• Authors:
    • Lyon, D. J.
    • Baltensperger, D. D.
  • Source: Journal of Production Agriculture
  • Volume: 8
  • Issue: 4
  • Year: 1995
  • Summary: Downy brome (Bromus tectorum L.), Jointed goatgrass (Aegilops cylindrica Host), and volunteer cereal rye (Secale cereale L.) are winter annual grass weeds that are increasingly troublesome in the winter wheat (Triticum aestivum L. emend. Thell.)-fallow rotation areas of the western USA. Six dryland cropping systems-continuous no-till winter wheat, winter wheat-fallow with fall tillage, winter wheat-fallow with fail applied herbicide, winter wheat-fallow-fallow, winter wheat-sunflower-fallow, and winter wheat-prose millet-fallow-were compared for their effect on winter annual grass densities in winter wheat. Winter annual grass densities averaged 145, 4.4, and 0.4 plants/sq yard for the 1-, 2-, and 3-yr systems, respectively. Eradication of the winter annual grasses was not achieved with any of the systems. Dockage and foreign material levels in wheat grain were lower in 3-yr than in 2-yr cropping systems. Jointed goatgrass was the most persistent annual grass investigated.
  • Authors:
    • Mineau, P.
    • McLaughlin, A.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 55
  • Issue: 3
  • Year: 1995
  • Summary: Agricultural activities such as tillage, drainage, intercropping, rotation, grazing and extensive usage of pesticides and fertilizers have significant implications for wild species of flora and fauna. Species capable of adapting to the agricultural landscape may be limited directly by the disturbance regimes of grazing, planting and harvesting, and indirectly by the abundance of plant and insect foods available. Some management techniques, such as drainage, create such fundamental habitat changes that there are significant shifts in species composition. This paper considers the relative merits of conventional tillage versus reduced, or no-till farming, and reviews the benefits of rest-rotation grazing, crop rotation and intercropping in terms of maintaining wild species populations. There are a number of undesirable environmental impacts associated with fertilizer and pesticide usage, and in this paper we attempt to provide an account of the ways in which these inputs impact on biodiversity at various levels including plant, invertebrate, and vertebrate groups. Factors which are considered include the mobility, trophic interactions, persistence, and spectrum of toxicity for various pesticides. The ecological virtues of organic and inorganic fertilizers are compared, and the problems arising from excessive use of fertilizer are discussed. The findings in this review indicate that chemical fertilizer loadings must be better budgeted to not exceed local needs, and that pesticide inputs should be reduced to a minimum. The types and regimes of disturbance due to mechanical operations associated with agricultural activity may also be modified to help reduce negative impacts on particular groups of species, such as birds. For those plant and insect species which need to be controlled for agronomic reasons, the population decreases brought about by disturbance regimes may be desirable as a form of pest management. The prevalence of agriculture over such a large portion of the Canadian landscape means that it is important that we find solutions to conflicts that arise between agriculture and wild species. It is important to realize that the impact of agricultural inputs varies greatly among regions and species, and actual effects have generally not been investigated for many species in any one locality; while the focus of this review is on Canada, much Canadian-specific research is lacking, thus, this review also draws from relevant research done elsewhere.
  • Authors:
    • Rowell, A. L.
    • Weinrich, K. B.
    • Barnwell, T. O.
    • Jackson, R. B.,IV
    • Patwardhan, A. S.
    • Donigian, A. S.
  • Source: Soil Management and Greenhouse Effect
  • Year: 1995
  • Authors:
    • McIntosh, M. S.
    • Mulford, F. R.
    • Meisinger, J. J.
    • Decker, A. M.
    • Clark, A. J.
  • Source: Agronomy Journal
  • Volume: 87
  • Issue: 3
  • Year: 1995
  • Summary: Hairy vetch (Vicia villosa Roth) can fix N-2 for subsequent release to a corn (Zea mays L.) crop, but kill date effects on vetch N accumulation, soil water, and subsequent corn production have not been studied. A hairy vetch cover crop can deplete soil water through transpiration, but cover crop mulches can conserve soil water for no-till corn. In order to determine optimum spring kill date and corn fertilizer N (FN) rates, hairy vetch was killed early April, late April, or mid-May, followed by three corn planting dates and four FN rates (0, 45, 135, and 202 kg N ha(-1)). From early April to mid-May, hairy vetch aerial phytomass and N content increased significantly, from 2800 to 4630 and 96 to 149 kg ha(-1), respectively. Corn grain yields ranged from 5.2 to 10.1 Mg ha(-1) and were significantly greater following mid or late kill, compared with early kill of vetch, regardless of corn planting date or FN rate. Gravimetric soil water under mid- or late-kill vetch was often significantly greater than after early-kill vetch. We conclude that soil water conservation by late-killed vetch mulches had a greater influence on corn production than vetch spring water use. Optimum N production and water conservation occurred when vetch was killed the last week of April. Early-kill vetch sacrificed N production and minimized soil water conservation, resulting in reduced corn grain yield. Late kill did not add significant N benefits, but could deplete soil water or interfere with timely corn planting.
