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JUSTUS LIEBIG UNIVERSITY GIESSEN (2008)

Site specific irrigation : improvement of application map and a dynamic steering of modified centre pivot irrigation system

Hezarjaribi, Aboutaleb

Titre : Site specific irrigation : improvement of application map and a dynamic steering of modified centre pivot irrigation system

Auteur : Hezarjaribi, Aboutaleb

Université de soutenance : JUSTUS LIEBIG UNIVERSITY GIESSEN

Grade : Doctor of Agricultural Sciences (Dr. agr.) 2008

Résumé
The need for irrigation may differ between zones of a particular field due to the spatial variation of soil properties or the cropping of different plants on the same field. While moving irrigation systems apply water at constant rates, some areas of the field may receive too much water and others not enough. Therefore the key objectives of the present study were a) Delineation of irrigation management zones (IMZs) using sensor-based soil electrical conductivity (ECa) measurement with the aid of EM38 and VERIS 3100, b) Developing and evaluating a precision mobile drip irrigation (PMDI) and c) Evaluating wireless EnviroSCAN sensors and AMBAV-models to measure the soil moisture content. Soil electrical conductivity in 25 °C were collected using EM38 and VERIS 3100 at field capacity on a 16.6 ha non-saline field in the Federal Agricultural Research Centre, Braunschweig, Germany. 29 calibration points taken at a depth of 60 cm depth were located using differential GPS based on the soil electrical conductivity spatial variability pattern to determine the best sensor-based method to monitor total available water content. The second span of the centre pivot irrigation machine was modified to precision mobile drip irrigation and controlled for variable-rate water application. A better value of R2 between total available water content and the VERIS 3100 readings was found. The R2 value from VERIS 3100-sh data for TAWC estimation was maximally (0.77) and matched the TAWC data quite well, whereas R2 values to EM38-h and EM38-v data were low. Six irrigation management zones were identified based on fuzzy k-means unsupervised classification as an optimum number of irrigation management zones. It was concluded that under conventional uniform irrigation, irrigation management zones 1 and 2 were over-irrigated, whereas irrigation management zones 4, 5 and 6 were under-irrigated. The developed concept of pulse irrigation was a feasible and a viable technique. Water application was directly proportional to the fraction of time the valve was opened. AMBAV model as a cheap and reliable alternative instead of the expensive and imprecise EnviroSCAN sensor was capable of simulating soil moisture in the root zone of grass crops. Precision mobile drip irrigation was able to save about 70 % of energy and about 25 % of water in comparison with centre pivot irrigation system. Although PMDI causes more annual fixed expenses than CP irrigation, it has less total irrigation cost per hectare and year than centre pivot and drip irrigation.

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Page publiée le 11 mars 2009, mise à jour le 8 janvier 2019