• Authors:
    • Ryan,E. M.
    • Ogle,K.
    • Zelikova,T. J.
    • Lecain,D. R.
    • Williams,D. G.
    • Morgan,J. A.
    • Pendall,E.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 7
  • Year: 2015
  • Summary: Terrestrial plant and soil respiration, or ecosystem respiration (R eco), represents a major CO 2 flux in the global carbon cycle. However, there is disagreement in how R eco will respond to future global changes, such as elevated atmosphere CO 2 and warming. To address this, we synthesized six years (2007-2012) of R eco data from the Prairie Heating And CO 2 Enrichment (PHACE) experiment. We applied a semi-mechanistic temperature-response model to simultaneously evaluate the response of R eco to three treatment factors (elevated CO 2, warming, and soil water manipulation) and their interactions with antecedent soil conditions [e.g., past soil water content (SWC) and temperature (SoilT)] and aboveground factors (e.g., vapor pressure deficit, photosynthetically active radiation, vegetation greenness). The model fits the observed R eco well ( R2=0.77). We applied the model to estimate annual (March-October) R eco, which was stimulated under elevated CO 2 in most years, likely due to the indirect effect of elevated CO 2 on SWC. When aggregated from 2007 to 2012, total six-year R eco was stimulated by elevated CO 2 singly (24%) or in combination with warming (28%). Warming had little effect on annual R eco under ambient CO 2, but stimulated it under elevated CO 2 (32% across all years) when precipitation was high (e.g., 44% in 2009, a 'wet' year). Treatment-level differences in R eco can be partly attributed to the effects of antecedent SoilT and vegetation greenness on the apparent temperature sensitivity of R eco and to the effects of antecedent and current SWC and vegetation activity (greenness modulated by VPD) on R eco base rates. Thus, this study indicates that the incorporation of both antecedent environmental conditions and aboveground vegetation activity are critical to predicting R eco at multiple timescales (subdaily to annual) and under a future climate of elevated CO 2 and warming.
  • Authors:
    • Baumhardt,R. L.
    • Mauget,S. A.
    • Gowda,P. H.
    • Brauer,D. K.
    • Marek,G. W.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Equatorial Pacific sea surface temperature anomalies can cause a systematic El Nino-Southern Oscillation (ENSO) coupling with the atmosphere to produce predictable weather patterns in much of North America. Adapting irrigation strategies for drought-tolerant crops like cotton ( Gossypium hirsutum L.) to exploit forecast climatic conditions represents one potential innovative technique for managing the declining Ogallala Aquifer beneath the US Southern High Plains. The crop simulation model GOSSYM was used with ENSO phase-specific weather records during 1959 to 2000 at Bushland, TX, to estimate lint yields of cotton emerging on three dates from soil at 50 or 75% available water content for all possible combinations of irrigation durations (0, 4, 6, 8, and 10 wk) and rates (2.5, 3.75, and 5.0 mm d -1). From those data, our objective was to compare partial center pivot deficit irrigation strategies that optimize calculated net cotton lint yield in relation to ENSO phase, initial soil water content, and emergence date. Although phase classification in June was inconsistent with maturing fall phases, the most accurately classified La Nina phase had limited rain that reduced lint yields compared with wetter Neutral and El Nino phases. During La Nina phase conditions, irrigation strategies that focused fixed water resources on smaller areas were better suited to increase net yield than spreading water across larger areas. Alternatively, during less predictable and wetter Neutral and El Nino phases, irrigation strategies that spread water increased net lint yield over focused applications except when both initial soil water and irrigation amount were limiting.
  • Authors:
    • Dold,Christian
    • Becker,Mathias
  • Source: Journal of Plant Nutrition and Soil Science
  • Volume: 178
  • Issue: 4
  • Year: 2015
  • Summary: Lake Naivasha is a freshwater lake in the East African Rift Valley. With continued lake level declines between 1980 and 2011, the newly exposed land areas were gradually taken for agricultural use. The resulting chronosequences allow for an analysis of the effects of land use duration on nutrient dynamics and agricultural production. Transects representing land use durations of 0-30 (cropland) and 15-30 years (pasture) were established on soils formed on alluvial deposits and lacustrine sediments. We assessed changes in topsoil nitrogen (N) stocks (t ha(-1)), ammonium mineralization potential (N-supplying capacity), and plant-available P with increasing durations of land use. An additional greenhouse experiment studied the responses of kikuyu grass (Cenchrus clandestinus) and maize (Zea mays) in potted topsoil collected from differnt land-use types and chronosequence positions. With increasing duration of land use we noted a significant decline (P < 5%) in soil N contents under both pasture and cropland uses, following a model of exponential decay. The N stocks decreased at 84kgha(-1) a(-1) and a decay rate constant of 0.019a(-1) in pasture soil within 15 years, and at 75kgha(-1) a(-1) with a decay rate-constant of 0.013 a(-1) in cropland soil within 30 years. While the ammonium-N mineralization potential also decreased with land use duration, the trends were significant only in lacustrine pasture soils. Plant-available P did not show any trends that were related to the duration of land use. Kikuyu grass and maize accumulated less dry matter and N as the duration of use increased. This biomass accumulation was significantly related to soil N. A continued mineralization of soil organic matter has possibly contributed to the observed soil N depletion over time. The continuous agricultural use of the littoral wetland zone of Lake Naivasha is likely to entail declining production potentials for both pastures and food crops.
