• Authors:
    • Huang, B.-X.
    • Christie, P.
    • Oenema, O.
    • Gao, B.
    • Ju, X.-T.
    • Su, F.
    • Hu, X.-K.
    • Jiang, R.-F.
    • Zhang, F.-S.
  • Source: Environmental Pollution
  • Volume: 176
  • Year: 2013
  • Summary: Here, we report on a two-years field experiment aimed at the quantification of the emissions of nitrous oxide (N2O) and methane (CH4) from the dominant wheat maize double cropping system in North China Plain. The experiment had 6 different fertilization strategies, including a control treatment, recommended fertilization, with and without straw and manure applications, and nitrification inhibitor and slow release urea. Application of N fertilizer slightly decreased CH4 uptake by soil. Direct N2O emissions derived from recommended urea application was 0.39% of the annual urea-N input. Both straw and manure had relatively low N2O emissions factors. Slow release urea had a relatively high emission factor. Addition of nitrification inhibitor reduced N2O emission by 55%. We conclude that use of nitrification inhibitors is a promising strategy for N2O mitigation for the intensive wheat maize double cropping systems.
  • Authors:
    • Gao, W.
    • Sui, P.
    • Chen, Y.
    • Huang, J.
  • Source: Science of The Total Environment
  • Volume: 456-457
  • Year: 2013
  • Summary: The net greenhouse gas balance (NGHGB), estimated by combining direct and indirect greenhouse gas (GHG) emissions, can reveal whether an agricultural system is a sink or source of GHGs. Currently, two types of methods, referred to here as crop-based and soil-based approaches, are widely used to estimate the NGHGB of agricultural systems on annual and seasonal crop timescales. However, the two approaches may produce contradictory results, and few studies have tested which approach is more reliable. In this study, we examined the two approaches using experimental data from an intercropping trial with straw removal and a tillage trial with straw return. The results of the two approaches provided different views of the two trials. In the intercropping trial, NGHGB estimated by the crop-based approach indicated that monocultured maize (M) was a source of GHGs (-1315 kg CO2-eq ha(-1)), whereas maize-soybean intercropping (MS) was a sink (107 kg CO2-eq ha(-1)). When estimated by the soil-based approach, both cropping systems were sources (-3410 for M and -2638 kg CO2-eg ha(-1) for MS). In the tillage trial, mouldboard ploughing (MP) and rotary tillage (RT) mitigated GHG emissions by 22,451 and 21,500 kg CO2-eq ha(-1), respectively, as estimated by the crop-based approach. However, by the soil-based approach, both tillage methods were sources of GHGs: -3533 for MP and -2241 kg CO2-eq ha(-1) for RT. The crop-based approach calculates a GHG sink on the basis of the returned crop biomass (and other organic matter input) and estimates considerably more GHG mitigation potential than that calculated from the variations in soil organic carbon storage by the soil-based approach. These results indicate that the crop-based approach estimates higher GHG mitigation benefits compared to the soil-based approach and may overestimate the potential of GHG mitigation in agricultural systems.
  • Authors:
    • Hao, X. M.
    • Thelen, K. D.
    • Gao, J.
  • Source: Agronomy Journal
  • Volume: 105
  • Issue: 3
  • Year: 2013
  • Summary: Corn ( Zea mays L.) and corn stover are currently considered the most abundant and readily accessible feedstock resources for renewable bioethanol. Whole-plant corn harvest could increase bioethanol yield compared with a conventional separated grain and stover harvest. There is limited research, however, on the environmental effects of whole-plant harvest strategies, including nonrenewable energy efficiency, greenhouse gas (GHG) emission intensity, and soil organic C (SOC) changes. In this study, harvest methods together with bioprocessing steps were combined through life cycle analysis (LCA) models, and SOC changes for corn farming with different harvest methods were simulated by a Daycent ecosystem model. The harvest data were from four agronomy farms (Branch, Ingham, Huron, and Menominee) of Michigan State University across south to north in Michigan. The LCA results showed that a whole-plant harvest strategy could increase energy efficiency 3.4 to 4.3 times and reduce GHG emissions by 382% relative to a traditional separate grain and stover harvest strategy. The analyses also indicated, however, that whole-plant harvest could reduce SOC (66.922.9 g CO 2 equivalent m -2) annually during 50 yr of continuous corn farming at Branch, Ingham, and Huron, while the conventional harvest system could sequestrate CO 2 into SOC at Ingham, Huron, and Menominee. The Daycent simulation also showed that a winter cover crop planted after whole-plant immature corn harvest could compensate for part of the SOC loss associated with a whole-corn-plant harvest.
