• Authors:
    • Pannkuk, C. D.
    • McCool, D. K.
  • Source: 2000 ASAE Annual International Meeting, Technical Papers: Engineering Solutions for a New Century. 
  • Year: 2000
  • Summary: Burn/low-till management of winter wheat is being practiced by some growers in the higher rainfall areas of the Pacific Northwest Wheat Region. The burning eliminates the numerous seedbed tillage operations that are normally required to reduce residues and control weeds and diseases in continuous winter wheat production. Detrimental effects of burn and till systems are well documented. However, there is little or no data on the effects of burning with no or low-till annual cropping on either erosion or soil quality. A three-year field study comparing erosion resulting from burn/low-till (BLT) seeded winter wheat following winter wheat and conventionally managed (CM) winter wheat following various crops was completed in 1997. Results indicate soil loss from the BLT fields was not significantly different from that from the CM fields with various crops preceding winter wheat. For the BLT fields, soil loss was as closely related to soil disturbance (tillage operations) as to surface residue. When residue and crop cover did not differ with the number of tillage operations, an increased number of tillage operations after burning loosened the soil and resulted in greater soil loss. The results of this study indicate no adverse effects on soil loss from using the BLT with one or two-pass seeding of winter wheat following winter wheat.
  • Authors:
    • Sherrod, L.
    • Ahuja, L. R.
    • Peterson, G. A.
    • Shaffer, M. J.
    • Rojas, K. W.
    • Ma, L. W.
  • Source: Agronomy Journal
  • Volume: 91
  • Issue: 3
  • Year: 1999
  • Summary: Decomposition of surface crop residues is important for agricultural management, especially under conservation tillage. The objective of this study was to test several models for describing crop residue decomposition under three eastern Colorado dryland agroecosystems at Sterling, Stratton, and Walsh with a yearly mean air temperature of 9.7, 10.4, and 12.0 degrees C, respectively. At each site, a soil toposequence common to its geographic region was chosen to include a summit, a sideslope, and a toeslope position, and several crop rotations were practiced under no-till conditions. Grab samples were taken at planting and before harvesting for surface residue measurement since 1985, Simulation results showed that the Douglas-Rickman model described surface crop residue decomposition better than the Gregory model during a 13-year period, based on a normalized objective function (NOF). Our fitted decomposition rate coefficients using the Douglas-Rickman model matched those originally published. The Douglas-Rickman model, which uses a first-order decay with respect to degree-days, was further evaluated against two other first-order decay models: one using a first-order decay equation with respect to decomposition-days and the other assuming a first order decay with respect to time (d), Although the three approaches performed equally well in terms of NOF values (P = 0.354), fitted decomposition rate coefficients were significantly different (P < 0.012) among the three experiment sites when models based on decomposition-days or on time (in days) were used. Therefore, the Douglas-Rickman model may be more applicable for describing long-term crop residue decomposition because of its consistency in model parameters among experimental sites and simplicity in modeling approach.
  • Authors:
    • Norwood, C. A.
  • Source: Agronomy Journal
  • Volume: 91
  • Issue: 1
  • Year: 1999
  • Summary: The dryland winter wheat (Triticum aestivum L,)-grain sorghum [Sorghum bicolor (L.) Moench]-fallow rotation is suitable for large areas of the U,S. Great Plains. High temperatures and potential evapotranspiration limit the number of other crops that can be grown, Sunflower (Helianthus annnus L.) is drought tolerant, but crops such as corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] are perceived to lark sufficient heat and drought tolerance for semiarid areas. A study was conducted near Garden City, KS, from 1991 through 1995 to compare yield and water uses of conventional tillage (CT) and no tillage (NT) corn, grain sorghum, sunflower, and soybean to determine if crops other than grain sorghum are suitable for dryland production. Conventional tillage (CT) and no tillage (NT) were included in a wheat-row crop-fallow rotation. Corn and soybean were similar in their depletion of soil water, as were sorghum and sunflower. Below a depth of 1.2 m, sorghum and sunflower removed the most water. Sunflower removed the most water nom the last 0.3 m of the profile and probably removed deeper water. Sorghum and sunflower removed an average of 19 mm more water from the 1.8-m soil profile than did corn and soybean. No-till increased yields of corn in 3 yr, of sorghum and sunflower in 2 yr, and of soybean in 1 yr, Corn had the greatest yield response to NT, averaging 31%. Average yields of corn were 25% higher than sorghum yields, whereas average yields of sunflower were 83% higher than soybean yields. Other crops can be successfully grown in the wheat-row crop-fallow rotation, but sorghum should occupy the most acres until the other crops have been tested under different climatic conditions.
  • Authors:
    • Singh, B. P.
