Plant Vigor and Yield of Perennial Cool-Season Forage Crops When Summer Planting Is Delayed

Abstract

The Cooperative Extension Service in most states recommends dates, in the late-summer or early-fall, when perennial coolseason forage crops should be planted. Planting after the recommended date generally results in less than optimum stand vigor and yield. For many reasons, farmers may wish to plant perennial forages after the recommended date. The objective of this research was to evaluate the performance of forages planted after the recommended latest date. Three perennial cool-season forage legume and grass species were planted on various dates during August, September, and October in 1991 and 1992 at two locations in Pennsylvania. Development and yield of plants was monitored for 1 year after planting. Plant height in lateNovember and percentage ground cover in the spring decreased as planting was delayed after 1 August. Each day planting was delayed after 1 August, total DM yield the following year declined by an average of 158 and 116 lb/acre for alfalfa (Medicago sativa L.), 105 and 71 lb/acre for red clover (Trifolium pratense L.), 76 and 28 lb/acre for birdsfoot trefoil (Lotus corniculatus L.), and 120 and 63 lb/acre for reed canarygrass (Phalaris arundinacea L.) in central and southern Pennsylvania, respectively. Orchardgrass (Dactylis glomerata L.) yields did not decrease at either location when planting was delayed from early- to mid-August. After mid-August, however, orchardgrass yield declined by an average of 92 lb/acre for each day planting was delayed. Perennial ryegrass (Lolium perenne L.) yields increased by over 1.0 ton/acre when planting was delayed from early-August to late-August. Daily delays in planting perennial ryegrass after late-August resulted in average yield reductions of 134 lb/acre. In general, planting perennial cool-season forage crops after 5 September in central and 10 October in southern regions of Pennsylvania resulted in ground cover judged too low for conservation purposes and produced yields that were too low for practical forage harvesting. Accumulated growing degree days (GDD, base 32°F) from 5 September and 10 October until the first killing frost (temperature ≤ 27°F) were approximately 1000 and 230, respectively