Soil properties under different supplementary organic fertilizers in a restoration site after kaolin mining in the Eastern Amazon

Abstract

Mining is one of the economic activities that most degrade ecosystems, and the rehabilitation of such environments in the Brazilian Amazon is still a challenge. The first step is to recover the soil quality for plant reestablishment. In this study was evaluated the effect of different organic fertilizers, supplementary to chemical fertilizers, on the physical and chemical attributes of a minesoil after kaolin mining in the Eastern Amazon, Brazil. Nine trenches measuring 1 m × 40 m and 1 m in depth were opened in a reconstructed area after kaolin mining. They were 6 m apart from each other and filled with topsoil from areas destined for new mine pits. Then 40 cm × 40 cm × 40 cm pits were opened along the trenches. They were 1.5 m apart from each other within each trench, and 400 g pit−1 of simple superphosphate, 130 g pit−1 of urea and 130 g pit−1 of potassium chloride were applied in five treatments: three treatments along the trenches, in the planting rows with; i) addition of topsoil; ii) sawdust; iii) cattle manure, and two treatments between the planting rows; iv) sawdust; and v) without sawdust. Two hundred and fifty seedlings of six heliophilous tree species were planted, being randomly distributed. One hundred and forty-four disturbed (original structure altered) and 144 undisturbed (structure equal to the original soil) samples were collected for evaluation of the physical and chemical attributes of minesoil. Besides soil, other variables were assessed: plants abundance, height, diameter at breast height as well as litter stock. The treatments did not differ significantly in relation to the effects on abundance, height, diameter and litter stock, either in the planting rows or between them. The organic matter was higher in the Manure treatment at depths of 0.0–0.1 and 0.2–0.4 m. The sawdust coverage between trenches increased Ca and base saturation, but decreased N due to the high Carbon/Nitrogen ratio. Planting using trenches, topsoil, chemical and organic fertilization and sawdust coverage resulted in good physical and chemical properties of the soil and enabled greater efficiency in restoring the area mined for kaolin in the Amazon.