The Crop Consultant Conference will take place on September 25 and 26 at the Visalia Convention Center in Visalia, Calif. (all photos by K. Platts.)
As the agriculture industry continues to evolve, staying informed and connected is more critical than ever. The Crop Consultant Conference, hosted by JCS Marketing Inc., is rapidly becoming a must-attend event for professionals in the field. With growing attendance, an increasing number of exhibits, and a surge in sponsorships, this year’s conference promises to be the most impactful yet.
Growing Attendance and Exhibits Year after year, the Crop Consultant Conference has seen a significant increase in the number of attendees. This surge reflects the conference’s reputation as a leading platform for learning, networking and showcasing the latest advancements in crop consulting. This year, we expect record-breaking attendance as more professionals recognize the value of participating in this pivotal event.
The exhibit hall will feature an expanded array of booths from top industry players, providing attendees with firsthand access to innovative products, services and technologies that are shaping the future of agriculture. From cutting-edge equipment to the latest in crop management solutions, the exhibit hall will be a hub of activity and discovery.
Enhanced CE Management with Online Courses Understanding the importance of continuing education (CE) for crop consultants, JCS Marketing Inc. has developed an online CE manager to streamline the process for attendees. This user-friendly platform allows participants to manage their course schedules, track credits and ensure they meet their professional development requirements seamlessly.
To provide comprehensive educational opportunities, JCS Marketing Inc. is offering 11 online credits before the conference, 9 live credits during the event and an additional 20+ credits available online after the conference. This extensive offering ensures attendees can fulfill all their CE requirements in one place, maximizing both their time and investment.
Record Attendance and Sponsorships Expected The growing success of the Crop Consultant Conference is mirrored by the increasing interest from sponsors. This year’s event is set to feature more sponsors than ever before, each eager to connect with the highly engaged audience the conference attracts. Sponsors recognize the value of aligning with a conference that draws the best and brightest in the industry, providing unparalleled opportunities for brand exposure and relationship building.
Unmatched Networking Opportunities Networking is a cornerstone of the Crop Consultant Conference, and this year, we’ve expanded our offerings to include more networking parties than ever before. These events provide attendees with invaluable opportunities to connect with peers, share insights and forge lasting professional relationships. Whether you’re looking to collaborate on new projects, exchange ideas or simply catch up with old friends, the networking parties are not to be missed.
The exhibit hall will feature an expanded array of booths from top industry players.
Don’t Miss Out With its growing attendance, enhanced educational offerings and increased sponsorship, the Crop Consultant Conference is poised to be the premier event of the year for agricultural professionals. Whether you’re a seasoned consultant or new to the field, this conference offers a wealth of opportunities to learn, connect and grow.
Join us at the Crop Consultant Conference on September 25 and 26 at the Visalia Convention Center in Visalia, Calif. and be part of a vibrant community dedicated to advancing the future of crop consulting. Secure your spot today and ensure you don’t miss out on the premier event of the year.
Figure 1. The flow meter is installed in the main pump system of a processing tomato field. With this setup, the flow meter monitors irrigation information for the whole field (photo by Z. Wang.)
Intensified drought in California has limited groundwater supply for crop production. Therefore, vegetable growers need to implement more efficient and crop-oriented irrigation management. Leveraging online decision-support tools can help growers with real-time, effective monitoring of their irrigation and provide updated irrigation recommendations across the crop cycle. CropManage (CM), developed and operated by UCCE, is a weather-based online decision-support tool that provides recommendations for efficient and sustainable irrigation and fertilization applications. CM combines a wide variety of data inputs including past and future weather, evapotranspiration (ET), satellite imagery, soil physical and chemical properties, irrigation system efficiency and other related variables to generate accurate and timely irrigation and fertilization recommendations based on crop-specific models. Growers can compare their actual irrigation amount and timing to the recommendations made by CM and make the proper adjustment to their crops.
Since 2011, CM has been used by growers, farm advisors and research scientists. CM (https://cropmanage.ucanr.edu/) is a credible, free-access, long-term tool for irrigation scheduling and has been adapted for a variety of vegetable crops (carrots, cabbage, broccoli, lettuce, spinach, etc.), berry crops (raspberry and strawberry), tree nut crops (almond, walnut and pistachio) and agronomic crops (alfalfa and corn). Most of the currently adopted vegetables, however, are mainly produced in the Central Coast, so we have been experimenting with Solanaceous and Cucurbits (processing tomato and watermelon) that dominate the Central Valley to examine the feasibility of adapting CM into these warm-season vegetables.
Table 1. Comparisons of watermelon grower’s actual total application of irrigation (inches per acre) and split between water applied via sprinkler and subsurface drip with the recommendations made by CropManage.
What Did We Do?
