Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore-641 003.
Conservation tillage decreases soil erosion, leaching of fertilizer, pesticides and herbicides into the ground water. Conservation and conventional tillage greatly affect bulk density and soil aggregation. Conservation tillage improves activity of earth worm and other soil micro flora. Some studies showed that soil microbial activity was higher with conventional tillage due to better aeration. Numerous studies conducted in temperate climate zones showed that no-tillage resulted in acidification of surface layer when continued for several years compared to conventional tillage. Conservation tillage increases soil infiltration rate and reduces soil evaporation there by it increases soil water storage, while other studies stated that soil crusting at aslower rate on no-till surface than onthe tilled reducing the infiltration rate. Due to higher residue in surface soil in conservation tillage, it will improve soil organic carbon content, while other work reported a decrease in soil organic matter compared to ploughed soil down to a depth of 10 cm after 3 years of study. Zero tillage gives smothering effect to weeds but some studies shows that, higher density of perennial grass weeds in reduced tillage systems compared to conventional tillage. Several studies have shown that crops grown under zero tillage have yielded as similar as or better than those grown under conventional tillage, while some workers revealed conventional tillage increased the yield of crops and other scientist reported there no yield difference between any tillage system.
