The study of models for better nutrient uptake estimation can help to improve integrated fertigation management, allowing enhanced water and fertilization use efficiency. The aim of this work was the development of empirical models that permit the prediction of the phosphorus (P) nutritional needs of Dieffenbachia amoena to increase P use efficiency in a recycled system. To achieve this, P uptake was correlated to climate parameters, such as temperature (T), vapor pressure deficit, and global radiation (Rg), and to growth parameters such as leaf area index (LAI). In addition, the influence of the N form supply (NO_3~--N or NH_4~+-N) on P uptake was studied. The trial was carried out with Dieffenbachia amoena 'Tropic Snow' plants growing in a recycled system with expanded clay as substrate. The crop was placed in an INSOLE buried solar greenhouse, with the plants supplied with equal amounts of N, differing in the percentage of the N form applied: Ta (100 NO_3~- 0 NH_4~+), Tb (50 NO_3~-: 50 NH_4~+) and Tc (0 NO_3~-: 100 NH_4~+). The N form applied to Dieffenbachia amoena 'Tropic Snow' plants affects P and N uptake, but it does not influence K uptake. Nitrogen and P uptake rates are higher in the plants supplied with NH_4~+ or NO_3~- + NH_4~+ than inthe plants provided with NO_3~- alone. The supply of a combination 50 NO_3~- : 50 NH_4~+ improves P use efficiency. The study also indicates the possibility of predicting the P uptake rate and P uptake concentration using the proposed models. Phosphorusuptake can be estimated with a model dependent on the LAI in the NO_3~--N treatments and on the LAI and Rg in the NH_4~+-N treatments. The P uptake concentration can be calculated with the P uptake, estimated through the previous model, and the experimental water uptake. This parameter would permit the nutritive solutions design, decreasing nutrient losses in open systems.
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