Soil labile (biologically active) organic carbon fractions under different crop rotation systems in Jiangsu Province, China, were investigated after 10 years of rotation. The rotation systems, including green manureri...Soil labile (biologically active) organic carbon fractions under different crop rotation systems in Jiangsu Province, China, were investigated after 10 years of rotation. The rotation systems, including green manurerice-rice (GmRR), wheat-rice-rice (WRR), wheat-rice (WR) and wheat/corn intercrop-rice (WCR) rotations,were established on paddy soils using a randomized complete block design with three replicates. The total organic carbon (TOC), total nitrogen (TN) and water-soluble organic carbon (WSOC) in the soils under different systems were greater in the GmRR and WRR than in the WR and WCR rotation systems because the soils under triple cropping often received more crop residues than the soils under double cropping. Both the WSOC and the microbial biomass carbon (MBC) contents in the soils of the GmRR rotation system were significantly greater than those in the other crop rotation systems, which was due to the return of green manure to the fields of the GmRR rotation system. The results of a 13C nuclear magnetic resonance (13C-NMR) analysis indicated that the structural characteristics of soil WSOC were similar under the four crop rotation systems with carbohydrates and long-chain aliphatics being the major components. Correlation analysis showed that the content of the WSOC was positively correlated with that of the MBC (P ＜0.01),and all had significantly positive correlations with TOC and TN. The coefficients of variation (CVs) for WSOC and WSOC/TOC were greater than the other indices (e.g, MBC, TOC and TN), suggesting that WSOC in the soils was more sensitive to these rotation systems. The results above indicated that the soil amended with green manure could not only increase the usable C source for soil microorganisms, but could also enhance soil organic matter content; hence, rotation with green manure would be a good strategy for sustainable agriculture.展开更多
The crop rotation system in organic farming is a determinant factor to accumulate and preserve soil organic matter(SOM),and in depth knowledge on its effects is still lacking.Tillage intensity in particular is crucial...The crop rotation system in organic farming is a determinant factor to accumulate and preserve soil organic matter(SOM),and in depth knowledge on its effects is still lacking.Tillage intensity in particular is crucial to maintain soil aggregates and protect SOM from degradation.The evolution of SOM was tested in two adjacent fields under two different rotation cropping systems(low-intensity tillage and high-intensity tillage),and the effect of a further cultivation of legume in both fields was evaluated using ^(13)carbon(C)-nuclear magnetic resonance(NMR)and elemental analysis of samples isolated through combined aggregate size and density fractionation.The two adjacent fields had been managed using the following organic farming methods for 13 seasons since 1998:i)alfalfa-based,with nitrogen(N)enrichment and low-frequency tillage with alfalfa(Medicago sativa)(9 seasons),winter wheat(Triticum durum)(3 seasons),and broad bean(Vicia faba)(1 season)and ii)cereal-based,with N depletion and annual tillage with barley(Hordeum vulgare)(7 seasons),sunflower(Helianthus annuus)(2 seasons),broad bean(Vicia faba)(3 seasons),and bare fallow(1 season).Soil sampling was carried out at the end of the 13-year rotation(T0,November 2011)and after winter wheat and chickpea cultivation in both fields over two subsequent years(T1,July 2013).Bulk organic C was significantly higher in the alfalfa-based system than in the cereal-based system at both T0 and T1,with SOM occluded in soil aggregates and associated with mineral particles.In terms of the macroaggregates heavy fraction at T0,the alfalfa-based field contained twice the organic C of that in the cereal-based field,as well as three times the organic C in the occluded particulate organic matter(POM).The occluded POM(oPOM)had a lower aryl/O-alkyl C ratio in the alfalfa-based system than in the cereal-based system,suggesting that oPOM undergoes a lower degree of decomposition during low-intensity management.The aryl/O-alkyl C ratios of the macro-and microaggregate oPOM decreased from T0 to T1 in the cereal-based system,suggesting increased protection of these fractions by soil aggregates.Thus,including legumes in crop rotation appears to positively affect the accumulation of SOM associated with mineral particles and within soil aggregates.展开更多
基金Project supported by the National Key Basic Research Support Foundation (NKBRSF) of China (No. G1999011809) the National Natural Science Foundation of China (No. 49871044).