  • Authors:
    • Cote, D.
    • Voroney, R. P.
    • Angers, D. A.
  • Source: Soil Science Society of America Journal
  • Volume: 59
  • Issue: 5
  • Year: 1995
  • Summary: This study was conducted to determine the influence of tillage practices on the decomposition of corn (Zea mays L.) residues and turnover of soil organic matter (SOM). Measurements of {delta}13C were made of the whole soil, the microbial biomass, and two particle-size fractions (50 {micro}m) in soils that had been under corn production for 11 yr and from an adjacent meadow. Meadow-derived C in total SOM (0-24 cm) decreased under corn cropping at the same rate under all tillage treatments. Corn-derived C was evenly distributed with depth in the moldboard plow treatment and accumulated at the surface in the shallow, reduced-tillage treatments. The incorporation of corn residue C into SOM in the 0- to 24-cm layer was not significantly affected by tillage and was estimated to be {approx}41 g C m-2 yr-1, which represents {approx}30% of the corn residue inputs. Both the macroorganic matter (>50 {micro}m) and microbial biomass had a greater enrichment (up to 35%) in corn-derived C than either the whole soil or the microorganic matter (<50 {micro}m), indicating that these pools are important recipients of plant residue inputs. Nevertheless, the microorganic matter was also a significant sink for C input, acounting for {approx}50% of the total corn-derived C remaining in the surface (0-8 cm) soil. Under the conditions of this study, tillage practices influenced the vertical distribution of SOM and corn residues but had no detectable effect on SOM turnover and on the fate of corn residues when the whole Ap horizon was considered.
  • Authors:
    • Schepers, JS
    • Havlin, JL
    • Rice, CW
  • Source: Fertilizer research
  • Volume: 42
  • Issue: 1-3
  • Year: 1995
  • Summary: The objective of a rational N fertilization program is to account for the sources and fate of N while estimating crop N needs. Efficiency of N use will vary with cropping systems and N sources. Management technologies that affect N use efficiency include the amount of N applied, timing and placement of N fertilizer, and use of inhibitors. One of the main problems in making a fertilizer N recommendation is to account for the contribution of N mineralization to plant available N. Most laboratory procedures do not account for the environmental factors that affect N mineralization and only estimate the size of the mineralizable N pool. However, changes in soil moisture and temperature can dramatically affect the amount and rate of release of mineralized N. Field and modeling techniques are two possible techniques to estimate N mineralization. Field techniques can be divided into soil and plant approaches. Soil incubations in the field provide a quantitative approach while soil nitrate tests during the growing season provide a qualitative approach to estimating N mineralization. The plant is the ultimate integrator of N mineralization. Plant N uptake by an unfertilized crop can provide a quantitative approach with certain precautions. This approach may be costly, labor intensive, and site specific. Crop N uptake during the growing season can be estimated by measuring the tissue N content or using a chlorophyll meter. The chlorophyll meter measures the greenness of the plant and has been shown to be positively correlated to plant N status. Modeling may provide another option by including the factors that affect the rate of N mineralization from a known pool. The two most important variables include soil moisture and temperature. Realistic yield expectations and accounting for existing and projected amounts of available N can improve the accuracy of N recommendations.
  • Authors:
    • Sweeney, D. W.
    • Moyer, J. L.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 26
  • Issue: 1-2
  • Year: 1995
  • Summary: Legumes provide benefit in crop rotations, but data are limited on soil inorganic nitrogen (N) and soil strength responses to spring- or fall-seeded legumes as green manures for grain sorghum [Sorghum bicolor (L.) Moench] production on the prairie soils of the eastern Great Plains of the United States. With increased emphasis on conservation tillage, information is also needed on combining conservation tillage with the use of legume cover crops. This experiment was established to examine the effects of i) red clover (Trifolium pratense L.) and hairy vetch (Vicia villosa Roth.) as previous crops to grain sorghum compared with continuous grain sorghum, ii) reduced or no-tillage, and iii) fertilizer N rate on changes in soil inorganic N and soil strength. At two adjacent sites (Parsons silt loam; fine, mixed thermic Mollic Albaqualf) differing in initial pH and phosphorus (P) and potassium (K) fertility, soil nitrate-nitrogen (NO3-N) was as much as fourfold higher following kill-down of red clover or hairy vetch than following continuous grain sorghum. At the higher fertility site, soil total inorganic N [TIN: sum of ammonium-nitrogen (NH4-N) and NO3-N] shortly following kill-down of red clover exceeded TIN following hairy vetch by more than 35% and that with continuous grain sorghum by 110%; however, at the lower fertility site, the trend for soil TIN to be higher following legumes was not significant. Tillage did not affect soil NO3-N levels in the spring following legume kill-down. However, subsequent soil NO3-N levels under no-tillage tended to be higher in the spring, but lower in the fall than with reduced tillage. Increases in soil TIN by legumes and fertilizer were related to grain sorghum yield, but likely were not the only factors affecting yield. Legumes and tillage used in grain sorghum production may also provide other non-N benefits as suggested by soil penetration resistance measured at the end of the study.
