• Authors:
    • McMahon, M.
    • Rajaram, S.
    • Sayre, K. D.
    • Ortiz-Monasterio, J. I.
  • Source: Crop Science
  • Volume: 37
  • Issue: 3
  • Year: 1997
  • Summary: The adaptation and performance of CIMMYT's bread wheat germplasm (Triticum aesttvum L.) under conditions of low N fertility have been questioned because they were developed under medium-high levels of N fertility. The objectives of this research were to (i) compare the performance of a set of tall vs. semidwarf cultivars developed by CIMMYT that were widely grown by farmers in the Yaqui Valley of Mexico at low and high N fertility, (ii) measure the genetic progress in grain yield and N use efficiency (NUE), and (iii) evaluate the contribution of N uptake efficiency (UPE) and utilization efficiency (UTE) to NUE. Ten wheat cultivars, two tall and eight semidwarf, produced by CIMMYT and released in the Yaqui Valley of Sonora, by the Mexican government from 1950 to 1985 were grown with 0, 75, 150, or 300 kg N ha-1 in a 3-yr field study at Ciudad Obregon, Sonora, Mexico. Genetic gains in both grain yield and NUE during 1950 to 1985 were 1.1, 1.0, 1.2, and 1.9% yr-1 on a relative basis or 32, 43, 59, and 89 kg ha-1 yr-1 on an absolute basis, when provided 0, 75,150, and 300 kg ha-1 N, respectively. Progress in NUE resulted in an improvement of both UPE and UTE. However, the relative importance of these two components was affected by the level of applied N. These results contradict the belief that modern semidwarf cultivars require more N than older cultivars. Instead, they respond more to N, which translates into higher economic rates and higher returns when N fertilizer is available.
  • Authors:
    • Unger, P. W.
    • Torbert, H. A.
    • Jones, O. R.
    • Potter, . N.
  • Source: Soil Science
  • Volume: 162
  • Issue: 2
  • Year: 1997
  • Summary: Limited information is available regarding soil organic carbon (SOC) distribution and the total amounts that occur in dryland cropping situations in semiarid regions. We determined crop rotation, tillage, and fertilizer effects on SOC distribution and mass in the semiarid southern Great Plains. A cropping system study was conducted for 10-years at Bushland, TX, to compare no-till and stubblemulch management on four dryland cropping systems: continuous wheat (CW) (Triticum aestivum L.); continuous grain sorghum (CS) (Sorghum bicolor [L.] Moench.); wheat/fallow/sorghum/fallow (WSF); and wheat/fallow (WF). Fertilizer (45 kg N ha-1) was added at crop planting to main plots. Subplots within each tillage and cropping treatment combination received no fertilizer. Ten years after treatment initiation, soil cores were taken incrementally to a 65-cm depth and subdivided for bulk density and SOC determination. The no-till treatments resulted in significant differences in SOC distribution in the soil profile compared with stubblemulch tillage in all four crop rotations, although differences were largest in the continuous cropping systems. Continuous wheat averaged 1.71% SOC in the surface 2 cm of soil compared with 1.02% SOC with stubblemulch tillage. Continuous sorghum averaged 1.54% SOC in the surface 2 cm of soil in no-till compared with 0.97% SOC with stubblemulch tillage. Total SOC content in the surface 20 cm was increased 5.6 t C ha-1 in the CW no-till treatment and 2.8 t C ha-1 in the CS no-till treatment compared with the stubblemulch treatment. Differences were not significantly different between tillage treatments in the WF and WSF systems. No-till management with continuous crops sequestered carbon in comparison to stubblemulch management on the southern Great Plains. Fallow limits carbon accumulation., (C) Williams & Wilkins 1997. All Rights Reserved.
  • 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.
  • Authors:
    • Peterson, G. A.
    • Lyon, D. J.
    • Halvorson, A. D.
    • Leavitt, S. W.
    • Paul, E. A.
    • Follett, R. F.
  • Source: Soil Science Society of America Journal
  • Volume: 61
  • Issue: 4
  • Year: 1997
  • Summary: The purposes of this study were to improve knowledge of regional vegetation patterns of C-3 and C-4 plants in the North American Great Plains and to use delta(13)C methodology and long-term research sites to determine contributions of small-grain crops to total soil organic carbon (SOC) now present, Archived and recent soil samples were used, Detailed soil sampling was in 1993 at long-term sites near Akron, CO, and Sidney, NE, After soil sieving, drying, and deliming, SOC and delta(13)C were determined using an automated C/N analyzer interfaced to an isotope-ratio mass spectrometer, Yield records from long-term experimental sites were used to estimate the amount of C-3 plant residue C returned to the soil, Results from delta(13)C analyses of soils from near Waldheim, Saskatchewan, to Big Springs, TX, showed a strong north to south decrease in SOC derived from C-3 plants and a corresponding increase from C-4 plants. The delta(13)C analyses gave evidence that C-3 plant residue C (possibly from shrubs) is increasing at the Big Springs, TX, and Lawton, OK, sites, Also, delta(13)C analyses of subsoil and topsoil layers shows evidence of a regional shift to more C-3 species, possibly because of a cooler climate during the past few hundreds to thousands of years, Data from long-term research sites indicate that the efficiency of incorporation of small-grain crop residue C was about 5.4% during 84 Jr at Akron, CO, and about 10.5% : during 20 yr at Sidney, NE, The C-14 age of the SOC at 0- to IO-tm depth was 193 yr and at 30 to 45 cm was 4000 yr; C-14 age of nonhydrolyzable C was 2000 and 7000 yr for these same two respective depths, Natural partitioning of the C-13 isotope by the photosynthetic pathways of C-3 and C-4 plants provides a potentially powerful tool to study SOC dynamics at both regional and local scales.
