Biomass yields, radiation interception and radiation use efficiency as influenced by seed rate in a cereal/legume intercropping system

Abstract For a cereal/legume intercrop, yield improvement under well-watered conditions depends on greater interception and use of photosynthecally active radiation (PAR) by the intercrop. However, in wheat/faba bean (bean) intercropping system, the effects of sowing rate (sr) on productivity is not well investigated. Findings from five field experiments indicate that mostly the wheat biomass yields (BY) responses to sr were asymptotic. A maximum wheat sole crop BY of up to 1428 g/m2 was found in one of the experiments. Except in one experiment where bean sole crop produced BY of up to 1037 g/m2: bean produced lower biomass than the wheat sole crop. The total intercrop produced greater BY than the wheat sole crop in two of the experiments. Across the experiments, the maximum intercepted PAR was 711 MJ/m2 and 641 MJ/m2 for the wheat sole crop and bean sole crop respectively. In some experiments intercropping improved the PAR interception. Mostly, the maximum wheat sole crop RUE was lower than 3 g/MJ PAR: occasionally intercropping improved the estimates significantly. Intercropping was more efficient than sole cropping as indicated by the total intercrop crop performance ratio (CPR) values for the BY, which were greater than unity with a maximum value of up to 1.63 obtained in one of the experiments. Positive CPR values for intercepted PAR and/or RUE were found at the intercrop that produced greater biomass. This research indicates that wheat/bean intercropping system is beneficial because whilst wheat might use transmitted radiation to produce, bean might use direct irradiance to produce.