Analysis of technical and environmental variability on irrigation requirements of fruit orchards, estimation of tree transpiration by gas flux analysis (CO2 y H2O)
- Autores: Enrico Nerilli Castellaneta
- Directores de la Tesis: Valvanera Zapata Ruiz (dir. tes.), José Fernando Ortega Álvarez (dir. tes.), Enrique Playán (dir. tes.)
- Lectura: En la Universidad de Castilla-La Mancha ( España ) en 2016
- Idioma: inglés
- Tribunal Calificador de la Tesis: Diego Sebastiano Intrigliolo Molina (presid.), José María Tarjuelo Martín-Benito (secret.), Kosana Suvocarev (voc.)
- Programa de doctorado: Programa Oficial de Doctorado en Ciencia e Ingeniería Agrarias
- Materias:
- Enlaces
- Tesis en acceso abierto en: RUIdeRA
- Resumen
The production of stone fruits has a relevant importance in the European agricultural sector. Aragon is one of the most important region of Spain for the cultivation of fruit trees, covering 38,000 ha. This cultivation needs to be supported by a permanent source of irrigation water constituted by the Ebro river. The trend of water consuming indicates that farmers do not cover the gross crop water requirements, but apply a sort of regulated deficit irrigation (RDI), often adopted without having an appropriate knowledge of crop physiology, phenology and water requirements. In order to contribute to a wider adoption of RDI, this work addressed the following main issues: 1) The assessment of spatial variability of soil and climate and its links to the irrigation network performance. 2) Comparison between the real water consuming and crop water requirement adopting RDI management in a commercial orchard. 3) The analysis of plant transpiration, crop evapotranspiration, photosynthesis and irrigation requirement in the different phenological stages. The Research has been carried out in a commercial orchards located in Caspe where are cultivated 225 hectares of stone fruits. The spatial variability of soil physical parameters and meteorology in the orchard was characterized, and its implication on crop water requirements was established. Three soil units were defined in order to evaluate the Readily Available Water inside the farm. For the Climate characterization were recorded all the climate variables adopting both, fixed and mobile meteorological stations. Irrigation depths applied during 2004- 2009 were analysed and compared with crop water requirements under standard and RDI strategies. Plant water status was also measured during two irrigation seasons using stem water potential measurements. Irrigation network analysis was performed using the measurements of flow rates and pressures of 10 selected control points placed on the network. For the analysis of plant transpiration, crop evapotranspiration, photosynthesis and irrigation requirement in the different phenological phase, the design of a prototype Open top chamber (OTC) adapted to adult trees was realised and tested during 2010 and 2011. The chamber has an inlet point where air is forced inside and an outlet point where air is expulsed. The systematic, alternate analysis of CO2 and H2O vapour concentrations at the inlet and outlet points permitted to characterize the plant photosynthesis and transpiration. The obtained gas exchange measurements (water vapour and CO2) were compared with the Eddy covariance system, for three days of October 2011 at a frequency of 30 minutes. Only 67% of the semi hourly periods could be used for this study, owing to limitations of both methods. Obtained results regarding the climate variability show that the wind speed variability reached 55% and determined 17% in reference evapotranspiration variability. An evolution of irrigation practices was observed during the studied years (2004-2009). In this period, the irrigation manager reduced water application by about 53 mm yr-1, while gross irrigation requirements decreased by 14 and 10 mm yr-1 for standard and deficit conditions, respectively. The comparison of temperatures and solar radiation permitted to conclude that temperature inside the OTC was 10% higher than outside (maximum difference of 6ºC) and that radiation inside the OTC was 20% lower than outside. The OTC measured concentrations of CO2 and H2O vapour adequately responded to the environmental inputs. Concerning the day time CO2 fluxes, the comparison of OTC and EC shows adequate correlation (r = 0.84), with OTC fluxes being 21% lower than EC measurements. During the night time, the EC plant respiration rate was higher than OTC measurements because the soil inside the chamber was covered with a plastic film. H2O vapour fluxes measured with both methods were well correlated (r = 0.83), with OTC values being 53% lower than EC values. Obtained results demonstrate that RDI implementation was limited by: 1) poor correspondence between environmental variability and irrigation system design; 2) insufficient information on RDI crop water requirements and its on-farm spatial variability within the farm; and 3) low control of the water distribution network. Improved control of the applied irrigation depths - as required to implement an RDI strategy - would require explicit characterization and exploitation of soil and climate variability and better-performing irrigation systems. Considering the gas exchange analysis there is margin for improving the OTC system by further automating some parts, such as data recording and analysis, and energy supply. The differences between OTC and EC results can be mostly attributed to the environmental conditions created by the presence of the chamber. Further research is needed to develop chamber prototypes showing lower environmental impact, resulting in similar conditions inside and outside the chamber.
