• Authors:
    • Clay, D. E.
    • Carlson, C. G.
    • Clay, S. A.
    • Reicks, G.
    • Kim, K.
    • Mamani-Pati, F.
  • Source: Agronomy Journal
  • Volume: 102
  • Issue: 6
  • Year: 2010
  • Summary: The harvesting of plant biomass in excess of the soil organic carbon (SOC) maintenance requirement can produce short-term economic benefits at the cost of long-term sustainability. The objective of this study was to assess the impact of corn ( Zea mays L.) harvesting approach, N rate, and simulated landscape positions on estimated long-term SOC maintenance, profitability, and the energy efficiency of no-till corn grown in eastern South Dakota. The 3-yr experiment (2002-2004) contained four N rates (0, 56, 112, and 168 kg N ha -1), two simulated landscape positions (shoulder and backslope), and two harvesting methods (grain with 100% stover returned or grain+40% corn stover returned). No-tillage was used at the site. Energy gains (out-input), for a cropping system where corn grain or corn grain plus stover was sold for ethanol production, were calculated. Profitability was estimated and SOC turnover was simulated using the annual time-step model, SOC t=SOC t-1+k NHCNHC-k soc SOC t-1, where SOC t was SOC at time t, SOC t-1 was SOC at the sampling date before time t, k NHC was rate that nonharvested carbon (NHC) was converted to SOC, and k soc was the rate that SOC was converted to CO 2 Tillage impacts on k SOC was estimated with the model k soc [g SOC-C (g SOC year) -1]=0.0115+0.00631(tillage events). When only grain was harvested, the highest and lowest energy gains and financial were associated with the 112 kg N ha -1 (46.6 GJ ha -1 and $427 ha -1) and the 0 kg N per ha -1 (37.5 GJ ha -1 and $192 ha -1) treatments, respectively. Applying more than 112 kg N ha -1 did not increase energy gains or financial returns. Profits were increased by 60% when corn stover was harvested for ethanol production and lower yielding simulated shoulder/summit position had a lower energy gain (59.3 GJ ha -1 and $425 ha -1) and financial return than the backslope position (66.3 GJ ha -1 and $614 ha -1). The SOC sustainability analysis suggests that the ability of a system to maintain SOC depends on many factors including the amount of nonharvested carbon returned to the site, and the amount of carbon contained in the soil.
  • 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:
    • Mulvaney, M. J.
    • Wood, C. W.
    • Kemble, J. M.
    • Balkcom, K. S.
    • Shannon, D. A.
  • Source: Agronomy Journal
  • Volume: 102
  • Issue: 5
  • Year: 2010
  • Summary: A combination of high biomass cover crops with organic mulches may be an option for no-till vegetable production, but information on mineralization rates from these residues is lacking. The objective of this study was to assess nutrient release rates and persistence from mimosa ( Albizia julibrissin Durazz.), lespedeza [ Lespedeza cuneata (Dum. Cours.) G. Don], oat ( Avena sativa L.) straw, and soybean [ Glycine max (L.) Merr.] residues under conventional and conservation tillage. The experiment was conducted in Tallassee, AL using litterbag methodology in a split-plot design (main plots: two tillage systems; subplots: four residue types). Comparison of rate constants showed that labile portions of residues was more affected by tillage than recalcitrant portions. In spring, mimosa residue contained 78 kg N ha -1 when buried the previous fall, compared to 123 kg N ha -1 when surface placed; soybean residue showed similar results (39 vs. 72 kg N ha -1, respectively). Results were similar for lespedeza (72 vs. 101 kg N ha -1, respectively), but not for oat straw (24 vs. 26 kg N ha -1, respectively). After 1 yr, surface placed mimosa residue mineralized 33% of initial N compared to 71% when buried, while surface placed lespedeza mineralized 36% of initial N compared to 64% when buried. Soybean residue mineralized N quickly regardless of placement (73 vs. 87%, respectively). This study demonstrates that cut-and-carry mulches may be used under conservation tillage for the enhancement of soil organic matter (SOM), soil organic carbon (SOC), and soil N status.
  • 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:
    • Schroeder, K. L.
    • Paulitz, T. C.
    • Schillinger, W. F.
