Are there any mechanisms that can explain higher yields when farmers intercrop different plant species?
Productivity of crops grown under monoculture declines because of increased competition for the the same resources, and more susceptibility to diseases and pests.
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Article Diverse perennial crop mixtures sustain higher productivity ...
Intercropping more than two crops is advantageous over mono cropping for the following reasons:
1. Chance of failure of a particular crop is less
2. Cumulative market price is more
3. A crop per unit area is always less advantageous than two, three or four crops from the same area
4. Less removal of nutrients, water, etc from same soil zone(and less chance of depletion thereby) due to differential root length and spread
5. Less chances of disease and pest attack due to preferential differences.
6. Better climate resilience
7.Better supply chain compliance and market responsiveness
8. Relative advantages from neighbouring crop to protect from pest attack, better deployment of allelopathic positive effects on weed, etc
9. Less unit cost requirement for inputs
10. Less labour requirement etc
However, for some specific crops monocropping is always followed for some specific advantages.
Polycultures are more productive than monoculture in following aspects:-
1. It allows more efficient use of space , time .
2. Gives greater productivity and economic profitability
3.Enhances ecosystems, biodiversity, nutrient cycling, soil and water conservation and carbon sequestration .
4.Plants with different nutrient requirements can complement nutrient use or, in the case of legumes, add nutrients to the soil.
It depends on the selection of crops you are going to cultivate in multi-culture/inter-cropping. The system may be more prductive when you intercrop one exhaustive and other restorative/ N-fixing crop, For example intercropping of mungbean with maize or mung-bean with sugarcane or mungbean with cotton.
ANother situation is regarding biological pest control. Inter-cropping of brassica with wheat may attract and culture lady bird beetle earlier which may control wheat aphid in its breakout.
The relation between crops is determined by the term " Allelopathy " which depends on some chemicals produced by some crops and may have negative, positive or no effect on other crops. So, in intercropping growing systems the selected crops must have a positive allelopathic relation which is reflected on higher production for one or all intercropped plants. The allelopathic chemical compounds can be stored in any parts in the plant depending on the crop but mostly the main effect comes from the roots. The other type of relation has to do with the fact that one crop may be a host for a beneficial biological enemy of another crop pests (positive relation) and the opposite may also exist (negative relation).
we strongly agree that the use of organic materials as soil fertilizers has a negative positive value. But we must be brave to see which is the most positive or negative. For farmers now how can the production of their crops be back to normal so they can sustain their family life.
But the negative nature of the material produced will be expected to decrease during the fermentation process ... because many farmers have successfully overcome the problems of land fertility they have (this is a farmer's experience)
Provides complementarity in nutritional absorption and possibility for better use of space.
Efficient management of two or more than two crops on the same piece of land in a definite time to get vacant space occupied by the crop thereby very lesser chances of weed emergence following competition for essential inputs needed...Second important aspects is that due to failure of any of the crops due to poor management practices or stress, risk can be managed... Additional income has to be generated when growing more than two crops as intercrop, mixed crop, or multiple crops .. Inclusion of legumes as companion crop or other crop with cereals may sustain soil health, utilizes all the natural resources efficiently while maintaining ecological balances besides improving soil fertility, productivity and quality... Fixation of non available form of nitrogen into ionic form improve nitrogen status... multi storey cropping is very important to understand the benefits of multiple cropping where plants of different heights and different roots has to be grown together at a definite dimensions and fasion so that there must be efficient utilisation of all the resources either through roots or shoots without competition among crops grown together... synergistic crops help each other by secreting metabolites which stimulate growth and metabolic activities of each crops ..It has been well documented that growing sugarcane with the potato as an intercrop give higher yield of both the crops as that of their sole stands...