Home Blog Page 3

Optimizing Fertilizer Nitrogen Release in Organic Production: The Role of Soil Conditions

By
Charlotte Decock | Associate Professor, Dept. of Natural Resources Management and Environmental Sciences, California Polytechnic State University, San Luis Obispo, Christopher Hight | Soil Laboratory Director, Betteravia Farms, Songyi Kim | Visiting scholar, California Polytechnic State University, San Luis Obsipo, Ashraf Tubeileh | Associate Professor, Dept. of Plant Sciences, California Polytechnic State University, San Luis Obispo and Matt Grieshop | Director, The Grimm Family Center for Organic Production and Research at Cal Poly
-
0

Crop yields are often lower in organic production systems compared to conventional farming systems (De Ponti et al. 2012). This yield difference is partly attributed to challenges in providing plants with the right nutrients, especially nitrogen (De Ponti et al. 2012; Gaskell and Smith 2007). Organic fertilizers must be broken down by soil organisms before N becomes available to plants in the form of ammonium (NH4+) and nitrate (NO3–), a process referred to as N mineralization (Figure 1). The speed and efficiency of this breakdown depend on the properties of the organic fertilizer (Cassity‐Duffey, Cabrera, Gaskin, et al. 2020; Geisseler et al. 2021). For instance, products with lower C:N ratios and liquid products are known to have a faster N release compared to products with higher C:N ratios and dry products, including pellets and composts (Lashermes et al. 2010; Lazicki et al. 2020). With this knowledge, fertilizer products can be chosen to best meet the crop’s N demand. Despite an increasing understanding of N mineralization rates of organic fertilizer, there is still large uncertainty around predicted release rates. One source of this uncertainty surrounds the impact of soil properties. Organic vegetable growers observe variations in nutrient program performance across fields, highlighting the need to understand how soil properties affect organic fertilizer breakdown rates. Research has shown differences in N mineralization from organic fertilizers between soils, but the reasons for these differences are not well understood (Lazicki et al. 2020; Marzi et al. 2020). Soil texture and pH are thought to impact organic fertilizer breakdown (Cassity‐Duffey, Cabrera, Franklin, et al. 2020; Thangarajan et al. 2015), but a thorough assessment of soil properties’ influence is lacking.

Figure 1. Overview of the nitrogen cycle. Green boxes and arrows represent nitrogen pools and processes within the soil-plant system. Gray boxes and arrows represent nitrogen loss pathways. Orange boxes and arrows represent nitrogen inputs.

Soil Laboratory Experiment
To address knowledge gaps on how soil properties affect N breakdown of organic fertilizers, we determined N mineralization rates of a commonly used 8-5-1 pelletized organic fertilizer in 72 soils with diverse properties (Figure 2). Composite soil samples were gathered from organic vegetable production fields in California’s Santa Maria Valley in fall 2020. This region, located at 34.9530 degrees N, 120.4357 degrees W, is a significant area for vegetable cultivation, boasting a variety of soil types and a Mediterranean coastal climate. Typically, these fields yield two to three crops annually. The valley features several soil series (Table 1), each with its own distinct soil properties.

Figure 2. Schematic overview of the experimental design.

We assessed 25 soil properties (Table 2), including soil texture, soil organic matter, soil organic carbon (SOC), soil organic nitrogen (SON), concentrations of ammonium (NH4+) and nitrate (NO3–) nitrogen, pH levels, electrical conductivity (EC), cation exchange capacity (CEC), exchangeable sodium percentage (ESP), concentrations of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfate (SO4-), mineralizable carbon (min-C), permanganate oxidizable carbon (POXC), carbon and nitrogen in particulate organic matter (POM) and mineral-associated organic matter (MAOM) fractions. All analyses were conducted using standard methods (Miller et al., 2013; Hurisso et al. 2016; Cotrufo et al. 2019). Mineralizable carbon (min-C), also referred to as soil respiration, is an indicator of microbial activity, while permanganate oxidizable carbon (POXC), also referred to as active carbon, can be considered a microbial food source. Both min-C and POXC are commonly used as indicators of soil health (Moebius-Clune et al. 2016; Norris et al. 2020). Meanwhile, POM and MAOM fractions can be interpreted as labile and more stabilized soil organic matter pools, respectively (Cotrufo et al. 2019; Lavallee et al. 2020).

Table 1. Dominant soil series in the Santa Maria Valley vegetable production region, based on the USDA Natural Resources Conservation Service soil survey.

All 72 soil samples were incubated for 28 days at 25 degrees C and 60% water holding capacity, both with and without the addition of organic fertilizer. The organic fertilizer used was a pelleted mix derived from meat and bone meal, poultry manure and feather meal (8-5-1), applied at a rate of 50 mg N per kg soil. This application rate corresponds to approximately 100 kg N per hectare (89 lbs. per acre), assuming a soil density of 2,000,000 kg per hectare in the top 15 cm of soil, consistent with rates reported by growers using split applications. Before application, the fertilizer was ground into a fine powder and thoroughly mixed. We measured NH4+ and NO3– concentrations on days 0, 7 and 28 of the incubation. The percentage of fertilizer N mineralized after 7 and 28 days was calculated as the difference in mineral N (NH4+-N + NO3–-N) over time between samples with and without fertilizer, divided by the amount of fertilizer N applied (Lazicki et al. 2020).

Table 2. Spearman correlation coefficients and p-values for correlations between the percentage of organic fertilizer nitrogen mineralized and various soil properties as predictor variables (n = 72). Significant spearman correlations (p < 0.05) are shown in bold.

Key Findings and Implications
We observed a wide variation in the percentage of N mineralized after 7 or 28 days of incubation (Figure 3). The mineralization rates ranged from -31% to 78% after 7 days and -22% to 87% after 28 days. Negative values indicate N was tied up in the soil after fertilizer application. On average, across all soils, 32% of the fertilizer N was mineralized after 7 days and 27% after 28 days. These results suggest soil characteristics can have a large impact on N mineralization from organic fertilizers.

Our findings are consistent with previous research. For example, a study comparing 22 commercial organic fertilizers found N mineralization ranged from 25% to 93%, with most N being mineralized within the first week. Similarly, in our study, the largest portion of fertilizer N was released within the first 7 days, with more subtle changes between days 7 and 28. Negative rates of N mineralization from organic amendments are found for inputs with high C:N ratios, but other studies typically find net mineralization for commercially available organic fertilizers. It’s important to note the application rate of organic fertilizer in our study was low compared to many other studies, so it is possible the balance between mineralization (release) and immobilization (tie-up) of N may depend on the application rate.

Figure 3. Histograms for the percentage of fertilizer nitrogen mineralized after 7 (blue) and 28 (yellow) days of incubation across 72 soil samples.

We found several significant correlations between soil properties and the percentage of fertilizer N released after seven days of incubation. For example, N mineralization after seven days was positively correlated with clay content, SOM, SOC, SON, CEC, pH, nitrate nitrogen, Olsen phosphorus, soil potassium, calcium, magnesium and microbial biomass nitrogen content. This suggests that fostering soil organic matter or soil carbon and general soil fertility may benefit the efficiency at which organic fertilizers are mineralized, especially during the first week following fertilizer application. In contrast to our expectation, the soil health indicators min-C and POXC and the organic matter fractions POM and MAOM performed poorly in predicting organic fertilizer mineralization in our study. Significant negative correlations were found with sand content, electrical conductivity and exchangeable sodium percentage. Negative effects of salinity and sodicity on organic fertilizer mineralization imply a compounding challenge for growing crops in saline or sodic soils under organic management.

Our study demonstrates organic fertilizer mineralization is influenced by soil properties. Maintaining pH, EC and ESP within the optimum range is important to ensure sufficient N mineralization from organic fertilizer. Fertilizer mineralization rates were greater at higher soil organic matter and soil nutrient concentrations, highlighting the importance of building these for efficient fertilizer use in organic crop production. Future research should focus on management practices that are most effective and cost-efficient for building soil organic matter and fertility to support reduced organic fertilizer input costs in the medium and long term. Our findings suggest in organic production systems, nutrient management should consider not only plant nutrient demand but also the nutrient demand for building and maintaining soil health and fertility.

The authors are grateful for support from Betteravia Farms for soil sample collection and analysis. Songyi Kim provided support through the Korea National Institute for International Education, Ministry of Education. Finally, this project could not have been completed without the technical support of Craig Stubler for laboratory analyses.

References

Al-Busaidi, K. T., Buerkert, A., & Joergensen, R. G. (2014). Carbon and nitrogen mineralization at different salinity levels in Omani low organic matter soils. Journal of Arid Environments, 100, 106-110.

