• Authors:
    • Daigh,A. L.
    • Sauer,T.
    • Xiao,X. H.
    • Horton,R.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 3
  • Year: 2015
  • Summary: Models of instantaneous soil-surface CO 2 efflux (SCE ins) are critical for understanding the potential drivers of soil C loss. Several simple SCE ins models have been reported in the literature. Our objective was to compare and validate selected soil temperature ( Ts)- and water content (theta v)-based equations for modeling SCE ins among a variety of cropping systems and land management practices. Soil-surface CO 2 effluxes were measured and modeled for grain-harvested corn ( Zea mays L.)-soybean [ Glycine max (L.) Merr.] rotations, grain- and stover-harvested continuous corn systems with and without a cover crop, and reconstructed prairies with and without N fertilization on soils with subsurface drainage. Soil-surface CO 2 effluxes, Ts, and theta v were measured from 2008 to 2011. Models calibrated with weekly measured SCE ins, Ts, and theta v throughout the growing season produced lower root mean squared error (RMSE) than models calibrated with several weeks of hourly measured data. Model selection significantly affected SCE ins estimations, with models that use only Ts parameters having lower RMSE than models that use both Ts and theta v. However, the model that produced the lowest RMSE during validation estimated growing-season SCE that did not significantly differ from numerical integration of weekly measured SCE ins. All models had similar residual errors with autocorrelated trends at monthly, weekly, and hourly scales. Autoregressive moving average functions were able to precisely describe the temporal errors. To accurately model SCE ins and scale across time, improvement of temporal errors in Ts- and theta v-based SCE ins models is needed to obtain accurate and precise closure of C balances for managed and natural ecosystems.
  • Authors:
    • Fan,T. -T
    • Wang,Y. -J
    • Li,C. -B
    • Zhou,D. -M
    • Friedman,S. P.
  • Source: Soil Science Society of America Journal
  • Volume: 79
  • Issue: 3
  • Year: 2015
  • Summary: Wien effect measurements were used to study the effect of organic matter on the interactions between divalent cations and soil clay particles of two black soil samples containing organic matter (OM) at 54.4 and 12.3 g kg-1 in the top (0-20-cm) and bottom (100-120-cm) horizons, respectively, and a sample of OM-free black soil, all saturated with Cd2+, Cu2+, Pb2+, and with Ca2+ as a reference cation. The weak-field electrical conductivities of suspensions of the top and bottom horizons and OM-free black soil samples were 0.021 to 0.033, 0.011 to 0.021, and 0.0065 to 0.0082 mS cm-1, respectively. The mean free binding energies of the cations in the same soil sample suspensions were 5.5 to 7.3, 7.3 to 9.3, and 9.6 to 10 kJ mol-1, respectively. The mean free adsorption energies of all cations increased with field strength and were in the order OM-free > bottom horizon > top horizon. At field strengths >100 kV cm-1, in the top-horizon soil, the adsorption energies of Ca were 0.21 to 0.72 kJ mol-1, those of Cd and Cu were similar to one another at 0.01 to 0.25 kJ mol-1, and those of Pb were close to zero, while in the bottom horizon soil, the adsorption energies of the various cations were in descending order: Ca > Cd > Pb > Cu, and in the OM-free soil the order of the adsorption energies of the various cations were Cd ˜ Cu ˜ Ca > Pb. The humus basically increased the negative electrokinetic potentials of the clay-size-fraction particles of the three black soil samples saturated with Ca, Cd, Cu, or Pb. © Soil Science Society of America, 5585 Guilford Rd., Madison Wl 53711 USA.
  • Authors:
    • Messerli,J.
    • Bertrand,A.
    • Bourassa,J.
    • Belanger,G.
    • Castonguay,Y.
    • Tremblay,G.
    • Baron,V.
