Effect of pre-planting tillage on crop yields and weed biomass in a rice-wheat system on a sandy loam soil in Punjab

In rice (Oryza sativa L.) culture the effect of puddling (wet tillage) on p uddle quality, weed growth and yield of crop depends upon initial soil mani pulations by pre-puddling tillage. However, the role of pre-puddling tillag e on these aspects has not been studied adequately. These effects were stud ied for three years (1994-1996) in a field experiment with a rice-wheat (Tr iticum aestivum L.) cropping system at Punjab Agricultural University, Ludh iana. Treatments included pre-puddling tillage treatments no tillage (PT0), one discing one harrowing (PT2) and one discing and three harrowings (PT4) ) in rice in combination with four tillage systems, varying in depth and in tensity of soil disruption in wheat on puddle quality, weed growth and yiel d of rice and wheat on a sandy loam soil (Dystric Cambisol). Pre-puddling t illage improved puddle quality in terms of increased puddle depth and tende d to decrease percolation rate. Weed infestation in rice decreased with inc rease in intensity of pre-puddling tillage. Mean dry weed biomass 35-40 day s after transplanting was 1.6 Mg ha(-1) in PT0, 0.6 Mg ha(-1) in PT2 and 0. 5 Mg ha(-1) in PT4. Leaving some area untilled between rows (strip tillage) in wheat resulted in a larger weed biomass in rice, than with inversion of soil. Pre-puddling tillage did not affect rice yield during the first two years but significantly increased it during the third year when rice yield was 4.1 Mg ha(-1) in PT0 compared with 5.8 Mg ha(-1) in PT2 and 6.1 Mg ha(- 1) in PT4. Manual weeding at 40 days after transplanting masked the effect of pre-puddling tillage on rice yield. In general, rice yield decreased exp onentially with increase in weed biomass recorded at harvest of the rice cr op. Pre-puddling tillage did not affect wheat yield significantly. The resu lts suggest that for effective weed control, high rice yield and water use efficiency, the field must receive pre-puddling tillage at least once. (C) 1999 Elsevier Science B.V. All rights reserved.