Bowles, T. M., Hollander, A. D., Steenwerth, K., & Jackson, L. E. (2015). Tightly-coupled plant-soil nitrogen cycling: comparison of organic farms across an agricultural landscape. PloS one, 10(6), e0131888.

Cassity‐Duffey, K., Cabrera, M., Franklin, D., Gaskin, J., & Kissel, D. (2020). Effect of soil texture on nitrogen mineralization from organic fertilizers in four common southeastern soils. Soil Science Society of America Journal, 84(2), 534-542.

Cassity‐Duffey, K., Cabrera, M., Gaskin, J., Franklin, D., Kissel, D., & Saha, U. (2020). Nitrogen mineralization from organic materials and fertilizers: Predicting N release. Soil Science Society of America Journal, 84(2), 522-533.

Cotrufo, M. F., Ranalli, M. G., Haddix, M. L., Six, J., & Lugato, E. (2019). Soil carbon storage informed by particulate and mineral-associated organic matter. Nature Geoscience, 12(12), 989-994.

Daly, A. B., Jilling, A., Bowles, T. M., Buchkowski, R. W., Frey, S. D., Kallenbach, C. M., Keiluweit, M., Mooshammer, M., Schimel, J. P., & Grandy, A. S. (2021). A holistic framework integrating plant-microbe-mineral regulation of soil bioavailable nitrogen. Biogeochemistry, 154(2), 211-229.

De Ponti, T., Rijk, B., & Van Ittersum, M. K. (2012). The crop yield gap between organic and conventional agriculture. Agricultural systems, 108, 1-9.

Drinkwater, L. E., & Snapp, S. (2007). Nutrients in agroecosystems: rethinking the management paradigm. Advances in Agronomy, 92, 163-186.

Gaskell, M., & Smith, R. (2007). Nitrogen sources for organic vegetable crops. HortTechnology, 17(4), 431-441.

Geisseler, D., Smith, R., Cahn, M., & Muramoto, J. (2021). Nitrogen mineralization from organic fertilizers and composts: Literature survey and model fitting. Journal of Environmental Quality, 50(6), 1325-1338.

Hartz, T., & Johnstone, P. (2006). Nitrogen availability from high-nitrogen-containing organic fertilizers. HortTechnology, 16(1), 39-42.

Hurisso, T. T., Culman, S. W., Horwath, W. R., Wade, J., Cass, D., Beniston, J. W., Bowles, T. M., Grandy, A. S., Franzluebbers, A. J., Schipanski, M. E., Lucas, S. T., & Ugarte, C. M. (2016, Sep-Oct). Comparison of Permanganate-Oxidizable Carbon and Mineralizable Carbon for Assessment of Organic Matter Stabilization and Mineralization. Soil Science Society of America Journal, 80(5), 1352-1364. https://doi.org/10.2136/sssaj2016.04.0106

Lashermes, G., Nicolardot, B., Parnaudeau, V., Thuriès, L., Chaussod, R., Guillotin, M.-L., Lineres, M., Mary, B., Metzger, L., & Morvan, T. (2010). Typology of exogenous organic matters based on chemical and biochemical composition to predict potential nitrogen mineralization. Bioresource technology, 101(1), 157-164.

Lavallee, J. M., Soong, J. L., & Cotrufo, M. F. (2020). Conceptualizing soil organic matter into particulate and mineral‐associated forms to address global change in the 21st century. Global Change Biology, 26(1), 261-273.

Lazicki, P., Geisseler, D., & Lloyd, M. (2020). Nitrogen mineralization from organic amendments is variable but predictable. Journal of Environmental Quality, 49, 483-495.

Marzi, M., Shahbazi, K., Kharazi, N., & Rezaei, M. (2020). The influence of organic amendment source on carbon and nitrogen mineralization in different soils. Journal of Soil Science and Plant Nutrition, 20(1), 177-191.

Miller, R. O., Gavlak, R., & Horneck, D. (2013). Soil, Plant and Water Reference Methods for the Western Region (WREP-125, Issue.

Norris, C. E., Bean, G. M., Cappellazzi, S. B., Cope, M., Greub, K. L., Liptzin, D., Rieke, E. L., Tracy, P. W., Morgan, C. L., & Honeycutt, C. W. (2020). Introducing the North American project to evaluate soil health measurements. Agronomy Journal, 112(4), 3195-3215.

Pathak, H., & Rao, D. (1998). Carbon and nitrogen mineralization from added organic matter in saline and alkali soils. Soil Biology and Biochemistry, 30(6), 695-702.

Thangarajan, R., Bolan, N. S., Naidu, R., & Surapaneni, A. (2015). Effects of temperature and amendments on nitrogen mineralization in selected Australian soils. Environmental Science and Pollution Research, 22(12), 8843-8854.

Yousif, A., & Abdalla, M. (2009). Variations in nitrogen mineralization from different manures in semi-arid tropics of Sudan with reference to salt-affected soils. Int. J. Agric. Biol, 11, 515-520.

Silverleaf Nightshade: A Challenge in California Orchards

By
Jorge Angeles | UCCE Weed Management Advisor, Tulare, Kings and Fresno Counties and Elizabeth Fichtner | UCCE Farm Advisor, Tulare and Kings Counties
-
0
Figure 1. Silverleaf nightshade is widespread in California (a); blue dots indicate the distribution of the weed. Silverleaf nightshade affects young pistachio orchards in the southern San Joaquin Valley (b) (map courtesy CALFLORA 2024.)

Silverleaf nightshade, Solanum elaeagnifolium, is a perennial weed native to South America, Mexico and the southwestern and southern U.S. It is widespread in California where it affects diverse agricultural and non-agricultural systems, including orchards, rangeland, pasture, roadsides and disturbed areas. Because it readily adapts to high temperatures, low rainfall and saline and drought conditions, silverleaf nightshade is a problem in orchard systems. It is widely distributed in California and is currently affecting both young and mature orchards (Figures 1 and 2). Silverleaf nightshade is currently affecting young pistachio orchards in western Fresno and Kings Counties. In Tulare County, it is found in pistachio orchards that were planted in unmanaged fallow land or in fields near roadsides where it is commonly found. In mature orchards, missing trees create gaps in the canopy, thus allowing light penetration to the orchard floor and enabling establishment of resident populations of silverleaf nightshade (Figure 2a). In orchard systems, it competes with developing trees for resources, while the toxic glycoalkaloid compounds in the leaves and berries pose an additional threat to livestock and other animals if consumed.

Figure 2. Silverleaf nightshade colonizes open areas in orchards where missing trees allow sufficient light to reach the orchard floor, facilitating growth of the weed (a). In spring, distinct violet and yellow flowers (b) on the current season’s growth are a diagnostic feature, as well as the berries remaining on the prior year’s growth (c).

Identification
Silverleaf nightshade is an herbaceous, perennial weed belonging to the Solanaceae family along with other weeds, including black nightshade (Solanum nigrum), hairy nightshade (Solanum physalifolium) and horsenettle (Solanum carolinense). The mature plant is generally 1 to 3 ft high and can be readily identified by the small yellow to brown berries (~0.5 inch in diameter) and silver-gray foliage that often contains prickles (Figure 2c). The flowers are violet with distinct yellow centers (Figure 2b).

Life Cycle
Silverleaf nightshade is difficult to control because of its perennial life cycle in California. It emerges in early spring to late summer, with new plants growing from both seed and rhizomes. It flowers from summer to early fall, generating around 200 small fruits on each plant. Each fruit may contain 24 to 150 seeds. The seeds may be dispersed by birds that have consumed the fruit or by the movement of soil. The plant is also disseminated by movement of soil containing rhizome fragments. The mature plant dies back with the first frost, but the rhizomes survive underground.

Impacts
The weed competes with young orchard trees for resources, such as water, light and nutrients. If left unmanaged, silverleaf nightshade can also interfere with irrigation operations and potentially reduce vigor of young trees. Since silverleaf nightshade can adapt to alkaline and saline soils, it has the potential to outcompete many of the summer annual weeds and become the dominant weed in a population.

Management
Silverleaf nightshade is difficult to control in orchards. Tillage is not recommended because the movement of rhizome fragments may result in spread of the weed across orchards. Mowing can be an effective strategy to prevent weeds from setting seed. Flail mowers are often used in orchards and vineyards to mow weeds in between tree rows. After mowing, however, new silverleaf nightshade shoots may sprout from underground rhizomes, regenerating the weed. Despite the efficacy of mowing, most commercial mowers will miss weeds in the tree row. Hand weeding can be used to remove some of the weeds around the trees, but precautions need to be taken to protect the skin because mature plants are covered with reddish prickles. Weeding tools, such as shovels and hula hoes, are effective but can damage surface drip hoses if the user is not careful.   

