Agroforestry systems, nutrients in litter and microbial activity in soils cultivated with coffee at high altitude

Abstract

Agroforestry systems are an alternative option for sustainable production manage- ment. These systems contain trees that absorb nutrients from deeper layers of the soil and leaf litter that help improve the soil quality of the rough terrain in high altitude areas, which are areas extremely susceptible to environmental degradation. The aim of this study was to characterize the stock and nutrients in litter, soil activity and the population of microorganisms in coffee (Cof- fea arabica L.) plantations under high altitude agroforestry systems in the semi-arid region of the state of Pernambuco, Brazil. Samples were collected from the surface litter together with soil samples taken at two depths (0-10 and 10-20 cm) from areas each subject to one of the follow- ing four treatments: agroforestry system (AS), native forest (NF), biodynamic system (BS) and coffee control (CT).The coffee plantation had been abandoned for nearly 15 years and, although there had been no management or harvesting, still contained productive coffee plants. The ac- cumulation of litter and mean nutrient content of the litter, the soil nutrient content, microbial biomass carbon, total carbon, total nitrogen, C/N ratio, basal respiration, microbial quotient, metabolic quotient and microbial populations (total bacteria, fluorescent bacteria group, total fungi and Trichoderma spp.) were all analyzed. The systems that were exposed to human inter- vention (AS and BS) differed in their chemical attributes and contained higher levels of nutrients when compared to NF and CT. BS for coffee production at high altitude can be used as a sustain- able alternative in the high altitude zones of the semi-arid region in Brazil, which is an area that is highly susceptible to environmental degradation.