RESPONSE OF US-72-1153 ENERGYCANE TO HARVEST MANAGEMENT

Lignocellulose materials can be readily produced under subtropical Flo rida conditions and converted to a variety of fuels through bioconvers ion methods. Optimal production of energy from biomass necessitates th e identification and management of high yielding plants. Energycane, S accharum sp. L. US 72-1153, was selected to study the influence of har vest treatments at plant heights of 4, 8, and 12 ft and mature in Octo ber (16 ft and in flower), and mature in December (16 ft and in flower ) on agronomic characteristics from 1986 to 1989. All treatments recei ved 50 lb acre-1 yr-1 P2O5 and 100 lb acre-1 yr-1 K2O in one applicati on and 300 lb acre-1 yr-1 N in split applications applied prior to the growth of each harvest. An additional October treatment at the mature stage received similar P2O5 and K2O but only 150 lb acre-1 N. Field-p lot layout was a randomized complete block with four replicates. Plant s repeatedly harvested at the 4-ft height produced a 4-yr average yiel d of 4.6 ton acre-1 dry biomass (DB) and decreased in DB yield 89% fro m year 1 to year 4. Plants harvested at the 12-ft height and at the ma ture stage in October and December produced a 4-yr average yield of 21 .5 ton acre-1 DB. However, these treatments also decreased 53% in DB y ield from year 1 or 2 to year 4 partly due to a 20% stand loss over th e 4-yr period. Leaf area index tended to increase quadratically to a h igh of 11.4 and 13.0 at 10 and 12 ft, respectively. Nitrogen content a nd in vitro organic matter digestion of biomass decreased 56 and 18%, respectively, from the vegetative (4-12 ft) harvest stages to the matu re stage over 4 yr. Total non-structural carbohydrates were generally higher (P<0.05) in crowns of plants harvested at maturity compared wit h any vegetative stage. Data indicate harvesting US 72-1153 energycane at 12-ft to mature stage resulted in high DB yields with extended sta nd longevity.