  • Source: Plant Disease
  • Volume: 94
  • Issue: 1
  • Year: 2010
  • Summary: An irrigated cropping systems experiment was conducted for 6 years in east-central Washington State to examine agronomic and economic alternatives to continuous annual winter wheat ( Triticum aestivum) with burning and plowing, and to determine how root diseases of cereals are influenced by management practices. The continuous winter wheat treatment with burning and plowing was compared with a 3-year no-till rotation of winter wheat-spring barley ( Hordeum vulgare)-winter canola ( Brassica napus) and three straw management treatments: burning, straw removal, and leaving the straw stubble standing after harvest. Take-all disease and inoculum increased from years 1 to 4 in the continuous winter wheat treatment with burning and plowing, reducing plant growth compared to the no-till treatments with crop rotations. Inoculum of Rhizoctonia solani AG-8 was significantly lower in the tilled treatment compared to the no-till treatments. Inoculum concentration of Fusarium pseudograminearum was higher than that of F. culmorum, and in one of three years, the former was higher in treatments with standing stubble and mechanical straw removal compared to burned treatments. Residue management method had no effect on Rhizoctonia inoculum, but spring barley had more crown roots and tillers and greater height with stubble burning. This 6-year study showed that irrigated winter wheat can be produced in a no-till rotation without major disease losses and demonstrated how cropping practices influence the dynamics of soilborne cereal diseases and inoculum over time.
  • Authors:
    • Sainju, U. M.
    • Jabro, J. D.
    • Caesar-TonThat, T.
  • Source: Journal of Environmental Quality
  • Volume: 39
  • Issue: 3
  • Year: 2010
  • Summary: Management practices are needed to reduce dryland sod CO(2) emissions and to increase C sequestration We evaluated the effects of tillage and cropping sequence combinations and N fertilization on dryland crop biomass (stems + leaves) and sod surface CO(2) flux and C content (0- to 120-cm depth) in a Williams loam from May to October, 2006 to 2008, in eastern Montana. Treatments were no-tilled continuous malt barley (Hordeum vulgaris L) (NTCB), no-tilled malt bailey pea (Pivot; sativum L) (NTB-P), no-tilled malt barley fallow (NTB-F), and conventional-tilled malt barley fallow (CTB-F), each with 0 and 80 kg N ha(-1) Measurements were made both in Phase I (malt barley in NTCB, pea in NTB-P, and fallow in NTB-F and CTB-F) and Phase II (malt barley in all sequences) of each cropping sequence in every year Crop biomass varied among years. was greater in the barley than in the pea phase of the NTB-P treatment, and greater in NTCB and NTB-P than in NTB-F and CTB-F in 2 out of 3 yr Similarly biomass was greater with 80 than with 0 kg N ha(-1) in 1 out of 3 yr. Soil CO(2) flux increased from 8 mg C m(-2) h(-1) in early May to 239 mg C m(-2) h(-1) in mid-June as temperature increased and then declined to 3 mg C m(-2) h(-1) in September. October Fluxes peaked immediately following substantial precipitation (>10 mm). especially in NTCB and NTB-P Cumulative CO(2) flux from May to October was greater in 2006 and 2007 than in 2008, greater in cropping than in fallow phases, and greater in NTCB than in NTB-F. Tillage did not influence crop biomass and CO(2) flux but N fertilization had a variable effect on the flux in 2008. Similarly, soil total C content was not influenced by treatments Annual cropping increased CO(2) flux compared with crop fallow probably by increasing crop residue returns to sods and root and rhizosphere respiration Inclusion of peas in the rotation wills malt barley in the no-till system, which have been known to reduce N fertilization rates and sustain malt barley yields, resulted in a CO(2) flux similar to that in the CTB-F sequence
  • Authors:
    • Saseendran, S. A.
    • Nielsen, D. C.
    • Ma, L. W.
    • Ahuja, L. R.
    • Vigil, M. F.
