• Authors:
    • Kushnak, G. D.
    • Riveland, N.
    • Eckhoff, J. L.
    • Wichman, D. M.
    • Carlson, G. R.
    • Kephart, K. D.
    • Cook, C. R.
    • Stougaard, R. N.
    • Berg, J. E.
    • Nash, D. L.
    • Bruckner, P. L.
  • Source: Crop Science
  • Volume: 46
  • Issue: 3
  • Year: 2006
  • Summary: MT1159CL (Reg. No. CV-992, PI 641221) hard red winter wheat ( Triticum aestivum) was developed by Montana Agricultural Experiment Station and released in September 2004, for its tolerance to imazamox herbicide, adaptation to dryland production in central and south-central Montana, and improved milling and bread baking qualities relative to other available Clearfield winter wheat cultivars. This double-haploid line developed using the wheat * maize hybridization method from the cross FS2/Tiber (PI 517194) has moderate resistance to stripe rust ( Puccinia striiformis f.sp. tritici).
  • Authors:
    • Yang, H. S.
    • Amos, B.
    • Burba, G. G.
    • Suyker, A. E.
    • Arkebauer, T. J.
    • Knops, J. M.
    • Walters, D. T.
    • Cassman, K. G.
    • Dobermann, A.
    • Verma, S. B.
    • Ginting, D.
    • Hubbard, K. G.
    • Gitelson, A. A.
    • Walter-Shea, E. A.
  • Source: Agricultural and Forest Meteorology
  • Volume: 131
  • Issue: 1-2
  • Year: 2005
  • Summary: Carbon dioxide exchange was quantified in maize ( Zea mays)-soybean ( Glycine max) agroecosystems employing year-round tower eddy covariance flux systems and measurements of soil C stocks, CO 2 fluxes from the soil surface, plant biomass, and litter decomposition. Measurements were made in 3 cropping systems: (a) irrigated continuous maize; (b) irrigated maize-soybean rotation; and (c) rainfed maize-soybean rotation during 2001-2004. The study was conducted at the University of Nebraska Agricultural Research and Development Centre near Mead, Nebraska, USA. Because of a variable cropping history, all 3 sites were uniformly tilled by disking prior to initiation of the study. Since then, all sites are under no-till, and crop and soil management follow best management practices prescribed for production-scale systems. Cumulative daily gain of C by the crops (from planting to physiological maturity), determined from the measured eddy covariance CO 2 fluxes and estimated heterotrophic respiration, compared well with the measured total above and belowground biomass. Two contrasting features of maize and soyabean CO 2 exchange are notable. The value of integrated gross primary productivity (GPP) for both irrigated and rainfed maize over the growing season was substantially larger (ca. 2:1 ratio) than that for soyabean. Also, soyabean lost a larger portion (0.80-0.85) of GPP as ecosystem respiration (due, in part, to the large amount of maize residue from the previous year), as compared to maize (0.55-0.65). Therefore, the seasonally integrated net ecosystem production (NEP) in maize was larger by a 4:1 ratio (approximately), as compared to soyabean. Enhanced soil moisture conditions in the irrigated maize and soyabean fields caused an increase in ecosystem respiration, thus eliminating any advantage of increased GPP and giving about the same values for the growing season NEP as the rainfed fields. On an annual basis, the NEP of irrigated continuous maize was 517, 424, and 381 g C m -2 year -1, respectively, during the 3 years of our study. In rainfed maize, the annual NEP was 510 and 397 g C m -2 year -1 in years 1 and 3, respectively. The annual NEP in the irrigated and rainfed soyabean fields were in the range of -18 to -48 g C m -2. Accounting for the grain C removed during harvest and the CO 2 released from irrigation water, our tower eddy covariance flux data over the first 3 years suggest that, at this time: (a) the rainfed maize-soybean rotation system is C neutral; (b) the irrigated continuous maize is nearly C neutral or a slight source of C; and (c) the irrigated maize-soybean rotation is a moderate source of C. Direct measurement of soil C stocks could not detect a statistically significant change in soil organic carbon during the first 3 years of no-till farming in these 3 cropping systems.
