• Authors:
    • Haeberli, M.
    • Keiser, A.
    • Stamp, P.
  • Source: Field Crops Research
  • Volume: 128
  • Year: 2012
  • Summary: Today over 90% of the potatoes for the fresh market are washed; therefore consumers already object to minor external quality deficiencies. The quality assessment performed by potato traders does not distinguish in detail between quality deficiencies and potential links to the farming systems and site parameters are unknown. Thus, the cause for the observed increase of external quality problems is unknown. From 2001 to 2003 the extent and the potential causes of quality deficiencies were studied on totally 278 fields on conventional, integrated and organic farms in the wet and cool climate of Switzerland. Just before harvest samples consisting of 810 tubers were collected on each field in a standardised sampling pattern. Wireworms, slugs and drycore were responsible for important economic losses in all farming systems. In the organic farming system the quality damage was higher for all three deficiencies. While wireworm and slug damage were of general importance, drycore was significantly most severe in the organic farming system in all three years. Crass clover ley in the years preceding potatoes increased the risk for all three quality deficiencies. Slug damage increased with soil cover (catch crops) and with the percentage of crops favourable to slugs in the crop rotation (e.g. vegetables). Seed tubers without black scurf infestation reduced the occurrence of black scurf and drycore on harvested tubers. Fungicide seed treatment reduced black scurf significantly if seed tubers were infested. Insecticide seed treatment for cereals preceding potatoes as well as molluscicide treatments in the potato crop had a beneficial but not always sufficient effect. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Brainard, D.
  • Source: Acta Horticulturae
  • Issue: 950
  • Year: 2012
  • Summary: In response to declines in yield and stand longevity, Michigan asparagus growers are experimenting with multiple cultural practices including irrigation, shallow tillage, and "living-mulches" sown immediately following harvest in late June. Drought stress may play an important role in limiting fern growth and increasing fern susceptibility to pests. Living mulches are thought to reduce soil degradation and suppress weeds, but may also suppress asparagus through competition for water. Research was initiated in Hart, Michigan, USA, in 2008 with the following long-term objectives: (1) to evaluate the effects of irrigation on asparagus yields and weed management under two cropping systems; and (2) to determine the effects of cereal rye ( Secale cereal) living-mulch on soil moisture, weed growth, and asparagus yield. In a research farm field experiment, 4 treatments were examined: (1) no-till with standard herbicides; (2) no-till with standard herbicides plus irrigation; (3) shallow-tillage with rye living-mulch; (4) shallow tillage with rye living-mulch plus irrigation. Irrigation increased weed density and weed dry weight but had no detectable effect on asparagus yields. Rye living mulch (1) reduced soil volumetric water content by approximately 2-3% at 60 cm; (2) suppressed weeds compared to weedy control treatments, but resulted in increased weed density and dry weight compared to conventional herbicide treatments; and (3) had no detectable effect on asparagus yield.
  • Authors:
    • Noyes, D. C.
    • Bakker, J.
    • Brainard, D. C.
    • Myers, N.
  • Source: HortScience
  • Volume: 47
  • Issue: 1
  • Year: 2012
  • Summary: Living mulches growing below asparagus ( Asparagus officinales) fern can improve soil health and suppress weeds but may also suppress asparagus through competition for water or nutrients. The central objective of this research was to test whether cereal rye ( Secale cereale) living mulch, in combination with overhead irrigation, could provide comparable weed suppression to standard residual herbicides without reducing asparagus yields. A field experiment was conducted from 2008 to 2010 in a mature asparagus planting on sandy soils in western Michigan to evaluate the effects of irrigation (none vs. overhead) and weed management systems (standard herbicides vs. rye living mulch) on weed suppression, soil moisture content, and asparagus yield. Rye living mulch and herbicide treatments were established immediately after asparagus harvest in late June of each year. Rye living mulch reduced soil-available water in early August by 26% to 52% compared with herbicide treatments but had no detectable effect on asparagus yields. Compared with herbicide treatments, rye living mulch reduced fall-germinating weed emergence and resulted in lower densities of horseweed ( Conyza canadensis) during asparagus harvest. However, in 2 of 3 years, the living mulch system resulted in higher densities of summer annual weeds - including Powell amaranth ( Amaranthus powellii) and longspine sandbur ( Cenchrus longispinus) - during the fern growth period compared with herbicide treatments. After 3 years, the density of summer annual weeds was more than 10-fold greater in rye living mulch treatments compared with standard residual herbicides treatments. Our results suggest that (1) soil-improving rye cover crops can partially suppress weeds but may also compete with asparagus for soil moisture in dry years unless irrigation is used; and (2) successful use of rye living mulches for weed management will depend on identification of complementary weed management practices to avoid build-up of the summer annual weed seedbank.
