Factors Affecting Frequency of Irrigation
In rainy season, the humidity is high and rains may be received just when the crop is in need of water. In such case, some irrigation turns could be stopped and frequency may be extended to 20 days. During winter season, also the frequency will be longer than in summer because of less evapotranspiration, dewfall, nighttime humidity, and less sunshine. The frequency may therefore be 15 to 20 days in winter and 6 to 8 days in summer. In summer irrigation, water is given more frequently and hence more frequency of irrigation in summer, medium in winter and less in rainy season.
Stage of Growth of Crops:
During certain stages particularly at flowering and fruit formation stages of crop requires much larges quantities of water than earlier stages. In earlier stage, even if a little less water than estimated daily use is provided, the crop will stand the strain without any harm, perhaps a slight moisture stress may encourage better root growth.
Type of Crop:
The frequency of irrigation will also depend up on the crop. A succulent leaf vegetable will require irrigation more often than cereal crop like Jowar. Crops which are doses of fertilizers need more water than those with a little or no fertilizers.
Light soil requires more frequent irrigation than the loamy soils. Sandy loam soil need to be irrigated every fifth day while clay loam may be irrigated every tenth day. Time required to irrigate an area: The time required to irrigate an area depends up on magnitude of discharge, quantity of water applied, irrigation efficiency and area. The time required to irrigate an area is calculated by formula.
IQT = Ad
I= irrigation efficiency
Q= discharge in cusec
T= time in hours
A= area in acres
d= moisture deficit in soil.
Problem: Calculate the time required to irrigate 4 acres of sugar cane when soil moisture deficit is 2.5 inch, discharge from a weir is 2 cusec and irrigation efficiency is 80 percent.
IQT = Ad
= 80/100 X 2 X t
= 4 X 5/2