• Authors:
    • Ouyang, Z.
    • Wang, X.
    • Wang, S.
  • Source: Journal of Environmental Sciences
  • Volume: 24
  • Issue: 3
  • Year: 2012
  • Summary: Soil organic carbon (SOC) and total nitrogen (TN) contents as well as their relationships with site characteristics are of profound importance in assessing current regional, continental and global soil C and N stocks and potentials for C sequestration and N conservation to offset anthropogenic emissions of greenhouse gases. This study investigated contents and distribution of SOC and TN under different land uses, and the quantitative relationships between SOC or TN and site characteristics in the Upstream Watershed of Miyun Reservoir, North China. Overall, both SOC and TN contents in natural secondary forests and grasslands were much higher than in plantations and croplands. Land use alone explained 37.2% and 38.4% of variations in SOC and TN contents, respectively. The optimal models for SOC and TN, achieved by multiple regression analysis combined with principal component analysis (PCA) to remove the multicollinearity among site variables, showed that elevation, slope, soil clay and water contents were the most significant factors controlling SOC and TN contents, jointly explaining 70.3% of SOC and 67.1% of TN contents variability. Only does additional 1.9% and 3% increase in the interpretations of SOC and TN contents variability respectively when land use was added to regressions, probably due to environment factors determine land use. Therefore, environmental variables were more important for SOC and TN variability than land use in the study area, and should be taken into consideration in properly evaluating effects of future land use changes on SOC and TN on a regional scale.
  • Authors:
    • Six, J.
    • Tian,Jing
    • Kuzyakov, Y.
    • Lee, J.
    • Chen, H.
    • Christie, P.
    • Li, X.
    • Zhang, F.
    • Fan, M.
    • Yan, Y.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 150
  • Year: 2012
  • Summary: The conversion from cereal fields to vegetable production in the last three decades represents a significant shift in land use in China. Here, we studied the effects of conversion form cereal fields to vegetable production in north China on soil organic carbon (SOC) and total nitrogen (TN) in both bulk soil and soil aggregates. We used two approaches: (1) measurements of paired soil samples from wheat (Triticum aestivum L) - maize (Zea mays L) fields and adjacent greenhouses vegetable fields in three vegetable production areas representing various management intensities in terms of C and N inputs and frequency of tillage: (2) fractionating soil to distinguish intra-aggregate particulate organic matter (iPOM) and organo-mineral complexes (silt + clay). Our results indicated that converting cereal fields to greenhouse vegetable production with intermediate and high management intensity led to increases in SOC and TN and decreases in C:N ratios in the top soil. The accumulation rates of C and N in the surface soil (0-30 cm) were estimated to be 1.37 Mg C ha(-1) yr(-1) and 0.21 Mg N ha(-1) yr(-1) over an average period of 8 years after cereal fields to greenhouse vegetable production conversion. At the soil aggregate level, only the coarse (>250 mu m) and fine (53-250 mu m) iPOM fraction contributed to the increases in soil C (e.g., 49% and 51% of total C increases, respectively), while the coarse and fine iPOM, and silt + clay fraction accounted for 22%, 30% and 48%, respectively, of total N increases. This illustrates how the addition of readily available C (manure) and N (manure and inorganic N) leads to a temporary stabilization of C in relatively labile SOM fractions, but to a preferential stabilization of N in organo-mineral SOM fractions. In conclusion, the conversion to highly intensive vegetable systems in China leads to marked differences in C and N stabilization dynamics.
  • Authors:
    • Zhang, H.
    • Chen, F.
    • Kong, F.
    • Wei, Y.
    • Zhang, M.
