• Authors:
    • Rong,Yuping
    • Ma,Lei
    • Johnson,Douglas A.
  • Source: Atmospheric Environment
  • Volume: 116
  • Year: 2015
  • Summary: Land-use types and management practices of temperate semiarid steppes may affect soil sink activity for atmospheric methane (CH4). Most previous studies related to CH4 have focused primarily on the growing season with only a few studies evaluating CH4 fluxes throughout the entire year. With CH4 exchange largely undocumented during the non-growing season, the annual CH4 uptake in different land-use types under various management practices is uncertain. The aim of this study was to investigate the annual variation of CH4 fluxes from four land-use types (ungrazed grassland, moderately grazed grassland, perennial pasture and cropland), which are the dominant land-use types in the agro-pastoral region of northern China. Fluxes of CH4 were measured throughout the year in four land-use types using a mobile greenhouse gas analyzer. Results showed that soils were a sink for atmospheric CH4 throughout the year for all land-use types. Annual CH4 uptake patterns were similar (but with quite different magnitudes) for all land-use types with low, spiky uptake during the two freeze-thaw periods, low and constant uptake during the frozen period and highly variable uptake with some emission events during the growing season. Seasonality of CH4 uptake was related to monthly mean temperature and precipitation. Monthly mean temperature and precipitation explained 56% (range: 40-83%) of the variability in monthly cumulative soil CH4 uptake. Annual CH4 uptake across all land-use types averaged 3.9 +/- 0.3 kg C ha(-1) yr(-1) (range: 1.0-10.2). CH4 uptake during the non-growing season represented about 50% (range: 41-59%) of annual CH4 uptake for the grassland types and 21% (range: 20-22%) for the cropland and perennial pasture land-use types. Moderate grazing (stocking rate 1.43 sheep ha(-1) yr(-1)) significantly increased annual CH4 uptake by 78% (P < 0.05) compared to ungrazed grassland. The highest annual CH4 uptake was observed for cropland (10.2 +/- 0.2 kg C ha(-1) yr(-1)), followed by 2.7 kg +/- 0.1C ha(-1) yr(-1) for perennial pasture. Our results documented year-long CH4 fluxes in four important land-use types in the expansive agro-pastoral region of northern China and contribute to our understanding of soil uptake levels of atmospheric CH4. (C) 2015 Elsevier Ltd. All rights reserved.
  • Authors:
    • Shi,Feng
    • Ge,Quansheng
    • Yang,Bao
    • Li,Jianping
    • Yang,Fengmei
    • Ljungqvist,Fredrik Charpentier
    • Solomina,Olga
    • Nakatsuka,Takeshi
    • Wang,Ninglian
    • Zhao,Sen
    • Xu,Chenxi
    • Fang,Keyan
    • Sano,Masaki
    • Chu,Guoqiang
    • Fan,Zexin
    • Gaire,Narayan P.
    • Zafar,Muhammad Usama
  • Source: Climatic Change
  • Volume: 131
  • Issue: 4
  • Year: 2015
  • Summary: To investigate climate variability in Asia during the last millennium, the spatial and temporal evolution of summer (June-July-August; JJA) temperature in eastern and south-central Asia is reconstructed using multi-proxy records and the regularized expectation maximization (RegEM) algorithm with truncated total least squares (TTLS), under a point-by-point regression (PPR) framework. The temperature index reconstructions show that the late 20th century was the warmest period in Asia over the past millennium. The temperature field reconstructions illustrate that temperatures in central, eastern, and southern China during the 11th and 13th centuries, and in western Asia during the 12th century, were significantly higher than those in other regions, and comparable to levels in the 20th century. Except for the most recent warming, all identified warm events showed distinct regional expressions and none were uniform over the entire reconstruction area. The main finding of the study is that spatial temperature patterns have, on centennial time-scales, varied greatly over the last millennium. Moreover, seven climate model simulations, from the Coupled Model Intercomparison Project Phase 5 (CMIP5), over the same region of Asia, are all consistent with the temperature index reconstruction at the 99 % confidence level. Only spatial temperature patterns extracted as the first empirical orthogonal function (EOF) from the GISS-E2-R and MPI-ESM-P model simulations are significant and consistent with the temperature field reconstruction over the past millennium in Asia at the 90 % confidence level. This indicates that both the reconstruction and the simulations depict the temporal climate variability well over the past millennium. However, the spatial simulation or reconstruction capability of climate variability over the past millennium could be still limited. For reconstruction, some grid points do not pass validation tests and reveal the need for more proxies with high temporal resolution, accurate dating, and sensitive temperature signals, especially in central Asia and before AD 1400.
