Using Winter Annual Cover Crops in a Virginia No-till Cotton Production System
Daniel, James B. II
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Cotton (Gossypium hirsutum L.) is a low residue crop, that may not provide sufficient surface residue to reduce erosion and protect the soil. A winter annual cover crop could alleviate erosion between cotton crops. Field experiments were conducted to evaluate selected winter annual cover crops for biomass production, ground cover, and N assimilation. The cover crop treatments were monitored under no-till and conventional tillage systems for the effects on soil moisture, cotton yield and quality. Six cover crop treatments, crimson clover (Trifolium incarnatum L.), hairy vetch (Vicia vilosa L.), hairy vetch and rye (Secale cereale L.), rye, wheat (Triticum aestivum L. amend. Thell.), and white lupin (Lupinus albus L.), and two tillage systems (conventional and no-till) were arranged in a split-plot design with four replications. Cover crop biomass production depended on climate conditions. Ground cover percent and N assimilation by cover crops were directly correlated with the amount of biomass produced within cover crop treatments. Within a range of near average winter temperatures, all cover crops except lupin provided enough ground cover to comply with federal conservation tillage standards. More ground cover remained on the soil surface further into the cotton growing season following the small grain treatments compared to the legume cover crop treatments. Soil moisture was higher (P < 0.05) under no-till compared to conventional tillage during the periods of drought in 1997. Tillage system had no effect on cotton yield and quality in 1995 and 1996. High cover crop biomass production coupled with an extended cotton growing season in 1995 resulted in higher lint yield for cotton grown following the hairy vetch + rye treatment compared with cotton grown following the wheat treatment. High heat unit accumulation in October 1995 led to the over maturity of cotton fiber and high micronaire values for cotton grown following all cover crop treatments. The high micronaire values (5.0 - 5.2) for cotton grown in all cover crop treatments except hairy vetch + rye (4.9), resulted in a market price deduction of 1.4 cents per kilogram of lint in 1995. All cover crops used in this experiment, with the exception of lupin, provided enough ground cover within a range of average winter temperatures to meet federal conservation requirements. The winter annual cover crops in a no-till cotton production system provided greater soil moisture conservation during periods of drought, and produced cotton yields and quality comparable to conventional tillage.
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