Limestone and gypsum reapplication in an oxisol under no-tillage promotes low soybean and corn yield increase under tropical conditions

Abstract

Limestone and gypsum combined use in no-tillage (NT) systems can favor soil acidity correction and improve nutrient availability in-depth with positive effects on crop production. There are still doubts about the necessity to restart the NT when the soil’s natural acidity was not corrected properly. The study evaluated i) the changes in the vertical distribution of nutrients and the acidity attributes in the soil solid phase, ii) the crop yields resulting from limestone reapplication strategies, associated or not with superficial gypsum application, and iii) the need to restart the NT system, with limestone incorporation to correct the re-acidification of an Oxisol in the Cerrado biome. Six treatments were evaluated, following the NT maintenance: i) no limestone reapplication and no gypsum application (NL), ii) superficial gypsum application (NL+), iii) superficial limestone reapplication (SL), and iv) superficial limestone reapplication and superficial gypsum application (SL+); or restarting the NT: v) limestone reapplication and incorporation (IL), and vi) limestone reapplication and incorporation followed by superficial gypsum application (IL+). Seven years after the experiment implementation, the soil was sampled in eight stratified layers down to the 50 cm depth in the experimental plots and under the Cerrado natural vegetation (CNV). The chemical attributes related to soil acidity, nutrient availability, and the soybean and corn yields were evaluated. The soil under CNV has lower pH and greater aluminum saturation (Alsat) than the NL treatment, whose natural potential acidity was corrected 36 years ago and remained without limestone reapplication for 11 years. Such results indicate that the soil re-acidification process is slow. Superficial limestone reapplication (SL and SL+) reduced soil Alsat down to 25 cm but did not neutralize it completely. Limestone incorporation (IL and IL+) had little effect on Alsat distribution in-depth when compared to superficial limestone application. Gypsum application increased Ca content and lead to Mg displacement in soil depth, but did not affect Al dynamics, nor the crop yields. The effects of limestone and gypsum reapplication on the soil surface under NT provided a greater nutrient accumulation in the soil superficial layer, especially Ca and Mg. Soybean showed a low but positive yield response to the limestone reapplication, regardless of the method (average yield increase of 252 kg ha−1 year−1), but corn yield was less affected. There is no need to incorporate the limestone neither to apply gypsum in agricultural lands that had their natural acidity corrected properly in the past.