• Authors:
    • Schoenau, J. J.
    • Malhi, S. S.
    • Fan, .
    • Xu, M.
    • Feng, W.
    • Six, J.
    • Plante, A. F.
  • Source: Canadian Journal of Soil Science
  • Volume: 94
  • Issue: 3
  • Year: 2014
  • Summary: Agricultural soils are typically depleted in soil organic matter compared with their undisturbed counterparts, thus reducing their fertility. Organic amendments, particularly manures, provide the opportunity to restore soil organic matter stocks, improve soil fertility and potentially sequester atmospheric carbon (C). The application of the soil C saturation theory can help identify soils with large C storage potentials. The goal of this study was to test whether soil C saturation can be observed in various soil types in agricultural ecosystems receiving long-term manure amendments. Seven long-term agricultural field experiments from China and Canada were selected for this study. Manure amendments increased C concentrations in bulk soil, particulate organic matter+sand, and silt+clay fractions in all the experiments. The increase in C concentrations of silt+clay did not fit the asymptotic regression as a function of C inputs better than the linear regression, indicating that silt+clay did not exhibit C saturation behavior. However, 44% of calculated C loading values for silt+clay were greater than the presumed maximal C loading, suggesting that this maximum may be greater than 1 mg C m -2 for many soils. The influences of soil mineral surface properties on C concentrations of silt+clay fractions were site specific. Fine soil particles did not exhibit C saturation behavior likely because current C inputs were insufficient to fill the large C saturation deficits of intensely cultivated soils, suggesting these soils may continue to act as sinks for atmospheric C.
  • Authors:
    • Gao, Z. Q.
    • Yang, W. S.
    • Li, P.
    • Ju, H.
    • Merchant, A.
    • Ma, Z. Y.
    • Han, X.
    • Gao, J.
    • Hao, X. Y.
    • Lin, E.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 192
  • Year: 2014
  • Summary: Investigations across the world have elucidated common chemical and physiological responses of plants to the influence of elevated atmospheric CO 2 concentration ([CO 2]). Focus is now turning to the influence of elevated [CO 2] on yield quality among a number of globally important crops including soybean ( Glycine max (L.) Merr). Soybean cv. Zhonghuang 35 was grown in a free-air CO 2 enrichment (FACE) field experiment at Changping-Beijing (China) under ambient (41516 mol mol -1) and elevated (55019 mol mol -1) CO 2 concentrations. Results showed that elevated [CO 2] increased the yields of soybean seeds (g m -2) by 26% and 31% respectively, in 2009 and 2011. Total protein concentration in seeds was significantly reduced by 3.3% under CO 2 enrichment, but oil concentration increased by 2.8%. Accordingly, most proteinogenic amino acid concentrations were significantly reduced under elevated [CO 2], whilst two fatty acids (linoleic acid and palmitic acid) increased in concentration. The protein and oil yield per unit ground area increased by 24.5% and 32.0%, respectively. Results indicate that whilst future elevated atmospheric [CO 2] may improve the oil quantity of soybean, corresponding reductions in the nutritive value are likely to occur.
  • Authors:
    • Liu, W. Z.
    • Li, J.
    • Yang, X. Y.
    • Chen, C.
    • Cleverly, J.
    • He, L.
    • Yu, Q.
  • Source: Agronomy Journal
  • Volume: 106
  • Issue: 4
  • Year: 2014
  • Summary: Crop production and water use in rainfed cropland are vulnerable to climate change. This study was to quantify diverse responses of winter wheat ( Triticum aestivum L.) yield and water use to climate change on the Loess Plateau (LP) under different combinations of climatic variables. The crop model APSIM was validated against field experimental data and applied to calculate yield and water use at 18 sites on the LP during 1961 to 2010. The coefficient of variation of yield ranged from 12 to 66%, in which the vulnerability of yield increased from the southeast (12%) to the northwest (66%). This change was attributed to the gradual increase in precipitation variation from the southeast to the northwest. An obvious warming trend during 1961 to 2010 resulted in a significant decrease in the growth duration by 1 to 5 d decade -1. The yield at 12 sites was significantly reduced by 120 to 720 kg ha -1 decade -1. Evapotranspiration was significantly decreased by 1 to 26 mm decade -1; however, water use efficiency at most sites showed no significant trend. Eighteen sites were classified into three climatic zones by cluster analysis: high temperature-high precipitation-low radiation (HHL), medium temperature-medium precipitation-medium radiation (MMM), and low temperature-low precipitation-high radiation (LLH). The trend of decreasing yield was smallest in the HHL cluster because of a minimal reduction in precipitation, while decreasing trends in yield and evapotranspiration were larger in the LLH and MMM because of larger reductions in precipitation. The results imply that among strategies such as breeding for long duration or drought tolerance, modification of the planting date will be necessary to avoid high temperatures associated with climate change.
