• Authors:
    • Lenssen, A.
    • Caesar-Thonthat, T.
    • Waddell, J.
    • Sainju, U. M.
  • Source: Journal of Environmental Quality
  • Volume: 35
  • Issue: 4
  • Year: 2006
  • Summary: Long-term use of conventional tillage and wheat (Triticum aestivum L.)-fallow systems in the northern Great Plains have resulted in low soil organic carbon (SOC) levels. We examined the effects of two tillage practices [conventional till (CT) and no-till (NT)], five crop rotations [continuous spring wheat (CW), spring wheat-fallow (W-F), spring wheat-lentil (Lens culinaris Medic.) (W-L), spring wheat-spring wheat-fallow (W-W-F), and spring wheat-pea (Pisum sativum L.)-fallow (W-P-F)], and Conservation Reserve Program (CRP) planting on plant C input, SOC, and particulate organic carbon (POC). A field experiment was conducted in a mixture of Scobey clay loam (fine-loamy, mixed, Aridic Argiborolls) and Kevin clay loam (fine, montmorillonitic, Aridic Argiborolls) from 1998 to 2003 in Havre, MT. Total plant biomass returned to the soil from 1998 to 2003 was greater in CW (15.5 Mg ha(-1)) than in other rotations. Residue cover, amount, and C content in 2004 were 33 to 86% greater in NT than in CT and greater in CRP than in crop rotations. Residue amount (2.47 Mg ha(-1)) and C content (0.96 Mg ha(-1)) were greater in NT with CW than in other treatments, except in CT with CRP and W-F and in NT with CRP and W-W-E The SOC at the 0- to 5-cm depth was 23% greater in NT (6.4 Mg ha(-1)) than in CT. The POC was not influenced by tillage and crop rotation, but POC to SOC ratio at the 0- to 20-cm depth was greater in NT with W-L (369 g kg(-1) SOC) than in CT with CW, W-F, and W-L. From 1998 to 2003, SOC at the 0- to 20-cm depth decreased by 4% in CT but increased by 3% in NT. Carbon can be sequestered in dryland soils and plant residue in areas previously under CRP using reduced tillage and increased cropping intensity, such as NT with CW, compared with traditional practice, such as CT with W-F system, and the content can be similar to that in CRP planting.
  • Authors:
    • Hergert, G. W.
    • Tarkalson, D. D.
    • Cassman, K. G.
  • Source: Agronomy Journal
  • Volume: 98
  • Issue: 1
  • Year: 2006
  • Summary: Tillage systems and nutrient management influence soil chemical properties that can impact the long-term sustainability of dryland production systems. This study was conducted to compare the effects of no-till (NT) and conventional till (CT) on the soil chemical properties and grain yield of a dryland winter wheat ( Triticum aestivum L.)-grain sorghum [ Sorghum bicolor (L.) Moench]/corn ( Zea mays L.)-fallow rotation. The effects of tillage practice over a 27-yr period (1962-1989) and the effect of the conversion of CT to NT over a 14-yr period (1989-2003) on selected soil chemical properties [pH, cation exchange capacity (CEC), base saturation (BS), soil organic C (SOC), K, Ca, Mg, and Bray-P] at different soil depths was determined. The acidification rate of the NT treatment from 1962 to 2003 was also determined. The study was conducted at North Platte, NE on a Holdrege silt loam (fine-silty, mixed, mesic Typic Argiustolls). In 1989, there were differences in soil chemical properties between CT and NT at some depths after 27 yr. However, in 2003, 14 yr after converting from CT to NT, there were no differences in the soil chemical properties compared with continuous NT. In 1989 and 2003, the soil chemical properties varied with soil depth. The acidification rate from 1962 to 2003 for the NT treatment in the 0- to 15-cm depth was 1.3 kmol H + ha -1 yr -1. This rate of acidification represents 38% of the total potential acidity from N fertilizer applications over 41 yr. Acidification was attributed to nitrification of ammonium-based fertilizers and leaching of NO 3-. Long-term winter wheat (1966-1983) and grain sorghum (1964-1988) grain yields were higher for NT (2718 and 4125 kg ha -1) than CT (2421 and 3062 kg ha -1). Retention of soil moisture as a result of increased residue cover under NT likely contributed to higher NT yields. Soil chemical properties in the wheat-sorghum/corn-fallow rotation will likely continue to change as a result of current management practices. Lime additions may become necessary in the future to ensure the sustainability of crop production in this system.
  • Authors:
    • Cassman, K. G.
    • Hergert, G. W.
    • Payero, J. O.
    • Tarkalson, D. D.