文摘Soil labile (biologically active) organic carbon fractions under different crop rotation systems in Jiangsu Province, China, were investigated after 10 years of rotation. The rotation systems, including green manurerice-rice (GmRR), wheat-rice-rice (WRR), wheat-rice (WR) and wheat/corn intercrop-rice (WCR) rotations,were established on paddy soils using a randomized complete block design with three replicates. The total organic carbon (TOC), total nitrogen (TN) and water-soluble organic carbon (WSOC) in the soils under different systems were greater in the GmRR and WRR than in the WR and WCR rotation systems because the soils under triple cropping often received more crop residues than the soils under double cropping. Both the WSOC and the microbial biomass carbon (MBC) contents in the soils of the GmRR rotation system were significantly greater than those in the other crop rotation systems, which was due to the return of green manure to the fields of the GmRR rotation system. The results of a 13C nuclear magnetic resonance (13C-NMR) analysis indicated that the structural characteristics of soil WSOC were similar under the four crop rotation systems with carbohydrates and long-chain aliphatics being the major components. Correlation analysis showed that the content of the WSOC was positively correlated with that of the MBC (P ＜0.01),and all had significantly positive correlations with TOC and TN. The coefficients of variation (CVs) for WSOC and WSOC/TOC were greater than the other indices (e.g, MBC, TOC and TN), suggesting that WSOC in the soils was more sensitive to these rotation systems. The results above indicated that the soil amended with green manure could not only increase the usable C source for soil microorganisms, but could also enhance soil organic matter content; hence, rotation with green manure would be a good strategy for sustainable agriculture.
基金funded by the Department of Agricultural,Food and Environmental Sciences(D3 A),Polytechnic University of Marche,Ancona,Italy。
文摘The crop rotation system in organic farming is a determinant factor to accumulate and preserve soil organic matter(SOM),and in depth knowledge on its effects is still lacking.Tillage intensity in particular is crucial to maintain soil aggregates and protect SOM from degradation.The evolution of SOM was tested in two adjacent fields under two different rotation cropping systems(low-intensity tillage and high-intensity tillage),and the effect of a further cultivation of legume in both fields was evaluated using ^(13)carbon(C)-nuclear magnetic resonance(NMR)and elemental analysis of samples isolated through combined aggregate size and density fractionation.The two adjacent fields had been managed using the following organic farming methods for 13 seasons since 1998:i)alfalfa-based,with nitrogen(N)enrichment and low-frequency tillage with alfalfa(Medicago sativa)(9 seasons),winter wheat(Triticum durum)(3 seasons),and broad bean(Vicia faba)(1 season)and ii)cereal-based,with N depletion and annual tillage with barley(Hordeum vulgare)(7 seasons),sunflower(Helianthus annuus)(2 seasons),broad bean(Vicia faba)(3 seasons),and bare fallow(1 season).Soil sampling was carried out at the end of the 13-year rotation(T0,November 2011)and after winter wheat and chickpea cultivation in both fields over two subsequent years(T1,July 2013).Bulk organic C was significantly higher in the alfalfa-based system than in the cereal-based system at both T0 and T1,with SOM occluded in soil aggregates and associated with mineral particles.In terms of the macroaggregates heavy fraction at T0,the alfalfa-based field contained twice the organic C of that in the cereal-based field,as well as three times the organic C in the occluded particulate organic matter(POM).The occluded POM(oPOM)had a lower aryl/O-alkyl C ratio in the alfalfa-based system than in the cereal-based system,suggesting that oPOM undergoes a lower degree of decomposition during low-intensity management.The aryl/O-alkyl C ratios of the macro-and microaggregate oPOM decreased from T0 to T1 in the cereal-based system,suggesting increased protection of these fractions by soil aggregates.Thus,including legumes in crop rotation appears to positively affect the accumulation of SOM associated with mineral particles and within soil aggregates.
