• Authors:
    • Stahlman, P. W.
    • Benjamin, J. G.
    • Mikha, M. M.
    • Geier, P. W.
  • Source: Agronomy Journal
  • Volume: 106
  • Issue: 1
  • Year: 2014
  • Summary: Nutrient dynamics in the calcareous eroded soils of the western United States may react differently than the acid soils in the eastern United States. The objectives of this study were to evaluate the impact of tillage practices and N treatments on changes in soil nutrient constituents. The eroded study was initiated in 2006 at the Agriculture Research Center, Hays, KS, on an Armo silt loam (fine-loamy, mixed, mesic Entic Haplustolls). Tillage practices were no-tillage (NT) and conventional tillage (CT). Beef manure (M) and urea, as commercial fertilizer (F) at low (L) and high (H) rates were applied as N sources. The control (C) treatment, with no N added, was included under both tillage practices. Annually (2006-2011) spring soil samples were taken at 0- to 15-cm and 15- to 30-cm depths. Soil chemical properties were influenced by N treatments and sampling depths, but not by tillage. Soil acidity (pH) was reduced in 2011 compared with 2006. Relative to control, more reduction in soil pH was observed with HM (21%) compared with HF treatment. Soil EC with HM and HF was approximately 2.2 times greater than LM and LF. Soil extractable P with HM substantially increased, 45.9 mg kg -1, compared with LM, 18.3 mg kg -1, at the surface 0 to 15 cm. The change in soil organic carbon (DeltaSOC) associated with M was 36-fold higher than F treatments. In general, the use of M as N source improved soil nutrient dynamics in this eroded site compared with F.
  • Authors:
    • Benjamin, J. G.
    • Stahlman, P. W.
    • Mikha, M. M.
    • Geier, P. W.
  • Source: Agronomy Journal
  • Volume: 106
  • Issue: 1
  • Year: 2014
  • Summary: The response of manure applications on calcareous eroded soils in the western United States is unlike the responses observed on acid soils in the eastern United States. The objectives of this study were to restore the productivity and evaluate N loss of eroded land influenced by tillage practices, N sources, and N rates. The study was initiated in 2006 on an Armo silt loam (fine-loamy, mixed, mesic Entic Haplustolls) at the Agriculture Research Center, Hays, KS. Tillage practices were no-tillage (NT) and conventional tillage (CT). Nitrogen sources were beef manure (M); urea, as commercial fertilizer (F); and no-N control (C) at two rates, low (L) and high (H). The crop rotation was grain sorghum ( Sorghum bicolor L.), forage oat ( Avena sativa L.), winter wheat ( Triticum aestivum L.), grain sorghum, proso millet ( Panicum miliaceum L.), and winter wheat. Grain yield (2006-2011) and soil inorganic nitrogen (SIN) at 0- to 120-cm depth were evaluated. Grain yields were not influenced by tillage practices, except in 2006 when NT had greater yields than CT. Manure addition increased grain yields compared with F and C treatments. Excess amounts of N and low productivity lead to leaching of the SIN down the soil profile with HF and HM. The LM exhibited less productivity and less SIN loss than HM treatment. Overall, M could be the N source that can improve the productivity of the eroded site. The benefits of increasing the productivity and the risk of N loss with HM need to be further addressed.
  • Authors:
    • Paustian, K.
    • Tubiello, F.
    • Rosenstock, T.
    • Wollenberg, L.
    • Olander, L.
    • Ogle, S. M.
    • Buendia, L.
    • Nihart, A.
    • Smith, P.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 1
  • Year: 2014
  • Summary: Agriculture in developing countries has attracted increasing attention in international negotiations within the United Nations Framework Convention on Climate Change for both adaptation to climate change and greenhouse gas mitigation. However, there is limited understanding about potential complementarity between management practices that promote adaptation and mitigation, and limited basis to account for greenhouse gas emission reductions in this sector. The good news is that the global research community could provide the support needed to address these issues through further research linking adaptation and mitigation. In addition, a small shift in strategy by the Intergovernmental Panel on Climate Change (IPCC) and ongoing assistance from agricultural organizations could produce a framework to move the research and development from concept to reality. In turn, significant progress is possible in the near term providing the basis for UNFCCC negotiations to move beyond discussion to action for the agricultural sector in developing countries.
