Residue Management in Double‐Crop Conservation Tillage Systems¹

Abstract

Crop residues have become an increasingly important renewable natural resource. They can serve to maintain optimum crop production on the nation's severely eroding 45.3 million ha of cropland as well as decrease the increasing cost of synthetic N fertilizer. Conservation tillage technologies have been recently identified as a high priority research need for sustaining agronomic productivity in the humid USA. Three double‐crop tillage systems—spring and fall disking, fall disking, and no‐tillage—were evaluated for 4 years on a Southern Piedmont Ultisol (Cecil sandy loam—a clayey, kaolinitic, thermic Typic Hapludults). These tillage systems were considered conventional (CT), minimum (MT), and continuous no‐till (NT), respectively. Wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] were used in the double‐crop systems as high stover producing as well as medium N fertilizer requiring crops. Six orthogonal N fertilizer rates ranging from 0 to 250 kg ha−1 were imposed on each tillage system. Both conservation tillage systems (MT and NT) were manageable in the short term (1 or 2 years) and produced significantly more sorghum grain than the conventional system. Grain yields (4 years) and favorable soil fertility status suggest the MT system was the best double‐crop management system in the long range (>2 years). The sum of wheat and sorghum grain yield increased significantly (5.0 to 7.4 Mg ha−1 year−1) in a linear manner with stover up to 11.5 Mg ha−1 year−1. This suggests some crop use of the 62 kg N ha−1 year−1 returned to the land in stovers when N fertilizers were applied at the recommended rate (100 kg N ha−1 year−1). It appears that N fertilizer rates may be reduced progressively in small quantities for optimum double‐crop yields in longterm conservation tillage systems on Southern Piedmont lands.

Response of no-till and conventionally planted grain sorghum to weed control method and row spacing

“…Similar results were reported by Langdale et al (1984), Sanford et al (1973), Elkins et al (1980), and Lal (1981. In no-till systems chemicals gave significantly better weed control because the pre-plant application of glyphosate killed existing weeds and the postemergence application of atrazine gave effective residual weed control.…”

“…Langdale et al (1984) studied residue management in double cropping conservation tillage systems and found that conservation tillage significantly increased yield of grain sorghum when compared to conventional tillage systems. They reported that grain sorghum in rotation with soybeans in double cropping systems increased yield of both sorghum and soybeans.…”

Winter Wheat Responses to Surface and Deep Tillage on the Southeastern Coastal Plain

“…By leaving more than 30% of the soil surface covered with residues, conservation tillage may reduce the severity of drought stress that occurs during the growing season. For many soils, surface residues can enhance crop productivity by increasing rainfall infiltration into the root zone (1,2), reducing water runoff (12,14), de-829 creasing soil losses (14), and improving soil tilth (10,11). Surface residues may also improve soil water contents by decreasing soil temperature, impeding the diffusion of water vapor from the soil surface, acting as an absorbant for water vapor diffusing from the soil, and reducing wind velocity at the soil surface (7,17).…”

Strategies for research and management in reduced-input agroecosystems

“…Rice et al (1986) suggested that no-tillage systems in Kentucky reached a state of soil nitrogen equilibrium in approximately ten years. However, soil organic matter (SOM) accumulation under reduced tillage varies considerably with life-zone, soil type, length of time under cultivation, and cropping practices (Hargrove et al, 1982;Langdale et al, 1984;Lugo et al, 1986;Gallaher and Ferrer, 1987). Thus, accumulation of soil organic matter and development of nutrient recycling processes (panel B) may require longer periods of transition in some systems than in others.…”