Nitrate-nitrogen in effluent from agricultural tile drains in California

Abstract

The first research phase consisted of extensive monitoring of tile drainage effluents collected in important agricultural areas in California. More intensive investigation of nitrate-N within a few soil profiles was done during the second phase. Nitrate-N concentrations were not well correlated with any measured parameter. The amount of nitrate-N contained in tile effluent was quite well correlated with total water discharge and fertilizer N application. Higher amounts of nitrate-N were removed from coarse-textured soil profiles as compared to profiles containing a layer of fine-textured material. Some alluvial soils on the west side of the San Joaquin Valley apparently contain significant native N which contributes to high nitrate-N concentrations and total mass emissions in tile effluent. It appears that the most positive approach to controlling nitrate-N in irrigated agriculture is through control of leaching.