Estabilidade de agregados do solo e carbono orgânico em sistema de integração lavoura-pecuária-floresta no agreste paraibano

Abstract

In the Brazilian semi-arid region, natural limitations related to climate and soil characteristics, together with the predominant use of conventional agriculture, have intensified soil degradation processes. Given this scenario, conservationist production systems have been adopted. Thus, the objective was to evaluate soil aggregate stability and organic carbon content in an integrated agriculture-livestock-forestry system in the Agreste region of Paraíba. The experiment was conducted in the EMPAER experimental area, in the municipality of Alagoinha/PB, on a Haplic Planosol with a moderate A horizon and sandy loam texture. Four mini trenches with a maximum depth of 30 cm were opened to collect three undisturbed soil samples (0-10; 10-20; 20-30 cm), for a total of 12 samples per land use system and 60 samples in the sampled area. The experiment used a randomized block design (RBD) with five systems and four replicates (5x4). The systems used were: T1) Urochloa decumbens + Gliricidia (Gliricidia sepium); T2) Urochloa decumbens + Sabiá (Mimosa caesalpiniifolia); T3) Urochloa decumbens; T4) Degraded pasture; and T5) Native vegetation. The integration systems promote improvements in aggregate distribution, both wet and dry, with macroaggregate percentages greater than 70% at depths of 0-10, 10-20, and 20-30 cm. The Urochloa decumbens + Gliricidia (Gliricidia sepium) (GC+UD), Urochloa decumbens + Sabiá (Mimosa caesalpiniifolia) (SB+UD) and Urochloa decumbens (UD) stood out for their significant contribution of total organic carbon, maintaining values above 10 g kg−1, with average organic matter values of 63.25; 63.84 and 65.75 g kg−1, in soil profiles at depths of 0- 30 cm, respectively. The most recommended among the integrated systems would be the Sábia + Urochloa decumbens system, as it has maintained satisfactory results in physical and structural soil improvement. The area of native vegetation showed marked physical structural fragility when the soil was subjected to moistening. This structural loss is considered harmful to the soil as it can promote erosion processes. The crop-livestock-forest integration systems showed improvements in the physical structure of the soil and in the supply of organic carbon, with greater effects on the soil surface.

Keywords:soil characteristics; aggregation of planosol; semi-arid.