Pine straw raking and fertilizer source impacts on nitrogen mineralization in a loblolly pine plantation

Abstract

Pine straw production can supplement traditional revenues generated by loblolly pine plantation management. However, there is concern that excessive straw removal may adversely affect nitrogen availability and thus straw and fiber productivity in these stands. This study evaluated the long-term effects of straw raking combined with or without supplemental applications of either commercial inorganic fertilizer or poultry litter on soil N and C dynamics in a loblolly pine plantation in north central Louisiana. In situ mineralization and nitrification were measured monthly in response to: (1) no raking or fertilizer, (2) annual straw raking for seven years, (3) annual straw raking for seven years with inorganic fertilizer application for five years, and (4) annual straw raking for seven years with annual poultry litter application for five years. Annual straw raking did not substantially alter the N and C pools observed in this study. Annual applications of inorganic fertilizer did not lead to an accumulation of N in the uppermost 15cm of mineral soil. Annual applications of poultry litter in conjunction with straw raking increased total C, total N, and exchangeable N (particularly as NO3–N), N mineralization, and nitrification in soil. Due to the greater propensity of poultry litter to increase NO3–N in soil relative to inorganic fertilizer, applying poultry litter at the frequency, rate, and/or target N rate used for inorganic fertilizer may have led to application of N in excess of plantation N demand at this site.