Herbicides can be an effective weed management method to control silverleaf nightshade in different tree and vine crops. There are six post-emergent herbicides and one preemergent herbicide registered for use in trees and vines in California (Table 1). Preemergent herbicides are normally applied during the dormant season and most only control weeds before they germinate. Preemergent herbicides will not control silverleaf nightshade that emerges from rhizomes in the summer. Post-emergent herbicides can be used to control silverleaf nightshade that emerges in the summer and early fall before harvest. In the summer months, a combination of mowing and the use of post-emergent herbicides can kill the aboveground tissues of silverleaf nightshade and deplete the belowground propagules in soil. Post-emergent herbicides need adjuvants, such as nonionic surfactants and crop and seed oils, to increase their efficacy. 

Table 1. Herbicides registered for use in California tree and vine crops (https://wric.ucdavis.edu/).

Specific to pistachio, there are 12 preemergent and 13 post-emergent herbicides with different modes of action that are registered. Pendimethalin, rimsulfuron, mesotrione, flumioxazin, isoxaben and flazasulfuron are herbicides that have great control over black and hairy nightshade. Isoxaben can suppress silverleaf nightshade but can only be used in pistachios that have been established for at least three years. Glyphosate, glufosinate, pyraflufen-ethyl, paraquat and carfentrazone are post-emergent herbicides with different modes of action that can be used to control different weeds and can be used up to two weeks before harvest. 2, 4-D is another post-emergent herbicide that is registered for use in pistachios but needs to be applied to trees that have been established for at least one year and has a preharvest interval of 60 days. Studies have shown glyphosate and 2, 4-D have excellent control of silverleaf nightshade. Glyphosate is a systemic herbicide that can potentially kill the root and rhizome system of silverleaf nightshade when applied at the correct timing and rate. Furthermore, always consult herbicide labels on information regarding the required adjuvants, preharvest intervals, application rates and maximum applications per season.

Because silverleaf nightshade is a problem in mature olive orchards adjacent to the foothills in Tulare County, UCCE Weed Management Advisor Jorge Angeles (Tulare and Kings counties) recently initiated a study evaluating post-emergence herbicides, alone and in combination, for management of the weed. A suite of 10 treatments was applied in late Spring 2024, and preliminary data on treatment efficacy will be available by late July. Angeles is also interested in establishing a trial in late winter to evaluate efficacy of pre-emergence herbicides for management of silverleaf nightshade in table olives.

Silverleaf nightshade is difficult to control because of its adaptability to diverse agricultural systems, its tolerance to many herbicides and its perennial nature. A combination of cultural practices, such as mowing between tree rows, and implementation of an herbicide program with products containing multiple modes of action should be used to develop an effective management strategy for silverleaf nightshade. Additionally, developing and maintaining field records before planting is a great way to determine the history of a field, and weed surveys in the winter and spring can help determine what weed species are present in a field. Last, to prevent introduction of silverleaf nightshade into orchards, it is important to sanitize tractor equipment and manage the weeds that grow on the field edges or near irrigation canals.

Cover Crops, Groundwater and SGMA: A Complex Relationship

By
Hudson Minshew | CCA, State Conservation Agronomist, USDA-NRCS
-
0
Aerial photos with (left) and without (right) cover crops (photos courtesy Andrew Gal, UC Davis.)

Growers in the west are facing more and more pressure to account for their water use. On May 13, Sustainable Conservation (SusCon) released a report entitled Cover Cropping in the SGMA Era, summarizing two years of convenings held by SusCon with over 100 scientists, crop advisers and other agricultural professionals and stakeholders. The report distills research and working knowledge of the aspects of cover cropping impacts upon soil water budgets in the context of the Sustainable Groundwater Management Act (SGMA) and associated Groundwater Sustainability Agencies (GSAs).  Specifically, the report provides three areas of information derived from hours of convenings and interviews with GSA representatives:

1. A research summary of cover crop impacts to the water cycle, focused on California, Mediterranean and semi-arid climates

2. An investigation about impacts SGMA and GSA management may have on the use of cover crops

3. Recommendations for statewide water planners regarding the use of cover crops as a Climate-Smart Practice

Cover Crops Use and Management in California
Cover crops are a non-cash crop grown for multiple benefits. Cover cropping is generally recognized as an option for growers to fill a void and armor the soil between cropping seasons. The USDA Natural Resources Conservation Service (NRCS) incentivizes growers to grow cover crops across the nation, and the CDFA Healthy Soils Program incentivizes growers to grow cover crops in California. 

In addition to soil armoring, cover crops are recognized to provide a wide array of ecological services, that include improved water infiltration, water quality protection, erosion control, weed suppression, pollinator support and nutrient cycling to name a few. Cover cropping as a conservation practice is also one of USDA’s climate-smart agricultural practices because the practice also sequesters carbon, which improves soil health by feeding microbial populations and improves climate resiliency by the simple fact it holds soil together with its roots. In California’s Mediterranean climate, where most of the annual precipitation occurs between the months of November and March, cover crops are generally planted in the fall and rely on rainfall to grow. They are terminated in spring using various methods and at different times, depending on the crop, field conditions, operation schedules and grower’s objectives for using the cover crop in the first place. 

Prior to World War II, cover cropping was a common practice, especially the use of leguminous cover crops to provide nitrogen for crop production. In the 1950s and beyond, an increased prevalence of commercial fertilizers coincided with a decrease in use of cover crops. Over the past 30 to 40 years, cover cropping interest grew, paralleling society’s growing interest in agricultural sustainability, organic farming, the environment and soil health. 

Prior to the widespread interest in soil health in California, it was not unheard of for crop advisors to discourage cover cropping due to concerns for water competition with the cash crop. Following SGMA, a similar and more serious controversy evolved regarding the potential impact of cover crops upon groundwater supply.

Hydrological processes that may be influenced by cover crops. This illustration depicts the major flows of water occurring on a parcel that cover cropping has the potential to impact (source: Cover Cropping in the SGMA Era.)

   

Sustainable Groundwater Management Act and Cover Crop Water Use
Amid one of the most severe droughts in Californian history (2012-14), SGMA was instituted by the state to build a framework of GSAs to protect aquifers from overdraft using local jurisdiction. The drought accelerated groundwater use, causing groundwater in parts of the state to drop 50 to 100 feet below previous historical lows.

Several years ago, the agricultural community heard stories about growers avoiding cover cropping due to the fear of being penalized by their local GSA for allowing cover crops to grow on their farms. Further investigation by SusCon and other stakeholders showed cover crops may be unintentionally discouraged by GSAs because of the water budget accounting methods used that. at times, incentivized the maintenance of bare ground. Methods used for water accounting, such as satellite imagery, were based upon the assumption that cover crops have an evapotranspiration (ET) value that negatively impacts groundwater recharge. Research on cover crop water use increased in 2016, when a group of UC Davis researchers began to investigate the topic more closely to try to answer some unknowns about the potential of cover crops to impact the soil water balance and aquifer recharge.

It is an undeniable truth that winter cover crops use water for establishment and growth until termination in spring. How much water they use is what has shown difficult to answer precisely, and this value changes based on many factors, such as soil texture, climate, time of year, ground cover, the cover crop being grown and timing of cover crop termination. Recent studies as outlined in the report show winter cover cropping can use between 1 and 2 inches for establishment, which in some cases falls within a “margin of error” for annual irrigation rates for cropping systems (Smither-Kopperl pers. comm. 2024, DeVincentis 2023).

In some locations in California, growers do not plant cover crops because the climate and water supply will support multiple cash crops in a single year. With climate change, these options may become more limited, and growers and agronomists will have to seek out other opportunities for maintaining soil health between growing cycles. I recently heard about innovators exploring the use of “precision cover cropping,” whereby plantings are in narrow bands to either coincide with a cash crop’s rooting area or to address specific soil health and soil quality issues, like soil crusting and compaction.

Cover crop adoption rates in California and other states have hovered around 0% to 5% for years. In the SusCon report, cover crops include prescribed planting of cover crops (native and non-native) and volunteer groundcover (weeds). Many conservation entities encourage prescribed planting of cover crops to achieve and maximize multiple benefits and ecological services. Nevertheless, whether they’re intentionally planted or not, living ground cover in the fields during off seasons protects the soil.