Since 2021, we have conducted numerous trials in the northern San Joaquin Valley to compare growers’ irrigation scheduling with the recommendations made by CM to determine if CM is potentially adaptable to processing tomato and watermelon irrigation management.
Figure 2. The flow meter is installed in the main blue flat in a watermelon field. With this setup, the flow meter records irrigation information only for the monitored area (photo by Z. Wang.)
Each field trial began with taking pre-plant soil samples and then was followed by setting up the flow meter, moisture sensors and communication devices to access real-time irrigation information remotely. The location where a flow meter is set highly depends on the setup of the field irrigation system. For processing tomato trials, the flow meter is usually connected to the main pump to monitor the whole field irrigation because all irrigation lines and sub-lines are underground, whereas the flow meter is typically connected to a main line in the watermelon trials to monitor the downstream acreage (Figures 1 and 2). The communication devices include a datalogger that saves the information of each irrigation event (duration, flow rate and total volume) and a cellular modem that transfers the data collected by the datalogger to CM (Figure 3).
Figure 3. The configuration and wiring of the communication devices. The flow meter in Figures 1 and 2 was connected to the CR300 datalogger (top) to store flow rate, duration and total volume of each irrigation event. The collected data communicates with the Cell210 cellular modem (bottom) and becomes available simultaneously in CropManage. A 12V battery (right) and a solar panel shown in Figure 2 were used to supply energy to the devices. (photo by Z. Wang.)
As an ET-based irrigation tool, CM provides irrigation recommendations based on the following equations:
Equation 1: Total ETcrop = Avg. ETref × Avg. Kcrop × days since last irrigation
Equation 2: Recommended irrigation amount = Total ETcrop × 100 ÷ (IDU × (1 – leaching requirement)) – total precipitation
In Equation 1, Total ETcrop is the actual evapotranspiration of processing tomato or watermelon in our cases; ETref is the reference ET near the field, which is accessed through the California Irrigation Management Information System (CIMIS), and Kcrop is the crop coefficient for processing tomato or watermelon, which directly relates to the crop canopy development over the crop cycle. By taking the in-field measurement of percent canopy coverage or accessing the coverage data through NASA’s Satellite Irrigation Management Support (SIMS), CM will provide daily crop coefficients (Figure 4).
Figure 4. Left: Watermelon canopy development curve generated by CropManage over the growing season. We collected the user data (green square) weekly in the field using an infrared camera. The SIMS canopy data (dark diamond) were obtained through NASA SIMS System. Right: Seasonal watermelon crop coefficient generated based on the ETref and crop canopy development.
In Equation 2, IDU stands for irrigation distribution uniformity, which is typically between 85% to 95% for subsurface drip irrigation for processing tomato and watermelon production. If using sprinkler or furrow irrigation, the IDU could be less than 75%. Leaching requirement is the fraction of applied water, including rainfall, that drains below the root zone. Growers can set the leaching requirement to zero when subsurface drip irrigation is used to ease the process of calculating irrigation recommendation. Typically, as no precipitation occurs during the growth of most warm-season vegetables in the Central Valley, Equation 2 can be simplified to Equation 3. Figure 5 shows an example of how much irrigation is recommended by CM. Growers can then adjust the actual irrigation amount based on the CM recommendation (Figure 6).
Equation 3: Recommended irrigation amount = Total ETcrop ÷ IDU (expressed as %)
Figure 5. An example showing the process of calculating the recommended irrigation in CropManage.Figure 6. The comparison of CropManage’s recommended irrigation (0.64 inches) vs grower’s applied irrigation amount (0.60 inches). Since we have the flow meter and communication devices connected, the actual water applied is autopopulated from the flow meter to CropManage without the need to download from datalogger or check the flow meter reading in person.
Adaptability in Processing Tomatoes and Watermelons.
For watermelon, the total amount of water applied was dramatically different among years (2021-23). The biggest difference was contributed by the amount of sprinkler irrigation for transplant establishment. Due to drought conditions in 2021 and 2022, 19 and 14.5 inches of sprinkler irrigation, respectively, were made to transplants prior to shifting to the subsurface drip, whereas only 2 inches of sprinkler irrigation was applied in 2023 (Table 1). Because our flow meter only connected to the lines of the drip system, the information of total amount and schedule of sprinkler irrigation was provided by growers. In Table 1, if we only focus on the CM recommendations for subsurface drip system, it is clear the recommended total amounts were close to the grower’s actual applications in all years. For processing tomato, growers took a well adoption of CM irrigation recommendations with differences of less than 4 inches per acre in 2022 and only 0.3 inches per acre in 2023 between the actual total application and CM recommendations (Figure 7).
