The interaction between different components crops: In intensive cropping, when crops are grown in association (intercropping) or sequence (sequential cropping) interaction between different component crop species occurs, which is essentially a response of one species to the environment as modified by the presence of another species (commonly referred to as interference or interaction).
Interference can be divided into two
a) Removal Reactions of One Plant on its Environment and
b) Additive Reactions when Something is Added.
When some factor is removed from the environment, the resulting response of neighboring species can be negative, positive or neutral. Competition among plants is one example for removal interactions. Some such additive interactions are allelopathic and symbiosis. When crops are grown in sequence, residual effect of the preceding crop influences the succeeding crop this may be harmful or helpful. The toxic chemicals (allelopathic chemicals) left in the soil by the roots of sunflower crop inhabit germination of the succeeding crop. The stubbles of sorghum with high C: N ration causes immobility of nitrogen, thus causing nitrogen deficiency in early stages of the succeeding crops. The roots of legume crops and their residues add nitrogen to soil.
The interaction may be:
2. Non-competitive and
1. Competitive Interaction: – One species may have greater ability to use the limiting factor and will gain at the expense of the other and this is called as competitive interaction or interference. Or when one or more growth factors are limiting, the species that is better equipped to use the limiting factors(s) will gain at the expense of the other and this is called as competitive interaction. In mixed crop communities, if the associated species are to share their growth from a limited pool of recourses such as light water or nutrients, then it is non-competitive interaction or interference.
2. Non-competitive:- If the crops are grown in association and the growth of either of the concerned species is not affected, such type of interaction is called non-competitive interaction or interference. Or if these resources (growth factors) are present in adequate quantities as a result of which the growth of either of the concerned species is not affected, then it is non-competitive interaction or interference.
3. Complementary: – If one species is able to help the other it is known as complementary interaction. Or if the component species are able to exploit to supply of growth factors in different ways (temporal or spatial) or if one species is able to help the other in supply of factor (like legumes supplying part of N fixed by symbiosis to non-legumes), it is complementary interaction or interference. This also referred to as Annidations.
Interaction in Inter-Cropping: Competition between the associated crops in mixed crop communities has been discussed by Donald (1963), Trenbath (1976) and Willey (1979).