    • Rahman, S.
    • Reddy, V. R.
    • Sainju, U. M.
  • Source: Journal of Environmental Quality
  • Volume: 28
  • Issue: 6
  • Year: 1999
  • Summary: Management practices can influence NO3-N content and movement in the soil. We examined the influence of 3 yr of tillage [no-till (NT), chisel (CH), and moldboard (MB)], cover crop [hairy vetch (Vicia villosa Roth) (HV), and no hairy vetch (NHV)], and N fertilization (0, 90, and 180 kg N ha(-1)) on residual NO3-N content and movement on a Norfolk sandy loam (fine-loamy, siliceous, thermic, Typic Kandiudults) under tomato (Lycopersicon esculentum Mill) in central Georgia. Because of low N recovery by tomato, NO3-N content in the soil increased with depth, regardless of treatments, and ranged from 127 to 316 kg ha(-1) at 0- to 120-cm depth in the fall (September 1997). The content increased with increasing rate of N addition from cover crop residue and N fertilizer. From fall to spring (March 1998), 22 to 58% (37 to 129 kg NO3-N ha(-1)) of this content was lost, mostly due to leaching. Greater loss occurred in NT than in CH or MB, with HV than with NHV, and with 180 or 90 than with 0 kg N ha(-1). Similarly, greater loss at 0- to 60-cm than at 60- to 120-cm depth and significant correlation between soil NO3-N and clay concentration with depth indicates that NO3-N moved from the surface layer to the underlying clay layer, where it moved slowly. Nitrate-N content and movement in the soil from cover crop residue and N fertilizer were similar. Minimum tillage reduced NO3-N movement compared with NT, yet avoided the negative effects on soil and water quality associated with MB. Although HV increased tomato N uptake and recovery, it was not effective in reducing NO3-N content and movement com pared with N fertilizer.
  • Authors:
    • Schomberg, H. H.
    • Jones, O. R.
  • Source: Soil Science Society of America Journal
  • Volume: 63
  • Issue: 5
  • Year: 1999
  • Summary: Soil C and N greatly influence Long-term sustainability of agricultural systems, We hypothesized that cropping and tillage differentially influence dryland soil C and N characteristics in the Southern High Plains. A Pullman clay loam (fine, mixed, thermic Torrertic Paleustol) cropped to vc heat (Triticum aestivum L.)-sorghum [Sorghum bicolor (L) Moench]-fallow (WSF), continuous wheat (CW) and continuous sorghum (CS) under no-tillage (NT), and stubble mulch (SM) was sampled at three depths to determine soil C and N characteristics. For CW, CS, and WSF phases (F-WSF, S-WSF, W-WSF), soil organic C (SOC) averaged 10.6 to 13.1 kg m(-3) and was greatest for CW, Carbon mineralization (C-MIN) at 0 to 20 mm was 30 to 40% greater for CW and F-WSF than for CS, S-WSF, or W-WSF. Cropping system by depth influenced soil organic N (SON),vith greatest SON at 0 to 20 mm in CW (1.5 kg m(-3)). At 0 to 20 mm for SM and NT, SOC was 9.9 and 12.5 kg m(-3), soil microbial biomass C (SMBC) was 0.80 and 1.1 kg m(-3), and soil microbial biomass N (SMBN) was 0.14 and 0.11 kg m(-3). Also at 0 to 20 mm, NT had 60% greater C-MIN, 11% more SMBC as a portion SOC, and 25% more SON compared to SM. Summed for 0 to 80 mm, NT had more SOC (0.98 vs 0.85 kg m(-2)) and SON (0.10 vs 0.9 kg m(-2)) than SM, and CW had greater or equal C and N activity as other systems. Negative correlations between yield and SOC, SMBC, C-MIN, SON, and SMBN indicate N removal in grain negatively affects active and labile C and N pools. Under dryland conditions, C and N conservation is greater with NT and with winter wheat because of less soil disturbance and shorter fallow.
  • Authors:
    • Ray, D. E.
    • Slinsky, S. E.
    • Graham, R. L.
    • Becker, D. A.
    • de la Torre Ugarte, D.
    • Turhollow, A.
    • Perlack, R. L.
    • Walsh, M. E.
  • Year: 1999
  • Authors:
    • Black, A. L.
    • Krupinsky, J. M.
    • Merrill, S. D.
    • Halvorson, A. D.
