Nitrogen Management for Irrigated Crops
The Central Valley is one of the most productive agricultural regions in the world, a horticultural wonder consisting of 7 million irrigated acres with over 300 different crops. With modern irrigation systems and adequate fertilization practices, growers have elevated their farming practices to coax spectacular yields of high-quality crops. A recent note from the CDFA indicates the enormous value of California agriculture: “In 2015, California's farms and ranches received approximately $47 billion for their outputs.” Read the full report here.
Greenhouse farming could be considered a closed-loop system, where all inputs required for crop production are 100% contained within the walls of the greenhouse. That’s a great goal to shoot for in the rest of the ag world farming in the great outdoors. In a practical sense, it’s not achievable. Still, our objective is to farm insuch a way that contains most water, soil and fertilizer within the farm boundary. The Regional Water Quality Control Board has been charged with the responsibility of monitoring movement of resources off the farm, which includes monitoring our groundwater resources for contamination by ag chemicals and nitrogen. Recently, they have directed their spotlight on growers to tighten up their nitrogen application in an effort to prevent additional leaching of nitrogen into the groundwater reservoir. Proper management of nitrogen is essential for sustaining maximum crop yield and the economic viability of the farm, as well as ensuring the protection of our natural resources and safety of our citizens.
Nitrogen fertilizer is typically applied at an agronomic rate to ensure maximum yield; extensive research and countless field trials have been conducted to determine these rates for most crops. Since 2014, California growers have been required to account for their nitrogen applications with a simple budget process: nitrogen applied should equal nitrogen removed by the harvested crop. Such a balance is an important step to ensure that “extra or unused” fertilizer is not wasted and leached into the groundwater reservoir.
Attached is a Nitrogen Management Plan template that is to be completed by the grower. It’s a simple walk through the worksheet to arrive at a nitrogen balance, but it does require some effort to pull in the factors needed in the calculation:
- Tax assessor’s parcel number, Farm ID, Coalition number
- Crop grown and projected yield per acre (based on historical trends)
- Nitrogen required to grow the crop (based on scientific studies and historical nitrogen need)
- Residual nitrogen carryover from a recent soil analysis
- Nitrogen content of irrigation water (from analysis of irrigation water sample)
- Total inches of irrigation water to be applied in current season
- Nitrogen content of fertilizers applied in current season, including all organic, foliar and fertilizer forms
Most Helena CCAs are certified to help the grower with this process, and have the supplemental nitrogen management certificate required to sign off on these plans. Please contact your Certified Crop Advisor if you have questions.
- Don Wolf, CCA, PCA; Agronomist, Northern CA; Helena Chemical Company