• Authors:
    • Ulbrich, A. V.
    • Yada, I. F. U.
    • Lima, J. de
    • Rodrigues, B. N.
    • Fornarolli, D. A.
  • Source: Planta Daninha
  • Volume: 18
  • Issue: 2
  • Year: 2000
  • Summary: Field experiments, conducted during 1997/98 in Londrina, Parana, Brazil, bioassays and chromatographic analyses were conducted to investigate the effect of mulch (oat residues) on crop-weed competition and retention of imazaquin in no-till soyabean crop. Imazaquin was applied at 0, 75, 150 and 300 g/ha on 7000 and 14 000 kg/ha of oat residues and on soil without mulch. Twenty-four hours after imazaquin application, the field was irrigated and more samples were collected for bioassays and chromatographic analyses. The weed population consisted of Brachiaria plantaginea, Euphorbia heterophylla and Bidens pilosa. Oat residues intercepted 90% of the imazaquin before irrigation, indicating the potential of this herbicide in no-till system.
  • Authors:
    • Norwood, C. A.
  • Source: Agronomy Journal
  • Volume: 91
  • Issue: 1
  • Year: 1999
  • Summary: The dryland winter wheat (Triticum aestivum L,)-grain sorghum [Sorghum bicolor (L.) Moench]-fallow rotation is suitable for large areas of the U,S. Great Plains. High temperatures and potential evapotranspiration limit the number of other crops that can be grown, Sunflower (Helianthus annnus L.) is drought tolerant, but crops such as corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] are perceived to lark sufficient heat and drought tolerance for semiarid areas. A study was conducted near Garden City, KS, from 1991 through 1995 to compare yield and water uses of conventional tillage (CT) and no tillage (NT) corn, grain sorghum, sunflower, and soybean to determine if crops other than grain sorghum are suitable for dryland production. Conventional tillage (CT) and no tillage (NT) were included in a wheat-row crop-fallow rotation. Corn and soybean were similar in their depletion of soil water, as were sorghum and sunflower. Below a depth of 1.2 m, sorghum and sunflower removed the most water. Sunflower removed the most water nom the last 0.3 m of the profile and probably removed deeper water. Sorghum and sunflower removed an average of 19 mm more water from the 1.8-m soil profile than did corn and soybean. No-till increased yields of corn in 3 yr, of sorghum and sunflower in 2 yr, and of soybean in 1 yr, Corn had the greatest yield response to NT, averaging 31%. Average yields of corn were 25% higher than sorghum yields, whereas average yields of sunflower were 83% higher than soybean yields. Other crops can be successfully grown in the wheat-row crop-fallow rotation, but sorghum should occupy the most acres until the other crops have been tested under different climatic conditions.
  • Authors:
    • Peters, M.
    • House, R.
    • Lewandrowski, J.
    • McDowell, H.
  • Source: Agricultural Outlook
  • Year: 1999
  • Authors:
    • Walters, D. T.
    • Kessavalou, A.
  • Source: Agronomy Journal
  • Volume: 91
  • Issue: 4
  • Year: 1999
  • Summary: Use of a winter rye (Secale cereale L.) cover crop following soybean [Glyceine max (L.) Merr.] has been shown to reduce the soil erosion potential in a corn (Zea mays L.)-soybean rotation system, but little is known about the effect of rye on residual soil NO(3)-N (RSN). An irrigated field study was conducted for 4 yr on a Sharpsburg silty clay loam (fine, smectitic, mesic Typic Argiudoll) to compare crop rotation and winter rye cover crop following soybean effects on RSN under several tillage practices and N fertilization rates. Treatments each gear were (i) tillage: no-till or disk; (ii) rotation: corn following soybean/rye (Cbr) or soybean/rye following corn (BRc), corn following soybean (Cb) or soybean following corn (Bc), and corn following corn (Cc); and (iii) N rate: 0, 100, and 300 kg N ha(-1) (applied to corn). Rye in the Cbr/BRc rotation was planted in the fall following soybean harvest and chemically killed in the spring of the following year prior to corn planting. Each spring, before tillage and N application, RSN was determined to a depth of 1.5 m, at 30-cm intervals. The net spring-to-spring change in RSN between subsequent spring seasons was computed for each plot, and annual aboveground N uptake for rye, corn, and soybean were determined. Rye, rotation, N rate, and tillage significantly influenced RSN in the top 1.5 m of soil. The presence of rye (BRc) reduced total spring RSN between 18 and 33% prior to corn planting in 2 of the 3 yr, compared with the no-rye system (Bc), as rye immobilized from 42 to 48 kg N ha(-1) in aboveground dry matter. Recycling of N in high-yielding rye cover crop residues led to an increase in RSN accumulation after corn in the succeeding spring. Up to 277 kg RSN ha(-1) accumulated at high rates of N following corn in the Cbr rotation, compared with 67 kg RSN ha(-1) in the no-rye system (Cb) in 1992. Regardless of the presence of rye, significant accumulation of RSN occurred following corn in the rotation sequence, while RSN declined following soybean. Less RSN was found in the top 1.5 m of soil under continuous than rotation corn, and disking tended to increase NO(3)(-) accumulation in rotation systems at high rates of N application. Although RSN declines following a rye cover crop, the ready release of this immobilized N suggests that some N credit should be given, reducing N recommendation for corn following winter rye cover, to minimize potential NO(3)(-) leaching under corn-soybean/rye rotations.
