Effect of crop residue returns on N₂O emissions from red soil in China

Abstract

For a long time, farmers in the red soil region of southern China have returned crop residues to the soil, but how various crop residues influence nitrous oxide (N 2 O) emissions is not well understood. We compared the influence of returning different crop residues [rapeseed cake (RC), maize straw, rice straw and wheat straw (WS)] in combination with different levels of nitrogen (N) fertilizer (nil, low and high) on red soil N 2 O emissions. Results confirmed the inverse relationship between cumulative N 2 O emissions and residue C:N ratio in red soil under different levels of N fertilizer. However, Nfertilizer application did not significantly influence N 2 O emissions in the WS (which had the highest C:N ratio) and corresponding control treatments, while it enhanced N 2 O emissions in the RC (which had the lowest C:N ratio) treatment and displayed significantly higher cumulative N 2 O emissions with low N fertilizer application. This phenomenon may be attributed to the poor nutrient content in red soil, which leads to 'Liebig's Law of the Minimum' on available C. N fertilizer application provided sufficient available N, while the readily available C, which was mainly dependent on the degradability of the residue, became the crucial factor influencing N 2 O emissions. Additional experiments, which showed that the addition of glucose and sucrose could increase N 2 O emissions when N (NH þ 4 À N) was sufficient, confirmed this hypothesis. Thus, to reduce N 2 O emissions when returning residues to red soil, we suggest that both the residue C:N ratio and the quality should be considered when deciding whether to apply N fertilizer.

Understanding the relations between soil organic matter fractions and N2O emissions in a long‐term integrated crop–livestock system

“…The influence of C on denitrification occurs with both the provision of C to denitrifying bacteria and the stimulation of microbial metabolism, which increases consumption, creating favourable conditions for denitrification. Wu et al () also observed an inverse relation between N 2 O fluxes and the biomass C/N ratio on different cover crops, confirming our findings. Meurer et al () verified that the formation of stable microaggregates and the adhesion of fine soil particles and iron oxides create a soil structure that provides better drainage and greater aerobiosis.…”

“…Kong et al () showed that the application of synthetic N fertilizer causes the fastest N turnover and greater incorporation of fertilizer‐N into the less stable silt‐and‐clay fraction, but also the largest N 2 O fluxes among the three cropping systems. The interactions between SOM and N 2 O emissions usually result from a larger proportion of labile fractions in SOM, with a large supply of residue‐derived N (Wu et al, ). In addition, the strong organo–mineral interaction of mineralized SOM fractions, which is predominant in the weathered soils of tropical regions, can contribute to SOM stabilization and explain the reduced N 2 O emissions from savanna soils under natural vegetation (Santos et al, ).…”

Short‐term grazing of cover crops and maize residue impacts on soil greenhouse gas fluxes in two Mollisols

“…Our previous study (e.g., Abagandura et al., 2019b) also reported that grazing CCs for ∼1 mo did not affect cumulative N 2 O flux vs. ungrazed CC. However, significantly higher cumulative N 2 O flux in LdC+G than in the GdC+G at this site may be due to higher N concentration of legume residue that decompose rapidly and release N 2 O. Mineralization of crop residues and flux of N 2 O is dependent on C:N ratio of the residues (Wu, Lin, Liu, Wan, & Hu, 2016). The legume‐based plant residues having a narrow C:N ratio and high N content generally result in rapid N mineralization and particularly higher N 2 O flux vs. residues having high C:N ratio (Li, Sørensen, Olesen, & Petersen, 2016).…”

Returning Tea Pruning Residue and Its Biochar Had a Contrasting Effect on Soil N2O and CO2 Emissions from Tea Plantation Soil

“…However, other studies observed the opposite effect on soil N 2 O emissions after residue amendment [12,13,33]. According to the results of Wu et al [34], the residue C/N ratio is a good predictor of soil N 2 O emissions. Chen et al [9] reported that residue amendment generated significantly positive effects on soil N 2 O emissions when C/N ratios of crop residues were <45, slightly positive effects for C/N ratios of 45-100, and slightly negative effects for C/N ratios >100.…”

“…Chen et al [9] reported that residue amendment generated significantly positive effects on soil N 2 O emissions when C/N ratios of crop residues were <45, slightly positive effects for C/N ratios of 45-100, and slightly negative effects for C/N ratios >100. Wu et al [34] observed that rapeseed cake with low C/N ratio showed high N 2 O emissions while wheat straw with high C/N ratio showed lower cumulative N 2 O emissions from red soil. Muhammad et al [35] discussed that incorporation of plant residues enhanced N 2 O emissions and this enhancement was quantitatively dependent on C/N ratio of the residues, lower C/N ratio of the residues inducing higher concentration of dissolved organic carbon and larger amount of N 2 O emission.…”