Green manure

**Green Manure Application:**
– Farmers blend plant discards into the soil for green manure.
– Green manuring involves growing legumes or collecting tree/shrub clippings.
– Harvesters mix green manure crops into the soil to release nutrients.
– Green manure can be added before or after planting cash crops.
– Green manures complement chemical fertilizers to reduce their use.

**Nutrient Release from Green Manure:**
– Heterotrophic bacteria break down green manure into plant nutrients.
– Warmth and moisture aid in nutrient release, similar to composting.
– The carbon-to-nitrogen ratio is crucial for nutrient content in the soil.
– Legumes with rhizobium-rich root systems are preferred for green manure.
– Rhizobium interacts with green manure to retain atmospheric nitrogen.

**Benefits and Limitations of Green Manure:**
– Green manures suppress weeds and provide habitat for beneficial insects.
– Some green manures can be used for grazing and erosion control.
– They reduce the need for additional fertilizers and pesticides.
– Limitations include time, energy, and resources required for green manures.
– Choosing green manure crops based on region and precipitation is crucial.

**Impact of Green Manure on Soil Health:**
– Green manure decreases soil alkalinity and increases humic acid.
– Cover crops increase soil microorganism abundance for decomposition.
– Soil aggregation improves water infiltration, aeration, and soil structure.
– Deep-rooting green manure crops bring up nutrient resources.
– Green manures reduce plant insect pests and diseases, like Verticillium wilt.

**Green Manure Crops and Historical Context:**
– Many green manures are planted in autumn or winter for ground cover.
– Popular green manure crops include alfalfa, buckwheat, cowpea, and clover.
– Green manures have ancient origins, with various cultures using them for soil fertility.
– Incorporating green manure is part of the fallow cycle of crop rotation.
– Historical examples include the Greeks and Romans using faba beans and lupines, and early North American colonists using rye, buckwheat, and oats.