• Authors:
    • Nichols, K. A.
    • Toro, M.
  • Source: Soil & Tillage Research
  • Volume: 111
  • Issue: 2
  • Year: 2011
  • Summary: Soil aggregate stability is a frequently used indicator of soil quality, but there is no standard methodology for assessing this indicator. Current methods generally measure only a portion of the soil or use either dry-sieved or wet-sieved aggregates. Our objective was to develop a whole soil stability index (WSSI) by combining data from dry aggregate size distribution and water-stable aggregation along with a 'quality' constant for each aggregate size class. The quality constant was based on the impact of aggregate size on soil quality indicators. Soil quality indicators can be loosely defined as those soil properties and processes that have the greatest sensitivity to changes in soil function. The WSSI was hypothesized to have a better relationship to the impacts of aboveground management than other soil aggregation indices such as a mean weight diameter (MWD), geometric mean diameter (GIVID), and the normalized stability index (NSI). Soil samples used in this study were collected from sites established on the same or similar soil types at the Northern Great Plains Research Laboratory in Mandan, ND. By utilizing dry aggregate size distribution, water-stable aggregation, and the quality constant, the WSSI detected differences in soil quality due to management (such as amount of disturbance, plant cover, and crop rotation) with the highest values occurring for the undisturbed, native range and the lowest values for conventional tillage, fallow treatments. The WSSI had the best relationship with management and is recommended as a standard measurement for soil aggregation. Published by Elsevier B.V.
  • Authors:
    • Odhiambo, L. O.
    • Irmak, S.
  • Source: Transactions of the American Society of Agricultural and Biological Engineers
  • Volume: 54
  • Issue: 3
  • Year: 2011
  • Summary: Estimation of actual evapotranspiration (ET), especially its partitioning into plant transpiration (T) and soil evaporation (E), in agricultural fields is important for effective soil water management and conservation and for understanding the interactions between ET, T and E with the management practices. Direct field measurements of ET, T, and E rates are difficult and costly; hence, mathematical models are used for estimating them. The objective of this study was to evaluate the practical applicability of the Shuttleworth-Wallace (S-W) model to estimate and partition ET in a subsurface drip-irrigated soybean ( Glycine max L. Merr.) field with partial residue cover. While its performance has been studied for various surfaces, the performance evaluation of the S-W model for such surface has not been carried out. An integrated approach of calculating bulk stomatal resistance (r sc) as a function of soil water content (theta i) was incorporated into the model to allow simulation of T over a range of theta i, and a residue decomposition function was introduced to account for surface residue decay over time to more accurately account for the actual residue cover in field conditions. The model performance was evaluated for different plant growth stages during the 2007 and 2008 growing seasons at the University of Nebraska-Lincoln, South Central Agricultural Laboratory near Clay Center, Nebraska. The sum of estimated T and E was compared to the bowen Ratio Energy Balance System (BREBS)-measured actual ET on a daily time-step. The model was able to capture the trends and magnitudes of measured ET, but its performance differed for various plant physiological growth stages. The root mean square difference (RMSD) values between the model-estimated and measured ET values for the growing season (day after emergence until physiological maturity) were 1.26 and 1.03 mm d -1 for 2007 and 2008, respectively. Best performance was observed during the mid-season during full canopy cover with a two-year average r 2 of 0.87, average RMSD of 0.94 mm d -1, and average mean biased error (MBE) of 0.30 mm d -1. Estimates for both initial and late season growth stages where E was dominant had the least agreement with BREBS measurements. The proportion of T and E in the estimated ET varied with growth stage. The S-W estimated seasonal total ET and BREBS measurements were equal in 2007 (S-W model ET=496 mm and BREBS ET=498 mm), and in 2008 the model underestimated by only 8.2% (S-W model ET=452 mm and BREBS ET=489 mm). While, in general, the model was successful in tracking the trends and magnitude of the BREBS-measured ET, further re-parameterization of the T module of the model can improve its accuracy to estimate ET, especially T, during the initial and late season (before full canopy cover and after physiological maturity) for a subsurface drip-irrigated soybean canopy. Other enhancements needed in the model for improved estimation of the E component include accurate determination of soil surface resistance coefficients and accounting for direct evaporation of intercepted rainfall on the canopy.
  • Authors:
    • Van Eerd, L. L.
    • Vyn, R. J.
    • Robinson, D. E.
    • O'Reilly, K. A.
