- Authors:
- Knezevic, S. Z.
- Leeson, J. Y.
- Thomas, A. G.
- Acker, R. C. van
- Frick, B. L.
- Source: Canadian Journal of Plant Science
- Volume: 80
- Issue: 4
- Year: 2000
- Summary: In 1997, a weed survey was conducted during July and August in fields of wheat, barley, oat, canola [rape] and flax in Manitoba, Canada. Field selection was based on a stratified-random sampling methodology using ecodistricts as strata. Species in the Poaceae family were most commonly observed in the survey, followed by species in the Polygonaceae, Asteraceae and Brassicaceae families. The six most abundant weed species were green foxtail ( Setaria viridis), wild oats ( Avena fatua), wild buckwheat ( Polygonum convolvulus) [ Fallopia convolvulus], Canada thistle ( Cirsium arvense), red-root pigweed ( Amaranthus retroflexus) and wild mustard ( Sinapis arvensis). The survey highlighted significant differences between ecoregions and between crops in residual weed infestations. The weed community in the Boreal Transition ecoregion was dominated by seven species, whereas fields in the Aspen Parkland and Lake Manitoba Plain ecoregions were dominated by two species and the Interlake Plain ecoregion was dominated by only one species. Although significant differences were found between the weed communities in crops, they were not as great as differences between ecoregions. The Manitoba residual weed community in 1997 was very similar to that reported for 1978-81 and 1986, suggesting that the same species should remain a focus for weed management.
- Authors:
- Source: Sveriges Utsädesförenings Tidskrift
- Volume: 110
- Issue: 4
- Year: 2000
- Summary: The use of hydroponic techniques to measure the response to stress by cereals is discussed with reference to studies on drought, low N inputs and crop weed competition with barley, wheat, oats, triticale and rape.
- Authors:
- Ray, D. E.
- Slinsky, S. E.
- Graham, R. L.
- Becker, D. A.
- de la Torre Ugarte, D.
- Turhollow, A.
- Perlack, R. L.
- Walsh, M. E.
- Year: 1999
- Authors:
- Black, A. L.
- Krupinsky, J. M.
- Merrill, S. D.
- Halvorson, A. D.
- Source: Agronomy Journal
- Volume: 91
- Issue: 4
- Year: 1999
- Summary: Winter wheat (Triticum aestivum L.) can add diversity to dryland crop rotations in the northern Great plains, but it is susceptible to winterkill in low surface residue environments. A 12-year study was conducted to determine the response of two winter wheat cultivars, Roughrider and Norstar; to tillage system (conventional-till, CT; minimum-till, MT: and no-till, NT) and N fertilizer rate (34, 67, and 101 kg N ha(-1)) in a dryland spring wheat-winter wheat-sunflower (Helianthus annuus L,) rotation. Grain yields were greater with MT (1968 kg ha(-1)) and NT (2022 kg ha(-1)) than with CT (1801 kg ha(-1)), but tillage system effects on grain yield varied among years, Increasing N rate from 34 kg N ha(-1) to 67 kg N ha(-1) increased grain production from 1844 to 1953 kg ha(-1), but yield response to N rate varied among years., The greatest overall grain yield (2111 kg ha(-1)) if as obtained with NT and application of 101 kg N ha(-1). Grain yields were lowest during gears when plant-available Hater (PAW) was 400 an PAW, leaf spot disease incidence was greatest, particularly at the lowest N rate with NT. Application of adequate N reduced the disease incidence in all tillage treatments. Cultivar differences Here significant 3 out of 12 years, but not consistent. Winterkill was a factor for both cultivars in only 1 year in the CT and MT plots. Winter wheat performed Hell as a rotational crop in this cropping system when using,tfT and NT systems and adequate N fertility, Our long-term results indicate that producers in the northern Great Plains ran use winter wheat successfully in annual cropping systems that do not include a fallow period, particularly if NT is used with adequate N fertilization.
- Authors:
- Merrill, S. D.
- Tanaka, D. L.
- Black, A. L.
- Halvorson, A. D.
- Krupinsky, J. M.
