The following factors affect any selected method of irrigation:
Topography is the slope of the ground and how much uneven or leveled it is. The irrigation method is selected accordingly.
If the slope is from 0.4 to 8 per cent, corrugation method of irrigation is suitable. If the slope is more than the above limit, then sprinkler method has been considered more suitable for soils which are shallow and permeability is fast.
Similarly, leveled surface flow method, check basin method, furrow irrigation method etc., are adopted. Apart from level differences, the structure and composition of soil also affects the selection of irrigation method. Deep soils have medium and fast permeability for which corrugated method of irrigation is suitable. Rate of seepage of water in the soil depends on its composition.
Ground level irrigation methods are directly affected by climate. The sprinkler system of irrigation is most suitable for such climate. Dryness, humidity and speed of air affect the methods of irrigation.
3. Means of Irrigation:
The sources of irrigation and the chemical composition of the water also affect the irrigation method. At the time of irrigation by tube wells, the sprinkler method or drip irrigation method is suitable, but in canal irrigation, flood method is selected.
The irrigation method is selected according to type of crops and pattern of its sowing. Different crops require different quantities of water. Growth of plants and their height are also affected. In taller plants, check basin irrigation method is more suitable as compared to sprinkler method.
5. Texture of the soils crusting, cracking and infiltration characteristics of the surface soil; nature and depth of relatively impermeable layer(s) in the sub-soil, if any; the water storage capacity of the potential root zone; the magnitude and nature of land slope; the length and size of the field; surface drainage; the nature and extent of salts in the surface soil and the sub-soil, also decide the method of irrigation.
6. Water Conservation:
Water conservation is the demand of the day when the whole world is facing water crisis. Hence, such a method of irrigation should be adopted which uses minimum water but provides maximum humidity to the plants. Sprinkler method and drip irrigation method are the best from the view point of water conservation.
7. Economic Factors and Labour:
While selecting any method of irrigation, the economic condition must be kept in mind as many irrigation methods require heavy initial investment but lesser investment later on. Surface irrigation methods require continuous investment. Along with investment, availability of labour is also an essential factor. As compared to sprinkler method, check basin method of irrigation requires more labour.
Outlook, management skills and financial resources of the farmer; nature of farm machinery used; availability and cost of labour; maintenance facilities and costs of irrigation equipment; availability of power supply should also be considered.
As far as possible, an irrigation method should not only provide a high level of water application efficiency but also ensure its economic viability, sustained soil productivity and wide adaptability to the prevalent features of the farm.