Inspection Services Blog

Key Learnings from the FREP/WPHA Conference


The twenty fourth annual FREP/WPHA Conference took place on October 26-27, where speakers from industry, academia, and agricultural consulting provided cutting edge information on nutrient management in California agriculture.

The conference presentations covered a wide range of nutrient management topics including education and outreach, soil microbiology, government regulations and irrigation, in addition to many applied plant nutrition and soil fertility topics. FREP staff has summarized some Key Learnings below that reflect our take-home messages from each of the presentations. The presentation files are available on the FREP website at:


Attendees at the 2016 FREP/WPHA Conference

Attendees at the 2016 FREP/WPHA Conference

Agriculture and Groundwater Banking for Increasing Water Security. Dr. Graham Fogg, UC Davis.  Water quality and quantity are intricately linked. The potential of groundwater banking for increasing water security in California is far greater than is currently practiced. While all of California’s 140 reservoirs amount to 42 Million Acre Feet (MAF), there is room for another 140 MAF in the Central Valley subsurface. Potentially, both flood plains and agricultural lands can be utilized for groundwater recharge projects. Increasing clean water recharge is key for stabilizing and improving groundwater quality and reversing the decline of groundwater storage. California’s Central Valley provides 6 million acres of irrigated croplands that could serve as spreading grounds for groundwater recharge. Alfalfa is among the most attractive options because of high acreage in California (~1 million acres), likelihood to find lands on highly permeable soils, relatively low use of fertilizer, and it is commonly flood irrigated with surface water. Soils across California have been studied for groundwater recharge suitability and Soil Agricultural Groundwater Banking Index (SAGBI) maps are available on the UC Davis website,

Salinity and the Threat to Productivity of Orchard Crops in the Central Valley. Dr. Patrick Brown, Professor, UC Davis.  Salinity affects over four million irrigated acres of annual and perennial crops in California. However, salt impact on many California cropping systems remains poorly understood, especially under low volume irrigation. In perennial crops, even short-term salinity can have implications for years beyond the exposure. Going forward, studies should focus on long-term effects of salinity on crops, as well as identifying which part of the root zone is relevant for salinity analysis, especially with more irrigation methods moving toward pressurized irrigation systems.

Evaluating Biochar’s Potential in California Agriculture. Dr. Sanjai Parikh, UC Davis.  Biochar is not a specific product, but rather a class of products with differing characteristics, depending on the biochar source and pyrolysis temperature. While benefits of adding biochar to soil are recognized, the results have not been consistent. There is significantly more research needed to understand the short- and long-term impacts of biochar on soil quality and crops in California. There is some evidence to suggest that the benefits of biochar are most recognized in neutral to acidic soils with coarse to medium texture. With more research, biochar could potentially be created for a specific intended use.

Status of the Irrigated Lands Regulatory Program in the Central Valley. Sue McConnell, Central Valley Water Quality Control Board.  The State Water Board’s proposed order in response to the East San Joaquin order petition is precedential, meaning that it affects the regulations in other regions across California. This year is the first year of data collection from Central Valley grower coalitions. Many lessons have been learned from the first cycle of nitrogen reporting with many challenges and opportunities remaining, including refining the ways reported data is used for grower outreach and education.

CCAs and Compliance with Water Board Regulations. Fred Strauss, Crop Production Services.  There are currently 1,200 registered Certified Crop Advisors (CCA) in California, with 50 more being added this year. The CCA training program offers a variety of new certifications including: sustainability (new in 2016), manure management, 4R nutrient management, and IPM resistance management. Many CCAs are cautious about certifying the grower’s Nitrogen Management Plans due to liability concerns. These concerns have led some companies to instruct their CCAs not to certify Nitrogen Management Plans due to liability. Nonetheless, CCAs are the most qualified professionals to assist growers with regulatory compliance due to their knowledge and experience with crop production and nutrient management.

Panel Discussion: Growers’ Perspective on Challenges to Improving Nutrient Management and Irrigation Practices in California. Moderator: Dr. Karen Lowell, USDA-NRCS. Panelists: Chuck Hornung, Hornung Brothers Ranch; Darrell Cordova, Triple C Farms; Chris Miller, Miller Farms.  Farming in California is a constant learning process due to changing variables that are often outside a grower’s influence. Growers are working to improve their systems and their efficiency. There is always a need for better tools and new technology to be able to monitor soil, water and plant status. Even when a practice succeeds, it may be difficult to quantify the benefits because there are so many moving parts. Every new addition or change on a farm has a learning curve and another parameter to be considered. Growers have improved their systems over time by using new technology, carefully monitoring water and nutrients, and by having eyes in the field all the time. One of the most challenging and time-consuming parts of farming is the ever-increasing reporting load required by regulatory agencies.

Nitrogen Management Training for Growers. Mark Cady, CDFA.  Growers in the Central Valley are required to complete a Nitrogen Management Plan, and if they farm in high-vulnerability areas, have a certified CCA sign the plan, or they can certify their own plan if they complete a nitrogen management training program. CDFA’s FREP worked with UC ANR to provide the CCA certification training. In the past few years, around 890 CCAs have been certified to complete nitrogen management plans for growers. Based on this curriculum, FREP worked with UC, Grower Coalitions, and the Coalition for Urban and Rural Environmental Stewardship to provide training for growers. Since winter 2015, 31 training sessions have been held with 1,916 growers in attendance and 82% have passed the certification exam.

