Effect of Summer Crops and their Residue Management on Yield of Succeeding Wheat and Soil Properties

The effect of summer crops and their residue incorporation on succeeding wheat crop and soil properties was studied in field conditions for two consecutive years on silty clay loam Typic Hapludoll. Soybean-wheat sequence recorded the highest grain and straw yields of wheat as well as organic C, available N and K, dehydrogenase activity and counts of fungi in soil, while pigeon pea-wheat sequence gave the maximum available P and microbial biomass C (MBC) after two crop cycles. Wheat grain yield, organic C and available N, P and K, MBC and dehydogenase enzyme activity in soil under different legume-based sequences were significantly higher than under cereal-based sequences, but no significant variations were observed in microbial counts. Legumes-based sequences also resulted in more organic C and available P and K in soil compared to their content at initiation of the study, while all the crop sequences improved microbial biomass C and dehydrogenase activity in the soil. Different crop sequences, except rice-wheat, also improved the counts of bacteria, fungi and actinomycetes in soil. Mean grain and straw yields of wheat for two years and organic C, available N and P in soil at the end following residue incorporation were significantly higher over removal, by 6.6, 4.4, 3.4, 7.2 and 7.8%, respectively. It also increased the microbial population and MBC by 10.2%, and dehydogenase activity by 10.2%, in the soil after harvest of 2^nd wheat crop. Increasing fertilizer levels did not increase the mean grain and straw yields; however, application of 100% recommended NPK recorded significant improvement in available K and MBC and 125% NPK in mean grain and straw yields and dehydrogensae activity and population of bacteria and fungi in soil over 75% NPK level. Soybean-wheat sequence produced the highest wheat yield, organic C, available N and K in soil and various soil biological properties. Irrespective of summer crops, their residue incorporation improved the yield of succeeding wheat and soil properties.