Influence of Supplemental Irrigation and Pre‐Sowing Soil Water Storage on Wheat1

Abstract

AbstractWater stress at certain physiological stages of growth reduces crop yields. The magnitude of water stress and the associated plant response depend upon the initial water content of the soil profile and the timing of additional input of water. A study was conducted to find out the influence of pre‐sowing profile water storage and the timing of supplemental irrigation on wheat (Triticum aestium L.) grown on Fatehpur loamy sand, a Typic Ustochrept. The storage levels were 25, 30, and 35 cm water in the 180 cm profile corresponding to approximately 15, 20, and 25‐cm of available water. The supplemental irrigation was applied at crown root initiation, boot, and grain development stages. Plant height, leaf area index, and number of tillers significantly increased with increase in the amount of profile stored water. The average grain yield increased from 26.1 to 33.1 q/ha when initial water storage increased from 25 to 35 cm. The increase in grain yield between the 25 and 30 cm storage levels was 0.80 q/ha per cm of additional storage, but with further increase in storage level from 30 cm to 35 cm, the increase per cm of additional water declined to 0.60 q/ha. The surface soil at crown root initiation dried to a water content of about 5%. The supplemental irrigation applied at this stage resulted in a maximum grain yield of 36.4 q/ha. Water use increased with increase in initial water storage in the soil and with the earliness of supplemental irrigation. Water use efficiency increased from 28.9 to 34.5 kg/ha per an water with an increase in the initial profile stored water from 25 to 35 cm. This study shows that in soils with water storage around 20 cm/m and substantial loss of soil water occurring early in the season, maximum yield of wheat is obtained when a supplemental irrigation is applied at the crown root initiation stage.