  • Authors:
    • Jat, M. L.
    • Jat, H. S.
    • Saharawat, Y. S.
    • Kumar, A.
    • Sharma, P. C.
    • Singh, M.
    • Kumar, V.
    • Gathala, M. K.
    • Humphreys, E.
    • Sharma, D. K.
    • Ladha, J. K.
    • Sharma, S.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 177
  • Year: 2013
  • Summary: Increasing scarcity of resources (labour, water, and energy) and cost of production, along with climate variability, are major challenges for the sustainability of rice-wheat system in the northwesten Indo-Gangetic Plains (IGP). We hypothesized that adopting the principles of conservation agriculture together with best crop management practices would improve system productivity and overall efficiency, resulting in a higher profitability. To test this hypothesis, we evaluated the performance of four cropping system scenarios (treatments), which were designed to be adapted to current and future drivers of agricultural changes. The treatments including farmers practices varied in tillage and crop establishment methods, residue management, crop sequence, and crop management. Zero-tillage direct-seeded rice (ZT-DSR) with residue retention and best management practices provided equivalent or higher yield and 30-50% lower irrigation water use than those of farmer-managed puddled transplanted rice (CT-TPR). Overall, net economic returns increased up to 79% with a net reduction in production cost of up to US$ 55 ha -1 in ZT-DSR than CT-TPR. Substituting rice with ZT maize was equally profitable but with 88-95% less irrigation water use. Avoiding puddling in rice and dry tillage in maize with residue retention increased yield (by 0.5-1.2 t ha -1) and net economic returns of the succeeding wheat crop. Inclusion of mungbean in the rotation further increased system productivity and economic returns. In summary, our initial results of 2-year field study showed positive effects of CA-based improved management practices on yield and system efficiencies with greater benefits in the second year. There is a need of longer term monitoring to quantify cumulative effects of various interventions and to eventually make recommendations for wider dissemination.
  • Authors:
    • Hatfield, J. L.
    • Hanan, N. P.
    • Glenn, A. J.
    • Fischer, M. L.
    • Burba, G. G.
    • Billesbach, D. P.
    • Bernacchi, C. J.
    • Baron, V. S.
    • Meyers, T. P.
    • Tieszen, L. L.
    • Wylie, B. K.
    • Gilmanov, T. G.
    • Heuer, M. W.
    • Hollinger, S. E.
    • Howard, D. M.
    • Matamala, R.
    • Prueger, J. H.
    • Tenuta, M.
    • Young, D. G.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 164
  • Year: 2013
  • Summary: We analyzed net CO 2 exchange data from 13 flux tower sites with 27 site-years of measurements over maize and wheat fields across midcontinent North America. A numerically robust "light-soil temperature-VPD"-based method was used to partition the data into photosynthetic assimilation and ecosystem respiration components. Year-round ecosystem-scale ecophysiological parameters of apparent quantum yield, photosynthetic capacity, convexity of the light response, respiration rate parameters, ecological light-use efficiency, and the curvature of the VPD-response of photosynthesis for maize and wheat crops were numerically identified and interpolated/extrapolated. This allowed us to gap-fill CO 2 exchange components and calculate annual totals and budgets. VPD-limitation of photosynthesis was systematically observed in grain crops of the region (occurring from 20 to 120 days during the growing season, depending on site and year), determined by the VPD regime and the numerical value of the curvature parameter of the photosynthesis-VPD-response, sigma VPD. In 78% of the 27 site-years of observations, annual gross photosynthesis in these crops significantly exceeded ecosystem respiration, resulting in a net ecosystem production of up to 2100 g CO 2 m -2 year -1. The measurement-based photosynthesis, respiration, and net ecosystem production data, as well as the estimates of the ecophysiological parameters, provide an empirical basis for parameterization and validation of mechanistic models of grain crop production in this economically and ecologically important region of North America.
  • Authors:
    • Ferro, C. A. T.
    • Challinor, A. J.
    • Fricker, T. E.
    • Hawkins, E.
    • Osborne,T. M.
    • Ho, C. K.