  • Authors:
    • Cadrin, F.
    • Fan, M. X.
    • MacKenzie, A. F.
  • Source: Journal of Environmental Quality
  • Volume: 27
  • Issue: 3
  • Year: 1998
  • Summary: Nitrous oxide (N2O) produced from agricultural activities must be determined if management procedures to reduce emissions are to be established. From 1994 to 1996, N2O emissions were determined using a closed chamber technique. Continuous corn (Zea mays L.) at four N rates of 0, 170, 285, and 400 kg of N ha-1 was used on a Ste. Rosalie heavy clay (a very-fine-silty, mixed, nonacid, frigid Typic Humaquept) and a Chicot sandy loam (a fine-loamy, frigid, Typic Hapludalf). On two additional sites, a Ste. Rosalie clay and an Ormstown silty clay loam (a fine-silty, mixed, nonacid, frigid Humaquept) no-till (NT) and conventional tillage (CT); monocultural corn (CCC), monocultural soybean (Glycine max L.) (SSS); corn-soybean (SSC, CCS); and soybean-corn-alfalfa (Medicago sativa L.) phased rotations (SAC, CSA, and ACS) were used. Nitrogen rates of 0, 90, and 180 kg of N ha-1 for corn and 0, 20, and 40 kg of N ha-1 for SSS were used. Rates of N2O emission were measured from April to November in 1994 and 1995, and from mid-March to mid-November in 1996. Maximum N2O emissions reached from 120 to 450 ng of N m-2 s-1 at the Ormstown site to 50 to 240 ng of N m-2 s-1 at the Ste. Rosalie soil. Generally, N2O emissions were higher in the NT systems, with corn, and increased linearly with increasing N rates, and amounted to 1.0 to 1.6% of fertilizer N applied. The N2O emission rates were significantly related to soil denitrification rates, water-filled pore space, and soil NH4 and NO3 concentrations. A corn system using conventional tillage, legumes in rotation, and reduced N fertilizer would decrease N2O emission from agricultural fields.
  • Authors:
    • Bluhm, G.
    • Smith, J. L.
    • Mummey, D. L.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 70
  • Issue: 1
  • Year: 1998
  • Summary: Although agricultural soil management is the predominant anthropogenic source of nitrous oxide (N2O) to the atmosphere, little is known about the effects of alternative soil management practices on N2O emissions. In this study the NGAS model of Parton et al. (1996), coupled with a N and C cycling model, was used to simulate annual N2O emissions from 2639 cropland sites in the US using both no-till and conventional tillage management scenarios. The N2O mitigation potential of returning marginal cropland to perennial grass was also evaluated by comparing simulated N2O emissions from 306 Conservation Reserve Program (CRP) grassland sites with emissions from nearby cropland sites. Extensive soil and land use data for each site was obtained from the Natural Resource Inventory (NRI) database and weather data was obtained from NASA. The initial conversion of agricultural land to no-till showed greater N2O emissions per hectare than conventional tillage. Differences between the two tillage scenarios were strongly regional and suggest that conversion of conventionally tilled soil to no-till may have a greater effect on N2O emissions in drier regions. About 80% of the total emissions were from the Great plains and central regions mainly due to their large cultivated area. Croplands producing soy, wheat, and corn were responsible for about 68% of the total emissions with rice, cotton, and vegetable croplands having the greatest N2O flux (6.5-8.4 kg N2O-N ha-1 yr-1) under either scenario. Model simulations estimate that the agricultural lands in the US produce 448 Gg N2O-N y-1 under a conventional tillage scenario and 478 Gg N2O-N yr-1 under a no-till scenario. Model estimates also suggest that the conversion of 10.5 million hectares of cropland to grassland has a N2O mitigation potential of 31 Gg N2O-N yr-1, (8.4 Tg carbon equivalents yr-1). This value is similar in magnitude to many of the major greenhouse gas (GHG) emission-reduction strategies currently being considered to help meet US GHG reduction goals. Thus the GHG mitigation potential of this conversion is substantial and may be a viable strategy to help meet GHG reduction goals.
  • Authors:
    • Sarrantonio, M.
    • Wagoner, P.
    • Drinkwater, L. E.
  • Source: Nature
  • Volume: 396
  • Issue: 6708
  • Year: 1998
  • Authors:
    • Myers, R.
    • Pullins, E.