Irrigation Scheduling Using ET-Based Methods. Dr. Khaled Bali, UC Kearney Agricultural Research and Extension Center.  There are several programs available to assist growers with irrigation scheduling (Basic Irrigation Scheduling, CropManage, and work is being done to add more field crops and Central Valley crops to CropManage. Three basic types of measurement are prevalent: ET based, plant based and soil based. From flood irrigation to pressurized systems, the primary differences are frequency, volume and efficiency. A new technology by Tule Technologies measures actual ET (no Kc is necessary). Many major California crops need updated Kc’s.

Investing in Your Soil: The Role of Organic Matter in Soil Function. Rex Dufour, National Center for Appropriate Technology.  Ecological soil management is an attempt to relink the carbon and nitrogen relationships in soil and often results in a higher phosphorus application. We can maximize soil health with regular additions to soil organic matter, following the 4R fertilization rubric, and by minimizing physical disturbance to soil. Seventy four percent of degraded land is west of the Rockies. Soil management is best done by replicating nature: regular addition of organic matter, use of diverse sources of organic matter, protecting the soil surface (cover crops or mulch, and keeping soil disturbance to a minimum (physical and chemical).

Soil Life, Soil Management: What Every Agronomist Should Know About Microbes. Dr. Kate Scow, UC Davis.  Microbes are inextricably linked with soils and we can manage some of the drivers of soil microbes, but not all (e.g. climate). Managing microbes to regulate N uptake means adding carbon to the soil which encourages a diverse soil food web. Depending on soil microbe composition, different management practices will have differing effects. For example, bacteria respond strongly to cover crops and less to tillage, while fungi do the opposite. Resilience of agroecosystems is largely based on the strength of their biological communities. We need to understand these communities better because research has shown that microbial communities in soils with more organic matter are resistant to dramatic changes in environmental conditions. Future research will employ microbial community genomics to better understand the identities of microbes present under different soil management practices. Promoting microbial heterogeneity in soils may be key to more resilient soils and more sustainable crop production.

The Role of Nutrients in Pest Management. Dr. Lacey Mount, Dellavalle Laboratory, Inc.  With crop diseases, combinations of a susceptible host and enough time, and a favorable environment will lead to disease. Symptoms and location will show what disease is present and where it originated. While under and over-fertilization can often leave a crop susceptible to disease, the severity of a disease will often be impacted by the fungal population, which is driven by soil structure. Overall, symptoms are good for identifying disease, but testing is important to confirm diagnoses.

Ecological Approach to Nutrient Management for Soil Health. Dr. Z. Kabir, USDA-NRCS.  Only 12% of the earth’s land surface is used for agricultural production. Current soil erosion rates globally threaten agriculture such that eventually we may be farming on poor quality subsurface soils. While nitrogen and phosphorus are the most limiting nutrients worldwide, they are also the greatest pollutants to groundwater aquifers and aquatic ecosystems. Phosphorus sources are so limited around the globe that we may have reached a situation of peak P, where P extraction has reached its maximum and may be declining. In ecological systems, net inputs are close to harvest outputs, inputs are diverse and cover crops contribute carbon and nitrogen to the soil, and plant nutrients are released slowly and in balance with crop growth. Good soil health in these terms means that soil organic carbon is maintained and increased to support a resilient soil ecosystem for sustainable crop growth.

Deficiency to Toxicity: The Role of Boron in California Crop Production. Dr. Sebastian Braum, The Tremont Group, Inc.  Boron is crucial for the formation of cell walls in plants, and deficiency often results in reduced photosynthetic and nitrogen use efficiency and inhibits the growth of new tissues. California’s Coastal Range tends to have high soil boron concentrations because of its origin as marine sediment. Streams flowing out of the coastal mountains carry high levels of boron to cropping areas. Boron mobility in crops varies and depends on whether the crop uses complex sugar alcohols as the primary photosynthetic metabolite, and it can determine the plant’s response to high B levels.

Nitrogen Budgets in California Rice Systems: What Do We Know and How Can We Improve? Dr. Bruce Linquist, UC Davis.  Agricultural rice system water is highly managed, allowing growers to control and minimize nitrogen losses from the system. Potential losses include ammonia volatilization, leaching, and denitrification. Nitrogen use efficiency in these systems is approximately 50%, similar to other California crops. To minimize losses in these systems, it is best to reduce the amount of surface applied N, use better weather forecasting to avoid rainfall between fertilizer application and field flooding, and time field drainage appropriately.

Improving N Use Efficiency of Cool Season Vegetable Production Systems with Broccoli Rotations. Richard Smith, UC Cooperative Extension Monterey County.  The active root zone of broccoli goes to two feet deep and beyond, which makes it ideal for scavenging nitrogen left behind by the previous crop (via leaching or mineralization). The second foot depth of roots is not established until 50 days after planting, so ensuring that the plant has good initial soil fertility is crucial to ensuring the roots are developed enough to access the two-foot depth. There is evidence to suggest that similar root development occurs in other crops including cabbage, cauliflower and peppers.

A poster session on the first day of the conference featured nutrient research from around California.

A poster session on the first day of the conference featured nutrient research from around California.

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