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Conservation management improves runoff water quality: Implications for environmental sustainability in a glyphosate-resistant cotton production system

Locke, Martin A., Krutz, L. Jason, Steinriede Jr., R. Wade, Testa III, Sam
Soil Science Society of America journal 2015 v.79 no.2 pp. 660-671
Gossypium hirsutum, Secale cereale, agricultural runoff, autumn, cotton, cover crops, crop production, dissolved organic carbon, environmental sustainability, fertilizer application, herbicide resistance, minimum tillage, nitrogen content, no-tillage, plant residues, rainfall simulation, rye, soil, spring, transgenic plants, turbidity, water quality, Mississippi
Studies suggest that coincidental adoption of both genetically modified crops (GMC) and conservation management may be mutually complementary, but integrated conservation systems with GMC’s need to be assessed to balance production goals with environmental concerns. Genetically modified cotton (Gossypium hirsutum L.) was managed on replicated experimental plots as either no-tillage (NT) or minimum tillage (MT), and with either no cover (NC) or a rye (Secale cereal L.) cover crop (CC) from 2001 to 2007 near Stoneville, MS. Rainfall simulations in 2007 were used to evaluate water quality in runoff as influenced by management at two critical times: (a) 24 h after fertilizer application in the spring; and (b) 24 h after tillage following crop harvest. With exception of MT-NC in the spring (which had the lowest surface residue coverage, 2%), runoff tended to be higher in the fall than in the spring. Suspended solids and turbidity in runoff were higher for tilled soil (MT) and areas with no cover crop, particularly in the fall. Tillage in the fall was the largest contributor to erosion loss. Similarly, total ortho-P and total Kjeldahl N losses were greatest with tillage in the fall, while the lowest dissolved organic C losses in runoff were in fall with NT. Overall, no-tillage and cover crop treatments reduced nutrient and solids losses. Major factors contributing to these results include recent tillage (in the fall) and coverage of the soil surface by plant residues (NT > MT; CC > NC). This study demonstrated the effectiveness of integrating cover crop and conservation tillage in reducing runoff and nutrient losses in a GMC production system.