• Authors:
    • Whitney, D.
    • Thompson, C.
  • Source: Journal of Production Agriculture
  • Volume: 11
  • Issue: 3
  • Year: 1998
  • Summary: Tillage and N management are important in dryland crop production of the west central Great Plains (area between the 99(th) meridian and the eastern edge of the Rocky Mountains) because of frequent periods of limited soil moisture. Therefore, judicious use of N fertilizer is a management priority in wheat (Triticum aestivum L,)-sorghum [Sorghum biocolor (L,) Moench]- fallow (W-S-F) rotations. The objectives of this study were to: (i) determine the long-term effects of N fertilization (0, 20, 40, and 60 lb N/acre) on grain yields of winter wheat and grain sorghum under three tillage systems, (ii) investigate the effect of soil moisture at or near planting on grain yields, and (iii) evaluate the residual profile soil inorganic N after 20 yr of N fertilization in the three tillage systems. The study involved a W-S-F rotation under three tillage systems on a nearly level Harney silt loam soil (fine, montmorillonite, mesic Typic Argiustoll), The three tillage systems were clean-till (CT), reduced-till (RT), and no-till (NT), Nitrogen was broadcast preplant as ammonium nitrate on each crop at rates of 0, 20, 40, and 60 Ib N/acre, As the level of soil moisture increased in each tillage system, there was a corresponding larger yield increase of wheat and sorghum to applied N, The correlation of grain yields of wheat and sorghum with soil profile N at all depths was highest for nitrate N and lowest for ammonium and total inorganic N. For all three tillage systems, sampling deeper than 6 in, resulted in little improvement in the coefficient of determination (R-2) for grain yields regressed on soil nitrate N, Residual soil nitrate N was highest in the top 6 in., dropped significantly in the 6- to 12-in. depth, and remained relatively low thereafter throughout the 72-in. sampling depth. Data from this long-term study showed the optimum broadcast N rate was approximately 60 Ib N/acre applied on each crop grown in a W-S-F rotation with the exact rate depending on soil moisture, fertilizer, and crop prices, Yields from CT were comparable with RT on this nearly level upland soil but failed to meet the residue requirements mandated in conservation compliance plans, Poorer stands, increased weed competition, and drier soils resulted in generally lower yields from NT plots. Considering all factors, RT systems for dryland wheat and sorghum production are recommended on upland fertile soils in the west central Great Plains.
  • Authors:
    • Bowman, R. A.
    • Halvorson, A. D.
  • Source: Soil Science
  • Volume: 163
  • Issue: 3
  • Year: 1998
  • Summary: Intensively cropped dryland systems in the central Great Plains require adequate N fertilization for optimum residue and grain production. However, this N fertilization could be slowly changing the chemistry of the surface soil because of a decrease in soil pH and an increase in soil organic matter (SOM) and basic cations, even in previously well buffered calcareous soil systems. We investigated the effects of five increasing ammonium-N fertilizer rates in a Platner loam, on physical and chemical changes at the 0 to 5, and 0 to 15-cm depths after three cycles of no-till wheat (Triticum aestivum L.)-corn (Zea mays L.)-fallow rotation. The measured soil pH, texture, bulk density, cation exchange capacity (CEC), total P, soluble and total soil organic carbon (SOC), nitrate-N to a depth of 60 cm, and grain yields. No significant changes were found with soil texture, bulk densities, CEC, and total P. The data showed a significant reduction in surface (0-5 cm) soil pH (6.5 to 5.1) with the highest N rate (112 kg/ha), but this was accompanied by a 40% increase in SOC. Although there were significant increases in Al and Mn and decreases in Ca concentrations in the surface 0 to 5 cm at the highest N rate, no reduction in grain yields occurred relative to lower N levels with near neutral pHs. Because only a shallow depth of the soil was affected, residue, SOM, and rapid root growth could be compensating for surface acidity, Over the longer term, we need to monitor the effects of ammoniacal-N on downward soil acidity and yield trends under these new intensive cropping systems.
  • Authors:
    • Lyon, D. J.
    • Tanaka, D. L.
    • Jones, O. R.
    • Havlin, J. L.
    • Halvorson, A. D.
    • Peterson, G. A.
    • Pennock, D. J.
