Effect of Long-Term Conservation Tillage on Soil Physical Properties and Soil Health under Rice-Wheat Cropping System in Sub Tropical India

Abstract

Tillage influence soil aggregation, microbial activity in the soil and enhance the oxidation of soil organic carbon (SOC). A long term study was carried out to investigate the impact of conservation tillage on soil aggregates, SOC and microbial biomass carbon (MBC) in rice (Oryza sativa)-wheat (Triticum aestivum) cropping system at experimental station of Varanasi, Uttar Pradesh under the aegis of All India Co-ordinated Research Project (AICRP) of Integrated Farming Systems (IFS) during 2003-10. The four rice crop establishment techniques i.e., direct seeding in zero tilled soil (P1), wet seeding of sprouted rice seed with drum seeder in puddled condition (P2), manual transplanting in puddled soil (P3) and mechanical transplanting in puddled soil (P4) served as horizontal treatments while four tillage practices in wheat (i.e. T1-rotavator till drill, T2-conventional sowing, T3-strip till drilling, T4-Zero till drilling) served as vertical treatments in strip plot design with three replications. Total water stable aggregates (WSA)(> 0.053 mm) in the soil at surface 0-15 cm depth, ranged between 69.92 and 88.78 % in rice crop, while in winter crop it varied between 74.62 and 83.57 %. According to mean weight diameter (MWD) different treatments in regard to crop establishment technique of rice could be ranked in the order P1 > P4 > P2 > P3 and T4 > T3 > T1 > T2 in wheat strip regarding tillage practices. However, the MWD decreased drastically in lower soil depth. The SOC ranged from 4.06 to 5.67 g kg-1 in soil samples from rice plots and from 4.32 to 5.24 g kg-1 in different tillage treatments in wheat at surface 0-15 cm layer. SOC contents in direct seeding in zero tilled rice strip (5.67 g kg-1) and zero till drill in wheat strip (5.24 g kg-1) were significantly higher than other treatments in all soil depth. The MBC of direct drilling zero tilled (441 μg g-1) in rice strip and zero till drill in wheat strip (395 μg g-1) had the highest values while the manually transplanted-puddled (383 μg g-1) rice and conventional wheat sowing had the lowest values (334 μg g-1) at all the depths. The differences were significant in at P < 0.01 for both SOC and MBC and ranked in order of P1 > P2 > P4 > P3 of rice crop strip and T4 > T3 > T> T2 in wheat crop strip under 0-15 cm soil depth. The decrease in SOC an average all treatments was about 51 and 89 percent from layer 0-15 to 15-30 and 30-45 cm, respectively. The interaction effects of P at same level of T and T at same level of P treatments on MWD, SOC and MBC were significant (P < 0.01) in 0-15 and 15-30 cm soil depth.