PRODUCTIVITY AND RADIATION USE EFFICIENCY OF SWEET SORGHUM (SORGHUM-BICOLOR (L.) MOENCH) CV KELLER IN CENTRAL SPAIN

Radiation use efficiency (RUE) is an extremely useful ratio in crop pr oductivity studies as it relates biomass production to solar radiation received by the crop. Cultivation of sweet sorghum For energy purpose s has generated great interest in Europe, and RUE can be a valuable ap proach to sweet sorghum yield forecasting. The aim of this work was to determine the RUE of sweet sorghum cv. Keller grown in non-limiting w ater conditions in Madrid (central Spain). Productivity in aerial biom ass and in sugars was studied during two crop cycles and the canopy ra diation interception was determined. Yields were estimated at 2.67 10( 3) g dry matter (DM) aerial biomass m(-2) and 835 g sugar m(-2), for t he following crop conditions: 122 days after emergence (DAE) cycle len gth, 1350 thermal time, 597 MJ intercepted photosynthetically active r adiation (PAR) m(-2). The canopy extinction coefficient was empiricall y determined as 0.57 for the interception efficiency. RUE, calculated as the slope of the regression of above-ground biomass and accumulated PAR(i), was estimated at 4.96 g DM MJ(-1). The energy efficiency of t he crop, energy content of the total biomass per unit of incident glob al radiation, was 2.3% for the crop season and 1.1% for the full year. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.