Interception of photosynthetically active radiation and radiation-use efficiency of wheat, field pea and mustard in a semi-arid environment

Abstract

Fractional ground cover, fractional PAR interception ( f), canopy extinction coefficient ( k) and radiation-use efficiency (RUE) for wheat, pea and mustard were examined in a field experiment conducted over 5 years in a semi-arid environment in Australia. Two crop sequences were compared: fallow–wheat–pea and mustard–wheat–pea. Significant periods of water stress occurred in some years. Complete ground cover was not achieved and f ranged to maxima of 0.77, 0.80 and 0.80 in wheat, pea and mustard, respectively. For wheat, fallow increased f under both average growing season and drought conditions, but pea PAR interception was not influenced by crop sequence. Estimates of k for wheat, pea and mustard were 0.82 (±0.05), 0.76 (±0.03) and 0.68 (±0.12), respectively. Estimated RUE (aboveground biomass) of 1.81 (±0.05), 1.52 (±0.05) and 1.92 (±0.12) g MJ −1 intercepted PAR for wheat, pea and mustard, respectively, was measured over the vegetative phase. Seasonal conditions had minimal impact on k and RUE, and RUE was generally lower than the maxima reported in the literature, but they were similar to others reported in comparable environments and matched predicted unstressed RUE for C 3 plants. This calls into question the application, in simulation models for crops that rarely reach full cover in such arid environments, of water supply or stress factors to RUE values established elsewhere on unstressed crops.