• Authors:
    • Young, M. H.
    • Breecker, D. O.
    • Meyer, N. A.
    • Litvak, M. E.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 78
  • Issue: 3
  • Year: 2014
  • Summary: The impacts of dynamic plant growth and microbial respiration have not been simulated in numerical models for calcite accumulation but are likely important because of their influence on variables governing calcite solubility. We simulated soil calcite dissolution and precipitation with HYDRUS-1D, which considers vegetation-soil interactions. We investigated vegetated vs. nonvegetated soil surfaces and the effect of plant phenology on seasonal calcite accumulation patterns in a silt loam soil. In each model run, calcite was leached from the shallow subsurface and redistributed deeper in the soil. Under identical boundary conditions, calcite accumulated in a narrower, more concentrated horizon (55% more calcite by mass) under a vegetated than a bare surface. The most significant periods of calcite accumulation corresponded with the onset of seasonal plant growth and root water uptake, when water was flowing up and focusing Ca ions in the root zone, resulting in the narrower, concentrated carbonate horizon. Therefore, accumulation of soil calcite occurred at temperatures 10°C higher for a simulation with summer plant growth {phenology based on C4 grass blue grama [Bouteloua gracilis (Kunth) Lag. ex Griffiths]} than for a simulation with spring plant growth occurred in the spring (intended to approximate a C3 plant community). Calcite was precipitated at or near thermodynamic equilibrium in the simulations, whereas previous empirical studies of calcic soils indicate the typical presence of calcite-supersaturated soil water and groundwater. More accurate, future simulations of CaCO3 accumulation should address this discrepancy, perhaps by incorporating a process that inhibits calcite precipitation, which might push calcite accumulation later in the year than simulated here.
  • Authors:
    • Kaspar, T. C.
    • Wiedenhoeft, M. H.
    • Moore, E. B.
    • Cambardella, C. A.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 78
  • Issue: 3
  • Year: 2014
  • Summary: Corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] farmers in the upper Midwest are showing increasing interest in winter cover crops. The effects of winter cover crops on soil quality in this region, however, have not been investigated extensively. The objective of this experiment was to determine the effects of a cereal rye (Secale cereale L.) winter cover crop after more than 9 yr in a corn silage-soybean rotation. Four cereal rye winter cover crop treatments were established in 2001: no cover crop, rye after soybean, rye after silage, and rye after both. Soil organic matter (SOM), particulate organic matter (POM), and potentially mineralizable N (PMN) were measured in 2010 and 2011 for two depth layers (0-5 and 5-10 cm) in both the corn silage and soybean phases of the rotation. In the 0- to 5-cm depth layer, a rye cover crop grown after both main crops had 15% greater SOM, 44% greater POM, and 38% greater PMN than the treatment with no cover crops. In general, the treatments that had a rye cover crop after both crops or after corn silage had a positive effect on the soil quality indicators relative to treatments without a cover crop or a cover crop only after soybean. Apparently, a rye cover crop grown only after soybean did not add enough residues to the soil to cause measureable changes in SOM, POM, or PMN. In general, rye cover crop effects were most pronounced in the top 5 cm of soil.
  • Authors:
    • Lal, R.
    • Al-Kaisi, M. M.
    • Olson, K. R.
    • Lowery, B.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 78
  • Issue: 2
  • Year: 2014
  • Summary: In agricultural land areas, no-tillage (NT) farming systems have been practiced to replace intensive tillage practices such as, moldboard plow (MP), chisel plow (CP), and other systems to improve many soil health indicators, and specifically to increase soil organic carbon (SOC) sequestration and reduce soil erosion. Numerous approaches to estimate the amounts and rates of SOC sequestration as a result of a switch to NT systems have been published, but there is a concern regarding protocol for assessing SOC especially for different tillage systems. Therefore, the objectives of this paper are to: (i) define and understand concepts of SOC sequestration, (ii) quantify SOC distribution and the methodology of measurements, (iii) address soil spatial variability at field- or landscape-scale for potential SOC sequestration, and (iv) consider proper field experimental design, including pretreatments baseline for SOC sequestration determination. For SOC sequestration to occur, as a result of a treatment applied to a land unit, all of the SOC sequestered must originate from the atmospheric CO2 pool and be transferred into the soil humus through land unit plants, plant residues, and other organic solids. The SOC stock present in soil humus at end of a study must be greater than the pretreatment SOC stock levels in the same land unit. However, one should recognize that a continuity equation showing drawdown in atmospheric concentration of CO2 may be difficult, if not impossible, to quantify. Therefore, SOC sequestration results of paired comparisons of NT to other conventional tillage systems with no pretreatments SOC baseline, and if the conventional system is not at a steady state, will likely be inaccurate where the potential for SOC loss exists in both systems. To unequivocally demonstrate that the SOC sequestration has occurred at a specific site, a temporal increase must be documented relative to pretreatment SOC content and linked attendant changes in soil properties and ecosystem services and functions with proper consideration given to soil spatial variability. Also, a standardized methodology that includes proper experimental design, pretreatment baseline, root zone soil depth consideration, and consistent method of SOC analysis must be used when determining SOC sequestration.
