Decomposition dynamics and nutrient release of walnut orchard litter in the Taihang Mountains, China

The decomposition of walnut litter components (leaves, husks, and male inflorescences) were studied to understand the decomposition process and its role in the soil fertility in walnut plantation in the southern Taihang Mountains of Hebei Province, China. The experiment was carried out at a walnut plantation in the southern Taihang Mountains of Hebei Province, China. The analysis focused on the dynamic changes of four mineral elements, trace elements, and lignin. The results showed that during the 300-day decomposition period, the mass residue percentages of the three types of litter were leaves (64.92%), husks (37.90%), and male inflorescences (21.33%). The 120th day was a turning point in the decomposition process. Before this, the decomposition process was active and relatively rapid; after reaching this inflection point, the rate of decomposition tended to stabilize. The Olson model was used to simulate and predict the decomposition process of three types of litter. The order of the decomposition coefficient k for litter types was male inflorescence > husks > leaves. The higher the k value, the greater the decomposition rate. The 50% decomposition time estimates for leaves, husks, and male inflorescences were 1.28a, 0.53a, and 0.39a, respectively, with values of 5.54a, 2.28a, and 1.68a for 95% decomposition, respectively. After 300 days, according to the criterion of NR < 100%, the C, N, P, K, and lignin contents of the three types of litter showed a net release state, with a wave release decomposition form and a small enrichment phenomenon occurring during the process. Compared with the initial state of decomposition, the four trace elements generally exhibited a net release state.