    • Seguin,P.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 3
  • Year: 2015
  • Summary: The increase in atmospheric carbon dioxide concentration ([CO 2]) and consequent increase in air temperature is expected to have significant effects on plant growth and nutritive value. Studies examining the effects of elevated [CO 2] on plants under field conditions have been limited by the inherent difficulty to modify air composition in open air. Here we describe an efficient and inexpensive open-top chamber (OTC) system designed to study the effects of elevated atmospheric [CO 2] and temperature on perennial alfalfa-timothy ( Medicago sativa L.)-( Phleum pratense L.) mixture. The design and construction of these OTCs are described in detail, along with cost estimation for each component. Eight OTCs, each with 1.2 m 2 of ground area (four with elevated [CO 2] and four with ambient [CO 2]) were fabricated and four control plots of the same dimension were established to assess the chamber effects on plant responses to CO 2. The [CO 2] in elevated-CO 2 chambers fell 93% of the time within 20% of the targeted 600 mol mol -1 CO 2, based on 10 min averages. The CO 2 consumption in elevated-CO 2 chambers averaged 3.0 kg CO 2 m -2 d -1. To ensure that the environment within OTCs was similar to the surrounding field, growing conditions were determined in all chambers and control plots. Adequate light transmission was observed compared to control plots (93%) and the temperature increase was 0.7°C on average. After two growing seasons of continued use, this system has proven its effectiveness for studying the effects of CO 2 and climate change in the field at low cost.
  • Authors:
    • Miao,Shujie
    • Qiao,Yunfa
    • Zhang,Futao
  • Source: Polish Journal of Environmental Science
  • Volume: 24
  • Issue: 3
  • Year: 2015
  • Summary: In converting cropland to grassland and forest, more carbon is sequestered in grassland soil and forest biomass, but the mitigation of global warming potential (GWP) is not clear. In this study, we use the lon-gterm conversion from cropland to grassland (28 y) and forest (14 y) to comprehensively assess the impact on GWP of soil carbon (C), nitrogen (N), CO2 and N2O emissions. The results showed that compared to the original cropland, conversion to grassland increased soil C content by 51.1%, soil N content by 28.4%, soil C stock (SCS) by four times, CO2 emission by 17%, and N2O emission by 40%; soil N stock (SNS) decreased by half. The corresponding values after afforestation were 7.2%, 5.2%, three times, 3%, -80%, and half, respectively. Overall GWP in the cropland system was calculated using the fuel used for farming production, the change in soil C, and N2O emissions. Due to large C sequestration, the GWP of conversion to grassland (-1667 kg CO2-C equivalent ha(-1).y(-1)) and forest (-324 kg CO2-C equivalent ha(-1).y(-1)) were significantly lower than the cropland system (755 kg CO2-C equivalent ha(-1).y(-1)). The relationship between GWP and greenhouse gas, between GWP and the change of total C and N, suggest that in rain-fed agricultural systems in northeast China, the conversion from cropland to grassland and forest can mitigate GWP through changing CO2 and N2O emissions.
  • Authors:
    • Schlegel,A. J.
    • Assefa,Y.
    • Bond,H. D.
    • Wetter,S. M.
    • Stone,L. R.
  • Source: Soil Science Society of America Journal
  • Volume: 79
  • Issue: 3
  • Year: 2015
  • Summary: Application of animal waste to cropland provides a method of waste disposal and benefits both soil and crops. The objective of this study was to evaluate the long-term effects of land application of animal waste and inorganic fertilizer on selected soil chemical and physical properties. The animal waste applications were conducted from 1999 through 2008 near Tribune, KS, with 10 treatments (three levels each of cattle manure and swine effluent [P, N, and 2N], three levels of N fertilizer, and a control). Soil chemical and physical properties were measured to evaluate the effect of 10 yr of application of these treatments. Cattle manure application at the 2N level increased Mehlich-3 P, total N, total C, and organic matter (OM) concentrations to about 19, 2.8, 2.5, and 2.5 times, respectively, compared with those of the untreated check. Physical properties of the soil such as water content at -1.5 MPa, modulus of rupture, Proctor maximum bulk density, and optimum water content for compaction improved with the application of cattle manure. Highly significant relationships (P < 0.001) were observed between soil OM and soil water content at -1.5 MPa, both Proctor maximum and field bulk densities, optimum water content for compaction, and steady-state infiltration rate. Cattle manure treatments improved soil resistance to compaction, largely due to the additional OM that builds in soil with the application of cattle manure. © Soil Science Society of America, 5585 Guilford Rd., Madison Wl 53711 USA.
