Intercropping on Organic Farms
Intercropping Technical Criteria
When two or more crops are cultivated in an intercropping system, each crop should have adequate space, to maximize cooperation and minimize competition between the crops. To accomplish this, attention should be paid to the specific local conditions (climate), the choice of crops, the arrangement of crops in space and time, the plant density, maturity dates of the different crops, plant architecture, and spatial arrangements.
Almost any type of crop or combination of crops can be used for intercropping. Choose crops that are locally grown and well adapted to the climatic conditions. Seeds or other plant material can be obtained from other farmers, on local markets or from specialized seed producers. Consider including a pulse crop in the intercrop, as pulses fix nitrogen and help to improve soil fertility and soil structure.
When two or more crops are combined in a field, plant densities need to be adapted to maximize yields. If full rates of each crop were planted, neither would yield well because of intense over-crowding.
Planting and Maturity Dates
In intercropping systems, it is an advantage if the different crops in the mixture have different maturity dates, with different times of peak demand for nutrients, water and sunlight, thereby reducing competition.
In designing an intercropping system, it is useful to pay attention to differences in plant architecture between the crops given that different crops may have a different architecture, i.e. height and width of the plant.
Intercropping has four general spatial arrangements. There is mixed intercropping, no distinct row arrangement; strip intercropping, growing crops in strips wide enough to separate them, yet narrow enough to allow interaction between them; relay intercropping, growing two or more crops during differing parts of their life cycles; and row intercropping, at least one crop is planted in rows.
Mixed or Multiple Intercropping
Mixed intercropping or mixed cropping is the growing of two or more crops at the same time with no distinct row arrangement (See Figure 9.1). This type of intercropping is common in intensive subsistence systems, especially in subtropical and tropical areas of the world. It is often used where fields are relatively small and field operations involve mostly manual labor. Mixed intercropping ensures that the ground is covered, and therefore weeds are suppressed.
Strip intercropping is the growing of two or more crops together in strips wide enough to allow separate production of crops using mechanical implements, but close enough for the crops to interact (See Figure 9.2). There are two types; contour strip cropping and field strip cropping. Contour strip cropping follows a layout of a definite rotational sequence and the tillage is held closely to the exact contour of the field.
Relay intercropping describes a cropping pattern in which the lifecycle of one crop overlaps that of another crop (See Figure 9.3). For example, a second crop can be planted into an existing crop when it has flowered (reproductive stage) but before harvesting. There is thus a minimum temporal overlap of two or more crops. Relay intercropping is practiced in regions where the growing season is too short to permit two sequential crops.
Row intercropping is the cultivation of two or more crops simultaneously on the same field with a row arrangement (See Figure 9.4). The productivity of row intercropping is influenced by the specific combination of crops, their spacing, and planting dates. This type of intercropping is ideal for shade loving plants like groundnuts and cowpeas.
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