  • Source: Transactions of the Chinese Society of Agricultural Engineering
  • Volume: 28
  • Issue: 6
  • Year: 2012
  • Summary: Distribution of soil organic carbon in different soil layer can be transformed by tillage practices, and then soil carbon storage was changed. The four indices of soil organic carbon (SOC), soil carbon density (SCD), soil respiration (SR) and biomass carbon (BC) were selected to verify the adaptability of DNDC model in North China based on model adaptation and then the model was used to simulate local dynamic change of soil carbon storage (SCS) and characteristics of greenhouse gas emission. The result showed that there was a high similarity between simulated values and observed values and the model proposed was suitable to apply to the simulation research of soil organic carbon for winter wheat-summer corn in North China. SOC and SCS simulated by the model increased from 2001-2010, and simulated data in the next 100 years showed that SOC with rotary tillage (RT), conventional tillage (CT) and no-tillage (NT) showed a severe rising tendency in the first 15 years, and rising tendency of NT could sustain for 40 years. By comparing changes of soil carbon storage for 100 years between each treatment, it was found that SCS values with CT were the highest in the first 20 years and SCS values with NT was the highest after first 20 years. The sequence of global warming potential (GWP) for each treatment was CT > RT > NT. The results showed that DNDC model could work well for winter wheat-summer corn in North China, and NT was beneficial to increase SCS and decrease GWP of farmland in the long run. It provides a reference for fixing carbon and reducing discharge of winter wheat-summer corn in North China.
  • Authors:
    • Zhang, X.
    • Zheng, J.
    • Li, L.
    • Hussain, Q.
    • Pan, G.
    • Liu, Y.
    • Zhang, A.
  • Source: Plant and Soil
  • Volume: 351
  • Issue: 1-2
  • Year: 2012
  • Summary: A field experiment was conducted to investigate the effect of biochar on maize yield and greenhouse gases (GHGs) in a calcareous loamy soil poor in organic carbon from Henan, central great plain, China. Biochar was applied at rates of 0, 20 and 40 t ha(-1) with or without N fertilization. With N fertilization, urea was applied at 300 kg N ha(-1), of which 60% was applied as basal fertilizer and 40% as supplementary fertilizer during crop growth. Soil emissions of CO2, CH4 and N2O were monitored using closed chambers at 7 days intervals throughout the whole maize growing season (WMGS). Biochar amendments significantly increased maize production but decreased GHGs. Maize yield was increased by 15.8% and 7.3% without N fertilization, and by 8.8% and 12.1% with N fertilization under biochar amendment at 20 t ha(-1) and 40 t ha(-1), respectively. Total N2O emission was decreased by 10.7% and by 41.8% under biochar amendment at 20 t ha(-1) and 40 t ha(-1) compared to no biochar amendment with N fertilization. The high rate of biochar (40 t ha(-1)) increased the total CO2 emission by 12% without N fertilization. Overall, biochar amendments of 20 t ha(-1) and 40 t ha(-1) decreased the total global warming potential (GWP) of CH4 and N2O by 9.8% and by 41.5% without N fertilization, and by 23.8% and 47.6% with N fertilization, respectively. Biochar amendments also decreased soil bulk density and increased soil total N contents but had no effect on soil mineral N. These results suggest that application of biochar to calcareous and infertile dry croplands poor in soil organic carbon will enhance crop productivity and reduce GHGs emissions.
  • Authors:
    • Chen, C.
    • Yang, M.
    • Zhu, L.
  • Source: Journal of Agricultural Science
  • Volume: 4
  • Issue: 9
  • Year: 2012
  • Summary: Carbon sequestration in cropland soils which could be achieved through improved management practices (IPMs) represents an important opportunity to offset a portion of greenhouse gas emissions. North China is the main wheat and maize production region where many IMPs have been widely used during the last several decades, but the effect size and duration of IMPs on soil organic carbon (SOC) sequestration in wheat-maize double cropping system in this region is scarcely studied. In this study, a meta-analysis was conducted to compare the effect size and duration of four IMPs on SOC sequestration in wheat-maize double cropping system in north China. A total of 29 long-term experiments, consisting of 119 paired treatments were compiled in this analysis. The results indicated that the four IMPs of organic manure application (OM), organic manure combined with chemical fertilizer application (MF), straw return (SR) and reduced or no tillage (RNT) all had significant effects on SOC sequestration in the study area. On average, the IMPs of OM, MF, SR and RNT enhanced SOC density by 260, 328, 278 and 134 kg ha -1 yr -1, respectively. The effect duration of OM, MF, SR and RNT on SOC sequestration were about 48, 26, 22 and 18 years, respectively. Accumulation enhancements of SOC for OM, MF, SR and RNT over SOC sequestration period were about 34.7%, 36.1%, 22.0% and 12.7%, respectively. OM and MF could be the appropriate practices on SOC sequestration in wheat-maize double cropping system in the research area.
  • Authors:
    • Huang, S. M.
    • Yang, X. Y.
