• Authors:
    • Ediriwickrema, J.
    • Shao, Y.
    • Lunetta, R. S.
    • Lyon, J. G.
  • Source: International Journal of Applied Earth Observation and Geoinformation
  • Volume: 12
  • Issue: 2
  • Year: 2010
  • Summary: The Moderate Resolution Imaging Spectrometer (MODIS) Normalized Difference Vegetation Index (NDVI) 16-day composite data product (MOD12Q) was used to develop annual cropland and crop-specific map products (corn, soybeans, and wheat) for the Laurentian Great Lakes Basin (GLB). The crop area distributions and changes in crop rotations were characterized by comparing annual crop map products for 2005, 2006, and 2007. The total acreages for corn and soybeans were relatively balanced for calendar years 2005 (31,462 km(2) and 31,283 km(2), respectively) and 2006 (30,766 km(2) and 30,972 km(2), respectively). Conversely, corn acreage increased approximately 21% from 2006 to 2007, while soybean and wheat acreage decreased approximately 9% and 21%, respectively. Two-year crop rotational change analyses were conducted for the 2005-2006 and 2006-2007 time periods. The large increase in corn acreages for 2007 introduced crop rotation changes across the GLB. Compared to 2005-2006, crop rotation patterns for 2006-2007 resulted in increased corn-corn, soybean-corn, and wheat-corn rotations. The increased corn acreages could have potential negative impacts on nutrient loadings, pesticide exposures, and sediment-mediated habitat degradation. Increased in US corn acreages in 2007 were related to new biofuel mandates, while Canadian increases were attributed to higher world-wide corn prices. Additional study is needed to determine the potential impacts of increases in corn-based ethanol agricultural production on watershed ecosystems and receiving waters. Published by Elsevier B.V.
  • Authors:
    • Bellaloui, N.
    • Smith, J. R.
    • Mengistu, A.
    • Paris, R. L.
    • Wrather, J. A.
  • Source: Crop Science
  • Volume: 50
  • Issue: 5
  • Year: 2010
  • Summary: Phomopsis seed decay (PSD) of soybean ( Glycine max L. Merr) is primarily caused by Phomopsis longicolla. Currently, percent seed infection is used as a method for evaluating resistance to PSD. However, researchers need a common system for classifying soybean genotypes for their reaction to P. longicolla that is consistent across environments. The purpose of this research was: (i) to evaluate the reaction of a select set of soybean accessions to P. longicolla, and (ii) determine the effects of irrigation and two harvest regimes (normal and delayed) on seed infection. We propose a classification system for comparing reactions to P. longicolla among accessions based on a Phomopsis seed infection index (PSII), derived by dividing the percent seed infection of each accession by percent seed infection values of susceptible standards selected within early and late maturity groups. Percent seed infection by P. longicolla infection was greater when accessions were irrigated during the growing season and harvested at normal maturity. Some lines such as MO/PSD-0259 were rated as resistant to P. longicolla (7% seed infection) when not irrigated and harvested at maturity, but were rated as susceptible (39% seed infection) with irrigation and delayed harvest. The resistance ratings to P. longicolla using percent seed infection and PSII varied among accessions. SS93-6012, for example, had similar ratings for both (9% seed infection and 16% PSII). PI 416942 exhibited some resistance to P. longicolla based on percent seed infection (8%), but no resistance based on PSII (32%). Accessions PI 594478, Delmar, SS93-6012, SS93-6181, PI 594603A, and PI 594712 were classified by PSII as moderately resistant under irrigation and with delayed harvest. These results indicate that simple comparisons of percent seed infection among accessions without irrigation, without delayed harvest, and without a standard control of a similar maturity group might result in false conclusions about resistance to P. longicolla.
  • Authors:
    • Vigil, M. F.
    • Benjamin, J. G.
    • Mikha, M. M.
    • Nielson, D. C.