  • Source: Soil & Tillage Research
  • Volume: 47
  • Issue: 3
  • Year: 1998
  • Summary: Concern about soil organic matter losses as a result of cultivation has been voiced consistently since the early part of the 20th century. Scientists working in the U.S. Great Plains recognized that organic matter losses from an already small pool could have major negative consequences on soil physical properties and N supplying capacity. The advent of reduced- and no-till systems has greatly improved our ability to capture and retain precipitation in the soil during the non-crop periods of the cropping cycle, and has made it possible to reduce fallow frequency and intensify cropping systems. The purpose of this paper is to summarize the effects of reduced tillage and cropping system intensification on C storage in soils using data from experiments in North Dakota, Nebraska, Kansas, Colorado, and Texas. Decades of farming with the wheat (Triticum aestivum L.)-fallow system, the dominant farming system in the Great Plains, have accentuated soil C losses. More intensive cropping systems, made possible by the greater water conservation associated with no-till practices, have produced more grain, produced more crop residue and allowed more of it to remain on the soil surface. Combined with less soil disturbance in reduced- and no-till systems, intensive cropping has increased C storage in the soil. We also conclude that the effects of cropping system intensification on soil C should not be investigated independent of residue C still on the surface. There are many unknowns regarding how rapidly changes in soil C will occur when tillage and cropping systems are changed, but the data summarized in this paper indicate that in the surface 2.5 cm of soil, changes can be detected within 10 years. It is imperative that we continue long-term experiments to evaluate rates of change over an extended period. It is also apparent that we should include residue C, both on the surface of the soil and within the surface 2.5 cm, in our system C budgets if we are to accurately depict residue±soil C system status. The accounting of soil C must be done on a mass basis rather than on a concentration basis.
  • Authors:
    • Paustian, K.
    • Elliott, E. T.
    • Six ,J.
  • Source: Soil Science Society of America Journal
  • Volume: 63
  • Issue: 5
  • Year: 1998
  • Summary: Tillage generally reduces aggregation and particulate organic matter (POM) content. We hypothesized that reduced C sequestration in conventional tillage (CT) compared with no-tillage (NT) is related to differences in aggregate turnover. Four soils (Haplustoll, Fragiudalf, Hapludalf, and Paleudalf), each with NT, CT, and native vegetation (NV) treatments, were separated into aggregates. Free light fraction (LF) and intraaggregate POM (iPOM) were isolated. At one site we used 13C natural abundance to differentiate crop- and grassland-derived C. Concentrations of coarse iPOM C (250-2000 {micro}m iPOM in macroaggregates), expressed on a per unit aggregate weight (g iPOM C kg-1 aggregate), did not differ between tillage treatments. In contrast, concentrations of fine iPOM C (53-250 {micro}m iPOM in macroaggregates) were less in CT compared to NT macroaggregates. On a whole soil basis, fine iPOM C was on average 51% less in CT than in NT, and accounted for 21% of the total C difference between NT and CT. The concentration of free LF C was not affected by tillage, but was on average 45% less in the cultivated systems than NV. Proportions of crop-derived C in macroaggregates were similar in NT and CT, but were three times greater in microaggregates from NT than microaggregates from CT. We suggest that a faster turnover rate of macroaggregates in CT compared with NT leads to a slower rate of microaggregate formation within macroaggregates and less stabilization of new SOM in free microaggregates under CT.
  • Authors:
    • Smith, J. U.
    • Glendining, M. J.
    • Powlson, D. S.
    • Smith, P.
  • Source: Global Change Biology
  • Volume: 4
  • Issue: 6
  • Year: 1998
  • Summary: In this paper we estimate the European potential for carbon mitigation of no-till farming using results from European tillage experiments. Our calculations suggest some potential in terms of (a) reduced agricultural fossil fuel emissions, and (b) increased soil carbon sequestration. We estimate that 100% conversion to no-till farming would be likely to sequester about 23 Tg C y-1 in the European Union or about 43 Tg C y-1 in the wider Europe (excluding the former Soviet Union). In addition, up to 3.2 Tg C y-1 could be saved in agricultural fossil fuel emissions. Compared to estimates of the potential for carbon sequestration of other carbon mitigation options, no-till agriculture shows nearly twice the potential of scenarios whereby soils are amended with organic materials. Our calculations suggest that 100% conversion to no-till agriculture in Europe could mitigate all fossil fuel-carbon emissions from agriculture in Europe. However, this is equivalent to only about 4.1% of total anthropogenic CO2-carbon produced annually in Europe (excluding the former Soviet Union) which in turn is equivalent to about 0.8% of global annual anthropogenic CO2-carbon emissions.