  • Source: Agronomy Journal
  • Volume: 102
  • Issue: 5
  • Year: 2010
  • Summary: Long-term crop rotation effects on crop water use and yield have been investigated in the Central Great Plains since the 1990s. System models are needed to synthesize these long-term results for making management decisions and for transferring localized data to other conditions. The objectives of this study were to calibrate a cropping systems model (RZWQM2 with the DSSAT v4.0 crop modules) for dryland wheat ( Triticum aestivum L.), corn ( Zea mays L.), and proso millet ( Panicum miliaceum L.) production in the wheat-corn-millet (WCM) rotation from 1995 to 2008, and then to evaluate the model from 1992-2008 for two additional rotations, wheat-fallow (WF) and wheat-corn-fallow (WCF) on a Weld silt loam soil under no-till conditions. Measured biomass and grain yield for the above three rotations were simulated reasonably well with root mean squared errors (RMSEs) ranging between 1147 and 2547 kg ha -1 for biomass, and between 280 and 618 kg ha -1 for grain yield. Corresponding index of agreement (d) ranged between 0.70 and 0.95 for biomass, and between 0.87 and 0.97 for grain yield. The validated model was further used to evaluate two additional crop rotations: wheat-millet-fallow (WMF) and wheat-corn-millet-fallow (WCMF) (1993-2008) without prior knowledge of the two rotations. We found that the model simulated the mean and range of yield and biomass of the three crops well. These results demonstrated that RZWQM2 can be used to synthesize long-term crop rotation data and to predict crop rotation effects on crop production under the semiarid conditions of eastern Colorado.
  • Authors:
    • Kennedy, A. C.
    • Schillinger, W. F.
    • Young, D. L.
    • Paulitz, T. C.
  • Source: Field Crops Research
  • Volume: 115
  • Issue: 1
  • Year: 2010
  • Summary: Field burning of residue is a traditional management tool for irrigated wheat ( Triticum aestivum L.) production in the Inland Pacific Northwest of the United States (PNW) that can result in reduced air quality. A 6-year no-till field experiment to evaluate two complete cycles of a 3-year irrigated crop rotation of winter wheat-spring barley ( Hordeum vulgare L.)-winter canola ( Brassica napus L.) was sown (i) directly into standing residue of the previous crop, (ii) after mechanical removal of residue and, (iii) after burning of residue. The traditional practice of continuous annual winter wheat sown after burning residue and inverting the topsoil with a moldboard plow was included as a check treatment. Over-winter precipitation storage efficiency (PSE) was markedly improved when residue was not burned or burned and plowed after grain harvest. Grain yield of winter wheat trended higher in all no-till residue management treatments compared to the check treatment. Average grain yields of spring barley and canola were not significantly different among the no-till residue management treatments. Winter canola failed in 5 of 6 years due to a combination of a newly identified Rhizoctonia damping-off disease caused by Rhizoctonia solani AG-2-1 and cold temperatures that necessitated replanting to spring canola. Six-year average net returns over total costs were statistically equal over all four systems. All systems lost from $358 to $396 ha -1. Soil organic carbon (SOC) increased linearly each year with no-till at the 0-5 cm depth and accumulated at a slower rate at the 5-10 cm depth. Take-all of wheat caused by Gaeumannomyces graminis var. tritici was most severe in continuous annual winter wheat. The incidence and severity of Rhizoctonia on roots of wheat and inoculum of R. solani AG-8, was highest in the no-till treatments, but there was no grain yield loss due to this disease in any treatment. Residue management method had no consistent effect on Rhizoctonia root rot on barley. The annual winter grass downy brome ( Bromus tectorum L.) was problematic for winter wheat in the standing and mechanically removed residue treatments, but was controlled in the no-till residue burned and the burn and plow check. Another winter annual grass weed, rattail fescue ( Vulpia myuros L.), infested all no-till treatments. This was the first comprehensive and multidisciplinary no-till irrigated crop rotation study conducted in the Pacific Northwest.
  • Authors:
    • Millen, J.
    • Evans, D.
    • Sadler, E.
    • Camp, C.
    • Stone, K.
