• 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:
    • Tribouillois,H.
    • Cruz,P.
    • Cohan,J. P.
    • Justes,E.
  • Source: Agriculture, Ecosystems and Environment
  • Volume: 207
  • Year: 2015
  • Summary: Cover crops are used during fallow periods to produce ecosystem services, especially those related to N management such as (i) capturing mineral-N from soil to reduce nitrate leaching, and (ii) improving N availability for the next main crop (green manuring). Bispecific mixtures consisting of legume and non-legume species could simultaneously produce these two services of nitrate saving and green manuring. The magnitude of these services can be estimated from indicators of agroecosystem functions such as crop growth rate, crop N acquisition rate and the C:N ratio of the cover crop. We developed a conceptual model for each indicator which was described using general linear models. A three-step procedure was used: (1) represent the behavior of each species based on a sub-model and calibrate each species in bispecific mixtures; (2) validate the complete-mixture models, corresponding to the sum of the two species sub-models, and the proportion of each species in the whole cover, and (3) validate the generality of sub-models and complete-mixture models to predict the agroecosystem function indicators of species in mixture not used for calibration. The combined use of (i) potential agroecosystem functions measured in sole crop in non-limiting conditions, (ii) difference in leaf functional traits, as indicators of plant strategies and (iii) environmental factors, was efficient in fitting and predicting the level of agroecosystem functions provided by a cover crop species in mixture in actual conditions. The models fitted for bispecific mixtures were efficient to represent the behavior of each species in mixture and to estimate the legume proportion which expressed the species dominance. The models were evaluated as satisfactory for crop growth rate and C:N ratio for their generality in predicting the agroecosystem functions provided in mixtures by other species not used in the model calibration step, which illustrates the relevance and robustness of the approach.
  • Authors:
    • Karasawa,Toshihiko
    • Takahashi,Shigeru
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 103
  • Issue: 1
  • Year: 2015
  • Summary: Field experiments were conducted to clarify whether the introduction of several cover crop species increases P uptake of the following wheat and soybean. Four summer cover crops (sorghum, buckwheat, groundnut and crotalaria) and four winter cover crops (oat, rye, vetch and lupin) were tested. Growth and P uptake of succeeding wheat were significantly increased by P fertilizer application and tended to be increased by sorghum, groundnut or crotalaria incorporation, whereas buckwheat did not show positive effects. Growth and P uptake of succeeding soybean were significantly increased by oat or vetch incorporation and tended to be increased by P fertilizer or other cover crop incorporation. These positive effects of cover crops were attributed to the large amount of P incorporation, increase in the P-solubilizing fungal population and/or biomass P in soil. Sorghum, oat, rye and vetch were thought to be suitable cover crops to accelerate P uptake of the following crops since a large amount of P would be incorporated. Sorghum, groundnut and lupin were thought to be suitable cover crops because they increased the indigenous P-solubilizing fungal population in soil. Soil biomass P correlated with P uptake of wheat. Incorporation of suitable cover crops as a P source and activation of indigenous soil microorganisms by the carbon supply were thought to have accelerated P uptake of the following wheat and soybean. It is therefore thought that introduction of suitable cover crops could be an effective means to reduce P fertilizer application for the following crops.
  • Authors:
    • Meshalkina,J.
    • Yaroslavtsev,A.
    • Mazirov,I.
    • Samardzic,M.
    • Valentini,R.
    • Vasenev,I.
  • Source: Eurasian Journal of Soil Science
  • Volume: 4
  • Issue: 3
  • Year: 2015
  • Summary: The eddy covariance (EC) technique as a powerful statistics-based method of measurement and calculation the vertical turbulent fluxes of greenhouses gases within atmospheric boundary layers provides the continuous, long-term flux information integrated at the ecosystem scale. An attractive way to compare the agricultural practices influences on GHG fluxes is to divide a crop area into subplots managed in different ways. The research has been carried out in the Precision Farming Experimental Field of the Russian Timiryazev State Agricultural University (RTSAU, Moscow) in 2013 under the support of RF Government grant # 11.G34.31.0079, EU grant # 603542 LUC4C (7FP) and RF Ministry of education and science grant # 14-120-14-4266-ScSh. Arable Umbric Albeluvisols have around 1% of SOC, 5.4 pH (KCl) and NPK medium-enhanced contents in sandy loam topsoil. The CO 2 flux seasonal monitoring has been done by two eddy covariance stations located at the distance of 108 m. The LI-COR instrumental equipment was the same for the both stations. The stations differ only by current crop version: barley or vetch and oats. At both sites, diurnal patterns of NEE among different months were very similar in shape but varied slightly in amplitude. NEE values were about zero during spring time. CO 2 fluxes have been intensified after crop emerging from values of 3 to 7 mol/s.m 2 for emission, and from 5 to 20 mol/s.m 2 for sink. Stabilization of the fluxes has come at achieving plants height of 10-12 cm. Average NEE was negative only in June and July. Maximum uptake was observed in June with average values about 8 mol CO 2 m -2 s -1. Although different kind of crops were planted on the fields A and B, GPP dynamics was quite similar for both sites: after reaching the peak values at the mid of June, GPP decreased from 4 to 0.5 g C CO 2 m -2 d -1 at the end of July. The difference in crops harvesting time that was equal two weeks did not significantly influence the daily GPP patterns. Cumulative assimilation of CO 2 at the end of the growing season was about 150 g C m -2 for both sites. So the difference in NEE was the consequence of essentially higher respiration rates in case of vetch and oats (about 350 g C m -2) comparing to barley (250 g C m -2) that needs additional research. The results have shown high daily and seasonal dynamic of CO 2 emission too as a result of different and contrasted conditions: crop type, crop development stage, soil moisture and air temperature. Obtained unique for Russian agriculture data are useful for land-use practices environmental assessment, for soil organic carbon dynamics analysis and agroecological evaluation.