  • Source: Soil Science Society of America journal
  • Volume: 74
  • Issue: 5
  • Year: 2010
  • Summary: The predominant cropping system in the Central Great Plains is conventional tillage (CT) winter wheat ( Triticum aestivum L.)-summer fallow. We investigated the effect of 15 yr of cropping intensities, fallow frequencies, and tillage (CT and no-till [NT]) practices on soil organic C (SOC) sequestration, particulate organic matter (POM), and wet aggregate-size distribution. A crop rotation study was initiated in 1990 at Akron, CO, on a silt loam. In 2005, soil samples were collected from the 0- to 5- and 5- to 15-cm depths in permanent grass, native prairie, and cropping intensities (CI) that included winter wheat, corn ( Zea mays L.), proso millet ( Panicum miliaceum L.), dry pea ( Pisum sativum L.), and summer fallow. The native prairie was sampled to provide a reference point for changes in soil parameters. The most intensive crop rotation significantly increased C sequestration compared with the other CIs where fallow occurred once every 2 or 3 yr. Legume presence in the rotation did not improve SOC sequestration relative to summer fallow. Significant amounts of macroaggregates were associated with grass and intensive cropping compared with the rotations that included fallow. Reduced fallow frequency and continuous cropping significantly increased soil POM near the surface compared with NT wheat-fallow. Macroaggregates exhibited a significant positive relationship with SOC and POM. A significant negative correlation was observed between microaggregates and POM, especially at 0- to 5-cm depth. Overall, a positive effect of continuous cropping and NT was observed on macroaggregate formation and stabilization as well as SOC and POM.
  • Authors:
    • Lang, J. M.
    • Ebelhar, S. A.
    • Olson, K. R.
  • Source: Soil Science
  • Volume: 175
  • Issue: 2
  • Year: 2010
  • Summary: An 8-year cover crop study was conducted in southern Illinois to evaluate the effects of conservation tillage systems on corn and soybean yields and for the maintenance and restoration of soil organic carbon (SOC) and soil productivity of previously eroded soils. In 2001, the no-till (NT), chisel plow, and moldboard plow (MP) treatment plots, which were replicated six times in a Latin square design, were split (with cover crop and without) on sloping, moderately well-drained, moderately eroded soil. The average corn and average soybean yields were similar for NT, chisel plow, and MP systems with and without cover crops. By 2009, the tillage zone, subsoil, and rooting zone of all treatments had similar SOC on a volume basis for the cover crop treatments as for the same tillage treatment without a cover crop. However, using the baseline 2000 SOC contents only, the NT with cover crops maintained most of the SOC levels in the topsoil and subsoil during the 8-year study, when the sediment was high in SOC and retained in the upland landscape by soil conservation practices, including border and filter strips and sod waterways adjacent to the plots, with and without cover crops. Soil carbon creation retention in the upland landscape was greatest for the MP treatments when sediments were retained by the soil conservation practices, which should reduce soil erosion and sediment rich in SOC being transported by overland flow into water and the eventual release of methane and carbon dioxide to the atmosphere.
  • Authors:
    • Bengtson, L. E.
    • Fagre, D.
    • Pederson, G.
    • Zeyuan, Q.
    • Prato, T.
    • Williams, J. R.
  • Source: Environmental Management
  • Volume: 45
  • Issue: 3
  • Year: 2010
  • Summary: Potential economic impacts of future climate change on crop enterprise net returns and annual net farm income (NFI) are evaluated for small and large representative farms in Flathead Valley in Northwest Montana. Crop enterprise net returns and NFI in an historical climate period (1960-2005) and future climate period (2006-2050) are compared when agricultural production systems (APSs) are adapted to future climate change. Climate conditions in the future climate period are based on the A1B, B1, and A2 CO(2) emission scenarios from the Intergovernmental Panel on Climate Change Fourth Assessment Report. Steps in the evaluation include: (1) specifying crop enterprises and APSs (i.e., combinations of crop enterprises) in consultation with locals producers; (2) simulating crop yields for two soils, crop prices, crop enterprises costs, and NFIs for APSs; (3) determining the dominant APS in the historical and future climate periods in terms of NFI; and (4) determining whether NFI for the dominant APS in the historical climate period is superior to NFI for the dominant APS in the future climate period. Crop yields are simulated using the Environmental/Policy Integrated Climate (EPIC) model and dominance comparisons for NFI are based on the stochastic efficiency with respect to a function (SERF) criterion. Probability distributions that best fit the EPIC-simulated crop yields are used to simulate 100 values for crop yields for the two soils in the historical and future climate periods. Best-fitting probability distributions for historical inflation-adjusted crop prices and specified triangular probability distributions for crop enterprise costs are used to simulate 100 values for crop prices and crop enterprise costs. Averaged over all crop enterprises, farm sizes, and soil types, simulated net return per ha averaged over all crop enterprises decreased 24% and simulated mean NFI for APSs decreased 57% between the historical and future climate periods. Although adapting APSs to future climate change is advantageous (i.e., NFI with adaptation is superior to NFI without adaptation based on SERF), in six of the nine cases in which adaptation is advantageous, NFI with adaptation in the future climate period is inferior to NFI in the historical climate period. Therefore, adaptation of APSs to future climate change in Flathead Valley is insufficient to offset the adverse impacts on NFI of such change.
