Sampling layer for soil fertility evaluation in long-term no-tillage systems

Abstract

In no-tillage (NT) systems, there is no plowed layer since the soil is not tilled. Thus, the soil layer for fertility evaluation can be defined as the one in which the fertility indices are affected by the surface application of lime and fertilizers and soil properties have the closest relationship with crop yields. The objective of this study was to determine the most appropriate soil layer under long-term NT for sampling for fertility evaluation in the South-Central region of Paraná, Brazil. A total of 99 field experiments of crop rotations were performed, including soybean, corn, barley, wheat, and white oat, all on Oxisols (Hapludox). Despite the surface application, lime and fertilizers increased base saturation (V) and available K to a depth of 0.20 m. The relationship with crop yields was high for V and low for available K for both soil layers (0.00-0.10 and 0.00-0.20 m); for P, however, the relationships with soybean and corn yields were strongest in the 0.00-0.20 m layer. Thus, considering the soil layer fertilized by the surface application of lime and potassium fertilizers and the highest relationship of soil P contents with the yield of the main crops of the crop rotation, the 0.00-0.20 m layer is the most appropriate for soil fertility evaluation under long-term no-tillage systems.