• Authors:
    • Holou, R. A. Y.
    • Stevens, G.
  • Source: GCB (Global Change Biology) Bioenergy
  • Volume: 4
  • Issue: 3
  • Year: 2012
  • Summary: The objective of this research was to determine the optimum nitrogen fertilizer rate for producing sweet sorghum (a promising biofuel crop) juice, sugar, and bagasse on silt loam, sandy loam, and clay soils in Missouri. Seven nitrogen fertilization rates were applied, ranging from 0 to 134 kg N ha -1. Regardless of the soil and year, the juice content of sweet sorghum stalk averaged 68.8% by weight. The juice yield ranged from 15.2 to 71.1 m 3 ha -1. Soil and N rate significantly impacted the juice yield ( P
  • Authors:
    • Singer, J. W.
    • Moorman, T. B.
    • Parkin, T. B.
    • Jaynes, D. B.
    • Kaspar, T. C.
  • Source: Agricultural Water Management
  • Volume: 110
  • Year: 2012
  • Summary: Much of the NO3 in the riverine waters of the upper Mississippi River basin in the United States originates from agricultural land used for corn (Zea mays L) and soybean (Glycine max [L] Merr.) production. Cover crops grown between maturity and planting of these crops are one approach for reducing losses of NO3. In this experiment, we evaluated the effectiveness of oat (Avena sativa L.) and rye (Secale cereale L.) cover crops in reducing NO3 concentrations and loads in subsurface drainage water. The oat fall cover crop was broadcast seeded into living corn and soybean crops before harvest in late August or early September and was killed by cold temperatures in late November or early December The rye winter cover crop, which had already been used annually for four years, was planted with a grain drill after corn and soybean harvest, overwintered, grew again in the spring, and was killed with herbicides before main crop planting. These treatments were evaluated in subsurface-drained field plots with an automated system for measuring drainage flow and collecting proportional samples for analysis of NO3 concentrations from each plot. The rye winter cover crop significantly reduced drainage water NO3 concentrations by 48% over five years, but this was less than the 58% reduction observed in its first four years of use. The oat fall cover crop reduced NO3 concentrations by 26% or about half of the reduction of the rye cover crop. Neither cover crop significantly reduced cumulative drainage or nitrate loads because of variability in cumulative annual drainage among plots. Both oat and rye cover crops are viable management options for significantly reducing NO3 losses to surface waters from agricultural drainage systems used for corn and soybean production. Published by Elsevier B.V.
  • Authors:
    • Lawton-Rauh, A.
    • Agudelo, P.
    • Leach, M.
  • Source: Plant Disease
  • Volume: 96
  • Issue: 1
  • Year: 2012
  • Summary: Rotylenchulus reniformis is a highly variable nematode species and an economically important pest in many cotton fields across the southeastern United States. Rotation with resistant or poor host crops is a method for management of reniform nematode. We studied the effect of six planting schemes covering four 120-day planting cycles on the predominant genotype of R. reniformis. Rotations used were: (i) cotton to corn; (ii) susceptible soybean to corn; (iii) resistant soybean to cotton; (iv) corn to cotton; (v) continuous susceptible soybean; (vi) continuous cotton. After each 120-day cycle, amplified fragment length polymorphisms (AFLPs) produced from four primer pairs were used to determine the effect of crop rotation on the predominant genotype of reniform nematode. A total of 279 polymorphic bands were scored using four primer combinations. Distinct changes in genotype composition were observed following rotations with resistant soybean or corn. Rotations involving soybean (susceptible and resistant) had the greatest effect on population structure. The characterization of field population variability of reniform nematode and of population responses to host plants used in rotations can help extend the durability of resistant varieties and can help identify effective rotation schemes.
  • 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:
    • Thomashow, L. S.
    • Parejko, J. A.
    • Mavrodi, D. V.
    • Mavrodi, O. V.
    • Weller, D. M.
  • Source: Applied and Environmental Microbiology
  • Volume: 78
  • Issue: 9
  • Year: 2012
  • Summary: This work determined the impact of irrigation on the seasonal dynamics of populations of Pseudomonas spp. producing the antibiotics phenazine-1-carboxylic acid (Phz +) and 2,4-diacetylphloroglucinol (Phl +) in the rhizosphere of wheat grown in the low-precipitation zone (150 to 300 mm annually) of the Columbia Plateau of the Inland Pacific Northwest. Population sizes and plant colonization frequencies of Phz + and Phl +Pseudomonas spp. were determined in winter and spring wheat collected during the growing seasons from 2008 to 2009 from selected commercial dryland and irrigated fields in central Washington State. Only Phz + bacteria were detected on dryland winter wheat, with populations ranging from 4.8 to 6.3 log CFU g -1 of root and rhizosphere colonization frequencies of 67 to 100%. The ranges of population densities of Phl + and Phz +Pseudomonas spp. recovered from wheat grown under irrigation were similar, but 58 to 100% of root systems were colonized by Phl + bacteria whereas only 8 to 50% of plants harbored Phz + bacteria. In addition, Phz +Pseudomonas spp. were abundant in the rhizosphere of native plant species growing in nonirrigated areas adjacent to the sampled dryland wheat fields. This is the first report that documents the impact of irrigation on indigenous populations of two closely related groups of antibiotic-producing pseudomonads that coinhabit the rhizosphere of an economically important cereal crop. These results demonstrate how crop management practices can influence indigenous populations of antibiotic-producing pseudomonads with the capacity to suppress soilborne diseases of wheat.
  • 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:
    • Asebedo, R.
    • Ruiz-Diaz, D.
    • Mengel, D.
    • Maxwell, T.
  • Source: Better Crops with Plant Food
  • Volume: 96
  • Issue: 1
  • Year: 2012
  • Summary: Soybeans are not generally considered responsive to N fertilizer; however, there are some circumstances where this crop can benefit from addition of N. Kansas research performed several years ago and reported in this magazine showed the potential for soybean grain response to N fertilizer in high-yield irrigated conditions. This article looks at other conditions where N fertilizer can be beneficial in soybean production.
  • Authors:
    • Horwath, W. R.
    • Wroble, J. F.
    • Munk, D. S.
    • Wallender, W. W.
    • Singh, P. N.
    • Mitchell, J. P.
    • Hogan, P.
    • Roy, R.
    • Hanson, B. R.
  • Source: California Agriculture
  • Volume: 66
  • Issue: 2
  • Year: 2012
  • Summary: Reducing tillage and maintaining crop residues on the soil surface could improve the water use efficiency of California crop production. In two field studies comparing no-tillage with standard tillage operations (following wheat silage harvest and before corn seeding), we estimated that 0.89 and 0.97 inches more water was retained in the no-tillage soil than in the tilled soil. In three field studies on residue coverage, we recorded that about 0.56, 0.58 and 0.42 inches more water was retained in residue-covered soil than in bare soil following 6 to 7 days of overhead sprinkler irrigation. Assuming a seasonal crop evapotranspiration demand of 30 inches, coupling no-tillage with practices preserving high residues could reduce summer soil evaporative losses by about 4 inches (13%). However, practical factors, including the need for different equipment and management approaches, will need to be considered before adopting these practices.