Intercropping

Intercropping is a multiple cropping practice that involves the cultivation of two or more crops simultaneously on the same field, a form of polyculture. The most common goal of intercropping is to produce a greater yield on a given piece of land by making use of resources or ecological processes that would otherwise not be utilized by a single crop.

The degree of spatial and temporal overlap in the two crops can vary somewhat, but both requirements must be met for a cropping system to be an intercrop. Numerous types of intercropping, all of which vary the temporal and spatial mixture to some degree, have been identified.

Mixed intercropping consists of multiple crops freely mixed in the available space. In the 21st century, it remains a common practice in Ethiopia, Eritrea, Georgia, and a few other places. Freely mixed intercropping has been practiced for thousands of years. In medieval England, farmers mixed oat and barley, which they called dredge, or dredge corn, to make livestock feed. French peasants similarly ground wheat and rye together to make pain de méteil, or bread of mixed grains. Ease of harvesting and buyer preferences led later farmers to plant single-species fields instead.

A row crop is a crop that can be planted in rows wide enough to allow it to be tilled or otherwise cultivated by agricultural machinery, machinery tailored for the seasonal activities of row crops. Such crops are sown by drilling or transplanting rather than broadcasting. They are often grown in market gardening (truck farming) contexts or in kitchen gardens. Growing row crops first started in Ancient China in the 6th century BC.^{[citation needed]}

Temporal intercropping uses the practice of sowing a fast-growing crop with a slow-growing crop, so that the fast-growing crop is harvested before the slow-growing crop starts to mature. This can provide greater yield than either crop alone.

Further temporal separation is found in relay cropping, where the second crop is sown during the growth, often near the onset of reproductive development or fruiting, of the first crop, so that the first crop is harvested to make room for the full development of the second.

Crop rotation is a related practice but is not a form of intercropping, as the different crops are grown in separate growing seasons rather than in a single season.

Alley cropping has crop strips alternating with rows of closely spaced tree or hedge species. Normally, the trees are pruned before planting the crop. The cut leafy material - for example, from Alchornea cordifolia and Acioa barteri - is spread over the crop area to provide nutrients. In addition to nutrients, the hedges serve as windbreaks and reduce erosion. In tropical North and South America, various species of Inga such as I. edulis and I. oerstediana have been used for alley cropping. Weed control is inherent to alley cropping, by providing mulch and shade.