ALBERT

Description: The use of conservation tillage management in fallow cropping systems reduces soil erosion and improves soil quality. The economic benefits of these alternate tillage methods are less certain. This study examined the economic returns from reduced tillage methods on fallow using yield and input data from two experiments at the Agriculture and Agri-Food Canada Research Centre at Lethbridge, Alberta. One experiment was long-term study initiated in 1955 with eight treatments, the second was a 5-yr study with 15 treatments. Results from the 5-yr study indicated no difference in net returns between conventional and reduced tillage fallow systems. In contras, the long-term study net returns were highest for tilled systems and lowest for herbicide-only systems. The long-term study had a build-up of weeds that are difficult to control with herbicides alone. The resulting lower average yield and higher herbicide costs of the herbicide-only treatments in the long-term study accounted for most of the contrasting results between the two experiments. An economic evaluation of tillage practices requires the entire system to be evaluated, not just the tillage component. Key words: Economics, tillage, reduced tillage, conservation practices, weed control

Description: Conservation tillage practices such as no-till (NT) and conventional tillage (CT) with a heavy-duty cultivator can influence the physical properties of soils. This study was conducted to determine the effect of 24 yr of NT versus CT on the physical properties of a clay loam soil in southern Alberta. Physical properties quantified were bulk density (BD), mean weight diameter (MWD), plant-available water-holding capacity (PAWHC), saturated hydraulic conductivity (Ksat), soil water characteristic [θ(ψ)] and unsaturated hydraulic conductivity [K(ψ)] relationships, and pore-size distribution (PSD). Bulk soil samples and small soil cores (5-cm depth increments to 20 cm) were taken from CT and NT fields in 1992, and tension infiltrometer measurements were made in 1994. The results from this study are reported as general trends for the tillage fields. Statistical probability levels are not reported because of the unreplicated nature of the experiment, the limited number of sampling locations within each tillage field, and to a lesser extent, the different sampling times for CT and NT in 1992. Plant-available water-holding capacity was higher for the CT field (14.3%) than the NT field (10.8%), and a greater amount of water was held at a given water potential (−1500 to −1.5 kPa) for the former, indicating a higher potential for soil water conservation under conventional tillage. Geometric mean Ksat values (small soil cores) were higher for the NT field (18.20 × 10−6 m s−1) than the CT field (1.74 × 10−6 m s−1). The K(ψ) values (small soil cores) between −10 and −2 kPa were higher for the CT field than the NT field at the 0- to 5-cm, 10- to 15-cm and 15- to 20-cm depths, but values were higher for the NT field at the 5- to 10-cm depth. Near-saturated K(ψ) values (−1.5 to −0.3 kPa) of the surface soil, as derived from tension infiltration measurements in 1994, were higher for the CT field (2.43 × 10−7 m s−1) than for the NT field (6.09 × 10−8 m s−1). There was a greater percentage volume of larger pores (30–40, 40–67, 67–200, 〉200 µm) for the NT field than for the CT field, and there was a lower percentage volume of smaller pores (0.2–0.6, 0.6–4 µm) for the CT field than for the NT field. Differences in certain soil physical properties between CT and NT fields may be related to the lag time between the most recent tillage event and sampling for the CT field. Key words: Conservation tillage, heavy-duty cultivator, physical attributes, soil water, hydraulic conductivity, porosity

Description: The Ap horizons of two conservation tillage studies on Dark Brown Chernozemic soils in southern Alberta were sampled in 1986 following the fallow year. The first study, started in 1967, consisted of a wheat-fallow rotation under either no-till chemical fallow, blade-cultivate, or chemical fallow + blade-cultivate management. The second study, started in 1977, consisted of continuous winter wheat, winter wheat-barley-fallow, and winter wheat-fallow rotations under either no-till or conventional tillage management. Nine years of no-till continuous wheat and 19 yr of no-till in a wheat-fallow rotation both led to 40% of the dry aggregates being 〉 0.84 mm in diameter. The parameters selected helped to characterize differences in organic matter between soil tillage systems. Dehydrogenase and phosphatase activities were twice as high under no-till as under the blade-cultivate treatment. No-till also led to the largest monosaccharide accumulation in the soil. Carbohydrates, solvent-extractable organic matter, and chitin N were significantly higher in the 〉 0.84 mm diameter dry aggregates from the no-till treatment. The monosaccarides under the blade-cultivate regime were generally of microbial origin whereas those under the no-till regime were generally of plant origin. Key words: Water-stable aggregates, dry aggregates, enzyme activities, organic carbon, monosaccharides, fallow