  • Authors:
    • Zuber,S. M.
    • Behnke,G. D.
    • Nafziger,E. D.
    • Villamil,M. B.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 3
  • Year: 2015
  • Summary: Recent increases in corn ( Zea mays L.) production in the U.S. Corn Belt have necessitated the conversion of rotations to continuous corn, and an increase in the frequency of tillage. The objective of this study was to assess the effect of rotation and tillage on soil physical and chemical properties in soils typical of Illinois. Sequences of continuous corn (CCC), 2-yr corn-soybean [ Glycine max (L.) Merr.] (CS) rotation, 3-yr corn-soybean-wheat ( Triticum aestivum L.) (CSW) rotation, and continuous soybean (SSS) were split into conventional tillage (CT) and no-till (NT) subplots at two Illinois sites. After 15 yr, bulk density (BD) under NT was 2.4% greater than under CT. Water aggregate stability (WAS) was 0.84 kg kg -1 under NT compared to 0.81 kg kg -1 under CT. Similarly, soil organic carbon (SOC) and total nitrogen (TN) were greater under NT than under CT with SOC values for 0 to 60 cm of 96.0 and 91.0 Mg ha -1 and TN values of 8.87 and 8.40 Mg ha -1 for NT and CT, respectively. Rotations affected WAS, TN, and K levels with WAS being greatest for the CSW rotation at 0.87 kg kg -1, decreasing with more soybean years (CS, 0.82 kg kg -1 and SSS, 0.79 kg kg -1). A similar pattern was detected for TN and exchangeable K. Results indicated that while the use of NT improved soil quality, long-term implementation of continuous corn had similar soil quality parameters to those found under a corn-soybean rotation.
  • Authors:
    • Cuello,J. P.
    • Hwang HyunYoung
    • Gutierrez,J.
    • Kim SangYoon
    • Kim PilJoo
  • Source: Applied Soil Ecology
  • Volume: 91
  • Issue: 1
  • Year: 2015
  • Summary: Plastic film mulching (PFM) is an agricultural management practice that is commonly used to suppress weed growth. However, its effect on greenhouse gas (GHG) emissions has not been well evaluated. To investigate the effect of PFM on GHG emissions and crop productivities, black PFM and no-mulching plots were installed as the main treatment, and three sub-treatments, chemical fertilizer (NPK) and two green manures, were arranged within each main treatment. Two cover crops (hairy vetch and barley) with different carbon/nitrogen (C/N) ratios were cultivated in the two green manure treatments during the fallow season. The aboveground biomasses of vetch (23-25 Mg fresh weight ha -1) and barley (10-11 Mg ha -1) were incorporated before maize seedling transplanting. Maize was cultivated without chemical fertilization in the two green manure treatments, whereas the recommended chemical fertilizers were applied in the NPK treatment. During two annual cropping seasons, the emission rates of methane (CH 4) and nitrous oxide (N 2O) gases were simultaneously monitored once a week using the closed-chamber method. Total global warming potential (GWP) was calculated as CO 2 equivalents by multiplying the seasonal CH 4 and N 2O fluxes by 25 and 298, respectively. Irrespective of soil amendments, PFM significantly increased soil temperature and moisture content by a mean of 2°C and 0.04 m 3 m -3 over no-mulching, respectively. Plastic film mulching increased grain productivity by 8-33% over no-mulching. However, PFM significantly decreased soil organic matter content and largely increased the two major GHG emissions. As a result, PFM increased the total GWP by 12-82% over no-mulching, irrespective of the soil amendments. In conclusion, more sustainable mulching systems should be developed that can sustain soil quality and minimize environmental impacts, including GHG emissions.
  • Authors:
    • Emery,I.
    • Mosier,N.