  • Authors:
    • Connell, T.
    • Knuteson, D. L.
    • MacGuidwin, A. E.
    • Bland, W. L.
    • Bartelt, K. D.
  • Source: Phytopathology
  • Volume: 102
  • Issue: 5
  • Year: 2012
  • Summary: We used cover crops with demonstrated efficacy against Verticillium dahliae and Pratylenchus penetrans in combination with the biocidal practice of solarization to determine the importance of targeting both organisms for managing potato early dying, an issue relevant to the search for alternatives to soil fumigation. Two experiments were conducted in commercial fields using a split-plot design with cover crop treatments of rapeseed, marigold, forage pearl millet, sorghum-sudangrass, and corn as the main plot factor and solarization as the subplot factor. Cover crops were grown and solarization applied in year one, followed by potato in year two. The main effect of solarization was significant for reduced inoculum levels of both organisms in year two and increased tuber yields. The main effect of cover crop was also significant with lower population densities of P. penetrans following the marigold and millet treatments and of V. dahliae following rape and sorghum-sudangrass. The cover crop treatments influenced yield in only one of the experiments in the absence of solarization. The combinatorial effect of cover crops and solarization resulted in a wide range of pathogen population densities. Mean soil inoculum levels were negatively related to yield for V. dahliae in experiment 1, and for P. penetrans and the P. penetrans x V. dahliae interaction in both experiments.
  • Authors:
    • Van Remortel, R.
    • Smith, E.
    • Mehaffey, M.
  • Source: Ecological Applications
  • Volume: 22
  • Issue: 1
  • Year: 2012
  • Summary: Meeting future biofuel targets set by the 2007 Energy Independence and Security Act (EISA) will require a substantial increase in production of corn. The Midwest, which has the highest overall crop production capacity, is likely to bear the brunt of the biofuel-driven changes. In this paper, we set forth a method for developing a possible future landscape and evaluate changes in practices and production between base year (BY) 2001 and biofuel target (BT) 2020. In our BT 2020 Midwest landscape, a total of 25 million acres (1 acre = 0.40 ha) of farmland was converted from rotational cropping to continuous corn. Several states across the Midwest had watersheds where continuous corn planting increased by more than 50%. The output from the Center for Agriculture and Rural Development (CARD) econometric model predicted that corn grain production would double. In our study we were able to get within 2% of this expected corn production. The greatest increases in corn production were in the Corn Belt as a result of conversion to continuous corn planting. In addition to changes to cropping practices as a result of biofuel initiatives we also found that urban growth would result in a loss of over 7 million acres of productive farmland by 2020. We demonstrate a method which successfully combines economic model output with gridded land cover data to create a spatially explicit detailed classification of the landscape across the Midwest. Understanding where changes are likely to take place on the landscape will enable the evaluation of trade-offs between economic benefits and ecosystem services allowing proactive conservation and sustainable production for human well-being into the future.
  • Authors:
    • Monk, Wendy A.
    • Baird, Donald J.
    • Peters, Daniel L.
    • Armanini, David G.
