Dheer Singh

Crop/weed competition studies in upland rice

Abstract Critical period of crop/weed competition was studied in upland rice during monsoon season from 1981 to 1983. Echinochloa colonum, Seirpus grossus, Dactyloctenlum aegyptium, Cyperus rotundus, C. iria and Trianthema monogyna were the major weed species. Competition from weeds during the first 15 days after sowing (d.a.s.) had no significant effect on the grain yield of rice. Competition beyond 15 d.a.s. caused drastic reduction in the grain yield. Grain yield of rice Increased significantly with the increase in the duration of weed‐free period up to 45 d.a.s. during two years. However, further increase in the weed‐free period up to 60 d.a.s. caused significant improvement in the grain yield of rice in only one year. Weeds emerging after 45 d.a.s. were lower in density and their growth was suppressed by the crop. Density of weeds emerging between 15 and 30 d.a.s. was high and could compete with the crop resulting in reduced grain yields. The period during 15 to 45 d.a.s. was found to be the most imp...

Management of complex weeds in sugarcane by ametryn + trifloxysulfuron

Field experiment was conducted to evaluate the bio-efficacy of ametryn 73.15% + trifloxysulfuron 1.85% W.G for the management of grasses, sedge and broad-leaf weeds in sugarcane. The experiment consisted of nine treatments laid out in randomized block design with three replications. Cyperus rotundus, Ipomoea spp, Brachiaria reptans, Echinochloa colona, Digitaria sanguinalis and Dactyloctenium aegyptium were observed as major weeds. Among herbicide treatments, the lowest density of total weeds was observed with ametryn + trifloxysulfuron at 1500 g/ha though the differences were nonsignificant when compared with its lower dose i.e. 1250 g/ha at 15 and 45 days after application (DAA). Application of ametryn + trifloxysulfuron 1250 and 1500 g/ha recorded significantly lower weed dry weight over any other herbicidal treatment at 15 and 45 days. Highest weed control efficiency of total weeds at both 15 and 45 DAA were recorded with the application of ametryn + trifloxysulfuron 1500 g/ha which was closely followed by 1250 g/ha. The highest cane yields (9.04 t/ha and 10.51 t/ha) were recorded from weed free plot being at par with hand weeding thrice at 30, 60 and 90 DAP.

Crop‐weed competition studies in greengram and blackgram

Abstract The critical period of weed‐crop competition was studied in greengram (Vigna radiate) during the monsoon seasons of 1982 and 1983, the summer seasons of 1983 and 1984 and in blackgram (Vigna mungo) during the monsoon seasons of 1982 and 1983. The major weed species during the monsoon seasons were Echinochloa colonum, Dactyloctenium aegyptium, Eleusine indica, Digitaria sanguinalis, Celosia argentea, Phyllanthus niruri, Cleome viscosa. Cyperus rotundus and C. iria. During the summer seasons E. colonum, D. aegyptium, Physalis minima, Portulaca quadrifida and C. rotundus were the major weed species. Competition during the first 15 days after sowing (d.a.s.) in greengram during the summer season had only a small depressing effect on grain yields. Grain yields of both crops during two seasons increased significantly with the increase in weed‐free duration up to 30 d.a.s. However, a weed‐free condition maintained beyond 30 d.a.s. induced no further improvements in grain yields. Weed emergence and growt...