Soil Carbon and Nitrogen Dynamics in a Silvopasture Agroforestry Ecosystem in North Alabama.

Agroforestry systems are used to manage, maintain and develop the ecosystem with the aim of achieving agricultural and economic growth which also helps in sustaining the environment. The study was done to assess environmental sustainability of silvopasture system by measuring the impact of forage production and management practices on indicators of soil quality, productivity and sustainability and also to investigate the effect of soil management practices on soil C and N sequestration and emission of CO₂ to the atmosphere. The study was conducted at the Winfred Thomas Agricultural Research Station, Hazel Green, Alabama in the Tennessee Valley Region of North Alabama in 2011 and 2012. A total of 13 treatments were used in a split-plot experimental design. Soil samples from the study area were analyzed for soil pH, total soil C and N. Data for soil moisture, soil temperature and soil CO₂ fluxes were collected in the field. Inorganic fertilizer application increased total soil N in the fertilized plots, by an average of 91% in the 0-90cm soil depth. Forest plantation plots had higher total soil N and C, compared to the agroforestry plots suggesting a higher potential for soil C and N sequestration in the densely planted system compared to the wider agroforestry planting. Soil CO₂ fluxes in the grass pasture system were consistently higher compared to those in the loblolly pine plots prior to grazing. The soil CO₂ fluxes were significant and highly correlated to the soil temperature in the silvopasture plots. Changes in total soil C due to soil management practices usually take time to be realized. It is therefore expected that with time, increased forage production and litter accumulation, due to fertilizer application, can increase soil C storage due to more biomass input.