  • Authors:
    • Briggs, R. D.
    • Volk, T. A.
    • Pacaldo, R. S.
  • Source: Bio-energy Research
  • Volume: 7
  • Issue: 3
  • Year: 2014
  • Summary: Previous greenhouse gas (GHG) assessments for the shrub willow biomass crops (SWBC) production system lacked quantitative data on the soil CO 2 efflux (F c). This study quantifies the mean annual cumulative F c, the C sequestration in the above- and belowground biomass, and the carbon balance of the production system. We utilized four SWBC fields, which have been in production for 5, 12, 14, and 19 years. Two treatments were applied: continuous production (CP) - shrub willows were harvested, and stools were allowed to regrow, and tear-out (TO) (crop removal) - shrub willows were harvested, and stools were sprayed with herbicide following spring, crushed, and mixed into the soil. Mean annual cumulative F c were measured using dynamic closed chambers (LI-8100A and LI-8150). Across different age classes, the mean cumulative F c ranged from 27.2 to 35.5 Mg CO 2 ha -1 year -1 for CP and 26.5 to 29.3 Mg CO 2 ha -1 year -1 for TO. The combined carbon (C) sequestration of the standing above- and belowground biomass, excluding stems, ranged from 50.6 to 94.8 Mg CO 2 eqv. ha -1. In the CP treatment, the annual C sequestration in the fine roots and foliage offsets the annual cumulative F c. Across different age classes, C balances ranged from -21.5 to -59.3 Mg CO 2 ha -1 for CP and 26.5 to 29.3 Mg CO 2 ha -1 for TO. The GHG potential of SWBC is about -36.3 Mg CO 2 eqv. ha -1 at the end of 19 years, suggesting that the SWBC system sequesters C until termination of the crop.
  • Authors:
    • Hatfield, J. L.
    • Parkin, T. B.
  • Source: Agronomy Journal
  • Volume: 106
  • Issue: 2
  • Year: 2014
  • Summary: Fertilizer application in crop production agriculture is a major factor influencing soil emissions of the greenhouse gas N 2O. Enhanced efficiency fertilizers (EEFs) have the potential to decrease N 2O emissions by improving the synchrony between soil N supply and crop N demand. This study was conducted to compare the effects of N 2O emissions from soil cropped to corn ( Zea mays L.) and EEFs and conventional fertilizers. During a 3-yr period, growing-season N 2O emissions were quantified in unfertilized check plots and plots fertilized with urea-NH 4NO 3 (UAN), UAN containing the urease and nitrification stabilizer AgrotainPlus (UAN+Ag), a stabilized urea containing urease and nitrification inhibitors (SuperU), and a controlled-release polymer-coated urea (ESN). In the third year of the study, conventional urea and an additional fertilizer formulation, Nutrisphere, were evaluated. We observed no reductions in cumulative seasonal N 2O emissions from treatments fertilized with the EEFs in any of the study years. Generally, N 2O emissions were significantly higher than emissions from the check (no fertilizer) treatment. There were no differences among fertilizer types except in 2009 when the ESN treatment had significantly higher emissions than the check, UAN, and UAN+Ag treatments. Our results indicate that, due to the episodic nature of N 2O emissions induced by rainfall events, reduction of N 2O emissions through the use of EEFs may be limited in rainfed regions.
  • Authors:
    • Meisinger, J. J.
    • Pote, D. H.
