Crop Rotations Involving Cotton In Southeastern Virginia.

Yields of cotton and other crops often decline when grown in continuous monoculture.  In contrast, where rotation crops are appropriately chosen, yields of both crops often increase when measured against either grown continuously.  In 2004, a long-term crop rotation study was initiated to investigate changes in crop productivity and soil quality indicators in the following rotations: 1) cotton-cotton-cotton-cotton-peanut; 2) cotton-corn-cotton-peanut; 3) cotton-peanut; 4) fescue-fescue-cotton-peanut; 5) orchardgrass-orchardgrass-cotton-peanut; 6) fescue-fescue-fescue-peanut; 6) orchardgrass-orchardgrass-orchardgrass-peanut; and 7) cotton-cotton-peanut-soybean. The objective of this study is to determine the relative yields, pest populations, costs and returns of cotton and peanuts grown in selected four-year rotations with other row crops and perennial grasses.  Cotton yielded 325 to 670 kg per ha more in the rotations that included a perennial grass crop than the other rotations.  When peanut followed three years of perennial grass, yields were 450 to 670 kg per ha greater than when peanut was preceeded by three years of other crops.  Northern rootknot nematode popualtions were greater in the cotton-peanut and cotton-cotton-peanut-soybean rotation.  Stubby root nematode populations only increased in rotations including soybean.  Although tall fescue and orchardgrass appeared to be an effective rotation for reducing root knot, ring, and stunt nematodes, both grasses seemed to slightly increase stubby root nematode populations; still populations remained below damage threshold levels for those rotations.  These data indicate that rotations which include perennial grass increase cotton and peanut yields.