No abstract

Annual legume plowdown systems, which utilize fall regrowth for N contributions to rotational crops, have not been adapted to irrigated, intermountain areas of the Northern Rockies. Our objective was to evaluate plowdown systems using ‘Nitro’ alfalfa (Medicago sativa L.) and ‘Bigbee’ berseem clover (Trifolium alexandrinum L.). These two legumes were grown under five harvest management systems (zero to three forage harvests prior to fall plowdown of regrowth, or a standard three harvest system with no herbage plowdown) at two sites in western MT differing in soil characteristics. They were assayed for forage and plowdown production and for N benefits to ‘Clark’ barley (Hordeum vulgare L.; syn. H. distichon L.) for two subsequent years. Maximum herbage plowdown N was 125 to over 200 kg N ha−1 for berseem clover and 87 kg N ha−1 for alfalfa. A two‐harvest system resulted in 3.6 to 6.6 Mg ha−1 forage and 45 to 78 kg N ha−1 in herbage plowdown. Effects of plowdown were measured directly in increased soil N availability and correlated increases in N uptake in subsequent barley; benefits were expressed in increased grain yields and/or grain N concentrations and were apparent for two successive years at the site of lower native fertility. Alfalfa N benefits were superior to berseem clover, though disproportionate to herbage plowdown N quantities, possibly due to greater root and crown N in alfalfa. Where the management goal is primarily forage production with moderate benefit of plowdown N, berseem clover works well in a two‐harvest system; Nitro alfalfa is preferred where greater benefits of plowdown N are desired.

Legume seedlings from seed of different sizes compete with one another in pure seedings, usually to the detriment of smaller seedlings. We seeded variable rates of sized‐seed at Bozeman, Mont., to determine if less competition would permit lowering the seeding rate of alfalfa. We screened alfalfa (Medicago sativa L.) seed to small, medium, and large sizes weighing 160, 210, and 256 mg/100 seed respectively, and also made up a composite of the three sizes. We planted seed of each size at seeding rates of 1.1, 2.2, 4.5, and 9.0 kg/ha into a Bozeman silt loam (Agric‐Pachic Cryoboroll) soil in the field and measured seedling emergence and survival and yield in the year following seeding. Number of seedlings that emerged and number of plants that survived the second year were closely related to seeding rate. Percentage of planted seeds, resulting in mature plants from two separate plantings, decreased with increased seeding rate due to more intraplant competition. More seedlings emerged from small seed, or from the seed composite of all sized‐seeds, than from medium or large seeds. Seed size did not affect yield in the year of seeding or the year following. A seeding rate as low as 1.1 kg/ha at one location and 2.2 kg/ha at a second location gave maximum yield in the year following seeding. Our data showed no advantage of sizing seed. Seedling density was as good or better with small or composited seed as with large seed at the same seeding rate.

Sod‐seeding establishment of small‐seeded legumes and grasses has great potential for increasing forage production on previously non‐tillable lands. However, consistently successful stand establishment has been difficult to achieve via sod‐seeding. Even when adequate stands are obtained, they often lack the vigor associated with conventional establishment. A delay between the spraying of a non‐selective chemical for sod control and seeding with a minimum‐till drill has been suggested to improve sod‐seeding stand establishment. We conducted two field experiments to determine the optimum time interval needed between spraying glyphosate [N‐(phosphonomethyl) glycine] and sod‐seeding various grass and legume species with minimum‐till drills. The soils were classified as Cumulic Haploborolls and Ustic Tomfluvents in the first experiment and Udic Haploborolls and Typic Eutrochrepts in the second. A 14 day interval between spraying glyphosate and sodseeding alfalfa (Medicago sativa L.), alsike clover (Trifolium hybridum L.), and tall fescue (Festuca arundinacea Schreb.) with either the John Deere Powr‐till drill or the Melroe 701 No‐till drill was needed for adequate establishment at Laramie, Wyoming in 1978. In 1979, a 7 to 14 day spray‐plant interval was needed for adequate establishment of alfalfa, alsike clover, creeping meadow foxtail (Alopecurus mundinaceus Poir.), and meadow bromegrass (Bromus biebersteinii Roem. & Schult.) when seeding with the John Deere drill. When seeding with the Melroe drill in 1979, no differences among spray‐plant intervals were obtained for the same species. At Kalipell, Montana in 1978, a 28 day delay between spraying glyphosate and sod‐seeding alfalfa with the John Deere drill was needed for adequate establishment; whereas ladino clover (Trifolium repens L.) required a 14 day interval between spraying and seeding. In 1979 at Kalispell, a 28 day spray‐plant interval was needed for adequate establishment of alfalfa. Ladino clover establiihment was very poor for all spray‐plant intervals. Inadequate legume establishment was associated with slug (Agriolimax reticulatum Müller) predation. Spraying 28 days prior to seeding allowed sufficient time for grass desiccation. This permitted sunlight to penetrate the canopy which dried out the furrow thereby providing a less favorable slug environment.

Winterhardiness of winter barley (Hordeum vulgare L.) has not been improved greatly during the last 40 yr. Explanations range from a presumed lack of genetic variance for hardiness to a lack of effective selection in winter barley improvement programs. Previous research in Montana utilized recurrent selection in composite crosses containing male sterility to increase genetic recombination and improve winterhardiness. Composite Cross XXVI (CCXXVI) was subjected to winter selection pressure at various Montana locations from 1966 to 1984. This research evaluated the effectiveness of natural selection on winter survival and various agronomic and morphological traits in CCXXVI. Field trials at 10 Montana locations from 1985 to 1987 were used to measure winter survival and agronomic traits. Changes in morphological traits were studied in field and controlled‐environment studies. Natural selection appeared to favor taller and later‐heading plants. No significant change in population grain yield over time was detected in CCXXVI. Natural selection improved winter survival in CCXXVI, but the selection was not uniform over generations and maximum population hardiness occurred midway through the experiment. The hardiest CCXXVI generation was lower in winter survival than a hardy winter wheat (Triticum aestivum L.) and the same as a nonhardy winter wheat and a hardy winter barley cultivar. No significant correlation was found between seedling leaf width, seedling leaf number, or subcrown internode and mean winter survival. Shorter seedling leaf length was associated with enhanced winter survival.