The effects of different soil nutrient management schemes in nitrogen cycling

Abstract

It is imperative for sustainable agriculture to explore practices and inputs creating low N₂O emission capacity without reducing the productivity of the agricultural system. To evaluate different nutrient management schemes, a microcosm study was conducted to assess the direct N₂O emission from soil. Four different treatments were used to provide a preliminary assessment of N₂O emissions, as well as the concentrations of nitrates (NO₃^-) and ammonium (NH₄⁺) produced in soil: compost (derived from green plant residues), chickpea residues (green manure) in two different N concentrations (2.6% and 5.5%, respectively) and ammonium nitrate (fertilizer). The soil was thoroughly mixed with the organic amendments and ammonium nitrate and incubated for 31 days. The emissions of N₂O were higher in green manure with high-N content, as a source of nitrogen in the soil, and were similar to the emissions measured from the chemically fertilized soil. In particular, chickpea residues, with high-N content, exhibited cumulative N₂O emissions, equal to 266.17 μg N/m², whereas in fertilized soil the emissions were 267.10 μg N/m². On the contrary, the incorporation of chickpea plant residues with low-N content can be an efficient way to minimize the N₂O emissions at 21.63 μg N/m². The emissions of N₂O when compost was applied, remained relatively low, equal to 5.47 μg N/m², and in comparison to soil without any treatment. Overall, a positive association between NH₄⁺, NO₃^- in soil and N₂O emissions were observed. However, this response was treatment depended, and the significant positive correlation between NH₄⁺ and N₂O emissions were noticed in soils treated with ammonium nitrate, chickpea residues with low N content, as well as untreated controls. On the contrary, the positive correlation observed between NO₃^- and N₂O emissions in soils receiving compost and high N chickpea residues, suggest that the different treatments are differentially affecting the processes that are contributing to N₂O emissions in agricultural soils. These findings, emphasize that the different nutrient management schemes are differentially affecting the main process contributing to N₂O emissions in agricultural soils.

Keywords: Climate change; N(2)O; NH(4)(+); NO(3)(−); Nutrient management; Soil.