Decomposition and nutrient release of four potential mulching materials for poplar plantations on upland sites

The application of organic residues and the release dynamics of nutrients during decomposition may be crucial to improving poplar growth in upland areas. Field experiments were conducted in Guizhou Province, southwestern China, to determine differences in biomass decomposition of four potential mulching materials in one-year-old poplar plantations. Results showed the initial total content of N, P, K, Ca and Mg in the mulches ranged from 30.0 to 35.0 g/kg and was significantly greater in Quercus fabri, Imperata cylindrica var. major and Pteridium aquilinum var. latiuscukum than in Coriaria nepalensis. The weight loss pattern of these four species during decomposition could be best described by a double exponential decay model, and monthly decay rate coefficients (k) were in the order Q. fabri > C. nepalensis > I. cylindrica > P. aquilinum over a one-year period. Total nutrient (N, P and K) release of the four mulching materials ranged from 74.2 to 90.8% of the initial content after one year of decomposition, while nutrients were released in the order K > P>N. Nutrient release was fastest in C. nepalensis followed by Q. fabri, I. cylindrica, and slowest in P. aquilinum. Thus, taking into account initial nutrient content, nutrient additions and decay rates, the sprouts of woody species (Q. fabri and C. nepalensis) with massive foliage proved to be more important as nitrogen sources than the grass or fern.