Plant growth and metabolism of exotic and native crotalaria species to mineland rehabilitation in the Amazon.

Abstract

Despite its enormous benefits, mining activity is responsible for intense changes on vegetation and soil properties. Thus, after exploration, it is necessary to rehabilitate the mined areas creating better conditions to the establishment of plant species, especially native ones, which is still a challenge. This study aimed to evaluate mineral and organic fertilization on growth, carbon compounds and nitrogen (N) metabolism of two Crotalaria species [Crotalaria spectabilis (exotic species) and Crotalaria maypurensis (native species from Carajás Mineral Province (CMP) cultivated in a waste pile from an iron mining area in CMP. Seven fertilizations were tested (i = without fertilizers application; ii = NPK; iii = NPK + micronutrients; iv = NPK + micronutrients + organic compost; v = PK; vi = PK + micronutrients; vii = PK + micronutrients + organic compost). Fertilization contributed for the greater growth of both Crotalaria species and treatments based on NPK and micronutrients presented the best results (up to 257%) while organic fertilization did not promote satisfactory differences. Exotic Crotalaria presented greater number of nodules, nodule dry mass, chlorophyll a and b contents and presented free ammonium as the predominant form of N reflecting greater increments in biomass production compared to native species. Although presenting lower growth, the use of native species in the rehabilitation of mining areas should be considered, mainly because it is a species that presents good development and meets the current legislation, being an opportunity to restore local biodiversity.