Residue and Water Management Effects on Aggregate Stability and Aggregate-Associated Carbon and Nitrogen in a Wheat-Soybean, Double-Crop System

Abstract

Agricultural sustainability rests on the principle that the needs of the present population can be met while protecting the ability of future generations to meet their needs. Consequently, soil sustainability is paramount to assuring continued agricultural production. Soil structure and C storage can be influenced by producers' choices regarding residue and water management techniques. The objective of this study was to evaluate the long-term effects of alternative residue (i.e., tillage, residue burning, and fertility–residue level) and water management (irrigated and dryland) practices and soil depth after 10 yr of consistent management on total water-stable aggregate (TWSA; >0.25 mm) concentrations, size-separated aggregate concentrations, and corresponding C and N concentrations in a wheat (Triticum aestivum L.)–soybean [Glycine max (L.) Merr.] double-crop production system in the lower Mississippi River Delta region of eastern Arkansas. The TWSA concentration was unaffected by residue burning and not always negatively impacted by conventional tillage (CT). The TWSA concentrations were 19% greater (P < 0.05) under CT than no-tillage (NT) within the dryland low-fertility–residue treatment combination. High-fertility–residue resulted in 18% less (P < 0.05) TWSA than under low-fertility–residue within the irrigated-NT treatment combination. Under high-fertility–residue, TWSA concentrations were 13% less (P < 0.05) in the 5- to 10-cm depth under irrigation and were 10% less (P < 0.05) in the top 5 cm under dryland management compared to the low-fertility–residue treatment. The smallest two size classes (0.25–0.5 and 0.5–1.0 mm) comprised over 80% of the TWSA. Water-stable aggregate concentrations in the largest two size classes (1–2 and >2 mm) were unaffected by all treatments imposed. Results of this study indicate that interactions between long-term residue and water management practices can significantly impact soil aggregate stability, and thus are useful for aiding the determination of long-term agricultural management practices that improve soil quality in the Lower Mississippi River Delta region.