Irrigation System Effects on Applied Fertilizer Nitrogen Movement in Soil

Abstract

AbstractMovement of unused fertilizer nitrate‐nitrogen (NO3‐‐N into shallow underground water strata by way of irrigation return flows has become a concern as irrigation has increased. Previous research has been largely conducted with furrow and sprinkler irrigation systems in areas of low rainfall and in many cases in the absence of a growing crop. We studied, directly in the field, the effects of furrow, sprinkler, and subirrigation on the movement of fertilizer NO3‐‐N in a supplementally irrigated area in the presence of sweet corn (Zea mays L.).Sodium nitrate enriched with 15N was band applied below the surface at rates of 124 and 105 kg of N/ha in 1973 and 1974, respectively. Soil samples were periodically taken in 30‐cm vertical increments through each fertilizer band, the center of the bed and beneath each furrow. Under sprinkler irrigation the fertilizer bands tended to move down with somewhat less lateral movement close to the soil surface than with the other systems. Also, movement out of the surface 30 cm was faster than for the other irrigation systems. Under furrow irrigation the fertilizer tended to move toward the center of the bed and then moved downward. With subirrigation the fertilizer moved upward and outward toward the furrows and then moved downward. The fertilizer remained in the upper 30 cm of soil longest with subirrigation.