  • Authors:
    • Hons, F.
    • Wright, A.
  • Source: Biology and Fertility of Soils
  • Volume: 41
  • Issue: 2
  • Year: 2005
  • Summary: Management practices, such as no tillage (NT) and intensive cropping, have potential to increase C and N sequestration in agricultural soils. The objectives of this study were to investigate the impacts of conventional tillage (CT), NT, and cropping intensity on soil organic C (SOC) and N (SON) sequestration and on distribution within aggregate-size fractions in a central Texas soil after 20 years of treatment imposition. Tillage regime and cropping sequence significantly impacted both SOC and SON sequestration. At 0-5 cm, NT increased SOC storage compared to CT by 33% and 97% and SON storage by 25% and 117% for a sorghum/wheat/soybean (SWS) rotation and a continuous sorghum monoculture, respectively. Total SOC and SON storage at both 0-5 and 5-15 cm was greater for SWS than continuous sorghum regardless of tillage regime. The majority of SOC and SON storage at 0-5 cm was observed in 250-m to 2-mm aggregates, and at 5-15 cm, in the >2-mm and 250-m to 2-mm fractions. Averaged across cropping sequences at 0-5 cm, NT increased SOC storage compared to CT by 212%, 96%, 0%, and 31%, and SON storage by 122%, 92%, 0%, and 37% in >2-mm, 250-m to 2-mm, 53- to 250-m, and
  • Authors:
    • Hons, F.
    • Wright, A.
  • Source: Soil Science Society of America Journal
  • Volume: 69
  • Issue: 1
  • Year: 2005
  • Summary: No-tillage (NT) has the potential to enhance C and N sequestration in agricultural soils of the southern USA, but results may vary with crop species. The objectives of this study were to investigate the impacts of NT, conventional tillage (CT), and crop species on soil organic carbon (SOC) and nitrogen (SON) sequestration and distribution within aggregate-size fractions in a central Texas soil after 20 yr of management. No-tillage increased SOC over CT at the 0- to 5-cm depth by 97, 47, and 72%, and SON by 117, 56, and 44% for continuous grain sorghum [ Sorghum bicolor (L.) Moench], wheat ( Triticum aestivum L.), and soyabean [ Glycine max (L.) Merr.], respectively. Crop species had significant impacts on SOC and SON sequestration. On average, the wheat monoculture had greater SOC (9.23 Mg C ha -1) at the 0- to 5-cm depth than sorghum (6.75 Mg C ha -1) and soyabean (7.05 Mg C ha -1). No-tillage increased the proportion of >2-mm and 250-m to 2-mm macroaggregate fractions in soil compared with CT. At the 0- to 5-cm depth, NT increased SOC compared with CT by 158% in macroaggregate fractions, but only 40% in 2-mm, 250-m to 2-mm, 53- to 250-m, and
  • Authors:
    • Hons, F.
    • Wright, A.
  • Source: Soil & Tillage Research
  • Volume: 84
  • Issue: 1
  • Year: 2005
  • Summary: No tillage (NT) and increased cropping intensity have potential for enhanced C and N sequestration in agricultural soils. The objectives of this study were to investigate the impacts of conventional tillage (CT), NT, and multiple cropping sequences on soil organic C (SOC) and N (SON) sequestration and on distribution within aggregate-size fractions in a southcentral Texas soil at the end of 20 years of treatment imposition. Soil organic C and SON sequestration were significantly greater under NT than CT for a grain sorghum [ Sorghum bicolor (L.) Moench]/wheat ( Triticum aestivum L.)/soybean [ Glycine max (L.) Merr.] rotation (SWS), a wheat/soybean doublecrop (WS), and a continuous wheat monoculture (CW) at 0-5 cm and for the SWS rotation at 5-15 cm. At 0-5 cm, NT increased SOC storage compared to CT by 62, 41, and 47% and SON storage by 77, 57, and 56%, respectively, for SWS, WS, and CW cropping sequences. Increased cropping intensity failed to enhance SOC or SON sequestration at either soil depth compared to the CW monoculture. No-tillage increased the proportion of macroaggregates (>2 mm) at 0-5 cm but not at 5-15 cm. The majority of SOC and SON storage under both CT and NT was observed in the largest aggregate-size fractions (>2 mm, 250 m to 2 mm). The use of NT significantly improved soil aggregation and SOC and SON sequestration in surface but not subsurface soils.