  • Authors:
    • Sanabria, J.
    • Atwood, J. D.
    • Uri, N. D.
  • Source: Science of The Total Environment
  • Volume: 216
  • Issue: 1-2
  • Year: 1998
  • Summary: Every production practice, including conservation tillage, has positive or negative environmental consequences that may involve air, land, water, and/or the health and ecological status of wildlife. The negative impacts associated with agricultural production, and the use of conventional tillage systems in particular, include soil erosion, energy use, leaching and runoff of agricultural chemicals, and carbon emissions. Several of these impacts are quantified. The conclusions suggest that the use of conservation tillage does result in less of an adverse impact on the environment from agricultural production than does conventional tillage by reducing surface water runoff and wind erosion. Additionally, wildlife habitat will be enhanced to some extent with the adoption of conservation tillage and the benefits to be gained from carbon sequestration will depend on the soil remaining undisturbed. Finally, further expansion of conservation tillage on highly erodible land will unquestionably result in an increase in social benefits, but the expected gains will be modest.
  • Authors:
    • Heinemeyer, O.
    • Lyon, D. J.
    • Drijber, R. A.
    • Doran, J. W.
    • Mosier, A. R.
    • Kessavalou, A.
  • Source: Journal of Environmental Quality
  • Volume: 27
  • Issue: 5
  • Year: 1998
  • Summary: Cropping and tillage management can increase atmospheric CO2, N2O, and CH4 concentrations, and contribute to global warming and destruction of the ozone layer. Fluxes of these gases in vented surface chambers, and water-filled pore space (WFPS) and temperature of survace soil were measured weekly from a long-term winter wheat (Triticum aestivum L.)-fallow rotation system under chemical (no-tillage) and mechanical tillage (noninversion subtillage at 7 to 10 cm or moldboard plowing to 15 cm) follow management and compared with those from "native" grass sod at Sidney, NE, from March 1993 to July 1995. Cropping, tillage, within-field location, time of year, soil temperature, and WFPS influenced net greenhouse gas fluxes. Mean annual interrow CO2 emissions from wheat-fallow ranged from 6.9 to 20.1 kg C ha-1 d-1 and generally increased with intensity and degree of tillage (no-till least and plow greatest). Nitrous oxide flux averaged summer > autumn > winter. Winter periods accounted for 4 to 10% and 3 to 47% of the annual CO2 and N2O flux, respectively, and 12 to 21% of the annual CH4 uptake. Fluxes of CO2 and N2O, and CH4 uptake increased linearly with soil temperature. No-till fallow exhibited the least threat to deterioration of atmospheric or soil quality as reflected by greater CH4 uptake, decreased N2O and CO2 emissions, and less loss of soil organic C than tilled soils. However, potential for increased C sequestration in this wheat-fallow system is limited due to reduced C input from intermittent cropping.
  • Authors:
    • Bluhm, G.
    • Smith, J. L.
    • Mummey, D. L.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 70
  • Issue: 1
  • Year: 1998
  • Summary: Although agricultural soil management is the predominant anthropogenic source of nitrous oxide (N2O) to the atmosphere, little is known about the effects of alternative soil management practices on N2O emissions. In this study the NGAS model of Parton et al. (1996), coupled with a N and C cycling model, was used to simulate annual N2O emissions from 2639 cropland sites in the US using both no-till and conventional tillage management scenarios. The N2O mitigation potential of returning marginal cropland to perennial grass was also evaluated by comparing simulated N2O emissions from 306 Conservation Reserve Program (CRP) grassland sites with emissions from nearby cropland sites. Extensive soil and land use data for each site was obtained from the Natural Resource Inventory (NRI) database and weather data was obtained from NASA. The initial conversion of agricultural land to no-till showed greater N2O emissions per hectare than conventional tillage. Differences between the two tillage scenarios were strongly regional and suggest that conversion of conventionally tilled soil to no-till may have a greater effect on N2O emissions in drier regions. About 80% of the total emissions were from the Great plains and central regions mainly due to their large cultivated area. Croplands producing soy, wheat, and corn were responsible for about 68% of the total emissions with rice, cotton, and vegetable croplands having the greatest N2O flux (6.5-8.4 kg N2O-N ha-1 yr-1) under either scenario. Model simulations estimate that the agricultural lands in the US produce 448 Gg N2O-N y-1 under a conventional tillage scenario and 478 Gg N2O-N yr-1 under a no-till scenario. Model estimates also suggest that the conversion of 10.5 million hectares of cropland to grassland has a N2O mitigation potential of 31 Gg N2O-N yr-1, (8.4 Tg carbon equivalents yr-1). This value is similar in magnitude to many of the major greenhouse gas (GHG) emission-reduction strategies currently being considered to help meet US GHG reduction goals. Thus the GHG mitigation potential of this conversion is substantial and may be a viable strategy to help meet GHG reduction goals.
