Deep Percolation in a Furrow-Irrigated Sandy Soil

Abstract

ABSTRACT IRRIGATING sandy soils with shallow water tables creates a potential for deep percolation losses of water and nitrogen and consequently, nitrate pollution of ground-water. The amount and nitrate con-tent of percolate was measured with eight vacuum extractors buried be-low the root zone in a sandy, furrow-irrigated cornfield. Total irrigation-season percolation was 17.6 cm, which was 25 percent of the water leaving the root zone. The maximum percolation rate was over 0.37 cm/day when the corn root system was not yet fully developed and when heavy rainfall followed irrigating. More frequent irrigations with smaller amounts of water should reduce percolation. Percolation of nitrate-nitrogen was 2.5 kg/ha/cm of percolate when N (67 kg/ha) was applied in solution in the irrigation water and 3.0 kg/ha/cm of percolate when anhy-drous ammonia N (90 kg/ha) was sidedressed. Percolation of nitrate-nitrogen was affected more by total deep percolation of water than by the method of fertilizer application.