Soil microbiological and chemical changes in rice-wheat cropping system at Palampur (Himachal Pradesh) after twelve years of Lantana camara L. residue incorporation

Long term effects of lantana (Lantana camera L.) residue incorporation on major soil microbes and on certain soil chemical properties in the rice-wheat cropping system were studied at Palampur (Himachal Pradesh) in an experiment that started in 1988 with four levels of lantana incorporation (0, 10, 20, 30 Mg.ha–1 on fresh weight basis) and three tillage practices (no puddling, puddling, and soil campaction). The tillage practices, however, were replaced with three levels of N and K (33, 66, and 100% of the recommended 90 and 40 kg.ha–1 N and K respectively) to rice from 1997 onwards. N, P and K application to wheat was at 66% of the recommended dose (120, 90, and 30 kg.ha–1). After 12 crop cycles (2001–’02), lantana residue application at 10, 20, and 30 Mg.ha–1 increased soil organic carbon (7, 13, and 19% over 1.29 g C kg–1 under no residue treatment) and pH (5.23 to 5.29 as against 5.12 in the control). Lantana incorporation at 10 to 30 kg.ha–1 also recorded a significant increase in the bacterial (249 to 369 104 CFU), fungal (148 to 220 104 CFU), actinomycetes (79 to 144 104 CFU), and phosphorus solublizing microorganism (53 to 100 104 CFU) counts (0 to 0.15 m soil depth) compared to control. The most important variable contributing to rice and wheat yield was soil organic carbon (R2= 86 to 95%), followed by bacteria and fungi