  • Authors:
    • Lupwayi, N.
    • Blackshaw, R.
    • Li, L
    • Pearson, D.
    • Larney, F.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 6
  • Year: 2015
  • Summary: Dry bean ( Phaseolus vulgaris L.) production on the Canadian prairies has traditionally used wide rows, inter-row cultivation, and undercutting at harvest. Recent breeding efforts have produced cultivars with more upright growth which are better suited to solid-seeded narrow-row production systems. A 12 yr (2000-2011) study compared conservation (CONS) and conventional (CONV) management for dry bean in 3- to 6-yr rotations. The CONS rotations included reduced tillage, cover crops, feedlot manure compost, and solid-seeded narrow-row dry bean. Effects of CONS management on plant density were inconsistent with some years showing lower density when seeded into high-residue conditions. On average, there was a 3 d maturity advantage with CONS (103 d) vs. CONV (106 d) management. The CONS rotations showed significantly higher mean incidence (19%) of white mold [ Sclerotinia sclerotiorum (Lib.) de Bary] than CONV rotations (6%). Averaging across 12 yr, there was no significant rotation effect on yield ( P=0.19) showing that CONS production performed as good as CONV production. In the last 2 yr (2010-2011) of the study, in an attempt to reduce harvest losses, CONS dry bean was undercut rather than direct combined. This led to significantly higher (25%) yield with CONS (3311 kg ha -1) vs. CONV management (2651 kg ha -1). Our results provide incentive for more rapid adoption of conservation-oriented soil and crop management practices for dry bean production on the Canadian prairies, including narrow rows, reduced tillage, cover crops, and feedlot manure compost addition.
  • Authors:
    • Benjamin, J. G.
    • Stahlman, P. W.
    • Mikha, M. M.
    • Geier, P. W.
  • Source: Agronomy Journal
  • Volume: 106
  • Issue: 1
  • Year: 2014
  • Summary: The response of manure applications on calcareous eroded soils in the western United States is unlike the responses observed on acid soils in the eastern United States. The objectives of this study were to restore the productivity and evaluate N loss of eroded land influenced by tillage practices, N sources, and N rates. The study was initiated in 2006 on an Armo silt loam (fine-loamy, mixed, mesic Entic Haplustolls) at the Agriculture Research Center, Hays, KS. Tillage practices were no-tillage (NT) and conventional tillage (CT). Nitrogen sources were beef manure (M); urea, as commercial fertilizer (F); and no-N control (C) at two rates, low (L) and high (H). The crop rotation was grain sorghum ( Sorghum bicolor L.), forage oat ( Avena sativa L.), winter wheat ( Triticum aestivum L.), grain sorghum, proso millet ( Panicum miliaceum L.), and winter wheat. Grain yield (2006-2011) and soil inorganic nitrogen (SIN) at 0- to 120-cm depth were evaluated. Grain yields were not influenced by tillage practices, except in 2006 when NT had greater yields than CT. Manure addition increased grain yields compared with F and C treatments. Excess amounts of N and low productivity lead to leaching of the SIN down the soil profile with HF and HM. The LM exhibited less productivity and less SIN loss than HM treatment. Overall, M could be the N source that can improve the productivity of the eroded site. The benefits of increasing the productivity and the risk of N loss with HM need to be further addressed.
  • Authors:
    • Martinez-Mena, M.
    • Almagro, M.
