Effect of straw management techniques and herbicides on soil microbes in wheat in rice-wheat system

The effect of herbicides on microbial population of soil as influenced by shaw management techniques in wheat was studied in rice-wheat system in IGP at Ludhiana. The experiment was laidout in strip plot design with shaw management techniques of wheat in horizontal plots and herbicides in vertical plots. The different shaw management techniques were zem till sowing with Happy Seeder (combine harvested), zem till sowing in standing stubbles (loose shaw removed), Zem till sowing (complete burning of rice shaw), bed sowing (Rice shaw removed), conventional tillage (partial bwning of rice straw). The weed control treatments were sulfosulfumn 25 g/ha, mesosulfuron + iodosulfuron 12 g/ha and pinoxaden 50 g/ha and unsprayed (control). Microbial counts were recorded in the soil samples taken at 0, 15, 30 and 60 days after spray. The highest population of bacteria, actinomycetes and fungi was observed under zem till sowing with Happy Seeder which was statistically at par with zero till sowing in standing stubbles followed by bed planting and significantly higher than zem till sowing after burning and conventional tillage after partial burning under all observational period. Similarly, the highest microbial population was observed in control plots as compared to those in herbicidal treatments. There was decrease in viable counts of bacteria, actinomycetes and fungi at 15 days after spray as compared to that at zem day after spray. Thereafter, the microbial population slarted to regain and an increase was observed in counts, indicating reduced toxicity, probably due to degradation of herbicidal chemicals.