  • Authors:
    • Wang,Jinzhou
    • Wang,Xiujun
    • Xu,Minggang
    • Feng,Gu
    • Zhang,Wenju
    • Lu,Chang'ai
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 102
  • Issue: 3
  • Year: 2015
  • Summary: Straw has been commonly incorporated to maintain soil fertility and crop productivity in China, but effects of long-term straw incorporation on crop yield, soil organic carbon (SOC) and total nitrogen (TN) have not been thoroughly evaluated. Thus, this study analyzed data collected in long-term (> 10-year) trials across the major agricultural zones of China. Across the trials, relative to straw removal, straw return significantly increased crop yield, SOC and TN (by 7.0, 10.1 and 11.0 %, respectively). In some trials with winter wheat in northern China, straw return reduced yield by 0.6-7.1 %. The effects of straw return on SOC and TN were not significantly affected by experimental duration, land use type and cropping system, but positively and linearly related to the inputs of straw-C and -N, respectively. Interestingly, SOC and TN responses to straw return were decoupled in upland and upland-paddy soils in China, but not in paddy soils. Mean values of straw-C sequestration efficiency (7.7, 10.3 and 9.4 %, under corn, wheat and rice, respectively) indicate that 100 % straw return could increase SOC by 281.7 Tg C in 18 years (the mean experimental period of the considered studies) in China. Our analyses demonstrate that straw return is an effective practice for sustaining crop productivity and soil fertility in large parts of China, but site-specific factors should be considered.
  • Authors:
    • Xie YaPing
    • Gan YanTai
    • Li Yang
    • Niu JunYi
    • Gao YuHong
    • An HuiHui
    • Li AiRong
  • Source: Plant and Soil
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Oilseed flax ( Linum usitatissimum L.) yields are primarily fertilizer-limited, especially by N supply in the semiarid regions of North China. This study was conducted to determine whether N accumulation, translocation and N use efficiency (NUE) could be manipulated through N. The effects of N on N translocation, oilseed flax yield, oil content and NUE were studied at Zhangjiakou, China. Plants were grown at 0, 45, 90, and 135 kg N ha -1 (designated as the control, low N, moderate N, and high N, respectively), in 2011 and 2012. We found that N accumulation in leaves and capsule pericarps reached the maximum at anthesis and kernel developmental stage, respectively, then decreased rapidly before maturity. Averaged over 2 yr, N translocation from leaves to the seeds increased by 43, 150, and 150% under low N, moderate N, and high N, respectively, compared to the control; similarly, N translocation in capsule pericarps increased by 43, 243, and 190%, respectively. We discovered that leaves contributed the largest proportion of the seed N (averaging 80% in both years), and secondarily by the capsule pericarp N, which contributed 12% (in 2011) and 9% (in 2012) of the seed N. The highest seed yields were 2270 kg ha -1 (in 2011) and 1903 kg ha -1 (in 2012) which were obtained with the moderate N. Oil content was not affected by N. Nitrogen use efficiency decreased with progressively higher rates of N. The results suggest the moderate-N supply was adequate for promoting N translocation, and increasing N harvest index, NUE, and the productivity of oilseed flax.
