• Authors:
    • Liscano,J. F.
    • Boquet, D. J.
    • Breitenbeck, G. A.
    • Mascagni, H. J.,Jr.
    • Clawson, E. L.
    • McCarter, K. S.
  • Source: Journal of Plant Nutrition
  • Volume: 34
  • Issue: 6
  • Year: 2011
  • Summary: Soil nitrogen (N)-supplying capacity bioassays could present alternatives to traditional soil tests. Objectives were to identify winter crops and associated characteristics with bioassay potential. Saint Joseph and Bossier City, LA experiments used randomized complete block designs with factorial N fertilizer and winter crop treatment arrangements. Nitrogen rates were applied to corn (Zea mays L.) in 2004. Unfertilized winter wheat (Triticum aestivum L.), cereal rye (Secale cereale L.), native winter vegetation, and weed-free winter fallow treatments followed corn. At Saint Joseph, cotton (Gossypium hirsutum L.) followed winter crop treatments. Greater corn N rate consistently increased winter crop biomass and N accumulation, suggesting potential as bioassays, and increased Saint Joseph seedcotton yield. Winter crop-seedcotton yield N-response relationships were non-significant by familywise error rate criteria. However, some winter crop characteristics, such as rye N accumulation, for which a relationship to seedcotton yield closely approached significance, may merit further research as soil N-supplying capacity bioassays.
  • Authors:
    • Barnes, P. L.
    • Sheshukov, A. Y.
    • Douglas-Mankin, K. R.
    • Daggupati, P.
    • Devlin, D. L.
  • Source: Transactions of the ASABE
  • Volume: 54
  • Issue: 2
  • Year: 2011
  • Summary: Soil erosion from agricultural fields is a fundamental water quality and quantity concern throughout the U.S. Watershed models can help target general areas where soil conservation measures are needed, but they have been less effective at making field-level recommendations. The objectives of this study were to demonstrate a method of field-scale targeting using ArcSWAT and to assess the impact of topography, soil, land use, and land management source data on field-scale targeting results. The study was implemented in Black Kettle Creek watershed (7,818 ha) in south-central Kansas. An ArcGIS toolbar was developed to post-process SWAT hydrologic response unit (HRU) output to generate sediment yields for individual fields. The relative impact of each input data source on field-level targeting was assessed by comparing ranked lists of fields on the basis of modeled sediment-yield density (Mg ha -1) from each data-source scenario. Baseline data of field-reconnaissance land use and management were compared to NASS and NLCD data, 10 m DEM topography were compared to 30 m, and SSURGO soil data were compared to STATSGO. Misclassification of cropland as pasture by NASS and aggregation of all cropland types to a single category by NLCD led to as much as 75% and 82% disagreement, respectively, in fields identified as having the greatest sediment-yield densities. Neither NASS nor NLCD data include land management data (such as terraces, contour farming, or no-till), but such inclusion changed targeted fields by as much as 71%. Impacts of 10 m versus 30 m DEM topographic data and STATSGO versus SSURGO soil data altered the fields targeted as having the highest sediment-yield densities to a lesser extent (about 10% to 25%). SWAT results post-processed to field boundaries were demonstrated to be useful for field-scale targeting. However, use of incorrect source data directly translated into incorrect field-level sediment-yield ranking, and thus incorrect field targeting. Sensitivity was greatest for land use data source, followed closely by inclusion of land management practices, with less sensitivity to topographic and soil data sources.
  • Authors:
    • Paustian, K.
    • Ogle, S.
    • Lee, J.
    • De Gryze, S.
