Soil fertility status controls the decomposition of litter mixture residues

Abstract

Increasing agroecosystem biodiversity with cover crops can restore many ecosystem functions that are lost with simplified crop rotations. Mixtures of species with complementary plant traits, such as legumes and grasses, may increase multiple functions at once, including soil nutrient supply and retention, which depend on microbial decomposition dynamics. Litter mixtures can stimulate decomposition compared to individual species, and decomposition also varies with soil properties. However, the interactive effect of cover crop functional type and soil fertility status on decomposition are not known. Here, we tested for mixture effects with a legume–grass litter in soils with lower and higher levels of fertility. We also identified specific soil properties that are associated with those effects. We incubated hairy vetch, cereal rye, and vetch‐rye litter treatments for 360 d in two soils from fields with contrasting management histories and fertility levels, as defined by biological indicators such as particulate organic matter (POM) pools. We measured decomposition dynamics through respired CO2, microbial biomass, microbial extracellular enzyme activity, and inorganic nitrogen (N) mineralization. With no litter addition, the soil with larger POM pools had twofold greater microbial biomass C, seven times more net N mineralization, and respired 58% more CO2. Across both soils, after 30 d microbial biomass C increased by 58–208% following litter addition, and litter addition significantly increased CO2 production compared to the no‐litter control. However, there was no difference in the magnitude of CO2 production among cover crop treatments and soils after litter addition. The lower fertility soil had a greater response to the litter C input for CO2 production and enzyme activities in soil. Furthermore, the size and N content of free and intra‐aggregate POM pools were associated with differences in the microbial response to litter addition. Our results demonstrate that cover crop litter affects microbial decomposition dynamics differently in soils with distinct soil fertility levels and suggests that new C inputs have larger effects in lower fertility soils. Understanding how soils with different fertility levels respond to diverse cover crops, including mixtures, will inform management of agroecosystems for sustainability.

Rye–vetch residue quality and plastic mulch affect soil nitrogen dynamics in vegetable production systems

“…This result contrasts with common speculation that the combination of contrasting residue qualities in cereal–legume mixtures can alter patterns of N release to mitigate asynchrony and N leaching (Crews & Peoples, 2005). Our results are more consistent with previous research suggesting that combinations of residues of contrasting quality exhibit patterns of net N mineralization similar to the weighted average of the high‐ and low‐quality residues individually, rather than resulting in release that is notably more synchronous with crop demand (Blesh & Ying, 2020; Palm et al., 2001; Poffenbarger et al., 2015; Sievers & Cook, 2018). Over the course of a 30‐week laboratory incubation, Kuo and Sainju (1998) tracked net N mineralization from mulched rye‐vetch residue combinations along a gradient from 100% vetch to 100% rye.…”

Management of Alternative Organic Fertilizer Sources for Wheat Production: Evidence from Decomposition Dynamics and Agronomic, Economic, and Farmers’ Preferences

“…Researchers and decision-makers are becoming more interested in maintaining soil health to fulfll the rising need for agricultural production to meet the world's needs for food and energy [1]. An increase in productivity is likely attained through an adequate and balanced supply of nutrients.…”

“…An increase in productivity is likely attained through an adequate and balanced supply of nutrients. To meet the nutrient needs of crops, employing organic resources would therefore be a necessary practice [1][2][3][4][5][6][7][8].…”

“…According to various studies [1,7,9], organic materials are considered a source and a repository of many essential plant nutrients that can be rendered available to succeeding crops through litter decomposition. Additionally, they compensate for minor defcits in secondary and micronutrients not addressed by mineral fertilizers.…”

Residue‐ and nitrogen‐induced carbon mineralization varies with soil fertility status

“…Besides the N supplied by residues and fertilization, soil fertility, and particularly soil N availability, has important effects on the decomposition of cellulosic substrates (Schmidt & Ruschmeyer, 1958; Stewart et al., 2015), as would be expected in view of evidence that the input of mineral N promotes the activity of cellulose‐degrading enzymes such as cellulase and β‐glucosidase (Henriksen & Breland, 1999; Keeler et al., 2009). Such activities tend to be greater for highly productive soils that are well structured and nearly neutral in pH, which is conducive to an increase in microbial biomass (Blesh & Ying, 2020; Xu et al., 2019). In contrast, C mineralization can be impeded in low‐fertility soils due to limited N availability that triggers a shift toward ‘microbial N mining’ whereby N is scavenged from recalcitrant SOM (Chen et al., 2014).…”