Growing of set of crops in a regular succession over a same piece of land (field with) in a specific period of time.
In crop rotation soil improving crops should be rotated in time over the entire farm in a regular sequence as permissible by soil, climatic and economic factors. In general cropping intensity in dryland is only 100 per cent. At few places on partial lands occasionally two crops are taken in favorable season (Monoculture is the rule in dryland agriculture) Increasing the cropping intensity is one of the methods for increasing crop production. Cropping intensity is increased by sequence cropping and double cropping but intercropping may also prove effective measure for increasing production per unit area.
Factors to be considered for planning of crop rotation:
1. Soil type crop and its duration.
2. Livestock on the farm
3. Occurrence of pests and diseases
4. Price and availability of Agricultural produce
5. Cost of labour.
Advantages of crop rotation:
1. Crop rotation maintains and improves soil fertility.
2. Prevent – build up of pests, weeds & soil diseases.
3. Control of soil erosion.
4. Ensures balanced programme of work through out the year.
5. Prevent or limit periods of peak (requirements of irrigation water)
6. Conserve moisture from one season to next.
Characteristics of good rotation:
1. It should be adoptable to the existing soil climate and economical factor.
2. It should be based on proper land utilization.
3. It should contain a sufficient number of soil improving crops to maintain and build up organic matter content of the soil.
4. It should provide sufficient fodder for live stock reared on farm.
5. It should be so arranged so as to make economy in production and labour utilization.
6. It should be so arranged as to help in control of weeds, plant diseases and pests.
7. It should provide maximum area under most profitable cash crop adopted in the area.
Effect of crop rotation so soil:
1. On runoff and soil loss: Crop rotation of Bajra – red gram or groundnut recorded minimum runoff and soil less (82 to 90%) followed by Bajra red gram – horse gram.
2. On bio – logical yield: Legumes cereals or cereals legumes rotations are not only beneficial for runoff but also increase biological yields.
3. Use of crop rotations according to soil moisture:
a) Kharif season: (Shallow and poor moisture retention capacity soils.)
Crop: Bajra, Sorghum, pulses, groundnut followed by follow.
b) Rabi season: (Medium to deep soils fairly good moisture retention capacity soils)
Crop: Sorghum, safflower, gram are rotted with Kharif Bajra sorghum etc.
Monoculture growing of a crop on the same piece of land year after year is known as monoculture or single crop system. Fallow – Jowar
(R) Or safflower fallow in rotation. In scarcity areas only two crops are taken in three years as against one crop every year. Experiments at Dry farming Research Station Shown the variability in benefits of fallow in rotation in increasing the yield of crop in the succeeding year.
By following intercropping system risk is reduced (shared) cropping intensity is increased. Crop selected for intercropping (intercrop) should not compete for moisture quick growing and short duration. The medium soils, depth uptown 45 cm do not provide sufficient moisture to support two crops in sequence (double cropping) even in normal year. These soils are therefore ideal for intercropping. A base crop and intercrop should have different duration of life and growth rhythms. At the same time crops should be cooperative. Bajra + Red gram are ideally suited for this purpose. Red gram gets of benefits from Sept showers and gives high yields. In the events of failure of later rains in Sept bajara already sown gives good yields. In the even of failure of early rains red gram compensates the production. In normal and above normal seasons both these crops boost up total production. For very shallow soils (up to 20 cm depth) Gross like Marvels planted 60 cm apart and established and horse gram is sown as intercrop was found to be most profitable. Intercropping is uneconomic and undesirable during Rabi season because Rabi crops are cultivated mainly on receding soil moisture and thus, it creates Competition for moisture. Gram and Safflower consume more moisture during early period there will be moisture stress at ear head emergence for Rabi sorghum resulting in low yields, Sequence or double cropping. In normal your (normal rainfall) there is possibility of two cops in dry land area giving increased production ranging from 100 to 300 percent over single cropping.
(Source – http://www.agriinfo.in/?page=topic&superid=1&topicid=490)