• 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.
  • Authors:
    • Merrill, S. D.
    • Black, A. L.
    • Bauer, A.
  • Source: Soil Science Society of America Journal
  • Volume: 60
  • Issue: 2
  • Year: 1996
  • Summary: In dryland cropping, no-tillage ran increase small grain crop growth compared with conventional tillage. Because root systems develop ahead of aboveground growth and are affected by soil environment, observation of root growth will show the mechanisms by which no-till enhances crop growth. Wheat (Triticum aestivum L.) was grown in a spring wheat-winter wheat-sunflower (Helianthus annus L.) rotation begun in 1984 on Temvik-aWilton silt loam (fine-loamy, mixed TS pic and Pachic Haploborolls) under conventional till (CT: spring dishing), minimal till (hlT: spring undercutting) and no-till (NT). Root length growth OULG) was measured by microvideo camera in pressurized-wall minirhizotrons, and soil water was measured by neutron moisture meter. Relative to CT, NT generally enhanced RLG more than aboveground growth; RLG averaged 65, 130, and 145 km/cm(2) in 1988, 1989, and 1990, respectively. In 1988, RLG was 37% greater than hlT (P < 0.1), with CT intermediate. In 1989, RLG was 40% greater in NT than in CT, with ILIT intermediate, and RLG in 1990 was 112% greater in NT than CT (no MT). Final biomass averaged 380, 1730, and 3090 kg/ha in 1988 through 1990, and was 36% greater, not significantly different, and 44% greater in NT than CT, respectively. Root penetration was shallow (1.1 m or less) in dry subsoil, but in each year roots penetrated to greater soil depths under NT than under hlT or CT. Amounts of stored soil water were generally not significantly different among tillages, but more water was depleted in 1990 under NT than CT. Cooler soil under NT (measured in 1989) and superior soil water conservation in the near-surface zone appear to confer a root growth advantage to the NT treatment.
  • Authors:
    • Franzluebbers, A. J.
    • Arshad, M. A.
  • Source: Soil Science Society of America Journal
  • Volume: 60
  • Issue: 5
  • Year: 1996
  • Summary: Changes in soil organic matter (SOM) pools during adoption of reduced (RT) or zero tillage (ZT) can influence soil physical properties, nutrient cycling, and CO2 flux between soil and atmosphere. We determined soil organic C (SOC), soil microbial biomass C (SMBC), basal soil respiration (BSR), and mineralizable N to a depth of 200 mm at the end of 3, 5, and 6 yr after implementation of tillage management on a Falher clay (fine, montmorillonitic, frigid Typic Natriboralf) near Rycroft, Alberta, in a canola (Brassica campestris L.)-wheat (Triticum Aestivum L.)-barley (Hordeum vulgare L.)-fallow cropping system. At the end of 6 yr, SOC was not different among tillage regimes and averaged 8.6 kg m−2. At the end of 3 and 5 yr, SMBC was not significantly different among tillage regimes, but at the end of 6 yr SMBC was 7% greater in RT and 9% greater in ZT than in conventional tillage (CT). Basal soil respiration and mineralizable N at the end of 6 yr were not different among tillage regimes following barley and averaged 2.7 g CO2-C m−2 d−1 and 5.0 g inorganic N m−2 24 d−1, respectively. However, BSR following fallow was 2.2, 2.5, and 2.6 g CO2-C m−2 d−1 in CT, RT, and ZT, respectively. Mineralizable N following fallow was 5.8 g inorganic N m−2 (24 d)−1 in RT and ZT and 7.3 g inorganic N m−2 (24 d)−1 in CT. At 0 to 50 mm, there was no significant increase in SOC at the end of 6 yr, a 17 to 36% increase in SMBC, and a 12 to 69% increase in BSR with ZT compared with CT, depending on rotation phase. Relatively small changes in SOM pools with adoption of conservation tillage may be attributable to the large amount of SOM initially present and the cold, semiarid climate that limits SOM turnover.
  • Authors:
    • Yoo, K. H.
    • Shirmohammadi, A.
    • Yoon, K. S.
    • Rawls, W. J.
