Radiation interception and radiation use efficiency of wheat and pea under different P availabilities

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: 250kgPha−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 2930gm−2, while in pea this variable fluctuated between 1005 and 1562gm−2. Wheat showed a higher (P<0.01) crop growth rate than pea and this variable was also affected (P<0.01) by the P supply. Averaged over the experiments, crop growth rate of wheat relative to P2 was decreased by 38 and 16%, respectively, in P0 and P1 treatments, while in pea these reductions were 35 and 9%, respectively. Above-ground biomass of both crops was highly related to crop growth rate. In turn, both crop growth rate and above-ground biomass of wheat and pea were highly related to IR. Responses of IR were the results of changes in LAI during the crop cycle affecting the fraction of intercepted radiation by the crop. Relative to the P2 treatment, the maximum leaf area index (LAI) of wheat and pea was decreased across experiments by P0 treatments on average by 52 and 49%, respectively. Regarding RUE, this trait was not affected (P<0.05) by the P supply in either crop suggesting that this variable is conservative under moderated P deficiency. However, wheat showed consistently higher RUE than pea, 1.63 vs 1.13gMJ−1, respectively, possibly owing to their differences in relation to the energetic cost of biomass synthesis.