Effects of Different Land Use Types on Soil Organic Carbon and Carbon Management Index in Karst Area

[Objective] The aim was to reveal changes of soil organic matter fraction and their corresponding carbon management indexes as affected by different land use types.[Method]Soil organic carbon,active soil organic carbon and soil carbon management index（CMI）of different land use types in Guilin Maocun karst area were studied.Sampling with field investigation and laboratory testing was carried out.Heavy potassium chromate method was adopted to determine soil organic matter.333 mmol/L KMnO4 oxidation method was used to determine active organic carbon.[Result]With active soil organic matter increasing,the differences of CMI between different land use types were bigger.The CMI value of different land uses was shrubforest paddy fielddry farmland.The statistical analysis showed that labile organic matter was related with major soil properties at a significant level.[Conclusion]Labile organic matter could be used to reveal the influence of different land use types on soil organic matter and carbon management index in karst area.

Impacts of Rice Field Winter Planting on Soil Organic Carbon and Carbon Management Index

To tackle with the problem of prevailing farmland abandonment in winter,5 treatments includes Chinese milk vetch-double cropping rice(CRR),rape-double cropping rice(RRR),garlic-double cropping rice(GRR),winter crop multiple cropping rotation(ROT),winter fallow control(WRR)were set up.By measuring soil total organic carbon,active organic carbon and its components and calculating the soil carbon pool management index in 0~15 cm and 15~30 cm soil layers in the early and late rice ripening stage.The effects of different winter planting patterns on the changes of soil organic carbon and carbon pool management index were discussed.In order to provide theoretical basis for the optimization and adjustment of winter planting pattern of double cropping rice field in the middle reaches of Yangtze River.The results showed that soil total organic carbon,active organic carbon and its components in different winter cropping patterns were increased,and ROT and CRR treatments were more beneficial to the accumulation of soil total organic carbon,active organic carbon and its components as well as the improvement of soil carbon pool management index,which should be preferred in the adjustment of cropping patterns.

Soil Carbon Pool Management Index under Different Straw Retention Regimes

[Objective] To clarify the effects of different straw retention regimes on soil fertility in double cropping paddy field. [Method] The effects of different straw reten- tion regimes on total organic carbon （CToc）, active carbon （CA） and mineralized carbon （CM） were analyzed, and carbon pool active （A）, carbon pool active index （A/）, carbon pool index （CPI） and carbon pool management index （CPMi） for each treat- ment were calculated. [Result] Compared with the unfertilized treatment （CK）, CToc, CA, CM and the available ratio of soil carbon were increased in the treatment of re- turning early season and late season rice straws to field. With the same nutrient application, CToc, CA and the available ratio of soil carbon in the field with straw re- turned to field were higher than that of straw incineration and no straw returning, and the change in soil CA content was more significant. The difference in CPMI be- tween different treatments reached significant or very significant level, and the value was in the order of straw directly returned to field 〉 straw returned to field after in- cineration 〉 no straw returned to field. [Conclusion] This study provided theoretical bases for the increase of soil CA content and soil fertility in double rice fields.

Fertilization Affects Biomass Production of Suaeda salsa and Soil Organic Carbon Pool in East Coastal Region of China

Land use practice significantly affects soil properties. Soil is a major sink for atmospheric carbon, and soil organic carbon （SOC） is considered as an essential indicator of soil quality. The objective of this study was to assess the effects of N and P applied to Suaeda salsa on biomass production, SOC concentration, labile organic carbon （LOC） concentration, SOC pool and carbon management index （CMI） as well as the effect of the land use practice on soil quality of coastal tidal lands in east coastal region of China. The study provided relevant references for coastal exploitation, tidal land management and related study in other countries and regions. The field experiment was laid out in a randomized complete block design, consisting of four N-fertilization rates （0 （NO）, 60 （N1）, 120 （N2） and 180 kg ha-1 （N3））, three P-fertilization rates （0 （P0）, 70 （P1） and 105 kg ha-~ （P2）） and bare land without vegetation. N and P applied to S. salsa on coastal tidal lands significantly affected biomass production （above-ground biomass and roots）, bulk density （Pb）, available N and P, SOC, LOC, SOC pool and CMI. Using statistical analysis, significantly interactions in N and P were observed for biomass production and the dominant factor for S. salsa production was N in continuous 2-yr experiments. There were no significant interactions between N and P for SOC concentration, LOC concentration and SOC pool. However, significant interaction was obtained for CMI at the 0-20 cm depth and N played a dominant role in the variation of CMI. There were significant improvements for soil measured attributes and parameters, which suggested that increasing the rates of N and P significantly decreased Pb at the 0-20 cm depth and increased available N and P, SOC, LOC, SOC pool as well as CMI at both the 0-20 and 20-40 cm depth, respectively. By correlation analysis, there were significantly positive correlations between biomass （above- ground biomass and roots） and SOC as well as LOC in 2010 and 2011 across all soil depth, respectively. The treatment with N at 180 kg ha-~ and P at 105 kg ha-1 was superior to the other treatments. The results from the 2-yr continuous experiments indicated that, in short-term, there were a few accumulation of SOC and LOC concentrations by means of N and P application to S. salsa, whereas in the long run, S. salsa with N and P application was recommended for coastal tidal lands because of its great potential of carbon sequestration, improvements of soil nutrition status and promotion of soil quality.

