Some grasses and annual 'cover crops' are seeded and grown seasonally in fields to provide organic matter or 'green manure'. Various Crotolaria and Sesbania species are grown in this way and then plowed into soils between cropping periods. It also provides sites for nutrients to bind to, holding them in upper soil layers where plants can use them. The slimes and microbial gums produced by decomposing organic matter bind soil particles. The result is a stronger, granular, more permeable and workable soil.
Water infiltrates more easily and is held in small soil pores.
The decomposition process releases hydrogen ions, increasing soil acidity. Without regular organic matter addition, soils become drained of essential plant nutrients and unable to absorb or retain water. As their structure is weakened, soils are much more susceptible to the forces of wind and water erosion. All trees, regardless of how they are arranged or managed, can be regularly harvested for organic matter. This plant material can then be applied to the soil surface around crops as mulch -or mixed with the soil in piles or pits to form compost .