Comparative assessment of the relative proportion of weed morphology, diversity, and growth under new generation tillage and crop establishment techniques in rice-based cropping systems

A study was conducted in a cropping system mode for rice-wheat (RW) and rice-maize (RM) with crop residue management [without residue (R-) and with residue (R+)] under different tillage and crop establishment (T&CE) techniques. The T&CE techniques comprised conventional tillage (CT) puddled transplanted rice followed by (fb) CT wheat/maize (CTTPR-CT), unpuddled transplanted rice fb zero-tillage (ZT) wheat/maize (UPTPR-ZT), ZT-transplanted rice fb ZT wheat/maize (ZTTPR-ZT), and ZT dry-seeded rice fb ZT wheat/maize (ZTDSR-ZT). Results after four years revealed that the relative dominance of weeds followed the sequence of Echinochloa colona > Cyperus iria > Caesulia axillaris > Alternanthera philoxeroides > Ammannia baccifera in the rainy season, whereas for the winter season, the sequence was Medicago denticulata > Rumex dentatus > Phalaris minor > Chenopodium murale > Cyperus rotundus, irrespective of the treatments. In the rainy season of 2013, the highest total weed density was recorded in ZTDSR-ZT, which was 43.8%, 56.8%, and 46.7% higher than those in CTTPR-CT, UPTPR-ZT, and ZTTPR-ZT, respectively. However, in 2014, the highest total weed density, which was significant, was recorded in ZTTPR-ZT. The R+ treatment decreased the total narrow-leaved weed density by 7.3% compared to that in the R-treatment in 2014. In the winter season of 2013-14, the sequence of total weed density was ZTTPR-ZT > ZTDSR-ZT > UPTPR-ZT > CTTPR-CT, whereas during 2014-15, the sequence was UPTPR-ZT > ZTTPR-ZT > ZTDSR-ZT > CTTPR-CT. The P. minor density in the RW system was 86.7% and 16.2% higher in 2013 and 2014, respectively, than that in the RM system (P < 0.05). Narrow-leaved weeds represented >65% of the total weed density in ZTDSR-ZT during the rainy season, whereas in the winter season, broad-leaved weeds represented >90% of the total weed density in both years irrespective of the treatments. Shifting from CTTPR-CT to UPTPR-ZT and ZTDSR-ZT systems resulted in significantly higher Shannon, evenness, and richness indices, thus indicating that the reduction in tillage intensity increased the weed diversity. However, the ecological dominance (C) was higher in CTTPR-CT (0.234) than in the remaining T&CE practices. The contribution of narrow-leaved and broad-leaved weeds toward total weed biomass became pronounced in the UPTPR-ZT, ZTDSR-ZT, and ZTTPR-ZT compared to the CTTPR-CT. The intensity of the total weed density was diminished in the ZTTPR-ZT and ZTDSR-ZT during 2014-15 compared to that during 2013-14. The results of the study can contribute to the development of effective weed management strategies under changing tillage regime for higher crop productivity.