  • Authors:
    • Hao,B.
    • Xue,Q.
    • Marek,T. H.
    • Jessup,K. E.
    • Becker,J.
    • Hou,X.
    • Xu,W.
    • Bynum,E. D.
    • Bean,B. W.
    • Colaizzi,P. D.
    • Howell,T. A.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Drought is an important factor limiting corn ( Zea mays L.) yields in the Texas High Plains, and adoption of drought-tolerant (DT) hybrids could be a management tool under water shortage. We conducted a 3-yr field study to investigate yield, evapotranspiration (ET), and water use efficiency (WUE) in DT hybrids. One conventional (33D49) and 4 DT hybrids (P1151HR, P1324HR, P1498HR, and P1564HR) were grown at three water regimes (I 100, I 75, and I 50, referring to 100, 75, and 50% ET requirement) and three planting densities (PD) (5.9, 7.4, and 8.4 plants m -2). Yield (13.56 Mg ha -1) and ET (719 mm) were the greatest at I 100 but WUE (2.1 kg m -3) was the greatest at I 75. Although DT hybrids did not always have greater yield and WUE than 33D49 at I 100, hybrids P1151HR and P1564HR consistently had greater yield and WUE than 33D49 at I 75 and I 50. Compared to 33D49, P1151HR and P1564HR had 8.6 to 12.1% and 19.1% greater yield at I 75 and I 50, respectively. Correspondingly, WUE was 9.8 to 11.7% and 20.0% greater at I 75 and I 50, respectively. Greater PD resulted in greater yield and WUE at I 100 and I 75 but PD did not affect yield and WUE at I 50. Yield and WUE in greater PD (8.4 plants m -2) were 6.3 to 8.3% greater than those in smaller PD (5.9 plants m -2). The results of this study demonstrated that proper selection of DT hybrids can increase corn yield and WUE under water-limited conditions.
  • Authors:
    • Irani,S.
    • Majidi,M. M.
    • Mirlohi,A.
    • Zargar,M.
    • Karami,M.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: The physiological basis of genetic variation in drought response and its association with forage yield and drought tolerance indices is not clear in sainfoin ( Onobrychis viciifolia Scop.). In this study, 100 sainfoin genotypes from 10 ecotypes were clonally propagated and evaluated under non-stressed and water deficit conditions during 2 yr. Physiological traits including chlorophyll a, chlorophyll b, total chlorophyll, carotenoid content, proline content, relative water content (RWC), catalase (CAT), ascorbate peroxidase (APX), superoxide dismutase (SOD) activity, dry matter yield (DMY), and stress tolerance index (STI) were studied. Large genotypic variation was observed among ecotypes for most of the studied traits indicating that selection in this germplasm would be useful. The results showed that water deficit greatly influenced physiological traits that affected forage production. Water deficit decreased DMY and RWC while significantly increasing carotenoid content, free proline content, CAT, APX, and SOD activity in both years. The relationship between dry matter yield and STI with proline content showed that ecotypes with high DMY and STI under water deficit conditions had higher proline accumulation in their leaves. With regard to the STI and principal component analysis (PCA), ecotypes Baft, Najafabad, and Sirjan were found to be drought tolerant or moderately drought tolerant. These ecotypes showed significantly higher values for proline content under water deficit conditions.
  • Authors:
    • Schlegel,A. J.
    • Assefa,Y.
    • Bond,H. D.
    • Wetter,S. M.
    • Stone,L. R.
  • Source: Web Of Knowledge
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Cattle ( Bos taurus) manure and swine ( Sus scrofa) effluent are applied to cropland to recycle nutrients, build soil quality, and increase crop productivity. The objective of this study was to determine the long-term effects of land application of cattle manure and swine effluent using the Kansas Nutrient Utilization Plan on crop yield, yield components, and crop nutrient uptake. The study was conducted for 10 yr (1999 through 2008) near Tribune, KS. There were 10 treatments: three levels of cattle manure and swine effluent (P, N, and 2N), three levels of N fertilizer (N 1=56, N 2=112, and N 3=168 kg N ha -1), and an untreated control. Corn ( Zea mays L.) grain and stover yields, yield components, and water use were measured. In all but 2 yr, all treatments significantly increased grain yield compared with the control and the lowest inorganic N rate. Mean corn grain yield over the years from the Cattle N and P, Swine N and P, and inorganic N 2 and N 3 treatments were about 2*, 1.8*, and 1.9* greater than the untreated control, respectively. Grain nutrient content and water productivity were consistently higher for the cattle manure treatments and the inorganic N 2 and N 3 treatments. However, grain yield and nutrient uptake did not differ among rates of cattle manure and swine effluent application. We concluded that using the lower application rate based on either N or P from the Kansas Nutrient Utilization Plan was sufficient to achieve optimal crop yield and water productivity.
