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This study investigates how temperature affects the response of capacitance sensors used to measure the dielectric permittivity of unsaturated soils. The dielectric permittivity is strongly correlated with the volumetric water content, an important variable in understanding water flow processes in unsaturated soils. Although capacitance sensors have been used widely in laboratory and field applications, they have only recently been used to characterize thermally induced water flow in unsaturated soils during geothermal heat exchange processes. To date, no studies have characterized the effects of temperature on capacitance sensor output for dense, compacted soils. This paper describes a calibration methodology that was used to isolate the effects of temperature on the response of capacitance probes in compacted soils having different initial conditions (i.e., compaction water content and dry density). It was observed that changes in temperature of 26°C can lead to an increase in the measured dielectric permittivity of up to 24 % with no changes in volumetric water content of the soil. In addition to defining a soil-specific calibration equation to relate volumetric water content and dielectric permittivity under ambient temperature conditions, a correction equation was proposed for temperature effects. The capacitance sensor's response to changing temperatures was observed to be sensitive to both the initial volumetric water content and the initial density of the soil, and parameters were defined for both of these terms in the correction equation.

An instrumentation technique is developed using embedded capacitive sensors to measure the thickness and evenness of coverage of a thin layer of dielectric thermal interface material (TIM) between two substrates. The technique requires an array of sensors embedded into one substrate, with an electrically conductive opposing substrate. Local capacitance measurements are sensitive to both local bond layer thickness and local voiding. We propose a means for using an array of capacitance measurements to interpret both bond layer thickness and local voiding at every sensor location. An algorithm is developed which reveals both characteristics from a single set of capacitance measurements. Experiments are conducted with thermal grease layers of different bond layer thicknesses and void distributions using a prototype system constructed on printed circuit boards. The thickness and void distribution are successfully mapped across the bond layer using the algorithm developed. The technique offers a sensing approach for in situ instrumentation of layers of thermal grease in a thermal test vehicle.

