Intercropping,Row cropping ,Mixed intercropping

Intercropping is the agricultural practice of cultivating two or more crops in the same space at the same time (Andrews & Kassam 1976). A practice often associated with sustainable agriculture and organic farming, intercropping is one form of polyculture, using companion planting principles. It is commonly used in tropical parts of the world and by various indigenous peoples (Altieri 1991), but in the mechanized agriculture of Europe, North America, and parts of Asia it is far less widespread. Intercropping may benefit crop yield or the control of some kind of pest, or may have other agronomic benefits.

Design

In intercropping, there is often one main crop and one or more added crops, with the main crop being the one of primary importance because of economic or food production reasons. The two or more crops used in an intercrop may be from different species and different plant families, or they may simply be different varieties or cultivars of the same crop species, such as mixing two kinds of wheat seed in the same field.

The most common goal of intercropping is to produce a greater yield on a given piece of land by making use of resources that would otherwise not be utilized by a single crop. Careful planning is required, taking into account the soil, climate, crops, and varieties. It is particularly important not to have crops competing with each other for physical space, nutrients, water, or sunlight. Examples of intercropping strategies are planting a deep-rooted crop with a shallow-rooted crop, or planting a tall crop with a shorter crop that requires partial shade.

When crops are carefully selected, other agronomic benefits are also achieved. Lodging-prone plants (those that are prone to tip over in wind or heavy rain) may be given structural support by their companion crop (Trenbath 1976). Delicate or light sensitive plants may be given shade or protection, or otherwise wasted space can be utilized. An example is the tropical multi-tier system where coconut occupies the upper tier, banana the middle tier, and pineapple, ginger, or leguminous fodder, medicinal or aromatic plants occupy the lowest tier.

Intercropping of compatible plants also encourages biodiversity, by providing a habitat for a variety of insects and soil organisms that would not be present in a single crop environment. This biodiversity can in turn help to limit outbreaks of crop pests (Altieri 1994) by increasing the diversity or abundance of natural enemies, such as spiders or parasitic wasps. Increasing the complexity of the crop environment through intercropping also limits the places where pests can find optimal foraging or reproductive conditions.

Types of Intercropping

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 (Andrews & Kassam 1976). These are some of the more significant types:

* Mixed intercropping, as the name implies, is the most basic form in which the component crops are totally mixed in the available space.
* Row cropping involves the component crops arranged in alternate rows. This may also be called alley cropping. A variation of row cropping is strip cropping, where multiple rows (or a strip) of one crop are alternated with multiple rows of another crop.
* Intercropping also 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 obviously involves some temporal separation of the two crops.
* 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.