• Authors:
    • Easley, S.
    • Sheedy, J.
    • Smiley, R.
  • Source: Plant Disease
  • Volume: 92
  • Issue: 12
  • Year: 2008
  • Summary: Dryland field crops in the Pacific Northwest United States are commonly produced in silt loams infested by the root-lesion nematodes Pratylenchus neglectus and P. thornei. Soils at 30 sites in Oregon were sampled from 0 to 120 cm depth to examine the vertical distribution of these Pratylenchus spp. Both species were distributed through entire soil profiles of all cropping systems. Populations were generally greatest in the surface 30 cm, but sometimes high populations were detected at depths greater than 45 cm. Sampling to 30 cm depth allowed detection of more than 50% of the population in most sites, while sampling to 45 cm depth yielded more than 75% of the population in over 75% of the sites evaluated. Therefore, soil samples should be collected to 30 to 45 cm depth to accurately estimate populations of Pratylenchus spp. in dryland crops produced on silt loams in the Pacific Northwest. Populations of Pratylenchus spp. were found to be related to the most recently planted crop, with populations after barley, after wheat, and during summer fallow being detected in ascending order.
  • Authors:
    • Riitters, K. H.
    • Wade, T. G.
    • Neale, A. C.
    • Wickham, J. D.
    • Slonecker, E. T.
    • Edmonds, C. E.
    • Jones, K. B.
    • Kepnera, W. G.
  • Source: Ecological Indicators
  • Volume: 8
  • Issue: 1
  • Year: 2008
  • Summary: Healthy riparian ecosystems in and and semi-arid regions exhibit shifting patterns of vegetation in response to periodic flooding. Their conditions also depend upon the amount of grazing and other human uses. Taking advantage of these system properties, we developed and tested an approach that utilizes historical Landsat data to track changes in the patterns of greenness (Normalized Difference Vegetation Index) within riparian zones. We tested the approach in the Upper San Pedro River of southeastern Arizona of the US, an unimpounded river system that flows north into the US from northern Mexico. We evaluated changes in the pattern of greenness in the San Pedro River National Conservation Area (SPRNCA), an area protected from grazing and development since 1988, and in a relatively unprotected area north of the SPRNCA (NA). The SPRNCA exhibited greater positive changes in greenness than did the NA. The SPRNCA also exhibited larger, more continuous patches of positive change than did the NA. These pattern differences may reflect greater pressures from grazing and urban sprawl in the NA than in the SPRNCA, as well as differences in floodplain width, depth to ground water, and base geology. The SPRNCA has greater amounts of ground and surface water available to support a riparian gallery forest than does the NA, and this may have influenced changes during the study period. Estimates of the direction of greenness change (positive or negative) from satellite imagery were similar to estimates derived from aerial photography, except in areas where changes were from one type of shrub community to another, and in areas with agriculture. Change estimates in these areas may be more difficult because of relatively low greenness values, and because of differences in soil moisture, sun-angle, and crop rotations among the dates of data collection. The potential for applying a satellite-based, greenness change approach to evaluate riparian ecosystem condition over broad geographic areas is also discussed. (C) 2007 Elsevier Ltd. All rights reserved.
  • Authors:
    • Kremer, R. J.
    • Sudduth, K. A.
    • Kitchen, N. R.
    • Jung, W. K.
