RADIATION INTERCEPTION, RADIATION USE EFFICIENCY AND GROWTH OF BARLEYCULTIVARS

Dry matter production and utilization of photosynthetically active rad iation (PAR) was studied for barley (Hordeum vulgare L.) in the field at Hermitage Research Station, Qld. In 1990, four cultivars (Gilbert, Tallon, Grimmett, Skiff) were sown at three times and grown with non-l imiting soil moisture. In 1991, soil moisture limitations were imposed on one sowing of the cultivar Grimmett. The radiation extinction coef ficient (k) was 0.41 +/- 0.02 and did not vary with cultivar, time of sowing or soil moisture availability. Radiation use efficiency (RUE) ( based on absorbed PAR and above-ground dry matter) did not change with time of sowing but did vary between cultivars. RUE was highest for Gi lbert (2.90 +/- 0.10 g MJ-1), while the other three cultivars averaged 2.60 +/- 0.04 g MJ-1. RUE of Grimmett was significantly lower in 1991 (1.48 +/- 0.07 g MJ-1) than in 1990 (2.60 +/- 0.07 g MJ-1), but soil moisture differences in 1991 did not significantly affect RUE. Several factors with possible links with RUE were examined and discussed. Of the variables examined those which showed the strongest relationships with RUE were average daily vapour pressure deficit and average daily minimum temperature.