  • Source: Applied Engineering in Agriculture
  • Volume: 26
  • Issue: 3
  • Year: 2010
  • Summary: Availability of spatially-indexed data and crop yield maps has caused increased interest in site-specific management of crop inputs, especially water and fertilizer As commercial equipment to implement site-specific applications of water and nutrients becomes available, crop response to variable inputs and decision support systems will be required to ensure profitable crop production while conserving natural resources and protecting the environment. The objective of this research was to determine corn yield response to a range of nitrogen fertilizer and irrigation amounts on a relatively uniform southeastern Coastal Plain soil under conservation tillage. Corn was grown in a field experiment using a center pivot irrigation system that had been modified to make site-specific applications of water and fertilizer during the period 1999-2001 on a site near Florence, South Carolina. Treatments included three antecedent crop rotations (prior four years), three irrigation regimes (0, 75%, and 150% of a base rate, IBR), and four nitrogen fertilizer amounts (50%, 75%, 100%, and 125% of a base rate, NBR), and with Put. replications. As expected, corn grain yields increased with irrigation and N fertilizer Mean corn grain yields for the three-year study ranged from 6.3 to 8.9 Mg/ha for the 0% IBR avail-twin, 9.4 to 10.5 Mg/ha for the 75% IBR treatment, and 10.0 to 10.6 Mg/ha for the 150% IBR treatment. The mean corn grain yields in response to N applications ranged from 6.4 to 8.0 Mg/ha for the 50% IBR treatment, 8.6 to 9.4 Mg/ha for the 75% NBR treatment, 9.1 to 10.9 Mg/ha for the 100% NBR treatment, and 8.8 to 11.7 for the 125% NBR treatment. However, the nature of the response varied among the three years, mainly because of differences in rainfall and rainfall distribution during the growing season. Also, during the first,year there was less response to N fertilizer (7.9 to 9.1 Mg/ha) possibly because of residual soil N from antecedent soybean crop. A regression analysis indicated that the slopes of the corn yield response to increased N fertilizer application were low for both irrigated and rainfed treatments in 1999. In both 2000 and 2001, the slopes were greater for the corn yield response to increased N fertilizer In 2000, the irrigated treatments had a greater slope of the yield response for additional N fertilizer than did the minted treatments. Using an orthogonal contrast analysis, the overall yield response for the combined irrigation treatments to N fertilizer was quadratic in 1999 and 2000, and linear in 2001. These quadratic yield response's indicated that, for these conditions, a potential upper limit on production for the applied N-fertilizer and water (rainfall and irrigation) was approached. For the minted treatment, yield response to N fertilizer was linear in all three years. These results provide useful information that should be helpful in developing management strategies and decision support systems for profitable management of both water and N fertilizer on spatially-variable soils in the southeastern Coastal Plain while conserving natural resources and protecting the environment.
  • Authors:
    • Maul, J. E.
    • Buyer, J. S.
    • Austin, E. E.
    • Treonis, A. M.
    • Spicer, L.
    • Zasada, I. A.
  • Source: Applied Soil Ecology
  • Volume: 46
  • Issue: 1
  • Year: 2010
  • Summary: Soil microorganisms (bacteria, fungi) and microfauna (nematodes, protozoa) have been shown to be sensitive to organic amendments, but few experiments have investigated the responses of all these organisms simultaneously and across the soil profile. We investigated the impact of organic amendment and tillage on the soil food web at two depths in a field experiment. Over three growing seasons, field plots received seasonal organic amendment that was either incorporated into the soil (tilled) or not (no-till) as part of a tomato/soybean/corn cropping system. Un-amended, control plots that were either tilled or no-till were also included. We hypothesized that the addition of amendments would have a bottom-up effect on the soil food web, positively influencing the abundance of microorganisms, protozoa, and nematodes, primarily in the surface layers of the soil, but that this effect could be extended into deeper layers via tillage. Organic amendment had positive effects on most measured variables, including organic matter, respiration, protozoan and nematode density, and the abundance of PLFA biomarkers for bacteria and fungi. These effects were more pronounced in the 0-5 cm depth, but most variables increased with amendment in the deeper layer as well, especially with tillage. Denaturing Gradient Gel Electrophoresis (DGGE) of bacterial rDNA fragments indicated that distinct bacterial communities were selected for among tillage and amendment treatments and depths. Nematode faunal indices were not influenced by amendment, however. Increased nematode density in amended soils encompassed all trophic groups of free-living nematodes, with the greatest response among fungal-feeders, particularly with tillage. Increased biomass of microorganisms and decomposer microfauna in amended, tilled soils (0-5 cm depth) corresponded with a decline in the abundance of plant-parasitic nematodes. In control soils (0-5 cm depth), tillage reduced the relative abundance of fungal-feeding nematodes and increased the density of bacterial-feeding nematodes, in particular nematode species contributing to the Enrichment Index. When combined with organic amendment however, tillage was associated with increases in fungal-feeding nematodes and fungal biomarker PLFA. The results of this study suggest that when combined with amendment, tillage enhances the soil food web beyond the effect of amendment alone and is associated with declines in plant-parasitic nematodes.