Nitrogen distribution within the soil-plant-microbial system in response to pre-thinning fertilization treatments in LouisianaThis article is part of a larger document. View the larger document here.
Improvements in nitrogen (N) uptake efficiency and plantation growth require refined silvicultural systems that consider soil type, stand development, ecology, and their interactions. On four unthinned, mid-rotation loblolly pine plantations in Louisiana located on a gradient of soil drainage classes, soil, plant, and microbial N dynamics were measured in response to fertilization and understory vegetation control. Treatments consisted of an untreated control, N and phosphorus (P) fertilization, and N + P fertilization with herbicide understory suppression. Results indicated understory suppression was necessary to effectively promote increases in pine foliage N concentrations when stands had no prior history of herbicide application. Understory control was most effective in enhancing pine response to fertilization on a well-drained site. Soil N returned to background levels within 6 months of application at all sites, and microbial biomass N was relatively unaffected by fertilization and brush control at all sites.