IRRIGATION AND WATER USE

IRRIGATION AND WATER USE

Water requirements of peanuts vary during the season. Daily water use is typically low early in the season, peaks during mid-season, and decreases again at crop maturity.

A peanut crop's water demand depends on the growth stage of individual plants. During seedling development, root growth can reach a 1-foot depth in 11 days. By this time, taproots and lateral roots are well developed, but only four leaves will have developed on the plant's main stem.

During vegetative growth, flowering, and pod development, water availability is important. Too much rainfall or irrigation can promote vegetative growth at the expense of reproductive growth. By contrast, the ratio of pods to vegetation is not increased by prolonged drought.

Peak daily water use by peanuts varies from 0.20 to 0.30 inch per day, with an average of about 0.25 inch per day. On extremely hot, dry days, water use can increase to 0.40 inch per day. On such days, even plants growing in a soil profile full of water may wilt during the afternoon. This is temporary wilt that should disappear during the night. The plant's protective mechanism causes the peanut plant to conserve moisture. There is little yield reduction with temporary wilt.

Peanuts use between 20 and 30 inches of water during the growing season. Average rainfall during the growing season, April 1 to October 1, in Roosevelt County is 11.84 inches, leaving a deficit of 8.16 to 18.16 inches that must be provided by irrigation.

All peanut irrigation systems should be able to meet the water needs of the crop over the entire field and should be able to apply water at a rate that does not exceed the soil's infiltration capacity. Uniform water distribution is necessary because the soils in which peanuts are grown have a relatively low water-holding capacity. Irrigation should fill the water holding capacity of the soils, even in sandy and sandy loam soils. Frequent light irrigation in low-water-holding-capacity soils can increase field humidity and promote foliar disease problems.

Too much water, especially in late season and during pod maturation, promotes soil-borne diseases, leaches certain nutrients required for proper pod development and production, and can cause some maturing kernels to germinate, reducing the percentage of sound mature kernels at harvest.