    • Six, J.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 144
  • Issue: 1
  • Year: 2011
  • Summary: We predicted changes in yields and direct net soil greenhouse gas (GHG) fluxes from converting conventional to alternative management practices across one of the world's most productive agricultural regions, the Central Valley of California, using the DAYCENT model. Alternative practices included conservation tillage, winter cover cropping, manure application, a 25% reduction in N fertilizer input and combinations of these. Alternative practices were evaluated for all unique combinations of crop rotation, climate, and soil types for the period 1997-2006. The crops included were alfalfa, corn, cotton, melon, safflower, sunflower, tomato, and wheat. Our predictions indicate that, adopting alternative management practices would decrease yields up to 5%. Changes in modeled SOC and net soil GHG fluxes corresponded to values reported in the literature. Average potential reductions of net soil GHG fluxes with alternative practices ranged from -0.7 to -3.3 Mg CO(2)-eq ha(-1) yr(-1) in the Sacramento Valley and -0.5 to -2.5 Mg CO(2)-eq ha(-1) yr(-1) for the San Joaquin Valley. While adopting a single alternative practice led to modest net soil GHG flux reductions (on average -1 Mg CO(2)-eq ha(-1) yr(-1)), combining two or more of these practices led to greater decreases in net soil GHG fluxes of up to -3 Mg CO(2)-eq ha(-1) yr(-1). At the regional scale, the combination of winter cover cropping with manure application was particularly efficient in reducing GHG emissions. However, GHG mitigation potentials were mostly non-permanent because 60-80% of the decreases in net soil GHG fluxes were attributed to increases in SOC, except for the reduced fertilizer input practice, where reductions were mainly attributed to decreased N(2)O emissions. In conclusion, there are long-term GHG mitigation potentials within agriculture, but spatial and temporal aggregation will be necessary to reduce uncertainties around GHG emission reductions and the delivery risk of the associated C credits. (C) 2011 Elsevier B.V. All rights reserved.
  • Authors:
    • Ebert, W.
    • Olson, R.
    • Demchik, M.
  • Source: Agroforestry: A Profitable Land Use. Proceedings of the 12th North American Agroforestry Conference, Athens, Georgia, USA, 4-9 June 2011
  • Year: 2011
  • Summary: In fall of 2006, a 2-acre hayfield on a tree farm in central Wisconsin was laid out into 10-foot wide terraces/swales along contour lines. The beds were strip sprayed with glyphosate and a two-bottom plow was used to create swales. A total of 2400 linear feet of planting bed were created. Each terrace was planted to 2-3 rows of plants, with trees on 20-ft spacing and shrubs interplanted at 5-8 foot spacing. This will create a multi-layer canopy with crops from each layer. Over 40 species/varieties were planted on the site in the spring of 2007 (240 trees, 480 shrubs, and 250 perennials). The entire site was electrically fenced. Plants were mulched with either wood chips or fabric mulch and treatments of drip-irrigation or no irrigation were applied to the plants. After three growing seasons, no difference was found between treatments. The swales and mulching was adequate to ensure survival and growth without the need of supplemental irrigation. Growth and fruiting of individual species as well as other observations will be discussed in this presentation.
  • Authors:
    • Tarkalson, D. D.
    • Shapiro, C. A.
    • Hergert, G. W.
    • Ferguson, R. B.
    • Wortmann, C. S.
    • Dobermann, A.
    • Walters, D. T.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 1
  • Year: 2011
  • Summary: Nitrogen management recommendations may change as yield levels and efficiency of crop production increase. The mean yield with nutrients applied in 32 irrigated corn ( Zea mays L.) trials conducted across Nebraska from 2002 to 2004 to evaluate crop response to split-applied N was 14.8 Mg ha -1 The mean economically optimal nitrogen rates (EONR) for irrigated corn varied with the fertilizer N/grain price ratio. At a fertilizer N/corn price ratio of 7 the EONR was 171, 122, and 93 kg ha -1, respectively, for cropping systems with corn following corn (CC), soybean [ Glycine max (L.) Merr.] (CS), and drybean ( Phaseolus vulgaris L.) (CD). At this price ratio the present University of Nebraska (UNL) recommendation procedure gave mean N recommendations that were 17.2 and 68.1 kg ha -1 higher than the mean EONR determined in this study for CC and CD, respectively, but essentially equal to mean EONR for CS. The UNL algorithm, adjusted for mean cropping system EONR gave more accurate prediction of site-year EONR than alternative N rate predictions for CC and CD with returns to applied nitrogen (RTN) of -$22 and -$13 ha -1 compared with measured site-year EONR. Prediction of site-year EONR using mean EONR adjusted for soil organic matter was more accurate for CS than other methods with an RTN of -$6 ha -1 compared with measured site-year EONR. Further research is needed to extend the results to: lower yield situations, alternatives to split application of N, and adjustment of EONR to protect against inadequate N in atypical seasons or for environmental protection.
  • Authors:
    • Fernandez, G. E.
    • Schroeder-Moreno, M. S.
    • Garland, B. C.
    • Creamer, N. G.
