Effects of different sowing date and the combined effects of sowing date and seed rates on the performance of wheat (Triticum aestivum L.)/faba bean (Vicia faba L.) intercropping system

Abstract Temporal complementarity in resource use is not well understood in wheat (Triticum aestivum) /faba bean (bean; Vicia faba) intercropping system. Results from a field experiment involving this intercrop combination indicate no benefit in resource use by delaying bean sowing date (BSD), as the total intercrop (wheat + bean) seed yields were reduced with delay in BSD. Averaged across wheat seed rate, total intercrop seed yields were 586 g/m2, 490 g/m2 and 422 g/m2 for simultaneous sowing of wheat with bean, 23 days delay in BSD and 37 days delay in BSD respectively. Although wheat seed yields were greater with delay in BSD, this had lesser effects on the overall total intercrop seed yields. Conversely, bean seed yields were greater the early the beans were sown and this had substantial impact on the total intercrop yield. This indicates that bean was the main determinant of variations in intercrop productivity. Biomass yields mainly determine seed yield variation in response to BSD for both wheat and bean. Biomass yields variations in response to BSD (and so seed yields) were attributed mainly to spatial complementarity in accumulated photosynthetically active radiation (PAR). For the combined effects of BSD and wheat seed rates, irrespective of the index used for evaluation, greatest intercrop performance was found when wheat and bean were sown simultaneously. Moreover, it was demonstrated that Area time equivalency ratio and crop performance ratio ‘time corrected' could be calculated using thermal time to evaluate intercrop performance.