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Soil Biology and Biochemistry
Hadas, A., Inst. Soil, Water and Environ. Sci., A.R.O., Volcani Center, Bet-Dagan 50250, Israel
Kautsky, L., Inst. Soil, Water and Environ. Sci., A.R.O., Volcani Center, Bet-Dagan 50250, Israel
Goek, M., Department of Soil Science, Cukurova University, Adana, Turkey
Kara, E.E., Department of Environment, Faculty of Engineering, Nigde University, Nigde, Turkey
The dynamics of inorganic N in soil following the application of plant residues depends on their composition. We assumed that all plant materials are composed of similar components, each decomposing at a specific rate, but differ in the proportions of the various components. The NCSOIL model that simulates C and N turnover in soil was used to link the rates of residue decomposition to their composition, defined as soluble, cellulose-like and lignin-like C and N, and thereby integrate short and long-term effects of residues on available N dynamics in soil. Five plant residues in a wide range of C:N ratios were incubated in soil for 24 weeks at 30°C, during which C and N mineralization were measured. The materials with large C:N ratios (corn, rice hulls and wheat straw) were also incubated with NH4+-N to avoid N deficiency. The residues were analyzed for total and soluble C and N. The partitioning of insoluble C and N between cellulose- and lignin-like pools was optimized by best fit of simulated C and N mineralization to measured results. The decomposition rate constants of the soluble and lignin-like pools were assumed to be 1.0 and 10-5d-1, respectively, and that of the cellulose-like pool, obtained by model optimization against mineralization of cellulose with NH4+-N in soil, was 0.051d -1. The optimized, kinetically defined lignin-like pool of all residues was considerably larger than lignin contents normally found in plant residues by the Van Soest procedure. Gross N mineralization of tobacco and rape residues was similar, but N recovery from tobacco was larger, because a larger fraction of its C was in the lignin-like pool. N in rice hulls, corn and wheat residues was mostly recalcitrant, yet rice hulls did not cause N deficiency, because most of its C was recalcitrant too. The soluble components of the residues had strong short-term effects on available N in soil, but the cellulose-like pool was equally important for short and medium-term effects. Soluble and cellulose-like C were 29 and 42% of total C, respectively, in corn and 7 and 50% in wheat. Maximal net inorganic N losses, measured in both residue treatments after 2 weeks, were 42 mg g-1 C applied as corn and 31 mg g-1C applied as wheat, or 84 and 110 mg g-1 decomposed C of corn and wheat, respectively. Rice hulls immobilized N slowly, but by the end of 24 weeks all three residues immobilized 26-27mgNkg -1C applied. The different dynamics of N immobilization demonstrated the need to determine the decomposability of C and N rather than their total contents in plant residues. © 2003 Elsevier Ltd. All rights reserved.
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Rates of decomposition of plant residues and available nitrogen in soil, related to residue composition through simulation of carbon and nitrogen turnover
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Hadas, A., Inst. Soil, Water and Environ. Sci., A.R.O., Volcani Center, Bet-Dagan 50250, Israel
Kautsky, L., Inst. Soil, Water and Environ. Sci., A.R.O., Volcani Center, Bet-Dagan 50250, Israel
Goek, M., Department of Soil Science, Cukurova University, Adana, Turkey
Kara, E.E., Department of Environment, Faculty of Engineering, Nigde University, Nigde, Turkey
Rates of decomposition of plant residues and available nitrogen in soil, related to residue composition through simulation of carbon and nitrogen turnover
The dynamics of inorganic N in soil following the application of plant residues depends on their composition. We assumed that all plant materials are composed of similar components, each decomposing at a specific rate, but differ in the proportions of the various components. The NCSOIL model that simulates C and N turnover in soil was used to link the rates of residue decomposition to their composition, defined as soluble, cellulose-like and lignin-like C and N, and thereby integrate short and long-term effects of residues on available N dynamics in soil. Five plant residues in a wide range of C:N ratios were incubated in soil for 24 weeks at 30°C, during which C and N mineralization were measured. The materials with large C:N ratios (corn, rice hulls and wheat straw) were also incubated with NH4+-N to avoid N deficiency. The residues were analyzed for total and soluble C and N. The partitioning of insoluble C and N between cellulose- and lignin-like pools was optimized by best fit of simulated C and N mineralization to measured results. The decomposition rate constants of the soluble and lignin-like pools were assumed to be 1.0 and 10-5d-1, respectively, and that of the cellulose-like pool, obtained by model optimization against mineralization of cellulose with NH4+-N in soil, was 0.051d -1. The optimized, kinetically defined lignin-like pool of all residues was considerably larger than lignin contents normally found in plant residues by the Van Soest procedure. Gross N mineralization of tobacco and rape residues was similar, but N recovery from tobacco was larger, because a larger fraction of its C was in the lignin-like pool. N in rice hulls, corn and wheat residues was mostly recalcitrant, yet rice hulls did not cause N deficiency, because most of its C was recalcitrant too. The soluble components of the residues had strong short-term effects on available N in soil, but the cellulose-like pool was equally important for short and medium-term effects. Soluble and cellulose-like C were 29 and 42% of total C, respectively, in corn and 7 and 50% in wheat. Maximal net inorganic N losses, measured in both residue treatments after 2 weeks, were 42 mg g-1 C applied as corn and 31 mg g-1C applied as wheat, or 84 and 110 mg g-1 decomposed C of corn and wheat, respectively. Rice hulls immobilized N slowly, but by the end of 24 weeks all three residues immobilized 26-27mgNkg -1C applied. The different dynamics of N immobilization demonstrated the need to determine the decomposability of C and N rather than their total contents in plant residues. © 2003 Elsevier Ltd. All rights reserved.
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