Ironically, at times, the discussion of whether cover crops compete for water with the following crop seemed to be isolated from the discussion of the many ecological services they provide, namely increased water infiltration and decreased runoff, the two most pronounced hydrological services cover crops can provide. 

Table 1. Confidence in potential cover crop impacts to water budgets. Based on available, contextually relevant information, there is higher confidence that cover crops increase infiltration, decrease runoff and erosion and that water use is affected by termination timing. Factors such as the impacts on evapotranspiration (and the drivers of those impacts) are less understood (source: Cover Cropping in the SGMA Era.)

Summary of Findings
The SusCon report is an in-depth account of the current state of knowledge for soil water impacts of cover crops in Mediterranean climate regimes. Key findings outlined in the report were:

• Cover cropping improves the soil ecology and water cycling and provides other benefits.

• Impact of cover crops on water budgets is highly variable and depends on an assortment of factors, not limited to climate, soils and management.

• Cover cropping has shown to have a negligible impact on ET compared to bare ground in perennial and annual systems in Mediterranean climates.

• Wintertime, rain-fed cover cropping does not significantly increase water losses compared to bare ground in the winter months.

• California-based research literature showed the dominant water-balance benefits of cover cropping are increased water infiltration into the soil and the reduction of runoff, frequently ≥40% for both pathways.

From its research, Suscon developed five core recommendations to support SGMA implementation for sustainable water use in California:

1. Create a coordinated research approach to improve understanding of the impact of cover crops on net water balances.

2. Identify and address knowledge gaps that would allow GSAs to permit integration of cover cropping within their jurisdictions.

3. Support GSAs with up-to-date scientific information and guidance related to satellite ET, flow meter data and consumptive groundwater.

4. Improve data acquisition processes for key ET data and high-resolution data essential to GSA management, which would improve the quantity and quality of the data.

5. Provide funding to improve technical support for GSA that support research and guidance documents related to key ET data inputs.

This report gives me great confidence that water managers, growers, crop advisors, scientists and stakeholders can find ways to effectively use cover crops where it makes sense to do so. We can design the cover crop management strategies to accommodate multiple environmental benefits and match strategies to location and geography when we find cover crops appropriate to use. These designed benefits can and will include water conservation.

Resources

California Dept. of Water Resources, (February 2015) California’s Most Significant Droughts: Comparing Historical and Recent Conditions https://cawaterlibrary.net/wp-content/uploads/2017/05/CalSignficantDroughts_v10_int.pdf

DeVincentis, A., Solis, S. S., Rice, S., Zaccaria, D., Snyder, R., Maskey, M., Gomes, A., Gaudin, A., & Mitchell, J. (2022). Impacts of winter cover cropping on soil moisture and evapotranspiration in California’s specialty crop fields may be minimal during winter months. California Agriculture, 76(1), 37–45.

Ingels, C., Horn, M. V., Bugg, R., & Miller, P. R. (1994). Selecting the right cover crop gives multiple benefits. California Agriculture, 48(5), 43–48USDA ERS. (2023). State Fact Sheets: California [dataset]. https://data.ers.usda.gov/reports.aspx?StateFIPS=06&StateName=California&ID=17854

Kratt (February 2024) “Cover Crop Use in California and Measurable Outcomes” Progressive Crop Consultant

Lloyd, Margaret (May 2023) The Costs and Benefits of Growing a Cover Crop in an Annual Rotation in the Lower Sacramento Valley Progressive Crop Consultant

Mitchell et. al; (2023) Water Related Impacts of Cover Cropping. YouTube Video.  https://www.youtube.com/watch?v=mTNLx6LzEt0

Sustainable Conservation (May 2024) Report:  Cover Cropping in the SGMA Era.  https://suscon.org/blog/2024/05/ccrop-report-release/

USDA ERS, Wallender et al. (February 2021) Economic Information Bulletin Number 222 Cover Crop Trends, Programs, and Practices in the United States https://www.ers.usda.gov/webdocs/publications/100551/eib-222.pdf

Wyant, Karl (March 2023) “The Agronomy of Water” Progressive Crop Consultant

New Tools for Monitoring Vineyard Nitrogen

By
Alireza Pourreza | Associate Professor, UC Davis; Director, Digital Agriculture Lab; Founder, kobin.com
-
0
Dr. Alireza Pourreza collecting grape leaf hyperspectral reflectance using a backpack spectrometer equipped with a leaf clipper and looking at the measurement in real time (all photos courtesy A. Pourreza.)

Accurate nitrogen monitoring and appropriate nitrogen management are crucial in California due to the state’s unique environmental challenges and agricultural practices. N is essential for crop growth, but excessive use can lead to serious environmental issues, including groundwater contamination and the emission of nitrous oxide, a potent greenhouse gas. The Central Valley, a major agricultural area, has seen significant N inputs from both synthetic fertilizers and manure, leading to widespread nitrate pollution in groundwater, a critical issue since many communities rely on groundwater for drinking. To address these challenges, California has enacted regulations that require more precise N applications aligned with crop needs. This initiative aims to reduce the amount of excess N that can leach into groundwater or run off into surface waters. The regulations, such as those detailed by the Central Valley Regional Water Quality Control Board, include requirements for growers to submit Nitrogen Management Plans that report both the N applied and the N removed by harvested crops. This approach helps calculate N use efficiency and identify areas where improvements are necessary.

Overfertilization poses several risks to both plants and the environment. In plants, excess N can cause stress and overproduction of leaves, making them more susceptible to diseases. It can also reduce yield and decrease quality, including organoleptic quality, and reduce the content of mineral nutrients and secondary metabolites. Additionally, high nitrate content in leaves can be harmful. Environmentally, excess N that remains unused in the soil can leach below the root zone or be lost through run-off, leading to nitrate accumulation in natural water bodies. This can cause algal blooms, eutrophication and acidification of freshwater lakes and coastal areas. Nitrate-contaminated drinking water requires expensive treatments, and nitrous oxide emissions from denitrification and manure decomposition processes on agricultural sites contribute to global warming. These emissions also negatively impact terrestrial and aquatic ecosystems.

Conversely, N deficiency negatively affects photosynthetic assimilation and reduces crop yield both in terms of quantity and quality. It restricts the development and growth of roots, suppresses lateral root initiation, increases the carbon-to-nitrogen ratio within the plant, reduces photosynthesis and results in early leaf senescence. Therefore, monitoring N levels accurately and managing them precisely is essential for maintaining the health of both crops and the environment, particularly in California, where agricultural practices must align with stringent environmental regulations.

Leaf Spectrometry
Leaf spectrometry is a powerful technique used to measure the spectral reflectance of plant leaves across a wide range of wavelengths. This process involves collecting hyperspectral data, which refers to the reflected light from leaves. Each leaf has a unique spectral signature that changes based on its biochemical and biophysical properties, such as leaf pigments, protein and carbon-based contents, and moisture content. By analyzing these spectral signatures, researchers can infer various properties of the leaves, which provides valuable insights into the plant’s health and nutritional status.

Several tools are commonly used to measure leaf spectral reflectance. One of the primary instruments is a spectrophotometer, which can capture detailed reflectance data across different wavelengths. Portable leaf spectrometers, used in many studies, offer a more convenient and flexible option for field measurements. These tools are designed to be lightweight and easy to use, making it possible to collect high-quality spectral data directly from the plants in their natural environment. By utilizing these advanced tools, researchers and growers can obtain precise information about leaf properties, enabling more accurate monitoring and management of plant health and nutrient levels.

The process to create a mechanistic remote sensing model. In order from left to right, this involves spectral analytics at the leaf level, a nitrogen prediction model, scaling up the leaf-level knowledge to generate a canopy-level radiative transfer model that simulates the spectral characteristics of vine and retrieves plant traits, and a nitrogen status map that illustrates the spatial variability of plant nitrogen contents in a field.

Practical Application and Implementation
Imaging spectroscopy and leaf spectrometry have vast potential applications in agriculture, particularly for N management in vineyards. These technologies allow growers to monitor vine health and nutrient status accurately, providing essential data that can lead to more precise and efficient decision-making and farming practices. Detailed spectral data reveals changes in leaf biochemical and biophysical properties, some of which are indicative of the vine’s N content.

Spectral modeling approaches for N retrieval have evolved significantly. Traditional methods often relied on simple correlations between basic vegetation indices or specific wavelengths and N levels. While these methods were quick, they could be overly simplistic. Modern approaches utilize advanced techniques, such as chemometrics and machine learning algorithms, to analyze spectral data. Chemometrics involves using statistical methods to extract meaningful information from complex spectral data, providing more accurate and comprehensive insights into N levels. Machine learning algorithms have become increasingly popular. These models can process large datasets and learn intricate patterns, offering high accuracy and robustness in N estimation.

