INTERCROPPING

Sustainable agriculture seeks, at least in principle, to use nature as the model for designing agricultural systems.  Since nature consistently integrates her plants and animals into a diverse landscape, a major tenet of sustainable agriculture is to create and maintain diversity.  Nature is also efficient.  There are no waste products in nature.  Outputs from one organism become in- puts for another.  One organism dies and becomes food for other organisms.  Since we are modelling nature, let us first look at some of the principles by which nature functions. By understanding these principles we can use them to reduce
 Intercropping offers farmers the opportunity to engage nature’s principle of diversity on their farms. Spatial arrangements of plants, planting rates, and maturity dates must be considered when planning intercrops. Intercrops can be more productive than growing pure stands.  Many different intercrop systems are discussed, including mixed intercropping, strip cropping, and traditional intercropping arrangements.  Pest management benefits can also be realized from intercropping due to increased diversity.  Harvesting options for intercrops include hand harvest, machine harvest for on-farm feed, and animal harvest of the standing crop.

So, then, how can we begin to model our agricultural pursuits after some of these natural principles? Can we look for patterns in nature and imitate them?  Some pioneering farmers have been able to utilize nature’s principle of diversity to their advantage.  Results of their efforts include lower cost of production and higher profits. Among the practices that promote diversity and stability are:
  

Enterprise diversification—

Risk reduction through stability of income and yield are two of the reasons people diversify their crop and live- stock systems.  Increasing diversity on-farm also reduces costs of pest control and fertilizer, be- cause these costs can be spread out over several crop or animal enterprises.

 Crop Rotation —

 Moving from simple monoculture to a higher level of diversity begins with viable crop rotations, which break weed and pest life cycles and provide complementary fertilization to crops in sequence with each other.

 Farmscaping—

Diversity can be increased by providing more habitat for beneficial organisms, habitats such as borders, windbreaks, and special plantings for natural enemies of pests.

Intercropping—

Intercropping is the growing of two or more crops in proximity to pro- mote interaction between them.  Much of this publication focuses on the principles and strategies of intercropping field crops.  A related ATTRA publication, Companion Planting, provides more information on intercropping of vegetable crops.

 Integration—

On-farm diversity can be carried to an even higher level by integrating animals with intercropping.  With each increase in the level of diversity comes an increase in stability. This publication focuses on intercropping and provides a section on integrating livestock with crops.

 Intercropping Concepts

Most grain-crop mixtures with similar ripening times cannot be machine-harvested to produce a marketable commodity since few buyers purchase mixed grains.  Because of limited harvest options with that type of intercropping, farmers are left with the options of hand harvesting, grazing crops in the field with animals, or harvesting the mixture for on-farm animal feed. However, some intercropping schemes allow for staggered harvest dates that keep crop species separated.  One example would be harvesting wheat that has been inter planted with soybeans, which are harvested later in the season.  Another example is planting harvestable strips, also known as strip cropping. When two or more crops are growing together, each must have adequate space to maximize cooperation and minimize competition between them.  To accomplish this, four things need to be considered:

1) spatial arrangement, 2) plant density, 3) maturity dates of the crops being grown, and 4) plant architecture.

1    SPATIAL ARRANGEMENT

There are at least four basic spatial arrangements used in intercropping.  Most practical systems are variations of these (3).

•  Row intercropping—growing two or more crops at the same time with at least one crop planted in rows.
•  Strip intercropping—growing two or more crops together in strips wide enough to permit separate crop production using machines but close enough for the crops to interact. 
•  Mixed intercropping—growing two or more crops together in no distinct row arrangement.
•   Relay intercropping—planting a second crop into a standing crop at a time when the standing crop is at its reproductive stage but before harvesting.
  

2    PLANT DENSITY

 To optimize plant density, the seeding rate of each crop in the mixture is adjusted below its full rate.  If full rates of each crop were planted, neither would yield well because of intense over- crowding.  By reducing the seeding rates of each, the crops have a chance to yield well within the mixture. The challenge comes in knowing how much to reduce the seeding rates. For example, if you are planning to grow corn and cowpeas and you want mostly peas and only a little corn, it would be easy to achieve this.  The corn-seeding rate would be drastically cut (by 80% or more) and the pea rate would be near normal.  The field should produce near top yields of peas even from the lower planting rate and offer the advantage of corn plants for the pea vines to run on.  If you wanted equal yields from both peas and corn, then the seeding rates would be adjusted to produce those equal yields.

