Crop Residue Effects on Organic Carbon, Nitrogen, and Phosphorus Concentrations and Loads in Runoff Water

Abstract

Degraded soil surface conditions favor surface runoff, thus enhancing sediment and nutrient losses. This study examined the effect of crop residues on carbon (C), nitrogen (N), total phosphorus (TP), and total dissolved P (TDP) losses by surface runoff in an agricultural loamy soil with degraded structure. Runoff and sediment yield were made over 1‐m2 plots using a rainfall simulator with constant 65 mmh−1 intensity. Four successive rainfall applications were performed, the first three ones 25 mm each and the last one 65 mm. Added corn straw varied between 0 and 4 tha−1 in the five studied treatments. Organic C, N, and TP concentrations in runoff showed a trend to decrease because of the effect of corn straw on soil losses. However, TDP concentration increased with increasing crop residue in the lower two rainfall events. Sedimentary P constituted the major proportion of P in runoff. After 140 mm of cumulative rainfall, nutrient losses were as follows: organic C from 137.7 to 792.7 kgha−1, N from 16.65 to 88.82 kgha−1, TP from 1.72 to 7.87 kgha−1, and TDP 57 to 87 gha−1. Total losses of the studied nutrients were correlated with soil losses.