Alternatively, physically based models, or radiative transfer models (RTMs), simulate the mechanism of light interaction with plant tissues to estimate biochemical/biophysical properties. These models are highly accurate and consistent and can be applied across various conditions, though they require detailed input data and calibration. Combining RTM with machine learning techniques, creating hybrid models, can further enhance their accuracy and applicability. Hybrid models use detailed simulations from RTMs to train machine learning algorithms, resulting in systems that can adapt to different environmental conditions and crop types. Implementing these advanced spectral sensing techniques in vineyards involves several practical steps. First, growers need to collect hyperspectral data from their crops using either portable ground-based spectrometers or aerial spectral cameras. This data is then analyzed using one of the above modeling approaches, whether it’s chemometrics, machine learning or a hybrid method. Depending on the modeling approach, the results can potentially provide detailed insights into the N status of the vines, allowing for precise and targeted fertilizer applications.

Case Study
We conducted a study to compare various analytical methods for N retrieval in grapevine leaves using hyperspectral data. Our primary goal was to determine the most effective approach for accurately and consistently estimating leaf N levels, considering both purely data-driven empirical methods and more sophisticated mechanistic models like PROSPECT and hybrid modeling techniques.

N in plants is primarily found in proteins, which are critical for various physiological processes. Proteins in the leaves contribute significantly to the N content, making the measurement of protein levels a consistent indicator of N status. Traditional methods often rely on the relationship between chlorophyll content and N, but this approach can be misleading due to the small proportion of N in chlorophyll and the dynamic nature of N allocation within the plant.

Empirical methods, such as those using simple vegetation indices like the Normalized Difference Vegetation Index (NDVI) and the Normalized Difference Red Edge (NDRE), have been widely used for estimating N content. However, these indices often fall short of providing accurate and consistent results for vine N content. NDVI and NDRE are sensitive to changes in chlorophyll content but do not capture the full complexity of N dynamics within the plant. Their reliance on a few spectral bands can lead to inaccuracies, particularly under varying environmental conditions and growth stages.

The PROSPECT model simulates how light interacts with leaf tissues, providing a more detailed and physically based approach to estimating N content. By incorporating specific absorption coefficients for proteins, PROSPECT can more accurately represent the biochemical processes within the leaves. This model showed robustness and transferability across different conditions but requires full band (400 to 2500 nm) and well-calibrated spectral data.

Hybrid modeling combines the strengths of both artificial intelligence and physically based approaches. By using detailed simulations from PROSPECT to train machine learning algorithms, hybrid models can achieve higher accuracy and adaptability. These models leverage the comprehensive understanding of light interactions provided by PROSPECT and the flexibility and learning capacity of machine learning techniques.

The advantages and disadvantages of four different spectral modeling approaches:

• Vegetation Indices (NDVI, NDRE, etc.): quick and easy to use but often inaccurate and inconsistent for detailed N estimation.

• Empirical Data-Driven Methods (Machine Learning): high accuracy with large datasets but can be prone to overfitting and may require extensive training data.

• Physically Based Models (PROSPECT): highly accurate and robust but complex and data-intensive.

• Hybrid Models: combines the best of both worlds, offering high accuracy and adaptability with a solid physical basis.

Our study demonstrated while traditional vegetation indices are useful for general assessments, they are insufficient for precise N management in vineyards. Advanced methods like RTM and hybrid models provide a more reliable and detailed understanding of N dynamics, paving the way for more effective and sustainable vineyard management practices. By leveraging these advanced analytical techniques, vineyard managers can optimize N use, improve crop health and reduce environmental impacts. If adopted by growers, this data-driven, decision-making vineyard management approach will support compliance with stringent environmental regulations, promote sustainability, drive the future of precision agriculture and optimize crop production.

Resources

The peer-reviewed paper: sciencedirect.com/science/article/pii/S0034425723005187#f0005

RTM interactive tool: digitalag.sf.ucdavis.edu/decision-support-tools/RTM

When2fly app: digitalag.sf.ucdavis.edu/decision-support-tools/when2fly

Overcoming Objections in the Field: A Sales Pro’s Guide to Engaging California Growers

By
Jason Scott, MS | Publisher/CEO, Progressive Crop Consultant, JCS Marketing Inc.
-
0

In the world of agricultural sales, particularly within the rich and varied landscapes of California, understanding and overcoming objections is paramount. As experienced sales professionals and crop consultants, your role transcends mere transactional exchanges; it’s about building trust, understanding needs and offering solutions that genuinely benefit our farming partners. Here, I’ll share my insights on navigating these waters effectively.

1. Listen Intently: Before you can overcome an objection, you need to fully understand it. Listen to the grower’s concerns without interrupting. This not only shows respect but also gives you the necessary information to address their specific issues.

2. Empathize and Validate: Growers want to know you understand their situation. Acknowledge their concerns and empathize with their challenges. A simple “I understand why that could be a concern” goes a long way.

3. Educate and Inform: Use your expertise to educate the grower about the benefits and features of the product. Present data, case studies and testimonials that align with their concerns. Remember, knowledge is power, but it must be relevant to their specific circumstances.

4. Tailor Solutions: Customize your solutions to address the grower’s unique needs and conditions. Show how your product or recommendation directly resolves their issues or improves their operations.

5. Highlight ROI: Growers are business owners who care about the bottom line. Discuss the return on investment and how the product can increase efficiency, yield or quality in the long term.

6. Address Risks Directly: Don’t shy away from discussing potential risks. Be honest about them and discuss how these risks can be managed or mitigated. This honesty builds trust and credibility.

7. Utilize Third-Party Validation: Bring in success stories, testimonials or endorsements from other growers and industry experts. Peer approval can be a powerful motivator.

8. Create a Sense of Urgency: Without being pushy, explain any time-sensitive benefits of acting now, such as limited availability, current pricing or seasonal advantages.

9. Offer Trial or Pilot Programs: If possible, offer a trial period or a pilot program. This lowers the barrier to entry by reducing perceived risk.

10. Be Patient but Persistent: Change can be daunting. Allow the grower time to think but follow up regularly. Persistence shows commitment and can often be the key to eventual agreement.

In my years of experience, these strategies have been instrumental in navigating objections and building fruitful relationships with California growers and other agricultural businesses. It’s about more than just selling a product; it’s about fostering partnerships and contributing to the success of their agricultural endeavors.

Remember, every objection is an opportunity in disguise, an opportunity to educate, to build rapport and to find mutual ground. With the right approach, patience and understanding, objections can be transformed into gateways for growth and collaboration. As sales professionals and crop consultants, your goal should always be to serve as trusted advisors, guiding farming partners toward decisions that enrich their lands and their livelihoods.

Helping California Growers Maximize Profits in 2024

By
Jacquelyn Fernandes | Territory Manager, Nutrien Financial
-
0
Jaquelyn Fernandes is a territory manager with Nutrien Financial and recommends now as a good time to evaluate a financial plan and make sure growers are taking steps to positively impact profitability (photo courtesy Nutrien Financial.)

Putting a farming operation along a profitable path may seem like a simple proposition (spend less to produce the crop than the price it can sell for), but when you look closer, the task is much more nuanced. Solving this equation requires a proactive plan and flexibility for growers to respond to many different scenarios.

Many variables can negatively impact the profitability equation: labor costs, water access/availability, changes in pest management strategy, etc. The chances of enhancing profitability increase when growers put themselves in a stable financial position where they can withstand threats and adapt to variable economic and environmental conditions.

To get there, California growers need to consider several factors that will impact farm finances this year.

Where to Look for Cost Savings
The cost of doing business continues to creep up, but there are savings to be had if you look in the right places.

To start, it’s important to review interest expenses and evaluate different lending options that can impact the cost of borrowing. There will always be a cost to borrowing money, but growers might be overpaying if they don’t research options, particularly in the current rate environment where costs can add up.

Over the last few years, growers have seen a much higher percentage of their profits eaten up by interest expenses due to rising interest rates, which climbed higher than many have seen in a generation. As of March, the Federal Reserve is holding rates steady, but they are still at a 20-year high, so interest rates remain critical.

Growers can’t control rates, but they can take advantage of promotional offers alongside traditional fixed rate financing to bring the total effective interest rate down to a level that, when consolidated, lands below Prime.