  • Authors:
    • Vitosh, M. L.
    • Pierce, F. J.
    • Christenson, D. R.
    • Peters, S. E.
    • Frye, W. W.
    • Blevins, R. L.
    • Dick, W. A.
  • Source: Soil & Tillage Research
  • Volume: 47
  • Issue: 3-4
  • Year: 1998
  • Summary: Soil organic matter has recently been implicated as an important sink for atmospheric carbon dioxide (CO2), However, the relative impacts of various agricultural management practices on soil organic matter dynamics and, therefore, C sequestration at spatial scales larger than a single plot or times longer than the typical three year experiment have rarely been reported. Results of maintaining agricultural management practices in the forest-derived soils of the eastern Corn (Zea mays L.) Belt states of Kentucky, Michigan, Ohio and Pennsylvania (USA) were studied. We found annual organic C input and tillage intensity were the most important factors in affecting C sequestration. The impact of rotation on C sequestration was primarily related to the way it altered annual total C inputs. The removal of above-ground plant biomass and use of cover crops were of lesser importance, The most rapid changes in soil organic matter content occurred during the first five years after a management practice was imposed with slower changes occurring thereafter. Certain management practices, e.g, no-tillage (NT), increased the soil's ability to sequester atmospheric CO2. The impact of this sequestration will be significant only when these practices are used extensively on a large percentage of cropland and when the C-building practices are maintained, Any soil C sequestered will be rapidly mineralized to CO2 if the soil organic matter building practices are not maintained,
  • Authors:
    • Paustian, K.
    • Elliott, E. T.
    • Doran, J. W.
  • Source: Soil & Tillage Research
  • Volume: 49
  • Issue: 1-2
  • Year: 1998
  • Summary: Two experiments were established in 1969 and 1970 near Sidney, NE, to determine the effect of moldboard plow (plow), sub-tillage (sub-till), and no-tillage (no-till) fallow management on soil properties, biological activities, and carbon and nitrogen cycling. One experiment was on land which had been broken from sod in 1920, seeded to crested wheatgrass [Agropyron cristatum (L.) Gaertn.] from 1957 to 1967, and cultivated for wheat again in 1967 (Previously Cultivated site). The second experiment was established on land that was in native mixed prairie sod until 1969 (Native Sod site), and compared the three tillage management practices listed above in a winter wheat-fallow system as well as replicated plots remaining in sod. Soil sampling done 10-12 years after these experiments were initiated, indicated that the biological environment near the soil surface (0-30 cm) with no-till was often cooler and wetter than that with conventional tillage management practices, especially moldboard plowing. Biological activity and organic C and N reserves were concentrated nearer the soil surface (0-7.6 cm) with no-tillage, resulting in greater potential for tie-up of plant available N in organic forms. However, regardless of tillage practice with wheat-fallow management at either site, long-term (22-27 years) losses of soil organic C from surface soil (0-30 cm) ranged from 12 to 32% (320-530 kg C ha(-1) year(-1)), respectively, for no-till and plowing. These soil C losses were closely approximated by losses measured to a depth of 122 cm, indicating that under the cropping, tillage, and climatic conditions of this study, soil C changes were adequately monitored by sampling to a depth of 30 cm within which most C loss occurs. No-till management maintains a protective surface cover of residue and partially decomposed materials near the soil surface. However, the decline in soil organic matter, and associated degradation in soil quality, will likely only be slowed by increasing C inputs to soil through use of a more intensive cropping system which increases the time of cropping and reduces the time in fallow. (C) 1998 Elsevier Science B.V. All rights reserved.