Bio-efficacy of pretilachlor with varying irrigation regimes in furrow transplanted and furrow irrigated rice (Oryza sativa L.) in Punjab.

Rice (Oryza sativa L.) is the most important staple food of India contributing 45 % of the total food grain production. Rice is the highest waterrequiring crop in the kharif season. To economize irrigation water, the concept of reduced water supply per irrigation through furrow irrigated rows and bed or furrow transplanted rice was evaluated for its effect on rice productivity and irrigation water savings. These studies revealed 30 to 40 per cent saving in irrigation. Paddy yields were either statistically same or slightly reduced particularly in years when the rains were about 50 % below normal (Mahey et al, 2003; Kaur, 2004). However, in these studies the authors reported severe problem of weeds because of comparatively unsaturated conditions on the raised portion of beds where even if herbicide is applied, its activity is reduced and also prevalence of oxygenated conditions favoured the growth of both narrow and broadleaf weeds. Thus, once again the physiological basis of Echinochloa seed germination and its control with herbicides’ use under just saturation conditions were thought of, as has been the case in flat puddled transplanted rice (Sandhu et al., 1992) with the hypothesis that even if some water saving is sacrificed to maintain the saturated conditions on the raised portion of bed by just inundating them while applying irrigation water during the first two weeks after transplanting to get optimum control of weeds through herbicide even then a saving of about 50-60 cm (20-25%) in irrigation water can be achieved by furrow/bed transplanting system over conventional method. Thus keeping in the view the physiology of Echinochloa seed germination and its control with herbicide use under saturated conditions the present investigation was undertaken to evaluate the effect of furrow and bed transplanting and varying irrigation management on crop growth and crop-weed competition. The field investigation was carried out at student’s farm, Punjab Agricultural University, Ludhiana (30 0 56’ N latitude with 75 0 52' E longitude, 247 m mean sea level). The soil of the experimental field was sandy loam, low in organic carbon (0.27 and 0.21 %) and available N (210 and 182 kg ha -1 ) and medium in available P (18.9 and 17.8 kg ha -1 ) and K (185 and 140 kg ha) in 0-15 and 15-30 cm soil depth, respectively. The soil reaction (pH) and electrical conductivity were in the normal range. The experiment was laid out in a randomized block design with four replications. The experiment comprising of 14 treatment combinations from seven planting methods × (irrigation treatments) viz. (i) Transplanting puddled flat × (Border method of irrigation) [Flat (BM)]; (ii) Transplanting 2 rows/furrow × (Irrigation inundating beds during establishment phase and in furrows thereafter) [2R/F (Inun. B+F)]; (iii) Transplanting 2 rows/bed × (Irrigation inundating beds during establishment phase and in furrows thereafter) [2R/B (Inun. B+F)]; (iv) Transplanting 2 rows/furrow × (Irrigation inundating beds throughout after transplanting) [2R/F (Inun. B)]; (v) Transplanting 2 rows/bed × (Irrigation inundating beds throughout after transplanting) [2R/B (Inun. B)]; (vi) Transplanting 2 rows/furrow × (Irrigation in furrows throughout after transplanting) [2R/F (F)]; (vii) Transplanting 2 rows/bed × (Irrigation in furrows throughout after transplanting) [2R/B (F)] and two weed control treatments i.e. (i) Unweeded control [UWC] (ii) Use of pretilachlor @ 0.75 kg ha -1 and metsulfuron @ 0.015 kg ha -1