Soil acidity correction and fertilization strategies: Effects on acidity, nutrient availability, and crop yield

High soil acidity and low nutrient availability in the deeper soil layers of no-tillage systems (NTS) can restrict crop yield potential. This study aimed to evaluate the impact of different soil acidity correction strategies and P and K application methods on the vertical variation of soil acidity, nutrient availability, and on corn and soybean yields. A randomized block factorial experiment was established in 2020 on a Plinthosol (Plintossolo Argilúvico Distrófico típico) under NTS since 2004. The first factor consisted of soil acidity correction strategies: (i) control, (ii) surface application of dolomitic limestone, (iii) surface application of calcium and magnesium oxide (CaO·MgO), and (iv) incorporation of dolomitic limestone to 0.20 m depth. The second factor corresponded to P and K application methods: (i) control without fertilization, (ii) in-furrow application, and (iii) surface broadcast application. The corrective amendment rates were calculated to raise the soil pH in the 0.00–0.20 m layer to 6.0. Six months after treatment application, soil samples were collected down to a depth of 0.40 m. Application of CaO·MgO increased soil pH, Ca²⁺+Mg²⁺+K⁺ saturation, and Ca²⁺ and Mg²⁺ contents, but these effects were confined to the surface soil layer (0.00–0.10 m). In contrast, limestone incorporation reduced soil pH, and Ca²⁺+Mg²⁺+K⁺ and Al³⁺ saturation gradients over a greatest soil depth (0.00–0.15 m), demonstrating greater effectiveness than both surface-applied limestone and CaO·MgO. Improvements in soil acidity resulting from limestone incorporation led to a 66 % increase in corn yield compared to other correction strategies. Soil chemical properties were minimally affected by P and K application methods, with higher available P observed only in the 0.00–0.05 m layer under surface broadcast application. Nevertheless, in-furrow P and K fertilization increased corn yield by 35 % compared to surface application. Soybean yield was not influenced by any of the treatments. In soils with high subsurface acidity, incorporating soil amendments is essential for effective acidity correction and yield improvement, while in-furrow P and K fertilization remains an efficient strategy to sustain high crop yields.

Keywords
calcium and magnesium oxide; dolomitic limestone; no-tillage; corn; soybean