Enzyme dynamics in paddy soils of the rice district (NE Italy) under different cropping patterns

Recently, the widespread interest on soil enzymes is due to the need to develop sensitive indicators of soil quality that reflect the effects of land management on soil and assist land managers in promoting long-term sustainability of terrestrial ecosystems. The activities of six important enzymes involved in C, N, P, and S cycling were investigated in a paddy soil from the Veneto region, Italy, in four different rotation systems (rice-rice-rice, soya-rice-rice, fallow-rice and pea-soya-rice) with three replications in April (after field preparation, field moist condition), June (after seedling, waterlogged soil condition), August (after tillering stage of rice, waterlogged soil condition) and October (after rice harvesting, drained soil condition) over the 2012 growing season. Our results demonstrated that soil enzyme activities varied with rotation systems and growth stages in paddy field. Compared with field moist soil, drained soil condition resulted in a significant increase (P < 0.05) of β-glucosidase, arylsulfatase, alkaline and acid phosphatases, leucine aminopeptidase (except of F-R), and chitinase activities in all rotations, while compared with drained soil, waterlogging (in month of June, the early period of waterlogging) significantly decreased (P<0.05) β-glucosidase, alkaline and acid phosphatases, leucine aminopeptidase (except of P-S-R), arylsulfatase, chitinases. Soil organic-C was positively correlated with acid and alkaline phosphatases, and arylsulfatase while ß-glucosidase, chitinases and leucine aminopeptidase were not significantly correlated to soil organic-C. Enzyme activities were always correlated among them.