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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. Introduction Intensive agricultural practices (e.g. high levels of fertilizer input and tillage) often increase crop yields but can also cause serious environmental problems and reduce the sustainability of agroecosystems (Tilman et al., 2002). Over the past decades, many sustainable agronomic practices have been developed to reduce or alleviate the negative effects of intensive farming. For instance, reduced tillage or no-tillage have been widely adopted to minimize soil disturbance and erosion (Zhang et al., 2012); organic fertilizers can be used to increase soil organic matter, improve soil structure, and enhance soil biological activity (Luo et al., 2018). Also, returning crop straw to the field is an environmentally friendly practice to supply organic carbon (C), nitrogen (N) and phosphorus (P) to the soil (Huang et al., 2021). Considering that straw returning is often applied with other agronomic practices, it is crucial to understand how different agricultural farming systems affect straw decomposition and the involved mechanisms. Plant litter decomposition is mainly influenced by biotic (e.g. litter quality, decomposers) and abiotic (e.g. soil properties and climatic variables) factors (Garcia-Palacios et al., 2016, Bani et al., 2018). Diverse organisms are involved in the process of litter decomposition, of which some fungal and bacterial taxa can directly decompose litters, whereas others (e.g. some protists and metazoans) may indirectly influence the decomposition by feeding on those primary decomposers or making the size of the litter smaller (Geisen et al., 2018, Wilschut and Geisen, 2021). Litter decomposition is closely related to the abundance and diversity of decomposers (Allison et al., 2013, Handa et al., 2014). However, increasing evidence has emphasized the importance of key decomposers in determining the decomposition process (Banerjee et al., 2018, Zheng et al., 2021). Furthermore, since decomposers live within complex multi-trophic food webs, the ecological co-occurrence networks and the ecological clusters within networks (i.e. ecological assemblages of species that strongly co-occur) should also be essential in regulating litter decomposition (Delgado-Baquerizo et al., 2020, Jiao et al., 2022). So far, however, very few studies have considered the linkages between multi-trophic or inter-kingdom communities (e.g. bacteria, fungi, protists and metazoans) and their interactions with straw decomposition. In addition to the biotic determinants, some abiotic factors, such as soil physical and chemical properties, can exert strong direct (e.g. soil moisture; Garcia-Palacios et al., 2016) and indirect (e.g. regulating decomposer communities; Bani et al., 2018) effects on litter decomposition. Thus, integrative investigations of diverse biological communities, environmental conditions, and their interactions are required to understand litter decomposition. Tillage and fertilization strongly influence soil abiotic and biotic properties and litter decomposition. Generally, conventional tillage often accelerates litter decomposition in soil compared to no-tillage (Lachnicht et al., 2004, Lupwayi et al., 2006, Alghamdi and Cihacek, 2021) because tillage will incorporate litter into the soil and facilitate the proliferation of decomposers (Schmidt et al., 2019). However, the response of straw decomposition to fertilization is diverse, depending on the fertilization regime and dose. Heavy N fertilization often slows litter decomposition by reducing decomposer abundance and suppressing the activities of oxidative enzymes (Knorr et al., 2005, Jian et al., 2016, Entwistle et al., 2018). Inconsistent effects of P fertilization on litter decomposition have been observed (Jiang et al., 2019, Tie et al., 2022), depending on whether the decomposers are N- or P-limited (Güsewell and Gessner, 2009). Compared to mineral fertilizers, organic fertilizers (e.g. animal manure) often accelerate litter decomposition by increasing microbial biomass and catabolic activity (Jin et al., 2018, Martínez-García et al., 2021). Furthermore, high fertilization levels may reduce litter decomposition by causing a stoichiometric imbalance in soil (Hessen et al., 2004) and high soil fertility will also decrease decomposition by alleviating microbial nutrient demands (Craine et al., 2007, Liu et al., 2018). Such a complex response of litter decomposition to fertilization suggests the need to compare fertilizer types in the same experimental system. A half-year of wheat straw decomposition was conducted in an experimental site, where tillage (conventional tillage or no-tillage) and fertilization (single or combined N, P and/or cow manure addition) were continuously applied for 16 years. We measured the decomposition rates of wheat straws and characterized bacterial, fungal, protistan and metazoan communities in the straw residues. We hypothesized that: (1) conventional tillage will accelerate straw decomposition compared to no-tillage because tillage will increase decomposer abundance; (2) straw decomposition rate shall vary among fertilizer types and decline with the increase of soil fertility; and (3) straw decomposition depends on biological communities and inter-kingdom network structure, particularly those taxa and ecological clusters that are very sensitive to fertilization or tillage. Section snippets Study site and experimental design This study was conducted at the Zhenyuan Loess Plateau Dryland Experimental Station of Gansu Academy of Agricultural Sciences in northwestern China (35º29′42″N, 107°29′36″E; 1249 m a.s.l.). This region is located in a warm-temperate semi-humid continental monsoon climate. The annual mean temperature is 8.3 °C, and the annual mean precipitation is 540 mm, whereas agricultural productivity heavily depends on rainfall. The soil was classified as Cumuli-Ustic Isohumosols, and the main crops were Effects of tillage and fertilization on soil properties Conventional tillage reduced soil organic C and total N contents in comparison to no-tillage, and M, NP and MNP treatments increased soil organic C and total N contents compared to the unfertilized control (Fig. 1a, b). Mineral N fertilizer obviously increased soil NH4-N and NO3-N concentrations, and both mineral P and manure fertilizers increased available P concentration (LME results; all p < 0.001; Fig. 1c-e). PCA results show that the first principal component (PC1) explained 46% of the Discussion Both tillage and fertilization strongly affected straw decomposition in soil, and straw mass loss was increased by tillage and declined with the increase of soil fertility (Fig. 2). We identified a key saprotrophic fungus (related to Apodus deciduus ), a key actinobacterium ( Leifsonia sp.) and an ecological cluster of inter-kingdom co-occurrence network, whose abundances closely correlated with the straw mass-loss rate (Fig. 3, Fig. 5). Tillage and fertilizer input could regulate straw Conclusions This study demonstrates that conventional tillage accelerated, but fertilizer inputs slowed straw decomposition by regulating the abundance and/or diversity of decomposers in a dryland agroecosystem. The straw mass loss was not only tightly related to the abundances of key fungal taxa (e.g. A. deciduus ) and functional groups (C-degrading bacteria and saprotrophic fungi) but also to particular ecological clusters of the inter-kingdom network. These findings highlight the importance of key Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements This work was supported by the National Natural Science Foundation of China ( 32060260 , 32171579 ), Natural Science Foundation of Gansu Province ( 23JRRA1029 ) and the RUDN University Strategic Academic Leadership Program. References (72) A. Bani et al. The role of microbial community in the decomposition of leaf litter and deadwood Appl. Soil Ecol. (2018) F. Bastian et al. 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