  • Source: American Journal of Alternative Agriculture
  • Volume: 13
  • Issue: 3
  • Year: 1998
  • Summary: The agronomic and economic performance of five alternative crops was assessed in comparison to the no-till wheat-soyabean double-cropping system prevalent in the southern Corn Belt of the USA. A field site was established in 1992 at the University of Missouri-Columbia and two further sites in Missouri were added in 1993. Amaranth, buckwheat, sunflower, and pearl millet were planted after the harvest of canola [rape] or wheat, or after fallow. Alternative double-crop grain yield, production costs, and net returns were compared with those of double-crop soyabean. Wheat yielded more than canola. Sunflower grain yields did not differ significantly after winter-crop treatments at any site. Yields of amaranth, buckwheat, soyabean, and pearl millet differed after winter crops at some sites. At three study yield levels, net returns were positive and greatest for double-crop wheat-amaranth, canola-amaranth, wheat-sunflower, and canola-sunflower systems. All double-crop systems except canola-pearl millet had positive net returns at median study yield levels. Low or negative net returns resulted from the combination of low yield and low price for some double crops. Canola was shown to be an economically feasible alternative to wheat in a double-cropping system for central and southern Missouri. Buckwheat and sunflower were shown to be agronomically and economically competitive alternatives to soyabean following either canola or winter wheat, with buckwheat most valuable in late-season planting conditions.
  • Authors:
    • Gordon, WB
    • Maddux, LD
    • Rice, CW
    • Omay, AB
  • Source: Soil Science Society of America Journal
  • Volume: 62
  • Issue: 6
  • Year: 1998
  • Summary: Increasing crop N use efficiency and minimizing environmental risk require an accurate assessment of N taken up by the crop from different sources. We conducted this study to: (i) compare the grain yields of corn (Zea mays L.) in monoculture and in rotation with soybean [Glycine max (L,) Merr,]; (ii) determine the contributions of N from fertilizer, soil, and legume residue to corn in the rotation; and (iii) compare N fertilizer recovery in monoculture and in rotation. Two existing (>10 yr) irrigated corn-soybean rotation areas in Kansas were used. The soils were Crete silt loam (fine, smectitic, mesic: Pachic Argiustolls) and Eudora loam (coarse-silty, mixed, superactive, mesic Fluventic Hapludolls). To trace the N through the rotation, N-15 microplots (2.4 m(2)) were established in the corn. Microplots also Here established in soybean to separately follow N-15 from roots + soil and shoots to corn. Crop rotation and fertilizer addition increased corn yield at both sites for two growing seasons. Averaged for 2 yr, the amount of N needed in the continuous corn to achieve yield equal to that in rotation with no N added was equivalent to 144 kg N ha(-1) in the Crete silt loam and 155 kg N ha(-1) in the Eudora loam, Response to N was greater on the Eudora loam, probably because of textural and organic matter differences. In the Eudora soil, significantly higher amounts of soil N Here taken up at harvest by corn in rotation, whereas, in the Crete soil, corn in monoculture took up significantly higher amounts of soil N, Corn plants recovered 3 kg N ha(-1) (3%) from soybean residue in the Eudora soil and 5 kg N ha(-1) (14%) in the Crete soil. The main value of legume residue appears to be longterm maintenance of soil N to ensure adequate delivery to future crops.
  • Authors:
    • Dick, W. A.
    • Jacinthe P. -A.
  • Source: Soil & Tillage Research
  • Volume: 41
  • Issue: 3-4
  • Year: 1997
  • Summary: Nitrous oxide (N2O) is an important atmospheric trace gas due to its involvement in the postulated global warming phenomenon and in the depletion of the ozone layer. Widespread concern has been triggered by recent reports of increased atmospheric N2O concentration. Since agriculture has been implicated as one contributor to that increase, a monitoring program was undertaken during the 1993 and 1994 cropping season (May-October) to evaluate the effect of several soil management practices on N2O emission from soil. Our results show that rates of N2O emission were generally near baseline levels during most sampling occasions. Major, but short-lived, fluxes of N2O were observed after rainfall events and during the days immediately following fertilizer application. It was during these times that most of the seasonal N2O loss occurred. An excellent relationship was found between seasonal N2O loss (y) and the maximum daily flux of N2O (x) during a season (y = -0.4x2 + 43.1x + 338, r2 = 0.89, P < 0.0001). The N2O emission data were log normally distributed for both years. Average daily emissions of N2O were 6.9 ± 6.3 g (range, 0.3 - 74.7 g) N2O---N ha-1 day-1 and 17.6 ± 10.5 g (range, 0.1-326 g) N2O---N ha-1 day-1 during the 1993 and 1994 seasons, respectively. Seasonal N2O---N losses were, in general, highest in the continuous corn (CC) (Zea mays L.) plots and lowest in the soybean (Glycine max L.) plots of the corn/soybean/wheat (Triticum aestivum L.)-hairy vetch (Vicia villosa Roth) rotation (CSW-V). Average N loss as N2O during a cropping season was between 0.6 kg (for the soybean crop of the CSWV rotation and ridge till treatment) and 3.7 kg N2O---N ha-1 year-1, (for the CC rotation and the chisel till treatment). Approximately 0.5-3% of the inorganic N fertilizer added was lost as N2O. Our data show that seasonal N2O---N loss from chisel-till plots were generally significantly higher than from no-till or ridge till plots.