Τα συστήματα μοριακής διαγνωστικής έχουν έρθει στο προσκήνιο τα τελευταία χρόνια δίνοντας τη δυνατότητα για αυτοματοποιημένες, αξιόπιστες, γρήγορες και χαμηλού κόστους βιολογικές αναλύσεις. Τέτοια συστήματα χαρακτηρίζονται από σύνθετη λειτουργικότητα, η οποία συνδυάζει πληθώρα ενεργοποιητών και αισθητήρων που συνεργάζονται για την εκτέλεση βιολογικών πρωτοκόλλων. Με βάση τα πρωτόκολλα αυτά και με τη χρήση μικροροϊκών συστημάτων, τα βιολογικά δείγματα και αντιδραστήρια υποβάλλονται σε διάφορα στάδια επεξεργασίας. Κατόπιν της επεξεργασίας τους, τα δείγματα υπό μελέτη καταλήγουν πάνω στην επιφάνεια αισθητήρων, οι οποίοι είναι ειδικά ευαισθητοποιημένοι ώστε να ανιχνεύουν συγκεκριμένες βιολογικές αλληλεπιδράσεις ενδιαφέροντος και να αποκρίνονται μεταβάλλοντας αναλόγως ένα φυσικό μέγεθος, μετρήσιμο από ηλεκτρονικά κυκλώματα. Τα ηλεκτρονικά κυκλώματα ανάγνωσης των αισθητήρων αποτελούν ένα από τα κυριότερα τμήματα ενός συστήματος μοριακής διαγνωστικής, καθώς βάσει της απόκρισης αυτών προκύπτουν τα διαγνωστικά αποτελέσματα. Κατά συνέπεια, αναγνωρίζεται ο σημαντικός ρόλος που κατέχουν στη συνολική αναλυτική διαδικασία. Είναι απαραίτητο οι μετρήσεις που εκτελούν να χαρακτηρίζονται από μεγάλη ακρίβεια με υψηλή διακριτική ικανότητα για κάθε αισθητήριο στοιχείο. Ταυτόχρονα όμως, πρέπει να εξασφαλίζεται και η αξιοπιστία της μέτρησης σε επίπεδο βιολογικής διεργασίας. Σε αυτό το στόχο συντελεί η χρήση συστοιχιών αισθητήρων, με τις οποίες η ίδια μέτρηση μπορεί να εκτελεστεί παράλληλα σε πολλά στοιχεία και συνοδεύεται από μετρήσεις θετικού και αρνητικού ελέγχου. Πάνω στη συστοιχία μπορούν να εκτελεστούν και συμπληρωματικές μετρήσεις περισσότερων δειγμάτων, ώστε τα αποτελέσματα που εξάγονται να δίνουν μια πιο ολοκληρωμένη αναλυτική εικόνα. Υπό αυτό το πρίσμα, οι μεγάλου μεγέθους συστοιχίες αισθητήρων μπορούν να προσφέρουν βέλτιστα αποτελέσματα. Η παρούσα διδακτορική διατριβή επικεντρώνεται στα κυκλώματα ανάγνωσης συστοιχιών χωρητικών και ηλεκτροχημικών αισθητήρων, δύο ευρέως χρησιμοποιούμενων τεχνολογιών αισθητήρων. Η αρχή λειτουργίας των χωρητικών αισθητήρων βασίζεται στο γεγονός ότι οι αλληλεπιδράσεις βιομορίων που μελετούνται ασκούν δυνάμεις και παραμορφώνουν την ευέλικτη μεμβράνη πυριτίου που αποτελεί τον έναν οπλισμό ενός μεταβλητού πυκνωτή. Συνέπεια αυτής της παραμόρφωσης είναι η ανάλογη μεταβολή της χωρητικότητας που παρουσιάζει η μεμβράνη με το υπόστρωμα πυριτίου, μεταβολή που μετράται από το κύκλωμα. Στην περίπτωση των ηλεκτροχημικών αισθητήρων, η αντίστοιχη αλληλεπίδραση βιομορίων, με τη βοήθεια βιομορίων σήμανσης, προκαλεί τη μεταβολή της αγωγιμότητας μεταξύ των ηλεκτροδίων τους. Υπό ελεγχόμενες συνθήκες πόλωσης τάσης, το αναπτυσσόμενο ρεύμα που μετράται αντιστοιχεί στην εξέλιξη του βιολογικού φαινομένου. Ιδιαίτερη έμφαση δίνεται στις δυνατότητες κλιμάκωσης της εκάστοτε αρχιτεκτονικής ώστε να είναι επεκτάσιμη στην ανάγνωση πολύ μεγάλων συστοιχιών αισθητήρων με βέλτιστο τρόπο, διατηρώντας μικρές διαστάσεις για τα κυκλώματα ανάγνωσης. Συγχρόνως, εξασφαλίζεται με διάφορες στρατηγικές η ορθή λήψη μετρήσεων από κάθε στοιχείο, χωρίς την επίδραση από τα υπόλοιπα μέλη της συστοιχίας. Για την ανάγνωση συστοιχιών χωρητικών αισθητήρων σχεδιάστηκε και υλοποιήθηκε ολοκληρωμένο κύκλωμα σε τεχνολογία 0.35 μm, που στον πυρήνα της μέτρησης διαθέτει έναν ταλαντωτή χαλάρωσης με βρόχο υστέρησης ρεύματος. Υποστηρίζεται από προγραμματιζόμενες πηγές ρεύματος διέγερσης ώστε να καλύπτεται ένα ευρύ φάσμα χωρητικοτήτων για τους αισθητήρες. Το σύστημα πολύπλεξης που αναπτύχθηκε για τη