  • Source: Soil Science and Plant Nutrition
  • Volume: 54
  • Issue: 6
  • Year: 2008
  • Summary: Crop management has the potential to either enhance or degrade soil quality, which in turn impacts on crop production and the environment. Few studies have investigated how crop management affects soil quality over different landscape positions. The objective of the present study was to investigate how 12 years of annual cropping system (ACS) and conservation reserve program (CRP) practices impacted soil quality indicators at summit, backslope and footslope landscape positions of a claypan soil in north-central Missouri. Claypan soils are particularly poorly drained because of a restrictive high-clay subsoil layer and are vulnerable to high water erosion. Three replicates of four management systems were established in 1991 in a randomized complete block design, with landscape position as a split-block treatment. The management systems were investigated: (1) annual cropping system 1 (ACS1) was a mulch tillage (typically >= 30% of soil covered with residue after tillage operations) corn (Zea mays L.)-soybean (Glycine max (L.) Merr.) rotation system, (2) annual cropping system 2 (ACS2) was a no-till corn-soybean rotation system, (3) annual cropping system 3 (ACS3) was a no-till corn-soybean-wheat (Triticum aestivum L.) rotation system, with a cover crop following wheat, (4) CRP was a continuous cool-season grass and legume system. In 2002, soil cores (at depths of 0-7.5, 7.5-15 and 15-30 cm) were collected by landscape position and analyzed for physical, chemical and biological soil quality properties. No interactions were observed between landscape and crop management. Relative to management effects, soil organic carbon (SOC) significantly increased with 12 years of CRP management, but not with the other management systems. At the 0-7.5-cm soil depth in the CRP system, SOC increased over this period by 33% and soil total nitrogen storage increased by 34%. Soil aggregate stability was approximately 40% higher in the no-till management systems (ACS2 and ACS3) than in the tilled system (ACS1). Soil aggregation under CRP management was more than double that of the three grain-cropping systems. Soil bulk density at the shallow sampling depth was greater in ACS3 than in ACS1 and ACS2. In contrast to studies on other soil types, these results indicate only minor changes to claypan soil quality after 12 years of no-till management. The landscape had minor effects on the soil properties. Of note, SOC was significantly lower in the 7.5-15-cm soil depth at the footslope compared with the other landscape positions. We attribute this to wetter and more humid conditions at this position and extended periods of high microbial activity and SOC mineralization. We conclude that claypan soils degraded by historical cropping practices will benefit most from the adoption of CRP or CRP-like management.
  • Authors:
    • Reddy, K. N.
    • Zablotowicz, R. M.
    • Locke, M. A.
  • Source: Pest Management Science
  • Volume: 64
  • Issue: 4
  • Year: 2008
  • Summary: BACKGROUND: Conservation practices often associated with glyphosate-resistant crops, e.g. limited tillage and crop cover, improve soil conditions, but only limited research has evaluated their effects on soil in combination with glyphosate-resistant crops. It is assumed that conservation practices have similar benefits to soil whether or not glyphosate-resistant crops are used. This paper reviews the impact on soil of conservation practices and glyphosate-resistant crops, and presents data from a Mississippi field trial comparing glyphosate-resistant and non-glyphosate-resistant maize (Zea mays L.) and cotton (Gossypium hirsutum L.) under limited tillage management. RESULTS: Results from the reduced-tillage study indicate differences in soil biological and chemical properties owing to glyphosate-resistant crops. Under continuous glyphosate-resistant maize, soils maintained greater soil organic carbon and nitrogen as compared with continuous non-glyphosate-resistant maize, but no differences were measured in continuous cotton or in cotton rotated with maize. Soil microbial community structure based on total fatty acid methyl ester analysis indicated a significant effect of glyphosate-resistant crop following 5 years of continuous glyphosate-resistant crop as compared with the non-glyphosate-resistant crop system. Results from this study, as well as the literature review, indicate differences attributable to the interaction of conservation practices and glyphosate-resistant crop, but many are transient and benign for the soil ecosystem. CONCLUSIONS: Glyphosate use may result in minor effects on soil biological/chemical properties. However, enhanced organic carbon and plant residues in surface soils under conservation practices may buffer potential effects of glyphosate. Long-term field research established under various cropping systems and ecological regions is needed for critical assessment of glyphosate-resistant crop and conservation practice interactions. Published in 2008 by John Wiley & Sons, Ltd.
  • Authors:
    • Fletcher, P. S.
    • Kennedy, A. C.
    • Pannkuk, C. D.
    • McCool, D. K.
  • Source: Soil & Tillage Research
  • Volume: 101
  • Issue: 1-2
  • Year: 2008
  • Summary: Burn/low-till management of winter wheat (Triticum aestivum) is being practiced by some growers in the higher rainfall areas of the Pacific Northwestern Winter Wheat Region of the US. Residue burning eliminates the numerous seedbed tillage operations that are normally required to reduce residues and control weeds and diseases in continuous winter wheat production. The detrimental effects of burn and till systems on soil erosion are well documented. However, there is little or no data on the effects of burning with no-till or low-till annual cropping on either erosion or soil quality. A 3-year field study comparing winter season 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 of the CM fields with various crops preceding winter wheat. For the BLT fields, soil loss was as closely related to soil disturbance (number of tillage operations) as to the amount of 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. No adverse effects on soil loss or soil quality from using the BLT with one or two-pass seeding of winter wheat following winter wheat were found in this study. The results have implications for harvesting wheat stubble as a source of biomass, or as an alternative technique for initiating conversion from a conventional tillage to a no-till seeding system, without high initial investment in new seeding equipment.
