Nutrient release during decomposition of leaf litter in a peach (Prunus persica L.) orchard

The decomposition of plant residues has a pivotal role in carbon and nutrient cycles in agricultural ecosystems, where it can contribute to the sustainable management of the crops. In this paper we report a study on the release of C and nutrients during the decomposition of peach abscised leaves in northern Italy. Litter bags containing a representative amount of leaf material were installed under tree canopies either on the soil surface under open field conditions or on the soil surface in pots under partially controlled conditions. Potted leaf litter was pre-labelled with 15N. We observed that in 3 years, peach leaves lost 85% of their initial mass mostly attributable to cellulose decomposition, while new lignin or lignin-like compounds were synthesised during the first stages of the decomposition process. Nutrient dynamics differed depending on the considered element. Nitrogen and sulphur were initially immobilized into the litter to be released only starting after 44 weeks from the beginning of the decomposition. Potassium and magnesium were rapidly released in the winter following leaf abscission, reaching an amount that remained constant up to the end of the trial. Calcium and phosphorus release was slow, but constant throughout the three-year study period. With the only exception of Mg, 80–90% of initial amounts of mineral elements had released from decomposing peach leaves after 3 year from leaf abscission. Since in mature stands leaf litters of different ages coexist on the soil surface 80–90% of the nutrients contained in the abscised leaves are expected to return annually to the soil and potentially be available for subsequent root and/or microbial uptake.