Tesis doctoral de Iván Francisco Garcia Tejero
Irrigated agriculture carries important and specific weight in the economic development of andalusia, with irrigated land constituting approximately 23% of the total agricultural surface area of spain, generating 57% of total yield and 60% of total agriculture employment in the country. However, today, water demand is higher than available water resources, forcing researchers to design new strategies for more efficient water use. Irrigation management intended to provide maximum output per unit of water (increasing water productivity) rather than per unit area, acquires special relevance for climatic conditions of south-western andalusia and in particular for sustainable citrus cultivation in the guadalquivir river basin. The present research shows the most relevant results reported in different experimental studies, in which different deficit-irrigation strategies have been applied in citrus: i) sustained deficit irrigation, ii) regulated deficit irrigation; iii) and low-frequency deficit irrigation. Special emphasis was placed on crop yield and its quality responses to deficit-irrigation strategies. On the basis of the experimental results, it was concluded that deficit-irrigation is a promising alternative technique for improving water-use efficiency, increasing productivity and minimizing the unnecessary waste of irrigation water. With regard to yield, the results proved highly dependent on the irrigation strategy rather than on the amount of water applied. Most deficit-irrigation strategies significantly affected the fruit-quality parameters, increasing the sugar content and titrable acidity. Also, depending on the strategy used, significant effects were found in some morphological parameters (e.G. Fruit diameter and rind) as well as the juice content. Periodic physiological measurements of stem-water potential and stomatal conductance during the irrigation periods were made for each treatment. These variables largely reflect the time course of the crop-water status. In addition, the integral of stress endured by the crop was estimated, which was found to be directly related to the final amount of water supplied. However, the treatments with similar levels of water stress accumulated over time, showed significant differences in yield and quality values, demonstrating the importance of irrigation strategy in citrus crops. In relation to the use of new tools for assessing the plant-water status, both dendrometry and infrared thermography significantly reflected the crop physiological status under water-stress situations, offering a good alternative for monitoring the water status and improving the irrigation scheduling for citrus orchards. Finally, with respect to water-use efficiency, it can be concluded that although deficit irrigation represents a significant gain in agronomic terms, financially, the increasing water restriction is not always related to high water-use efficiency. Therefore, a deficit-irrigation strategy is a key factor in maximizing fruit yield in terms of irrigation water. In general, given the climatic conditions of south-western andalusia, we conclude that irrigation applications in the range from 200 to 300 mm per year maintain optimal yield levels, with declines of less than 10% in comparison to well-watered trees while achieving significant water savings of 1,000-1,250 m3 ha-1. Thus, the results corroborate that deficit-irrigation techniques constitute a good alternative for managing limited water supplies at the same time as preserving the crop viability in physiological, agronomic, and financial terms under protracted water-shortage situations similar than those occurring in guadalquivir river basin (sw spain).
Datos académicos de la tesis doctoral «Deficit irrigation for sustainable citrus cultivation in guadalquivir river basin«
- Título de la tesis: Deficit irrigation for sustainable citrus cultivation in guadalquivir river basin
- Autor: Iván Francisco Garcia Tejero
- Universidad: Sevilla
- Fecha de lectura de la tesis: 28/10/2010
Dirección y tribunal
- Director de la tesis
- José Luis Muriel Fernández
- Tribunal
- Presidente del tribunal: Antonio Jesús Zapata sierra
- ignacio j. Lorite torres (vocal)
- José enrique Fernandez luque (vocal)
- Luis Andréu cáceres (vocal)