    • Zhang, W. J.
    • Wang, X. J.
    • Xu, M. G.
    • Cong, R. H.
    • Wang, B. R.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 93
  • Issue: 2
  • Year: 2012
  • Summary: Soil carbon dynamics would be influenced by fertilization management in the agro-ecosystem. In this study, we analyze carbon inputs and soil organic carbon (SOC) dynamics under wheat-corn double cropping system based on four long-term experimental sites in different climate zones of China. We examine soil carbon responses to various carbon inputs by using linear (S = aA - b) and non-linear () equations. The term S is the SOC change rate; a, the proportion of C inputs incorporated into soil; b, minimum change rate of SOC; S (M) , the asymptotic maximum value at SOC change rate approaching infinity (Mg C ha(-1) year(-1)); S (L) , the decomposition rate of SOC substrates, and K (S) , a constant value (or 'half-saturation constant'). The S value is fitted using linear equation with SOC data over the duration of the experiment. The annual C input (A) is estimated by measured crop biomass and C input from manure. Different amounts of balanced fertilization show little impact on the C inputs derived by plants, reaching to similar to.5 Mg C ha(-1) year(-1). The SOC change rate is much higher under the manure application than treatments with chemical fertilizers only. Statistical analysis shows that the linear and non-linear equations perform equally well (p < 0.01) within the experimental data interval. But the non-linear equation is more suitable for specific purpose. Using the non-linear equation, we can predict that minimum C input to maintain the current SOC level would be 0.33-1.32 Mg C ha(-1) year(-1) at the most sites but only 0.03 Mg C ha(-1) year(-1) at the Changping site. The chemical nitrogen and phosphate fertilization yield sufficient carbon biomass inputs to maintain the current SOC levels. However, to increase SOC at 1 Mg C ha(-1) year(-1), soils need over 10 Mg C ha(-1) year(-1) at most sites. Our results suggest that the increment of SOC stocks would be mainly related to the additional carbon inputs for the long-term perspectives.
  • Authors:
    • Chen, X.
    • Yang, X. D.
    • Anderson, N. J.
    • Dong, X. H.
    • Shen, J.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 7
  • Year: 2012
  • Summary: Floodplain lakes may play an important role in the cycling of organic matter at the landscape scale. For those lakes on the middle and lower reaches of the Yangtze (MLY) floodplain which are subjected to intense anthropogenic disturbance, carbon burial rates should, theoretically, be substantial due to the high nutrient input, increased primary production and high sediment accumulation rates. There are more than 600 lakes >1 km 2 on the Yangtze floodplain including 18 lakes >100 km 2 and most are shallow and eutrophic. 210Pb-dated cores were combined with total organic carbon (TOC) analyses to determine annual C accumulation rates (C AR; g C m -2 yr -1) and the total C stock (since ~1850). The sediment TOC content is relatively low with an average <2% in most lakes. C AR ranged from ~5 to 373 g C m -2 yr -1, resulting in C standing stocks of 0.60-15.3 kg C m -2 (mean: ~5 kg C m -2) since ~1850. A multicore study of Chaohu lake (770 km 2) indicated that spatial variability of C burial was not a significant problem for regional upscaling. The possible effect of changes in lake size and catchment land use on C burial was examined at Taibai lake and indicated that lake shrinkage and declining arable agriculture had limited effects on C AR. The organic C standing stock in individual lakes is, however, significantly dependent on lake size, allowing a simple linear scaling for all the MLY lakes. Total regional C sequestration was ~80 Tg C since ~1850, equivalent to ~11% of C sequestration by soils, but in ~3% of the land area. Shallow lakes from MLY are a substantial regional C sink, although strong mineralization occurs due to their shallow nature and their role as C sinks is threatened due to lake drainage.
  • Authors:
    • Wu,
    • Zhang, Y. M.
    • Hu, C. S.
