WATER FRONT ADVANCE UNDER VARIABLE BORDER WIDTH AND INITIAL SOIL MOISTURE CONTENTS UNDER WHEAT (Triticum aestuivium L.) CROP – I: HYDRAULICS AND IRRIGATION EFFICIENCIES

Border irrigation experiments were conducted on wheat ( Triticum aestivum L.) crop at Water Technology Centre, Indian Agricultural Research Institute (IARI) New Delhi in winter season (October-April) of 2013-2014 to study the border hydraulics (cutoff ratio, border width and stream discharge), irrigation efficiencies, grain and biomass yields for 4 border sizes (2, 3, 4 and 5 m widths) to economize the water use. Optimizing the border width under varying soil moisture contents prior to irrigation was attempted. The border of length 25 m required 30.2 minutes (min) to 78.1 min for irrigation for a fixed cutoff length of 15 m. The water front advance time up to cutoff length was 10 min and 27.3 min for border widths varying from 2 to 5 m; respectively corresponding to the selected stream discharge of 1.5 l/s. The water front advance time was inversely proportional to the initial soil moisture contents. The travel time to cutoff point of 15 m for three soil moisture contents namely q 1:14.2, q 2:16.5 and q 3:17.2%; varied from 10.0-11.7 min for the border size (width) of 2.0 m, 14.0-15.6 min for the border size of 3 m; 20.0-23.4 min for the border size of 4 m whereas, it took 24.5- 27.3 min for 5 m border size. The best border size was identified as 4 m without any yield penalty. The effect of the stream discharge was not pronounced based on yields. Due to uniform cutoff ratio there was no significant difference in the amount of water use. Hence, the border size of 4 m was rated the best.