  • Source: Journal of Environmental Science and Health . Part A: Environmental Science and Engineering and Toxicology
  • Volume: 31
  • Issue: 3
  • Year: 1996
  • Summary: A Continuous version of distributed parameter model, ANSWERS (ANSWERS 2000) was applied to a field-sized watershed planted to cotton in the Limestone Valley region of northern Alabama. The field was cultivated for three years with conventional tillage followed by three years of conservation tillage. Overall, the ANSWERS model simulated runoff and nutrient losses in surface runoff within an acceptable range for the conventional tillage system conditions in continuous simulation mode. But the sediment losses predicted by ANSWERS were initially on the order of fifteen times or more higher than measured regardless of tillage systems. In order to duplicate measured data, the sediment detachment coefficient of rainfall and flow had to be reduced for calibration. The model poorly predicted soluble nutrient losses for the conservation tillage system due to the model's weakness in representing the surface application of fertilizer under this practice. The model simulates only one soil layer, in which soil moisture, nutrient concentration, and soil characteristics are assumed homogeneous. Currently, the model does not consider vertical nutrient concentration variation in soil profile. During the conservation tillage system, corn stalk and the residue of a winter cover crop were spread on the soil surface. However, the model did not properly represent surface spreading of crop residue, thus the model was unable to consider the organic-nitrogen contribution from crop residue to the erodible soil surface. This resulted in poor prediction of sediment-bound TKN, especially for conservation tillage system.
  • Authors:
    • Madramootoo, C. A.
    • Mehuys, G. R.
    • Burgess, M. S.
  • Source: Agronomy Journal
  • Volume: 88
  • Issue: 5
  • Year: 1996
  • Summary: Reduced tillage is often recommended to decrease soil degradation and erosion associated with intensive row cropping. This study assessed the effects of different tillage and crop residue levels on corn (Zea mays L.) yields and related factors on a 2.4-ha site in southwestern Quebec over a 3-yr period. The soil, a Typic Endoaquent, consisted of sandy loam or loamy sand (mean depth, 46 cm) overlying clay, with subsurface drains at the 1.2-m depth. Treatments, begun in fall 1991, consisted of no-till (NT), reduced tillage (RT; dished in fall and spring), and conventional tillage (CT; moldboard-plowed in fall, dished in spring), in combination with two crop residue levels: no residue (-R; grain and stover removed at harvest, as for silage corn) and with residue (+R; stover left on site at harvest, as for grain corn). High crop-residue mulches resulted from NT+R (77-97% of soil surface covered), RT+R (45-92%), and at times NT-R (8-35%), potentially protecting the soil from erosive forces. Seedling emergence was delayed (1992, 1993) or partly suppressed (1994) in NT+R, and was also delayed in CT+R in 1992 and 1993, and in CT-R and RT+R in 1993. Final populations were affected only in 1993. In -R (silage) plots, yields with NT and RT were either greater (1992) or the same as their CT counterparts. On +R (grain) plots, grain, stover, and total yields were lower with NT in 1992 and 1994, due in part to difficulties in planting through the residue mulch, while RT reduced grain, stover, and total yields in 1992 and stover and total yields in 1993. Thus, for silage-corn production, NT and RT may offer economically viable alternatives to CT, although the use of dishing for a RT system provides almost no protective residue cover. In continuous grain corn, high residue buildup with NT and RT requires special attention to seeding technique or yield losses may result.
  • 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:
    • Schulbach, K. F.
    • Jackson, L. E.
    • Wyland, L. J.
  • Source: The Journal of Agricultural Science
  • Volume: 124
  • Year: 1995
  • Summary: Winter non-leguminous cover crops are included in crop rotations to decrease nitrate (NO3-N) leaching and increase soil organic matter. This study examined the effect of incorporating a mature cover crop on subsequent N transformations. A field trial containing a winter cover crop of Merced rye and a fallow control was established in December 1991 in Salinas, California. The rye was grown for 16 weeks, so that plants had headed and were senescing, resulting in residue which was difficult to incorporate and slow to decompose. Frequent sampling of the surface soil (0-15 cm) showed that net mineralizable N (anaerobic incubation) rapidly increased, then decreased shortly after tillage in both treatments, but that sustained increases in net mineralizable N and microbial biomass N in the cover-cropped soils did not occur until after irrigation, 20 days after incorporation. Soil NO3-N was significantly reduced compared to winter-fallow soil at that time. A N-15 experiment examined the fate of N fertilizer, applied in cylinders at a rate of 12 kg N-15/ha at lettuce planting, and measured in the soil, microbial biomass and lettuce plants after 32 days. In the cover-cropped soil, 59% of the N-15 was recovered in the microbial biomass, compared to 21% in the winter-bare soil. The dry weight, total N and N-15 content of the lettuce in the cover-cropped cylinders were significantly lower; 28 v. 39% of applied N-15 was recovered in the lettuce in the cover-cropped and winter-bare soils, respectively. At harvest, the N content of the lettuce in the cover-cropped soil remained lower, and microbial biomass N was higher than in winter-bare soils. These data indicate that delayed cover crop incorporation resulted in net microbial immobilization which extended into the period of high crop demand and reduced N availability to the crop.
  • 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:
    • 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.