  • Source: Plant and Soil
  • Volume: 283
  • Issue: 1-2
  • Year: 2006
  • Summary: Soil pH is decreasing in many soils in the semiarid Great Plains of the United States under dry land no-till (NT) cropping systems. This study was conducted to determine the rate of acidification and the causes of the acidification of a soil cropped to a winter wheat (Triticum aestivum L.)-grain sorghum [Sorghum bicolor (L.) Moench]/corn (Zea mays L.)-fallow rotation (W-S/C-F) under NT. The study was conducted from 1989 to 2003 on soil with a long-term history of either continuous NT management [NT(LT)] (1962-2003) or conventional tillage (CT) (1962-1988) then converted to NT [NT(C)] (1989-2003). Nitrogen was applied as ammonium nitrate (AN) at a rate of 23 kg N ha(-1)supercript stop in 1989 and as urea ammonium nitrate (UAN) at an average annual rate of 50 kg N ha(-1) from 1990 to 2003 for both NT treatments. Soil samples were collected at depth increments of 0-5, 5-10, 10-15, and 15-30 cm in the spring of 1989 and 2003. Acidification rates for the NT(LT) and NT(C) treatments were 1.13 and 1.48 kmol H+ ha(-1) yr(-1) in the 0-30 cm depth, respectively. The amount of CaCO3 needed to neutralize the acidification is 57 and 74 kg ha(-1) yr(-1) for the NT(LT) and NT(C) treatments, respectively. A proton budget estimated by the Helyar and Porter [1989, Soil Acidity and Plant Growth, Academic Press] method indicated that NO3- leaching from the 30 cm depth was a primary cause of long-term acidification in this soil. Nitrate leaching accounted for 59 and 66% of the H+ from the acid causing factors for NT(LT) and NT(C) treatments, respectively. The addition of crop residues to the soil neutralized 62 and 47% of the acidity produced from the leaching of NO3-, and 37 and 31% of the acid resulting from NO3- leaching and the other acid-causing constituents for the NT(LT) and NT(C) treatments, respectively. These results document that surface soils in dry land W-S/C-F rotations under NT are acidifying under current management practices. Improved management to increase nitrogen uptake efficiency from applied fertilizer would help reduce the rate of acidification. The addition of lime materials to prevent negative impacts on grain yields may be necessary in the future under current management practices.
  • Authors:
    • Varvel, G.
  • Source: Soil Science Society of America Journal
  • Volume: 70
  • Issue: 2
  • Year: 2006
  • Summary: Sequestration and storage of carbon (C) by agricultural soils has been cited as one potential part of the solution to soil degradation and global climate change. However, C sequestration in soils is a slow and dynamic process. This study was conducted to evaluate the effects of crop rotation and N fertilizer management on soil organic C (SOC) levels at several points in time during 18 years of a long-term study in the Western Corn Belt (Nebraska, USA). Seven cropping systems (three monoculture, two 2-year, and two 4-year rotations) with three levels of N fertilizer were compared. The monocultures included continuous maize ( Zea mays), soyabean ( Glycine max) and grain sorghum ( Sorghum bicolor). The 2-year rotations were maize/soyabean and grain sorghum/soyabean, and the two 4-year rotations were oat ( Avena sativa) + clover (80% Melilotus officinalis and 20% Trifolium pratense/grain sorghum/soyabean/maize and soyabean/grain sorghum/oat + clover/maize). Soil samples were taken in the spring in 1984, 1992, 1998, and 2002 to a depth of 30 cm in 0- to 7.5-, 7.5- to 15-, and 15- to 30-cm increments. No differences were obtained in SOC levels in 1984 at the beginning of the study. After 8 years, rotation significantly increased SOC 449 kg ha -1 across all cropping systems. From 1992 to 2002, SOC levels in the 0- to 7.5-cm depth decreased by 516 kg ha -1 across all cropping systems. Soil organic C levels in the 7.5- to 15-cm depths in 1992 and 2002 demonstrated similar rotation effects to those in the surface 0- to 7.5-cm, being not significantly affected from 1984 to 1992 but being significantly decreased from 1992 to 2002 (568 kg SOC ha -1 across all cropping systems). Many of the SOC gains in the surface 30 cm measured during the first 8 years of the study were lost during the next 10 years in all but the 4-year cropping systems after 18 years. The loss of SOC in this latter period occurred when depth of tillage was increased by using a tandem disc with larger-diameter discs. These results demonstrate that more than one point-in-time measurement from long-term experiments is necessary to monitor SOC changes when several management variables, such as cropping system and N fertilizer, are being used. They also indicate that apparent small changes in cultural practices, such as in depth of tillage in this experiment, can significantly change SOC dynamics in the soil. Subtle changes in cultural practices (e.g., tillage depth) can have significant long-term results, but long-term experiments are required to quantify their impact under variable climatic conditions.
  • Authors:
    • McVay, K.
    • Langemeier, M.
    • Regehr, D.
    • Devlin, D.
    • Mankin, K.
    • Pierzynski, G.
