• Authors:
    • Yu, Y.
    • Zhang, W.
    • Li, T.
    • Wang, G.
  • Source: PLoS ONE
  • Volume: 9
  • Issue: 4
  • Year: 2014
  • Summary: Dynamics of cropland soil organic carbon (SOC) in response to different management practices and environmental conditions across North China Plain (NCP) were studied using a modeling approach. We identified the key variables driving SOC changes at a high spatial resolution (10 kmx10 km) and long time scale (90 years). The model used future climatic data from the FGOALS model based on four future greenhouse gas (GHG) concentration scenarios. Agricultural practices included different rates of nitrogen (N) fertilization, manure application, and stubble retention. We found that SOC change was significantly influenced by the management practices of stubble retention (linearly positive), manure application (linearly positive) and nitrogen fertilization (nonlinearly positive) - and the edaphic variable of initial SOC content (linearly negative). Temperature had weakly positive effects, while precipitation had negligible impacts on SOC dynamics under current irrigation management. The effects of increased N fertilization on SOC changes were most significant between the rates of 0 and 300 kg ha(-1) yr(-1). With a moderate rate of manure application (i.e., 2000 kg ha(-1) yr(-1)), stubble retention (i.e., 50%), and an optimal rate of nitrogen fertilization (i.e., 300 kg ha(-1) yr(-1)), more than 60% of the study area showed an increase in SOC, and the average SOC density across NCP was relatively steady during the study period. If the rates of manure application and stubble retention doubled (i.e., manure application rate of 4000 kg ha(-1) yr(-1) and stubble retention rate of 100%), soils across more than 90% of the study area would act as a net C sink, and the average SOC density kept increasing from 40 Mg ha(-1) during 2010s to the current worldwide average of similar to 55 Mg ha(-1) during 2060s. The results can help target agricultural management practices for effectively mitigating climate change through soil C sequestration.
  • Authors:
    • Sui, P.
    • Chen, Y.
    • Zhang, M.
    • Gao, W.
    • Yang, X.
  • Source: Journal of Cleaner Production
  • Volume: 76
  • Issue: August
  • Year: 2014
  • Summary: Increasing atmospheric concentrations of greenhouse gases has caused grievous global warming and associated consequences. Lowering carbon footprint to promote the development of cleaner production demands the immediate attention. In this study, the carbon footprint calculations were performed on five cropping systems in North China Plain from 2003 to 2010. The five cropping systems included sweet potato -> cotton -> sweet potato -> winter wheat-summer maize (SpCSpWS, 4-year cycle), ryegrass-cotton -> peanut -> winter wheat-summer maize (RCPWS, 3-year cycle), peanut -> winter wheat-summer maize (PWS, 2-year cycle), winter wheat-summer maize (WS, 1-year cycle), and continuous cotton (Cont C), established in a randomized complete-block design with three replicates. We used a modified carbon footprint calculation with localized greenhouse gas emissions parameters to analyze the carbon footprint of each cropping system per unit area, per kg biomass, and per unit economic output. Results showed that the lowest annual carbon footprint values were observed in SpCSpWS among the five cropping systems, which were only 27.9%, 28.2% and 25.0% of those in WS rotation system (the highest carbon footprint) in terms of per unit area, per unit biomass, and per unit economic output, respectively. The five cropping systems showed the order of SpCSpWS < Cont C < RCPWS < PWS < WS sorting by their annual carbon footprint calculated by all the three metrics above-mentioned. Results revealed that appropriate diversified crop rotation systems could contribute to decreased carbon footprint compared with conventional intensive crop production system in North China Plain. (C) 2014 Elsevier Ltd. All rights reserved.
  • Authors:
    • Zhang, W.
    • Li, D. J.
    • Xu, X. L.
    • Luo, Y. Q.
    • Kumar, S.
    • Rafique, R.
    • Asam, Z. U.