  • Authors:
    • Arriaga, F. J.
    • Rogers, H. H.
    • Runion, G. B.
    • Prior, S. A.
  • Source: Journal of Environmental Quality
  • Volume: 39
  • Issue: 2
  • Year: 2010
  • Summary: Increasing atmospheric CO(2) concentration has led to concerns about potential effects on production agriculture. In the fall of 1997, a study was initiated to compare the response of two crop management systems (conventional tillage and no-tillage) to elevated CO(2). The study used a split-plot design replicated three times with two management systems as main plots and two atmospheric CO(2) levels (ambient and twice ambient) as split plots using open-top chambers on a Decatur silt learn soil (clayey, kaolinitic, thermic Rhodic Paleudults). The conventional system was a grain sorghum [Sorghum bicolor (L.) Moench.] and soybean (Glycine max (L.) Merr.] rotation with winter fallow and spring tillage practices. In the no-tillage system, sorghum and soybean were rotated, and three cover crops were used [crimson clover (Trifolium incarnatum L.), sunn hemp (Crotalaria juncea L.), and wheat (Triticum aestivum L.)]. Over multiple growing seasons, the effect of management and CO(2) concentration on leaf-level gas exchange during row crop (soybean in 1999, 2001, and 2003; sorghum in 2000, 2002, and 2004) reproductive growth were evaluated. Treatment effects were fairly consistent across years. In general, higher photosynthetic races were observed under CO(2) enrichment (more so with soybean) regardless of residue management practice. Elevated CO(2) led to decreases in stomatal conductance and transpiration, which resulted in increased water use efficiency. The effects of management system on gas exchange measurements were infrequently significant, as were interactions of CO(2) and management. These results Suggest that better soil moisture conservation and high rates of photosynthesis can occur in both tillage systems in CO(2)-enriched environments during reproductive growth.
  • Authors:
    • Helmers, M. J.
    • Qi, Z.
  • Source: Vadose Zone Journal
  • Volume: 9
  • Issue: 1
  • Year: 2010
  • Summary: Utilization of cereal rye (Secale cereale L. ssp. cereal) as a winter cover crop has potential benefits for subsurface drainage and NO(3) loss reduction. The objective of this study was to quantify the soil water balance components and impacts of a rye cover crop on subsurface drainage in central Iowa. Rye was planted in lysimeters in mid-October and terminated in early June in 3 yr and the lysimeters were left fallow during the summer months. Subsurface drainage water was generally pumped out weekly along with taking soil moisture measurements; however, multiple appreciable rain events in a given week required more frequent pumping. During May through July of the 3 yr, monthly subsurface drainage was significantly reduced by 21% when comparing the rye system to bare soil (P
  • Authors:
    • Wrather, A.
    • Shannon, G.
    • Stevens, G.
    • Rhine, M. D.
    • Sleper, D.
  • Source: Irrigation Science
  • Volume: 28
  • Issue: 2
  • Year: 2010
  • Summary: Furrow irrigating soybean prior to a large, unexpected rainfall event can reduce nitrogen fixation and crop yield. The objective of this study was to evaluate the tolerance of soybean cultivars to waterlogged alluvial soils. Five cultivars were selected, which showed a range of tolerances to excessive soil water. Flood duration and flood timing experiments were conducted on clay and silt loam soils. Main plots were flooding duration and flood timing and subplots were soybean cultivars. Most cultivars were able to withstand flooding for 48-96 h without crop injury. Cultivars flooded during the V5 growth stage suffered the least amount of yield loss. The greatest yield losses from flooding occurred at the R5 growth stage. Soybean yields from cultivars flooded at R5 were reduced by 20-39% compared to non-flooded checks. Pioneer 94B73 (cv.) had no significant change in yield from flooding for 192 h at any of the three growth stages, compared to non-flooded controls.
