Long-term impact of crop establishment methods on weed dynamics, water use and productivity in rice-wheat cropping system

Abstract

An experiment consisting of five establishment techniques in rice-wheat cropping sequence with different combinations of conventional tillage (CT), zero-tillage (ZT) and minimum tillage (MT) viz. CT-CT, ZT-CT, CT-ZT, ZT-ZT and MT-ZT) was conducted during 2003–2007 at the farm of a farmer in Haryana on a larger plot size of 0.4 ha under each treatment. During first year, grain yield of wheat did not differ significantly among different treatments but during 2004–05 to 2007–08, grain yield of wheat in ZT method of planting was either higher or at par with conventional ploughed method of planting but CT transplanting of rice was significantly more than ZT transplanted treatments except during first year when rains were very good at transplanting time. Weed dynamics after 4 years revealed that in rice crop, weed density of Echinochloa colona, E. crusgalli, Leptochloa chinensis, Cyperus spp. and broad-leaf weeds such as Ammania baccifera and Eclipta alba was more when rice was transplanted under ZT or MT conditions but in wheat, weed density of grassy weed Phalaris minor was less under ZT-ZT or MT-ZT treatments. After 4 years of continuous ZT in both rice and wheat crops, weed flora changed in favour of broad-leaf weeds. Bulk density of soil did not vary after 5 years of ZT-ZT conditions. Soil temperature of root zone in wheat crop planted under ZT conditions was more (0.7–1.7 OC) in first week of February and less (2.1-.3.8 OC) in first week of April as compared to conventional CT-CT practice of rice and wheat crops resulting in more grain yield of wheat due to temperature moderation and also due to a bit addition of organic matter in ZT conditions. Grain yield of rice planted under ZT or MT conditions was less mostly due to more weed infestation and it also consumed 4.8–184% more water as compared to CT method of puddle transplanted rice.