  • Authors:
    • Unger, P. W.
  • Source: Journal of Soil and Water Conservation
  • Volume: 50
  • Issue: 3
  • Year: 1995
  • Summary: Crop residue management was chosen as a key practice to help control erosion on nearly 75% of the highly erodible land covered by conservation plans. This study determined the effects of treatments that involved retaining all residues on the surface (NT+Res), removing some residues at harvest (NT-ResH) or at planting (NT-ResP), and conventional tillage (ConvT) on soil water storage and use, and yields of continuous winter wheat (Triticum aestivum L.) produced with limited irrigation. Water storage between crops was greater with NT+Res (95 mm) and NT-ResH (100 mm) than with ConvT (79 mm), but soil water depletion was not affected by treatments. Grain yield was greater with NT+Res (4.56 Mg ha(-1)), than with ConvT (4.26 Mg ha(-1)) and NT-ResH (4.18 Mg ha(-1)), but straw yield was not affected by treatments. Grain and straw yield differed among crops. Continuous wheat production with limited irrigation resulted in an estimated 2.2 Mg ha(-1) of residues on the surface at planting with the NT-ResH and NT-ResP treatments. The initial amount was 9.0 Mg ha(-1) with the NT+Res treatment, and much of this remained on the surface at planting of the next crop. In all cases, the residue amounts provided considerably more (a minimum of about 70%) than the 30% surface cover usually required to control erosion on highly erodible land. Hence, use of limited irrigation and no-tillage can help producers meet the surface residue requirements established for their conservation plans for highly erodible lands in the southern Great Plains.
  • Authors:
    • Martin, R. J.
    • Marcellos, H.
    • Felton, W. L.
  • Source: Australian Journal of Experimental Agriculture
  • Volume: 35
  • Issue: 7
  • Year: 1995
  • Summary: Four experiments were commenced after a 1980 wheat crop, and a fifth after the 1981 crop, at different sites representing the major soil types of northern New South Wales in the 550-700 mm rainfall zone, to examine the influence of 3 fallow management practices [no tillage (NT); stubble retention after harvest, cultivation (SM); stubble burning after harvest, cultivation (SB)] on wheat production. Data considered in this paper cover the continuous wheat subtreatments of the 5 experiments (1981-90). Nitrogen applied at 50 kg N/ha in addition to the basal treatment was included as a treatment from 1986 to 1988. Across all sites and seasons, grain yields were in the order SB>SM approximate to NT, stubble retention having a greater effect than tillage. In some years at some sites, differences in grain yield and grain N yield were not significant. In others, when significant yield differences occurred, variations in grain yield and grain N yield were highly correlated with differences in soil N available for the crop. The data show that the influence of fallow management interacted with season and crop nutrition, and required long-term study for proper assessment.
  • Authors:
    • Lindemann, W. C.
    • Salazarsosa, E.
    • Gill, L. R.
    • Christensen, N. B.
  • Source: Agronomy Journal
  • Volume: 86
  • Issue: 2
  • Year: 1994
  • Summary: Soil nitrogen and organic carbon differences between no-till and conventional tillage systems are often dramatic and well documented, but these differences between no-till and stubble mulch tillage systems are more subtle. Our objective was to evaluate changes in soil inorganic N, organic N, organic C, surface soil moisture and grain yield on the southern High Plains as affected by stubble mulch and no-till tillage systems from 1988 to 1992. The cropping system was a sorghum (Sorghum bicolor (L.) Moench)-sorghum-fallow-wheat (Triticum aestivum L.) rotation conducted on a Pullman sandy clay loam (fine, mixed, thermic Torrertic Paleustoll) under dryland conditions near Clovis, NM. Tillage treatments were main plots and N fertilization treatments were subplots. Averaged over 5 yr and 37 sampling dates, the no-till treatment had 2.0 mg kg-1 less inorganic N, 40 mg kg-1 more organic N, and 617 mg kg-1 more organic C than the stubble mulch treatment. Although differences between tillage systems were generally small, they were most noticeable during sorghum planting and development. No-till unfertilized treatments often showed N deficiency symptoms during development. Nitrogen fertilization was more important than tillage system in determining sorghum and wheat yields in wet years. In dry years, N-fertilized stubble mulch treatments had the lowest yields. Since conversion to either stubble mulch or no-till in 1987, organic C levels under both systems have continually increased.