Early‐, Mid‐, and Late‐Spring Establishment of Switchgrass at Several Seeding Rates1

Abstract

AbstractConcerns of forage producers about seed cost and difficult stand establishment have limited the popularity and use of switchgrass (Panicum virgatum L.) as a summer forage alternative in the humid northern USA. ‘Cave‐in‐Rock’ switchgrass was seeded with atrazine (2‐chloro‐4‐ethylamino‐6‐isopropyl amino‐1,3,5‐triazine) for weed control in 1981 and 1982 on a Webster‐Nicollet soil complex (fine‐loamy, mixed, mesic, Typic Haplaquoll‐Aquic Hapludoll) at three seeding dates (April, May, and June) and five rates, ranging from 3.4 to 16.8 kg pure live seed (PLS) ha−1. Precipitation patterns primarily accounted for differences in mean seedling numbers of 27.8,13.0, and 28.0 seedlings m−1 of row for April, May, and June seeding dates, respectively. Mean tiller numbers of 118 m−1 in 1981 and 131 m−1 in 1982 suggest that tillering compensated for observed differences between years in initial seedling number, and producers should not hastily attempt to reestablish new seedings which initially appear to be marginal. Greater seeding rates increased seedling number, tiller number, and forage dry matter (DM) yields, but slightly decreased forage in vitro dry matter disappearance (IVDMD) and crude protein (CP). Seeding date had a greater effect than seeding rate on switchgrass forage yield and quality. Seeding‐year forage DM yields were 8.5, 6.5, and 4.5 Mg ha−1 for April, May, and June seedings, respectively. Forage IVDMD and CP concentrations were greatest for June (619 and 120 g kg−1, respectively) and least for April (524 and 84 g kg−1, respectively) seeding dates. Results suggest that highly productive switchgrass stands can be obtained during the establishment year with mid‐April to early May seeding dates at rates of only 3.4 kg PLS ha−1 when atrazine is used for weed control.