Agronomic and chemical evaluation of selected sorghums as sources of pulp

Abstract

Nine accessions representing three sorghum species were grown at six locations in a single crop year to evaluate their potential as fibrous raw materials for pulp and papermaking. Evaluations were based on field yields, agronomic characteristics, and physical and chemical composition. Growing conditions caused considerable variation, but maturity, time of harvest, and harvesting methods also influenced composition. Preferred locations based on production of whole stalks (exclusive of roots) and of culms were Iowa, Indiana, and Georgia. The best productivity for several accessions exceeded 10 tons per acre (o.d.) for whole stalks and 6 tons per acre for culms. The mean content (for three locations) of crude cellulose in culms, ranged from 40.9 to 53.8% and of alpha cellulose from 25. 7 to 34. 7%; the level of pith ranged from 6.1 to 15.2%. Ash content in culms was 3% or less compared with 7% or more in leaves. Late-maturing PI 22983 7 and 229847 were consistently good yielders, but were chemically inferior to PI 177549 and 190579. Composition of PI 177549 was the most favorable, with a high proportion of culms to leaves and with crude cellulose content of 58.4% in culms (Georgia). In Iowa, the content of crude cellulose in culms of PI 229837 was equivalent to 3.40 tons per acre, and that of alpha cellulose was equivalent to 2.31 tons per acre. Accessions meriting further consideration are: PI 177549 (broom corn), 229837 and 229847 (kafir types), and 190579 (sorghum grass).