Identification of weed competition and its effect on plant growth and yield in ajwain (Trachyspermum ammi Sprague)

Weeds are one of the major problems for farmers in any crop production, which reduce the availability of nutrients, water, sun light to the crop and provide a tough competition to crop. Hence causing severe loss to the crop quality and produce. Weeds are also considered one of the major problems in seed spices. Ajwain is an important seed spice crop grown in Rajasthan, Madhya Pradesh and Andhrapradesh. The research on Ajwain crop is very meagre, it is severely affected by various. biotic and abiotic factors which affects the yield potential significantly. Plant weed competition is one of the major factors, besides insect pest and diseases causing significant yield and quality losses. Ajwain being a rabi crop faces severe competition with the weeds like Chenopodium album, Coronopus didymus, Melilotus spp., Rumex spp., Cyperus rotundus etc. To enhance the yield potential it is must to have an efficient cost-effective weed management modules.Best growth parameters were observed in weed free condition through out growth period treatment. Maximum (98.91%) loss in yield was recorded with the treatment, weedy through out under growth period (T9). Weed count and weed biomass was recorded maximum in T9’whereas minimum in T18. Critical period for weed competition in ajwain was found to be 63 days after sowing. 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 638.15kg/ha was obtained with the treatment weed free throughout growth period, this was also found economically viable which resulted in highest gross return of 99987/ha, net returns  66315/ha and B: C ratio of 1.97. The Benefit: Cost ratio of 0.31 and 1.31 was observed for weed free condition up to 90 DAS (T15) and 120 DAS (T17) respectively.