- Source: Agronomy Journal
- Volume: 91
- Issue: 4
- Year: 1999
- Summary: Sunflower (Helianthus annuus L.) is a warm-season, intermediate water-use crop that can add diversity to dryland crop rotations, Reduced tillage systems may Enhance sunflower yield in intensive cropping systems. A 12-year study was conducted to determine how sunflower cultivars of early and medium maturity respond to tillage system (conventional-till, CT; minimum-till, MT; no-till, NT) and N fertilization (34, 67, and 101 kg N ha(-1)) within a dryland spring wheat (Triticum aestivum L.)-winter wheat-sunflower rotation. Averaged across N rates, cultivars, and years, sunflower seed yields were greater with MT (1550 kg ha(-1)) than with NT (1460 kg ha(-1)) and CT (1450 kg ha(-1)). Increasing N rate above 34 kg N ha-L generally increased gain yield, but varied from year to year. The tillage X N interaction showed that the highest seed yields were obtained with NT (1638 kg ha(-1)) and MT (1614 kg ha(-1)) at 101 kg N ha(-1). Total plant-available water (TPAW) of 500 mm did not result in increased sunflower yields over those with 350 to 500 mm TPAW. Yield differences between cultivar maturity classes varied from year to gear and with tillage and N level. At the lowest N rate, weeds were more problematic in NT than in CT and MT plots. More N fertilizer may be needed with NT to optimize sunflower yields than with CT and MT, because of less residual soil NO3-N with NT. Results indicate that producers in the northern Great Plains can use sunflower successfully in annual a cropping systems, particularly if MT and NT are used with adequate N fertilization.
- Authors:
- Peters, M.
- House, R.
- Lewandrowski, J.
- McDowell, H.
- Source: Agricultural Outlook
- Year: 1999
- Authors:
- Paul, E. A.
- Huggins, D. R.
- Dick, W. A.
- Bundy, L. G.
- Blevins, R. L.
- Christenson, D. R.
- Collins, H. P.
- Source: Soil Science Society of America Journal
- Volume: 63
- Issue: 3
- Year: 1999
- Summary: We used natural 13C abundance in soils to calculate the fate of C4-C inputs in fields cropped to continuous corn (Zea mays L.). Soil samples were collected from eight cultivated and six adjacent, noncultivated sites of the Corn Belt region of the central USA. The amount of organic C in cultivated soils declined an average of 68%, compared with adjacent, noncultivated sites. The {delta} 13C of cultivated soil profiles that had been under continuous corn for 8 to 35 yr increased in all depth increments above that of the noncultivated profiles. The percentage of soil organic C (SOC) derived from corn residues and roots ranged from 22 to 40% of the total C. The proportion of corn-derived C, as determined by this technique, decreased with soil depth and was minimal in the 50- to 100-cm depth increments of fine-textured soils. The mean residence time of the non-corn C (C3) ranged from 36 to 108 yr at the surface, and up to 769 yr at the subsoil depth. The longer turnover times were associated with soils high in clay. Prairie-derived soils have a higher potential to sequester C than those derived from forests. The significant loss of total C at all sites and the slow turnover times of the incorporated C lead us to conclude that there is a substantial potential for soils to serve as a C sink and as a significant nutrient reserve in sustainable agriculture.
- Authors:
- Source: Agricultural and Food Science in Finland
- Volume: 8
- Issue: 4/5
- Year: 1999
- Summary: The role of plant growth regulators (PGR) in nitrogen (N) fertilization of spring wheat and oats (CCC [chlormequat]), fodder barley (etephon/mepiquat) an oilseed rape (etephone) in crop rotation was studied in 1993-96 on loamy clay soil. Carry over effect of the N fertilization rates (0-180 kg/ha) was evaluated in 1997. N fertilization rate for the best grain/seed yield (120-150 kg/ha) was not affected by PGRs. The seed and N yields of oilseed rape were improved frequently by the recommended use of PGR. The yield of oats increased in 1995-96. Even though PGR effectively shortened the plant height of spring wheat, the grain yield increased only in 1995. N yield of wheat grains was not increased. Response of fodder barley to PGR was insignificant or even negative in 1995. The data suggest that PGRs may decrease some N leaching at high N rates by improving N uptake by grain/seeds, if the yield is improved. The carryover study showed that in soils with no N fertilization, as well as in soils of high N rates, N uptake was higher than in soils with moderate N fertilization (60-90 kg/ha), independent of PGRs. According to soil mineral N contents, N leaching risk was significant (15-35 kg/ha) only after dry and warm late seasons. After a favourable season of high yields, the N rates did not significantly affect soil mineral N contents.