  • Authors:
    • Wang, X. G.
    • Zhu, B.
    • Hua, K. K.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 98
  • Issue: 2
  • Year: 2014
  • Summary: Runoff is a major driver for dissolved organic carbon (DOC) diffusing into aquatic ecosystems. Transport of DOC in runoff is important in the C cycle of soils in an agricultural ecosystem. This study provides a combined dataset on DOC loss pathways and fluxes from sloping upland in the purple soil area of southwestern China. A free-drain lysimeter experiment was conducted to quantify DOC loss through overland flow (2010-2012), interflow (2010-2012) and sediment (2011-2012). Average annual cumulative discharges of overland and interflow were 58.3 +/- A 3.1 and 289.4 +/- A 5.4 mm, accounting for 6.8 and 33.8 % of the totals during the entire rainy season, respectively. Average annual cumulative sediment loss flux was 183.5 +/- A 14.6 g m(-2). Average DOC concentrations in overland flow and interflow were 3.44 +/- A 0.36 and 3.04 +/- A 0.24 mg L-1, respectively. Average DOC content in sediment was 73.76 +/- A 4.09 mg kg(-1). The relationship between DOC concentration and discharge in overland flow events could be described by a significant exponential decaying function (R = 0.53, P = 0.027). Average annual DOC loss fluxes through overland flow, interflow and sediment were 163.6 +/- A 28.5, 865.5 +/- A 82.5 and 9.4 +/- A 1.5 mg m(-2), respectively, and total DOC loss was 1,038.5 +/- A 112.5 mg m(-2). The results suggest that interflow is the major driver of DOC leaching loss on sloping upland. It is shown that interflow is fundamentally important for reducing DOC loss on sloping croplands in the Sichuan Basin and possibly beyond.
  • Authors:
    • Asseng, S.
    • Zhu, Y.
    • Cao, W. X.
    • Tian, L. Y.
    • Liu, L. L.
    • Liu, B.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 2
  • Year: 2014
  • Summary: Wheat is sensitive to high temperatures, but the spatial and temporal variability of high temperature and its impact on yield are often not known. An analysis of historical climate and yield data was undertaken to characterize the spatial and temporal variability of heat stress between heading and maturity and its impact on wheat grain yield in China. Several heat stress indices were developed to quantify heat intensity, frequency, and duration between heading and maturity based on measured maximum temperature records of the last 50 years from 166 stations in the main wheat-growing region of China. Surprisingly, heat stress between heading and maturity was more severe in the generally cooler northern wheat-growing regions than the generally warmer southern regions of China, because of the delayed time of heading with low temperatures during the earlier growing season and the exposure of the post-heading phase into the warmer part of the year. Heat stress between heading and maturity has increased in the last decades in most of the main winter wheat production areas of China, but the rate was higher in the south than in the north. The correlation between measured grain yields and post-heading heat stress and average temperature were statistically significant in the entire wheat-producing region, and explained about 29% of the observed spatial and temporal yield variability. A heat stress index considering the duration and intensity of heat between heading and maturity was required to describe the correlation of heat stress and yield variability. Because heat stress is a major cause of yield loss and the number of heat events is projected to increase in the future, quantifying the future impact of heat stress on wheat production and developing appropriate adaptation and mitigation strategies are critical for developing food security policies in China and elsewhere.
  • Authors:
    • Miao, S. J.
    • Han, X. Z.