  • Source: Journal of Environmental Quality
  • Volume: 41
  • Issue: 1
  • Year: 2012
  • Summary: Agricultural land use can place heavy demands on regional water resources, strongly influencing the quantity and timing of water flows needed to sustain natural ecosystems. The effects of agricultural practices on streamflow conditions are multifaceted, as they also contribute to the severity of impacts arising from other stressors within the river ecosystem. Thus, river scientists need to determine the quantity of water required to sustain important aquatic ecosystem components and ecological services, to support wise apportionment of water for agricultural use. It is now apparent that arbitrarily defined minimum flows are inadequate for this task because the complex habitat requirements of the biota, which underpin the structure and function of a river ecosystem, are strongly influenced by predictable temporal variations in flow. We present an alternative framework for establishing a first-level, regional ecological instream flow needs standard based on adoption of the Indicators of Hydrologic Alteration/Range of Variability Approach as a broadly applicable hydrological assessment tool, coupling this to the Canadian Ecological Flow Index which assesses ecological responses to hydrological alteration. By explicitly incorporating a new field-based ecological assessment tool for small agricultural streams, we provide a necessary verification of altered hydrology that is broadly applicable within Canada and essential to ensure the continuous feedback between the application of flow management criteria and ecological condition.
  • Authors:
    • Larsen, S. E.
    • Kristensen, K.
    • Elsgard, L.
    • Blicher-Mathiesen, G.
    • Schäfer, C. -M
    • Hoffmann, C. C.
    • Petersen, S. O.
    • Torp, S. B.
    • Greve, M. H.
  • Source: Biogeosciences
  • Volume: 9
  • Issue: 1
  • Year: 2012
  • Summary: The use of organic soils by agriculture involves drainage and tillage, and the resulting increase in C and N turnover can significantly affect their greenhouse gas balance. This study estimated annual fluxes of CH4 and N2O, and ecosystem respiration (R-eco), from eight organic soils managed by agriculture. The sites were located in three regions representing different landscape types and climatic conditions, and three land use categories were covered (arable crops, AR, grass in rotation, RG, and permanent grass, PG). The normal management at each site was followed, except that no N inputs occurred during the monitoring period from August 2008 to October 2009. The stratified sampling strategy further included six sampling points in three blocks at each site. Environmental variables (precipitation, PAR, air and soil temperature, soil moisture, groundwater level) were monitored continuously and during sampling campaigns, where also groundwater samples were taken for analysis. Gaseous fluxes were monitored on a three-weekly basis, giving 51, 49 and 38 field campaigns for land use categories AR, PG and RG, respectively. Climatic conditions in each region during monitoring were representative as compared to 20-yr averages. Peat layers were shallow, typically 0.5 to 1 m, and with a pH of 4 to 5. At six sites annual emissions of N2O were in the range 3 to 24 kg N2O-N ha(-1), but at two arable sites (spring barley, potato) net emissions of 38 and 61 kg N2O-N ha(-1) were recorded. The two high-emitting sites were characterized by fluctuating groundwater, low soil pH and elevated groundwater SO42- concentrations. Annual fluxes of CH4 were generally small, as expected, ranging from 2 to 4 kg CH4 ha(-1). However, two permanent grasslands had tussocks of Juncus effusus L. (soft rush) in sampling points that were consistent sources of CH4 throughout the year. Emission factors for organic soils in rotation and with permanent grass, respectively, were estimated to be 0.011 and 0.47 gm(-2) for CH4, and 2.5 and 0.5 gm(-2) for N2O. This first documentation of CH4 and N2O emissions from managed organic soils in Denmark confirms the levels and wide ranges of emissions previously reported for the Nordic countries. However, the stratified experimental design also identified links between gaseous emissions and site-specific conditions with respect to soil, groundwater and vegetation which point to areas of future research that may account for part of the variability and hence lead to improved emission factors or models.
  • Authors:
    • Prasuhn, V.