3    MATURITY DATES

 Planting intercrops that feature staggered maturity dates or development periods takes advantage of variations in peak resource demands for nutrients, water, and sunlight.  Having one crop mature before its companion crop lessens the competition between the two crops.  An aggressive climbing bean may pull down corn or sorghum growing with it and lower the grain yield.  Timing the planting of the aggressive bean may fix the problem if the corn can be harvested before the bean begins to climb.  A common practice in the old southern U.S. cotton culture was to plant velvet beans or cowpeas into standing corn at last corn cultivation.  The corn was planted on wide 40-inch rows at a low plant population, allowing enough sunlight to reach the peas or beans.  The corn was close enough to maturity that the young legumes did not compete.  When the corn was mature, the beans or peas had corn stalks to climb on.  The end result was corn and beans that would be hand harvested together in the fall.  Following corn and pea harvest, cattle and hogs would be turned into the field to consume the crop fodder. Selecting crops or varieties with different maturity dates can also assist staggered harvesting and separation of grain commodities. In the traditional sorghum/pigeon pea intercrop, common in India, the sorghum dominates the early stages of growth and matures in about four months.  Following harvest of the sorghum, the pigeon pea flowers and ripens.  The slow-growing pigeon pea has virtually no effect on the sorghum yield. 

      PLANT ARCHITECTURE

 Plant architecture is a commonly used strategy to allow one member of the mix to capture sunlight that would not otherwise be available to the others.  Widely spaced corn plants growing above an understory of beans and pumpkins is a classic example.

Inter Cropping And Its Advantages

Intercropping: Growing of two or more crops simultaneously on the same piece of land (field). There is a crop intensification in both time and space dimensions. There is intercrop competition during all or part of crop growth.

Type of intercropping: 
1. Mixed intercropping               
2. Row intercropping     
2. Strip intercropping 
4. Relay intercropping

Definitions of Intercropping system: 
1. Mixed Intercropping: Growing two or more crops simultaneously with no district row arrangement. 
2. Row Intercropping: Growing two or more crops simultaneously where one or more crops are planted in rows. 
3. Strip Intercropping: Growing soil conserving and soil depleting crops in alternate strips running perpendicular to the slope of the land or to the direction of prevailing winds for the purpose of reducing errosion. 
4. Relay Intercropping: Seeding planting two or more succeeding crops after flowering and before the harvest of the standing crop.

Advantages: 
1. Intercropping gives higher income per unit area than sole cropping. 
2. It acts as an insurance against failure of crop in abnormal year. 
3. Intercrops maintain soil fertility as the nutrient uptake is made from both layers. 
4. Reduce soil runoff. 
Limitations: Intercropping system is uneconomical and undesirable during rabi. 
Crops to be considered for intercropping. 
A) Kharif crops: 
1. Medium black soils: 
a) Pearl millet + Red gram 2: 1
b) Pearl millet + Horse gram / Kidney bean / cow pea Inter row of pearl millet. 
3. Soils up to 20 cm depth 
a) Pearl millet + red gram (30 - 60 - 30 cm)
B) Rabi crops: 
Safflower + Gram (2: 1)
D) Fodder for milch animals: Sorghum bajara + Cowpea or horse gram or kidney bean.

In rained areas of Maharashtra: 
1. Sorghum / pearl millet / cotton + red gram / black gram or kidney bean or cowpea or groundnut. 
2. Groundnut + Sunflower. 
Cotton + soybean, cotton + Black gram 
Safflower + gram

How intercropping economizes water use:
Selection of intercrop is one the basis of duration of crop and growth rethyms. The short duration crop gets harvested and long duration crop gets the benefits of September showers and produces more yields. E.g. Pearl millet + red grams. 
LER: It is observed that under the rainfall situation deviating from 2090 to 50 percent, the intercropping system of bajara + red gram is more stable as cowpea to the pure crops tried. On an average, the land equivalent ratio (LER) comes to 77 percent compared to pure crop.