  • Source: Weed Technology
  • Volume: 25
  • Issue: 3
  • Year: 2011
  • Summary: The effectiveness of cover crops as an alternative weed control strategy should be assessed as the demand for food and fiber grown under sustainable agricultural practices increases. This study assessed the effect of fall cover crops on weed populations in the fall and spring prior to sweet corn planting and during sweet corn growth. The experiment was a split-plot design in a pea cover-cover crop-sweet corn rotation with fall cover crop type as the main plot factor and presence or absence of weeds in the sweet corn as the split-plot factor. The cover crop treatments were a control with no cover crop (no-cover), oat, cereal rye (rye), oilseed radish (OSR), and oilseed radish with rye (OSR+rye). In the fall, at Ridgetown, weed biomass in the OSR treatments was 29 and 59 g m(-2) lower than in the no-cover and the cereal treatments, respectively. In the spring, OSR+rye and rye reduced weed biomass, density, and richness below the levels observed in the control at Bothwell. At Ridgetown in the spring, cover crops had no effect on weed populations. During the sweet corn season, weed populations and sweet corn yields were generally unaffected by the cover crops, provided OSR did not set viable seed. All cover crop treatments were as profitable as or more profitable than the no-cover treatment. At Bothwell profit margins were highest for oat at almost Can$600 ha(-1) higher than the no-cover treatment. At Ridgetown, compared with the no-cover treatment, OSR and OSR+rye profit margins were between Can$1,250 and Can$1,350 ha(-1) and between Can$682 and Can$835 ha(-1), respectively. Therefore, provided that OSR does not set viable seed, the cover crops tested are feasible and profitable options to include in sweet corn production and provide weed-suppression benefits.
  • Authors:
    • Roskamp, G. K.
    • Glassman, K. R.
    • Ortiz-Ribbing, L. M.
    • Hallett, S. G.
  • Source: Plant Disease
  • Volume: 95
  • Issue: 4
  • Year: 2011
  • Summary: Common waterhemp ( Amaranthus rudis) and pigweeds ( Amaranthus spp.) are troublesome weeds in many cropping systems and have evolved resistance to several herbicides. Field trials to further develop Microsphaeropsis amaranthi and Phomopsis amaranthicola as bioherbicides for control of waterhemp and pigweeds were conducted to test the effectiveness of these organisms in irrigated and nonirrigated pumpkin and soybean plots over 2 years at three locations in western Illinois. The bioherbicide was applied with lecithin and vegetable oil at 187 liters ha -1 in 2008 and 374 liters ha -1 in 2009. Treatments included spore suspensions of M. amaranthi and P. amaranthicola alone, a mixture of both organisms, and sequential treatments of the organisms with halosulfuron-methyl (Sandea Herbicide) in pumpkin or glyphosate (Roundup Original Max Herbicide) in soybean. Bioherbicide effectiveness was estimated at approximately 7 and 14 days after treatment, as disease incidence, disease severity, percent weed control, and weed biomass reduction. Significant reductions in weed biomass occurred in treatments with one or both of the fungal organisms, and potential exists to tank mix M. amaranthi with halosulfuron-methyl. Leaf surface moisture and air temperatures following application may account for inconsistencies in field results between year and locations. These fungal organisms show potential as bioherbicides for weeds in the genus Amaranthus.
  • Authors:
    • Bonta, J. V.
    • Owens, L. B.
    • Shipitalo, M. J.
    • Rogers, S.
  • Source: Journal of Environmental Quality
  • Volume: 40
  • Issue: 1
  • Year: 2011
  • Summary: Winter application of manure poses environmental risks. Seven continuous corn, instrumented watersheds (approximately 1 ha each) at the USDA-ARS North Appalachian Experimental Watershed research station near Coshocton, Ohio were used to evaluate the environmental impacts of winter manure application when using some of the Ohio Natural Resources Conservation Service recommendations. For 3 yr on frozen, sometimes snow-covered, ground in January or February, two watersheds received turkey litter, two received liquid swine manure, and three were control plots that received N fertilizer at planting (not manure). Manure was applied at an N rate for corn; the target level was 180 kg N ha(-1) with a 30-m setback from the application area to the bottom of each watershed. Four grassed plots (61 x 12 m) were used for beef slurry application (9.1 Mg ha(-1) wet weight); two plots had 61 x 12 m grassed filter areas below them, and two plots had 30 x 12 m filter areas. There were two control plots. Nutrient concentrations were sometimes high, especially in runoff soon after application. However, most events with high concentrations occurred with low flow volumes; therefore, transport was minimal. Applying manure at the N rate for crop needs resulted in excess application of P. Elevated P losses contributed to a greater potential of detrimental environmental impacts with P than with N. Filter strips reduced nutrient concentrations and transport, but the data were too limited to compare the effectiveness of the 30- and 61-m filter strips. Winter application of manure is not ideal, but by following prescribed guidelines, detrimental environmental impacts can be reduced.