Take a hypothetical example where a grower finances an equal amount for three different input purchases over the same financing period. In addition to their own in-house financing offer, a retailer may have access to a variety of promotional rate offers on some brands. For example, a financing package might look like:

  • Product A at 9% APR
  • Product B at 2% APR
  • Product C at 4% APR

If this grower paid for these products with their operating line of credit, they would be looking at a financing rate ranging between 7% to 11% APR. If this same grower used the blended approach and took advantage of the option to finance the purchase of all three products, they would bring their effective interest rate down to 5% APR, which adds up to meaningful savings on interest expense.

Be Proactive When It Comes to Managing Cash Flow
Beyond interest rates, California growers can also impact profitability by looking closely at their cash flow needs and evaluating the terms of any financing programs they participate in to ensure that payment due dates line up with crop schedules.

One of the biggest benefits that comes with strategic use of financing is cash preservation. It’s not enough to have the right mix of crop nutrition and protection products; growers must go a step further and think about how and when they’re paying for those products, whether that strategy affords the amount of financial flexibility they need. For example, growers may experience unexpected costs if they need to adjust their pest management strategy mid-season.

Let’s say a crop is infested by navel orangeworm in July, but a grower won’t have cash on-hand until harvest proceeds are recorded in December. In this scenario, it’s helpful to use other financing programs that can complement a grower’s operating line of credit. This affords more options in terms of how and when to spend capital, depending on changing needs.

Creating a Layer of Protection Against Market Volatility, Other Uncertainties
Growers know they are going to face challenges every season, and they need to be ready to respond to impacts from the market, Mother Nature and other factors that play into the success of their crop. We can’t control every threat as no one has a crystal ball to show where the market will go. It’s hard to predict how consumer preferences are going to shift and how that will impact crop selection and planting decisions. However, there are a few proven strategies that can give California growers some peace of mind when it comes to protecting themselves, and their money, against external forces.

It starts with capital management strategy, and being surrounded with people who can provide partnership and expertise to help succeed. Second, it may seem elementary, but diversification is also critical to manage risk. That may come in the form of crops, but it also comes back to finances and having a diverse stream of capital to pull from as to not overextend or put too much leverage on one source of capital.

Having a sound financial plan is also helpful when it comes to contingency plans and avoiding situations where a grower might take a financial hit when something unexpected happens. Strategic financing of crop inputs enables growers to keep cash on-hand for those unexpected expenses. Growers who are paying for operational expenses with a bank operating note have fewer options in terms of a backup plan if they run into unforeseen circumstances.

As we see how things start coming up after planting season, now is a good time to evaluate a financial plan and make sure growers are taking steps to positively impact profitability. With informed financial planning and sound money management, 2024 can be a grower’s best year yet.

ACP and HLB: Not Just Acronyms Understanding What California’s Citrus Crop Could Face

By
JW Lemons | CCA, CPAg, Verdesian Life Sciences
-
0
Figure 2. Asian citrus psyllid nymphs. The spread of huanglongbing by psyllids increases the mortality rate of citrus trees, reduces marketable yield per tree and increases production costs through greening.

Acronyms mean a lot when it comes to protecting our citrus industry.

Many Californians are affected by the many acronyms being passed around as plans to protect a valuable agriculture crop in our state are formed. CDFA is leading the charge, with the Citrus Pest and Disease Prevention Division developing a statewide Action Plan for Asian citrus psyllid (ACP) and huanglongbing (HLB) disease.

Action taken to control the spread includes an HLB citrus quarantine in place throughout portions of Los Angeles, Orange, Riverside, San Bernardino, San Diego and Ventura counties in response to HLB detections in those areas. These steps are sometimes perceived negatively by growers. They are, however, necessary. It is a way to try to ensure the fruit goes through a collection and observation period to detect the vector. ACP carry the disease, and when they feed on a healthy tree, they spread the infection.

Figure 1. Asian citrus psyllid adult. Psyllids vector huanglongbing, and when they feed on a healthy tree, they spread the infection (all photos courtesy Citrus Research Board.)

Quarantines can come with a huge price tag. Increased sorting and detection methods in place increases the cost of doing business as normal. Delay from picking to warehouse could have some adverse effects on the quality of the crop as it pertains to storage and packing. Because we isolate the picked fruit on site it delays cooling and other treatments in the packing sheds. This could allow other diseases to gain a foothold and cause additional losses. With a crop valued at $2.6 billion (in California) for the 2022-23 season, we can easily see its economic importance. During this season, California accounted for 92% of fresh market production in the U.S.

To put losses from HLB into perspective, we can look at the Florida market. HLB was first detected in 2005. One study (Hodges and Spreen 2012) estimates HLB reduced the value of Florida citrus output by $4.51 billion between the 2006-07 and 2010-11 crop production years. Many factors of abiotic and biotic stresses play a part in citrus losses. HLB economically affects commercial citrus groves in three ways. First, the disease increases the mortality rate of citrus trees. Second, the disease reduces the marketable yield per tree. Third, greening increases production costs. Yield and quality are inhibited in an infected grove to the point of 100% loss at times. Removal of entire blocks reduces growers’ ability to get positive returns.

Other studies conducted have different loss numbers, but we can see this destructive disease can bring with it additional large economic losses. The three losses previously listed are directly related to trees, fruit and production. Much of this has been a permanent loss to production. What we cannot ignore are the other financial impacts of the disease. Costs of fertilizer and insect control must increase to even try and maintain productivity. We strive to control the insect with numerous sprays and even trunk injections. We supplement the trees’ nutrition to offset the reduced nutrient and water flow capability of an infected tree. In addition to controlling the psyllid, growers can mitigate some of the symptoms of the disease via foliar applications of essential micro- and macronutrients, often supplemented with resistance-enhancing products (Shen et al. 2013a; and Spann et al. 2010a). These applications increase costs by $200 to $600 per acre, depending on the nutrient mix applied (Roka and Muraro 2010).

Figure 2. Asian citrus psyllid nymphs. The spread of huanglongbing by psyllids increases the mortality rate of citrus trees, reduces marketable yield per tree and increases production costs through greening.

Less trees and fruit drives consumer prices up and could push buyers away from the citrus market. In one estimate, higher prices for the fruit that is left could still result in a loss to producers in the millions of dollars. The reasoning is even higher fruit and juice prices would not make up for the difference. Because the decrease in sales would far outweigh the increase in price received. Job losses in the fresh sector and the juice sector in Florida were reported in the tens of thousands. Lost income in the job sector and lost sales taxes for the state can add up quickly. An economy that depends greatly on this crop and job sector suffers heavily.

Reading additional reports, we might assume job loss would be proportional to the drop in production. One report expected HLB in orange groves would result in the loss of approximately 5,000 jobs per year in Florida’s processing sector. Job loss estimates are consistent with the estimates in Hodges and Spreen (2012), who estimate citrus greening has cost Florida an average of 8,257 jobs per year.

The disease is here in California. Because this disease has struck around the world, researchers and concerned citrus industry participants from numerous countries recently attended the seventh International Research Conference on Huanglongbing (IRCHLB) in March in Riverside, Calif. The sixth IRCHLB was held in Riverside in 2019 with more than 400 attendees from around the world. The global citrus industry continues to fight the battle with new treatments, genetic changes to trees, biostimulants and nutrition.

The theme of this year’s conference was, “Transitioning research to field reality,” and featured keynote speakers who provided research and technical updates regarding the global status of HLB as well as technical and poster sessions presented by many of the leading researchers from around the world. The conference allowed these scientists time to foster collaborations to advance their research and discuss notable and emerging ideas.
In California, we need people to understand and not be confused by acronyms. We cannot begrudge the millions of research dollars that will go toward finding solutions. Other funds will go toward action plans to control the spread of this devastating disease and potential loss to a very important part of our state.

Resources
Spreen, Thomas & Baldwin, Jean-Paul & Futch, Stephen. (2014). An Economic Assessment of the Impact of Huanglongbing on Citrus Tree Plantings in Florida. HortScience. 49. 1052-1055. 10.21273/HORTSCI.49.8.1052.
Ariel Singerman, Michael E Rogers, The Economic Challenges of Dealing with Citrus Greening: The Case of Florida, Journal of Integrated Pest Management, Volume 11, Issue 1, 2020, 3, https://doi.org/10.1093/jipm/pmz037
Singerman, A., & Useche, P. (2016). Impact of Citrus Greening on Citrus Operations in Florida. EDIS, FE983.
Vaz da Costa, G., Neves, C. S. V. J., Bassanezi, R. B., Leite Junior, R. P., & Telles, T. S. (2021). Economic impact of Huanglongbing on orange production. Revista Brasileira de Fruticultura, 43(3), 4.
Lopez, J. A., & Durborow, S. L. (2015). Huanglongbing and the California Citrus Industry: A Cost Comparison of Do Nothing vs. Do Something Management Practices. Texas Journal of Agriculture and Natural Resources, 27, 51–68.

