• 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:
    • Rogers, D. J.
    • Brier, H. B.
  • Source: Crop Protection
  • Volume: 29
  • Issue: 1
  • Year: 2010
  • Summary: The response of vegetative soybean (Glycine max) to Helicoverpa armigera feeding was studied in irrigated field cages over three years in eastern Australia to determine the relationship between larval density and yield loss, and to develop economic injury levels. Rather than using artificial defoliation techniques, plants were infested with either eggs or larvae of H. armigera, and larvae allowed to feed until death or pupation. Larvae were counted and sized regularly and infestation intensity was calculated in Helicoverpa injury equivalent (HIE) units, where 1 HIE was the consumption of one larva from the start of the infestation period to pupation. In the two experiments where yield loss occurred, the upper threshold for zero yield loss was 7.510.21 HIEs and 6.431.08 HIEs respectively. In the third experiment, infestation intensity was lower and no loss of seed yield was detected up to 7.0 HIEs. The rate of yield loss/HIE beyond the zero yield loss threshold varied between Experiments 1 and 2 (-9.440.80 g and -23.173.18 g, respectively). H. armigera infestation also affected plant height and various yield components (including pod and seed numbers and seeds/pod) but did not affect seed size in any experiment. Leaf area loss of plants averaged 841 and 1025 cm 2/larva in the two experiments compared to 214 and 302 cm 2/larva for cohort larvae feeding on detached leaves at the same time, making clear that artificial defoliation techniques are unsuitable for determining H. armigera economic injury levels on vegetative soybean. Analysis of canopy leaf area and pod profiles indicated that leaf and pod loss occurred from the top of the plant downwards. However, there was an increase in pod numbers closer to the ground at higher pest densities as the plant attempted to compensate for damage. Defoliation at the damage threshold was 18.6 and 28.0% in Experiments 1 and 2, indicating that yield loss from H. armigera feeding occurred at much lower levels of defoliation than previously indicated by artificial defoliation studies. Based on these results, the economic injury level for H. armigera on vegetative soybean is approximately 7.3 HIEs/row-metre in 91 cm rows or 8.0 HIEs/m 2.
  • Authors:
    • Karp, A.
    • Riche, A.
    • Bohan, D. A.
    • Mallott, M. D.
    • Haughton, A. J.
    • Cunningham, M.
    • Sage, R.
  • Source: Ibis
  • Volume: 152
  • Issue: 3
  • Year: 2010
  • Summary: We compared birds in a group of established and well-managed miscanthus (Miscanthus x giganteus) fields in Somerset and East Devon, southwestern England, with plots of short rotation coppice (SRC) willow, arable crops and grassland in two winters and one summer. Following early spring cutting, 19 miscanthus fields grew taller, initially produced greater cover and were less weedy than SRC. As stubble in May, the miscanthus contained broadly similar species at similar densities to arable and grassland comparison plots. By July, at 2-m-tall, miscanthus held higher densities of birds but of fewer species, most of them characteristic of woodland and scrub. SRC, previously identified as being a beneficial crop for many birds, always contained more species and individuals than miscanthus. Throughout each of two winters, 15 miscanthus plots remained unharvested and contained more wood/scrub species such as Blackbirds Turdus merula, tits, Reed Buntings Emberiza schoeniclus and Woodcock Scolopax rusticola than the comparison plots, which held more corvids and Skylarks Alauda arvensis amongst others. Similar overall mean densities of birds in the miscanthus and the comparison plots masked relatively low density variance in miscanthus and very high variance in the comparison plots. Unharvested miscanthus crops grown in place of habitat types supporting flocks of wintering birds would displace these flocks. Miscanthus plantations with open patches attracted more finches and waders in winter. The two previous studies of birds in miscanthus in the UK found more species and more individuals than we did in summer and winter. Both these studies documented high levels of weediness and patchy crop growth. In the context of this previous work our data suggest that bird use of miscanthus in summer and winter is likely to be variable, affected by region, weediness, crop structure and patchiness. While large-scale cropping of SRC in England is likely to have a positive overall impact on a suite of common farmland and woodland birds, our data suggest that miscanthus in the southwest of England may have an approximately neutral effect. However, some open farmland specialist species may be lost when planting either crop.
  • Authors:
    • Meijide, A.
    • Sanz-Cobena, A.
    • Sanchez-Martin, L.
    • Quemada, M.