  • Source: Agronomy Journal
  • Volume: 91
  • Issue: 4
  • Year: 1999
  • Summary: Winter wheat (Triticum aestivum L.) can add diversity to dryland crop rotations in the northern Great plains, but it is susceptible to winterkill in low surface residue environments. A 12-year study was conducted to determine the response of two winter wheat cultivars, Roughrider and Norstar; to tillage system (conventional-till, CT; minimum-till, MT: and no-till, NT) and N fertilizer rate (34, 67, and 101 kg N ha(-1)) in a dryland spring wheat-winter wheat-sunflower (Helianthus annuus L,) rotation. Grain yields were greater with MT (1968 kg ha(-1)) and NT (2022 kg ha(-1)) than with CT (1801 kg ha(-1)), but tillage system effects on grain yield varied among years, Increasing N rate from 34 kg N ha(-1) to 67 kg N ha(-1) increased grain production from 1844 to 1953 kg ha(-1), but yield response to N rate varied among years., The greatest overall grain yield (2111 kg ha(-1)) if as obtained with NT and application of 101 kg N ha(-1). Grain yields were lowest during gears when plant-available Hater (PAW) was 400 an PAW, leaf spot disease incidence was greatest, particularly at the lowest N rate with NT. Application of adequate N reduced the disease incidence in all tillage treatments. Cultivar differences Here significant 3 out of 12 years, but not consistent. Winterkill was a factor for both cultivars in only 1 year in the CT and MT plots. Winter wheat performed Hell as a rotational crop in this cropping system when using,tfT and NT systems and adequate N fertility, Our long-term results indicate that producers in the northern Great Plains ran use winter wheat successfully in annual cropping systems that do not include a fallow period, particularly if NT is used with adequate N fertilization.
  • Authors:
    • Merrill, S. D.
    • Tanaka, D. L.
    • Black, A. L.
    • Halvorson, A. D.
    • Krupinsky, J. M.
  • Source: Agronomy Journal
  • Volume: 91
  • Issue: 4
  • Year: 1999
  • Summary: Sunflower (Helianthus annuus L.) is a warm-season, intermediate water-use crop that can add diversity to dryland crop rotations, Reduced tillage systems may Enhance sunflower yield in intensive cropping systems. A 12-year study was conducted to determine how sunflower cultivars of early and medium maturity respond to tillage system (conventional-till, CT; minimum-till, MT; no-till, NT) and N fertilization (34, 67, and 101 kg N ha(-1)) within a dryland spring wheat (Triticum aestivum L.)-winter wheat-sunflower rotation. Averaged across N rates, cultivars, and years, sunflower seed yields were greater with MT (1550 kg ha(-1)) than with NT (1460 kg ha(-1)) and CT (1450 kg ha(-1)). Increasing N rate above 34 kg N ha-L generally increased gain yield, but varied from year to year. The tillage X N interaction showed that the highest seed yields were obtained with NT (1638 kg ha(-1)) and MT (1614 kg ha(-1)) at 101 kg N ha(-1). Total plant-available water (TPAW) of 500 mm did not result in increased sunflower yields over those with 350 to 500 mm TPAW. Yield differences between cultivar maturity classes varied from year to gear and with tillage and N level. At the lowest N rate, weeds were more problematic in NT than in CT and MT plots. More N fertilizer may be needed with NT to optimize sunflower yields than with CT and MT, because of less residual soil NO3-N with NT. Results indicate that producers in the northern Great Plains can use sunflower successfully in annual a cropping systems, particularly if MT and NT are used with adequate N fertilization.
  • Authors:
    • NRCS,USDA
  • Year: 1999
  • Summary: from intro: "Cultural farming practices have a major influence on the quality of wildlife habitat provided by croplands on the agricultural landscape. In considering tillage practice alternatives, measures that reduce the amount of soil erosion are generally considered to help protect and enhance aquatic resources. However, it also is important to consider how various tillage practices affect terrestrial wildlife such as birds, mammals, reptiles and amphibians, and beneficial insects found in cropland situations."
  • Authors:
    • Schlesinger, W. H.
  • Source: Science
  • Volume: 284
  • Issue: 5423
  • Year: 1999
  • Summary: first paragraph, "Maintaining and increasing soil organic matter (SOM) adds to soil fertility, water retention, and crop production. Recently, many soil scientists have suggested that the sequestration of atmospheric carbon dioxide in SOM could also contribute significantly to attempts to adhere to the Kyoto Protocol. Conversion of large areas of cropland to conservation tillage, including no-till practices, during the next 30 years could sequester all the CO2 emitted from agricultural activities and up to 1% of today's fossil fuel emissions in the United States (1). Similarly, alternative management of agricultural soils in Europe could potentially provide a sink for about 0.8% of the world's current CO2 release from fossil fuel combustion (2). Beyond conservation tillage, however, many of the techniques recommended to increase carbon sequestration in soils contain hidden carbon "costs" in terms of greater emissions of CO2 into the atmosphere."