Planting Seeds - Food & Farming News from CDFA

CDFA, UC Davis collaborate on study about growers and fertilization

An example of fertigation.

This research project is directed at understanding influences and grower decisions about the adoption of improved nitrogen management practices.


Nitrogen best management practices (BMPs), such as applying fertilizers at the right time, right rate, right place and in the right form (the 4 R’s), and soil and leaf sampling, are key to managing crop productivity. Practices such as these and many other promising BMPs have been coming out of CDFA’s Fertilizer Research and Education’s (FREP) research-based projects for more than two decades. Many of these practices have economic and environmental benefits, so what is preventing their implementation?

With a grant from FREP, a team of researchers from University of California, Davis has been collaborating with Water Quality Coalitions in the Central Valley to explore the key barriers to implement practices that increase nutrient use efficiency. This project also aims to establish a baseline of current practices that can be used to measure progress with practice adoption.


The first phase of the project is aimed at gathering information on current management practice adoptions levels, perceived risks, knowledge gaps and decision-making processes. Researchers assessed the use of improved nitrogen management practices by surveying growers in two Central Valley Water Quality Coalitions. The survey questions focused on the use of the following practices and their barriers to adoption.

  • Fertilizer practices: Use a nitrogen budget to determine fertilizer rates; split fertilizer applications; verify plant nutrient status with in-season leaf sampling
  • Soil practices: Take soil samples to measure residual nitrate; apply organic matter (compost or manure); plant cover crops
  • Irrigation practices: Schedule irrigation by measuring plant-water status or using evapotranspiration (ET) measurements; use soil moisture sensors; test irrigation systems for distribution uniformity

Preliminary Results

Data were collected from 565 growers over the course of seven grower education meetings. The two Central Valley Water Quality Coalitions represent approximately 8,000 growers and 1.6 million acres of irrigated farmland in the Central Valley.


Preliminary results indicate that growers operating on large parcels, and in perennial crop systems reported higher adoption rates for nearly all practices and named fewer challenges to adoption. Uncertainty was the most common barrier identified for seven out of ten practices. This illustrates the importance and demand for outreach and education around nitrogen management practices. Messaging to farmers should address the risks and benefits associated with BMPs and technical workshops are essential in aiding on-farm implementation. The potential for improving yield and crop quality are the largest recognized benefits and should be emphasized in outreach materials.

This information and more was also gleaned through a series of interviews with twenty growers who participated in the initial survey. Growers emphasized the importance of outreach and extension and cited issues with lack of clarity around nitrogen regulations and policy.

Next Steps

The second phase of the project will be an expanded survey designed to assess social, political, and economic factors influencing decision-making and adoption of improved nitrogen management practices. Surveys were mailed out to the Colusa-Glenn Sub watershed of the Sacramento Valley Water Quality Coalition, in February 2018 and will be distributed to growers in the San Joaquin County and Delta Water Quality Coalition and East San Joaquin Water Quality Coalition regions in June 2018.

Link to FREP blog

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