Nitrogen is a key element for almond production. Economics plus a potential for leaching nitrogen (NO3-N) below the root zone necessitates efficient use. Application estimates vary, but many almond farmers apply something like 200 pounds of nitrogen per acre per year. Hopefully all of that nitrogen is captured in the tree root zone. Under certain circumstances, losses can occur to volatilization, de-nitrification and possible leaching below the root zone. It’s in everyone’s interest to minimize those losses.
As interest in groundwater nitrogen increases, farm managers across California are going to be placed in the position of documenting efficient nitrogen application and where applied nitrogen goes. Fortunately for the almond industry, research on a “Nutrient Budget Approach and Optimization of Fertilizer Management in Almond” (Patrick Brown et al. at UCD) is underway and starting to offer answers for nitrogen management (Almond Board of California 2012 Research Update).
Just how serious ground water nitrate contamination from agricultural sources is for the Sacramento Valley is still to be determined. Recent studies focused on the southern San Joaquin Valley and the Salinas valley. Additional data will be needed from other regions of the state to sort out how serious of a problem actually exists and what sources contribute to the problem.
(See related: Confusion clouds California groundwater regulations)
Work done by Cooperative Extension Farm Advisors in 1999 looked at NO3-N groundwater levels across the Sacramento Valley. Analysis at fifteen locations from Yolo to Tehama County showed a range of 0 to 11.1 ppm NO3-N in well water samples. 11.1 ppm NO3-N would be 30.2 pounds of Nitrogen per acre-foot (NO3-N (ppm) x 2.72 = pounds of nitrogen per acre-foot of water). Assuming 3 acre-feet of applied water, irrigating with that water could contribute 90.6 pounds of nitrogen per acre. This is a potentially valuable resource whose contribution you should know about in your wells when irrigating. Factoring in nitrogen contributions from irrigation water is an important part of making your farming operation efficient and cost effective. Depending upon location, ground water nitrogen is definitely worth looking at.