    • Vallejo, A.
  • Source: European Journal of Soil Science
  • Volume: 61
  • Issue: 5
  • Year: 2010
  • Summary: The aim of this study was to evaluate the pattern of nitrous oxide (N 2O) and methane (CH 4) fluxes, and leaching losses of nitrate (NO 3-) and dissolved organic C (DOC), during a fallow-onion crop-fallow cycle in a Mediterranean area. The importance of the fallow (intercrop) period and the type of fertilizer were also evaluated. Goat and chicken manure (M) from an organic farm, digested pig slurry (DPS) and urea (U) were applied at a rate of 110 kg N ha -1 and compared with a zero N treatment (Control). The crop period contributed more than each fallow period to the total N 2O emission (ranging from 70 to 85% of the total emission, depending on the treatment). The variability of rainfall during fallow periods affected N 2O emissions, with the highest fluxes observed in the second fallow, which was the wetter. Negative net fluxes of N 2O (0 to -0.4 mg N 2O-N m -2 day -1) were mainly observed during the irrigation period and in fallow periods. The type of fertilizer had no effect on N 2O fluxes, but influenced the CH 4 oxidation. The largest CH 4 emission was from the manure treatment (2.4 mg CH 4-C m -2 day -1) during the irrigation period. The lowest NO 3- but highest DOC leaching rates were measured during the second fallow period from the manure treated plots (0.2 kg NO 3--N ha -1 and 3.9 kg C ha -1), which also had the highest drainage. The use of OM, therefore, seems to be a suitable method to reduce the environmental impacts associated with N leaching as well as increase the potential to denitrify NO 3- in groundwater.
  • Authors:
    • Launay, M.
    • Tourdonnet, S. de
    • Shili-Touzi, I.
    • Dore, T.
  • Source: Field Crops Research
  • Volume: 116
  • Issue: 3
  • Year: 2010
  • Summary: The introduction of a living cover crop during a cash crop growth cycle (relay intercropping) and its maintenance after the cash crop harvest may help to preserve biodiversity, increase soil organic matter content and carbon sequestration and provide other ecosystem services, such as natural pest regulation or nutrient recycling, by increasing useful biotic interactions within the agroecosystem. We studied the impact of various approaches to manage a red fescue cover crop in a winter wheat crop in terms of light, water and nitrogen competition, using the STICS crop model adapted for intercropping. The STICS model for wheat/fescue intercropping was first evaluated on two years of experimental data obtained in the field. It gave satisfactory statistical results for the prediction of dry matter, leaf area index (LAI) and nitrogen accumulation in the two species, and for nitrogen and water dynamics in the soil. By simulating unmeasured variables, such as transpiration, the model improves our understanding of the performance of the intercrop in the field. For example, we showed that the intercropping system was more efficient that wheat grown as a sole crop, in terms of nitrogen accumulation and decreasing soil nitrogen levels before the leaching period. However, it also resulted in lower wheat yields. We then used the STICS model to compare four intercropping management scenarios differing in terms of the date of red fescue emergence, over 35 climatic years. We found that, in most climatic scenarios, the emergence of the fescue crop during the late tillering phase of the wheat crop gave the best compromise between wheat yield overall nitrogen accumulation and radiation interception.
  • Authors:
    • Sa, M. E. de
    • Lazarini, E.
    • Silva, J. B. da
    • Vieira, R. D.
  • Source: Revista Brasileira de Sementes
  • Volume: 32
  • Issue: 2
  • Year: 2010
  • Summary: During the maturation and harvest of soybean (Glycine max (L.) Merr.) seed the ideal climatic conditions include dryness and lower temperatures. Using winter-sown (July to September) soybean we verified the effects of irrigation on the physiological quality of soybean seeds during maturity using a factorial treatment design with three varieties (IAC-19, Conquista and IAC 8-2) and two irrigation interruption times (starting at stage R 7 and irrigating until 14 days after stage R 8). The samples were taken at stage R 7 and at 3 days, 7 days, 10 days, 14 days (stage R 8) and 28 days after starting stage R 7. We evaluated the percentage germination, vigor using accelerated aging and electric conductivity tests, and the percentage of spotted and imperfect seeds and found that irrigation after stage R 7 does not reduce seed quality but can improve the physiological potential of the seeds.
  • Authors:
    • Walter, C.
    • Durand, P.