  • Authors:
    • Atwood,J. D.
    • Izaurralde, R. C.
    • Williams, J. R.
    • He, X.
    • Wang, X.
  • Source: Transactions of the ASAE
  • Volume: 48
  • Issue: 3
  • Year: 2005
  • Summary: Modeling biophysical processes is a complex endeavor because of large data requirements and uncertainty in model parameters. Model predictions should incorporate, when possible, analyses of their uncertainty and sensitivity. The study incorporated uncertainty analysis on EPIC (Environmental Policy Impact Calculator) predictions of corn (Zea mays L.) yield and soil organic carbon (SOC) using generalized likelihood uncertainty estimation (GLUE). An automatic parameter optimization procedure was developed at the conclusion of sensitivity analysis, which was conducted using the extended Fourier amplitude sensitivity test (FAST). The analyses were based on an experimental field under 34-year continuous corn with five N treatments at the Arlington Agricultural Research Station in Wisconsin. The observed average annual yields per treatment during 1958 to 1991 fell well within the 90% confidence interval (CI) of the annually averaged predictions. The width of the 90% CI bands of predicted average yields ranged from 0.31 to 1.6 Mg ha-1. The predicted means per treatment over simulations were 3.26 to 6.37 Mg ha-1, with observations from 3.28 to 6.4 Mg ha-1. The predicted means of yearly yield over simulations were 1.77 to 9.22 Mg ha-1, with observations from 1.35 to 10.22 Mg ha-1. The 90% confidence width for predicted yearly SOC in the top 0.2 m soil was 285 to 625 g C m-2, while predicted means were 5122 to 6564 g C m-2 and observations were 5645 to 6733 g C m-2. The optimal parameter set identified through the automatic parameter optimization procedure gave an R2 of 0.96 for average corn yield predictions and 0.89 for yearly SOC. EPIC was dependable, from a statistical point of view, in predicting average yield and SOC dynamics.
  • Authors:
    • West,Tristram O.
    • West,Tristram O.
    • McBride,Allen C.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 108
  • Issue: 2
  • Year: 2005
  • Summary: Agricultural lime (aglime) is commonly applied to soils in the eastern U.S. to increase soil pH. Aglime includes crushed limestone (CaCO3) and crushed dolomite (MgCa(CO3)2). Following the supposition by the Intergovernmental Panel on Climate Change (IPCC) that all C in aglime is eventually released as CO2 to the atmosphere, the U.S. EPA estimated that 9 Tg (Teragram = 1012g=106metric tonne) CO2 was emitted from an approximate 20 Tg of applied aglime in 2001. A review of historic data on aglime production and use indicates that 30 Tg may better represent the annual U.S. consumption of aglime. More importantly, our review of terrestrial and ocean C dynamics indicates that it is unlikely that all C from aglime is released to the atmosphere following application to soils. On the contrary, the primary pathway for aglime dissolution is reaction with carbonic acid (H2CO3) which results in uptake of CO2. Depending on soil pH and nitrogen fertilizer use, a fraction of aglimemay react with strong acid sources such as nitric acid (HNO3), thereby releasing CO2. Data on soil leaching and river transport of calcium (Ca2+) and bicarbonate (HCO3) suggest that a significant portion of dissolved aglime constituents may leach through the soil and be transported by rivers to the ocean. Much of the fraction transported to the ocean will precipitate as CaCO3. Bicarbonate remaining in the soil profile is expected to release CO2 following re-acidification of the soil over time. Our analysis indicates that net CO2 emissions from the application of aglime is 0.059 Mg C per Mg limestone and 0.064 Mg C per Mg dolomite. This is in contrast to IPCC estimates of 0.12 and 0.13Mg C perMg limestone and dolomite, respectively. Based on our best estimate, the application of 20–30 Tg of aglime in the U.S., consisting of 80% limestone and 20% dolomite, would have resulted in a net 4.4–6.6 Tg CO2 emissions in 2001.
