Estimativa de calagem pelo método SMP em solos do sul do Amazonas

Abstract

Acidity is the main factor of soil chemical degradation and covers extensive areas of temperate zones and the tropics. Liming is the most common management practice as it reduces aluminum toxicity and improves the root environment. The SMP method is based on the soil's buffering power, determining greater amounts of corrective as the soil acidity levels increase. This work aimed to evaluate a liming recommendation method for acidity correction in soils under natural grasslands, in Humaitá, AM. For the installation of the experiment of incubation of soils with limestone, 8 soils were selected under the domain of natural fields in the municipality of Humaitá-AM, south of the state of Amazonas. These were collected at a depth of 0 – 20 cm. The incubation curve experiment was carried out in the UFAM shed, Humaitá campus, where the collected soils were crushed and passed through sieves with 4.0 mm mesh openings. Subsequently, samples with 1 kg of air-dried soil were separated and placed in plastic bags with a capacity of 5 kg, without drainage pores. Soils were incubated at doses corresponding to 0.0; 1.0; 2.0; 4.0; 6.0; 8.0 and 10.0 t ha-1 of limestone were used as a mixture of calcium carbonate and magnesium carbonate. Thus, treatments were followed, resulting from 8 types of soils under 7 different doses of limestone with 3 replications, totaling 168 experimental units. The results of the experiment were submitted to analysis of variance by the F test at 5% probability. Subsequently, the pH results in water were plotted graphically in relation to limestone rates and adjusted to polynomial regression models. Regarding the effect between soils requiring limestone, it appears that the soils of Field 7 (C7) and Field 6 (C6) require a greater amount of limestone in relation to the others to reach a certain pH value, respectively. The positive relationship between the SMP pH of the soils and the liming requirement of all the grouped soils was similar to that observed in the individual soils. There was a significant effect between soil SMP pH and the need for liming to obtain pH 5.5; 6.0 and 6.5 by the incubation curve, with the data fitting to a linear model.