Soil Microbiome Post-Fumigation: Building Soil Microbe Populations Back Stronger

By
Cassidy Million | Ph.D., Director of Ag Science, Heliae Agriculture
-
0
Figure 2. The soil on the left shows limited microbial growth post-fumigation. The soil on the right shows increased microbial abundance (number) and diversity (different types) when a microbial food source is applied post-fumigation.

Fumigation provides a myriad of economic benefits for growers, including pest control, improved food safety and increased yields. High-value crop producers rely on fumigation to aid in the control of soilborne pests, including nematodes, fungi, bacteria and even weeds.
However, fumigants remain controversial due to potential environmental and off-target issues as well as risks to human and animal health. While both the economic and environmental benefits and risks are important to consider when fumigating, what is happening belowground? How is fumigation impacting our soil microbiome, and what are the risks and benefits to consider when considering soil health?

What Happens to Soil Microbes After Soil Fumigation?
Depending on a fumigant’s active ingredient, bacteria, fungi, nematodes and/or weeds are reduced to control pathogen load to produce a healthy crop in the following planting. Once fumigation occurs, a reduction in the target pest should be observed. However, can fumigation impact off-target organisms, or those microbes that fumigant was not intended for?

Fumigants with broad-spectrum activity can affect both target (pathogenic) and non-target (beneficial) microorganisms. This can have an impact on nutrient cycling and plant nutrient uptake, which can negatively impact soil health. The ability for beneficial, non-target organisms to recover is critical as they play an important role in the promotion of soil health. Recent studies have shown within the first four weeks post-fumigation, there is a decrease in the abundance (number) and diversity (different types) of bacteria in fumigated soils compared to untreated soils.

Figure 1. The goal of soil fumigation is increased economic benefits for growers. There are some watchouts that can be combated through soil amendments and practices.

Research shows these affected microbial populations can recover in a relatively short period of time, less than a year after the application of fumigants. But what if you are regularly fumigating your fields year after year? Results have shown that the microbial communities can shift due to fumigation, meaning you may see changes in the functional diversity of these communities or what functions these microbes provide in the soil. The fumigation treatments that cause these community shifts can also contribute to physical, chemical and biological changes in the soil, ultimately degrading soil health. Long-term studies (15+ years) of repeatedly fumigated fields show non-target organisms such as arbuscular mycorrhizal fungi (AMF, which play a role in nutrient and water uptake), gram – and + bacteria, actinomycetes and fungi biomass declined compared to non-fumigated soils.
The impact on the microbial community and recovery is also dependent on the type of fumigant used, with methyl bromide having the most detrimental effects and 1,3-dicloropropene having the least. This research suggests there may be a negative impact on soil health with repeated long-term fumigation practices.

How to Rebuild Soil Microbes Following Fumigation
Avoiding fumigation all together is likely not an option for all growers. To aid in building back your microbial populations post-fumigation, utilization of soil amendments and practices can be adopted, including management practices that introduces food sources to increase microbial abundance and diversity to improve your soil and soil health (Table 1). There are many options when it comes to building soil biology and soil health. Some of these practices may have better outcomes based on your current operation.

Table 1. Practices that can help improve soil biology and improve soil structure.

They’re Hungry! Feed Your Soil Biology
It may seem obvious that a good management choice would be to feed the post-fumigated biology in the soil, but this practice is often missed or overlooked.

After fumigation, the soil still contains fungi and bacteria, and we know that within four weeks to one year, post-fumigation populations begin to recover, and they are ready to go to work for you. The problem? They are starving and will go dormant until conditions improve. Research shows farm soils are generally low in the food sources that microbes like to eat, and this food scarcity will limit the activity of your soil biology. The answer? Give them a well-balanced meal to keep their populations up. You have many choices, including microalgae and molasses, etc. Figure 2 is an example of utilizing a microalgae food source to feed the microbes after a fumigation event has occurred. Here you can see a significant increase in microbial populations with a 6.4x increase compared to the fumigated soil alone.

Figure 2. The soil on the left shows limited microbial growth post-fumigation. The soil on the right shows increased microbial abundance
(number) and diversity (different types) when a microbial food source is applied post-fumigation.

Add Soil Biology
Another option is to add biology to the soil. There are many options when it comes to choosing the type (genus and species), but the main concept is to provide selected species of bacteria or fungi to the soil that will benefit your crop and put them to work for you. Live inoculants must stay alive to get the benefit you are looking for, which can be challenging when these sensitive microbes are exposed to changes in temperature and humidity from shipping, storage and field application. If you choose this option, plan carefully about how you are getting these products to the field, including best practices for tank mixing. Make sure your product is viable and high quality before adding to your fields.

Mulches and Compost
This practice is like the first management suggestion but provides a “slow release” food source for the microbes. Not all the carbon in plant mulch and compost is available as microbial food. Instead, it must be chemically and physically broken down before the microbes can take advantage of it. Mulches and compost provide a nutrient source to the soil. Watch out for organic matter that isn’t prepared carefully, as it can contain excess salt and weed seeds.

Reduce Tillage and Improve Your Soil Biology
Field management practices like tillage can be hard on your soil biology, particularly the soil fungi.

For example, when a disk moves through the field, it not only slices through the soil (what you want to happen) but it also slices and dices through all the fungi threads (hyphae) you are trying to grow (what you do not want to happen!). This unintentional result can have a severe impact on the biological contribution to soil structure.

Moreover, excessive tillage can compact your soil structure over time, resulting in potential water management issues. Reducing tillage can improve your soil structure on two fronts by preserving the biology and reducing the crushing and compaction of your soil structure. It’s commonly known that implementing reduced tillage may be difficult in certain operations or in more distributive soil cropping systems, so consider combining multiple practices mentioned for a beneficial alternative.

Cover Crops and Soil Biology
The use of cover crops improves soil quality and structure, builds organic matter and recycles nutrients. Cover crops can be grown in between the rows of permanent crops (e.g., trees and vines) or in the ‘off-season’ for annual crops and can be used to help feed soil microbes. Cover crop roots secrete carbon substances, called exudates, which can help boost the soil fungi and bacteria when a crop is not in the ground. Plus, their fine root hairs can tie soil particles together. Keeping soil alive year-round is key to optimizing biological contribution to soil quality.

Fumigation is a tool to help increase economic benefit for the growers including the control of soilborne pests, improve food safety and increase yield. Fumigation can negatively impact the soil microbiome, and long-term use of fumigation can reduce soil health. However, there are many options to offset any damage done to soil health by utilizing soil amendments and practices to counter the risks of declining soil health. When utilizing agricultural practices, it is best to know the long-term and short-term risks and benefits of a practice and understand how to reduce those risks with management solutions.

References
Castellano-Hinojosa, A., Boyd, N.S., Strauss, S.L. (2022). Impact of fumigants on non-target soil microorganisms: a review. Journal of Hazardous Materials, Volume 427.
Ibekwe A.M., Papiernik S.K., Gan J, Yates S.R., Yang C.H., Crowley D.E. (2001). Impact of fumigants on soil microbial communities. Appl Environ Microbiol.
Li, X., Skillman, V., Dung, J. et al. (2022). Legacy effects of fumigation on soil bacterial and fungal communities and their response to metam sodium application. Environmental Microbiome, 17, 59.
Dangi, S.R., Tirado-Corbalá, R., Gerik, J., Hanson, B.D. (2017). Effect of Long-Term Continuous Fumigation on Soil Microbial Communities. Agronomy, 7, 37.

Crop Consultant Conference is the Premiere Event for PCAs, CCAs

By
PCC
-
0
Crop Consultant Conference is the Premiere Event for PCAs, CCAs

The 2024 Crop Consultant Conference is set to return this September and promises to be the agricultural event of the year. Taking place in the heart of California’s Central Valley in Visalia, the conference is an essential gathering for PCAs and CCAs. Hosted by JCS Marketing’s Progressive Crop Consultant magazine and MyAgLife, and Western Region Certified Crop Advisers, a leader in PCA and CCA education, the event offers a unique blend of continuing education (CE), networking and industry insights you won’t find anywhere else.

Renowned for its agricultural productivity, the Central Valley is an ideal setting for this conference, which will immerse attendees in an environment that reflects the latest advancements and enduring traditions of California agriculture.

“This strategic location in Visalia allows participants to connect directly with the innovations and practices that are shaping the future of crop consulting,” said JCS Marketing CEO Jason Scott.

