Seed Size and Seeding Rate Effects upon Stand Density and Yield of Alfalfa¹

Abstract

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.

Influence of sowing rate on dry matter yield, plant density and survival of lucerne (Medicago sativa) under dryland and irrigated conditions

“…Sowing rate had the greatest effect on DM yield at the irrigated site with a range of 1-60 t ha" 1 between the lowest and highest sowing rates. Previous irrigated studies showed similar results in the sowing year; in Montana, DM yield increased 1-20 t ha" 1 with sowing rates ranging from 2-2 to 11-2 kg ha" 1 (Cooper et al 1979). In South Dakota, DM yield increased 1-10 t ha" 1 with sowing rates ranging from 4-5 to 17-9 kg ha" 1 (Hansen & Krueger 1973).…”

“…A quadratic effect may have been detected if higher sowing rates had been used. For example, other studies using higher sowing rates reported curvilinear responses in the first full-production year (Hansen & Krueger 1973;Cooper et al 1979). As observed for the sowing year, the slope of the line for the irrigated site was significantly (P < 001) lower than the slopes for the two dryland sites during the first fullproduction year (Fig.…”

“…Dry matter yield in the first year of full-production was not significantly affected by sowing rate at the forest site and decreased slightly with increasing sowing rate at the grassland site. Previous studies also indicated that the influence of sowing rate on DM yield is less in the second year under both irrigated (Hansen & Krueger 1973;Cooper et al 1979) and dryland conditions (Wakefield & Skaland 1965;Hansen & Krueger 1973). Unpublished work at Kamloops (B. Hubbard, personal communication) did not include sowing year yields but indicated that first full-production year DM yield increased by 0-60 t ha" 1 when the sowing rate was increased from 2-8 to 11-2 kg ha" 1 .…”

Shearing force of alfalfa stems as affected by seeding rate

“…This may be caused by non-uniform reduction in plant populations among cultivars. Plant losses were expected to be higher at higher seeding rates (Cooper et al 1979) because of winter injury, plant pests and diseases (Gossen et al 1994).…”

Peanut Tolerance to Paraquat as Influenced by Seed Size1

“…(5,9,11,16,18), sweet clover [Melilutus officinalis (L.) Lam.] (14), alfalfa (Medicago sativa L.) (7), and peanut (Arachis hypugaea L.) (13,17), In these studes larger seed size generally was associated with superior performance during emergence and subsequent development. However, this early-season benefit was not consistently reflected in yield.…”