  • Source: Global Change Biology
  • Volume: 19
  • Issue: 3
  • Year: 2013
  • Summary: Improved crop yield forecasts could enable more effective adaptation to climate variability and change. Here, we explore how to combine historical observations of crop yields and weather with climate model simulations to produce crop yield projections for decision relevant timescales. Firstly, the effects on historical crop yields of improved technology, precipitation and daily maximum temperatures are modelled empirically, accounting for a nonlinear technology trend and interactions between temperature and precipitation, and applied specifically for a case study of maize in France. The relative importance of precipitation variability for maize yields in France has decreased significantly since the 1960s, likely due to increased irrigation. In addition, heat stress is found to be as important for yield as precipitation since around 2000. A significant reduction in maize yield is found for each day with a maximum temperature above 32°C, in broad agreement with previous estimates. The recent increase in such hot days has likely contributed to the observed yield stagnation. Furthermore, a general method for producing near-term crop yield projections, based on climate model simulations, is developed and utilized. We use projections of future daily maximum temperatures to assess the likely change in yields due to variations in climate. Importantly, we calibrate the climate model projections using observed data to ensure both reliable temperature mean and daily variability characteristics, and demonstrate that these methods work using retrospective predictions. We conclude that, to offset the projected increased daily maximum temperatures over France, improved technology will need to increase base level yields by 12% to be confident about maintaining current levels of yield for the period 2016-2035; the current rate of yield technology increase is not sufficient to meet this target.
  • Authors:
    • Markelz, R. J. C.
    • Ruiz-Vera, U. M.
    • Siebers, M. H.
    • Vanloocke, A.
    • Hussain, M. Z.
    • Leakey, A. D. B.
    • Ort, D. R.
    • Bernacchi, C. J.
  • Source: Global Change Biology
  • Volume: 19
  • Issue: 5
  • Year: 2013
  • Summary: Maize, in rotation with soybean, forms the largest continuous ecosystem in temperate North America, therefore changes to the biosphere-atmosphere exchange of water vapor and energy of these crops are likely to have an impact on the Midwestern US climate and hydrological cycle. As a C 4 crop, maize photosynthesis is already CO 2-saturated at current CO 2 concentrations ([CO 2]) and the primary response of maize to elevated [CO 2] is decreased stomatal conductance ( gs). If maize photosynthesis is not stimulated in elevated [CO 2], then reduced gs is not offset by greater canopy leaf area, which could potentially result in a greater ET reduction relative to that previously reported in soybean, a C 3 species. The objective of this study is to quantify the impact of elevated [CO 2] on canopy energy and water fluxes of maize ( Zea mays). Maize was grown under ambient and elevated [CO 2] (550 mol mol -1 during 2004 and 2006 and 585 mol mol -1 during 2010) using Free Air Concentration Enrichment (FACE) technology at the SoyFACE facility in Urbana, Illinois. Maize ET was determined using a residual energy balance approach based on measurements of sensible ( H) and soil heat fluxes, and net radiation. Relative to control, elevated [CO 2] decreased maize ET (7-11%; P<0.01) along with lesser soil moisture depletion, while H increased (25-30 W m -2; P<0.01) along with higher canopy temperature (0.5-0.6°C). This reduction in maize ET in elevated [CO 2] is approximately half that previously reported for soybean. A partitioning analysis showed that transpiration contributed less to total ET for maize compared to soybean, indicating a smaller role of stomata in dictating the ET response to elevated [CO 2]. Nonetheless, both maize and soybean had significantly decreased ET and increased H, highlighting the critical role of elevated [CO 2] in altering future hydrology and climate of the region that is extensively cropped with these species.
  • Authors:
    • Stevenson, F. C.
    • Vanasse, A.
    • Legere, A.