  • Authors:
    • Shipitalo, M. J.
    • Owens, L. B.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 141
  • Issue: 1-2
  • Year: 2011
  • Summary: With the current emphasis on the role of carbon in the environment, agricultural systems and their impacts on the carbon cycle are important parts of the overall issue. Organic carbon lost to streams and rivers can promote bacterial production and microbial respiration of CO(2) to the atmosphere. Although pastures and grasslands are major land uses in the humid U.S., row crop agriculture has received most of the carbon research focus. The objective of this study at the North Appalachian Experimental Watershed near Coshocton, Ohio, was to assess organic carbon transported from a pasture system, particularly on a runoff event basis. A beef cow-calf herd rotationally grazed a paddock during the growing season and was fed hay in this paddock during the dormant season (November-April). Surface runoff and sediment loss was measured and sampled throughout the year from the small watershed in the paddock. Most of the sediment samples were collected during the dormant season. With continuous winter occupancy, the percent vegetative cover was often = 10 kg ha(-1) from the watershed in the winter feeding area. The largest 6 events carried nearly 50% of the total sediment and sediment-attached C lost during this period. Annual losses of sediment and sediment-C varied considerably but averaged 2642 and 140 kg ha(-1), respectively. There was no significant correlation between the amount of sediment transported during individual events and the C concentration on the associated sediment. The pasture sediments have a C enrichment ratio of 1.2-1.5 compared with the 0-2.5 cm soil layer. Pasture sediment-C concentrations were >2x the C concentrations on sediments from nearby row crop watersheds. Published by Elsevier B.V.
  • Authors:
    • Jauhiainen, L.
    • Peltonen-Sainio, P.
    • Hakala, K.
  • Source: The Journal of Agricultural Science
  • Volume: 149
  • Year: 2011
  • Summary: Global warming has accelerated in recent decades and the years 1995-2006 were the warmest ever recorded. Also, in Finland, the last decade has been exceptionally warm. Hence, this study examines how current field crop cultivars, adapted to northern long-day conditions and short growing seasons, have responded to the elevated temperatures, especially with regard to determination of yield potential and quality. These comparisons were carried out with spring and winter wheat (Triticum aestivum L.), oats (Avena sativa L.), barley (Hordeum vulgare L.), winter rye (Secale cereale L.), pea (Pisum sativum L.) and rapeseed (turnip rape, Brassica rapa L. and oilseed rape, B. napus L.). Long-term data sets of MTT Official Variety Trials and the Finnish Meteorological Institute were used to study crop responses to precipitation and elevated temperatures at different growth phases. The MTT data sets were also grouped into experiments that could be considered typical of the temperature conditions in the period 1971-2000 seasons (termed '1985' conditions) or typical of the period 2010-39 (termed '2025'). At elevated temperatures, yields generally declined in these relatively cool growing conditions of northern Europe, except for pea. Elevated temperatures tended to have negative effects both in the pre- and post-anthesis phases, but the response depended on species. The response was probably associated with reduced water availability, which limited yield determination, especially in early growth phases. For example, in spring cereals a decrease in early summer precipitation by 10 mm decreased yields by 45-75 kg/ha. As warmer conditions also typically hastened development and growth in such generally cool growing conditions of Finland, it is essential that breeding programmes produce cultivars that are less sensitive to elevated temperatures, which are likely to become more frequent in future.
  • Authors:
    • Jauhiainen, L.
    • Peltonen-Sainio, P.
    • Sadras, V. O.