Table 1. Comparisons of watermelon grower’s actual total application of irrigation (inches per acre) and split between water applied via sprinkler and subsurface drip with the recommendations made by CropManage.Figure 7. Comparisons between the actual cumulative applied irrigation to processing tomatoes and recommendations made by CropManage in 2022 (top) and 2023 (bottom).
FAQs from Users
Attending CM training workshops is another way to get familiar with this decision-support tool. Each year, we host over 10 in-person workshops statewide as well as virtual trainings. Below are the most frequently asked questions from the workshop attendees and grower-collaborators.
What information do we need to enter in CM when setting up the monitored field?
To get more accurate recommendations, we ask users to put in detailed information about the commodity (crop type, acres of the monitored area, coordinates of the field and planting and harvest dates), irrigation settings (water source, nitrogen concentration in the water, irrigation application rate [typically expressed as inches/hour] and distribution uniformity), soil type (autopopulate with entering the field coordinates) and crop settings (previous crop, crop total nitrogen uptake and water stress setting for crops requiring water reduction or cutoff).
If I don’t have the communication devices, can I still use CM to manage my irrigation application?
Yes. As shown in Figure 6, with the flow meter connecting with communication devices, the actual water applied is autopopulated from the flow meter to CM without the need to download from datalogger or check the flow meter reading in person. Without these devices, you can still have your irrigator keep the irrigation duration and enter the hours of irrigation to CM manually. Then, CM will transfer hours of application to inches applied based on the irrigation settings entered earlier.
I don’t have time to measure the crop canopy coverage. Can I only rely on NASA’s measurements?
Yes, but you need to make sure the field is clean from weeds, especially in the furrows (Figure 8). The percent canopy coverage generated by NASA’s satellite imagery system cannot separate weeded areas from the true coverage of cash crop.
Figure 8. Weed infestation in the furrows of the watermelon field due to sprinkler irrigation and possibly ineffective weed control. In this case, watermelon canopy coverage collected by NASA SIMS will be greater than the actual coverage, potentially resulting in inaccurate irrigation recommendations (photo by Z. Wang.)
I have many fields to manage. Can I assign other farm crew for the fields that rely on CM for irrigation?
Yes. In the Ranch Settings, you can assign as many ranch members as you like and give them different levels of access permissions (e.g., view only vs permission to edit settings).
Can I export the field settings and irrigation information?
Yes. If you have full permission, you can export your field settings and cumulative irrigation charts, which can be viewed as an Excel or PDF file.
What are some resources that can help with my use of CM?
CropManage has a knowledge base including tutorial guidance and more FAQs (help.cropmanage.ucanr.edu/tutorials/). Also, keep an eye on the Veg Views Newsletter for future CropManage hands-on trainings (cestanislaus.ucanr.edu/news_102/Veg_Views/).
If I begin using CM in my field, will you help us co-manage the irrigation?
Yes. If you need, I will be working with growers to set up CM and deliver recommendations. We will work together to make sure CM provides timely and accurate irrigation recommendations, which will serve as an important reference for your irrigation decisions.
Figure 1. Dead stems showing symptoms of shepherd’s crook in alfalfa (photo by S. Orloff.)
Roundup Ready technology builds genetic resistanceto glyphosate into crops, providing an excellent tool for weed management. Initial screening in the early 2000s found good crop safety in alfalfa, leading many growers to rely on glyphosate as the only herbicide. Although using the same chemical control season after season is not a good idea because it may accelerate herbicide resistance in weeds, Roundup Ready alfalfa has been successfully used with few to no concerns. However, the combination of glyphosate and cold weather may cause crop injury, especially in regions where frost events typically follow the herbicide application in spring.
It All Started in Siskiyou County
The issue was first observed in 2014 by Steve Orloff, former UCCE farm advisor in Siskiyou County. A Roundup Ready alfalfa field showed injury after glyphosate application followed by freezing temperatures. The main symptoms were plant stunting, chlorosis and “shepherd’s crook,” in which individual alfalfa stems curl over and die (Figure 1). Yield reductions were also observed for the first cutting. Steve noticed the injury could be related to the glyphosate application because a section of the field where an irrigation wheel line prevented the herbicide application looked perfectly normal.
Injury Symptoms Were Like a Known Disease
Interestingly, the injury seen was very similar to symptoms caused by frost and/or bacterial stem blight (BSB) caused by Pseudomona syringae, a waterborne bacteria present everywhere. The bacteria can exacerbate frost damage due to its protein that mimics a crystalline structure and provides a starting point for ice formation, damaging the plant tissue and serving as an entrance port into the leaves and stems. Once into the plant tissue, colonization leads to infection and symptoms about 7 to 10 days after the frost event. Symptoms on stems start as water-soaked lesions that extend down one side. Leaves become water-soaked and often are twisted and deformed. Currently, there are no resistant alfalfa varieties nor effective control methods besides harvesting the crop earlier.
