When two or more crops are grown simultaneously in the same field, this is called inter-cropping or mixed cropping.
Crops are often grown in mono-culture. This has several advantages for the easier management of the crop (planting, weeding and harvesting), but it has also some disadvantages.
Many pests and diseases multiply more rapidly in a mono-culture than in a mixed crop. In a mono-culture, insects can disperse easier and faster. When other crops are present in the field the insects need more time to search for their host plants. Outbreaks of pests and diseases are generally less serious in mixed cropping systems.
Another advantage of inter-cropping is that the soil is used more efficiently. A mixture of various crops will often give a better coverage of the soil leaving less space for the development of weeds.
If legumes are used in inter-cropping, they will contribute to improved soil fertility.
Some crops produce odors that repel insect pests of other crops. Examples of crops with repelling odors are onion, garlic and lemon grass. When crops are inter-cropped with these strong smelling crops they will help to suppress insect attack.
- Cabbage-Tomato inter-cropping is reported to reduce infestation of Diamond-back moth in the cabbage.
- Cabbage-Garlic inter-cropping will also reduce infestation of Diamond back moth.
In these two examples, the tomato and garlic act as a repellent for the pest.
- Inter-cropping vegetables with marigolds is an effective way to manage root-knot nematodes (Meloidogyne spp.). Most cultivars of African marigold (Tagetes erecta) and French marigold (Tagetes patula) are effective in reducing root-knot population.