• Authors:
    • Brown, M. G.
    • Merwin, I. A.
    • Atucha, A.
  • Source: HortScience
  • Volume: 46
  • Issue: 8
  • Year: 2011
  • Summary: Groundcover management systems (GMSs) are essential for fruit production, but very few long-term studies have evaluated orchard GMS sustainability. We evaluated four GMSs-pre-emergence soil-active herbicides (PreHerb), post-emergence herbicide (PostHerb), a turfgrass cover crop (Sod), and hardwood bark mulch (Mulch)-in an apple (Malus domestica Borkh.) orchard over 16 years of continuous observation. There were no consistent long-term trends in fruit yields among GMSs, although during the first 5 years, yields were lower in trees on Sod. Tree growth was greater in PostHerb and Mulch than in Sod during the first 5 years, and during the next decade, trees in Mulch plots were consistently larger than in other GMSs. Total soil nitrogen (N) and carbon (C) content, C-to-N ratios, and essential plant nutrients were much greater in the Mulch soil after 16 years of treatments. Long-term responses of trees to groundcover vegetation indicated that apple trees respond adaptively to compensate for weed and grass competition. Year-round elimination of surface vegetation with residual soil active herbicides may be unnecessary or even detrimental for orchard productivity and soil fertility in established orchards. Post-emergence herbicides that reduce weed competition primarily during the summer months may offer an optimal combination of weed suppression and soil conservation.
  • Authors:
    • Elfstrand, S.
    • Båth, B.
    • Wetterlind, J.
    • Stenberg, M.
    • Bergkvist, G.
  • Source: Field Crops Research
  • Volume: 120
  • Issue: 2
  • Year: 2011
  • Summary: Four two-year field trials, arranged in randomised split-plots, were carried out in southern Sweden with the aim of determining whether reduced N fertiliser dose in winter wheat production with spring under-sown clover cover crops, with or without perennial ryegrass in the seed mixture, would increase the clover biomass and hence the benefits of the cover crops in terms of the effect on the wheat crop, on a subsequent barley crop and on the risk of N leaching. Four doses of nitrogen (0, 60, 120 or 180 kg N ha(-1)) constituted the main plots and six cover crop treatments the sub-plots. The cover crop treatments were red clover (Trifolium pratense L). white clover (Trifolium repens L) and perennial ryegrass (Lolium perenne L.) in pure stands and in mixtures. The winter wheat (Triticum aestivum L.) was harvested in August and the cover crops were ploughed under in November. The risk of N leaching was assessed in November by measuring the content of mineral N in the soil profile (0-30, 30-90 cm). In the following year, the residual effects of the cover crops were investigated in spring barley (Hordeum distichon L) without additional N. Under-sowing of cover crops did not influence wheat yield, while reduced N fertiliser dose decreased yield and increased the clover content of the cover crops. When N was applied, the mixed cover crops were as effective in depleting soil mineral nitrogen as a pure ryegrass cover crop, while pure clover was less efficient. The clover content at wheat harvest as well as the amount of N incorporated with the cover crops had a positive correlation with barley yield. Spring barley in the unfertilised treatments yielded, on average, 1.9-2.4 Mg DM ha(-1) more in treatments with clover cover crops than in the treatment without cover crops. However, this positive effect decreased as the N dose to the preceding wheat crop increased, particularly when the clover was mixed with grass. (C) 2010 Elsevier B.V. All rights reserved.
  • Authors:
    • Hedtcke, J. L.
    • Stoltenberg, D. E.
    • Posner, J. L.
    • Bernstein, E. R.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 4
  • Year: 2011
  • Summary: A major challenge that organic grain crop growers face is weed management. The use of a rye (Secale cereale L.) cover crop to facilitate no-tillage (NT) organic soybean [Glycine max (L.) Merr.] production may improve weed suppression and increase profitability. We conducted research in 2008 and 2009 to determine the effect of rye management (tilling, crimping, and mowing), soybean planting date (mid-May or early June), and soybean row width (76 or 19 cm), on soybean establishment, soil moisture, weed suppression, soybean yield, and profitability. Soybean establishment did not differ between tilled and NT treatments; and soil moisture measurements showed minimal risk of a drier soil profile in NT rye treatments. Rye mulch treatments effectively suppressed weeds, with 75% less weed biomass than in the tilled treatment by mid-July. However, by this time, NT soybean competed with rye regrowth, were deficient in Cu, and accumulated 22% as much dry matter (DM) and 28% as much N compared to the tilled treatment. Soybean row width and planting date within NT treatments impacted soybean productivity but not profitability, with few differences between mowed and crimped rye. Soybean yield was 24% less in the NT treatments than the tilled treatment, and profitability per hectare was 27% less. However, with fewer labor inputs, profitability per hour in NT rye treatments was 25% greater than in tilled soybean; in addition, predicted soil erosion was nearly 90% less. Although soybean yields were less in NT rye mulch systems, they represent economically viable alternatives for organic producers in the Upper Midwest.
