Release of nitrogen, phosphorus, and potassium during the decomposition of apple (Malus domestica) leaf litter under different fertilization regimes in Loess Plateau, China

Abstract

The decomposition of apple (Malus domestica) leaf litters has a pivotal role in nutrient release in orchard ecosystems. We studied the decomposition rate and subsequent release of nitrogen (N), phosphorus (P), and potassium (K) nutrients over 24-months using the litterbags method, from three types of litters sampled from an apple orchard which received different rates of N, P, K fertilization (control, CK; low fertilizer rate, LF; high fertilizer rate, HF). The patterns of mass loss of all three litters were quite similar following the exponential decay model. However, the amount of mass loss was greater for HF and LF litters than that for CK litter over the first six months. During the initial six months, concentrations of N and P in the leaf litters increased while that of K declined. Subsequently, concentrations of all elements decreased during 24-months of incubation. The release of N and P from leaf litter was positively correlated to the respective concentrations in the leaf litter at the beginning of decomposition. The amounts of N and P release from the litter were greater for that collected from the trees which received HF than that under CK and LF treatments during the course of decomposition in the two years. The rapid release of K occurred during the early stage across all litters and was not influenced by varying levels of leaf nutritional status. At the end of 24 months of decomposition, the relative release of nutrients from litters followed the order: K > N > P. The mean quantities of N, P, and K released during the first and second year following the application of 10, 6, 58% and 63, 6, 8% of recommended rates at respective nutrients for young apple orchards in Loess Plateau. Therefore, the results suggest that nutrient release from leaf litter in an apple orchard system can contribute a significant portion of the nutrient requirement for apple production. Accounting for this nutrient contribution in the annual fertilizer management is important to avoid excess application, optimize net returns, and maintain sustainable production systems.