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This experiment was conducted in a greenhouse in Vinces Los Rios (Ecuador). The aim of this work is to evaluate the relationship between different parameters and the nutrient demand of a greenhouse soilless cucumber production system in a tropical climate as well as to propose an empirical model for the design of the nutrient supply to the system. Considering the results obtained in this experiment, there was a high correlation between nutrient demands of the system with nutrient supplies and water uptake but not with leaf area index. With respect to the models, nutrient supplies and leaf area index were the most significant variables for nitrate (NO3−), chloride (Cl−) and manganese (Mn). For calcium (Ca2+), magnesium (Mg2+) and zinc (Zn), nutrients supply was the most significant variable and for the rest of nutrients [phosphates (H2PO4−), sulfates (SO42)−, potassium (K+), sodium (Na+) and iron (Fe)], the three variables assessed were significant. [ABSTRACT FROM AUTHOR]

The irrigation water consumption of a soilless cucumber crop under greenhouse conditions in a humid tropical climate has been evaluated in this paper in order to improve the irrigation water and fertilizers management in these specific conditions. For this purpose, a field experiment was conducted. Two trials were carried out during the years 2011 and 2014 in an experimental farm located in Vinces (Ecuador). In each trial, the complete growing cycle of a cucumber crop grown under a greenhouse was evaluated. Crop development was monitored and a good fit to a sigmoidal Gompertz type growth function was reported. The daily water uptake of the crop was measured and related to the most relevant indoor climate variables. Two different combination methods, namely the Penman-Monteith equation and the Baille equation, were applied. However, the results obtained with these combination methods were not satisfactory due to the poor correlation between the climatic variables, especially the incoming radiation, and the crop's water uptake (WU). On contrary, a good correlation was reported between the crop's water uptake and the leaf area index (LAI), especially in the initial crop stages. However, when the crop is fully developed, the WU stabilizes and becomes independent from the LAI. A preliminary model to simulate the water uptake of the crop was adjusted using the data obtained in the first experiment and then validated with the data of the second experiment. [ABSTRACT FROM AUTHOR]

In soilless culture, irrigation scheduling is an important and difficult task, as water and nutrients must be frequently and precisely applied, due to the reduced volume and low water holding capacity of most of the substrates. This paper describes an efficient control system for irrigation management of soilless culture based on an irrigation tray and a new adaptive hybrid automatic irrigation control algorithm. The proposed irrigation scheduling criteria are based on applying constant amounts in every irrigation application and variable timing as a function of crop water consumption. The control system analyzes the water balance in the control tray from the information provided by the sensors on the measured inputs and outputs of water from the tray. A hybrid algorithm composed of two stages is proposed. An estimation of the irrigation interval between irrigations is made by using an average daily crop water uptake pattern obtained from the feedback information of the tray. Short-term variations of the crop water uptake from the average daily pattern are adjusted by applying a proportional-integral (PI) controller. A field test was conducted to assess the performance of the proposed control system. The irrigation controller performed reasonably well as it fitted the leaching fraction for most of the irrigation events to the target value and its productive results were comparable to the ones obtained in a radiation-based control treatment. [ABSTRACT FROM AUTHOR]

In recent decades, the improvement of automated fertigation systems has gained great importance for the efficient use of water and fertilizers and for environmental sustainability. The objective of this study was to evaluate the performance of a new fertigation system compared to the fertigation-control tray system, which has been widely used in soilless cultures. A tomato crop (cv. Ramyle) was cultivated in coir crop units at the University of Almeria from November 2012 to May 2013. The fertigation-control tray method was used as a control (T0) and was compared to a new proportional integral derivative (PID) controlled method (T1), which was designed to maintain a constant leaching fraction. A plot design subdivided into three blocks was used, in which the drainage volume was automatically measured. The crop yield and some parameters related to fruit quality and size distribution were estimated. The results show a better distribution of the desired drainage fraction in T1. T1 had lower drainage electric conductivity (EC) values and significantly higher fertigation absorption. There were no improvements in the total crop yield or in most of the measured quality parameters. However, a significant improvement in the largest fruit size was recorded under the T1 treatment. [ABSTRACT FROM AUTHOR]