  • Source: Agronomy Journal
  • Volume: 105
  • Issue: 3
  • Year: 2013
  • Summary: Combining low-input systems with conservation tillage may be feasible for field crops under northeastern conditions. This study compared the effects of herbicide-free (HF), organic (ORG), conventional (CONV), and herbicide-tolerant (GM) cropping systems applied to three 20 yr-old tillage treatments (MP, moldboard plow; CP, chisel plow; NT, no-till) on weed biomass and crop productivity in a 4-yr barley ( Hordeum vulgare L.)-red clover ( Trifolium pratense L.)-corn ( Zea mays L.)-soybean [ Glycine max (L.) Merr.] rotation. Barley yield (4.5 Mg ha -1), and red clover forage yield (two cuts: 5.3 Mg ha -1) were similar across treatments. With MP and CP tillage, silage corn yield for CONV and GM systems (15 Mg ha -1) was 25% greater than for HF and ORG (11 Mg ha -1), whereas HF-NT and ORG-NT systems produced no harvestable yield. Soybean yield for HF-MP and ORG-MP systems was similar to that for CONV and GM (2.4 Mg ha -1), whereas yield in for the HF and ORG systems with CP and NT was half or less than for other treatments. Some form of primary tillage (CP or MP) was needed in corn and soybean to achieve adequate weed control and yield in the ORG and HF systems. Midseason weed proportion of total biomass was greater in the HF and ORG systems with CP and NT, and provided good yield prediction in corn ( R2=0.74) and soybean ( R2=0.84). Nutrient availability appeared adequate in corn following N 2-fixing red clover but limiting in NT and CP for soybean following corn. Improving crop sequence, fertilization, and weed management will be key to the adoption of low-input systems using conservation tillage practices in cool, humid climates.
  • Authors:
    • Lin, X. M.
    • Hubbard, K. G.
    • Liu, Z. J.
    • Yang, X. G.
  • Source: Global Change Biology
  • Volume: 19
  • Issue: 11
  • Year: 2013
  • Summary: Northeast China (NEC) accounts for about 30% of the nation's maize production in China. In the past three decades, maize yields in NEC have increased under changes in climate, cultivar selection and crop management. It is important to investigate the contribution of these changing factors to the historical yield increases to improve our understanding of how we can ensure increased yields in the future. In this study, we use phenology observations at six sites from 1981 to 2007 to detect trends in sowing dates and length of maize growing period, and then combine these observations with in situ temperature data to determine the trends of thermal time in the maize growing period, as a measure of changes in maize cultivars. The area in the vicinity of these six sites accounts for 30% of NEC's total maize production. The agricultural production systems simulator, APSIM-Maize model, was used to separate the impacts of changes in climate, sowing dates and thermal time requirements on maize phenology and yields. In NEC, sowing dates trended earlier in four of six sites and maturity dates trended later by 4-21 days. Therefore, the period from sowing to maturity ranged from 2 to 38 days longer in 2007 than it was in 1981. Our results indicate that climate trends alone would have led to a negative impact on maize. However, results from the adaptation assessments indicate that earlier sowing dates increased yields by up to 4%, and adoption of longer season cultivars caused a substantial increase in yield ranging from 13% to 38% over the past 27 years. Therefore, earlier sowing dates and introduction of cultivars with higher thermal time requirements in NEC have overcome the negative effects of climate change and turned what would have otherwise been a loss into a significant increase in maize yield.
  • Authors:
    • Ndabamenye, T.
    • Lelei, D.
    • Koala, S.
    • Hurisso, T. T.
    • Hoogmoed, M.
    • Gassner, A.
    • Ayuke, F.
    • Vanlauwe, B.
    • Paul, B. K.
    • Six, J.
    • Pulleman, M. M.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 164
  • Year: 2013
  • Summary: Conservation agriculture is widely promoted for soil conservation and crop productivity increase, although rigorous empirical evidence from sub-Saharan Africa is still limited. This study aimed to quantify the medium-term impact of tillage (conventional and reduced) and crop residue management (retention and removal) on soil and crop performance in a maize-soybean rotation. A replicated field trial was started in sub-humid Western Kenya in 2003, and measurements were taken from 2005 to 2008. Conventional tillage negatively affected soil aggregate stability when compared to reduced tillage, as indicated by lower mean weight diameter values upon wet sieving at 0-15 cm ( PT<0.001). This suggests increased susceptibility to slaking and soil erosion. Tillage and residue management alone did not affect soil C contents after 11 cropping seasons, but when residue was incorporated by tillage, soil C was higher at 15-30 cm ( PT*R=0.037). Lack of treatment effects on the C content of different aggregate fractions indicated that reduced tillage and/or residue retention did not increase physical C protection. The weak residue effect on aggregate stability and soil C may be attributed to insufficient residue retention. Soybean grain yields tended to be suppressed under reduced tillage without residue retention, especially in wet seasons ( PT*R=0.070). Consequently, future research should establish, for different climatic zones and soil types, the critical minimum residue retention levels for soil conservation and crop productivity.