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Cover crops help control erosion, prevent nutrient leaching, fix nitrogen, improve soil conditions, and protect seedlings, but also use water, thus affecting soil water relationships for the next crop. Effects are positive when cover crops are managed to improve infiltration and decrease evaporation, or to remove water from a wet soil to allow timely establishment of the next crop. Effects are negative when they limit water for the next crop or aggravate a wet soil condition. Cover crops are better suited to humid and subhumid regions where precipitation is more reliable than to semiarid regions where precipitation is limited. Where cover crops are not used, use of conservation tillage that involves crop residue retention on the soil surface helps conserve soil water and provides many of the benefits of cover crops, except for nitrogen fixation, soil nutrient (especially nitrate) uptake to prevent leaching, excess water removal, and additional organic matter inputs.
Unger et al. (Wed,) studied this question.