Characterization and modelling of water and mineral uptake in soiless cucumber: Fertigation management application

Fertigation management of hydroponics crops in commercial greenhouse is presently based on totally empirical rules for adjustment and control of the nutrient solution. This management generally results in an excess of applied water and fertilizers, with the consequent negative impact on the environment. Improving fertigation management, making a better use of available knowledge and models of water and mineral elements uptake, represents a priority issue for scientists.; Within this context, the main scientific goal of the present study was the characterization and analysis of the relations and interactions between the dry biomass accumulation of a cucumber greenhouse crop, its water consumption and its uptake of mineral nutrients. The applied objective is to formulate and validate from the collected experimental data the corresponding operational models of the processes that allow to describe and predict realistically the mineral uptake.; For reaching these objectives, an experimental protocol was first elaborated in order to characterize, during two crop cycles (winter and spring) and under a climatized glasshouse, the dynamics of dry matter accumulation, leaf area expansion, water consumption and mineral uptake. The interpretation of the experimental data by means of (i) growth analysis and (ii) the use of concepts such as radiation use efficiency and intercepted radiation, allowed to determine the general trends of the processes.; The second part of the study consisted in the elaboration and validation of different simplified models for estimating dry biomass production, leaf area index and transpiration. These models were use afterwards for deriving the mineral absorption, using empirical relationships established between these variables and the mineral uptake of a given element (N, P, K, Ca, Mg). The final choice of the models was based on the validation of the different modelling schemes, one in open circuit and the other with a closed system.; A useful data set of data is now available about the dynamics of mineral uptake by a cucumber crop at medium term (week), and its links with other processes such as biomass accumulation and water consumption. The data allowed to elaborate and validate operational models for predicting mineral uptake at a weekly interval, and their future use as tools for controlling and adjusting the nutrient solution in both open and closed systems.