  • Source: Global and Planetary Change
  • Volume: 118
  • Year: 2014
  • Summary: Greenhouse gas (GHG) emissions play an important role in regulating the Earth surface temperature. GHG emissions from soils are sensitive to climate change and land management practices. According to general circulation model (GCM) predictions, the Earth will experience a combination of increased temperature and altered precipitation regimes which may result in an increase or a decrease of GHG exchange. The effect of climate change on GHG emissions can be examined through both experiments and by applying process-based models, which have become more popular. The performance of those models can be improved significantly by appropriate calibration procedures. The objectives of this study are to: (i) calibrate the DAYCENT model using advance parameter estimation (PEST) software and to (ii) examine simulated GHG dynamics at daily and seasonal time-scales under a climate change scenario of increased temperature (2°C) and a precipitation regime change where 40% of precipitation during the dry season was redistributed to the wet season. The algorithmic calibration improved the model performance by reducing the sum of weighted squared residual differences by up to 223% (decreased from 1635 to 505 g N 2O-N ha -1 d -1) for N 2O and 22% (decreased from 623 to 507% WFPS) for water filled pore space (WFPS) simulation results. In the altered climate scenario, total N2O and CO2 fluxes decreased by 9% (from 2.31 to 2.10 kg N2O-N ha -1 yr -1) and 38% (from 1134.08 to 699.56 kg CO2 ha -1 yr -1) respectively, whereas CH4 fluxes increased by 10% (from 1.62 to 1.80 kg CH4 ha -1 yr -1). Our results show a larger impact of altered climate on CO2 as compared to N2O and CH4 emissions. The main difference in all GHG emissions was observed in summer period due to drought conditions created by reduced precipitation and increased temperatures. However, the GHG dynamics can also be attributed to no-till practices which play an important role in changing the soil moisture conditions for aerobic and anaerobic microsites. These results are based on a process-based model, therefore, we suggest performing experimental studies to examine the GHG emissions under increased temperature and especially under altered precipitation regimes.
  • Authors:
    • Greve, M. B.
    • Kheir, R. B.
    • Minasny, B.
    • Hartemink, A. E.
    • Adhikari, K.
    • Greve, M. H.
  • Source: PLOS ONE
  • Volume: 9
  • Issue: 8
  • Year: 2014
  • Summary: Estimation of carbon contents and stocks are important for carbon sequestration, greenhouse gas emissions and national carbon balance inventories. For Denmark, we modeled the vertical distribution of soil organic carbon (SOC) and bulk density, and mapped its spatial distribution at five standard soil depth intervals (0-5, 5-15, 15-30, 30-60 and 60-100 cm) using 18 environmental variables as predictors. SOC distribution was influenced by precipitation, land use, soil type, wetland, elevation, wetness index, and multi-resolution index of valley bottom flatness. The highest average SOC content of 20 g kg(-1) was reported for 0-5 cm soil, whereas there was on average 2.2 g SOC kg(-1) at 60-100 cm depth. For SOC and bulk density prediction precision decreased with soil depth, and a standard error of 2.8 g kg(-1) was found at 60-100 cm soil depth. Average SOC stock for 0-30 cm was 72 t ha(-1) and in the top 1 m there was 120 t SOC ha(-1). In total, the soils stored approximately 570 Tg C within the top 1 m. The soils under agriculture had the highest amount of carbon (444 Tg) followed by forest and semi-natural vegetation that contributed 11% of the total SOC stock. More than 60% of the total SOC stock was present in Podzols and Luvisols. Compared to previous estimates, our approach is more reliable as we adopted a robust quantification technique and mapped the spatial distribution of SOC stock and prediction uncertainty. The estimation was validated using common statistical indices and the data and high-resolution maps could be used for future soil carbon assessment and inventories.
  • Authors:
    • Bandyopadhyay, K. K.
    • Lal, R.
