Nonuniform leaching of nitrate and other solutes in a furrow‐irrigated, sludge amended field

Abstract

Nitrate leaching losses were estimated using soil core samples from three different locations in a furrow irrigated, N fertilized and sludge amended cotton field. These losses were controlled by irrigation efficiency, as well as sources and quantities of N applied. Statistical comparisons of sample locations and N treatments revealed N treatment to be less significant than the field sampling location. However, sludge amended soils had significantly higher levels of nitrates in the root zone and consequently suffered higher nitrate leaching losses. A NO₃‐N profile (30–210 cm) balance indicated that about forty percent (40%) of available NO₃‐N was leached below the root zone (0–150 cm) in the upper two‐thirds of the field plots during the pre‐plant irrigation. Whereas, the lower one‐third of the field did not experience significant nitrate losses below the root zone. A one‐dimensional finite difference layered model, was used to estimate the depth of moisture penetration at the field (furrow) locations following pre‐plant irritation. It was concluded that the lower one‐third of the plots received less than 50% of mean plot application (30 cm) water during pre‐plant irrigation.