Let the Research Begin
Steve replicated the symptoms in field trials conducted in 2015-17. The field trials showed yield reductions of up to 0.7 tons/acre in the first cutting in Scott Valley. Crop injury was not observed in a similar field trial conducted in 2014, probably because there was no frost event after the glyphosate application. Similar impacts were observed in a trial at the UC Intermountain Research and Extension Center, near Tulelake, Calif.; additional yield reductions were observed with higher glyphosate rates (Table 1).
Table 1. Yields of first and second cutting in 2015 in the Intermountain Region of California. Trial conducted by Steve Orloff.
Broadening the Scope of the Research
Based on this work, a multi-year project started to investigate the effects of glyphosate rate and application timing at 24 sites over five years, measuring the impact on alfalfa crop height and biomass yield. Results were published in the Agronomy Journal in 2023 (Loveland et al. 2023). All locations in this study were in the Intermountain West (California and Utah), and results showed while summer glyphosate application did not injure alfalfa, spring applications reduced crop height at 76% of the sites and biomass at 62% of the sites.
In sites where glyphosate application resulted in crop injury, low (22 oz/acre) and high (44 oz/acre) rates of glyphosate reduced yields by 0.24 tons/acre and 0.47 tons/acre, respectively (Figure 2).
Figure 2. Effects of low and high rates of glyphosate on crop height and yield when compared to untreated check (UTC). Only sites that showed statistical significance were depicted in the graph.
Data also showed the crop height at glyphosate application influenced the degree of injury (Figure 3), with greater yield reductions at 30 to 40 cm (12 to 16 in) than at 5 to 10 cm (2 to 4 in).
Figure 3. Alfalfa yield response (Mg ha -1) to glyphosate applied at six alfalfa heights up to 40 cm (16 in) at four sites in California and Utah in 2019 (Loveland et al. 2023).
Do Alfalfa Growers Need to Panic?
As alarming as the possibility of injury might sound, its occurrence and degree are widely variable, and the crop resumes normal growth and yields after first cutting. Figure 4 illustrates this complexity and variability throughout experimental sites where harvest yield and crop height were assessed. Note the locations represented in the following graph are colder than the San Joaquin Valley and the injury happened after glyphosate applications in spring.
As of 2024, this type of injury has mostly been reported in the Intermountain West due to its high altitude and cooler weather. However, one field I visited in early February 2024 in Firebaugh, Calif. brought my attention back to the issue. The field was planted in fall 2023 and had many of the symptoms previously mentioned: plant stunting, typical shepherd’s crook, chlorosis and dead stems. While all these symptoms could be exclusively due to bacterial blight infections or frost, parts of the field where glyphosate application was accidentally skipped looked better.
Figure 4. The percentage of sites (17) where spring-applied glyphosate reduced alfalfa first cutting yield, height at harvest, both or neither (Loveland et al. 2023).
Considerations and Recommendations
The exact role of glyphosate, temperature, and P. syringae in the injury is unclear. Although most of the sites in this research showed some level of injury followed by glyphosate application in the spring, the degree of the damage was widely variable. Interestingly, injury symptoms worsened with increasing glyphosate rate and crop height up to when alfalfa was 8 inches tall, but the crop somehow seemed less susceptible when glyphosate was applied at 8 to 16 inches tall.
While the initial cases of BSB of alfalfa were reported in 1904 in Colorado, relatively few cases were reported during the second half of the 20th century. However, the disease has become increasingly problematic in past decades, especially in areas where frost events are favorable. Would the re-emerging BSB in alfalfa have something to do with the extensive use of Roundup Ready technology and the overreliance on glyphosate?Future research is needed to answer this question.
Current UC IPM weed management guidelines for Roundup Ready alfalfa recommend rotating herbicides with different modes of action to reduce the development of herbicide-resistant weeds and avoid glyphosate overuse during the colder winter months. Second, spray glyphosate when the alfalfa is short (<2 in) when using the higher rate (44 oz/acre) or 4 inches when spraying at the lower rate (22 oz/acre). Third, use the lowest glyphosate rate possible according to the weeds present and their stage of development; a soil residual herbicide tank mixed with early glyphosate application should provide adequate late-emerged weed control. Finally, pay attention to the weather forecast; applying glyphosate before frost events increases the likelihood of crop injury, especially in old stands.
References
Loveland, L.C., Orloff, S.B., Yost, M.A., Bohle, M., Galdi, G.C., Getts, T., Putnam, D.H., Ransom, C.V., Samac, D. A., Wilson, R., and Creech, J E. (2023). Glyphosate-resistant alfalfa can exhibit injury after glyphosate application in the Intermountain West. Agronomy Journal, 115, 1827-1841. https://doi.org/10.1002/agj2.21352
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.
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.
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
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.
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.
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.
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.