  • Source: Field Crops Research
  • Volume: 124
  • Issue: 2
  • Year: 2011
  • Summary: In the northernmost European environments of Finland, large variability in the yield and quality of crops is a critical source of uncertainty for growers and end-users of grain. The aims of this study were (i) to quantify and compare the plasticity, i.e., cultivar responsiveness to environment, in yield of spring oat, spring wheat, six-row barley, two-row barley, winter rye, winter wheat, turnip rape and oilseed rape, (ii) to explore the existence of hierarchies or positive correlations in the plasticity of agronomic, yield and quality traits and (iii) to probe for trends in yield plasticity associated with different eras of breeding for yield potential and agronomic traits. Plasticities of yield, agronomic and quality traits were derived as slopes of norms of reaction using MTT Agrifood Research Finland data sets combining long-term (1970-2008 for cereals and 1976-2008 for rapeseed) results from 15 to 26 locations. Plasticity of yield ranged typically between 0.8 and 1.2, was smallest for six-row barley (0.84-1.11) and largest for winter rye (0.72-1.36). We found two types of associations between plasticity of yield and yield under stressful or favourable conditions for cereals but none for rape. In spring wheat, oat and six-row barley, high yield plasticity was associated with crop responsiveness to favourable conditions rather than yield reductions under stressful conditions. Modern spring wheat cultivars had higher maximum grain yields compared to older ones at the same level of plasticity. In winter wheat and rye, high yield plasticity resulted from the combination of high yield in favourable conditions and low yield in stressful environments. Many associations between yield plasticity and other traits were identified in cereals: e.g., high yield plasticity was often associated with higher grain weight, more grains per square meter, later maturity (contrary to turnip rape), shorter plants, less lodging and lower grain protein content and in winter cereals with higher winter damage. (C) 2011 Elsevier B.V. All rights reserved.
  • Authors:
    • Nonnecke, G. R.
    • Portz, D. N.
  • Source: HortScience
  • Volume: 46
  • Issue: 10
  • Year: 2011
  • Summary: Yield of strawberry grown continuously on the same site often declines over time as a result of proliferation of weed seeds and pathogenic organisms in the soil. Plots were established and maintained in seven different cover crops and as continuous strawberry or continuous tillage for 10 years (1996 to 2005) in a site that was previously in strawberry production for 10 years (1986 to 1995). Cover crops included blackeyed Susan (Rudbeckia hirta L.), sorghum Sudangrass [Sorghum bicolor (L.) Moench], marigold (Tagetes credo L.), big bluestem (Andropogon gerardii Vitman), perennial ryegrass (Lolium permute L.), switchgrass (Panicum virgatum L.), and Indiangrass [Sorghastrum nutans (L.) Nash]. Treatments were ended in 2005 and plots were planted with 'Honeoye' strawberry in a matted row. Effectiveness of soil pretreatments in reducing weed populations and enhancing strawberry production was evaluated for four growing seasons by quantifying weed growth by type and biomass and strawberry plant density and yield. The results indicate that matted-row strawberry production plots that were either in continuous tillage or established in S. bicolor, P. virgatum, or A. gerardii before planting strawberry had lower weed biomass and greater strawberry plant establishment and yield than plots established in L. permute or R. hirta or that had supported continuous strawberry production.
  • Authors:
    • Nichols, R. L.
    • Kelton, J. A.
    • Culpepper, S. A.
    • Balkcom, K. S.
    • Price, A. J.
    • Schomberg, H.
  • Source: Journal of Soil and Water Conservation
  • Volume: 66
  • Issue: 4
  • Year: 2011
  • Summary: Conservation tillage reduces the physical movement of soil to the minimum required for crop establishment and production. When consistently practiced as a soil and crop management system, it greatly reduces soil erosion and is recognized for the potential to improve soil quality and water conservation and plant available water. Adoption of conservation tillage increased dramatically with the advent of transgenic, glyphosate-resistant crops that permitted in-season, over-the-top use of glyphosate (N-[phosphonomethyl] glycine), a broad-spectrum herbicide with very low mammalian toxicity and minimal potential for off-site movement in soil or water. Glyphosate-resistant crops are currently grown on approximately 70 million ha (173 million ac) worldwide. The United States has the most hectares (45 million ha [99 million ac]) of transgenic, glyphosate-resistant cultivars and the greatest number of hectares (46 million ha [114 million ac]) in conservation tillage. The practice of conservation tillage is now threatened by the emergence and rapid spread of glyphosate-resistant Palmer amaranth (Amaranthus palmeri [S.]Wats.), one of several amaranths commonly called pigweeds. First identified in Georgia, it now has been reported in Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, and Tennessee. Another closely related dioecious amaranth, or pigweed, common waterhemp (Amaranthus rudis Sauer), has also developed resistance to glyphosate in Illinois, Iowa, Minnesota, and. Missouri. Hundreds of thousands of conservation tillage hectares, some currently under USDA Natural Resources Conservation Service conservation program contracts, are at risk of being converted to higher-intensity tillage systems due to the inability to control these glyphosate-resistant Amaranthus species in conservation tillage systems using traditional technologies. The decline of conservation tillage is inevitable without the development and rapid adoption of integrated, effective weed control strategies. Traditional and alternative weed control strategies, such as the utilization of crop and herbicide rotation and integration of high residue cereal cover crops, are necessary in order to sustain conservation tillage practices.