    • Dong, W. X.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 94
  • Issue: 2-3
  • Year: 2012
  • Summary: No-tillage cropping can increase soil carbon (C) stocks and aggregation, and subsequently impact the internal nitrogen (N) cycle and gas loss. The N-15 pool dilution method was used to study gross N transformations, and relative proportions of nitrous oxide (N2O) emissions derived from denitrification versus nitrification-related processes under long-term tillage systems (no-tillage, rotary tillage and conventional tillage) in the North China Plain. In-field incubation experiments were repeated in successive growing seasons during April-November in 2007. Gross mineralization rates for rotary and mouldboard plough tillage (3.6 +/- A 0.3-10.6 +/- A 1.5 mg N kg(-1) days(-1)) were significantly higher than for no-tillage (1.7 +/- A 0.8-6.8 +/- A 1.1 mg N kg(-1) days(-1)). Gross mineralization was positively correlated with soil moisture and temperature, as well as with microbial biomass N and C. However, there was no consistent tillage effect on gross nitrification, and gross nitrification was positively correlated with soil moisture, but not with gross mineralization and microbial biomass. N2O emissions were higher in no-tillage (NT) than for conventional tillage (CT) during May-August. The N-15 labelling indicated that 26-92 % of the N2O was directly derived from the soil ammonium (NH4 (+)) pool. Emission rates of N2O from both nitrification and denitrification were positively correlated with NH4 (+) supply as expressed by gross mineralization, but not correlated with supply of nitrate as expressed by gross nitrification. The fraction of nitrified N emitted as N2O was positively correlated with changes in soil moisture and varied within 0.01-2.51 aEuro degrees. Our results showed that the tillage management impact on gross N transformation was not consistent with N2O emission, and more detailed information on the controls over N2O formation needs to be sought.
  • Authors:
    • Zhang, Y. M.
    • Li, X. X.
    • Oenema, O.
    • Hu, C. S.
    • Wang, Y. Y.
    • Qin, S. P.
    • Dong, W. X.
  • Source: Atmospheric Environment
  • Volume: 55
  • Year: 2012
  • Summary: Emissions of nitrous oxide (N 2O) from agricultural soils contribute to global warming and stratospheric ozone depletion. Applications of fertilizer nitrogen (N) increase N 2O emission, but also increase agricultural production. Here, we report on the responses of crop yield, N 2O emission and yield-scaled N 2O emission (N 2O emission per unit N uptake by grain and aboveground biomass) to different N fertilizer rates in a winter wheat-summer corn double-cropping system in the North China Plain. Soil N 2O emission measurements were carried out for two years in a long-term field experiment, under semi-arid conditions with four flood irrigations events per year. Our results indicated that N 2O emissions were linear functions and yield-scaled N 2O emissions were cubic functions of N fertilizer application rate. Yield-scaled N 2O emissions were lowest at application rates of 136 kg N ha -1 yr -1. Using a quadratic-plateau model, it was found that maximal crop yields were achieved at an application rate of 317 kg N ha -1 yr -1, which is 20% less than current practice. This level is suggested to be a compromise between achieving food security and mitigation N 2O emissions.
  • Authors:
    • Zheng, Y. K.
    • Yang, G. A.
    • Vasseur, L.
    • You, M. S.
    • Yao, F. L.
  • Source: Crop Protection
  • Volume: 34
  • Year: 2012
  • Summary: The frequent outbreaks of rice planthoppers, especially brown planthopper Nilaparvata lugens (Stal), in the last ten years in China and other Asian countries have caused serious rice ( Oryza sativa L.) yield losses. The key problem is possibly due to biodiversity loss in rice ecosystems. We examined the potential of intercrops of soybean ( Glycine max L.) and corn ( Zea mays L.), both of which are more profitable than rice and mostly planted in levees, to diversify rice ecosystems and enhance insect pest management. We studied the impacts of such intercrops on planthopper populations and their natural enemies. The results showed significantly lower numbers of rice planthoppers in rice fields with intercrops of corn than in rice monocultures and rice fields with intercrops of soybean. Rice fields with corn intercrops had 26-48% fewer planthoppers than rice monoculture. Rice fields with soybean intercrops had lower rice planthopper abundance compared to rice monoculture in 2008 but higher in 2009. However, neither parasitoid nor predator numbers were significantly affected by intercropping. There were no significant differences in directional movements of planthoppers or natural enemies between crop subplots in the different cropping systems. Moreover, movement of planthoppers was very limited. Our study indicated that soybean and corn intercrops do not greatly enhance the ability of natural enemies to suppress planthoppers. However, rice fields with intercrops of corn had lower abundance of planthoppers and this strategy may be useful as part of an integrated pest management strategy for the sustainable rice production.