Low Intensity Harvest Management of Reed Canarygrass

forage K concentration was 12 g kg 1 (Brown et al., 1969). Timothy stands should persist over time with a High K grass forage increases risk of animal metabolic disorders, concentration of 15 to 18 g K kg 1 in headed spring and forage management of perennial grass grown under K-limiting soil conditions needs further study. Our objective was to evaluate growth and 12 to 16 g K kg 1 in regrowth, according to forage nutritive value, yield, and stand persistence of reed canarygrass Grant and MacLean (1966). Nitrogen fertilization of (Phalaris arundinaceae L.) under two-harvest management and low grasses initially increases forage K concentration if there availability of soil K. Three N and three K fertilizer treatments were is sufficient available soil K, but prolonged N fertilizaapplied to reed canarygrass for 5 yr at two sites in central New York tion of a grass stand will quickly deplete soil K and state with Niagara silt loam (fine-silty, mixed, active, mesic Aeric result in decreased forage K concentration (Cherney et Epiqualfs) and Williamson silt loam (coarse-silty, mixed, active, mesic al., 1998). Typic Fragiudepts) soil types. Reed canarygrass persisted under all Management systems that result in low forage K contreatments throughout the experiment, although K deficiency sympcentration are a prerequisite for grass forage fed to toms appeared in the high N, low K fertilizer combination. At the nonlactating dairy cows (Cherney et al., 1998). Based high N fertilizer rate, dry matter (DM) yield increased linearly (P 0.05) with increased K fertilizer rate, while K fertilizer did not influon results of Goff and Horst (1997), animal scientists ence yield in the absence of N fertilizer. Recovery of K fertilizer was generally suggest that forage for nonlactating dairy cows low and increased linearly (P 0.05) with increased N fertilizer rate contain less than 25 g K kg 1 DM to reduce the risk of from 6 to 42%. Soil test K increased to 59.9 mg kg 1 with no N high dietary K on animal health. High dietary K can fertilization and decreased to 34.9 mg kg 1 with 224 kg N ha 1. Under predispose pregnant cows to a number of disorders, high N fertilization with no K fertilization, grass forage K concentraincluding ketosis, metritis, retained placenta, and distion averaged 12 g kg 1 in the spring and 8 g kg 1 in the fall. placed abomasums (Beede, 1996). Our objective was to Sufficient yields of grass forage with reasonable quality and low conevaluate the effects of extensive harvest management centrations of K were possible through high N, low K fertility manageand low availability of soil K on reed canarygrass forage ment in a two-harvest system. yield, nutritive value, and stand persistence. MATERIALS AND METHODS P grasses will absorb K in excess of plant requirements, depending on the quantity of availReed canarygrass was established in 1992 on a Niagara silt loam (fine-silty, mixed, active, mesic Aeric Epiqualfs) soil with able soil K and the availability of other elements, partic0 to 2% slope in Ithaca, NY (Site 1). A second site was ularly N. Regions of the world, such as Europe, that established in 1993 on a Williamson silt loam (coarse-silty, rely heavily on grazing appear to have few concerns mixed, active, mesic Typic Fragiudepts) soil with 0 to 6% regarding plant K, and K often is not discussed in their slope in Ithaca, NY (Site 2). Both soils are classified as having literature concerning grass management (Beever et al., medium K supplying power, based primarily on their clay 2000). In contrast, in the USA, where stored forage is content. the primary dairy forage source, concerns regarding K Site 1 was fertilized with three rates of N fertilizer: 0, 168, content of dairy cattle diets are high (Horst et al., 1997). or 336 kg N ha , split applied before each of three harvests Incidence of milk fever in dairy cows fed a low calcium in 1993 and 1994. Site 2 received the same fertilization/harvest (Ca) diet was 0% for a diet containing 11 g K kg 1 dry regime in 1994 and 1995. Both sites were fertilized with P and K during the first 2 yr following the establishment year matter (DM), 36% for a diet containing 21 g K kg 1 according to soil test recommendations. DM, and 80% for a diet containing 31 g K kg 1 DM In 1995 previous N fertilized plots were split into three (Goff and Horst, 1997). High concentrations of soil-test subplots (2.13 by 6.08 m), with 0, 56 and 112 kg K ha 1 applied K in perennial grass fields are common on many dairy annually from 1995 to 2000. Previous N-fertilized plots refarms in the northern USA owing to preferential appliceived 0, 112 or 224 kg N ha 1 annually from 1995 to 2000, cation of animal manure on these fields. split applied at spring greenup and immediately after first On prairie soil with low available soil K concentraharvest. The same management sequence was applied to Site tion, no yield increase resulted from K fertilization of 2, starting 1 yr later than Site 1. Potassium fertilizer was applied smooth bromegrass (Bromus inermis Leyss.) (George as one annual early spring application from 1995 through et al., 1979). Timothy (Phleum pratense L.) yield was 1997, and then applied to both sites as one annual application following spring harvest in 1998 through 2000. significantly reduced under a 2-cut management when Broadleaf weeds were controlled by annual applications of either 2,4-D [(2,4-dichlorophenoxy) acetic acid] at 0.14 kg J.H. Cherney, Dep. of Crop and Soil Sci., 503 Bradfield Hall, Cornell a.i. ha 1 in the spring or dicamba [(3,5-dichloro-2-methoxy) Univ., Ithaca, NY 14853; D.J.R. Cherney, Dep. of Animal Sci., Cornell benzoic acid] at 0.11 kg a.i. ha 1 in the fall. From 1995 to 2000 Univ., Ithaca, NY 14853; and M.D. Casler, USDA-ARS, U.S. Dairy for Site 1 and from 1996 to 2000 for Site 2, plots were harvested Forage Research Center, Madison, WI 53706-1108. Contribution from Cornell Univ. Agric. Exp. Stn. Received 10 May 2002. *Corresponding Abbreviations: Ca, calcium; CP, crude protein; DM, dry matter; IVTD, author ([email protected]). in vitro true digestibility; K, potassium; N, nitrogen; NDF, neutral detergent fiber; OM, organic matter. Published in Agron. J. 95:627–634 (2003).