  • Authors:
    • Lal, R.
    • Jagadamma, S.
  • Source: Biology and Fertility of Soils
  • Volume: 46
  • Issue: 6
  • Year: 2010
  • Summary: Soil organic carbon (SOC) is distributed heterogeneously among different-sized primary particles and aggregates. Further, the SOC associated with different physical fractions respond differently to managements. Therefore, this study was conducted with the objective to quantify the SOC associated with all the three structural levels of SOC (particulate organic matter, soil separates and aggregate-size fractions) as influenced by long-term change in management. The study also aims at reevaluating the concept that the SOC sink capacity of individual size-fractions is limited. Long-term tillage and crop rotation effects on distribution of SOC among fractions were compared with soil from adjacent undisturbed area under native vegetation for the mixed, mesic, Typic Fragiudalf of Wooster, OH. Forty five years of no-till (NT) management resulted in more SOC accumulation in soil surface (0-7.5 cm) than in chisel tillage and plow tillage (PT) treatments. However, PT at this site resulted in a redistribution of SOC from surface to deeper soil layers. The soils under continuous corn accumulated significantly more SOC than those under corn-soybean rotation at 7.5-45 cm depth. Although soil texture was dominated by the silt-sized particles, most of the SOC pool was associated with the clay fraction. Compared to PT, the NT treatment resulted in (i) significantly higher proportion of large macroaggregates (>2,000 m) and (ii) 1.5-2.8 times higher SOC concentrations in all aggregate-size classes. A comparative evaluation using radar graphs indicated that among the physical fractions, the SOC associated with sand and silt fractions quickly changed with a land use conversion from native vegetation to agricultural crops. A key finding of this study is the assessment of SOC sink capacity of individual fractions, which revealed that the clay fraction of agricultural soils continues to accumulate more SOC, albeit at a slower rate, with progressive increase in total SOC concentration. However, the clay fraction of soil under native woodlot showed an indication for SOC saturation. The data presented in this study from all the three structural levels of SOC would be helpful for refining the conceptual pool definitions of the current soil organic matter prediction models.
  • Authors:
    • Lal, R.
    • Ussiri, D. A. N.
    • Trumbore, S. E.
    • Mestelan, S.
    • Jagadamma, S.
  • Source: Biogeochemistry
  • Volume: 98
  • Issue: 1-3
  • Year: 2010
  • Summary: Accurate quantification of different soil organic carbon (SOC) fractions is needed to understand their relative importance in the global C cycle. Among the chemical methods of SOC fractionation, oxidative degradation is considered more promising because of its ability to mimic the natural microbial oxidative processes in soil. This study focuses on detailed understanding of changes in structural chemistry and isotopic signatures of SOC upon different oxidative treatments for assessing the ability of these chemicals to selectively isolate a refractory fraction of SOC. Replicated sampling (to ~1 m depth) of pedons classified as Typic Fragiudalf was conducted under four land uses (woodlot, grassland, no-till and conventional-till continuous corn [ Zea mays L.]) at Wooster, OH. Soil samples (<2 mm) were treated with three oxidizing agents (hydrogen peroxide (H 2O 2), disodium peroxodisulfate (Na 2S 2O 8) and sodium hypochlorite (NaOCl)). Oxidation resistant residues and the bulk soil from A1/Ap1 horizons of each land use were further analyzed by solid-state 13C nuclear magnetic resonance (NMR) spectroscopy and accelerator mass spectrometry to determine structural chemistry and 14C activity, respectively. Results indicated that, oxidation with NaOCl removed significantly less SOC compared to Na 2S 2O 8 and H 2O 2. The NMR spectra revealed that NaOCl oxidation preferentially removed lignin-derived compounds at 56 ppm and at 110-160 ppm. On the other hand, the SOC resistant to Na 2S 2O 8 and H 2O 2 oxidation were enriched with alkyl C groups, which dominate in recalcitrant macromolecules. This finding was corroborated by the 14C activity of residual material, which ranged from -542 to -259 per mil for Na 2S 2O 8 resistant SOC and -475 to -182 per mil for H 2O 2 resistant SOC as compared to relatively greater 14C activity of NaOCl resistant residues (-47 to 61 per mil). Additionally, H 2O 2 treatment on soils after light fraction removal was more effective in isolating the oldest ( 14C activity of -725 to -469 per mil) SOC fraction. The Delta 14C signature of SOC removed by different oxidizing agents, calculated by mass balance, was more or less similar irrespective of the difference in labile SOC removal efficiency. This suggests that SOC isolated by many fractionation methods is still a mixture of much younger and older material and therefore it is very important that the labile SOC should be completely removed before measuring the turnover time of stable and refractory pools of SOC.
