Least-limiting water range of the soil seedbed submitted to mechanical and biological chiselling under no-till

Abstract

Physical quality of the soil seedbed affects germination, seedling emergence and crop establishment. The aim of this work was to determine the least-limiting water range (LLWR) of a soil seedbed cultivated for 18 consecutive years under no-till (NT) and submitted to mechanical chiselling (NT-M) and biological chiselling by a forage radish cover crop (NT-B). The study was carried out in Ponta Grossa, Paraná, Brazil. The experimental design was randomised complete blocks with four replications. Soil samples at 0–5 and 5–10 cm depths were collected at 6 and 18 months after the start of the experiment which corresponded to maize (October 2009) and soybean (November 2010) planting. Water-retention curve, penetration-resistance curve, soil and relative bulk density, and LLWR were determined. Bulk density did not differ among treatments at 0–5 cm depth for both evaluation periods. At 5–10 cm soil depth, the NT-M treatment showed the lowest bulk density at the first sampling (2009), whereas NT-B showed the highest bulk density at the second sampling (2010). Soil penetration resistance was the most limiting factor of the LLWR, which was greater in NT-M for both soil layers at the first sampling. At the second sampling, the NT treatment had the greatest LLWR at 0–5 cm, but at 5–10 cm soil depth, both NT and NT-M had higher LLWR than NT-B. The efficiency of mechanical chiselling in improving soil seedbed physical quality lasted 18 months after its application. Biological chiselling was efficient in improving soil air-filled porosity in both periods as evaluated by the LLWR.