  • Source: Soil & Tillage Research
  • Volume: 120
  • Year: 2012
  • Summary: The positive effects of soil conserving farming methods have mostly been demonstrated using small test plots. The present study is aimed at confirming that they also occur on the catchment scale. The impact of crops and soil tillage practises on the extent of soil erosion was determined in 203 crop fields over 10 years in the Swiss Midlands. Soil erosion totalled 1969 t or 0.75 t ha(-1) yr(-1). Most erosion took place in winter wheat fields (33%), which accounted for 22% of the crop area. Second and third most erosion was observed in potato (26%) and fallow (14%) fields. By far the highest mean soil loss was found for potatoes, at 2.87 t ha(-1) yr(-1). Fallow (1.06 t ha(-1) yr(-1)) and winter wheat (1.05 t ha(-1) yr(-1)) fields were also relatively susceptible to soil erosion. In contrast, values for soil loss below mean were observed for maize (0.44 t ha(-1) yr(-1)), sugar beet (0.27 t ha(-1) yr(-1)), and rape seed (0.39 t ha(-1) yr(-1)). 88% of soil erosion took place on plough tilled land (PT), 9% on non-ploughed land with less than 30% surface residue cover (RT), 1% on mulch-tilled land with more than 30% surface residue cover (MT), and 2% in non-tilled or strip-tilled land with >30% soil cover (NT). At 0.07 and 0.12 t ha(-1) yr(-1), respectively, the mean soil loss in MT and NT fields was more than an order of magnitude lower than that under PT (1.24 t ha(-1) yr(-1)). Field mappings confirmed the positive effects of the soil conserving soil tillage practises. The risk of soil erosion was significantly influenced by crop rotation. The carry-over effects should be taken into account when studying the effects of cropping methods on soil erosion. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Mazza, G.
    • Pronyk, C.
  • Source: Bioresource Technology
  • Volume: 106
  • Year: 2012
  • Summary: Five cereal (triticale, durum wheat, CPS wheat, feed barley, oats) and two oilseed (canola, mustard) straws were fractionated with pressurized low polarity water in a flow-through reactor at 165 degrees C with a flow rate of 115 mL/min and a solvent-to-solid ratio of 60 mL/g. The conversion and extraction of the major carbohydrates and lignin from the reactor system during hydrothermal treatment was largely completed within the first 20-30 min. Glucan content of all straws were enriched by the process. More. than 90% of the xylan and nearly 50% of the lignin were extracted and there was no effect on yield due to crop species. However, there were differences in solid residue and liquid extract composition. Cereal crops yielded a residue richer in glucan and lower in lignin. Oilseed crop residues contained very low levels of ash. Xylo-oligosaccharides from oilseed crops contain more acetyl and uronic acid substituents. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.
  • Authors:
    • Netland, J.
    • Brandsaeter, L. O.
    • Sjursen, H.
  • Source: Acta Agriculturae Scandinavica, Section B - Soil & Plant Science
  • Volume: 62
  • Issue: 2
  • Year: 2012
  • Summary: Cover crops can be used to reduce leaching and erosion, introduce variability into crop rotation and fix nitrogen (N) for use by the main crops, less is however known about effects on weeds. The effects on weed seed bank, weed growth and grain yield of 4 years of annual undersown clover and ryegrass alone and in combination, and one of the 4 years with clover or clover + grass as green manure, were studied in oat and spring wheat at two experimental sites in south-eastern Norway. These treatments were compared with no undersown crop (control) and with weed harrowing. In contrast to many results in the literature, the undersown clover in this study did not suppress annual weeds, but fertilized the weeds as well as the cereals. Undersown clover resulted in a statistically significant increase of grain yield at the two sites to 116% and 121% of control. During the 4-year period relative seed bank and density of emerged weed (dominated by Spergula arvensis) increased significantly about 4.5 and 10 times respectively in the undersown clover plots at Apelsvoll. At Kise both ryegrass alone and ryegrass mixed with clover significantly suppressed the weed biomass to 70% and 74% of control respectively. It is concluded that fertilization effects of undersown clover may have dominated and overriden the competitive effects. One whole-season clover green manure did not increase the mean yield, but resulted in a significant drop in seed bank size the following year, because of limited weed establishment in an established ley. Only a slight increase in average weed biomass was observed at one of the two experimental sites. The weed seed bank and the weed biomass were essentially kept at steady state during the experimental period in harrowed plots, but harrowing decreased grain yield significantly at both sites.