  • Authors:
    • Mahan, A.
    • Finlayson, J.
    • Payton, S.
    • Xue, P.
    • Rudd, Qing wu
    • Liu, J.
    • Reddy, S.
    • Lu
    • Akhunova, S.
    • Holalu, Nan yan
  • Source: JOURNAL OF PLANT PHYSIOLOGY
  • Volume: 171
  • Issue: 14
  • Year: 2014
  • Summary: Hard red winter wheat crops on the U.S. Southern Great Plains often experience moderate to severe drought stress, especially during the grain filling stage, resulting in significant yield losses. Cultivars TAM 111 and TAM 112 are widely cultivated in the region, share parentage and showed superior but distinct adaption mechanisms under water-deficit (WD) conditions. Nevertheless, the physiological and molecular basis of their adaptation remains unknown. A greenhouse study was conducted to understand the differences in the physiological and transcriptomic responses of TAM 111 and TAM 112 to WD stress. Whole-plant data indicated that TAM 112 used more water, produced more biomass and grain yield under WD compared to TAM 111. Leaf-level data at the grain filling stage indicated that TAM 112 had elevated abscisic acid (ABA) content and reduced stomatal conductance and photosynthesis as compared to TAM 111. Sustained WD during the grain filling stage also resulted in greater flag leaf transcriptome changes in TAM 112 than TAM 111. Transcripts associated with photosynthesis, carbohydrate metabolism, phytohormone metabolism, and other dehydration responses were uniquely regulated between cultivars. These results suggested a differential role for ABA in regulating physiological and transcriptomic changes associated with WD stress and potential involvement in the superior adaptation and yield of TAM 112.
  • Authors:
    • Running, S. W.
    • Bagne, K. E.
    • Moreno, A. L.
    • Reeves, M. C.
  • Source: CLIMATIC CHANGE
  • Volume: 126
  • Issue: 3-4
  • Year: 2014
  • Summary: The potential effects of climate change on net primary productivity (NPP) of U.S. rangelands were evaluated using estimated climate regimes from the A1B, A2 and B2 global change scenarios imposed on the biogeochemical cycling model, Biome-BGC from 2001 to 2100. Temperature, precipitation, vapor pressure deficit, day length, solar radiation, CO2 enrichment and nitrogen deposition were evaluated as drivers of NPP. Across all three scenarios, rangeland NPP increased by 0.26 % year(-1) (7 kg C ha(-1) year(-1)) but increases were not apparent until after 2030 and significant regional variation in NPP was revealed. The Desert Southwest and Southwest assessment regions exhibited declines in NPP of about 7 % by 2100, while the Northern and Southern Great Plains, Interior West and Eastern Prairies all experienced increases over 25 %. Grasslands dominated by warm season (C4 photosynthetic pathway) species showed the greatest response to temperature while cool season (C3 photosynthetic pathway) dominated regions responded most strongly to CO2 enrichment. Modeled NPP responses compared favorably with experimental results from CO2 manipulation experiments and to NPP estimates from the Moderate Resolution Imaging Spectroradiometer (MODIS). Collectively, these results indicate significant and asymmetric changes in NPP for U.S. rangelands may be expected.
  • Authors:
    • Caesar-TonThat, T.
    • Stevens, W. B.
