Certain Important Definitions in Crops Irrigation
Kharif Rabi ratio or crop ratio. The area to be irrigated for Rabi crop is generally more than that for the Kharif crop. This ratio of proposed areas, to be irrigated in Kharif season to that in the Rabi season is called, Kharif Rabi ratio. This ratio is generally 1.2 i.e. Kharif area is onehalf of the Rabi area.
Paleo irrigation. Sometims, in the initial stages before the crop is sown, the land is very dry. This particularly happens at the time of sowing of Rabi crops because of hot September, when the soil may be too dry to be sown easily. In such a case, the soil is moistened with water, so as to help in sowing of the crops. This is known as Paleo irrigation.
Korwatering. The first watering which is given to a crop, when the crop is a few centrimetres high, is called korwatering. It is usually the maximum single watering followed by other waterings at usual intervals, as required by drying of leaves.
The optimum depth of korwatering for different crops is different. For example, the optimum depth of korwatering for Rice is 19 cm. For Wheat (in U.P) is about 13.5 cm and for sugarcane is 16.5 m.
The kor â€'watering must be applied within a fixed limited period, called Korperiod. If the plants fail to receive this water in time or in sufficient quantity, then they do suffer a significant loss. The kor â€'period depends upon the climate. It is less for humid climates and more for dry climates. The kor period for rice varies from 2 to 4 weeks, and that for wheat varies from 3 to 8 weeks.
Cash Crops: A cash crop may be defined as crop which has to be encashed in the market for processing, etc. as it cannot be consumed directly by the cultivators. All nonfood crops, are thus, included in cash crops. Crops like jute, tea, cotton, tobacco, sugarcane etc, are therefore, called cash crops. The food crops like wheat, rice, barley , maize, etc. are excluded from the list of cash crops.
Crops rotation. When the same crop is grown again and again in the same field, the fertility of land gets reduced as the soil becomes deficient in plant foods favourable to that particular crop. In order to enhance the fertility of the land and to make the soil regain its original structure, it is often found necessary and helpful to give some rest to the land . This can be achieved either by allowing the land to life fallow without any cultivation for some time, or to grow crop which do not mainly required those salts or foods which were mainly required by the earlier grown crop. This method of growing different crops in rotation, one after the other, in the same field, is called Rotation of Crops. A cash crop may be followed by a fodder crop, which, in turn , may be followed by a soilrenovating crop. The cultivators who are found of sowing cash crops always, should be educated and made to understand the advantages of sowing crops in rotation.
The rotation of crops will help in extracting different foods from the soil, and thus avoiding the general deficiency of any one particular type. Moreover, if only one type of crop is grown in the same field, numerous insects and pests (of similar nature) will get developed. The crop rotation will also help in checking such growths. Crop rotation will thus help in increasing the fertility of soil, and reducing the diseases and wastage due to insects, and hence increasing the overall crop yield.
In general, the following rotations of crops may be adopted depending upon the soil conditions:
(i) Wheat â€'Juar â€'Gram
(ii) Rice â€'Gram*
(iii) Cotton Wheat â€'Gram* or Sugarcane
(iv) Cotton Jar â€'Gram*.