Weed competition affecting growth and yield in ajwain (Trachyspermum ammi)

Weeds compete with crop plants throughput the plant growth period and causes significant losses in quality, productivity and profitability. Seed spices are more sensitive to crop weed competition as they are grown under arid conditions where moisture is the limiting factor. A study was carried out to identify the critical period of weed competition in ajwain (Trachyspermum ammi Sprague) during 2012-13 to 2014-2015 at ICAR-National Research Centre on Seed Spices, Ajmer, Rajasthan. Treatments included weedy and weed-free condition for different growth periods, i.e. 15, 30, 45, 60, 75, 90, 105, 120 days after sowing (DAS) along with weed free throughout growth period and weedy throughout growth period. Weedy period up to 30, 45, 60, 75, 90, 105, 120 DAS and weedy throughout growth period reduced the seed yield significantly to the tune of 321.4, 463.0, 607.7, 705.9, 852.9, 950.4, 1072.9 and 1162.4 kg/ha respectively as compared with the weed free throughout growth period. Weed free up to 15 DAS to 120 DAS decreased the seed yield from 1039.4 to 99.0 kg/ha as compared to the weed free throughout growth period. Weedy period up to 75 DAS gave tough competition to the crop for growth which was reflected in yield attributes and seed yield of ajwain. The maximum yield of 1244.5 kg/ha was obtained with the treatment weed free throughout growth period, this was also found economically viable which resulted in highest gross return of ` 136891/ha, net returns ` 102953/ha and B: C ratio of 3.03. Critical period for weed competition in ajwain was found to be 54 days after sowing.