Agregação do solo sob os efeitos da reaplicação de corretivos da acidez e de gesso agrícola em plantio direto

Abstract

The soil acidity has as its main factor the limitation in plant development in agricultural production in several sectors of the world. The general objective of this study was to evaluate the reapplication of soil acidity correctives, ground rock limestone (CRM), ground rock silicate (SRM) and calcined limestone (CC), associated or not with agricultural gypsum (GA) on soil aggregation in no-till farming system (SPD). The present study was conducted in the experimental area of the ABC Foundation Experimental Demonstration Field (EDC), in the city of Ponta Grossa-PR, LATOSSOLO VERMELHO-AMARELO Distrófico de textura argilo-arenosa. The treatments were the three soil acidity correctors CRM (4,8 Mg ha-1), SRM (15,4 Mg ha-1) and CC (3,4 Mg ha-1) plus a control treatment (no acidity correction), associated or not with agricultural gypsum (GA) (3,0 Mg ha-1). Unformed soil samples were collected in May 2021 (i) monoliths, in the layers 0 – 0,05; 0,05 – 010 and 0,10 – 0,20 m, for evaluation of aggregation and aggregate stability. Deformed samples were collected in layers 0 – 0,05; 0,05 – 0,10; 0,10 – 0.20; 0,20 – 0,40 and 0,40 – 0,60 m for determination of soil acidity components (pH, H+Al and Al3+), basic exchangeable cations (Ca2+, Mg2+ and K+) and labile carbon (COX-P) and organic carbon (CO) contents. The effect of reapplication of acidity correctives was more effective, increasing labile carbon content in the soil considering a 0 – 0,20 m layer. In the 0 – 0,05 m layer, labile carbon contents remained stable. The limestones when applied alone increased the availability of organic carbon in the soil. The reapplication of the acidity correctives and agricultural gypsum resulted in the reduction of the microaggregates class. The large, medium and small MAgg classes correlated with exchangeable acidity (Al3+) of the soil. On the other hand, microaggregates correlated with active acidity (pH), potential (H+Al) and with Mg2+. The correctives increased DMP and large MAgg in the 0 – 0,05 m layer. The effect of reapplication of the correctives and agricultural gypsum on soil acidity will be more evident at longer term of application, requiring further evaluation. The combination of ground rock limestone and calcined limestone with gypsum promoted better pH correction (active acidity) on the surface (0 – 0,20 m). Besides showing a positive effect (without or with gypsum) of gypsum on Ca2+ availability at the surface. Aggregate classes are strongly linked to soil chemical components and cations and soil organic carbon. The large MAgg class (macroaggregates) increases according to the application of acidity correctives without gypsum application.