Water Productivity in a Mediterranean Semi-Arid Greenhouse District

Abstract

An irrigation performance analysis has been carried out in a horticultural greenhouse area located in the BCampo de Níjar^(Southern Spain) in order to assess its irrigation productivity. Irrigation water productivity indicators were calculated for a wide sample of crops over the course of two different study periods. These productivity indices were similar in average to those reported in other nearby greenhouse irrigation districts although their variability was very high. The overall productivity ratio (CYR) was 73.9 %. The low values for CYR were expected as irrigation water in this area has high salinity levels and low irrigation leaching fractions were applied. The influence of type of crop, greenhouse technology and agricultural season in the CYR values was analyzed. None of these factors had a statistically significant influence. A multivariate regression analysis was performed to model the crop yield as a function of several quantitative variables. The results showed that the most significant variable was the relative irrigation supply (RIS). Other variables that had an influence of the productivity were the length of the growing cycle in the case of tomato and the number of greenhouses per farm in the case of watermelon. Results of this work are useful as they highlight the weaknesses of the system and suggest possible measures in order to improve its productivity and sustainability.

Determining Reference Evapotranspiration in Greenhouses from External Climate

“…Transmissivity is usually a function of the type and age of the greenhouse material, the shading, and greenhouse geometry and orientation. Incident solar radiation also affects the daily transmissivity values because of variations in the sun's azimuth and atmospheric cloudiness (Castilla 2013;Sánchez et al 2015b;Von Zabeltitz 2011). The orientation of the greenhouse roofs and walls allowed more solar radiation to enter the greenhouses in winter than in summer (due to roof reflection).…”

“…Irrigated agriculture continues, globally, to be the primary consumer of blue water. Thus, precision irrigation is increasingly necessary for improving crop water productivity and maintaining the sustainability of intensive agricultural systems (FAO 2013;Sánchez et al 2015b). Greenhouse cultivation, an intensive agricultural production system, has been expanding recently in several regions of the world (Asia, the Mediterranean basin, central and northern Europe) (Castilla 2013;FAO 2013;Fernández et al 2010;Pardossi et al 2004).…”

“…Some authors have correlated weather variables inside greenhouses with outside weather variables and then calculated ET o inside the greenhouses using reference equations (Gavilán et al 2015;Sánchez et al 2015b). However, many farmers in developing countries do not have access to weather data, which may restrict their use of the Penman-Monteith equation.…”

“…Email: hj01@aub.edu.lb a factor related to greenhouse transmissivity (Fernández et al 2010;Gavilán et al 2015). Sánchez et al (2015b) used solar radiation measured outside the greenhouse and the day of the year to locally calibrate FAO ET oPM and calculate irrigation water requirements to assess irrigation adequacy in a broad sample of greenhouses in Spain. Local calibration is sometimes cumbersome, and more research is required in other areas in order to define how weather variables can be used to derive reference evapotranspiration within greenhouses.…”

Análisis de viabilidad y gestión del riego en invernaderos mediterráneos con energía solar fotovoltaica

“…Esto se ha realizado a partir de datos propios (Sánchez, Reca, & Martínez, 2015a,b) y de la información disponible en trabajos previos (Valera et al, 2014;Sánchez et al, 2015b). Se ha prestado especial atención a aquellas variables que condicionan de manera más significativa la demanda de energía del invernadero como son: el tamaño medio de la explotación, el número de invernaderos por explotación, las características de los sistemas de riego, y la tecnología asociada al invernadero.…”