Inter Cropping is a growing of two or more crops simultaneously on the same piece of land with a definite row pattern e.g. growing set aria + red gram in 5:1 ratio i.e. after every 5 rows of set aria one row of red gram is sown. Thus, cropping intensity in space dimension is achieved.
Multiple cropping in the form of intercropping is predominant in the regions of dry, humid & semi-arid tropics.
The objectives of Intercropping Systems are:
1. Insurance against total crop failure under aberrant weather conditions or pest epidemics.
2. Increase in total productivity per unit land area..
3. Judicious utilization of resources such as land labour and inputs.
Intercropping was originally practiced as an insurance against crop failure under rainfall conditions. At present the main objective of intercropping is higher productivity per unit area in addition to stability in production. Intercropping systems utilizes resources sufficiently and their productivity is increased.
When two crops are to be grown together, they are chosen in such away that there is variation in their growth duration. The peak periods of growth of the two crops species should not coincide. In such arrangements, a quick maturing crop completes its life cycle before the other crop starts. Willey (1979) described the concept as temporal complementary. Greater differences in maturity and growth demands of the crop components, more opportunity is provided for greater exploitation of growth factors and over yielding. This will be achieved either by generic difference in crop species or manipulation of planting dates. Normally short and long duration crops are grown together.
Based on the percent of plat population used for each crop in intercropping system, It is divided in to two viz; additive series and replacement series.
Additive Series: Which is mostly adopted in India, one crop is sown with 100% of its recommended population in pure stand, which is known as the base crops. Another crop known as intercrop is introduced into the base crop by adjusting or changing geometry. The population of intercrop is less than its recommended population in pure stand LER of additive series is greater than replacement series. Additive series is more efficient than replacement series in intercropping system.
In replacement series both the crops are called component crops. By scarifying certain proportion of population of none component, another component is introduced. This type of intercropping is practiced in western countries.
Component Crop: is used to refer to either individual crops making up the intercropping situation. Intercrop yield is the yield of a component crop when grown in intercropping and expressed over the total intercropped area. (I.e. area occupied by both the crops). A simple addition of both the intercrop yields a combined intercrop yield.
Base Crop: is the one which is plated as its optimum sole crop population in an intercropping situation and second crop is planted in between rows of base crop for obtaining bonus yield from intercrop without affecting base crop yield.
Inter Cropping in Cereals: – Inter-cropping with cereal is an excellent way of improving the resource utilization because the serial utilizes the rainy season resources while late maturing crops exploits the post-rainy season resources such as residual moisture. Sorghum is most commonly inter-cropped with pigeon pea on a variety of soils. Sorghum is harvested after 3 ½ to 4 ½ months and pigeon pea matures in about 6-9 months depending on the genotype.
In monocropping of groundnut climate resources like rainfall, temperature and solar radiation are utilized only rainy season, however when red gram is introduced as an inter-crop, these resources are used up to the end winter season and also benefit of late shower rains.
Soybean is also good compatible companion crop with maize. Pearl millet is a quick tillering and fast growing crop that attains full canopy development within 20-30 days of seedling establishment. It can be inter-cropped with groundnut, black-gram or castor.
Inter Cropping in Pulses: For pigeon pea, short duration grain legumes such as black-gram and soybean are the best companion crops in Peninsular India. Groundnut is also a suitable inter-crop.
Inter-cropping in cotton: It is initially a slow growing crop. Any short duration and fast growing crops such as groundnut, black-gram, green-gram or cluster bean are the compatible companion crops.
Inter Cropping in Sugarcane: Sugarcane is slow growing up to 80-90 days. Since the crop is planted in rows 0.8-1.0 m apart, considerable space is available for inter-cropping. Short duration crops maturing in 80-90 days can be advocated as inter-crops. Black-gram and soybean are found suitable. The green manure, Dhaicha can be sown in the inter-space and incorporated at about 2 months.
For successful intercropping, there are certain important requirements:
1. The time of peak nutrient demands of component crops should not overleap in maize + green gram intercropping system, the peak nutrient demand period for green gram is around 35 DAS while it is 50 days for maize.
2. Competition for light should be minimum among the component crops.
3. Complementary should exist between the component crops.
4. The differences in maturity of component crops should be at least 30 days.