  • Authors:
    • Wang, L.
    • van Ranst, E.
    • Li, C.
    • Tang, H.
    • Li, H.
    • Qiu, J.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 135
  • Issue: 1-2
  • Year: 2010
  • Summary: Agricultural production plays an important role in affecting atmospheric greenhouse gas concentrations. Field measurements were conducted in Quzhou County, Hebei Province in the North China Plains to quantify carbon dioxide (CO 2) and nitrous oxide (N 2O) emissions from a winter wheat-maize rotation field, a common cropping system across the Chinese agricultural regions. The observed flux data in conjunction with the local climate, soil and management information were utilized to test a process-based model, Denitrification-Decomposition or DNDC, for its applicability for the cropping system. The validated DNDC was then used for predicting impacts of three management alternatives (i.e., no-till, increased crop residue incorporation and reduced fertilizer application rate) on CO 2 and N 2O emissions from the target field. Results from the simulations indicated that (1) CO 2 emissions were significantly affected by temperature, initial SOC, tillage method, and quantity and quality of the organic matter added in the soils; (2) increases in temperature, initial SOC, total fertilizer N input, and manure amendment substantially increased N 2O emissions; and (3) temperature, initial SOC, tillage, and quantity and quality of the organic matter added in the soil all had significant effects on global warming. Finally, five 50-year scenarios were simulated with DNDC to predict their long-term impacts on crop yield, soil C dynamics, nitrate leaching losses, and N 2O emissions. The modelled results suggested that implementation of manure amendment or crop residue incorporation instead of increased fertilizer application rates would more efficiently mitigate GHG emissions from the tested agro-ecosystem. The multi-impacts provided a sound basis for comprehensive assessments on the management alternatives.
  • Authors:
    • Chiriac, I. P.
    • Bălan, A.
    • Lipșa, F. D.
    • Ulea, E.
  • Source: Lucrări ŞtiinÅ£ifice
  • Volume: 53
  • Issue: 1
  • Year: 2010
  • Summary: Research was carried out on rapeseed ( Brassica napus L.) field trials located in the south region of Moldavian plain (Ezareni Farm), studying the effects of fertilization (organic, mineral) and soil tillage systems on soil population. Soil tillage has been realized with plough (in classic system), with chisel, rotary harrow (in minimum soil tillage) and in no-till system. The objectives of this investigation were to isolate and quantify the existing microbial population in soil (Gram positive bacteria, Gram negative bacteria, micromycetes) establishing their participation ratio, the main fungus genres which activate in soil and their activity level for each variant. The results illustrate the influence of the fertilization and soil tillage systems on the dinamic of microorganisms population, on the relationship between the main groups (bacteria and fungi), and on the micromycetes spectrum determined in each variant of our experiment.
  • Authors:
    • Wilson, D.
    • Mischler, R.
    • Duiker, S. W.
    • Curran, W. S.
