• 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:
    • Cadrin, F.
    • Fan, M. X.
    • MacKenzie, A. F.
  • Source: Journal of Environmental Quality
  • Volume: 27
  • Issue: 3
  • Year: 1998
  • Summary: Nitrous oxide (N2O) produced from agricultural activities must be determined if management procedures to reduce emissions are to be established. From 1994 to 1996, N2O emissions were determined using a closed chamber technique. Continuous corn (Zea mays L.) at four N rates of 0, 170, 285, and 400 kg of N ha-1 was used on a Ste. Rosalie heavy clay (a very-fine-silty, mixed, nonacid, frigid Typic Humaquept) and a Chicot sandy loam (a fine-loamy, frigid, Typic Hapludalf). On two additional sites, a Ste. Rosalie clay and an Ormstown silty clay loam (a fine-silty, mixed, nonacid, frigid Humaquept) no-till (NT) and conventional tillage (CT); monocultural corn (CCC), monocultural soybean (Glycine max L.) (SSS); corn-soybean (SSC, CCS); and soybean-corn-alfalfa (Medicago sativa L.) phased rotations (SAC, CSA, and ACS) were used. Nitrogen rates of 0, 90, and 180 kg of N ha-1 for corn and 0, 20, and 40 kg of N ha-1 for SSS were used. Rates of N2O emission were measured from April to November in 1994 and 1995, and from mid-March to mid-November in 1996. Maximum N2O emissions reached from 120 to 450 ng of N m-2 s-1 at the Ormstown site to 50 to 240 ng of N m-2 s-1 at the Ste. Rosalie soil. Generally, N2O emissions were higher in the NT systems, with corn, and increased linearly with increasing N rates, and amounted to 1.0 to 1.6% of fertilizer N applied. The N2O emission rates were significantly related to soil denitrification rates, water-filled pore space, and soil NH4 and NO3 concentrations. A corn system using conventional tillage, legumes in rotation, and reduced N fertilizer would decrease N2O emission from agricultural fields.
  • Authors:
    • Johnson, D. E.
    • Minami, K.
    • Heinemeyer, O.
    • Freney, J. R.
    • Duxbury, J. M.
    • Mosier, A. R.
  • Source: Climatic Change
  • Volume: 40
  • Issue: 1
  • Year: 1998
  • Summary: Agricultural crop and animal production systems are important sources and sinks for atmospheric methane (CH4). The major CH4 sources from this sector are ruminant animals, flooded rice fields, animal waste and biomass burning which total about one third of all global emissions. This paper discusses the factors that influence CH4 production and emission from these sources and the aerobic soil sink for atmospheric CH4 and assesses the magnitude of each source. Potential methods of mitigating CH4 emissions from the major sources could lead to improved crop and animal productivity. The global impact of using the mitigation options suggested could potentially decrease agricultural CH4 emissions by about 30%.
  • 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:
    • Myers, R.
    • Pullins, E.
  • Source: American Journal of Alternative Agriculture
  • Volume: 13
  • Issue: 3
  • Year: 1998
  • Summary: The agronomic and economic performance of five alternative crops was assessed in comparison to the no-till wheat-soyabean double-cropping system prevalent in the southern Corn Belt of the USA. A field site was established in 1992 at the University of Missouri-Columbia and two further sites in Missouri were added in 1993. Amaranth, buckwheat, sunflower, and pearl millet were planted after the harvest of canola [rape] or wheat, or after fallow. Alternative double-crop grain yield, production costs, and net returns were compared with those of double-crop soyabean. Wheat yielded more than canola. Sunflower grain yields did not differ significantly after winter-crop treatments at any site. Yields of amaranth, buckwheat, soyabean, and pearl millet differed after winter crops at some sites. At three study yield levels, net returns were positive and greatest for double-crop wheat-amaranth, canola-amaranth, wheat-sunflower, and canola-sunflower systems. All double-crop systems except canola-pearl millet had positive net returns at median study yield levels. Low or negative net returns resulted from the combination of low yield and low price for some double crops. Canola was shown to be an economically feasible alternative to wheat in a double-cropping system for central and southern Missouri. Buckwheat and sunflower were shown to be agronomically and economically competitive alternatives to soyabean following either canola or winter wheat, with buckwheat most valuable in late-season planting conditions.
  • Authors:
    • Doran, J. W.
    • Koerner, P. T.
    • Power, J. F.
    • Wilhelm, W. W.
  • Source: Soil Science Society of America Journal
  • Volume: 62
  • Issue: 5
  • Year: 1998
  • Summary: Returning crop residue improves water conservation and storage, nutrient availability, and crop yields, We have little knowledge, however, er, of the residual impacts of crop residues on soil properties and crop production. We hypothesized that residual impacts of crop residues vary with the amount of residues used. A 10-yr study near Lincoln, NE, evaluated the residual effects of an earlier 8-yr study of various crop residue amounts on crop growth and selected soil properties. From 1978 through 1985, crop residues were returned at 0, 50, 100, and 150% of the quantity produced by the previous crop (averaging 0 to approximate to 6 Mg ha(-1) yr(-1)). Continuous corn (Zea mays L.) was produced 1986 through 1995 on these plots, except sorghum [Sorghum bicolor (L.) Moench] was substituted in several years. To study management effects on residual responses, plots were subdivided with or without tillage, N fertilizer (60 kg N ha(-1)), and hairy vetch (Vicia villosa L.) cover crop. Residual effects of the 150% residue amount increased grain production 16% compared with the 0% amount (4900 vs. 4250 kg ha(-1), respectively), and were not affected by time or other management practices. Increasing previous residue amount did enhance soil N availability (from 73.0 to 82.3 kg autoclave-mineralizable N ha(-1)) and Bray soil P (16.7 to 20.3 kg ka(-1)). These results are among the first to show that residual effects of crop residue are prolonged (half-life of approximate to 10 yr) and probably result from changes in soil properties that enhance soil nutrient availability.
