Effect of Loblolly-Pine Thinning on Pastoral-Silvopastoral System Establishment and Some Soil Properties.

Cycling of nutrients in pastoral systems is different from that in cropping systems as the grazing animals are excreted back to the pasture most of the ingested nutrients. This study was conducted at the Florida A&M University Research & Extension Center, Quincy on Ultisols of the Orangeburg series. Twenty year-old loblolly pine (Pinus taeda L.) trees were systematically thinned in 2002 for establishing of a pastoral-silvopastoral system with Boer x Spanish crossbred goats (Capra hircus). Prior to sowing the seeds of either bahiagrass (Paspalum notatum Flügge) or bermudagrass [Cynodon dactylon (L) Pers.], soil samples were randomly collected at the depth of 15 cm; samples were also taken at the end of three consecutive grazing seasons from both silvopastoral and pastoral plots. The soil samples were analyzed for macro- and micro-nutrients to evaluate the impact of tree and forage growth on soil constituents. The results are discussed in relation to the nutrient-use efficiencies and an attempt is made to find possible relationships and distribution patterns. A decrease for Total Kjeldahl Nitrogen (TKN), P, K, Ca, Mg, S, and Zn concentrations in silvopastoral plots was observed, while in the pastoral plots the decrease of TKN, P, Ca, and Zn was less pronounced. These results suggested that a mixed silvopastoral-pastoral system need to be managed by individual subsystems in order to ensure the effective utilization of nutrients from both the trees and the grass forage. This is particularly important for goat producers who want to manage silvopastoral systems for sustainable agriculture.