    • Doane,T. A.
    • Qiao, Y. F.
  • Source: Journal of Food, Agriculture & Environment
  • Volume: 12
  • Issue: 2
  • Year: 2014
  • Summary: The impact of long-term fertilizer application on greenhouse gas emission and global warming potential (GWP) is not well documented. A long-term fertilizer experiment, located at the Hailun State Key Agro-ecological Experiment Station, Hailun County, Heilongjiang Province, China, was used in this study to completely account for emission of CO 2 and N 2O from maize-soybean rotation systems. Five treatments were implemented, including nitrogen and potassium (NK), nitrogen and phosphorus (NP), balanced inorganic fertilizer (NPK), combined inorganic/organic fertilizer (NPKM), and no fertilizer (Cont.). CO 2 and N 2O fluxes were measured using a closed-chamber method from May 2006 to April 2007, and net GWP was estimated using emission data and considering CO 2 fixed by crops. With the exception of NK in soybean, long-term fertilizer application significantly increased crop biomass in all treatments and both crops compared to Cont. plots. Long-term inorganic fertilizer application tended to decrease total CO 2 emission and increase total N 2O emission. Inorganic/organic combination fertilizer significantly increased CO 2 and N 2O emission by 41% and 388% compared to the Cont., respectively. Compared with the Cont., inorganic fertilizer application significantly decreased total net GWP by 179%; in contrast, net GWP was increased 82% by inorganic/organic combination fertilizer application. The results of this study indicate that reduction of GWP and agricultural economic gain can be simultaneously achieved by appropriate fertilizer application.
  • Authors:
    • Zhang, Y. M.
    • Dong, W. X.
    • Schaefer, D. A.
    • Oenema, O.
    • Ming, H.
    • Hu, C. S.
    • Wang, Y. Y.
    • Li, X. X.
  • Source: PLOS ONE
  • Volume: 9
  • Issue: 6
  • Year: 2014
  • Summary: The production and consumption of the greenhouse gases (GHGs) methane (CH 4), carbon dioxide (CO 2) and nitrous oxide (N 2O) in soil profile are poorly understood. This work sought to quantify the GHG production and consumption at seven depths (0-30, 30-60, 60-90, 90-150, 150-200, 200-250 and 250-300 cm) in a long-term field experiment with a winter wheat-summer maize rotation system, and four N application rates (0; 200; 400 and 600 kg N ha -1 year -1) in the North China Plain. The gas samples were taken twice a week and analyzed by gas chromatography. GHG production and consumption in soil layers were inferred using Fick's law. Results showed nitrogen application significantly increased N 2O fluxes in soil down to 90 cm but did not affect CH 4 and CO 2 fluxes. Soil moisture played an important role in soil profile GHG fluxes; both CH 4 consumption and CO 2 fluxes in and from soil tended to decrease with increasing soil water filled pore space (WFPS). The top 0-60 cm of soil was a sink of atmospheric CH 4, and a source of both CO 2 and N 2O, more than 90% of the annual cumulative GHG fluxes originated at depths shallower than 90 cm; the subsoil (>90 cm) was not a major source or sink of GHG, rather it acted as a 'reservoir'. This study provides quantitative evidence for the production and consumption of CH 4, CO 2 and N 2O in the soil profile.
  • Authors:
    • Wang, Y. Y.
    • Zhao, F. H.
    • Sun, X. M.
    • Wen, X. F.
    • Bao, X. Y.
  • Source: PLOS ONE
  • Volume: 9
  • Issue: 10
  • Year: 2014
  • Summary: Interannual variation in plant phenology can lead to major modifications in the interannual variation of net ecosystem production (NEP) and net biome production (NBP) as a result of recent climate change in croplands. Continuous measurements of carbon flux using the eddy covariance technique were conducted in two winter wheat and summer maize double-cropped croplands during 2003-2012 in Yucheng and during 2007-2012 in Luancheng on the North China Plain. Our results showed that the difference between the NEP and the NBP, i.e., the crop economic yield, was conservative even though the NEP and the NBP for both sites exhibited marked fluctuations during the years of observation. A significant and positive relationship was found between the annual carbon uptake period (CUP) and the NEP as well as the NBP. The NEP and the NBP would increase by 14.8 +/- 5.2 and 14.7 +/- 6.6 g C m(-2) 22 yr(-1), respectively, if one CUP-day was extended. A positive relationship also existed between the CUP and the NEP as well as the NBP for winter wheat and summer maize, respectively. The annual air temperature, through its negative effect on the start date of the CUP, determined the length of the CUP. The spring temperature was the main indirect factor controlling the annual carbon sequestration when a one-season crop (winter wheat) was considered. Thus, global warming can be expected to extend the length of the CUP and thus increase carbon sequestration in croplands.