  • Authors:
    • Suyker, A. E.
    • Verma, S. B.
    • Gitelson, A. A.
    • Wardlow, B. D.
    • Sakamoto, T.
    • Arkebauer, T. J.
  • Source: Remote Sensing of Environment
  • Volume: 114
  • Issue: 10
  • Year: 2010
  • Summary: The crop developmental stage represents essential information for irrigation scheduling/fertilizer management, understanding seasonal ecosystem carbon dioxide (CO 2) exchange, and evaluating crop productivity. In this study, we devised an approach called the Two-Step Filtering (TSF) for detecting the phenological stages of maize and soybean from time-series Wide Dynamic Range Vegetation Index (WDRVI) data derived from Moderate Resolution Imaging Spectroradiometer (MODIS) 250-m observations. The TSF method consists of a Two-Step Filtering scheme that includes: (i) smoothing the temporal WDRVI data with a wavelet-based filter and (ii) deriving the optimum scaling parameters from shape-model fitting procedure. The date of key crop development stages are then estimated by using the optimum scaling parameters and an initial value of the specific phenological date on the shape model, which are preliminary defined in reference to ground-based crop growth stage observations. The shape model is a crop-specific WDRVI curve with typical seasonal features, which were defined by averaging smoothed, multi-year WDRVI profiles from MODIS 250-m data collected over irrigated maize and soybean study sites. In this study, the TSF method was applied to MODIS-derived WDRVI data over a 6-year period (2003 to 2008) for two irrigated sites and one rainfed site planted to either maize or soybean as part of the Carbon Sequestration Program (CSP) at the University of Nebraska-Lincoln. A comparison of satellite-based retrievals with ground-based crop growth stage observations collected by the CSP over the six growing seasons for these three sites showed that the TSF method can accurately estimate the date of four key phenological stages of maize (V2.5: early vegetative stage, R1: silking stage, R5: dent stage and R6: maturity) and soybean (V1: early vegetative stage, R5: beginning seed, R6: full seed and R7: beginning maturity). The root mean square error (RMSE) of phenological-stage estimation for maize ranged from 2.9 [R1] to 7.0 [R5] days and from 3.2 [R6] to 6.9 [R7] days for soybean, respectively. In addition, the TSF method was also applied for two years (2001 and 2002) over eastern Nebraska to test its ability to characterize the spatio-temporal patterns of these key phenological stages over a larger geographic area. The MODIS-derived crop phenological stage dates agreed well with the statistical crop progress data reported by the United State Department of Agriculture (USDA) National Agricultural Statistics Service (NASS) for eastern Nebraska's three crop agricultural statistic districts (ASDs). At the ASD-level, the RMSE of phenological-stage estimation ranged from 1.6 [R1] to 5.6 [R5] days for maize and from 2.5 [R7] to 5.3 [R5] days for soybean.
  • Authors:
    • Belina, K.
    • Baumgartner, K.
    • Steenwerth, K.
    • Veilleux, L.
  • Source: Weed Science
  • Volume: 58
  • Issue: 3
  • Year: 2010
  • Summary: This research compared effects of the weed control practice, soil cultivation, and the conventional practice, glyphosate application on weed seedbank, in a vineyard system. The experiment was conducted in a commercial wine-grape vineyard in the Napa Valley of northern California from 2003 to 2005. The annual treatments were "winter-spring glyphosate," "spring cultivation," "fall-spring cultivation," and "fall cultivation-spring glyphosate," and were applied "in-row," under the vine. Composition of the weed seedbank collected in 2002 before treatment establishment did not differ among treatments. After 3 yr of weed treatments, detrended correspondence analysis indicated that the composition of spring cultivation and winter-spring glyphosate tended to differ from each other, but the remaining two treatments showed little differentiation. As determined by linear discriminant analysis, the specific weed species were associated with seedbanks of certain treatments. These were Carolina geranium, annual bluegrass, brome grasses, California burclover, and scarlet pimpernel, which do not pose problems with regard to physical aspects of grape production. Although 'Zorro' rattail fescue was ubiquitous among treatments, its distribution between depths in the cultivated treatments indicated that tillage provided some homogenization of seedbank along the vertical soil profile. The seedlings from the seedbank study were not congruent with those measured aboveground in the field, suggesting that both treatment and microclimatic effects in the field may have influenced germination, and thus, aboveground composition.