Management of Setaria barbata in upland rice

Abstract

A field experiment on "Management of Setaria barbata in upland rice" was undertaken during 2019-21 with an objective to find out a cost-effective weed management practice for Setaria barbata in upland rice. The investigation was carried out at Coconut Research Station, Balaramapuram in Thiruvananthapuram district during the period from June 2020 to October 2020. The experiment was laid out in randomised block design (factorial RBD), with three replications. Treatments were 16 (2x8) combinations of 2 factors; Factor A (seed bed preparation) and Factor B (weed management practices). The treatments included two seed bed preparation, viz., stale seedbed (s1) and no stale seedbed (s2) and weed management practices, viz., preemergence application of oxyfluorfen @ 0.15 kg ha-1 followed by (fb) fenoxaprop-p-ethyl @ 0.06 kg ha-1 at 25 DAS (w1), pre-emergence application of oxyfluorfen @ 0.15 kg ha-1 fbcyhalofop-butyl @ 0.135 kg ha-1 at 25 DAS (w2), pre-emergence application of oxyfluorfen @0.15 kg ha-1 fb application of penoxulam + cyhalofop-butyl @ 0.135kg ha-1 at 25 DAS (w3), preemergence application of pyrazosulfuron-ethyl @ 0.025 kg ha-1 fb application of fenoxaprop-pethyl @ 0.06 kg ha-1 at 25 DAS (w4), pre-emergence application of pyrazosulfuron-ethyl @ 0.025 kg ha-1 fb application of cyhalofop-butyl @ 0.135 kg ha-1 at 25 DAS (w5), pre-emergence application of pyrazosulfuron-ethyl @ 0.025 kg ha-1 fb application of penoxulam + cyhalofopbutyl @ 0.135kg ha-1 at 25 DAS (w6), hand weeding at 20 and 40 DAS (w7), no weeding (weedy check) (w8). The variety used was Prathyasa (MO-21) released from Rice Research Station, Moncompu. FYM @ 5 t ha-1, N: P: K @ 90:30:45 kg ha-1 and lime 1.5 t ha-1 were applied uniformly to all treatments.The predominant weed flora of the experimental field was grass weeds followed by broadleaved weeds and sedges. Among the grass weeds, Setaria barbata was the dominant one. Stale seed bed recorded significantly lower density and dry weight at all stages of observations. At 15 and 30 DAS, lower absolute density, relative density and weed dry weight were recorded in w3. At 45 DAS, total dry weight and absolute density were lower in w1, w2, w3 and w7. Higher weed control efficiency (WCE) was observed in w2 (91.76%) at 15 DAS, w3 (97.34%) at 30 DAS and w7 (95.52%) at 45 DAS. Among interactions, s1w1 and s2w3 recorded higher WCE. The weed index in w3 was negative (-0.32%), indicating that w3 was superior than hand weeding (w7). The growth attributes viz., plant height, number of tillers, dry matter production and physiological parameters (CGR, RGR, total chlorophyll content) were significantly influenced by seed bed preparation and weed management practices at all growth stages. Stale seed bed method had the tallest plants and higher number of tillers during all growth stages. At harvest, tallest plants and higher number of tillers were observed in w3 (oxyfluorfen fb penoxsulam + cyhalofop butyl). The treatments w1 and w2 showed slight phytotoxicity on rice seedlings. Stale seed bed positively influenced the yield attributes of upland rice viz., number of panicles per m2, number of spikelets per panicles, percent filled grains, panicle weight, grain weight, grain yield, straw yield and harvest index. Among the weed management methods, w3 recorded higher values for all the above yield attributes except harvest index and number of panicle m-2. The grain yield was significantly affected by weed management strategies with w3 recorded higher grain yield (2.91 t ha-1) which was on par with w1, w2 and w7. Stale seed bed preparation had higher dehydrogenase enzyme activity, organic carbon, P and K status after the experiment. Among the weed management treatments, the dehydrogenase activity was higher in w3. Available N and K status of the soil were also influenced by weed management practices with weedy check recording lower values. Weedy check recorded the highest NPK uptake by weeds. Leaf folder and rice bug infestation were controlled by appropriate control measures. he highest BC ratio was observed with w3, which was on par with w1. Net returns was higher in w3 which was on par with w1 and w2. Weedy check (w8) recorded lower net returns. From the experimental results it can be concluded that, adoption of stale seed bed method along with pre-emergence application of oxyfluorfen @ 0.15 kg ha-1 at 0-3 DAS followed by either the application of penoxsulam + cyhalofop butyl @ 0.135kg ha-1 or fenoxaprop-p-ethyl @ 0.06 kg ha-1 at 25 DAS can be recommended as a viable cost-effective weed management option for the management of Setaria barbata in upland rice.