    • Sweeney, D.
    • Janssen, K.
    • Zeimen, M.
  • Source: Journal of Soil and Water Conservation
  • Volume: 61
  • Issue: 5
  • Year: 2006
  • Summary: Best management practices have been recommended for controlling nutrient, herbicide, or sediment losses with surface runoff. This study was designed to determine the best overall combination of tillage and application practices to reduce surface losses from cropland. Runoff was collected from two Kansas sites in sorghum-soybean rotation during the 2001 to 2004 crop years and analysed for bioavailable phosphorus (P), soluble P, total P, ammonium, nitrate, total nitrogen (N), sediment, atrazine, and metolachlor concentrations. No-till treatments consistently experienced higher runoff water volumes than the chisel/disk tillage system used to warm and dry these clay soils in the spring. For this reason the no-till treatments also had higher nutrient and herbicide losses than chisel/disk tillage regardless of use of high or low application management techniques. The high included fertilizer and herbicide application practices intended to reduce losses with runoff while the standard application broadcast applied fertilizer and herbicide at planting. Few consistent differences were seen for pollutant loss between the high and standard application management. When average losses for all eight location-years were compared to chisel/disk low, soluble P losses were 3.0 and 2.1 times higher for no-till low and no-till high, respectively; metolachlor losses were 2.4 and 2.7 times higher for no-till low and no-till high, respectively; and atrazine losses were 4.8 and 6.1 times higher for no-till low and no-till high, respectively. The chisel/disk low did experience two times higher sediment losses compared with the no-till low or no-till high, when averaging over all eight location-years. However, tolerable soil loss was not exceeded, chisel/disk low generally had small losses for all tested pollutants and may be the best management combination to simultaneously reduce nutrient, herbicide, and sediment losses with cropland runoff for sites like those used in this study.
  • Authors:
    • Pitts, T.
    • Atwood, J. D.
    • Williams, J. R.
    • Potter, S. R.
    • Wang, X.
  • Source: Transactions of the ASABE
  • Volume: 49
  • Issue: 3
  • Year: 2006
  • Summary: Sensitivity analysis for mathematical simulation models is helpful in identifying influential parameters for model outputs. Representative sets of APEX (Agricultural Policy/Environmental eXtender) model data from across the U.S. were used for sensitivity analysis to identify influential parameters for APEX outputs of crop grain yields, runoff/water yield, water and wind erosion, nutrient loss, and soil carbon change for a national assessment project: the Conservation Effects Assessment Project (CEAP). The analysis was based on global sensitivity analysis techniques. A test case, randomly selected from the representative sets of APEX model data, was first analyzed using both the variance-based sensitivity analysis technique and the enhanced Morris method. The analysis confirmed the reliability of the enhanced Morris measure in screening subsets of influential and non-influential parameters. Therefore, the enhanced Morris method was used for the national assessment, where the cost of applying variance-based techniques would be excessive. Although sensitivities are dynamic in both temporal and spatial dimensions, the very influential parameters (ranking 1st and 2nd) appear very influential in most cases. Statistical analyses identified that the NRCS curve number index coefficient is very influential for runoff and water-related output variables, such as soil loss by water, N and P losses in runoff. The Hargreaves PET equation exponent, moisture fraction required for seed germination, RUSLE C factor coefficient, and the potential heat units are influential for more than two APEX outputs studied.
  • Authors:
    • Wielopolski, L.
  • Year: 2006
  • Summary: The Department of Energy (DOE) operates Brookhaven National Laboratory (BNL) with its many unique research facilities and programs. One of the DOE’s major strategic missions is the Terrestrial Carbon Processes Program that studies the global production and transport of anthropogenic CO2 and its effects on climate and health. BNL’s Environmental Sciences Department responds to this mission and the research of Wielopoloski’s group in the Environmental Research and Technology Division are closely tied to this goal. Through new instrumentation, focused measurements, and modeling, they aim to determine the in situ carbon content of soils, locally and over large tracts of land. This research, though still in its early stages, is very promising, offering levels of precision not previously attainable, along with speed and lower costs. This meeting will bring together experts in instrumentation and field measurements from other DOE laboratories, universities, and the United States Department of Agriculture to evaluate and explore the novel methodologies and to assess their advantages over conventional methods.
  • Authors:
    • Grace, P. R.
    • Colunga-Garcia, M.
    • Gage, S.
    • Safir, G.
    • Robertson, G. P.
