Abstract

Alternatives to traditional agricultural farming practices that combine production and environmental conservation, such as agroforestry systems, are currently being studied. This study aimed to quantify the contribution of trees to nutrient input and output in crops grown in an agrosilvopastoral system in the municipality of Sobral, Ceará State, Brazil. Nutrient concentrations were quantified in shade and sun leaves of Cordia oncocalyxAllemão (called pau-branco) trees in the rainy and dry seasons and in maize leaves at the time of harvest. Nutrient concentrations in different soil layers (0-10, 10-20 and 20-40cm) were also quantified at 0.4 and 4.0 m from the trunk of C. oncocalyxtrees. The contribution of the trees to the nutrient input to the system and nutrient output due to the removal of maize plants were also assessed. The soil under the canopy of C. oncocalyxshowed the highest concentrations of total N, K, P, Fe, Cu, Zn and Mn. However, few differences were noted in the concentrations of maize leaf nutrients as a function of the distance from the trunk. The trees may contribute up to 35kg ha^-1 Ca, 19kg ha^-1 N and 15kg ha^-1 K, whereas approximately 2.3kg N, 5.6kg K and 0.2kg Ca leave the system with the removal of maize plant shoots. Therefore, maintaining trees in production systems significantly contributes to replenishing the nutrients lost from harvesting crops.

Keywords

cordia oncocalyx, agrosilvopastoral system, maize, nutrient cycling, organic, atmospheric, plants, weathering, environmental, structurally, functionally, conventional, concentrations, monoculture, forestry