  • Source: AGRICULTURE ECOSYSTEMS & ENVIRONMENT
  • Volume: 196
  • Year: 2014
  • Summary: Soil erosion by water promotes the distribution of soil organic carbon (SOC) and nutrients within the landscape. Moreover, soil redistribution may have a large impact on litter decomposition dynamics. There is a current lack of information about the role of soil erosion in the SOC balance of sloping agricultural fields because its magnitude and direction depend on the dominant horizontal and vertical C fluxes at the different landform (eroding, transport and depositional) positions within the hillslope. Therefore, the significance of these lateral fluxes in the local C balance has to be assessed when interactions with vertical C fluxes (e.g., litter decay) are also taken into account. An experiment was designed to increase our understanding of the role of different phases of the soil erosion process in litter decomposition and the resulting impact on the soil C balance of a rain-fed olive grove under a dry Mediterranean climate, in which two or three high intensity-low frequency rainfall events are responsible for the majority of the annual soil erosion. To accomplish this, four replicate plots were installed at three different landform positions, according to erosion criteria (eroding, transport and depositional sites), and two litter types ( Avena sativa L. or Vicia sativa L.) with contrasting initial litter chemistry (high C:N, low C:N) were deployed in the middle of the summer season, before the expected occurrence of rainfall events in the experimental area. Two successive rainfall events led to pronounced patterns of erosion and associated processes of soil transport and deposition, accounting for 99% of total soil loss in the experimental area and leading to the burial of most of the litterbags located at the depositional positions. The results indicate that soil erosion (lateral movement and soil mixing) may be an important mechanism of litter decomposition, as litter mass loss rates were related closely to the amount of soil infiltrated/deposited within the litterbags for both litter types, decay rates at depositional sites being about three-fold higher than at eroding and transport sites. Our results also indicate that soil mobilisation by erosion has significant impacts on C dynamics, causing lateral and vertical fluxes of C similar in magnitude to those induced by changes in land use or management. According to our estimates, soil C losses driven by land-use change could be compensated after 20 years of green manure incorporation in this rainfed Mediterranean olive grove.
  • Authors:
    • Roisin, C.
    • Van Oost, K.
    • Trigalet, S.
    • van Wesemael, B.
  • Source: AGRICULTURE ECOSYSTEMS & ENVIRONMENT
  • Volume: 196
  • Year: 2014
  • Summary: Detecting soil organic carbon (SOC) gain or loss is challenging due to large uncertainties deriving from temporal and spatial variability of organic carbon concentrations, even at the field scale. In order to reduce these uncertainties, we used the organic carbon associated with clay and fine silt particles (fine fraction) rather than SOC in bulk soil for assessing decadal changes. This approach reduces the impact of the inherent variability of labile carbon on SOC estimates. We analysed archived soil samples taken in 1970 and recent ones taken in 2012 from an on-going long-term field trial in the Hesbaye region in Belgium. The experiment started in 1959 and contains three contrasting management practices (3*6 replicates): residue export (RE), farmyard manure (FYM) and residue restitution (RR). After 42 years, there are no significant differences in bulk soil organic carbon concentrations between treatments (RE=9.2 g C kg -1 soil; FYM=10.4 g C kg -1 soil; RR=10.1 g C kg -1 soil). In contrast, there are significant differences ( p<0.05) in stable carbon concentration (C associated to the fine fraction) between treatments over the same time period (RE=13.2 g C kg -1 clay and fine silt; FYM=16.6 g C kg -1 clay and fine silt; RR=15.4 g C kg -1 clay and fine silt). Moreover, we can be 99% confident that stable carbon in the fine fraction increased between 1970 and 2012 in FYM (+19%, p<0.01) and RR plots (+14%, p<0.01). There was a small, but significant, change of stable carbon in RE plots over the same period. In 1970, no differences in stable carbon concentration were detected between residue treatments. Labile carbon did not change significantly from 1970 to 2012 but its variability increased for all plots except for the RE treatment. We used the Rothamsted carbon model (RothC-26.3) to describe SOC changes under the different residue treatments. For bulk soil, observed trends in FYM and RR SOC concentrations are in line with the ones predicted. Modeled SOC changes from 1962 to 2012 are -14% (RE) and +10% (FYM). We also used RothC-26.3 to understand the evolution of the sensitive and slow fractions over time. On the one hand, we found that RothC was not capable to simulate the range of observed SOC concentrations inter-annual variability. On the other hand, the increase of the RothC pool with slow decomposition (HUM) was similar to the trend in the carbon associated with the fine fraction observed in the FYM and RR plots. This finding highlights that residue management can increase the storage of C in more stable fractions in agricultural soils, even when no changes are detected in bulk soil C.
  • Authors:
    • Bjornsson,L.
    • Prade,T.
  • Source: Proceedings of the 9th International Conference on Life Cycle Assessment in the Agri-Food Sector
  • Year: 2014
  • Summary: In an analysis of climate effects, increased soil organic carbon will have a dual effect due to both increased soil fertility and carbon sequestration. Even so, soil carbon changes are neglected in many crop production LCAs. In the present study, the introduction of grass-clover crops in cereal-dominated crop production was evaluated. The grass-clover crops were used for biogas production, and the digested residue was recycled to the farm as biofertilizer. A shift from the cereal-dominated crop rotation to integrated production of food crops and one or two years of grass-clover crops used as biogas feedstock would result in avoided emissions of 2-3 t CO 2-eq. ha -1 a -1. Integrated food and energy crop production would in this case improve soil organic carbon content at the same time as resulting in considerably decreased greenhouse gas emissions from the cultivation system.