  • Authors:
    • Kissel, D. E.
    • Havlin, J. L.
  • Source: Soil Organic Matter in Temperate Agroecosystems: Long-Term Experiments in North America
  • Volume: 1
  • Year: 1997
  • Authors:
    • Voroney, R.
    • Vyn, T.
    • Janovicek, K.
  • Source: Agronomy Journal
  • Volume: 89
  • Issue: 4
  • Year: 1997
  • Summary: Research in Ontario, Canada in 1989, 1990, and 1995 evaluated no-till maize yield response to various preceding crops and examined whether in-row residue removal affected no-till maize response to rotation crops. The soil was an imperfectly drained loam (medium, mixed, weakly to moderately calcareous Typic Hapludalf). The preceding crops were: maize harvested for grain or whole-plant silage; hard red spring wheat; barley; red clover ( Trifolium pratense) cover crops, following barley, that were killed by spraying either 3 weeks (early-kill) or 1 day (late-kill) prior to sowing maize; canola [rape]; and soyabeans. In-row residue was either retained while sowing or cleared using planter-mounted, notched-disc row cleaners. Clearing in-row cover crop residue increased early-season maize growth and was associated with yield increases of 0.61 t ha -1 (8%) following early-killed red clover and 0.43 t ha -1 (6%) ( P = 0.10) following late-killed red clover. In 2 of 3 years, maize yields following early-killed red clover were similar to following soyabeans and greater than following grain maize, provided that in-row residue was cleared. Following the other crops, grain yield response to clearing in-row residue was smaller and less consistent over years. Preceding cropping affected early-season maize growth, with the largest plants at 5 weeks after sowing following either soyabeans or silage maize and the smallest following either red clover or grain maize. In 2 of 3 years, when preceding crop effects on grain yield were statistically significant, yields following either soyabeans or spring wheat were more than 1.05 t ha -1 (16%) higher than after grain maize. That yield increase occurred regardless of in-row residue placement. Removing maize stover by harvesting as silage increased maize yield by 0.86 t ha -1 (12%) over yield following grain maize. During 1995, maize yield following silage maize was less than after soyabeans, canola, barley, or wheat; thus, no-till maize yield response to rotation is not exclusively due to the presence of surface-placed stover. In-row residue placement and preceding cropping practices affected in-row soil temperature, but this could not totally account for the treatment effects on early-season maize growth and yields.
  • Authors:
    • Harapiak, J.
    • Lafond, G.
    • Johnston, A.
    • Head, W.
  • Source: Journal of Production Agriculture
  • Volume: 10
  • Issue: 3
  • Year: 1997
  • Summary: A research study was conducted in Saskatchewan and Alberta to determine the potential for precision side band application of partially liquified anhydrous ammonia (AA) at sowing. While AA reduced plant stand over that observed with urea for both wheat and canola [rape], no effect on grain yields of wheat were observed from seven field trials. The use of AA did not adversely affect the rate of wheat establishment as measured by main stem Haun stage or plant development as measured by number of root axes and frequency of tillers produced. With canola, a reduction in seed yield was observed at only one of the five trial sites. The lower canola yield reflects the N loss when AA is applied on clay soils. Loss of AA on clay and silty clay soils, which were wet at application, resulted in reduced crop N uptake and lowered N use efficiency relative to urea at one wheat and two of the canola trial locations. It is suggested that given adequate seed-fertilizer separation, partially liquified AA can be safely applied at sowing in a precision side band application. Soil conditions that are known to cause N loss on application of AA, in particular wet clay and silty clay soils, may benefit more from an alternative N source such as granular urea or solution N.
  • Authors:
    • Bauer, P. J.
    • Hunt, P. G.
    • Matheny, T. A.