  • Source: HortScience
  • Volume: 46
  • Issue: 7
  • Year: 2011
  • Summary: The effects of eight summer cover crop treatments combined with two arbuscular mycorrhizal (AM) fungal inoculants on strawberry growth and yields were examined in a 2-year field experiment. Cover crop treatments included 1) sudangrass [Sorghum bicolor (L.) Moench cv. Piper]: 2) pearl millet [Pennisetum glaucum (L.) R.Br. CV. 102 M Hybrid!: 3) soybean [Glycine max (L.) Merrill cv. Laredo]: 4) velvetbean [Mucuna deeringiana (Bort) Merr. cv. Georgia Bush]: 5) sudangrass/velvetbean combination; 6) pearl millet/soybean combination; 7) a non-mycorrhizal host consisting of rape (Brassica napus L. var. napus cv. Dwarf Essex) and buckwheat (Fagopyrum esculentum Moench) in Year 1 and Year 2, respectively; and 8) no cover crop control. Strawberry tips were inoculated with either a native mixture of several AM fungal species or a single species sold commercially, Glomus intraradices. Cover crop treatments were assessed for their aboveground biomass and nutrient uptake as well as their impacts on weed abundance and diversity, soil nutrients, and parasitic nematode populations. Cover crop and AM treatments were assessed for their impact on strawberry growth, yields, AM root colonization, and nutrient uptake. Grass-based cover crop treatments, particularly pearl millet, produced the most aboveground biomass. In both years, all cover crop treatments reduced summer weed biomass compared with the control. Neither cover crop nor AM treatments had an effect on overall strawberry plant growth or yields in either year, although some differences existed at specific growth periods. The results suggest that cover crops are a viable strategy for reducing summertime weeds and that background, native populations of AM fungi in the soil may be just as effective as a commercially available species. It is likely that no overall yield benefit was found among treatments for two reasons: 1) nutrients, especially nitrogen, were not limiting; and 2) the cover crop growth window may have been too short for a significant impact on strawberries over two seasons.
  • Authors:
    • Huffman, R. L.
    • Grabow, G. L.
    • Evans, R. O.
  • Source: Journal of Irrigation and Drainage Engineering
  • Volume: 137
  • Issue: 1
  • Year: 2011
  • Summary: A subsurface drip irrigation (SDI) system was installed in the Piedmont of North Carolina in a clay soil in the fall of 2001 to test the effect of dripline spacing on corn and soybean yield. The system was zoned into three sections; each section was cropped to either corn ( Zea mays L.), full-season soybean [ Glycine max (L.) Merr.], or winter wheat ( Triticum aestivum) double cropped to soybean representing any year of a typical crop rotation in the region. Each section had four plots; two SDI plots with dripline spacing at either 1.52 or 2.28 m, an overhead sprinkler irrigated plot, and an unirrigated plot. There was no difference in average corn grain yield for 2002-2005 between dripline spacings or between either dripline spacing and sprinkler. Irrigation water use efficiency (IWUE) was greater for sprinkler irrigated corn than for either SDI treatment and there was no difference in IWUE in soybean. Water typically moved laterally from the driplines 0.38 to 0.50 m. SDI yield and IWUE increased relative to sprinkler yields and water use efficiency in the second and third year of the study. This may suggest that initial fracturing of the heavy clay soil during SDI system installation and subsequent settling of the soil affected water distribution.
  • Authors:
    • Burr, C.
    • Thorburn, J.
    • Irmak, S.
    • Yang, H. S.
    • Grassini, P.
    • Cassman, K. G.
  • Source: Field Crops Research
  • Volume: 120
  • Issue: 1
  • Year: 2011
  • Summary: Appropriate benchmarks for water productivity (WP), defined here as the amount of grain yield produced per unit of water supply, are needed to help identify and diagnose inefficiencies in crop production and water management in irrigated systems. Such analysis is lacking for maize in the Western U.S. Corn Belt where irrigated production represents 58% of total maize output. The objective of this paper was to quantify WP and identify opportunities to increase it in irrigated maize systems of central Nebraska. In the present study, a benchmark for maize WP was (i) developed from relationships between simulated yield and seasonal water supply (stored soil water and sowing-to-maturity rainfall plus irrigation) documented in a previous study; (ii) validated against actual data from crops grown with good management over a wide range of environments and water supply regimes ( n=123); and (iii) used to evaluate WP of farmer's fields in central Nebraska using a 3-y database (2005-2007) that included field-specific values for yield and applied irrigation ( n=777). The database was also used to quantify applied irrigation, irrigation water-use efficiency (IWUE; amount of yield produced per unit of applied irrigation), and the impact of agronomic practices on both parameters. Opportunities to improve irrigation management were evaluated using a maize simulation model in combination with actual weather records and detailed data on soil properties and crop management collected from a subset of fields ( n=123). The linear function derived from the relationship between simulated grain yield and seasonal water supply, namely the mean WP function (slope=19.3 kg ha -1 mm -1; x-intercept=100 mm), proved to be a robust benchmark for maize WP when compared with actual yield and water supply data. Average farmer's WP in central Nebraska was ~73% of the WP derived from the slope of the mean WP function. A substantial number of fields (55% of total) had water supply in excess of that required to achieve yield potential (900 mm). Pivot irrigation (instead of surface irrigation) and conservation tillage in fields under soybean-maize rotation had the greatest IWUE and yield. Applied irrigation was 41 and 20% less under pivot and conservation tillage than under surface irrigation and conventional tillage, respectively. Simulation analysis showed that up to 32% of the annual water volume allocated to irrigated maize in the region could be saved with little yield penalty, by switching current surface systems to pivot, improving irrigation schedules to be more synchronous with crop water requirements and, as a fine-tune option, adopting limited irrigation.