  • Source: Geoderma
  • Volume: 232/234
  • Year: 2014
  • Summary: Soils can be a source or sink for the atmospheric greenhouse gases (GHGs) depending on the land use management, which needs to be understood properly for devising management strategies to mitigate climate change. It is hypothesized that the aggregate size distribution under different land use management practices and the C and N concentration in these aggregates may influence GHG (CO 2, N 2O and CH 4) emissions from soil. To test this hypothesis, a laboratory incubation study was conducted using soils from a 16-year old tillage experiment on corn ( Zea mays L.) and the adjoining forest on a Crosby silt loam soil (Haplic Luvisols) at the Waterman Agricultural and Natural Resource Laboratory of the Ohio State University (OSU), Columbus, Ohio. It was observed that in forest soil, cumulative CO 2 and N 2O emissions were significantly higher than those from the cultivated soil by 81.2 and 100%, respectively. However, there was no significant difference between conventional tillage (CT) and no till (NT) with respect to the cumulative CO 2 and N 2O emissions. Emissions were significantly higher from the large macro-aggregates than from other aggregate size fractions. There was net CH 4 uptake by the soil during the incubation period. The cumulative CO 2 and N 2O emissions and CH 4 uptake from different aggregate size fractions accounted for 59, 56, and 47% of the emissions/uptake of these gases from the bulk soil, respectively. The contributions of the large macro-aggregates towards the bulk soil CO 2 (39%) and N 2O (37.9%) emissions and CH 4 uptake (49.7%) were significantly higher than those of the micro-aggregates and mineral fraction. Total soil carbon, nitrogen, particulate carbon and nitrogen, and mineral associated carbon and nitrogen accounted for 87, 87 and 66% variation in the cumulative CO 2 and N 2O emissions and CH 4 uptake, respectively.
  • Authors:
    • Grassini, P.
    • Gayler, S.
    • Sanctis, G. de
    • Deryng, D.
    • Corbeels, M.
    • Conijn, S.
    • Boogaard, H.
    • Biernath, C.
    • Basso, B.
    • Baron, C.
    • Adam, M.
    • Ruane, A. C.
    • Rosenzweig, C.
    • Jones, J. W.
    • Lizaso, J.
    • Boote, K.
    • Durand, J. L.
    • Brisson, N.
    • Bassu, S.
    • Hatfield, J.
    • Hoek, S.
    • Izaurralde, C.
    • Jongschaap, R.
    • Kemanian, A. R.
    • Kersebaum, K. C.
    • Kim, S. H. (et al)
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 7
  • Year: 2014
  • Summary: Potential consequences of climate change on crop production can be studied using mechanistic crop simulation models. While a broad variety of maize simulation models exist, it is not known whether different models diverge on grain yield responses to changes in climatic factors, or whether they agree in their general trends related to phenology, growth, and yield. With the goal of analyzing the sensitivity of simulated yields to changes in temperature and atmospheric carbon dioxide concentrations [CO 2], we present the largest maize crop model intercomparison to date, including 23 different models. These models were evaluated for four locations representing a wide range of maize production conditions in the world: Lusignan (France), Ames (USA), Rio Verde (Brazil) and Morogoro (Tanzania). While individual models differed considerably in absolute yield simulation at the four sites, an ensemble of a minimum number of models was able to simulate absolute yields accurately at the four sites even with low data for calibration, thus suggesting that using an ensemble of models has merit. Temperature increase had strong negative influence on modeled yield response of roughly -0.5 Mg ha -1 per °C. Doubling [CO 2] from 360 to 720 mol mol -1 increased grain yield by 7.5% on average across models and the sites. That would therefore make temperature the main factor altering maize yields at the end of this century. Furthermore, there was a large uncertainty in the yield response to [CO 2] among models. Model responses to temperature and [CO 2] did not differ whether models were simulated with low calibration information or, simulated with high level of calibration information.
  • Authors:
    • Johnston, A.
    • Snapp, S.
    • Zingore, S.
