Abstract Above-ground biomass of crops can be expressed as the product between the cumulative intercepted radiation by the crop canopy (IR) and the radiation use efficiency (RUE) of the crop. The aim of the present study was to comparatively evaluate in wheat and pea these ecophysiological determinants of biomass under different P supplies at field conditions. Two field experiments were conducted in southern Chile combining two crops (wheat and pea) and three P supply levels (P0: 0; P1: 100 and P2: 250 kg P ha−1). In both experiments, the crop phenology of wheat and pea were slightly affected by P supply. Above-ground biomass of wheat ranged between 1352 and 2930 g m−2, while in pea this variable fluctuated between 1005 and 1562 g m−2. Wheat showed a higher (P