Crop Residue Effects on Calcium, Magnesium, Potassium, and Sodium Runoff Losses from a Soil Prone to Crusting

Abstract

In Galicia (northwestern Spain), cultivated soils developed on schists from the Ordenes series are susceptible to surface degradation, mostly when soil organic content decreases. Therefore, management systems that protect the soil and increase its organic-matter content should also improve its quality. However, tillage practices may cause crusting. Degraded soil surface conditions favor surface runoff, thus enhancing nutrient losses. This study examined the effect of applying crop residues to the soil surface on the basic cation nutrient [calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na)] losses by runoff from a tilled soil with relatively low organic-matter content. Runoff and sediment yield were measured on 1-m2 plots using a rainfall simulator with constant 65 mm h−1 intensity. Four successive rainfall applications were performed, the first three at 25 mm each and the last at 65 mm. Added corn straw varied between 0 and 4 t ha−1 in the five treatments studied. Total and dissolved concentrations of the elements studied showed a tendency to decrease due to the effect of corn straw on soil losses. After 140 mm cumulative rainfall, total nutrient losses were as follows: Ca from 12.32 to 28.94 mg L−1, Mg from 20.81 to 148.90 mg L−1, K from 14.20 to 35.17 mg L−1, and Na from 14.99 to 23.41 mg L−1. The relative contribution of the dissolved fraction to the total nutrient content loss was highly variable, being up to 90% for Na. The results confirm that corn residues applied to a degraded soil, with low structural stability, prevent cation nutrient losses.