- Authors:
- Williams, J. R.
- Kramer, L. A.
- Gassman, P. W.
- Chung, S. W.
- Gu, R.
- Source: Journal of Environmental Quality
- Volume: 28
- Issue: 3
- Year: 1999
- Summary: The Erosion Productivity Impact Calculator (EPIC) model was validated using long-term data collected for two southwest Iowa watersheds in the Deep Loess Soil Region, which have been cropped in continuous corn (Zea mays L.) under two different tillage systems (conventional tillage vs. ridge-till). The annual hydrologic balance was calibrated for both watersheds during 1988 to 1994 by adjusting the runoff curve numbers and residue effects on soil evaporation. Model validation was performed for 1976 to 1987, using both summary statistics (means or medians) and parametric and nonparametric statistical tests. The errors between the 12-yr predicted and observed means or medians were <10% for nearly all of the hydrologic and environmental indicators, with the major exception of a nearly 44% overprediction of the N surface runoff loss for Watershed 2. The predicted N leaching rates, N losses in surface runoff, and sediment loss for the two watersheds clearly showed that EPIC was able to simulate the long-term impacts of tillage and residue cover on these processes. However, the results also revealed weaknesses in the model's ability to replicate year-to-year variability, with r2 values generally <50% and relatively weak goodness-of-fit statistics for some processes. This was due in part to simulating the watersheds in a homogeneous manner, which ignored complexities such as slope variation. Overall, the results show that EPIC was able to replicate the long-term relative differences between the two tillage systems and that the model is a useful tool for simulating different tillage systems in the region.
- Authors:
- Source: Journal of Production Agriculture
- Volume: 11
- Issue: 3
- Year: 1998
- Summary: Tillage and N management are important in dryland crop production of the west central Great Plains (area between the 99(th) meridian and the eastern edge of the Rocky Mountains) because of frequent periods of limited soil moisture. Therefore, judicious use of N fertilizer is a management priority in wheat (Triticum aestivum L,)-sorghum [Sorghum biocolor (L,) Moench]- fallow (W-S-F) rotations. The objectives of this study were to: (i) determine the long-term effects of N fertilization (0, 20, 40, and 60 lb N/acre) on grain yields of winter wheat and grain sorghum under three tillage systems, (ii) investigate the effect of soil moisture at or near planting on grain yields, and (iii) evaluate the residual profile soil inorganic N after 20 yr of N fertilization in the three tillage systems. The study involved a W-S-F rotation under three tillage systems on a nearly level Harney silt loam soil (fine, montmorillonite, mesic Typic Argiustoll), The three tillage systems were clean-till (CT), reduced-till (RT), and no-till (NT), Nitrogen was broadcast preplant as ammonium nitrate on each crop at rates of 0, 20, 40, and 60 Ib N/acre, As the level of soil moisture increased in each tillage system, there was a corresponding larger yield increase of wheat and sorghum to applied N, The correlation of grain yields of wheat and sorghum with soil profile N at all depths was highest for nitrate N and lowest for ammonium and total inorganic N. For all three tillage systems, sampling deeper than 6 in, resulted in little improvement in the coefficient of determination (R-2) for grain yields regressed on soil nitrate N, Residual soil nitrate N was highest in the top 6 in., dropped significantly in the 6- to 12-in. depth, and remained relatively low thereafter throughout the 72-in. sampling depth. Data from this long-term study showed the optimum broadcast N rate was approximately 60 Ib N/acre applied on each crop grown in a W-S-F rotation with the exact rate depending on soil moisture, fertilizer, and crop prices, Yields from CT were comparable with RT on this nearly level upland soil but failed to meet the residue requirements mandated in conservation compliance plans, Poorer stands, increased weed competition, and drier soils resulted in generally lower yields from NT plots. Considering all factors, RT systems for dryland wheat and sorghum production are recommended on upland fertile soils in the west central Great Plains.