    • Sainju, U. M.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 78
  • Issue: 3
  • Year: 2014
  • Summary: Management practices are needed to reduce soil C losses from croplands converted from Conservation Reserve Program (CRP) grassland. We evaluated the effects of irrigation, tillage, cropping system, and N fertilization on surface residue and soil organic C (SOC) at the 0- to 85-cm depth in relation to crop yields in a sandy loam soil from 2005 to 2011 in croplands converted from CRP in western North Dakota. Treatments were two irrigation practices (irrigated vs. nonirrigated) as the main plot and six cropping systems [CRP, conventional till malt barley (Hordeum vulgare L.) with N fertilizer (CTBN), conventional till malt barley without N fertilizer (CTBO), no-till malt barley- pea (Pisum sativum L.) with N fertilizer (NTB-P), no-till malt barley with N fertilizer (NTBN), and no-till malt barley without N fertilizer (NTBO)] as the split plot arranged in a randomized complete block with three replications. Soil surface residue amount and C content were greater in CRP and NTBN than the other cropping systems. At 0 to 5 cm, SOC was greater in irrigated CRP, but at 0 to 85 cm it was greater in nonirrigated NTBN than most other treatments. At 0 to 20 cm, SOC increased by 0.26 to 1.21 Mg C ha-1 yr-1 in NTB-P and CRP but decreased by 0.02 to 0.68 Mg C ha-1 yr-1 in other cropping systems. Surface residue C and SOC at 0 to 10 cm were related to annualized crop grain yield (R2 = 0.45-0.77, P x≤ 0.12, n = 10). Because of positive C sequestration rate and favorable crop yields, NTB-P may be used as a superior management option to reduce soil C losses and sustain yields in croplands converted from CRP in the northern Great Plains.
  • Authors:
    • Xu, Y. J.
    • Zhong, B.
  • Source: ENVIRONMENTAL MONITORING AND ASSESSMENT
  • Volume: 186
  • Issue: 10
  • Year: 2014
  • Summary: This study aimed to assess the degree of potential temperature and precipitation change as predicted by the HadCM3 (Hadley Centre Coupled Model, version 3) climate model for Louisiana, and to investigate the effects of potential climate change on surface soil organic carbon (SOC) across Louisiana using the Rothamsted Carbon Model (RothC) and GIS techniques at the watershed scale. Climate data sets at a grid cell of 0.5A degrees x 0.5A degrees for the entire state of Louisiana were collected from the HadCM3 model output for three climate change scenarios: B2, A2, and A1F1, that represent low, higher, and even higher greenhouse gas emissions, respectively. Geo-referenced datasets including USDA-NRCS Soil Geographic Database (STATSGO), USGS Land Cover Dataset (NLCD), and the Louisiana watershed boundary data were gathered for SOC calculation at the watershed scale. A soil carbon turnover model, RothC, was used to simulate monthly changes in SOC from 2001 to 2100 under the projected temperature and precipitation changes. The simulated SOC changes in 253 watersheds from three time periods, 2001-2010, 2041-2050, and 2091-2100, were tested for the influence of the land covers and emissions scenarios using SAS PROC GLIMMIX and PDMIX800 macro to separate Tukey-Kramer (p < 0.01) adjusted means into letter comparisons. The study found that for most of the next 100 years in Louisiana, monthly mean temperature under all three emissions projections will increase; and monthly precipitation will, however, decrease. Under three emission scenarios, A1FI, A2, and B2, the mean SOC in the upper 30-cm depth of Louisiana forest soils will decrease from 33.0 t/ha in 2001 to 26.9, 28.4, and 29.2 t/ha in 2100, respectively; the mean SOC of Louisiana cropland soils will decrease from 44.4 t/ha in 2001 to 36.3, 38.4, and 39.6 t/ha in 2100, respectively; the mean SOC of Louisiana grassland soils will change from 30.7 t/ha in 2001 to 25.4, 26.6, and 27.0 t/ha in 2100, respectively. Annual SOC changes will be significantly different among the land cover classes including evergreen forest, mixed forest, deciduous forest, small grains, row crops, and pasture/hay (p < 0.0001), emissions scenarios (p < 0.0001), and their interactions (p < 0.0001).
  • Authors:
    • Lamb, J. A.
    • Fassbinder, J.
    • Baker, J. M.
