Fertilidade do Solo em Sistema Agroflorestal na Zona Litorânea Nordestina

Abstract

Technologies developed for industrial agriculture raised productivity, but generated environmental impacts, such as the decline in soil fertility. Need for agroecosystems with less environmental impact, Agroforestry Systems (AFS) are essential to promote soil recovery. However, the AFS promote the heterogeneity of soil attributes, and it is important to assess this factor to develop management strategies. In this work, the objective was to evaluate the soil fertility in AFS at Fazenda Coringa Agrofloresta (Trairi-CE). The experimental design was in randomized blocks, with four replications and a 2x4 factorial, totaling 32 experimental units. The treatment factors were two species (gliricidia - Gliricidia sepium and banana - Musa spp.), and four horizontal distances in relation to the canopy projection of the plants between the rows (10, 20, 30 and 40 cm). Soil collection was carried out with a sampling probe at a depth of 10 cm. The parameters taken from the soil were pHH2O, total nitrogen (N), phosphorus (P), Calcium (Ca), magnesium (Mg), potassium (K); sodium (Na), copper (Cu), iron (Fe), manganese (Mn), zinc (Zn); acidity potential (H+Al); aluminum (Al); organic matter (SOM); cation exchange capacity (T); base saturation (V%); aluminum saturation (m%); sum of bases (SB) and Exchangeable Sodium Percentage (ESP). An analysis of variance, Tukey test and regression analysis at 5% probability were performed. CO and SOM contents were very good in relation to the edaphoclimatic conditions of the semi-arid region, with a higher value for Musa spp. at 30 cm. The highest P content occurred for Musa spp. at 10 cm, while N was higher at 10 cm for G. sepium. Ca contents varied from low to medium and those of Mg between medium and high, being the smallest and largest contents at 40 cm for banana and gliricidia, respectively. Values of Na, K, H+Al and m% were low and SB and V% suggest adequate levels of exchangeable bases. Values of t and T corroborate the results of SOM, SB and V%, being higher the further away from gliricidia. Cu contents were high, Fe between medium and high and Zn were high. Higher levels of Cu and Fe occurred associated with banana. Soil chemical attributes were adequate to maintain fertility, considering that the agroforestry system is very young. Musa spp. seems to absorb more nutrients the greater the distance from the canopy projection, unlike G. sepium. Higher N contents close to gliricidia indicate effects of biological fixation on the rhizosphere. Further studies on the fertility of the AFS are essential to follow the evolution of the system and the accumulation of nutrients in the soil.