Managing soil acidity and carbon emission in crop systems

Abstract

Liming is essential for achieving high crop yields in tropical acidic soils, but lime dissolution releases CO ₂ , whereas silicate slag does not, while gypsum improves subsoil fertility. Although the benefits of these amendments for soil fertility are well known, their combined effects on CO ₂ emissions and soil carbon (C) accumulation in cropping systems remain unclear. We evaluated the effects of lime and silicate applied alone or in combination with gypsum, in a soybean ( Glycine max L.) double‐cropped with maize ( Zea mays L.) intercropped with Urochloa ruziziensis system under no‐till (NT) and conventional tillage (CT), in two side‐by‐side field experiments. The experiments were conducted on a Typic Haplorthox in Southwestern Brazil over 2 years. Treatments included (i) lime, (ii) silicate slag, (iii) lime + gypsum, (iv) silicate slag + gypsum, and (v) control. Root and shoot dry matter, plant carbon (C) input, CO ₂ emissions, and soil C stocks were measured in the second‐year soybean season. The application of soil amendments increased shoot and root dry matter and C inputs under NT and CT but did not alter total C stocks across the soil profile. Cumulative CO ₂ emissions were not affected by soil amendments under NT; however, emissions increased with lime + gypsum under CT. Alleviating soil acidity in tropical cropping systems through the application of lime, silicate, and their combination with gypsum can enhance crop yields while reducing yield‐scaled (normalized) CO ₂ emissions.