  • Authors:
    • Balkcom, K. S.
    • Delaney, D. P.
    • Mitchell, C. C.
  • Source: Agronomy Journal
  • Volume: 100
  • Issue: 5
  • Year: 2008
  • Summary: After more than 110 yr, the Old Rotation experiment on the campus of Auburn University in Alabama continues to document the long-term effects of crop rotation and winter legume cover crops on sustainable cotton (Gossypium hirsutum L.) production in the southeastern United States. Long-term yields indicate that winter legumes are as effective as fertilizer N in producing maximum cotton yields and increasing soil organic carbon (SOC). Higher SOC resulted in higher crop yields. However, rotating cotton with corn (Zea mays L.) in a 2-yr rotation or with corn, winter wheat (Triticum aestivum L.), and soybean [Glycine max. (L.) Merr.] in a 3-yr rotation produced little long-term cotton yield advantage beyond that associated with SOC. Cotton yields without winter legumes nor fertilizer N are only slightly higher than they were 110 yr ago. Nonirrigated corn grain yields in rotation with cotton are typically low for central Alabama and appear limited by N. Yields of all crops on the Old Rotation increased with increasing rates of P and K through the 1950s. Since adoption of in-row subsoiling, high-residue, conservation tillage, and genetically modified cultivars; in 1997, all crops have produced their highest, nonirrigated, recorded yields since the experiment began: 1910 kg cotton lint ha(-1) in 2006, 14.8 Mg corn grain ha(-1) in 1999, 6.34 Mg wheat ha-1 in 2001, and 4.50 Mg soybean ha(-1) in 2004.
  • Authors:
    • Humburg, D. S.
    • Schumacher, T. E.
    • Osborne, S. L.
  • Source: Agricultural Journal
  • Volume: 3
  • Issue: 5
  • Year: 2008
  • Summary: Although no-till soil management has many benefits, including protecting the soil from erosion, improving soil organic matter and improving soil moisture storage, depending on environmental conditions there could be a number of potential problems. Implementation of no-till soil management in eastern South Dakota can lead to wet and cold soils at the time of planting. Cover crops have the potential to utilize excess soil moisture and improve soil conditions at planting. A field experiment was established to evaluate the impact of 14 different cover crop species as well as no cover crop and conventional tillage on soil conditions prior to corn planting and the impact on corn yield and quality. The experimental design was a randomized complete block design with 4 replications. Cover crops evaluated include a mixture of grass, legumes, cool and warm season crops. All cover crops were planted in early August (following spring wheat harvest) at recommended seeding rates. The following spring all plots were planted to corn ( Zea mays L.). The experiment was conducted in a 3 year crop rotation (soybean [ Glycine max (L.) Merrill]/spring wheat ( Triticum aestivum L.)-cover crop/corn). Cover crop species that survived the winter included hairy vetch, red clover, sweet clover, Alsike clover, slender wheatgrass and winter ryegrass. The presence of these species increased soil strength and reduced soil moisture. Corn grown following hairy vetch was the only treatment that exhibited a significant reduction in plant population. Corn yield for plots grown under red clover, winter ryegrass and no cover crop had yield significantly higher than corn grown after conventional tillage, hairy vetch and slender wheatgrass. This experiment illustrated the ability of cover crops to utilize excess soil moisture and increase soil strength compared to conventional tillage or no cover crop.
  • Authors:
    • Miller, P. S.
    • Karthikeyan, K. G.
    • Panuska, J. C.
  • Source: Geoderma
  • Volume: 145
  • Issue: 3-4
  • Year: 2008
  • Summary: The impact of field surface conditions and erosion processes on runoff volume, soil loss and sediment particle size during the rainfall runoff period was investigated. Results are reported for multiple events and from within individual events (intra-event) for sites with different corn (Zea mays L.) management systems (i.e., grain (CG), silage (CS), and silage-manure (CSM)). The multi-event bulk runoff volume and soil loss for CG were less than that for CS and CSM due to higher residue levels increasing surface roughness, ponding and infiltration. The aggregate stability for CG treatment was greater than that for CS and CSM and aggregate size peaks were identified at 5.4, 32,160 and 570 pm. Size peaks at 32 and 570 pm had the highest combined frequency (64%). Intra-event continuous monitoring covered silage plots with crop-rows oriented up-and-down the slope (CS) and along the contour (CScont). The crop-row orientation significantly influenced both runoff and sediment loss (concentration, load, size-distribution) patterns. The runoff volume and sediment concentration for CS was twice that of CScont. While no treatment difference attributable to residue coverage was evident for particle-size dynamics, crop-row orientation had a significant effect with finer-sized particles exported from the contoured site. Surface sealing, more pronounced at the silage sites, occurred after the 1st major storm in a season for all monitoring periods, types, and treatments, and it significantly influenced runoff generation, sediment load, and size distribution characteristics. Under crusted conditions, a storm with slightly higher rainfall depth but significant lower erosive potential, generated 53% more runoff and twice as much sediment compared to an early-season event. During crust development finer particles dominated sediment composition, later shifting to larger particles due to rill erosion once a stable crust was established. These results are expected to improve our understanding and, hence, predictive capability for transport of particulate-bound contaminants from row-crop systems, especially under conditions promoting surface crust formation. (c) 2008 Elsevier B.V. All rights reserved.