  • Source: BioEnergy Research
  • Volume: 7
  • Issue: 2
  • Year: 2014
  • Summary: Corn stover removal, whether for silage, bedding, or bioenergy production, could have a variety of environmental consequences through its effect on soil processes, particularly N2O production and soil respiration. Because these effects may be episodic in nature, weekly snapshots with static chambers may not provide a complete picture. We adapted commercially available automated soil respiration chambers by incorporating a portable N2O analyzer, allowing us to measure both CO2 and N2O fluxes on an hourly basis through two growing seasons in a corn field in southern Minnesota, from spring 2010 to spring 2012. This site was part of a USDA multilocation research project for five growing seasons, 2008-2012, with three levels of stover removal: zero, full, and intermediate. Initially in spring 2010, two chambers were placed in each of the treatments, but following planting in 2011, the configuration was changed, with four chambers installed on zero removal plots and four on full removal plots. The cumulative data revealed no significant difference in N2O emission as a function of stover removal. CO2 loss from the full removal plots was slightly lower than that from the zero removal plots, but the difference between treatments was much smaller than the amount of C removed in the residue, implying loss of soil carbon from the full removal plots. This is consistent with soil sampling data, which showed that in five of six sampled blocks, the SOC change in the full removal treatments was negative relative to the zero removal plots. We conclude that (a) full stover removal may have little impact on N2O production, and (b) while it will reduce soil CO2 production, the reduction will not be commensurate with the decrease in fresh carbon inputs and, thus, will result in SOC loss.
  • Authors:
    • Bonin, C. L.
    • Lal, R.
  • Source: GCB Bioenergy
  • Volume: 6
  • Issue: 1
  • Year: 2014
  • Summary: Biofuel crops may help achieve the goals of energy-efficient renewable ethanol production and greenhouse gas (GHG) mitigation through carbon (C) storage. The objective of this study was to compare the aboveground biomass yields and soil organic C (SOC) stocks under four crops (no-till corn, switchgrass, indiangrass, and willow) 7years since establishment at three sites in Ohio to determine if high-yielding biofuel crops are also capable of high levels of C storage. Corn grain had the highest potential ethanol yields, with an average of more than 4100Lha(-1), and ethanol yields increased if both corn grain and stover were converted to biofuel, while willow had the lowest yields. The SOC concentration in soils under biofuels was generally unaffected by crop type; at one site, soil in the top 10cm under willow contained nearly 13Mg Cha(-1) more SOC (or 29% more) than did soils under switchgrass or corn. Crop type affected SOC content of macroaggregates in the top 10cm of soil, where macroaggregates in soil under corn had lower C, N and C:N ratios than those under perennial grasses or trees. Overall, the results suggest that no-till corn is capable of high ethanol yields and equivalent SOC stocks to 40cm depth. Long-term monitoring and measurement of SOC stocks at depth are required to determine whether this trend remains. In addition, ecological, energy, and GHG assessments should be made to estimate the C footprint of each feedstock.
  • Authors:
    • Castellano, M. J.
    • Sawyer, J. E.
    • Jeske, E. S.
    • Hofmockel, K. S.
    • Drijber, R. A.
    • Bach, E. M.
    • Brown, K. H.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 4
  • Year: 2014
  • Summary: Global maize production alters an enormous soil organic C (SOC) stock, ultimately affecting greenhouse gas concentrations and the capacity of agroecosystems to buffer climate variability. Inorganic N fertilizer is perhaps the most important factor affecting SOC within maize-based systems due to its effects on crop residue production and SOC mineralization. Using a continuous maize cropping system with a 13 year N fertilizer gradient (0-269kg Nha(-1)yr(-1)) that created a large range in crop residue inputs (3.60-9.94 Mgdry matter ha(-1)yr(-1)), we provide the first agronomic assessment of long-term N fertilizer effects on SOC with direct reference to N rates that are empirically determined to be insufficient, optimum, and excessive. Across the N fertilizer gradient, SOC in physico-chemically protected pools was not affected by N fertilizer rate or residue inputs. However, unprotected particulate organic matter (POM) fractions increased with residue inputs. Although N fertilizer was negatively linearly correlated with POM C/N ratios, the slope of this relationship decreased from the least decomposed POM pools (coarse POM) to the most decomposed POM pools (fine intra-aggregate POM). Moreover, C/N ratios of protected pools did not vary across N rates, suggesting little effect of N fertilizer on soil organic matter (SOM) after decomposition of POM. Comparing a N rate within 4% of agronomic optimum (208kg Nha(-1)yr(-1)) and an excessive N rate (269kg Nha(-1)yr(-1)), there were no differences between SOC amount, SOM C/N ratios, or microbial biomass and composition. These data suggest that excessive N fertilizer had little effect on SOM and they complement agronomic assessments of environmental N losses, that demonstrate N2O and NO3 emissions exponentially increase when agronomic optimum N is surpassed.