• Authors:
    • Potter, J. W.
    • Cerkauskas, R. F.
    • McKeown, A. W.
    • Van Driel, L.
  • Source: Canadian Journal of Plant Science
  • Volume: 78
  • Issue: 2
  • Year: 1998
  • Summary: A 6-yr (1987-1992) experiment, continuous on the same site, evaluated potential problems for yield, nematodes and diseases with tomatoes (Lycopersicon esculentum Mill.) grown in a strip-till system. Treatments consisted of conventional tillage (CT) and strip tillage (ST), rye (Secale cereale L.), wheat (Triticum aestivum L.) and perennial ryegrass (Lolium perenne L.) cover crops and a 2-yr rye-tomato rotation. Results of the first 5 yr indicated a decrease in tomato yield over time for both tillage treatments and cover crops. However, yield rebounded overall for treatments in 1992 with the highest yield in the rye-tomato rotation. We suspect this was a result of high populations of root-knot nematodes which collapsed over the winter of 1991/1992. Tomato yields were lower following wheat and perennial ryegrass than rye. In only 1 yr out of 6, strip-tillage reduced yield compared with conventional tillage. Bacterial speck/spot symptoms on foliage, although minor, were significantly greater in ST than in CT plots during the last 3 yr. No major trends in incidence and severity of bacterial and fungal diseases and of disorders of fruit were evident during the 5-yr period and neither fruit yield nor quality were significantly affected by these factors. Root-knot nematodes (Meloidogyne hapla Chitwood) were numerically less in the rye-tomato rotation than in other treatments; both root-knot and root lesion nematodes (Pratylenchus penetrans [Cobb]) tended to be less numerous under CT than under ST. Strip-tillage is feasible for machine harvest processing tomatoes. However, we are concerned about the tendency of tomatoes grown under reduced tillage to have lower yields than those grown under conventional tillage. More work is required on the interactions of cultivars, cover crops and nematodes in soil conservation systems.
  • 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:
    • Naeth, M. A.
    • Chanasyk, D. S.
    • Sansom, J. J.
    • Bateman, J. C.
  • Source: Canadian Journal of Soil Science
  • Volume: 78
  • Issue: 4
  • Year: 1998
  • Summary: The effects of sulfur and gypsum amendments in conjunction with crop management (fallow/barley and forage) on soil physical properties, soil moisture and vegetation characteristics were measured on a sodic and calcareous sandy loam minespoil at the Highvale coal mine, west of Edmonton, Alberta. Amendment and crop management had no significant effect on bulk density, plant species composition, canopy cover, ground cover or annual aboveground biomass. Crop management significantly affected penetration resistance (which was generally higher under forage), while amendment treatments did not. Profile soil moisture was lowest within the gypsum-amended plots at all depths, and was similar for sulfur-amended and control plots. Crop management affected profile soil moisture, with significantly less moisture under continuous forage than fallow/barley. As percolation is critical to the effectiveness of amendments in the amelioration process, cereal/fallow rotations are more effective than continuous forage in facilitating that process.
  • 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.
  • Authors:
    • Oenema, O.
    • Silvola, J.
    • Martikainen, P.
    • Berglund, K.
    • Klemedtsson, L.
    • Kasimir-Klemedtsson, Å.
  • Source: Soil Use and Management
  • Volume: 13
  • Issue: s4
  • Year: 1997
  • Summary: The large boreal peatland ecosystems sequester carbon and nitrogen from the atmosphere due to a low oxygen pressure in waterlogged peat. Consequently they are sinks for CO2 and strong emitters of CH4. Drainage and cultivation of peatlands allows oxygen to enter the soil, which initiates decomposition of the stored organic material, and in turn CO2 and N2O emissions increase while CH4 emissions decrease. Compared to undrained peat, draining of organic soils for agricultural purposes increases the emissions of greenhouse gases (CO2, CH4, and N2O) by roughly 1t CO2 equivalents/ha per year. Although farmed organic soils in most European countries represent a minor part of the total agricultural area, these soils contribute significantly to national greenhouse gas budgets. Consequently, farmed organic soils are potential targets for policy makers in search of socially acceptable and economically cost-efficient measures to mitigate climate gas emissions from agriculture. Despite a scarcity of knowledge about greenhouse gas emissions from these soils, this paper addresses the emissions and possible control of the three greenhouse gases by different managements of organic soils. More precise information is needed regarding the present trace gas fluxes from these soils, as well as predictions of future emissions under alternative management regimes, before any definite policies can be devised.
  • Authors:
    • Lichtenberg, E.
    • Hanson, J. C.
    • Peters, S. E.
  • Source: American Journal of Alternative Agriculture
  • Volume: 12
  • Issue: 1
  • Year: 1997
  • Summary: Compares the profitability of the organic and conventional cash grain rotations since 1982. Dependence of sustainable farming on the generated income from farmers; Conduct of a Farming Systems Trial; Analysis of two FST systems; Advantage of the organic rotation; Tabulation of net returns for three different periods; Net returns and labor requirements.
  • Authors:
    • Kissel, D. E.
    • Havlin, J. L.
  • Source: Soil Organic Matter in Temperate Agroecosystems: Long-Term Experiments in North America
  • Volume: 1
  • Year: 1997
  • Authors:
    • Tanaka, D. L.
    • Black, A. L.
  • Source: Soil Organic Matter in Temperate Agroecosystems
  • Year: 1997
  • Authors:
    • Blair, J. M.
  • Source: Ecology
  • Volume: 78
  • Issue: 8
  • Year: 1997
  • Summary: In tallgrass prairie, periodic spring fires often result in enhanced aboveground net primary productivity (ANPP) that exceeds the productivity of either annually burned or unburned sites. This study evaluated two alternate hypotheses for the "pulse" in productivity following an infrequent fire: (1) enhanced ANPP results from increased net N mineralization rates due to the removal of surface litter and elevated soil temperatures following fire (the enhanced mineralization hypothesis) or (2) enhanced ANPP results from a transient release from both light and N limitation during a nonequilibrium period as a switch from energy to N limitation occurs (the transient maxima hypothesis). The former hypothesis predicts greater N availability following an infrequent fire, relative to either annually burned or unburned prairie. The latter predicts that N availability following an infrequent fire will decline to intermediate levels, relative to unburned and annually burned prairie, and continue to decline with successive annual fires. To test these hypotheses, I measured inorganic soil N, net N mineralization rates, and plant productivity and N content at Konza Prairie in sites with several different burn histories (unburned, annually burned, infrequently burned). Inorganic soil N and cumulative net N mineralization rates were greatest on the unburned sites, lowest in annually burned sites, and intermediate in infrequently burned sites. Net N mineralization rates and plant tissue N content both declined with successive spring burning. These results did not support the enhanced mineralization hypothesis but indicated that enhanced ANPP following an infrequent fire resulted from an accumulation of inorganic and mineralizable N in the absence of fire which, under conditions of adequate light availability, was utilized following a spring fire. This is consistent with the transient maxima hypothesis and suggests that nonequilibrium responses to multiple, variable resources (light, energy, N) are an important aspect of tallgrass prairie ecosystem dynamics.