  • Authors:
    • Shangguan, Z. P.
    • Liu, G. B.
    • Deng, L.
  • Source: GLOBAL CHANGE BIOLOGY
  • Volume: 20
  • Issue: 11
  • Year: 2014
  • Summary: The establishment of either forest or grassland on degraded cropland has been proposed as an effective method for climate change mitigation because these land use types can increase soil carbon (C) stocks. This paper synthesized 135 recent publications (844 observations at 181 sites) focused on the conversion from cropland to grassland, shrubland or forest in China, better known as the 'Grain-for-Green' Program to determine which factors were driving changes to soil organic carbon (SOC). The results strongly indicate a positive impact of cropland conversion on soil C stocks. The temporal pattern for soil C stock changes in the 0-100 cm soil layer showed an initial decrease in soil C during the early stage (5 years) coincident with vegetation restoration. The rates of soil C change were higher in the surface profile (0-20 cm) than in deeper soil (20-100 cm). Cropland converted to forest (arbor) had the additional benefit of a slower but more persistent C sequestration capacity than shrubland or grassland. Tree species played a significant role in determining the rate of change in soil C stocks (conifer < broadleaf, evergreen < deciduous forests). Restoration age was the main factor, not temperature and precipitation, affecting soil C stock change after cropland conversion with higher initial soil C stock sites having a negative effect on soil C accumulation. Soil C sequestration significantly increased with restoration age over the long-term, and therefore, the large scale of land-use change under the 'Grain-for-Green' Program will significantly increase China's C stocks.
  • Authors:
    • Zeng, Z. B.
    • Zhu ,B.
    • Dong, Z. X.
  • Source: ENVIRONMENTAL SCIENCE-PROCESSES & IMPACTS
  • Volume: 16
  • Issue: 11
  • Year: 2014
  • Summary: The effects of nitrogen fertilization regimes on N2O emissions and denitrification rates were evaluated by in situ field incubation experiments with intact soil cores and the acetylene block technique. Intact soil cores were collected from long-term field experiments involving several N fertilization regimes, including single synthetic N fertilizer (N), organic manure (OM), synthetic N, P. K fertilizer (NPK), organic manure with synthetic fertilizer (OMNPK), crop straw residue with synthetic fertilizer (SRNPK) and no nitrogen fertilizer (NF). N2O was sampled from the head space of the cylinders to determine the daily N2O emission and denitrification rate. The results showed that the N2O emissions were greatly influenced by the specific fertilization regime even when the same nitrogen rate was applied. The mean N2O emissions and denitrification rates from the N, OM, NPK, OMNPK and SRNPK treatment were 2.22, 2.66, 1.94, 2.53, 1.67 and 4.63, 5.96, 4.15, 5.41, 3.65 mg per m(2) per day, respectively. The application of OM significantly increased the N2O emission and denitrification compared to the application of NPK because of the high soil organic carbon (SOC) content of OM. However, SRNPK increased the SOC content and decreased the N2O emissions significantly compared to the OM and OMNPK treatments because the addition of crop straw with a high C/N ratio to soil with a low inorganic N content induced N immobilization. The contents of soil nitrate and ammonium were the main limiting factors for N2O emissions in a positive regression as follows: Ln (N2O) = 2.511 + 1.258 x Ln ([NH4+] + [NO3-). Crop straw residue combined with synthetic fertilizer is recommended as an optimal strategy for mitigating N2O emissions and denitrification-induced N loss in rain-fed croplands.