Effects of long-term tillage systems on soil physical quality and crop yield in a Brazilian Ferralsol

Abstract

Long-term soil tillage trials can provide important knowledge about sustainable changes in soil physical quality and crop yield. This study evaluated soil physical quality indicators under different long-term tillage systems and examined the relationships between quality indicators and crop yield. The study was carried out on a Rhodic Ferralsol with three tillage systems established in 1989: conventional tillage (CT), strategic tillage (ST), and no-tillage (NT). All treatments had long-term crop rotation. The soil parameters evaluated were total organic carbon (TOC), bulk density (ρs), macro and microporosity (Mac and Mic), relative gas diffusivity (D/D0), pore tortuosity (τ), relative field capacity (RFC), structural stability index (SSI), least-limiting water range (LLWR), and degree of compactness (DC, taking as reference the soil bulk density in which LLWR = 0). Soybean and maize yields in two consecutive summer seasons were measured. Conventional and strategic tillage provided higher ρs in the 0.15–0.30 m layer depth, leading to higher DC in CT. Using soil bulk density at LLWR = 0 as reference proved useful to assess soil DC and plant response. No-tillage provided lower DC in the 0–0.15 m (86 %) and 0.15–0.30 m (78 %) layers than CT (91 % and 94 %, respectively). The maize yield had a negative linear relationship to DC, with the lower values at DC > 87 %. All tillage systems affected D/D0, even at similar porosity values. The better soil physical quality under NT provided 1211 kg ha−1 higher maize yield compared with CT. The differences in soybean yield between treatments were not significant, but NT provided 381 kg ha−1 more than CT. These findings indicate that NT is the best system studied. Our results strongly suggest that ST does not improve physical properties of soils under NT with crop rotation, and that a diversified crop rotation in NT was efficient to avoid soil physical degradation.