Bamboo species, size, and soil water define the dynamics of available photosynthetic active solar radiation for intercrops in the Brazilian savanna biome

Bamboo has many potential applications in agroforestry systems. This study evaluated the photosynthetic active solar radiation available (PAR) to intercrops in three bamboo species as a function of estimated soil water content in the Brazilian savanna biome (tropical savanna climate with dry winters and rainy summers). The study was conducted from 2019 to 2021 (three to five years after planting), with clumps spaced at 8 × 5 m. PAR was measured below the bamboo at 0900, 1200, and 1500 h in the central, in-row, and inter-row positions. The estimated soil water balance was used to define the water available in the soil, which was correlated with the fraction of available PAR. The lowest value for the available PAR fraction occurred at the end of the maximum soil water content, being lower than 0.20 for Dendrocalamus asper and Dendrocalamus strictus and 0.80 for Guadua angustifolia. D. asper and D. strictus showed an inverse response rate of 0.50% and 0.75%, respectively, in the change in the available PAR fraction for each percentage change in the estimated mean soil water content 60 days prior to the PAR measurement date. G. angustifolia did not show any significant effect because of the smaller size of the culms and clump. The available PAR was correlated with estimated soil water content and species rate response. This information can be used to plan the cutting of bamboo culms to maximize the amount of PAR based on intercrop demand.