Nitrogen Leaching Potential for Cauliflower (Brassica olaraceae var. botrytis) Grown with UAN32 and Organic Fertilizers.

 "Nitrogen Leaching Potential for Cauliflower (Brassica oleraceae var. botrytis) Grown with UAN32 and an Organic Fertilizer."

Nitrate (NO₃) contamination in ground water is a significant unresolved issue worldwide due to its environmental, economic and social impacts. There has been growing concern about the high NO₃ levels found in California drinking water from wells associated with agricultural operations. Hence, there is a need to implement nitrogen (N) fertilizer and irrigation management practices to mitigate the potential for N leaching from cropping systems. This research focuses on determining the N leaching potential for a Cauliflower (Brassica oleraceae var. botrytis) cropping system fertilized with conventional UAN 32 and an organic soybean based meal ( 7-1-2).  Cauliflower was planted during the Fall 2014 on a sandy-loam soil, fertilized with 225 lbs N/acre of the two fertilizers, and irrigated with surface drip irrigation. The experimental layout was a completely randomized block design with five replicates of the fertilizer treatments and a control with no fertilizer application. In addition to yield and soil nitrate measurements at pre plant and post-harvest, the NO₃ leaching index (LI) was calculated as the ratio of the amount of NO₃ in the third and four feet of the soil to the total amount of NO₃ in the top four feet of soil. There were no significant differences in yield and biomass for plants subjected to the different fertilizer treatments. However the root dry weight for plants receiving UAN-32 were significantly (P=0.04) greater than the control (20%) and organically fertilized plants (6%).  The LI for both fertilizer treatments was 0.15 at pre plant and 0.7 at post-harvest, indicating that NO₃ in the 36-48 inches depth was more prone to leaching than plant uptake. Calculation of the annual N balance for the cauliflower is in progress to determine the potential for N leaching of any excess N not taken up by the crop or stored within the root zone.