Benefits
When cover crops are turned over into the soil, they contribute nutrients to the main crop so that less chemical fertilizer is required. The amount of the contribution depends on the biomass, which varies over time and depends on rainfall and other factors. The greater the biomass, the greater the nutrient turnover. Legume cover crops turn over nitrogen fixed from the atmosphere. Reports indicate that legumes in general have higher foliar nitrogen contents, from 20 to 45 mg g-1.
Bare soil resulting from intensive tillage can lead to soil erosion, nutrient losses, and offsite movement of pesticides. In addition, weeds can germinate and grow without competition. Living mulches can reduce water runoff and erosion, and protect waterways from pollution. Living mulches have also been shown to increase the population of organisms which are natural enemies of some crop pests.
Living mulches control weeds in two ways. When they are seeded before weed establishment, they suppress weeds by competition. In some situations, the allelopathic properties of living mulches can be used to control weeds. For example, the allelopathic properties of winter rye (Secale cereale), ryegrasses (Lolium spp), and subterrain clover (Trifolium subterraneum) can be used to control weeds in sweet corn (Zea mays var "rugosa") and snap beans (Phaseolus vulgaris).
Populations of ground-dwelling predators were greater in a corn and soybean rotation with alfalfa and kura clover living mulches than without a living mulch. This situation was due in part to a change in the composition of vegetation in the agricultural system.
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