  • Authors:
    • Sieverding,H. L.
    • Bailey,L. M.
    • Hengen,T. J.
    • Clay,D. E.
    • Stone,J. J.
  • Source: Journal of Environmental Quality
  • Volume: 44
  • Issue: 4
  • Year: 2015
  • Summary: Biofuel policy changes in the United States have renewed interest in soybean [ Glycine max (L.) Merr.] biodiesel. Past studies with varying methodologies and functional units can provide valuable information for future work. A meta-analysis of nine peer-reviewed soybean life cycle analysis (LCA) biodiesel studies was conducted on the northern Great Plains in the United States. Results of LCA studies were assimilated into a standardized system boundary and functional units for global warming (GWP), eutrophication (EP), and acidification (AP) potentials using biodiesel conversions from peer-reviewed and government documents. Factors not fully standardized included variations in N 2O accounting, mid- or end-point impacts, land use change, allocation, and statistical sampling pools. A state-by-state comparison of GWP lower and higher heating values (LHV, HHV) showed differences attributable to variations in spatial sampling and agricultural practices (e.g., tillage, irrigation). The mean GWP of LHV was 21.1 g.CO 2-eq MJ -1 including outliers, and median EP LHV and AP LHV was 0.019 g.PO 4-eq MJ -1 and 0.17 g.SO 2-eq MJ -1, respectively, using the limited data available. An LCA case study of South Dakota soybean-based biodiesel production resulted in GWP estimates (29 or 31 g.CO 2-eq MJ -1; 100% mono alkyl esters [first generation] biodiesel or 100% fatty acid methyl ester [second generation] biodiesel) similar to meta-analysis results (30.1 g.CO 2-eq MJ -1). Meta-analysis mean results, including outliers, resemble the California Low Carbon Fuel Standard for soybean biodiesel default value without land use change of 21.25 g.CO 2-eq MJ -1. Results were influenced by resource investment differences in water, fertilizer (e.g., type, application), and tillage. Future biofuel LCA studies should include these important factors to better define reasonable energy variations in regional agricultural management practices.
  • 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:
    • Parton,W. J.
    • Gutmann,M. P.
    • Merchant,E. R.
    • Hartman,M. D.
    • Adler,P. R.
    • McNeal,F. M.
    • Lutz,S. M.
  • Source: Proceedings of the National Academy of Sciences of the United States
  • Volume: 112
  • Issue: 34
  • Year: 2015
  • Summary: The Great Plains region of the United States is an agricultural production center for the global market and, as such, an important source of greenhouse gas (GHG) emissions. This article uses historical agricultural census data and ecosystem models to estimate the magnitude of annual GHG fluxes from all agricultural sources (e.g., cropping, livestock raising, irrigation, fertilizer production, tractor use) in the Great Plains from 1870 to 2000. Here, we show that carbon (C) released during the plow-out of native grasslands was the largest source of GHG emissions before 1930, whereas livestock production, direct energy use, and soil nitrous oxide emissions are currently the largest sources. Climatic factors mediate these emissions, with cool and wet weather promoting C sequestration and hot and dry weather increasing GHG release. This analysis demonstrates the long-term ecosystem consequences of both historical and current agricultural activities, but also indicates that adoption of available alternative management practices could substantially mitigate agricultural GHG fluxes, ranging from a 34% reduction with a 25% adoption rate to as much as complete elimination with possible net sequestration of C when a greater proportion of farmers adopt new agricultural practices.
  • Authors:
    • Sapkota,T. B.
    • Kaushik Majumdar
    • Jat,M. L.
  • Source: Better Crops with Plant Food
  • Volume: 99
  • Issue: 3
  • Year: 2015
  • Summary: In a collaborative effort between the International Maize and Wheat Improvement Centre and the International Plant Nutrition Institute to test, pilot and upscale Nutrient Expert (NE; a decision support system)-based fertilizer management, on-farm participatory research was conducted in 7 districts (Karnal, Kurukshetra, Kaithal, Ambala, Sonepat, Panipat, and Yamunanager) of Haryana (India) to evaluate and compare the NE-based strategies in conventional and no-till wheat production systems. For this, 15 on-farm experiments were established in 2010-11 and 2011-12. The four nutrient management treatments included: (1) NE-based recommendation; (2) NE+GreenSeeker (GS; handheld sensors): NE recommendation supplemented with GS-guided application of N; (3) SR: state fertilizer recommendation; and (4) FFP or the farmers fertilizer application practice. These treatments were compared for agronomic productivity, economic profitability and total greenhouse gas emissions. Total greenhouse gas emissions from wheat production were estimated using the Cool Farm Tool. The results showed that both grain yield and net return were higher with NE-based strategies compared to FFP and SR. The estimated total carbon footprint (i.e. GWP per tonne of wheat grain production and per US$ of net return) was also lower for NE-based strategies than other nutrient management strategies. Thus, the use of precision nutrient management tools such as NE and GS are important for increasing wheat yields and farmer profits yet minimizing the environmental footprint of wheat production.