Four kinds of plant materials (astragalus, azolla, rice straw and water hyacinth) were allowed to decompose for 10 years in two soils with different mineralogical characteristics in fields under upland and submerged c...Four kinds of plant materials (astragalus, azolla, rice straw and water hyacinth) were allowed to decompose for 10 years in two soils with different mineralogical characteristics in fields under upland and submerged conditions. Greater amounts of C and N from azolla were retained in soils throughout the 10-year experimental period compared to those from the other plant materials. The residual C Of all the plant materials in the two soils under upland conditions mineralized st rates corresponding to half-lives between 4.4-6.6 years,while the corresponding figures for thine under submerged conditions were between 6.5-13.1 years. Minerallization of residual organic N followed the same pattern as residual C. Compared to residual C, however, the mineralization rates of residual organic N in most cases were significantly lower and the percentages of added N regained in sons were higher. More N from plat materials was retained in the yellow-brown soil than in the red soil, but no consistent differences in the amounts of C from plant materials and in the mineralization rates of both residual C and residual organic N between the two soils could be found.展开更多
Pot experimeats were carried out to estimate N2 fixation by vetch, milk vetch, sickle alfalfa and broadbean in pure stand using a 15N-labelled soil. Winter wheat was used as the non-fixing control. The 15N-labelled so...Pot experimeats were carried out to estimate N2 fixation by vetch, milk vetch, sickle alfalfa and broadbean in pure stand using a 15N-labelled soil. Winter wheat was used as the non-fixing control. The 15N-labelled soil used was prepared by growing corn-wheat-corn successively on a nearly organic-matter-free Xiashu loess supplemented with adequate amounts of (15NH4)aSO4, P, K and micronutrients, then incorporating these 15N-labelled plant msterials into the soil after each harvest, and allowing the plant materials to be decomposed aerobically for 410 d after incorporation of the plant material of the third crop. The 15N enrichment of wheat plant-N varied slightly with organs,with a maximum difference of 9.8%. Based on 15N enrichment of soil N inferred from the mean value of the 15N enrichment in different organs of wheat 79%-91% of total N in the tops and 67%-74% of total N in the roots of legumes studied were derived from atmosphere. Estimate by isotope dilution method was in good agreement with that by the conventional difference method provided values obtained by the latter were corrected for seed N, and also with that from the measurement of N accumulated in the tops of the legumes.展开更多
Water-soluble, nondialyzable Maillard polymers were prepared by reacting D-xylose with 15N-glycine (and/or glycine) at 68 ℃ and pH 8.0 at equimolar concentrations of 1, 0.5 and 0.1 mol L-1, respectively,for 13 days a...Water-soluble, nondialyzable Maillard polymers were prepared by reacting D-xylose with 15N-glycine (and/or glycine) at 68 ℃ and pH 8.0 at equimolar concentrations of 1, 0.5 and 0.1 mol L-1, respectively,for 13 days and partitioned into acid-insoluble (MHA) and acid-soluble (MFA) fractions. The nitrogen forms in these polymers were studied by using the 15N cross polarization-magic angle spinning nuclear magnetic resonance (CPMAS NMR) technique in combination with chemical methods. The 15N nuclear magnetic resonance (NMR) data showed that while the yield, especially the MHA/MFA ratio, varied considerably with the concentrations of the reactants, the nitrogen distribution patterns of these polymers were quite similar.From 65% to 70% of nitrogen in them was in the secondary amide and/or indole form with 24%~25% present as aliphatic and/or aromatic ammes and 5% to 11% as pyrrole and/or pyrrole-like nitrogen. More than half (50%~77%) of the N in these polymers were nonhydrolyzable. The role of Maillard reaction in the formation of nonhydrolyzable nitrogen in soil organic matter is discussed.展开更多
Chemical characteristics of humic substances in soils with different mineralogical characteristics and under different utilization patterns in Zhangpu, Fujian Province,together with two pairs of cultiwted soils in Nor...Chemical characteristics of humic substances in soils with different mineralogical characteristics and under different utilization patterns in Zhangpu, Fujian Province,together with two pairs of cultiwted soils in North China Plain were studied by chemical analysis,visible and IR spectroscopy and 13C NMR spectrometry.For soils in Zhangpu the HA/FA ratio and both the aromaticity and the degree of hundfication of HA were higher in soils with montmorillonite as the predominant clay mineral than in thO6e with kaolinite as the predominant clay mineral, provided these soils were under the same utilisstion pattern. While for eaCh pair of soils with similar mineralogical characteristics the HA/FA ratio was higher and the C/H ratio and the content of carboxyl group of HA were lower in paddy soil than in upland soil.Among the upland soils(or paddy soils) studied the HA/FA ratio of soil in Zhangpu with kaollnite as the predominant clay mineral was the lowest,and that of soil in Zhangpu with montmorillonite aa the predominant clay mineral was the highest.It was concluded that the presence of moatmorillonite favored the formation and maturation of humic acid.展开更多
Phenolic polymers synthesized by reactions of p-benzoquinone with 15N-labelled protein or(15NH4)2SO4 were studied by using 15N CP-MAS NMR technique in combination with chemical approaches.Results showed that more than...Phenolic polymers synthesized by reactions of p-benzoquinone with 15N-labelled protein or(15NH4)2SO4 were studied by using 15N CP-MAS NMR technique in combination with chemical approaches.Results showed that more than 80% of nitrogen in quinone-protein polymers was in the form of amide with some present as aromatic and/or aliphatic alone and less than 10% of nitrogen occurred as heterocyclic N.The nitrogen distribution in the non-hydrolyzable residue of the quinone-protein polymers was basically similar to that of soil humic acid reported in literature with the exception that a higher proportion of N as heterocyclic N and aromatic amine and a lower proportion of N as amide and aliphatic amine were found in the former than in the latter. More than 70% of total nitrogen in quinones(NH4)2SO4 polymer was acid resist ant,of which about 53% occurred as pyrrole,nitrile and imino type N.The possible roles of the reactions of phenols or quinones with proteins in the formation of humic acid,especially the non-hydrolyzable nitrogen in humic acid,are discussed.展开更多
文摘Four kinds of plant materials (astragalus, azolla, rice straw and water hyacinth) were allowed to decompose for 10 years in two soils with different mineralogical characteristics in fields under upland and submerged conditions. Greater amounts of C and N from azolla were retained in soils throughout the 10-year experimental period compared to those from the other plant materials. The residual C Of all the plant materials in the two soils under upland conditions mineralized st rates corresponding to half-lives between 4.4-6.6 years,while the corresponding figures for thine under submerged conditions were between 6.5-13.1 years. Minerallization of residual organic N followed the same pattern as residual C. Compared to residual C, however, the mineralization rates of residual organic N in most cases were significantly lower and the percentages of added N regained in sons were higher. More N from plat materials was retained in the yellow-brown soil than in the red soil, but no consistent differences in the amounts of C from plant materials and in the mineralization rates of both residual C and residual organic N between the two soils could be found.