  • Source: GCB Bioenergy
  • Volume: 7
  • Issue: 4
  • Year: 2015
  • Summary: Little is known about the contributions of biomass feedstock storage to the net greenhouse gas emissions from cellulosic biofuels. Direct emissions of methane and nitrous oxide during decomposition in storage may contribute substantially to the global warming potential of biofuels. In this study, laboratory-scale bales of switchgrass and corn stover were stored under a range of moisture (13.0-32.9%) and temperature (5-35°C) conditions and monitored for O 2 consumption and CO 2, CH 4, and N 2O production over 8 weeks. Gas concentrations and emissions rates were highly variable within and between experimental groups. Stover bales produced higher CO 2 concentrations ( P=0.0002) and lower O 2 ( P<0.0001) during storage than switchgrass bales. Methane concentrations (1.8-2100 ppm) were inversely correlated with bale moisture ( P<0.05), with emissions rates ranging from 4.4-914.9 g kg -1 DM day -1. Nitrous oxide concentrations ranged from 0 to 31 ppm, and emissions from switchgrass bales inversely correlated with temperature and moisture ( P<0.0001). Net global warming potential from each treatment (0-2.4 gCO 2e kg -1 DM) suggests that direct emission of methane and nitrous oxide from aerobically stored feedstocks have a small effect on net global warming potential of cellulosic biofuels.
  • Authors:
    • Knapp,A. K.
    • Hoover,D. L.
    • Wilcox,K. R.
    • Avolio,M. L.
    • Koerner,S. E.
    • Pierre,K. J. la
    • Loik,M. E.
    • Luo,Y. Q.
    • Sala,O. E.
    • Smith,M. D.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 7
  • Year: 2015
  • Summary: Climate change is intensifying the hydrologic cycle and is expected to increase the frequency of extreme wet and dry years. Beyond precipitation amount, extreme wet and dry years may differ in other ways, such as the number of precipitation events, event size, and the time between events. We assessed 1614 long-term (100 year) precipitation records from around the world to identify key attributes of precipitation regimes, besides amount, that distinguish statistically extreme wet from extreme dry years. In general, in regions where mean annual precipitation (MAP) exceeded 1000 mm, precipitation amounts in extreme wet and dry years differed from average years by ~40% and 30%, respectively. The magnitude of these deviations increased to >60% for dry years and to >150% for wet years in arid regions (MAP 99th percentile of all events); these occurred twice as often in extreme wet years compared to average years. In contrast, these large precipitation events were rare in extreme dry years. Less important for distinguishing extreme wet from dry years were mean event size and frequency, or the number of dry days between events. However, extreme dry years were distinguished from average years by an increase in the number of dry days between events. These precipitation regime attributes consistently differed between extreme wet and dry years across 12 major terrestrial ecoregions from around the world, from deserts to the tropics. Thus, we recommend that climate change experiments and model simulations incorporate these differences in key precipitation regime attributes, as well as amount into treatments. This will allow experiments to more realistically simulate extreme precipitation years and more accurately assess the ecological consequences.
  • Authors:
    • Miao ShuJie
    • Qiao YunFa
    • Zhang FuTao
  • Source: Polish Journal of Environmental Studies
  • Volume: 24
  • Issue: 3
  • Year: 2015
  • Summary: In converting cropland to grassland and forest, more carbon is sequestered in grassland soil and forest biomass, but the mitigation of global warming potential (GWP) is not clear. In this study, we use the longterm conversion from cropland to grassland (28 y) and forest (14 y) to comprehensively assess the impact on GWP of soil carbon (C), nitrogen (N), CO 2, and N 2O emissions. The results showed that compared to the original cropland, conversion to grassland increased soil C content by 51.1%, soil N content by 28.4%, soil C stock (SCS) by four times, CO 2 emission by 17%, and N 2O emission by 40%; soil N stock (SNS) decreased by half. The corresponding values after afforestation were 7.2%, 5.2%, three times, 3%, -80%, and half, respectively. Overall GWP in the cropland system was calculated using the fuel used for farming production, the change in soil C, and N 2O emissions. Due to large C sequestration, the GWP of conversion to grassland (-1667 kg CO 2-C equivalent ha -1.y -1) and forest (-324 kg CO 2-C equivalent ha -1.y -1) were significantly lower than the cropland system (755 kg CO 2-C equivalent ha -1.y -1). The relationship between GWP and greenhouse gas, between GWP and the change of total C and N, suggest that in rain-fed agricultural systems in northeast China, the conversion from cropland to grassland and forest can mitigate GWP through changing CO 2 and N 2O emissions.