  • Authors:
    • Wu, J. J.
  • Source: American Journal of Agricultural Economics
  • Volume: 87
  • Issue: 1
  • Year: 2005
  • Summary: Given that the Conservation Reserve Program (CRP) costs taxpayers $2 billion per year and remains the largest conservation program in U. S. history, Roberts and Bucholtz are to be commended for revisiting the slippage issue. However, their central point that regional variation in CRP acreage is endogenous is inconsistent with CRP implementation rules and data. Thus, it is not surprising that the null hypothesis of exogeneity cannot be rejected by statistical tests.
  • Authors:
    • Ginting, D.
    • Eghball, B.
  • Source: Soil Science Society of America Journal
  • Volume: 69
  • Issue: 3
  • Year: 2005
  • Summary: Field experiments were conducted to determine optimal time during the day for N 2O flux determination and to evaluate the effects of wheel traffic and soil parameters on N 2O fluxes following urea ammonium nitrate (UAN) injection and summer UAN fertigations. The experiments were located on silty clay loam soils under no-till irrigated continuous corn of eastern Nebraska. Three approaches were used. First, near-continuous N 2O flux measurements were made in non-wheel-tracked (NWT) interrows in four 24-h periods during the growing season of 2002. Second, point measurements of N 2O flux were made in the wheel-tracked (WT) and NWT interrows at five dates during the growing season of 2002. Third, point measurements of N 2O fluxes and soils (nitrate, ammonium, moisture, and temperature) were made in the NWT interrows from 2001 to 2004. The differences between point vs. continuous flux measurements (<8 g N 2O-N ha -1 d -1) and between the WT vs. the NWT (<3.7 g N 2O-N ha -1 d -1) were not significant. The means of N 2O daily flux within 60 d after injection (period of high soil N) in the first, second, and third year were 26.8, 21.2, and 28.0 g N 2O-N ha -1 d -1, respectively. The means during low soil N were 9.24, 4.05, and 7.50 g N 2O-N ha -1 d -1, respectively. Summer fertigations did not increase N 2O flux. Under the conditions of this study, optimal point measurement for N 2O daily flux can be made any time during the day at the NWT interrows. Among the soil parameters, soil nitrate dynamics in the injection zone correlates best with N 2O fluxes.
  • Authors:
    • Paustian, K.
    • Breidt, F. J.
    • Ogle, S. M.
  • Source: Biogeochemistry
  • Volume: 72
  • Issue: 1
  • Year: 2005
  • Summary: We conducted a meta-analysis to quantify the impact of changing agricultural land use and management on soil organic carbon (SOC) storage under moist and dry climatic conditions of temperate and tropical regions. We derived estimates of management impacts for a carbon accounting approach developed by the Intergovernmental Panel on Climate Change, addressing the impact of long-term cultivation, setting-aside land from crop production, changing tillage management, and modifying C input to the soil by varying cropping practices. We found 126 articles that met our criteria and analyzed the data in linear mixed-effect models. In general, management impacts were sensitive to climate in the following order from largest to smallest changes in SOC: tropical moist>tropical dry>temperate moist>temperate dry. For example, long-term cultivation caused the greatest loss of SOC in tropical moist climates, with cultivated soils having 0.58 ± 0.12, or 58% of the amount found under native vegetation, followed by tropical dry climates with 0.69 ± 0.13, temperate moist with 0.71 ± 0.04, and temperate dry with 0.82 ± 0.04. Similarly, converting from conventional tillage to no-till increased SOC storage over 20 years by a factor of 1.23 ± 0.05 in tropical moist climates, which is a 23% increase in SOC, while the corresponding change in tropical dry climates was 1.17 ± 0.05, temperate moist was 1.16 ± 0.02, and temperate dry was 1.10 ± 0.03. These results demonstrate that agricultural management impacts on SOC storage will vary depending on climatic conditions that influence the plant and soil processes driving soil organic matter dynamics.