Abstract
Abstract In agriculture, winter cover crop (WCC) residues are incorporated into the soil to improve soil quality, as gradual litter decomposition can improve fertility. Decomposition rate is determined by litter quality, local soil abiotic and biotic properties. How these factors are interlinked and influenced by cropping history is, however, unclear. We grew WCC monocultures and mixtures in rotation with main crops Avena sativa (oat) and Cichorium endivia (endive) and tested how crop rotation influences WCC litter quality, abiotic and biotic soil conditions, and litter decomposition rates. To disentangle WCC litter quality effects from WCC soil legacy effects on decomposition, we tested how rotation history influences decomposition of standard substrates and explored the underlying mechanisms. In a common environment (e.g. winter fallow plots), WCC decomposition rate constants (k) correlated negatively with litter C, lignin and, surprisingly, N content, due to strong positive correlations among these traits. Plots with a history of fast‐decomposing WCCs exhibited faster decomposition of their own litters as well as of the standard substrates filter paper and rooibos tea, as compared to winter fallow plots. WCC treatments differentially affected soil microbial biomass, as well as soil organic matter and mineral nitrogen content. WCC‐induced soil changes affected decomposition rates. Depending on the main crop rotation treatment, legacy effects were attributed to biomass input of WCCs and their litter quality or changes in microbial biomass. Synthesis and applications. These results demonstrate that decomposition in cropping systems is influenced directly through crop residues, as well as through crop‐induced changes in soil biotic properties. Rotation history influences decomposition, wherein productive winter cover crops (WCC) with low lignin content decompose fast and stimulate the turnover of both own and newly added residues via their knock‐on effect on the soil microbial community. Thus, WCC have promise for sustainable carbon‐ and nutrient‐cycling management through litter feedbacks.
Highlights
| MATERIALS AND METHODSWinter cover crop legacy on litter decomposition was tested in a field experiment on arable sandy soil at the field facilities of Wageningen University (Wageningen, The Netherlands, 51°59′41.9′′N 5°39′17.5′′E)
Depending on the main crop rotation treatment, legacy effects were attributed to biomass input of winter cover crops (WCC) and their litter quality or changes in microbial biomass
We found that WCC decomposition rates related negatively with lignin, C and surprisingly N concentrations
Summary
Winter cover crop legacy on litter decomposition was tested in a field experiment on arable sandy soil at the field facilities of Wageningen University (Wageningen, The Netherlands, 51°59′41.9′′N 5°39′17.5′′E). Differences between relative WCC legacy effects on litter and standard-substrate decomposition were tested with a mixed linear model including litter type as main factor, with block, preceding-and current main cropping as random factors. With multiple linear regression, we tested how decomposition rates of filter paper and rooibos were influenced by the decomposition drivers (H2b): directly through WCC residue turn-over rates (WCC k in fallow) and WCC residue input (shoot biomass), or indirectly through soil abiotic (SOM, mineral N, potential N mineralisation, pH), microbial biomass and composition (bacterial and fungal biomass, F:B, ergosterol and coordinates PCA axis one and two). Winter cover crop decomposition rates differed significantly between WCC treatments (F5,203 = 109.79, p < 0.0001; Figure 1d, Supporting Information Table S3). Decomposition rates of all standard substrates were affected by rotation design, with most pronounced effects for filter paper and rooibos tea Both substrates decomposed fastest in Raphanus and Raphanus+Vicia plots and slowest in former fallow plots. Neither Filter paper nor rooibos decomposition rates were related to any of the abiotic soil properties
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