    • Chikowo, R.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 100
  • Issue: 1
  • Year: 2014
  • Summary: Farm typologies are a useful tool to assist in unpacking and understanding the wide diversity among smallholder farms to improve targeting of crop production intensification strategies. Sustainable crop production intensification will require the development of an array of nutrient management strategies tailored to farm-specific conditions, rather than blanket recommendations across diverse farms. This study reviewed key literature on smallholder farm typologies focusing on three countries (Kenya, Malawi and Zimbabwe), to gain insights on opportunities for crop production intensification, and the importance of developing farm-specific nutrient management practices. Investigations on farm typologies have done well in highlighting the fundamental differences between farm categories, with 3-5 typologies often adequate to represent the wide differences in resource endowment. Resource-endowed farmers have ready access to large quantities of manure and mineral fertilizers, which contribute to higher soil fertility and crop productivity on their farms. Resource-constrained households use little or no manure and mineral fertilizers, and have limited capacity to invest in labour-demanding soil fertility management technologies. These farmers often have to rely on off-farm opportunities for income that are largely limited to selling unskilled labour to their resource-endowed neighbors. The variability in management practices by farmers has resulted in three main soil fertility classes that can be used for targeting soil fertility management technologies, characterized by potential response to fertilizer application as: (1) low-responsive fertile fields that receive large additions of manure and fertilizer; (2) high-responsive infertile fields that receive moderate nutrient applications; (3) poorly responsive degraded soils cultivated for many years with little or no nutrient additions. The main conclusions drawn from the review are: (1) resource constrained farmers constitute the widest band across the three countries, with many of the farmers far below the threshold for sustainable maize production intensification and lacking capacity to invest in improved seed and fertilizer, (2) farm sizes and livestock ownership were key determinants for both farmer wealth status and farm productivity, and (3) soil organic carbon and available P were good indicators for predicting previous land management, that is also invariably linked to farmer resource endowment.
  • Authors:
    • Yang, X. M.
    • McLaughlin, N. B.
    • Tan, C. S.
    • Reynolds, W. D.
    • Drury, C. F.
    • Calder, W.
    • Oloya, T. O.
    • Yang, J. Y.
  • Source: Canadian Journal of Soil Science
  • Volume: 94
  • Issue: 3
  • Year: 2014
  • Summary: A field study was established in 1959 to evaluate the effects of fertilization and crop rotation on crop yields, soil and environmental quality on a Brookston clay loam. There were two fertilizer treatments (fertilized and not-fertilized) and six cropping treatments including continuous corn (CC), continuous Kentucky bluegrass sod and a 4-yr rotation of corn-oat-alfalfa-alfalfa with each phase present each year. We measured N 2O emissions, inorganic N and plant N uptake over three growing seasons (2007-2009) in the corn phase. Nitrous oxide emissions varied over the 3 yr as a result of the seasonal variation in precipitation quantity, intensity and timing and differences in crop growth and N uptake. Fertilized CC lost, on average, 7.36 kg N ha -1 by N 2O emissions, whereas the not-fertilized CC lost only 0.51 kg N ha -1. Fertilized rotation corn (RC) lost 6.46 kg N ha -1, which was 12% lower than fertilized CC. The not-fertilized RC, on the other hand, emitted about half as much N 2O (2.95 kg N ha -1) as the fertilized RC. Fertilized RC had corn grain yields that averaged 10.0 t ha -1 over the 3 yr followed by fertilized CC at 5.48 t ha -1. Not-fertilized RC corn had yields that were 61% lower (3.93 t ha -1) than fertilized RC, whereas the not-fertilized CC had yields that were 75% lower (1.39 t ha -1) than fertilized CC. Nitrous oxide emissions were found to be dramatically affected by long-term management practices and crop rotation had lower emissions in the corn phase of the rotation even though the N input from fertilizer addition and legume N fixation was greater. These N 2O emission and yield results were due to both factors that are traditionally used to describe these processes as well as long-term soil quality factors, which were created by the long-term management (i.e., soil organic carbon, soil physical parameters such as bulk density, and porosity, soil fauna and micro-flora) and that influenced crop growth, N uptake and soil water contents.