  • Source: Journal of Soil and Water Conservation
  • Volume: 69
  • Issue: 1
  • Year: 2014
  • Summary: Ammonia (NH3) volatilization from agricultural fields is important economically as a direct loss of the valuable crop nutrient nitrogen (N), but it can also be a significant environmental concern for soil, air, and water quality of nearby ecosystems. As poultry production has expanded in cropland areas of the southeastern United States, poultry litter has become a major source of crop nutrients for farmers using conservation tillage systems. However, the conventional application method of broadcasting poultry litter on the soil surface can allow as much as 60% of the applied litter N to volatilize as NH3. To provide management options that can prevent NH3 losses and help farmers use poultry litter nutrients more efficiently, a research team at USDA's Agricultural Research Service developed a prototype tractor-drawn implement for subsurface application of dry poultry litter in perennial pasture and conservation tillage systems. When compared to surface broadcasting, previous research showed that subsurface application of poultry litter decreased odor problems, increased crop yields, prevented more than 90% of nutrient losses in runoff, and prevented NH3 volatilization from perennial pasture systems. The current study was conducted to expand our knowledge regarding the effect of this litter application method on NH3 volatilization from row-crop conservation tillage systems. For two consecutive summers, field plots with a uniform high-residue surface cover of chopped wheat straw received about 5,000 kg ha(-1) (4,500 lb ac(-1)) of poultry litter applied by surface spreading with no incorporation, surface spreading followed by light disking, or subsurface banding using the prototype USDA ARS applicator. Small mobile wind tunnels monitored NH3 volatilization for at least five days after each litter treatment. Results for both years showed that NH3 losses were consistently affected by diurnal variations that were closely related to the vapor pressure deficit. Compared to conventional surface spreading of poultry litter, NH3 volatilization decreased an average of 67% when the litter application was followed by light disking, and decreased an average of 88% when the litter was applied below the soil surface using the prototype applicator. These data show that subsurface injection of dry poultry litter can preserve adequate surface cover for conservation needs while constraining NH3 losses to minimal levels, thus conserving N for row crops and reducing potential nitrogen losses to the environment.
  • Authors:
    • Morton, L. W.
    • McCann, L.
    • Lynne, G.
    • Jackson-Smith, D.
    • Genskow, K.
    • Arbuckle, J. G.
    • Prokopy, L. S.
    • Thompson, A.
    • Reimer, A.
    • Nowak, P.
  • Source: Journal of Soil and Water Conservation
  • Volume: 69
  • Issue: 2
  • Year: 2014
  • Authors:
    • Sainju, U. M.
  • Source: Agronomy Journal
  • Volume: 106
  • Issue: 4
  • Year: 2014
  • Summary: To determine farm C credit and reduce global warming potential, information is needed on the effect of management practices on soil C storage. The effects of tillage, cropping sequence, and N fertilization were evaluated on dryland crop biomass, surface residue C, and soil organic carbon (SOC) at the 0- to 120-cm depth in a Williams loam (fine-loamy, mixed, superactive, frigid, Typic Argiustolls) and their relationships with grain yields from 2006 to 2011 in eastern Montana. Treatments were no-till continuous malt barley ( Hordeum vulgare L.) (NTCB), no-till malt barley-pea ( Pisum sativum L.) (NTB-P), no-till malt barley-fallow (NTB-F), and conventional till malt barley-fallow (CTB-F), each with 0, 40, 80, and 120 kg N ha -1. Annualized crop grain and biomass yields, surface residue amount, and C contents were greater in NTB-P and NTCB than CTB-F and NTB-F and increased with increased N rates. At 0 to 5 and 5 to 10 cm, SOC was greater in NTB-P than CTB-F or NTCB with 40 kg N ha -1 and at 10 to 30 and 0 to 120 cm was greater in NTB-P than NTCB with 120 kg N ha -1. Surface residue C and SOC were related with grain yield and C content ( R2=0.21-0.55, P≤0.10, n=16). Greater amount of crop residue returned to the soil and turnover rate probably increased surface residue C, soil C storage, and crop yields in NTB-P with 40 and 120 kg N ha -1 than the other treatments. Soil organic matter and crop yields can be enhanced by using NTB-P with 40 kg N ha -1.
  • Authors:
    • Hatfield, P. G.
    • Lenssen, A. W.
    • Barsotti, J. L.
    • Sainju, U. M.
