C and N mineralization and dissolved organic matter potentials of two contrasting plant residues: effects of residue type, moisture, and temperature

Predicting carbon (C) and nitrogen (N) mineralization of plant residues returned to soils is vital for foreseeing carbon dioxide (CO2) emissions into the atmosphere and soil nitrogen availability. Similarly, dissolved organic matter (DOM) is an important factor in forecasting microbial degradation of organic inputs as it represents the most active organic fraction, both biologically and chemically. In this study, an incubation experiment was conducted to investigate C and N mineralization and DOM potentials of residues of peanut (green manure, GM) and rice (rice straw, RS) at moisture regimes 50% (W1) and 100% (W2) of water holding capacity and temperature T1 (25 degrees C) and T2 (35 degrees C). The incorporation of plant residues significantly (P < 0.05) increased the mineralization and DOM, compared to controls. We observed that though GM residue had high carbon and nitrogen and DOM potential, but because of low C:N ratio and lignin, cellulose, and hemicelluloses compounds were vulnerable to easy decomposition with the increase in temperature, which led to more CO2 emission, fast mineralization, and less net OM in the soil. Conversely, RS residue, due to high C:N ratio, lignin, cellulose, and hemicelluloses compounds was resistant to decompose with the increase in temperature and possessed slow mineralization and eventually low CO2 emission. The moisture regimes (W1 and W2) and temperature (T1 and T2) had significant (P < 0.05) effect on mineralization and DOM potentials of both plant residues. The significant decrease and increase in the mineralization and DOM potential of both plant residues was observed with the increase in moisture and temperature. Our results suggest that plant residues with high C:N ratio, lignin, cellulose, and hemicelluloses compounds like RS are resistant to decompose with the increase in temperature, as a result possessed slow decomposition and mineralization, and can be used as an eco-friendly organic amendment, to get enduring benefits, and to mitigate the problem of carbon losses and CO2 emission from soil to atmosphere.