Can the agricultural AquaCrop model simulate water use and yield of a poplar short rotation coppice

We calibrated and evaluated the agricultural model AquaCrop for the simulation of water use and yield of a short rotation coppice (SRC) plantation with poplar (Populus) in East Flanders (Belgium) during the second and the third rotation (first two years only). Differences in crop development and growth during the course of the rotations were taken into account during the model calibration. Overall, the AquaCrop model showed good performance for the daily simulation of soil water content (R² of 0.57 to 0.85), of green canopy cover (R² > 0.87), of evapotranspiration (R² > 0.76) and of potential yield. The simulated, total yearly water use of the SRC ranged between 55 and 85% of the water use of a reference grass ecosystem calculated under the same environmental conditions. Crop transpiration was between 67 and 93% of total evapotranspiration, with lower percentages in the first than in the second year of each rotation. The observed (dry mass) yield ranged from 6.61 to 14.76 Mg ha−1 yr−1. A yield gap of around 30% was observed between the second and the third rotation, as well as between simulated and observed yield during the third rotation. This could possibly be explained by the expansion of the understory (weed) layer; the relative cover of understory weeds was 22% in the third year of the third rotation. The agricultural AquaCrop model simulated total water use and potential yield of the operational SRC in a reliable way. As the plantation was extensively managed, potential effects of irrigation and/or fertilization on evapotranspiration and on yield were not considered in this study. This article is protected by copyright. All rights reserved.