Key decomposers of straw depending on tillage and fertilization

Abstract

Crop straw is often incorporated into soil, but how agricultural practices affect straw decomposition and the involved biological mechanisms are not fully understood. We conducted a half-year straw decomposition assay in a 16-year experiment with tillage (conventional tillage or no-tillage) and fertilization (single or combined nitrogen, phosphorus and/or cow manure addition) regimes in a dryland agroecosystem. Straw decomposition and extracellular enzyme activities as well as bacterial, fungal, protistan and metazoan communities in the straw residues were analyzed. Straw mass loss was accelerated by tillage, whereas it was slowered by all but not single nitrogen fertilization treatments and correlated negatively with soil fertility. Enzyme activities were sensitive to tillage and fertilization but not correlated with straw decomposition. Straw mass loss was positively correlated with the relative abundances of a dominant saprotrophic fungus (related to Apodus deciduus) and an ecological cluster of the inter-kingdom co-occurrence network, whose abundances were increased by tillage and decreased with increasing soil fertility. This study shows strong effects of agricultural practices on straw decomposition, and highlights the importance of key decomposers and inter-kingdom interactions in regulating straw decomposition. We propose that straw incorporation should be applied with appropriate tillage and reduced fertilizers in dryland agroecosystems.