Long‐term no‐tillage increases soil organic matter and cation exchange capacity, but reduces P and K, in irrigated rice

Abstract

Brazil is one of the main countries in the adoption of no tillage (NT) in highlands, however, in lowlands, under irrigated rice cultivation, the adoption of this important soil management is incipient (<5%). Thus, the objective of this work was to evaluate the dynamics of soil chemical attributes under long‐term NT and rice cultivation. Throughout the field trial, irrigated rice monoculture prevailed continuously in succession with ryegrass prevailed for 23 years, under the adoption of different management systems, conventional tillage (CT), pre‐germinated (PG) and NT in an soil Albaqualf (soil under hydromorphic condition) under a randomized block design with three replications. Active acidity, potential acidity, soil organic matter, cation exchange capacity (CEC), phosphorus, potassium, calcium and magnesium were evaluated in the stratified profile at depths: superficial (0–10 cm), intermediate (10–20 cm) and deep (20–40 cm). An increase in the potential acidity of the soil in the NT was observed in the surface layer, an increase in organic matter and in the exchangeable forms of calcium and magnesium. However, there was a reduction in the availability of phosphorus by 20% and potassium by 32% in the topsoil in the NT compared with PG and NT. NT is a soil conservation system that increases organic matter and CEC levels. However, strategies aimed at improving the availability of phosphorus and potassium under NT in paddy fields must be used not to reduce the productive potential of rice grains.