  • Source: Ecosystems
  • Volume: 9
  • Issue: 5
  • Year: 2006
  • Summary: Soil organic carbon (SOC) represents a significant pool of carbon within the biosphere. Climatic shifts in temperature and precipitation have a major influence on the decomposition and amount of SOC stored within an ecosystem. We have linked net primary production algorithms, which include the impact of enhanced atmospheric CO2 on plant growth, to the Soil Organic Carbon Resources And Transformations in EcoSystems (SOCRATES) model to develop a SOC map for the North Central Region of the United States between the years 1850 and 2100 in response to agricultural activity and climate conditions generated by the CSIRO Mk2 Global Circulation Model (GCM) and based on the Intergovernmental Panel for Climate Change (IPCC) IS92a emission scenario. We estimate that the current day (1990) stocks of SOC in the top 10 cm of the North Central Region to be 4692 Mt, and 8090 Mt in the top 20 cm of soil. This is 19% lower than the pre-settlement steady state value predicted by the SOCRATES model. By the year 2100, with temperature and precipitation increasing across the North Central Region by an average of 3.9 C and 8.1 cm, respectively, SOCRATES predicts SOC stores of the North Central Region to decline by 11.5 and 2% (in relation to 1990 values) for conventional and conservation tillage scenarios, respectively.
  • Authors:
    • Cantero-Martinez, C.
    • Westfall, D. G.
    • Sherrod, L. A.
    • Peterson, G. A.
  • Source: Journal of Soil and Water Conservation
  • Volume: 61
  • Issue: 2
  • Year: 2006
  • Summary: The presence of crop residue is an important component of dryland cropping systems management in the semiarid environment where soil erosion by wind is a major soil degradation process. Residue also affects precipitation capture and runoff. Long-term residue quantity dynamics of different cropping systems has not been studied in the semi-arid environment of the western Great Plains. Long-term studies were conducted in eastern Colorado, USA to determine the interaction of no-till cropping systems, soils, and climatic gradient on the production, retention, and disappearance of crop residue over a 12-year period. The cropping systems evaluated were winter wheat ( Triticum aestivum)-summer fallow (WF), winter wheat-maize ( Zea mays) or sorghum ( Sorghum bicolor)-summer fallow (WC/SF), winter wheat-maize/sorghum-millet ( Panicum miliaceum)-summer fallow (WC/SMF), and continuous cropping (CC). A soil surface residue base was achieved in a few years (four to five) and changed little over time. However, as cropping intensity increased the total crop residue retained on the soil surface increased as the proportion of fallow time decreased; a general trend was for residue levels to increase slowly. However, in the winter wheat-summer fallow system residue levels showed a trend to decrease after the initial base was achieved. Greater residue production and retention occurred on the toeslope soil position because these soils are deeper, have greater water holding capacity, and receive run-on water from upslope positions. Residue disappearance was less in the fallow period before maize planting compared to before wheat planting due to the greater fallow period, which included summer fallow in the wheat system. Residue loss was greater during the crop production periods as compared to the fallow periods. The levels of residue present on the soil surface in our intensive no-till cropping systems were generally adequate to control erosion by wind. However, at our high potential evapotranspiration site the residue levels were "marginal" for adequate wind erosion abatement, particularly in the winter wheat-summer fallow system. A combination of no-till management and increased cropping intensity (greater than winter wheat-summer fallow) is the key to sustainable production and soil conservation in this semi-arid environment.
  • Authors:
    • Halvorson, A. D.
    • Reule, C. A.
  • Source: Agronomy Journal
  • Volume: 98
  • Issue: 5
  • Year: 2006
  • Summary: Irrigated, no-till (NT) production systems can potentially reduce soil erosion, fossil fuel consumption, and greenhouse gas emissions compared with conventional till (CT) systems. Including a legume in the rotation may also reduce N fertilizer requirements. Nitrogen fertilization (6 N rates) effects on irrigated, corn (Zea mays L.) and soybean [Glycine mar (L.) Merr.] yields in a corn-soybean rotation were evaluated for 5 yr on a clay loam soil to determine the viability of an irrigated NT system and N needs for optimum crop yield. Corn grain yields were significantly increased by N fertilization each of 3 yr in the rotation, but soybean grain yields (2 yr) did not respond to N fertilization, averaging 2.79 Mg ha(-1). Three year average corn grain yields were near maximum with an available N (AN) (soil + fertilizer + irrigation water N) level of 257 kg N ha(-1). Nitrogen use efficiency (NUE) by corn and soybean, based on grain N removal, decreased with increasing AN level and ranged from 155 to 46 and 88 to 18 kg grain kg(-1) AN for the low and high N treatments for corn and soybean, respectively. Estimated total N required to produce one Mg grain at maximum yield averaged 20 kg N for corn and 54 kg N for soybean. Corn residue increased with increasing N rate, but soybean residue was constant across N rates. Excellent irrigated, NT corn yields were obtained in this corn-soybean rotation for northern Colorado, but soybean yields were only marginally acceptable. Short soybean plant height (30-40 cm) and shattering made combine harvest difficult resulting in significant grain loss. Improved soybean cultivars are needed for this area to make a corn-soybean rotation a viable production system.