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How do crop rotation and green manure help maintain soil fertility?

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A green cotton combine harvests a field of mature cotton plants, with white cotton bolls visible across the landscape. — Agricultural technology Cotton combine harvesting a cotton field.

Both crop rotation and green manure are essential practices in agricultural technology for maintaining soil health and productivity.

Green Manure

Green manure involves growing specific crops—typically annual grasses or legumes—and plowing them into the soil while they are still green. This practice improves soil fertility through several mechanisms:123
* Nutrient Addition: Leguminous green manure crops host bacteria that fix atmospheric nitrogen, which is then returned to the soil when the crop is turned under.14
* Organic Matter: The decaying plant material adds organic matter, which serves as a vital source of plant nutrients and improves the soil's physical condition.3
* Conservation: These crops help reduce soil erosion and minimize nutrient loss caused by leaching.12

Crop Rotation

Crop rotation is the systematic cultivation of different crops in a regular sequence on the same land. It maintains soil fertility by:53
* Resource Management: By alternating crops with different needs (such as row crops, grains, and sod-forming rest crops), farmers can better balance the use of soil resources.5
* Soil Protection: Including sod-forming or rest crops helps provide vegetative cover, which protects sloping land from erosion and adds organic matter to improve productivity.5
* Pest and Disease Control: Rotating crops disrupts the life cycles of insects and diseases that might otherwise thrive in a one-crop system.53