Prediction of nitrogen, phosphorus and potassium uptake using a photothermal model

The prediction of nutrients uptake, in most cases, has been done with mathematical models that simulate, firstly, the dry matter production of the crop, so there is a lack of research to explain the dynamic of nutrients uptake related to climatic variables and leaf area index.
In this research, a dynamic model is proposed to predict nitrogen (Nup), phosphorus (Pup) and potassium (Kup) uptake by a tomato crop from a photo-thermal index (PTI). This model uses a similar approach to the one that uses RUE to simulate biomass production, only the effect of the normalized thermal time was included.
A parameter called efficiency of the use of the photo-thermal index ( ), was found with the lineal correlation between macronutrients and PTI, which is defined as the rate of change of nutrimental extraction respect to this new concept applied to greenhouse crops.
For this purpose, a hydroponic experiment was carried out in a greenhouse, with tomato cultivar ‘CID F1’ cultivated in autumn-winter season.
The air temperature and global solar radiation were measured with a HOBO weather station.
N content was determined by micro-Kjeldahl method, P content with yellow molybdovanadate procedure and K content was analyzed by atomic absorption spectrophotometry.
The leaf area index was measured with plant canopy analyzer (LAI-300, LICOR). The calibrated values for the parameter PTIUEN, P, K were: PTIUEN = 0.135 g N MJ m^‑2 d^‑1, PTIUEP = 0.0218 g P MJ m^‑2 d^‑1, PTIUEK = 0.311 g K MJ m^‑2 d^‑1, with values of goodness of fit (r=0.991, r=0.996, r=0.997). The trend of the nutrimental extraction curves was different when the concept “heat units” was used by logistic model.
This model involves variables that explain the growth and development of a crop and it has a very simple mathematical structure and predicts the absorption of Nup, Pup and Kup with excellent performance.
With the new model, the simulation of the nutrients uptake does not depend on the biomass estimation equation.

International Symposium on Advanced Technologies and Management for Innovative Greenhouses: GreenSys2019

A. Martinez-Ruiz, P. Sánchez-García, J. Pineda-Pineda, J.V. Prado-Hernández, A. Ruiz-García

dynamic model, nutrient optimization, leaf expansion, simulation, nutrient stress index

https://doi.org/10.17660/ActaHortic.2020.1296.61