  • Source: Nutrient Cycling in Ecosystems
  • Volume: 99
  • Issue: 1-3
  • Year: 2014
  • Summary: Sheep (Ovis aries L.) grazing, a cost-effective method of weed control compared to herbicide application and tillage, may influence N cycling by consuming crop residue and weeds and returning N through feces and urine to the soil. The objective of this experiment was to evaluate the effect of sheep grazing compared to tillage and herbicide application for weed control on soil particulate and active soil N fractions in dryland cropping systems. Our hypothesis was that sheep grazing used for weed control would increase particulate and active soil N fractions compared to tillage and herbicide application. Soil samples collected at the 0-30 cm depth from a Blackmore silt loam were analyzed for particulate organic N (PON), microbial biomass N (MBN), and potential N mineralization (PNM) under dryland cropping systems from 2009 to 2011 in southwestern Montana, USA. Treatments were three weed management practices [sheep grazing (grazing), herbicide application (chemical), and tillage (mechanical)] as the main plot and two cropping sequences [continuous spring wheat (Triticum aestivum L.; CSW) and spring wheat-pea (Pisum sativum L.)/barley (Hordeum vulgare L.) mixture hay-fallow; W-P/B-F] as the split-plot factor arranged in randomized complete block with three replications. The PON and MBN at 0-30 cm were greater in the chemical or mechanical than the grazing treatment with CSW. The PNM at 15-30 cm was greater in the chemical or mechanical than the grazing treatment in 2009 and 2011 and at 5-15 cm was greater with W-P/B-F than CSW in 2010. From 2009 to 2011, PON at 0-30 cm and PNM at 15-30 cm reduced from 2 to 580 kg N ha(-1) year(-1) in the grazing and chemical treatments, but the rate varied from -400 to 2 kg N ha(-1) year(-1) in the mechanical treatment. Lower amount of labile than nonlabile organic matter returned to the soil through feces and urine probably reduced soil active and coarse organic matter N fractions with sheep grazing compared to herbicide application and tillage for weed control. Reduction in the rate of decline in N fractions from 2009 to 2011 compared to the herbicide application treatment, however, suggests that sheep grazing may stabilize N fractions in the long-term if the intensity of grazing is reduced. Animal grazing may reduce soil N fractions in annual cropping systems in contrast to known increased fractions in perennial cropping systems.
  • Authors:
    • Webber, M. E.
    • Sanders, K. T.
  • Source: Environmental Research Letters
  • Volume: 9
  • Issue: 4
  • Year: 2014
  • Summary: The US food system utilizes large quantities of liquid fuels, electricity, and chemicals yielding significant greenhouse gas (GHG) emissions that are not considered in current retail prices, especially when the contribution of biogenic emissions is considered. However, because GHG emissions might be assigned a price in prospective climate policy frameworks, it would be useful to know the extent to which those policies would increase the incremental production costs to food within the US food system. This analysis uses lifecycle assessment (LCA) to (1) estimate the magnitude of carbon dioxide equivalent (CO 2e) emissions from typical US food production practices, using wheat and beef as examples, and (2) quantify the cost of those emissions in the context of a GHG-pricing regime over a range of policy constructs. Wheat and beef were chosen as benchmark staples to provide a representative range of less intensive and more intensive agricultural goods, respectively. Results suggest that 1.10.13 and 318.1 kg of lifecycle CO 2e emissions are embedded in 1 kg of wheat and beef production, respectively. Consequently, the cost of lifecycle CO 2e emissions for wheat (i.e. cultivation, processing, transportation, storage, and end-use preparation) over an emissions price range of $10 and $85 per tonne CO 2e is estimated to be between $0.01 and $0.09 per kg of wheat, respectively, which would increase total wheat production costs by approximately 0.3-2% per kg. By comparison, the estimated lifecycle CO 2e price of beef over the same range of CO 2e prices is between $0.31 and $2.60 per kg of beef, representing a total production cost increase of approximately 5-40% per kg based on average 2010 food prices. This range indicates that the incremental cost to total US food production might be anywhere between $0.63-5.4 Billion per year for grain and $3.70 and $32 Billion per year for beef based on CO 2e emissions assuming that total production volumes stay the same.