Reduced tillage with residue retention improves soil labile carbon pools and carbon lability and management indices in a seven-year trial with wheat-mung bean-rice rotation

Soil total organic carbon(TOC)is a composite indicator of soil quality with implications for crop production and the regulation of soil ecosystem services.Research reports on the dynamics of TOC as a consequence of soil management practices in subtropical climatic conditions,where microbial carbon(C)loss is high,are very limited.The objective of our study was to evaluate the impact of seven years of continuous tillage and residue management on soil TOC dynamics(quantitative and qualitative)with respect to lability and stratification under an annual wheat-mung bean-rice cropping sequence.Composite soil samples were collected at 0-15 and 15-30 cm depths from a three-replicate split-plot experiment with tillage treatment as the main plots and crop residue levels as the sub-plots.The tillage treatments included conventional tillage(CT)and strip tillage(ST).Residue levels were high residue level(HR),30%of the plant height,and low residue level(LR),15%.In addition to TOC,soil samples were analyzed for particulate organic C(POC),permanganate oxidizable C(POXC),basal respiration(BR),specific maintenance respiration rate(qCO_(2)),microbial biomass C(MBC),potentially mineralizable C(PMC),and TOC lability and management indices.The ST treatment significantly increased the TOC and labile C pools at both depths compared with the CT treatment,with the effect being more pronounced in the surface layer.The HR treatment increased TOC and labile C pools compared with the LR treatment.The ST+HR treatment showed significant increases in MBC,metabolic quotient(qR),C pool index(CPI),C lability index(CL_(I)),and C management index(CMI),indicating improved and efficient soil biological activities in such systems compared with the CT treatment.Similarly,the stratification values,a measure of soil quality improvement,for POC and MBC were>2,indicating improved soil quality in the ST+HR treatment compared with the CT treatment.The ST+HR treatment not only significantly increased the contents of TOC pools,but also their stocks.The CMI was correlated with qCO_(2),BR,and MBC,suggesting that these are sensitive indicators of early changes in TOC.The qCO_(2) was significantly higher in the CT+LR treatment and negatively correlated with MBC and CMI,indicating a biologically stressed soil condition in this treatment.Our findings highlight that medium-term reduced tillage with HR management has profound consequences on soil TOC quality and dynamics as mediated by alterations in labile C pools.

Long-term fertilization and residue return affect soil stoichiometry characteristics and labile soil organic matter fractions

Ecological stoichiometry provides the possibility for linking microbial dynamics with soil carbon(C),nitrogen(N),and phosphorus(P)metabolisms in response to agricultural nutrient management.To determine the roles of fertilization and residue return with respect to ecological stoichiometry,we collected soil samples from a 30-year field experiment on residue return(maize straw)at rates of 0,2.5,and 5.0 Mg ha^-1 in combination with 8 fertilization treatments:no fertilizer(F0),N fertilizer,P fertilizer,potassium(K)fertilizer,N and P(NP)fertilizers,N and K(NK)fertilizers,P and K(PK)fertilizers,and N,P,and K(NPK)fertilizers.We measured soil organic C(SOC),total N and P,microbial biomass C,N,and P,water-soluble organic C and N,KMnO4-oxidizabIe C(KMnO4-C),and carbon management index(CMI).Compared with the control(F0 treatment without residue return),fertilization and residue return significantly increased the KMn〇4-C content and CMI.Furthermore,compared with the control,residue return significantly increased the SOC content.Moreover,the NPK treatment with residue return at 5.0 Mg ha^-1 significantly enhanced the C:N,C:P,and N:P ratios in the soil,whereas it significantly decreased the C:N and C:P ratios in soil microbial biomass.Therefore,NPK fertilizer application combined with residue return at 5.0 Mg ha^-1 could enhance the SOC content through the stoichiometric plasticity of microorganisms.Residue return and fertilization increased the soil C pools by directly modifying the microbial stoichiometry of the biomass that was C limited.

No-till and conservation agriculture in the United States:An example from the David Brandt farm,Carroll,Ohio

No-till(NT)farming(conservation agriculture)began in the US in the 1960s.The state of Ohio has a university research location that began no-till research in 1962.A few innovative Ohio farmers,including NT pioneers David Brandt and Bill Richards,were early adopters of the new conservation practice.Initially,no-till was most successful on sloping,well drained soils,then with improvements to the system,including cover crops,it became more widely adopted on all soil types.David Brandt was an enthusiastic learner and teacher of no-till practices,working with chemical company representatives and Cooperative Extension Specialists to demonstrate the system.David Brandt’s cooperation with Ohio State University researchers continues to provide a valuable site for studying the long term changes in soil health and ecosystem services.Results showed that total microbial biomass as one of the soil biological health indicators significantly increased with an associated decrease in carbon(C)loss under NT compared with conventional tilled soil(CT).Under NT,there was significantly higher total C and total N compared to CT.Active C,as a composite measure of soil health,significantly increased with NT.When cover crops,especially cover crop cocktail mixes,were used,NT substantially improved soil health.Long-term NT with cover crop cocktail mixes significantly increased the soil aggregate stability,compared with CT.The overall rate of C sequestration by NT suggested that the soils on the Brandt farm act as a consistent sink of atmospheric CO2 although this tends to level off after about 20 years.The Brandt farm showed that crop yields are increased under long-term NT with cover crops mixes.Results suggested that starting with a cover crop when switching from CT to NT,is more likely to ensure success and to maintain economic crop yields.Another early adopter,Bill Richards,from Circleville,Ohio,also became a national leader and promoter of no-till farming.He served as head of the United States Department of Agriculture’s Natural Resources Conservation Service in the early 1990s and instituted a program that led to rapid expansion of no-till.He advises that farmers who follow conservation agriculture principles need to be more proactive,from local level to national levels,to influence policy decisions that can lead to robust improvement in soil health.