  • Authors:
    • Norwood, C.
    • Currie, R.
  • Source: Journal of Production Agriculture
  • Volume: 10
  • Issue: 1
  • Year: 1997
  • Summary: Dryland crop yields in the U.S. Great Plains are limited by low precipitation and high potential evapotranspiration. In western Kansas wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] are grown commonly, whereas corn (Zea mays L.) is believed to lack sufficient drought and heat tolerance for dryland production. A study was conducted near Garden City, KS, from 1991 through 1995 to determine whether corn could be grown successfully. No-till (NT) and conventional-till (CT) corn and grain sorghum were compared. In the driest year, sorghum yielded 137% more than corn with CT and 85% more with NT, but in 3 of 5 yr, NT corn yielded from 34% to 112% more than NT sorghum. In the remaining year, CT sorghum yielded more than CT corn, but NT yields did not differ. Overall, NT increased corn yields by 28% and net return by 69%, but increased sorghum yields by only 11% add had no effect on net return. No-till corn yielded 28% more than NT sorghum and produced 169% more net return, whereas CT corn yielded 11% more than CT sorghum and produced 48% more net return. Dryland corn can be grown in western Kansas if lower yields and returns are accepted in dry years in exchange for yields and returns considerably higher than those of sorghum in favorable years. No tillage will substantially increase yields in most years and is essential to assure adequate corn yields in dry years.
  • Authors:
    • Lyon, D. J.
    • Peterson, G. A.
    • Halvorson, A. D.
    • Leavitt, S. W.
    • Follett, R. F.
    • Paul, E. A.
  • Source: Soil Science Society of America Journal
  • Volume: 61
  • Issue: 4
  • Year: 1997
  • Summary: The size and turnover rate of the resistant soil organic matter (SOM) fractions were measured by 14C dating and 13C/12C measurements. This involved soils archived in 1948, and recent samples, from a series of long-term sites in the North American Great Plains. A reevaluation of C dates obtained in the 1960s expanded the study scope. The 14C ages of surface soils were modern in some native sites and near modern in the low, moist areas of the landscape. They were much older at the catena summits. The 14C ages were not related to latitude although this strongly influenced the total SOM content. Cultivation resulted in lower C contents and increased the 14C age by an average of 900 yr. The 10- to 20-cm depths from both cultivated and native sites were 1200 yr older than the 0- to 10-cm depth. The 90- to 120-cm depth of a cultivated site at 7015 yr before present (BP) was 6000 yr older than the surface. The nonhydrolyzable C of this depth dated 9035 yr BP. The residue of 6 M HCl hydrolysis comprised 23 to 70% of the total soil C and was, on the average, 1500 yr older. The percentage of nonhydrolyzable C and its 14C age analytically identify the amount and turnover rate of the old resistant soil C.
  • Authors:
    • Dick, W. A.
    • Jacinthe P. -A.
  • Source: Soil & Tillage Research
  • Volume: 41
  • Issue: 3-4
  • Year: 1997
  • Summary: Nitrous oxide (N2O) is an important atmospheric trace gas due to its involvement in the postulated global warming phenomenon and in the depletion of the ozone layer. Widespread concern has been triggered by recent reports of increased atmospheric N2O concentration. Since agriculture has been implicated as one contributor to that increase, a monitoring program was undertaken during the 1993 and 1994 cropping season (May-October) to evaluate the effect of several soil management practices on N2O emission from soil. Our results show that rates of N2O emission were generally near baseline levels during most sampling occasions. Major, but short-lived, fluxes of N2O were observed after rainfall events and during the days immediately following fertilizer application. It was during these times that most of the seasonal N2O loss occurred. An excellent relationship was found between seasonal N2O loss (y) and the maximum daily flux of N2O (x) during a season (y = -0.4x2 + 43.1x + 338, r2 = 0.89, P < 0.0001). The N2O emission data were log normally distributed for both years. Average daily emissions of N2O were 6.9 ± 6.3 g (range, 0.3 - 74.7 g) N2O---N ha-1 day-1 and 17.6 ± 10.5 g (range, 0.1-326 g) N2O---N ha-1 day-1 during the 1993 and 1994 seasons, respectively. Seasonal N2O---N losses were, in general, highest in the continuous corn (CC) (Zea mays L.) plots and lowest in the soybean (Glycine max L.) plots of the corn/soybean/wheat (Triticum aestivum L.)-hairy vetch (Vicia villosa Roth) rotation (CSW-V). Average N loss as N2O during a cropping season was between 0.6 kg (for the soybean crop of the CSWV rotation and ridge till treatment) and 3.7 kg N2O---N ha-1 year-1, (for the CC rotation and the chisel till treatment). Approximately 0.5-3% of the inorganic N fertilizer added was lost as N2O. Our data show that seasonal N2O---N loss from chisel-till plots were generally significantly higher than from no-till or ridge till plots.