The role of complementarity and selection effects in P acquisition of intercropping systems

Enhanced crop productivity by intercropping is commonly assumed to be driven by resource complementarity. However, relatively few studies have directly measured resource acquisition to assess potential mechanisms underlying enhanced performance of intercropping. A long-term field experiment with three P application rates (0, 40, 80 kg P ha(-1) yr.(-1)) and four maize-based intercropping systems was used to assess P acquisition and P fertilizer recovery efficiency (PRE) for three consecutive years. To identify underlying mechanisms, the additive partitioning method was applied to determine complementarity (CE) and selection effects (SE) in P acquisition of intercropping. Average P acquisition increased by 28.4% and 27.6% compared to their monocultures in faba bean/maize and chickpea/maize intercropping, respectively. However, P acquisition was generally not enhanced and even reduced in the last year in soybean/maize and oilseed rape/maize intercropping. Enhanced P acquisition was due to positive CE in faba bean/maize, and to positive CE and SE in chickpea/maize intercropping. Increased resource acquisition via CE and/or SE depended on the particular crop combination in intercropping systems. Application of the additive partitioning method to intercropping may help to identify underlying mechanisms of overyielding and carefully select crop combinations to enable more efficient resource use.