Sustainable weed management in transplanted rice

The Field experiments were conducted to study the influence of off-season land management in combination with various rice weed control measures on the weed competition and yield of rice in two different locations in late samba rice (September 2002 – January 2003) with the rice cultivar of CO 43. The experiments were taken up in a split-plot design with the main-treatments comprising off-season land management practices viz., ploughing the land twice at an interval of 45 days in off-season and raising a green manure in the off-season and ploughing in situ during land preparation, which were compared with an untreated fallow during off-season. Weed control and cultural measured taken up during the rice cropping period viz., hand weeding twice (at 20 and 40 days after transplanting), butachlor @1.25 kg ha-1, pendimethalin @1.5 kg ha-1, butachlor @1.25 kg ha-1 + 2, 4-D @1.0 kg ha-1 (tank mix), pendimethalin @1.5 kg ha-1 + 2,4-D @ 1.0 kg ha-1 (tank mix) as pre-emergent application were compared with unweeded control as sub-treatments. Among the off-season land management practices, off-season ploughing (twice at an interval of 45days) excelled the other treatments by recording least weed count and weed dry matter production DMP (in location 1 and Location 2) and higher weed control index (in location 1 and location 2) favouring higher yield attributes and grain yield (4.38 t ha-1 in location 1 and 4.47 t ha-1 in location 2), which was comparable with raising green manure in the preceding off-season and incorporating it just before preparing the land. Leaving the land fallow during the preceding off-season encouraged the highest weed count and weed DMP and recorded lowest weed control index resulting in poor yield attributes and grain yield. Among the rice weed control measures, hand weeding twice at 20 and 40 DAT recorded the lowest weed count and weed DMP (in location 1 and location 2) with higher weed control index (in location 1 and location 2) favouring higher yield attributes and grain yield (5.20 t ha-1 in location 1 and 5.27 t ha-1 in location 2). This was on par with pre emergence application of butachlor @ 1.25 kg ha-1 + 2, 4-D @1.0 kg ha-1 (tank mix). These treatments were significantly superior than the rest of the treatments in reducing the weed infestation and ultimately increased grain yield. The unweeded controls recorded the highest weed count and weed DMP resulting in the lowest yield attributes and grain yield. Significant interaction effects between the main treatments and sub treatments were also observed.