Description: In 1991, up to 38 g L−1 hexazinone was found in 50% of surface runoff and 27% of groundwater samples at Lethbridge. No herbicides were detected in surface runoff from irrigation at Taber, but 2,4-D, bromoxynil, dicamba, mecoprop, MCPA and diclofop were found in 48, 34, 21, 16, 13 and 9%, respectively, of groundwater samples, and bromoxynil exceeded the Canadian drinking guideline (5.0 μg L−1) in 11% of samples. Key words: Herbicides, surface irrigation, surface runoff, groundwater

Description: Fallow continues to be a common agronomic practice on the southern Canadian prairies, but it has been associated with increased soil erosion and salinity and declining soil fertility. Field experiments were conducted at Lethbridge, Alberta, from 1987 to 1992 to determine the effects of various fallow treatments on weed control, conservation of surface crop residues, accumulation of soil water, and succeeding spring and winter wheat yields. Conventional cultivation during the fallow year with 168-cm sweeps controlled most spring-germinating weeds but did not adequately control overwintered flix-weed or downy brome. Repeated applications of glyphosate and 2,4-D effectively controlled most weeds. Paraquat did not control wild buckwheat or dandelion. Glyphosate alone often did not control wild buckwheat or Russian thistle. Treatments involving a combination of herbicides and tillage gave the best control of all weed species. Although not as effective in conserving surface crop residues as sole use of herbicides, many of the combined herbicide-tillage treatments maintained sufficient crop residue to keep the risk of soil erosion low. Soil water accumulation and succeeding wheat yields with the combined herbicide-tillage treatments were similar to, or greater than, those attained with repeated herbicides or repeated tillage. Management systems combining herbicides and tillage for fallow weed control may reduce costs and prevent or retard the development of herbicide resistance. Key words: Water conservation, herbicides, reduced tillage, soil erosion, stubble retention, weed control, wheat yield, no-till

Description: A field was artificially eroded by levelling in 1957 and then continuously cropped to barley for 7 yr. Subsequently, a wheat-fallow experiment was conducted from 1965 to 1979 to determine the effects of four fertilizer treatments and green manure (yellow sweet clover) on restoring the productivity to soil that had been "eroded" to various depths. After 22 yr and 14 crops, the productivity of the land from which soil was removed has been improved but not fully restored. Although green manuring with yellow sweet clover improved soil structure, wheat yields were not improved because of competition for soil moisture and poorer in-crop weed control in this part of the rotation. The addition of 45 kg N plus 90 kg P2O5 per hectare in each crop year to sites from which 8–10, 10–20, or 46 + cm of soil had been removed resulted in yield increases of 18, 46, and 70%, respectively, over the unfertilized check of each treatment; the average yields were 104, 91, and 70%, respectively, of the undisturbed, unfertilized (check) treatment. On "erosion" treatments where only 8–10 cm of soil were removed, 45 kg N plus 22 kg P2O5 per hectare were sufficient to restore the productivity. Precipitation apparently had a greater effect than fertilizer application on wheat yields. The loss of organic matter and associated soil structure characteristics seemed to be critical factors contributing to yield losses associated with soil erosion. These results show that it is more practical to use management practices that prevent soil erosion than to adopt the practices required to restore eroded soil. Key words: Soil erosion, topsoil loss, water-stable aggregates, soil organic matter, green manure, precipitation

Description: Complete loss of topsoil resulting from erosion or other causes generally results in reduced crop yield. To determine, under dryland conditions, the effect of loss of various amounts of soil and of various amendment practices suitable for use under a cereal production program on soil properties and crop yields, a field was artificially eroded during cut and fill of land-levelling in 1957. Continuous cropping to barley for 7 yr was followed by a wheat-fallow rotation for 22 yr. A continuous wheat experiment was conducted from 1987 to 1991 to determine the effects of five fertility amendments on restoring the productivity to soil from which 10–20 cm and 46+ cm of soil had been removed. In 1990, a below-average precipitation year, after 33 yr and 23 crops, yields from the unfertilized 46+ cm eroded field were only 44% of the yields from the uneroded field. However, with the increased precipitation in 1991 this value was 66%. A one-time topsoil amendment was beneficial in the earlier stages of the experiment, but lost its effect as cultivation mixed it into the "subsoil" over time. Plot treatments with annual applications of manure and high rates of fertilizer generally out-yielded the yields of the check plots of the uneroded treatment. Amendment with straw + fertilizer was not very effective. Soil, once lost, is non-renewable without amendments within the working lifetime of the producer. Key words: Soil erosion, manure, commercial fertilizer, topsoil soil, productivity

