Simulating phosphorus dynamics between the soil and the crop with the STICS model: Formalization and multi-site evaluation on maize in temperate area

Soil-crop models are pertinent tools to study and manage phosphorus (P) in agroecosystems. However, P modeling is suffering a delay as compared to nitrogen and carbon. In this study, we extended the STICS model to simulate the P uptake and P feed-back by coupling it with a soil-plant P model. The paper aims at describing the P model and present the results showing the ability of the model to simulate contrasting P uptake and growth response pattern of maize submitted to different level of P inputs. in temperate area. The model simulates the soil P availability and the crop P demand, uptake, and partitioning. A major originality of this work is that it relies on soil solution P concentration and P sorption curves to simulate soil P availability, and critical P dilution curves to simulate crop P demand. We evaluated the model against a dataset coming from four field fertilization trials located at different site in mainland France. The trials consisted of fertilizing maize with a mineral fertilizer at three application rates (P0, P1, P2) which induced contrasted crop responses to P shortage. The model has shown great ability in predicting P uptake both dynamically and at the end of the cropping season for the entire dataset (EF >0.75). The model has satisfactory predictions of crop biomass accumulation (EF >0.5) and leaf area index. Considering each fertilization level separately, the evaluation has shown that the model had predicted the final P uptake of P1 and P2 treatments better than that of P0 treatment (EF of 0.74, 0.73 and 0.62 for P2, P1, and P0, respectively). The predictions made for the P0 treatment remained nonetheless satisfactory for both P uptake and plant growth. The good performance of the model is promising as it shows that the model is sufficiently robust to simulate maize P uptake across a range of soil P availability and P fertilization under contrasting temperate climatic conditions. Further validation on other crop species and soil and climatic conditions is discussed.