Scott said the event’s focus on innovative pest control strategies, sustainable farming practices and cutting-edge technology ensures attendees will leave with practical knowledge that can be immediately applied.

Comprehensive CE Opportunities at an Affordable Price
Scott said he recognizes the vital role of continuing education for ag professionals and strives to offer a range of CE opportunities at the conference each year. MyAgLife ensures attendees can earn their credits through early online courses, live event sessions and post-conference offerings.

“This flexibility allows professionals to manage their schedules while keeping up to date with essential knowledge and skills,” Scott said.

With a registration fee of just $350, the conference is an exceptional value.
“This cost-effective pricing translates to mere pennies per CE credit, making it an unbeatable investment for PCAs and CCAs,” Scott said, adding the affordable fee ensures every participant can access high-quality education and networking without breaking the bank.

An Event Packed with Opportunities
The Crop Consultant Conference is more than just a series of lectures; it’s a full-fledged experience designed to benefit all attendees to connect them with industry leaders, decision-makers and peers through structured networking events and informal gatherings.
“It’s a unique chance to build relationships that can lead to new opportunities and collaborations,” Scott said.

Attendees can expect to sit in on innovative seminars and workshops to learn the latest research, cutting-edge technologies, and best practices that are driving the industry forward. They will also have access to the latest products, services and technologies in the agricultural sector during the conference’s trade show, allowing them to engage with exhibitors who are at the forefront of innovation and see firsthand the tools that can enhance your practice.

Scott said the trade show is also a great opportunity for companies who are looking to increase their visibility and establish industry leadership by taking advantage of exclusive sponsorship opportunities.

“Our sponsorship packages offer prominent exposure to a highly targeted audience of ag professionals,” he said.

High Demand and Limited Availability
With its comprehensive educational program, affordable pricing and unparalleled networking opportunities, the Crop Consultant Conference is expected to sell out quickly. Both registrations and sponsorship opportunities are in high demand, so it’s crucial to secure your spot early.

“This is an unparalleled opportunity to join your peers and industry leaders in the Central Valley for an event that promises to be both educational and transformative,” Scott said.
He said the Crop Consultant Conference represents a pivotal moment for ag professionals. By bringing together PCAs, CCAs, researchers and industry experts, the conference fosters a collaborative environment where attendees can enhance their knowledge, skills and professional networks.

“MyAgLife’s commitment to providing flexible and accessible CE opportunities makes this event an invaluable resource for those dedicated to excellence in crop consulting,” Scott said.

Act Now: Secure Your Spot
Given the high level of interest and limited availability, it’s imperative to act quickly. Avoid the disappointment of missing out on this invaluable event by registering today. The fear of missing out (FOMO) is real, and this is your chance to be part of a transformative experience that will drive your professional growth and industry knowledge.
Visit progressivecrop.com/conference to register and secure your place at the 2024 Crop Consultant Conference.

Satellite-Based Irrigation Tools for More Precise Water Management in Avocado Orchards

By
Ali Montazar | UCCE Irrigation and Water Management Advisor, San Diego, Riverside and Imperial Counties
-
0
Figure 1. A screenshot of the FRET ETo map for the entire U.S. issued on April 26, 2024.

The water requirement of a crop must be satisfied to achieve optimum potential yield. The crop water requirement is called crop evapotranspiration and is usually represented as ETc. By combining reference evapotranspiration (ETo) and the proper crop coefficient (Kc), crop water needs (ETc) can be determined as ETc = ETo × Kc. ETo is an estimation of evapotranspiration for short grass canopy under a well-managed, non-stressed condition. ETo is the main driver to estimate or forecast crop water needs. There are user-friendly, satellite-based irrigation tools available that may assist avocado growers with scheduling irrigation more effectively. These tools provide ETo forecast for up to six days in the future and/or actual ET at the scale of individual fields. This article introduces three free satellite-based irrigation tools including FRET, IrriSAT and OpenET. A comparison of estimated daily ET by OpenET tool and actual ET measured using Eddy Covariance equipment is also presented for an avocado orchard in San Diego County.

FRET (Forecast Reference Evapotranspiration)
A new alternative to weather station ET is forecast reference ET or FRET (Figure 1). The National Weather Service offers FRET data on the Graphical Forecasts page of their website. FRET is one option in the digital forecast database display, and you can zoom in to find ETo data for your field up to six days in the future. In other words, FRET will assist growers to have forecast ETo up to the next six days and more effectively schedule irrigation. FRET is currently available at https://digital.weather.gov/. This tool is particularly useful to forecast crop water needs and schedule running hours of an irrigation system ahead of heat waves in avocado orchards.

Figure 1. A screenshot of the FRET ETo map for the entire U.S. issued on April 26, 2024.

IrriSAT Irrigation Decision Support System
IrriSAT is a weather-based irrigation management and benchmarking technology that uses remote sensing to provide site-specific crop water management information across large spatial scales (Figure 2). It uses satellite imagery to estimate crop coefficients (Kc) at a 30-meter resolution. IrriSAT calculates Kc from a linear relationship with satellite derived Normalized Difference Vegetation Index (NDVI). Daily crop water use is determined by simply multiplying Kc and ETo observations from a nearby weather station. A beta version of the app is currently available at https://irrisat-cloud.appspot.com/, developed using Google App Engine.

Figure 2. A screenshot of crop coefficients calculated by the IrriSAT Google App. By combining reference evapotranspiration and the Landsat-derived crop coefficient, crop water use can be determined on a 30m x 30m basis such that ETc = ETo × Kc.

OpenET
OpenET is a new online platform that uses satellites for mapping evapotranspiration (actual ET) at the scale of individual fields and currently can be used in 17 western states (Figure 3). OpenET is produced at a spatial resolution of 30m x 30m (0.22 acres). Daily, monthly and cumulative ET data are accessible on the OpenET Data Explorer. OpenET is currently available at https://openetdata.org/.

Figure 3. A screenshot of of cumulative ET (inch) for the entire western states. You may zoom on the OpenET map to find your orchard for a specific time (daily, monthly, yearly) and explore the data.

OpenET includes six models that are developed based on full or simplified implementations of the surface energy balance (SEB) approach or relies on surface reflectance data and crop type information to compute ET as a function of canopy density using a crop coefficient approach for agricultural lands. The model acronyms are eeMETRIC, geeSEBAL, DisALEXI, SSEBop, PT-JPL and SIMS. In addition, OpenET provides the OpenET ensemble values calculated from an ensemble of these six models.

OpenET Tool to Estimate Crop Water Needs of Avocado Orchards
A case study was conducted to estimate daily ET values in an avocado orchard in San Diego County over a nine-month period (April 15, 2022 through Dec. 29, 2022). The ET estimated from the OpenET models and the OpenET Ensemble was evaluated versus the actual ET measured using the residual of energy balance approach with a combination of surface renewal and eddy covariance equipment (Figure 4).

Figure 4. Ground view of surface renewal and eddy covariance ET station in an avocado site in Escondido.

The actual daily ET (measured) ranged between 0.03- and 0.23-inch d−1 over the study period (Figure 5). The cumulative ET and average daily ET were 33.2 and 0.13-inch, respectively (Table 1). Comparing the cumulative ET and average daily ET values estimated from the OpenET models and measured from the eddy covariance equipment indicated the OpenET Ensemble provided an accurate estimation of ET for this experimental site over the study period (nearly 5% overestimates of the cumulative ET); however, this is not a true finding for some other avocado sites.

Table 1. Cumulative ET, maximum daily ET and average daily ET estimated by the seven OpenET models and measured using surface renewal equipment in an avocado orchard in Escondido. The comparison was conducted for the period of April 15, 2022 through Dec. 29, 2022. The ET values are reported in inch.

The geeSEBAL, SSEBop, PT-JPL and SIMS models showed a greater accuracy than the OpenET Ensemble on ET estimates of some other avocado sites.

While more comprehensive efforts are required to evaluate the accuracy of OpenET models under different canopy features, row orientations and environmental conditions for avocados, this case study demonstrated a good agreement between the results of the OpenET Ensemble and field measurements for an avocado site.

As a user-friendly, free, satellite-based irrigation tool, it is recommended growers consider using OpenET to manage irrigation water and fertilizer more efficiently. Further analysis and evaluation to adopt OpenET in avocado orchards under various conditions will be developed and shared soon.

Figure 5. Daily ET (actual ET or ETa) estimated by the OpenET models and measured using eddy covariance equipment in an avocado site in Escondido.
1234...37Page 3 of 37
-Advertisement-



EDITOR PICKS

POPULAR POSTS

POPULAR CATEGORY

©