Nitrogen Cycling from Increased Soil Organic Carbon Contributes Both Positively and Negatively to Ecosystem Services in Wheat Agro-Ecosystems

Abstract

Soil organic carbon (SOC) is an important and manageable property of soils that impacts on multiple ecosystem services through its effect on soil processes such as nitrogen (N) cycling and soil physical properties. There is considerable interest in increasing SOC concentration in agro-ecosystems worldwide. In some agro-ecosystems, increased SOC has been found to enhance the provision of ecosystem services such as the provision of food. However, increased SOC may increase the environmental footprint of some agro-ecosystems, for example by increasing nitrous oxide emissions. Given this uncertainty, progress is needed in quantifying the impact of increased SOC concentration on agro-ecosystems. Increased SOC concentration affects both N cycling and soil physical properties (i.e., water holding capacity). Thus, the aim of this study was to quantify the contribution, both positive and negative, of increased SOC concentration on ecosystem services provided by wheat agro-ecosystems. We used the Agricultural Production Systems sIMulator (APSIM) to represent the effect of increased SOC concentration on N cycling and soil physical properties, and used model outputs as proxies for multiple ecosystem services from wheat production agro-ecosystems at seven locations around the world. Under increased SOC, we found that N cycling had a larger effect on a range of ecosystem services (food provision, filtering of N, and nitrous oxide regulation) than soil physical properties. We predicted that food provision in these agro-ecosystems could be significantly increased by increased SOC concentration when N supply is limiting. Conversely, we predicted no significant benefit to food production from increasing SOC when soil N supply (from fertiliser and soil N stocks) is not limiting. The effect of increasing SOC on N cycling also led to significantly higher nitrous oxide emissions, although the relative increase was small. We also found that N losses via deep drainage were minimally affected by increased SOC in the dryland agro-ecosystems studied, but increased in the irrigated agro-ecosystem. Therefore, we show that under increased SOC concentration, N cycling contributes both positively and negatively to ecosystem services depending on supply, while the effects on soil physical properties are negligible.

Simulation of Soil Organic Carbon Effects on Long-Term Winter Wheat (Triticum aestivum) Production Under Varying Fertilizer Inputs

“…Building up SOC stock through agricultural measures (e.g., cover cropping, residue incorporation, reduced tillage) can affect soil properties, soil water retention and nutrient storage, affecting the productive capacity of soils ( Ingram et al, 2016 ; Paustian et al, 2016 ). Decomposition of SOC releases mainly N, which can increase crop yields where crop N supply is limited ( Palmer et al, 2017 ). Maintenance or build-up of SOC will require regular inputs of organic matter (OM) into the soil as the mineralization process will continually deplete the SOC over time, especially in environmental zones, where soil moisture and temperature are conducive for the mineralization process.…”

“…Maintenance or build-up of SOC will require regular inputs of organic matter (OM) into the soil as the mineralization process will continually deplete the SOC over time, especially in environmental zones, where soil moisture and temperature are conducive for the mineralization process. The other effects of increased SOC content are decrease in the bulk density ( Chen et al, 2017 ; Palmer et al, 2017 ; Minasny and McBratney, 2018 ) and small increase in volumetric water holding capacity ( Rawls et al, 2003 ). Due to these multiple effects, there is a great interest to quantify SOC effects in agro-ecosystems.…”

“…Due to these multiple effects, there is a great interest to quantify SOC effects in agro-ecosystems. SOC increase can have positive and negative effects ( Palmer et al, 2017 ; Minasny and McBratney, 2018 ). Among the multiple SOC effects, crop productivity and soil water retention are the priorities of the farmers to maintain sustainable agro-ecosystems.…”

Social and ecological analysis of commercial integrated crop livestock systems: Current knowledge and remaining uncertainty

“…The integration of a grazed forage crop can also enhance soil organic carbon (SOC) which provides multiple co-benefits such as accumulation and retention of N and P and other ecosystem services, except when external fertilizer applications are excessive Palmer et al, 2017). Land-based livestock integration enhances C-, N-, P-, and S-cycling (Acosta-Martínez et al, 2010;Archer and Smeins, 1991;Drinkwater et al, 1998;Soussana and Lemaire, 2014), but the impacts on carbon and nutrient accumulation remain strongly influenced by co-management factors such as N and P fertilization, tillage methods, rotation length and grazing intensity (de Faccio Carvalho et al, 2010;de Lima Wesp et al, 2016;Savian et al, 2014).…”

Leaching of dissolved organic carbon and nitrogen under cotton farming systems in a Vertisol

“…Soil organic carbon changes are closely related to nitrogen (N) cycling in soil, and N losses in runoff and drainage may parallel C losses in the same pathways (Palmer et al., ). A lysimeter study in a Vertisol near Narrabri, Australia, reported that dissolved organic nitrogen (DON) constituted 40% (8.7 kg ha −1 ) of total nitrogen losses (21.6 kg ha −1 ) in deep drainage (Macdonald et al., ).…”