  • Authors:
    • Yan Jiao
    • Hou JianHua
    • Zhao JiangHong
    • Yang WenZhu
  • Source: Acta Agriculturae Scandinavica: Section B, Soil & Plant Science
  • Volume: 65
  • Issue: 6
  • Year: 2015
  • Summary: The effects of soil properties and cropland age on atmospheric nitrous oxide (N2O) emissions following the conversion of grassland to cropland in temperate grassland ecosystems are uncertain. In this study, N2O emissions were compared among grassland and cropland soils in the agro-pastoral ecotone of Inner Mongolia over three growing seasons. Four adjacent sites with different land-use histories were selected, including grassland and croplands cultivated for 5, 10, and 50 years after conversion. N2O flux measurements were obtained using a closed-chamber method and were performed continuously during vegetation periods. After the conversion of grassland to cropland, N2O emission initially decreased and thereafter increased in the study sites. The cumulative N2O emissions of the cropland soils 5 and 10 years in age were 10-50% less than those of the grassland, and the N2O emissions from the cropland soil 50 years in age were 10-30% greater than the grassland. When the seasonal emissions were correlated against single soil parameter, the key soil parameter that affected N2O emissions over the entire growing season was the soil moisture content. When the interactions among soil parameters were considered, the amount of N2O emissions could be quantitatively described by a linear combination of two soil variables, the soil ammonium nitrogen (NH4+-N) and moisture concentrations. This study demonstrates how the time of land use conversion from grassland to cropland can positively or negatively affect N2O emission.
  • Authors:
    • Yunusa,Isa A. M.
    • Blair,Graeme
    • Zerihun,Ayalsew
    • Yang,Shenjiao
    • Wilson,Susan C.
    • Young,Iain M.
  • Source: Acta Agriculturae Scandinavica, Section B — Soil & Plant Science
  • Volume: 131
  • Issue: 4
  • Year: 2015
  • Summary: Coal-fired power generation and agriculture account for more than half of global greenhouse gas emissions, but the coal fly ash (CFA) produced in the former can be a resource for reducing emissions from agriculture to minimise environmental footprints in both industries. Our aim in this study was to test how acidic and alkaline CFA addition could minimise loss of C and N from acidic soil, with or without added manure. We determined composition and structural characteristics of acidic and alkaline CFA for their capacity to adsorb organic carbon, but observed poor adsorption because of low concentrations of cenospheres and unburnt carbon as the primary absorbents in the ash. Addition of CFA had no impact on the loss of carbon or nitrogen from unmanured soil in which concentrations of these nutrients were low. Loss of carbon from manured soil was reduced by 36 % with alkaline ashes and by 3-fold with acidic ashes; while loss of N was 30-50 % lower with acidic ashes, but 28 % higher with alkaline ashes, compared with no ash treatment. The increases in C sparing with CFA addition were achieved not by direct C absorption but by restraining microbial population and respiration, and potentially emissions. Alkaline CFA increased soil pH and if used to substitute just 10 % of lime for ameliorating soil acidity would reduce CO2 emission associated with the mining of the lime and its eventual dissolution in soil by 2.66 Tg or 2.8 % of Australia's annual agricultural emissions. High concentrations of oxides of phosphorus, silicon, titanium and clay particles in acidic ashes, and oxides of cations in alkaline ashes, were associated with potential for promoting C storage and acidity amelioration in soil.
  • Authors:
    • Zhan DongXia
    • Zhang Chao
    • Yang Ying
    • Luo HongHai
    • Zhang YaLi
    • Zhang WangFeng
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Little is known about how water deficit affects cotton ( Gossypium hirsutum L.) canopy architecture and the vertical distribution of photosynthesis within the canopy. The objective of this 2-yr field experiment was to determine the effects of reduced water supply on (i) surface area distribution within a cotton canopy, (ii) the transmission of photosynthetically active radiation (PAR) within the canopy, and (iii) the contribution of leaves and non-leaf organs at different positions within the canopy to whole-canopy photosynthesis. The results showed that compared with conventional irrigation, water deficit reduced leaf surface area in the upper canopy layer by 20 to 46% and increased PAR transmission into the mid-canopy layer by 38 to 73%. Slight water deficit reduced leaf photosynthetic rates in the upper canopy layer by 24%, but increased leaf photosynthetic rates in the mid-canopy layer by 23% and the lower canopy layer by 79%. Compared with conventional irrigation, slight water deficit had no significant effect on yield, whereas moderate water deficit significantly reduced both variables. Leaves, especially those in the upper canopy layer, were the main drivers of whole-canopy photosynthesis. On a percentage basis, non-leaf organs accounted for <26% of whole-canopy photosynthesis. Future research is needed to learn more about the photosynthetic potential of non-leaf organs and their response to water deficit.
