Crop productivity in relation to interception of photosynthetically active radiation

Abstract

The attenuation of photosynthetic photon flux density (PPFD) in maize, sorghum, pigeonpea, and a maize/pigeonpea intercrop in the operational research watersheds at ICRISAT Center in India was measured on a weekly basis throughout the growing season. A 2-m high frame covering an area of 3 m 2 was designed to accommodate four manually-operated traversing quantum sensors for the measurement of PPFD. The interception of PPFD by the crop canopies was found to be closely related to the leaf area index. The plots of the regression relationship between dry matter for different crops and cumulative intercepted PPFD (grams of dry matter/einstein intercepted) were used to define the efficiency of light interception by crops. The maize/pigeonpea intercrop proved to be most efficient, followed by maize, sorghum, and pigeonpea. The Bouguer—Lambert Law was used to compute the extinction coefficient of PPFD of plant canopies. The interception of PPFD could be accurately predicted for sorghum and maize using this law, but in the case of pigeonpea the law was not satisfactory for accurate prediction of PPFD interception.