N Mineralization from Residues of Crops Grown with Varying Supply of 15N Concentrations

Abstract

A laboratory study was conducted to evaluate the effects of varying 15 N concentrations on crop residue quality (rice straw=RS and soybean=SY) and N mineralization. Two crops (rice and soybean) were grown in a glass-house under four 15 N concentrations, i.e., 0 mM (N0), 0.625 mM (N1), 2.5 mM (N2) , and 10 mM (N3) supplied as CO( 15 NH 2 ) 2 , in 30 cm diameter plastic pots containing 5 kg of quartz sand. Eight weeks after planting the above-ground biomass was pruned and oven dried at 60 o C for 48 hours and analyzed for polyphenol, lignin, N, C, C/N, organic matter and % 15 N-abundance. Each of the eight crop residues produced from this experiment was then incorporated into 10 g of soil in a 50 ml plastic bottle. Mineralization of N from the residues was measured over a 14-week period under controlled non-leaching conditions.The results showed that increasing N concentration in the nutrient solution (0 to 10 mM) increased total N but decreased C, lignin and polyphenol content in the crop residues. The results suggested that N supply may increase the quality of the crop residues, as indicated by decreasing of C/N, lignin/N, polyphenol/N ratios. SY residue released N about 2x faster than RS residue, and the amount N released increased with increasing supply of the N concentration. At the 10 mM N supply, RS and SY residues released respectively 3734,857 mg kg -1 and 4352.34 mg kg -1 cumulative amount of mineral N with the mineralization rate about 7x faster than without 15 N in the solution. Differences in the %N mineralized were determined by the quality of the crop residues. Regression analyses showed that the N, lignin and polyphenol contents were the residues quality factors which could be used to predict N mineralization of the crop residues, and the relationship was best described by a linear regression.

Effect of organic matter and soil fertility on nitrogen mineralization and its uptake by cassava (Manihot esculenta Crantz) in a typic Hapludults

“…Findings of the present study indicated that the mixing of organic matter with groundnut having low C:N ratio while the maize biomass has high C:N and because of this groundn ut shows higher rate of mineralization as compared to maize. Result of the present study are in agreement with the finds of Sholihah et al (2012) those who have reported that the rate of mineralization indirectly correlates with the ratio C:N (0.582*), which shows that higher mineralization take place at low C:N (Abera et al, 2012). The observation of N potential also shows the similar pattern of the rate of mineralization.…”

The Enhancement of Soybean Growth and Yield in a Field Trial through Introduction of Mixtures of Bradyrhizobium japonicum, Bacillus sp. and Pseudomonas chlororaphis

“…Nitrogen content was 4.85-5.08% and was significantly higher than or equal to the values reported by Sholihah et al (2012). Araujo and Hungria (1999) demonstrated that B. subtilis introduction increases the contribution of the biological nitrogen fixation process in co-inoculated soybean seeds with crude or formulated metabolites.…”

Comparison of two kinetics models for estimating N mineralization affected by different quality of organic matter in Typic Hapludults

“…It is due to C:N ratio decrease. Sholihah et al (2012) reported that mineralization rate has correlation to C:N ratio (0.582*). Organic matter with low C:N ratio has higher mineralization rate compared to organic matter with high C:N ratio (Abera et al, 2012).…”