文摘Pot experimeats were carried out to estimate N2 fixation by vetch, milk vetch, sickle alfalfa and broadbean in pure stand using a 15N-labelled soil. Winter wheat was used as the non-fixing control. The 15N-labelled soil used was prepared by growing corn-wheat-corn successively on a nearly organic-matter-free Xiashu loess supplemented with adequate amounts of (15NH4)aSO4, P, K and micronutrients, then incorporating these 15N-labelled plant msterials into the soil after each harvest, and allowing the plant materials to be decomposed aerobically for 410 d after incorporation of the plant material of the third crop. The 15N enrichment of wheat plant-N varied slightly with organs,with a maximum difference of 9.8%. Based on 15N enrichment of soil N inferred from the mean value of the 15N enrichment in different organs of wheat 79%-91% of total N in the tops and 67%-74% of total N in the roots of legumes studied were derived from atmosphere. Estimate by isotope dilution method was in good agreement with that by the conventional difference method provided values obtained by the latter were corrected for seed N, and also with that from the measurement of N accumulated in the tops of the legumes.
文摘Water-soluble, nondialyzable Maillard polymers were prepared by reacting D-xylose with 15N-glycine (and/or glycine) at 68 ℃ and pH 8.0 at equimolar concentrations of 1, 0.5 and 0.1 mol L-1, respectively,for 13 days and partitioned into acid-insoluble (MHA) and acid-soluble (MFA) fractions. The nitrogen forms in these polymers were studied by using the 15N cross polarization-magic angle spinning nuclear magnetic resonance (CPMAS NMR) technique in combination with chemical methods. The 15N nuclear magnetic resonance (NMR) data showed that while the yield, especially the MHA/MFA ratio, varied considerably with the concentrations of the reactants, the nitrogen distribution patterns of these polymers were quite similar.From 65% to 70% of nitrogen in them was in the secondary amide and/or indole form with 24%~25% present as aliphatic and/or aromatic ammes and 5% to 11% as pyrrole and/or pyrrole-like nitrogen. More than half (50%~77%) of the N in these polymers were nonhydrolyzable. The role of Maillard reaction in the formation of nonhydrolyzable nitrogen in soil organic matter is discussed.
文摘Chemical characteristics of humic substances in soils with different mineralogical characteristics and under different utilization patterns in Zhangpu, Fujian Province,together with two pairs of cultiwted soils in North China Plain were studied by chemical analysis,visible and IR spectroscopy and 13C NMR spectrometry.For soils in Zhangpu the HA/FA ratio and both the aromaticity and the degree of hundfication of HA were higher in soils with montmorillonite as the predominant clay mineral than in thO6e with kaolinite as the predominant clay mineral, provided these soils were under the same utilisstion pattern. While for eaCh pair of soils with similar mineralogical characteristics the HA/FA ratio was higher and the C/H ratio and the content of carboxyl group of HA were lower in paddy soil than in upland soil.Among the upland soils(or paddy soils) studied the HA/FA ratio of soil in Zhangpu with kaollnite as the predominant clay mineral was the lowest,and that of soil in Zhangpu with montmorillonite aa the predominant clay mineral was the highest.It was concluded that the presence of moatmorillonite favored the formation and maturation of humic acid.
文摘Phenolic polymers synthesized by reactions of p-benzoquinone with 15N-labelled protein or(15NH4)2SO4 were studied by using 15N CP-MAS NMR technique in combination with chemical approaches.Results showed that more than 80% of nitrogen in quinone-protein polymers was in the form of amide with some present as aromatic and/or aliphatic alone and less than 10% of nitrogen occurred as heterocyclic N.The nitrogen distribution in the non-hydrolyzable residue of the quinone-protein polymers was basically similar to that of soil humic acid reported in literature with the exception that a higher proportion of N as heterocyclic N and aromatic amine and a lower proportion of N as amide and aliphatic amine were found in the former than in the latter. More than 70% of total nitrogen in quinones(NH4)2SO4 polymer was acid resist ant,of which about 53% occurred as pyrrole,nitrile and imino type N.The possible roles of the reactions of phenols or quinones with proteins in the formation of humic acid,especially the non-hydrolyzable nitrogen in humic acid,are discussed.