Description: Soil and crop management practices and their effects on surface residue levels can modify soil temperature. Our study investigated the effect of rotation, tillage and row spacing on near-surface (0.025 m) soil temperature under winter wheat (Triticum aestivum L.) in 1993-1994 and 1994-1995. The main treatment was winter wheat rotation: continuous winter wheat (WW); winter wheat-canola (Brassica campestris L.) (WC) or winter wheat-fallow (WF)] with tillage sub-treatments of conventional tillage (CT) vs. zero tillage (ZT) and row spacing treatments of uniform row (UR) vs. paired row (PR) spacing. From fall 1993 to spring 1994, ZT was cooler than CT by 1.2°C on the WC rotation, 1.1°C on WW and 0.4°C on the WF rotation. From fall 1994 to spring 1995, the magnitude of tillage differences was lower on all three rotations with ZT being cooler than CT by 0.1–0.9°C. The magnitude of the row spacing effect on soil temperature was less than that of the tillage effect. Extreme differences in soil temperature due to tillage were generally higher (1.0–4.9°C) on the WW and WC than the WF rotation (0.6–2.5°C) due to the presence of more crop residue. Results demonstrate that while ZT promotes overall cooler soils under winter wheat from fall to late spring, especially on continuously cropped (WW, WC) rotations, it also allows moderation of soil temperatures during extremely cold periods. Key words: Soil temperature, winter wheat, rotation, tillage, row spacing

Description: This study was conducted to compare the long-term (20 yr) effects of conventional tillage, minimum tillage and no-till on various soil-water related properties within the tilled layer (0–30 and 30–60 mm) and immediately below the tilled layer (90–120 mm) under a spring cereal-summerfallow rotation cropping system. Parameters measured included saturated hydraulic conductivity, saturation percentage, plant-available water-holding capacity, large pore porosity, bulk density, and infiltration rate of the soil. Tillage treatment effects on these soil properties in each of the four sampling periods were not significantly different. The confidence interval test showed some temporal changes in these soil physical properties, of which hydraulic conductivity was the most affected. In the summerfallow field, regardless of the previous cereal crops, the steady infiltration rate was significantly lower in the soil under conventional tillage than with that under no-till. The results indicate that the surface soil structure was most stable under no-till. In the fresh stubble field, the type of cereal crop had an effect on the infiltration rate of the soil. The mean infiltration rate was higher in the summerfallow field than in the fresh stubble field and also was higher in the fresh barley stubble than in the fresh wheat stubble. Except for infiltration rates, there is no significant advantage of one tillage method over the other with respect to the soil physical properties measured in this Brown Chernozemic clay loam soil. Key words: No-till, minimum tillage, hydraulic conductivity, bulk density, infiltration

Description: The optimum management system for winter wheat (Triticum aestivum L.) production in southern Alberta has not been adequately defined. A 9-yr (1978–1986) study was conducted to determine the effects of three rotations (continuous winter wheat, winter wheat–fallow and winter wheat–barley (Hordeum vulgare L.)–fallow), two tillage systems (conventional tillage, zero tillage) and two seeder types (hoe-drill, disc drill) on winter wheat growth, yield and water use. Continuous cropping to winter wheat was terminated after 4 yr because of a heavy downy brome (Bromus tectorum L.) infestation. Soil moisture reserves to 1.5-m depth fell to only 61% of that under the wheat–fallow rotation. Wheat grown in the wheat–barley–fallow rotation yielded on average 4% higher than that in the wheat–fallow rotation. Yields under zero tillage were significantly higher in 3 of the 9 study years, and slightly higher in 5 yr, due to better soil moisture conservation once the zero-tillage treatment was established for 2 yr. Zero tillage was most beneficial when precipitation at fall planting was less than normal. The hoe-drill provided more effective seed placement than the disc drill when surface soil conditions were dry at or soon after seeding. A management system which incorporates zero tillage (and preferably seeding with a hoe drill) into a 3-yr (wheat–barley–fallow) rotation is best suited for winter wheat production in southern Alberta. Key words: Wheat (winter), crop rotation, zero tillage, seed drill, soil moisture regime