Surface liming combined with the use of monoammonium phosphate and elemental sulphur in a no‐till wheat–soybean cropping system

Abstract Tropical and subtropical soils typically have high acidity and limited nutrient availability. Surface liming under no‐till systems ameliorates topsoil acidity in the short term, but it is generally slow to neutralize subsoil acidity. A field experiment was conducted in the period from 2016 to 2021 in Parana State, Brazil, on a loamy, kaolinitic, thermic Typic Hapludox to evaluate the effects of surface application of lime combined with the use of monoammonium phosphate (MAP) and elemental S on soil acidity, root growth, plant nutrition and grain yields of wheat ( Triticum aestivum L.) and soybean ( Glycine max. [L.] Merr.) under no‐till. Treatments consisted of a control (no amendments), surface lime (SL), SL + MAP and SL + MAP + elemental S. Applying lime to the soil surface increased soil pH, exchangeable Ca 2+ and Mg 2+ contents and base saturation, as well as reducing Al 3+ content and Al 3+ saturation throughout the soil profile. Such effects were more pronounced in the 0–10 cm layer and occurred to a lesser extent in the 10–100 cm layers. The addition of MAP or MAP + elemental S did not improve the effectiveness of surface liming in alleviating soil acidity throughout the soil profile. The root length per soil surface area to a depth of 100 cm exhibited a strong correlation with wheat yield, but not with soybean yield. Surface liming increased wheat yield by 40% and when lime application was combined with MAP + elemental S, the increase in wheat yield reached 74%. Surface liming resulted in a 36% increase in soybean yield, regardless of the use of MAP and elemental S. Thus, surface application of lime was effective in reducing soil acidity to a 100‐cm depth, regardless of fertilizer application with MAP and MAP + elemental S. The improving effects of surface liming had a more favourable impact on wheat root growth than on soybean root growth, probably because wheat was more affected than soybean by insufficient rainfall during the crop development cycle. Wheat showed a greater yield response to P and S fertilizer application than soybean.