  • Authors:
    • Druschke, C. G.
    • Secchi, S.
  • Source: Journal of Soil and Water Conservation
  • Volume: 69
  • Issue: 2
  • Year: 2014
  • Summary: Female agricultural land ownership and operatorship are on the rise in Iowa and across the nation, but little research exists that explores agricultural conservation outreach to women and gendered differences in conservation knowledge and attitudes. The authors surveyed all agricultural landowners and operators in the Clear Creek Watershed in eastern Iowa about conservation knowledge and attitudes, as well as preferred sources of information about conservation. Clear Creek is a high-visibility watershed for conservation outreach for several reasons, including its long-standing watershed stakeholder council and its connection to the impaired Iowa River. Analysis of the survey results demonstrated that female respondents had significantly lower levels of knowledge about best management practices and significantly more positive attitudes towards conservation and collaboration than men. Meanwhile, women looked to the same sources for conservation information as male respondents, including neighbors, friends, and conservation agencies like the Natural Resources Conservation Service, Cooperative Extension, and the Farm Service Agency. These gendered results have significant consequences for the future of agricultural conservation practice and policy and for the subsequent health of the nation's soils and waterways. While lacking in knowledge about specific conservation practices, female respondents valued conservation practices, looked to government agencies for information about conservation, and expressed interest in collaborating with government entities for conservation on their land. Agricultural conservation practitioners can use these findings to tailor outreach efforts that will more effectively reach the nation's female landowners and operators.
  • Authors:
    • Liu, X.
    • Vidon, P.
    • Jacinthe, P. A.
    • Fisher, K.
    • Baker, M. E.
  • Source: Journal of Environmental Quality
  • Volume: 43
  • Issue: 1
  • Year: 2014
  • Summary: Riparian buffers are important nitrate (NO 3-) sinks in agricultural watersheds, but limited information is available regarding the intensity and control of nitrous oxide (N 2O) emission from these buffers. This study monitored (December 2009-May 2011) N 2O fluxes at two agricultural riparian buffers in the White River watershed in Indiana to assess the impact of land use and hydrogeomorphologic (HGM) attributes on emission. The study sites included a riparian forest in a glacial outwash/alluvium setting (White River [WR]) and a grassed riparian buffer in tile-drained till plains (Leary Weber Ditch [LWD]). Adjacent corn ( Zea mays L.) fields were monitored for land use assessment. Analysis of variance identified season, land use (riparian buffer vs. crop field), and site geomorphology as major drivers of N 2O fluxes. Strong relationships between N mineralization and N 2O fluxes were found at both sites, but relationships with other nutrient cycling indicators (C/N ratio, dissolved organic C, microbial biomass C) were detected only at LWD. Nitrous oxide emission showed strong seasonal variability; the largest N 2O peaks occurred in late spring/early summer as a result of flooding at the WR riparian buffer (up to 27.8 mg N 2O-N m -2 d -1) and N fertilizer application to crop fields. Annual N 2O emission (kg N 2O-N ha -1) was higher in the crop fields (WR: 7.82; LWD: 6.37) than in the riparian areas. A significant difference ( P<0.02) in annual N 2O emission between the riparian buffers was detected (4.32 vs. 1.03 kg N 2O-N ha -1 at WR and LWD, respectively), and this difference was attributed to site geomorphology and flooding (WR is flood prone; no flooding occurred at tile-drained LWD). The study results demonstrate the significance of landscape geomorphology and land-stream connection (i.e., flood potential) as drivers of N 2O emission in riparian buffers and therefore argue that an HGM-based approach should be especially suitable for determination of regional N 2O budget in riparian ecosystems.