Effect of tillage sequence and weed management on weed dynamics and productivity of dry-seeded rice (Oryza sativa)-wheat (Triticum aestivum) system

Abstract

A field experiment was conducted during 2006-07 to 2008-09 at Jabalpur to study the effect of four tillage se- quences [zero-till planting of both the crops (ZT-ZT), conventional planting in both the crops (CT-CT), and two ro- tational tillage sequences that altered between zero-till and conventional tillage (ZT-CT and CT-ZT)] and three weed control treatments (weedy check, herbicide alone, and herbicide + 1 hand weeding at 35 days after sowing) on weed dynamics, tillage economy and productivity of dry-seeded rice ( Oryza sativa L.)-wheat [( Triticum aestivum (L.) emend Fiori & Paol)] system on a clay-loam soil. Results revealed that continuous zero tillage in- creased the population density of Echinochloa colona (L.) Link (jungle rice) and Cyperus iria L. (rice flat sedge), the most dominant weeds of rice. In subsequent wheat crop, zero tillage reduced the population of Avena ludoviciana (L.) Dur. (wild oats) and Chenopodium album L. (common lambsquarters) but increased the density of Medicago hispida Gaertn. (burclover) as compared to other tillage systems. Rotational tillage systems had vari- able effects on weed density in rice and wheat. Pendimethalin (1.0 kg/ha) fb 2, 4-D (0.50 kg/ha) significantly re- duced the population density of E. colona, C. iria and Alternanthera sessilis (L.) D.C. (sessile joyweed) but failed to control Caesulia axillaris Roxb. (pink node flower) in rice. In subsequent wheat, clodinafop propargyl alone sig- nificantly reduced the population of A. ludoviciana, but M. hispida was unaffected even with integration of herbi- cide with 1 hand weeding. Continuous zero tillage yielded 25.1 and 15.4% higher grain yields of rice and wheat re- spectively, than that of conventional tillage regardless to weed control methods. Continuous zero tillage with rec- ommended herbicide + 1 hand weeding recorded the maximum net returns (`73.87 103/ha) and B: C ratio (3.81) in direct-seeded rice-wheat system.