  • Source: Journal of Production Agriculture
  • Volume: 10
  • Issue: 3
  • Year: 1997
  • Summary: Cotton (Gossypium hirsutum L.) production has dramatically increased in the Southeast, but the role of conservation tillage in doublecropped cotton systems has not been clearly defined. Therefore, from 1988 to 1994, we investigated doublecropped wheat (Triticum aestivum L.) and cotton on plots that had been in continuous conservation vs. conventional tillage since 1979. The experimental site wits located near Florence, SC, on a Norfolk loamy sand (fine-loamy, siliceous, thermic Typic Kandiudult). Conventional tillage consisted of multiple diskings and cultivations; surface tillage was eliminated for conservation tillage. Wheat yields were not significantly affected by tillage, but cotton yields were significantly higher for conservation tillage (P less than or equal to 0.01). Cotton planting dates ranged from 7 to 18 June, and 5 of the 7 yr had more than 145 frost-free days. Two years had crop failure because of early freezes, and a June drought prevented the planting of cotton in 1 yr. In the 4 yr with harvestable yields, seed cotton yields among the eight cultivars ranged from about 500 to 2200 and 300 to 1850 lb/acre for conservation and conventional tillage, respectively. The early maturing cultivar, 'Deltapine (DP) 20,' had the highest seed cotton yields with means of 1442 and 1123 lb/acre for conservation and conventional tillage, respectively Development of earlier maturing cotton and wheat cultivars will be important for this cropping system in the northern Coastal Plain portion of the Cotton Belt.
  • Authors:
    • Unger, P. W.
    • Alemu, G.
    • Jones, O. R.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 28
  • Issue: 1-2
  • Year: 1997
  • Summary: Soil and water conserving practices must be used to sustain dryland crop production in semiarid regions. In this 1994 study, we evaluated the effects of different cropping system and tillage method treatments on surface residue cover, organic matter content, aggregation, and water infiltration for a soil used for grain sorghum [Sorghum bicolor (L.) Moench] production in the United States Southern Great Plains from 1982 to 1994. Cropping systems were continuous sorghum (CS) and winter wheat (Triticum aestivum L.)-fallow-grain sorghum-fallow (designated WSF) and tillage methods were no-tillage (NT) and stubble mulch tillage (SMT). Treatments were CS-NT, CS-SMT, WSF-NT, and WSF-SMT. Surface residue cover before planting sorghum was >70% with CS-NT and WSF-NT, 29% with CS-SMT, and 12% with WSF-SMT. Surface cover after planting was approximate to 50% with both NT treatments, whereas amounts with other treatments were similar to those before planting. Soil organic matter contents (0- to 10-cm depth) were greater on CS than on WSF plots, but were not affected by tillage method in either cropping system. Water stable aggregation (0- to 2-cm depth) was greater with SMT than with NT in both cropping systems, but differences between cropping systems were not significant. Dry aggregates were smaller with NT than with SMT. Water infiltration was or tended to be greater on CS than on WSF plots, apparently because the WSF plots contained more water when infiltration was measured. Infiltration was not affected by tillage method, apparently because the greater amount of surface residues on NT plots counteracted the less water stable aggregates and smaller dry aggregates that had potential for reducing infiltration on the NT plots. This study indicates that no cropping system-tillage method combination treatment had a consistently beneficial or detrimental effect on soil conditions. In conclusion, both cropping systems (CS and WSF) and both tillage methods (NT and SMT) are suitable for conserving soil and water resources and, therefore, for sustaining dryland crop production in the semiarid United States Southern Great Plains.
  • Authors:
    • Kitchen, N. R.
    • Westfall, D. G.
    • Peterson, G. A.
    • Kolberg, R. L.
  • Source: Journal of Production Agriculture
  • Volume: 9
  • Issue: 4
  • Year: 1996
  • Summary: Crop N needs are not usually predicted based on cropping intensity or on tillage practice. However, N fertilizer requirements may increase dramatically as less fallow and less tillage are used in semi-arid regions of the Great Plains where summer fallow cropping is common. This long-term experiment was conducted to study the influence of N fertilizer rate, source/placement/timing (NSP), and crop rotation factors on the production of winter wheat (Triticum aestivum L.), corn (Zea mays L.), and grain sorghum (Sorghum bicolor L.), as well as their fertilizer N use efficiency (FNUE) for the initial years of conversion to no-till dryland farming. Research was conducted from 1987 through 1992 on two soils (Keith clay loam, a fine-silty, mixed, mesic Aridic Argiustoll and Weld loam, a fine-silty, mixed, mesic, Aridic Argiustoll) in eastern Colorado. Rotations included winter wheat-fallow (WF) and winter wheat-corn or grain sorghum-fallow (WCF). Wheat yields were similar between WF and WCF with adequate N application. Response to N fertilizer at lower rates was greater in WCF than WF because of its greater depletion of soil N. Corn production averaged 72 bu/acre with adequate N and required 1 lb/acre of N uptake to produce 1 bu/acre of grain. Current N fertilizer recommendations for wheat and corn were not adequate to insure maximum production under no-till management. Fertilizer placement significantly affected average annual rotational yield (40 to 70 lb/acre per yr difference) but application rate was more important economically. Grain biomass produced in each rotation per pound of total plant N uptake (GNUE) was 17 lb/acre per yr in WF compared with 29 lb/acre per yr for WCF. This 70% increase in average annual grain production of WCF over WF was accomplished with a 44% annual increase in fertilizer N application.