  • Authors:
    • Reddy, K. C.
    • Tazisong, I. A.
    • Nyakatawa, E. Z.
    • Senwo, Z. N.
    • Sainju, U. M.
  • Source: Journal of Environmental Quality
  • Volume: 37
  • Issue: 3
  • Year: 2008
  • Summary: Quantification of soil carbon (C) cycling as influenced by management practices is needed for C sequestration and soil quality improvement. We evaluated the 10-yr effects of tillage, cropping system, and N source on crop residue and soil C fractions at 0-to 20-cm depth in Decatur silt loam (clayey, kaolinitic, thermic, Typic Paleudults) in northern Alabama, USA. Treatments were incomplete factorial combinations of three tillage practices (no-till [NT], mulch till [MT], and conventional till [CT]), two cropping systems (cotton [Gossypium hirsutum L.]-cotton-corn [Zea mays L.] and rye [Secale cereale L.]/cotton-rye/cotton-corn), and two N fertilization sources and rates (0 and 100 kg N ha(-1) from NH4NO3 and 100 and 200 kg N ha(-1) from poultry litter). Carbon fractions weresoil organic C (SOC), particulate organic C (POC), microbial biomass C (MBC), and potential C mineralization (PCM). Crop residue varied among treatments and years and total residue from 1997 to 2005 was greater in rye/cottoil-rye/cotton-corn than in cotton-cotton-corn and greater with NH4NO3 than with poultry litter at 100 kg N ha(-1). The SOC content at 0 to 20 cm, after 10 yr was greater with poultry litter than with NH4NO3 in NT and CT, resulting in a C sequestration rate of 510 kg C ha(-1) yr(-1) with poultry litter compared with -120 to 147 kg C ha(-1) yr(-1) with NH4NO3. Poultry litter also increased PCM and MBC compared with NH4NO3. Cropping increased SOC, POC, and PCM compared with fallow in NT Long-term poultry litter application or continuous cropping increased soil C storage and microbial biomass and activity compared with inorganic N fertilization or fallow, indicating that these management practices can sequester C, offset atmospheric CO2 levels, and improve soil and environmental quality.
  • Authors:
    • Cassman, K. G.
    • Specht, J. E.
    • Weiss, A.
    • Setiyono, T. D.
    • Dobermann, A.
  • Source: Field Crops Research
  • Volume: 108
  • Issue: 1
  • Year: 2008
  • Summary: Different approaches have been used to simulate leaf area index (LAI) in soybean ( Glycine max L. Merr). Many of these approaches require genotype-specific calibration procedures. Studies modeling LAI dynamics under optimal growth conditions with yields close to the yield potential of soybean have remained scarce. A sink-driven approach was developed and evaluated for LAI simulation in soybean under near-optimal environments. The rate of change in expanding leaf area was simulated using the first derivative of a logistic function accounting for plant population density, air temperature, and water deficit. The rate of change in senescing leaf area was also simulated using the first derivative of a logistic function, assuming monocarpic senescence that began at the flowering stage (R1). Phenology was simulated as a function of temperature and photoperiod. Data for model development and evaluation were obtained from irrigated field experiments conducted at two locations in Nebraska, where agronomic management was optimized to achieve growth at a near yield potential level. LAI simulation with the proposed model had average RMSE of 0.52 m 2 m -2 for independent data at the two locations. The proposed model has minimum input requirements. Interactions between leaf growth and source-driven processes can be incorporated in the future, while maintaining the basic physiological assumptions underlining leaf expansion and senescence.