  • Authors:
    • Butts, C. L.
    • Sorensen, R. B.
    • Nuti, R. C.
  • Source: The Journal of Cotton Science
  • Volume: 15
  • Issue: 3
  • Year: 2011
  • Summary: Long-term cotton ( Gossypium hirsutum L.) yield with various irrigation rates and crop rotations, irrigated with subsurface drip irrigation (SSDI) is not known for the US Southeast. A SSDI system was installed in Southwest GA (1998) and maintained for 10 years. The soil is a Tifton loamy sand (Fine-loamy, kaolinitic, thermic Plinthic Kandiudults) and treatments consisted of three crop rotations, two drip tube lateral spacings, and three irrigation levels. Crop rotations were alternate year cotton (cotton-peanut; Arachis hypogeae L), two years (cotton-maize ( Zea mays L.) -peanut), and three years between cotton (cotton-maize-maize-peanut). Drip tube laterals were installed underneath each crop row and alternate crop row furrows. Cotton was not grown in 1999 and 2006. Crops were irrigated daily at 100, 75 and 50% of estimated crop water use. No lint yield difference resulted from crop rotation. Lint yield differences were attributed to irrigation treatments in 4 of 8 years. Lint yields were greatest at the 75% irrigation level compared to 50%, and in 3 out of 4 years compared to the 100% irrigation treatment. Higher lint yield with irrigation also coincided with lower seasonal rainfall totals. Drip tube lateral spacing affected lint yield 4 out of 8 years. Across all years, yield data indicates that alternate row furrow lateral spacing is as effective as every-row lateral spacing. Some fiber qualities were affected by irrigation, lateral, and rotation treatments, but these effects were small and inconsistent. Subsurface drip irrigation in the Southeast is optimal at the 75% irrigation level with tubing in alternate row furrows.
  • Authors:
    • Williams, J. D.
    • Long, D. S.
  • Source: Crop Management
  • Issue: March
  • Year: 2011
  • Summary: In the intermediate annual precipitation zone (14 to 18 inches) of northeastern Oregon, there is interest in increasing the intensity of cropping with spring crops. Mechanical tillage remains popular for seedbed preparation and weed control, but contributes to environmental problems and high labor and fuel cost. No-tillage (NT) crop production can reduce on site and off site problems and has lower labor and fuel costs, but soil-borne disease and weed control problems can limit yields. We compared crop yields, production costs, and economic returns of an intensive, four-year crop production rotation under two management systems: (i) minimum tillage (MT) with cultivation by chiseling, sweeping, and rod weeding; and (ii) NT with chemical weed control. The rotation was fallow-winter wheat-dry spring pea-winter wheat in which a spring broadleaf crop is included to aid in the control of winter annual weeds and reduce host pathogen levels of soil-borne cereal diseases. Four year averages of wheat yields in the NT treatment were equal to or greater than those in the MT treatment whereas dry green pea production was roughly equal in each treatment. Crop productivity differed significantly in each phase of the rotation in descending order from winter wheat following fallow [4,578 lb/acre (76 bu/acre)], winter wheat following dry spring pea [3,548 lb/acre (59 bu/acre)], to dry spring pea (1,505 lb/acre). Partial budget analysis shows that NT is substantially less costly than MT in terms of labor and fuel, potentially making NT economically viable for intensive cropping systems in the intermediate precipitation dryland region of northeastern Oregon.