Decomposition characteristics of maize (Zea mays. L.) straw with different carbon to nitrogen (C/N) ratios under various moisture regimes

Abstract

Decomposition of maize straw incorporated into soil with various nitrogen amended carbon to nitrogen (C/N) ratios under a range of moisture was studied through a laboratory incubation trial. The experiment was set up to simulate the most suitable C/N ratio for straw carbon (C) decomposition and sequestering in the soil. The purpose of this study was to determine organic C decomposition by measuring CO 2 evolution using alkali traps. Maize straw mixed with clay loam topsoil was supplied with four initial nitrogen rates (40, 80, 160, 320 mg N/0.5 g C) using (NH 4) 2 SO 4 , to adjust its C/N ratio to 80, 40, 18 and 9. The soil moisture content was maintained at four moisture levels to achieve 60, 70, 80 and 90% of field capacity. Each of the four nitrogen rates were tested against four moisture levels, arranged in complete randomized design and incubated at 20°C for 52 days. Results reveal that decomposition rates and cumulative CO 2-C was increased by about 40% in straw amended treatments as compared to the controls. On average, about 34.56% of the added straw C was mineralized to CO 2-C. Also, there was highly significant relationship between CO 2-C emission and incubation period (R 2 = 0.98). Further, straw addition with interactive effect of nitrogen and moisture had significant relationships (p < 0.05) with cumulative amounts of CO 2-C, soil organic C and microbial biomass nitrogen. In conclusion, straw returning with appropriate N doses and optimum moisture can sequester and restore organic C in soil, thereby improving soil quality.

Maize residues, soil quality, and wheat growth in China. A review

“…A C/N ratio of 18:25 seems to be most suitable for microbial activity. The retention of maize residues results in a high soil C/N ratio, which restricts the decomposition of residues and leads to net N immobilization (Abro et al 2011;Alijani et al 2012). Some reports have recommended the application of additional inorganic N to amend the C/N ratio to an appropriate level; this practice has profound effects on the decomposition of maize residues, CO 2 evolution, C mineralization, and soil properties for subsequent crops (Abro et al 2011).…”

“…The retention of maize residues results in a high soil C/N ratio, which restricts the decomposition of residues and leads to net N immobilization (Abro et al 2011;Alijani et al 2012). Some reports have recommended the application of additional inorganic N to amend the C/N ratio to an appropriate level; this practice has profound effects on the decomposition of maize residues, CO 2 evolution, C mineralization, and soil properties for subsequent crops (Abro et al 2011). In China, it has been observed that maize residue retention combined with N fertilization results in increases in the SOM content, field water holding capacity, soil porosity, nutrient availability (Gong et al 2008), WUE, NUE (Yan et al 2011), grain yields (by 7.1-11.1 %), and N harvest index (by 6.2-16.7 %) compared with no N fertilizer treatment Chen 2008a, 2008b).…”

“…The shift in the microbial community composition is accompanied by a significant reduction in the activity of phenol oxidase, a lignin-degrading enzyme produced by the white-rot fungi; this observation indicates that N fertilization may decrease the decomposition of residues, particularly in the late decomposing stages. The reduction in the mineralization of residues in later stages indicates that a greater amount of residue C is sequestered in the soil or incorporated into the microbial biomass (Abro et al 2011).…”

“…1). However, the removal of crop residues from the field is known to hasten the decline in soil organic carbon (SOC), especially when coupled with conventional tillage (Abro et al 2011). Therefore, residue retention should be strongly recommended in crop production (Wu et al 2002).…”

“…The remaining residue has commonly been used as animal fodder and fuel or is burned directly in the field (Abro et al 2011;Ma et al 2003;Wang et al 2011b). Such burning of crop residues leads to environmental pollution and the loss of resources.…”