  • Authors:
    • Gong,Daozhi
    • Hao,Weiping
    • Mei,Xurong
    • Gao,Xiang
    • Liu,Qi
    • Caylor,Kelly
  • Source: PLoS ONE
  • Volume: 10
  • Issue: 8
  • Year: 2015
  • Summary: Effects of agricultural practices on ecosystem carbon storage have acquired widespread concern due to its alleviation of rising atmospheric CO2 concentrations. Recently, combining of furrow-ridge with plastic film mulching in spring maize ecosystem was widely applied to boost crop water productivity in the semiarid regions of China. However, there is still limited information about the potentials for increased ecosystem carbon storage of this tillage method. The objective of this study was to quantify and contrast net carbon dioxide exchange, biomass accumulation and carbon budgets of maize (Zea maize L.) fields under the traditional non-mulching with flat tillage (CK) and partial plastic film mulching with furrow-ridge tillage (MFR) on the China Loess Plateau. Half-hourly net ecosystem CO2 exchange (NEE) of both treatments were synchronously measured with two eddy covariance systems during the growing seasons of 2011 through 2013. At same time green leaf area index (GLAI) and biomass were also measured biweekly. Compared with CK, the warmer and wetter (+1.3 degrees C and +4.3%) top soil at MFR accelerated the rates of biomass accumulation, promoted greater green leaf area and thus shortened the growing seasons by an average value of 10.4 days for three years. MFR stimulated assimilation more than respiration during whole growing season, resulting in a higher carbon sequestration in terms of NEE of -79 gC/m(2) than CK. However, after considering carbon in harvested grain (or aboveground biomass), there is a slight higher carbon sink (or a stronger carbon source) in MFR due to its greater difference of aboveground biomass than that of grain between both treatments. These results demonstrate that partial plastic film mulched furrow-ridge tillage with aboveground biomass exclusive of grain returned to the soil is an effective way to enhance simultaneously carbon sequestration and grain yield of maize in the semiarid regions.
  • Authors:
    • Wang Zhan-biao
    • Wen Xin-ya
    • Zhang Hai-lin
    • Lu Xiao-hong
    • Chen Fu
  • Source: Journal of Integrative Agriculture
  • Volume: 14
  • Issue: 8
  • Year: 2015
  • Summary: Excessive use of N fertilizer in intensive agriculture can increase crop yield and at the same time cause high carbon (C) emissions. This study was conducted to determine optimized N fertilizer application for high grain yield and lower C emissions in summer corn (Zea mays L.). Afield experiment, including 0 (NO), 75(N75), 150 (N150), 225 (N225), and 300 (N300) kg N ha(-1) treatments, was carried out during 2010-2012 in the North China Plain (NCP). The results showed that grain yield, input energy, greenhouse gas (GHG) emissions, and carbon footprint (CF) were all increased with the increase of N rate, except net energy yield (NEY). The treatment of N225 had the highest grain yield (10364.7 kg ha(-1)) and NEY (6.8%), but the CF (0.25) was lower than that of N300, which indicates that a rate of 225 kg N ha(-1) can be optimal for summer corn in NCR Comparing GHG emision compontents, N fertilizer (0-51.1%) was the highest and followed by electricity for irrigation (19.73-49.35%). We conclude that optimazing N fertilizer application rate and reducing electricity for irrigation are the two key measures to increase crop yield, improve energy efficiency and decrease GHG emissions in corn production.
  • Authors:
    • He, X.
    • Guan, Q.
    • Lu, X.
    • Lu, M.
    • Wu, H.
  • Source: Biology Article
  • Volume: 88
  • Year: 2015
  • Summary: Soil fauna can significantly affect soil CO2 and N2O emissions, but little is known about interactions between faunal groups and their relative contribution to such emissions. Over a 64-day microcosm incubation, we studied the effects of an epigeic earthworm (Eisenia fetida), mesofauna (Collembola plus oribatid mites) and their combinations on soil CO2 and N2O emissions under two faunal densities. Earthworms significantly enhanced soil CO2 and N2O emissions, while mesofauna only increased N2O emissions. Soil CO2 and N2O emissions were significantly affected by earthworm density, but not by mesofauna density. No significant interactive effects between earthworms and mesofauna were found on soil CO2 and N2O emissions. Our results indicate that earthworms probably play the dominant roles in determining soil CO2 and N2O emissions where they coexist with soil mesofauna. (C) 2015 Elsevier Ltd. All rights reserved.