Evaluation of the impact of alternative wheat residue and water management on soil properties and soybean yield in a wheat-soybean double-crop system, Eastern Arkansas

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Date

2008-12

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University of Arkansas

Abstract

Long-term agricultural sustainability requires evaluation of agricultural management practices that may improve and sustain soil quality and crop productivity over time. The objective of this study was to determine the 6-yr effects of tillage [conventional (CT) and no-tillage (NT)], wheat residue burning (bum and no bum), residue level (low and high), and 3-yr irrigation (irrigated and dry-land condition), on soybean [Glycine max (L.) Men-.] yield, soil physical and chemical properties in the top 10 cm, and weed population diversity in a wheat [Triticum aestivum (L.)]-soybean double-crop production system. A field experiment was conducted from fall 2001 through fall 2007 in the Mississippi River Delta region of eastern Arkansas on a Calloway silt loam (fine silty, mixed, active, thermic Glossaquic Fraglossudalf). Soil bulk density increased at a greater magnitude under NT (1.22 to 1.35 g cm'3) than CT (1.19 to 1.26 g cm*3) during the first 3 years, but declined at a similar rate in both tillage treatments after the third year. Irrigation increased soil pH (0.2 pH unit yr*1), Mehlich-3 extractable soil Mg (55.1 kg Mg ha*1 yr*1), and total C contents (0.11 kg C m*2 yr*1) compared to dry-land condition which had no pH change, but had less increase of extractable Mg (36.6 kg Mg ha*1 yr*1), and total C content (0.04 kg C m*2 yr*1). Soil organic matter (SOM) increased over time in all treatment combinations. Total C (TC) increased at a greater rate in the no bum (0.077 kg C m*2 yr*1) and high-residue-level (0.073 kg C m*2 yr*1) than in the bum (0.051 kg C m*2 yr*1) and low-residue-level (0.054 kg C m*2 yr*1) treatments. The total weed species density was greater under CT (513 plants m*2) than under NT (340 plants m*2) early in the soybean growing season in 2006, but did not differ between tillage treatments in 2007. Perennial weed density was greaterunder bum (99 plants m"2) than no bum (59 plants m’2) in 2006, and in 2007, was greater under NT than CT but unaffected by bum. Retaining crop residues and herbicide application reduced the density of all weed species, grass, and broadleaf weed species. Tillage, burning, and residue level generally did not affect soil penetration resistance in the top 0.20-m in 2003 and in 2006, but soil cone index (CI) was consistently lower under bum than no bum at all depth below 0.20 m. The CI at the 0.05-m depth increased by 35% after 4 years compared to after 1 year of NT soybean. Soybean yield differed over years of the trials. Soybean yield declined during the first 3 years, but increased over the subsequent 3 years in all treatment combinations. Economic analysis showed that management practices with NT will likely be more profitable than the traditional CT practice even when the fertilizer and diesel costs continue to increase. Therefore, NT and non-burning with any residue level have great potential to improve soil quality, reduce weed pressure in the soybean growing season, and maintain profitability in the wheat­ soybean double-crop production system.

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Keywords

Wheat-soybean, Soybean yield, Wheat residue, Soil properties, Water management, Eastern Arkansas, Soil organic matter

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