    • Viaud, V.
    • Sorel, L.
  • Source: Agricultural Systems
  • Volume: 103
  • Issue: 9
  • Year: 2010
  • Summary: Evaluating the environmental impacts of agricultural practices increasingly involves the use of spatially distributed simulation models that account for crop allocations across fields as an input factor. Our objective was to develop a model for spatio-temporal allocation of crops to a field pattern that was able to account for agronomic and spatial driving factors including crop production objectives, spatial distribution of the crops around farmsteads, and preferential allocation of crops on soil waterlogging classes. We developed a model based on stochastic decision trees (SDTs) to integrate farm type and field characteristics (area, distance to farmstead, waterlogging, and current crop) in the spatio-temporal allocation process without prior expert knowledge, and we compared the model to a reference model based on first-order Markov chains or transition matrices. A case study comparing both models was performed in the Naizin catchment (Western France), where crop allocation to fields was known for the period 1993-2006. The SDTs built had a general structure similar to transition matrices. SDTs and transition matrices exhibited similar performances in predicting crop transitions in time and in allocating crops to the proper soil waterlogging class. However, SDTs proved to better reproduce the spatial distribution of crops around the farmsteads. SDTs provide an integrated way to analyze and simulate crop allocation processes within a single integrated framework. The ease of constructing decision trees suggests potential couplings of SDT to various landscape-scale ecological models requiring a detailed description of the land use mosaic as input data. (C) 2010 Elsevier Ltd. All rights reserved.
  • Authors:
    • Fontaneli, R. S.
    • Santos, H. P. dos
    • Spera, S. T.
    • Tomm, G. O.
  • Source: Acta Scientiarum. Agronomy
  • Volume: 32
  • Issue: 1
  • Year: 2010
  • Summary: Soil physical characteristics were evaluated, after eight years (1995 to 2003), on a typic Hapludox located in Coxilha, Rio Grande do Sul State, Brazil. Six crop production systems were evaluated: system I (wheat-soybean/black oat+common vetch pasture-corn); system II (wheat-soybean/black oat+common vetch+annual ryegrass pasture-corn); system III (wheat-soybean/black oat+common vetch pasture-pearl millet pasture); system IV (wheat-soybean/black oat+common vetch+annual ryegrass pasture-pearl millet pasture); system V (wheat-soybean, white oat-soybean/black oat+common vetch pasture-pearl millet pasture); and system VI (wheat-soybean/white oat-soybean/black oat+common vetch+annual ryegrass pasture-pearl millet pasture). Soil bulk density and resistance to penetration increased from deeper layer (10-15 cm) to top layer (0-5 cm). In the systems I, V and VI, total porosity decreased and soil bulk density resistance to penetration increased from the deeper layers to top layer surface, due to higher intensity of livestock activities. After eight years of use, the production systems under no-till, involving annual winter and summer pastures and crops, did not promoted soil degradation, in constraining levels, on soil physical attributes.
  • 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.
  • Authors:
    • Dougall, A.
    • Halpin, N. V.
    • Stirling, G. R.
    • Bell, M. J.
  • Source: Proceedings of the 2010 Conference of the Australian Society of Sugar Cane Technologists held at Bundaberg, Queensland, Australia, 11-14 May 2010
  • Year: 2010
  • Summary: Lesion nematode ( Pratylenchus zeae) occurs in almost every sugarcane field in Queensland and is perhaps the most important of a community of nematode pests that cost the Australian sugar industry an estimated $82 million/annum in lost production. Legumes such as soybean and peanut are relatively poor hosts of the nematode and, when they are used as rotation crops in the sugarcane farming system, populations of P. zeae are markedly reduced. This paper provides data on the host status of other rotation crops that might have a place in the sugarcane farming system, together with some common weeds. The capacity of P. zeae to multiply on various plants was assessed after 70 days in pots at temperatures suitable for nematode reproduction, with multiplication factors calculated as (Pf/Pi), where Pf was the final nematode population density and Pi the initial inoculum density. Sugarcane and forage sorghum had the highest multiplication factors (Pf/Pi >40), whereas the nematode population on most other plants increased 5 to 13 times. Some cultivars of wheat, oats and Rhodes grass had multiplication factors of only 3 or 4 and three crops ( Setaria cv. Splenda, barley cv. Grimmett and cowpea cv. Red Caloona) were non-hosts (Pf/Pi