Water use and yield of winter wheat in Northern India as affected by timing of last irrigation

Summary

Standard local practice in Northern India is to continue irrigation of winter wheat crop almost up to harvest, based on the farmer's belief that this treatment increases grain weight and yield. The effect of an early cut-off of irrigation on the water use was studied in a three-year experiment on a deep, sandy-loam soil.

Wheat, sown during the second or third week of November, received its first irrigation four weeks later. Subsequently treatments included irrigations of 7.5 cm water depth applied after 10 cm of cumulative pan evaporation minus rainfall had elapsed since the previous irrigation up till mid-April; irrigations of 7.5 cm up till mid-February and thereafter irrigation equal to 75 and 100% soil-water deficit in the 0–180 cm profile around March 10 with no later irrigation; and a similar treatment with one additional irrigation after making up the water deficit.

Least irrigation water was used from the treatment in which 75% water deficit was restored around March 10 and no further irrigation was applied. This treatment increased the average extraction of profile water by 4 cm compared to treatments in which irrigation was continued until mid-April. Profile water depletion was inversely related to the amount of irrigation. Grain weight and yields from the various treatments harvested in the last week of April were unaffected by the treatments.