  • Source: Agronomy Journal
  • Volume: 102
  • Issue: 1
  • Year: 2010
  • Summary: Rolling-crimping to control hairy vetch ( Vicia villosa Roth) may make organic no-till corn ( Zea mays L.) possible. This study investigated how rolling-crimping date and growth stage of the cover crop affected hairy vetch control and if a rolled-crimped hairy vetch cover crop could supply weed control for no-till corn. Hairy vetch was planted in late August and was rolled and crimped and planted to corn at four dates ("planting dates") between late May and late June at three Pennsylvania locations. Hairy vetch biomass, measured at each planting date, varied from 2000 to 8000 kg ha -1. Hairy vetch control with the roller-crimper varied through the flowering stage and was consistent after early pod set. The hairy vetch cover crop reduced weed density by at least 50%, with annual weeds being affected more than perennials. Total weed biomass was reduced 31, 93, and 94% in different site-years compared with no-cover plots. As corn planting dates were delayed, greater amounts of vetch mulch and lower weed density helped reduce weed biomass. Corn yields in the organic no-till system with a hairy vetch cover crop ranged from 1.1 Mg ha -1 to 9.6 Mg ha -1. Low yields were attributed to incomplete control of hairy vetch, weed competition, reduced corn plant populations, increased insect pests, and possibly inadequate N supply. This study shows that it is possible to kill hairy vetch with a roller-crimper and provide weed control for organic corn, resulting in reasonable corn yields, but that production risk increases.
  • Authors:
    • Newman, J. K.
    • Laflen, J. M.
    • Kaleita, A. L.
  • Source: Journal of Soil and Water Conservation
  • Volume: 65
  • Issue: 4
  • Year: 2010
  • Summary: Corn stover is promoted as a readily available feedstock for cellulosic ethanol fermentation, potentially adding value to Iowa's corn harvest. However, soil productivity and water quality could be adversely affected by poor residue management practices. This paper presents the results of computer simulations of soil erosion by water under various corn stover harvesting and management scenarios applied universally across the state of Iowa. The WEPP (Water Erosion Prediction Project) computer model was used to simulate soil loss in Iowa at 17,848 agricultural point locations of the 1997 National Resources Inventory. Location information at the township level of 9.66 by 9.66 km (6 by 6 mi) for the National Resources Inventory points allows for presentation of results in the form of gridded color-scale maps. The maps indicate corn stover removal risk at the following levels: extreme, high, medium, or low. Risk categories are based on the soil loss tolerance (T) and 1/2 T as constraints. This paper presents simulated impacts of corn stover removal on soil erosion only. Important considerations for maintaining soil organic carbon are reviewed and discussed. The simulation results suggest that the amount of harvestable corn stover is not uniform in Iowa when water erosion control guides management. No-till is necessary to maintain soil loss below permissible levels of T and 1/2T in regions with steeper slopes. Maps and corresponding analyses in this paper help guide policy pertaining to the harvest of corn stover in Iowa.
  • Authors:
    • Ferguson, R. B.
    • Liska, A. J.
    • Wortmann, C. S.
    • Lyon, D. J.
    • Klein, R. N.
    • Dweikat, I.
  • Source: Agronomy Journal
  • Volume: 102
  • Issue: 1
  • Year: 2010
  • Summary: Sweet sorghum [SS; Sorghum bicolor (L.) Moench] is a potential biofuel crop for the Great Plains. Sweet sorghum was compared with corn [ Zea mays (L.)] and grain sorghum for potential ethanol yield, energy use efficiency, and greenhouse gas (GHG) emissions at seven dryland site-years in Nebraska. Seasonal rainfall ranged from approximately 340 to 660 mm. Soils were deep with medium texture at all site-years. The effects of seeding rate, N rate, and cultivar on SS performance were evaluated. Sweet sorghum sugar yield was not affected by seeding rate and N application at six of seven site-years, but yield was increased by 19% at one site-year. Calculated ethanol yield and net energy yield were 33 and 21% more, respectively, with the grain crops compared with SS, but mean net energy yield of an earlier-maturing SS cultivar was comparable with the grain crops. The mean ratio of energy produced in ethanol per total energy invested was 23% less for grain crops compared with SS. Mean life cycle GHG emissions were 53% and 66 to 69% less compared with gasoline for SS and grain crops, respectively. Very efficient use of the ethanol coproducts was assumed for the grain crops while SS bagasse was assumed to be returned to the field. At least one SS cultivar is competitive with grain crops for some biofuel criteria, but SS is not competitive with grain crops for total or net liquid transportation fuel produced per hectare.