The factors are as below:
1. Net profit per hectare
2. Growth habit and nutrient requirement of different crops.
3. Soil type and slope.
4. Infestation of weeds, pests and diseases.
5. Irrigation facilities.
6. Climatic conditions.
7. Land, labour, power and other resources.
8. Food habit and requirements.
9. Market facilities.
In light of above factors or consideration the mechanics of setting good crop rotation can be summarized as below. Or there are certain accepted principles, based on which the crops should be selected for crop rotation.
1. The crops with taproot should be followed by those, which have a fibrous root system. This helps in proper and uniform use of nutrients from the soil and root do not compliant with each other for uptake of nutrients.
2. A shallow rooted grain crop, deep rooted cash crop and restorative crop (legume crop) should be included in the rotation for providing food, fodder, cash and maintaining the fertility and productivity of soil.
3. The leguminous crops should be grown after non-leguminous crops because leguminous fix atmospheric “N” into soil and more organic matter to soil, while non- leguminous are fertility crops. Apart form this, legumes need more phosphate and less nitrogen while non- legumes need more of nitrogen and relatively low phosphorus. So nutrient requirements of these crops are different and such combination helps farmers in reducing cost of cultivation.
4. Selection of the crops should be based on soil, climate season and market demand.
5. More exhaustive crops should be followed by less exhaustive crops because crops like potato, sugarcane, maize, etc. need more inputs such as better tillage, more fertilizer higher number of irrigations, more insecticides, better care than crops like oil seeds, pulses, etc. which need little less care or little less inputs.
6. As per availability of irrigation water, two or three crops are taken in a year on same land under irrigated conditions. However a dry crop should be included in the rotation to avoid damage to the soil due to continuous irrigation.
7. In case of rain fed farming (assured rainfall) on moisture retentive soils after harvest of Kharif crop some minor crop requiring less moisture like pulses or cereals may be grown. E.g. Rice (Kharif) – Gram/ Wal (Rabi), Green gram or black gram- Rabi sorghum, sorghum, sorghum –gram.
8. The selection of crops should be problem based e.g. on sloppy lands which are prone to soil erosion, an alternate cropping of erosion promoting ( erect growing crops like millet etc) and erosion resisting crops like legumes, should be adopted. Selection of crops should suit the farmer’s financial conditions.
9. Both wide spaced crop and thickly planted crops should be included in rotation for control of weeds. E.g. wide spaced crops like tobacco controls weeds due to frequent inter culturing ands dense ( thick ) forage or legume crops controls weeds and soil erosion e.g. soybean.
10. Crops with different botanical relationship should be altered for control of weeds, pests and diseases, e.g. If crops of Graminae are grown gramminaceous crops.
11. Effect of previous crop on succeeding crop should be considered for obtaining maximum yield and harvest quality of produce.
12. Enough elasticity may be kept in rotation so that if pest or diseases destroys a crop, another crop can be substituted
13. Fertile and well-drained land should be utilized for important good rotation, less fertile land for soil improving crops (legumes) and salt tolerant crops on acidic, saline or alkali soils.
14. The ideal crop rotation should be built up around a hub crop for which the greatest comparative advantages exist. E.g. In areas of dairy industry oil seeds like groundnut or pulses will supply cattle feed (oil cakes and roughages) or in irrigated areas near cities, growing of vegetables or floriculture will be profitable.
15. Selection of crops should be demand based, i.e. the crops, which are needed by the people or area. So that produce can be sold at a higher price. The area devoted to each crop should be constant from year to year.