διασύνδεση κάθε μέλους από τις συστοιχίες αισθητήρων πάνω στον πυρήνα ανάγνωσης μπορεί να διαχειριστεί πεπλεγμένες συστοιχίες, όπου τα στοιχεία είναι οργανωμένα με κοινές γραμμές και στήλες ηλεκτρικών επαφών στους οπλισμούς τους. Με αυτόν τον τρόπο είναι δυνατή η δημιουργία μεγάλων συστοιχιών με μικρό πλήθος ακροδεκτών διασύνδεσης. Η πρόκληση της ανάγνωσης τέτοιου είδους συστοιχιών έγκειται στις αλληλεπιδράσεις μεταξύ των στοιχείων, λόγω ανεπιθύμητων μονοπατιών στο ρεύμα φόρτισης του ταλαντωτή. Μία πρώτη αντιμετώπιση αυτού του προβλήματος διαφωνίας γίνεται με τη χρήση διακοπτών δύο καταστάσεων στις μονάδες πολύπλεξης, ώστε να ελέγχεται ο τρόπος με τον οποίο διεγείρεται το μετρούμενο καθώς και τα υπόλοιπα στοιχεία κατά τη μέτρηση. Με διαδοχικές μετρήσεις υπό διαφορετικές συνδεσμολογίες στους πολυπλέκτες και με κατάλληλη μαθηματική επεξεργασία, μπορούν να εξαχθούν ακριβείς μετρήσεις για την κατάσταση κάθε αισθητήρα της συστοιχίας. Η στατικότητα του συστήματος κατά τη διάρκεια των διαδοχικών μετρήσεων που είναι προϋπόθεση για το σωστό υπολογισμό των αποτελεσμάτων, βασίζεται στην ιδιαίτερα αργή εξέλιξη των βιολογικών φαινομένων στην επιφάνεια των αισθητήρων. Στα πλαίσια της διατριβής έγινε και ένας επανασχεδιασμός του κυκλώματος ανάγνωσης συστοιχιών, σε επίπεδο σχηματικού και φυσικού σχεδιασμού, του οποίου η λειτουργία επιβεβαιώθηκε με post-layout εξομοιώσεις. Σε αυτή την ανάπτυξη έγινε προσθήκη επιπλέον υπομονάδων και η βελτίωση των υπαρχουσών. Από τα κύρια χαρακτηριστικά αυτού του σχεδιασμού είναι μια μονάδα απομονωτή, που προσφέρει έναν δεύτερο τρόπο αντιμετώπισης του προβλήματος διαφωνίας μεταξύ των στοιχείων, αποτρέποντας το ρεύμα φόρτισης του ταλαντωτή να οδηγηθεί προς μη επιθυμητά στοιχεία. Επιπλέον, οι μονάδες ταλάντωσης που χρησιμοποιεί το επανασχεδιασμένο κύκλωμα είναι δύο, για ταυτόχρονη ανάγνωση αισθητήρων και ταχύτερη σάρωση μεγάλων συστοιχιών, με το εύρος του προγραμματιζόμενου ρεύματος να είναι μεγαλύτερο, καλύπτοντας μεγαλύτερο φάσμα αισθητήρων. Τέλος, αυτή η έκδοση του κυκλώματος έχει πιο αυτόνομο χαρακτήρα, με την ενσωμάτωση ενός υποσυστήματος σειριακής επικοινωνίας και ελέγχου. Για τη δεύτερη τεχνολογία αισθητήρων που καλύπτει η παρούσα διατριβή, των ηλεκτροχημικών αισθητήρων, σχεδιάστηκαν και υλοποιήθηκαν κυκλώματα ανάγνωσης συστοιχιών με χρήση διακριτών στοιχείων, καθώς επίσης και κυκλώματα με το βασικό πυρήνα μέτρησης να υλοποιείται σε ολοκληρωμένη μορφή με τεχνολογία 90 nm. Για τους σχεδιασμούς αυτούς έχει αναπτυχθεί η τεχνική της υβριδικής πολύπλεξης, βάσει της οποίας τα μέλη της συστοιχίας ομαδοποιούνται καταλλήλως, ώστε να επιτευχθούν οι απαιτούμενες επιδόσεις σε ρυθμούς δειγματοληψίας από το κύκλωμα ανάγνωσης, ενώ παράλληλα το μέγεθος του κυκλώματος παραμένει μικρό. Η υβριδική πολύπλεξη συνδυάζει διαδοχική ανάγνωση με παράλληλη ανάγνωση στοιχείων, κάνοντας χρήση πολυπλεκτών και κατάλληλου αριθμού υποσυστημάτων μέτρησης που επαναχρησιμοποιούνται για πολλά αισθητήρια στοιχεία. Η ιδιαιτερότητα που έχουν αυτού του τύπου οι μετρήσεις έγκειται στην απαίτηση για διαρκή πόλωση όλων των στοιχείων χωρίς διακοπή της ροής του ρεύματος μέσω αυτών, που καλύπτεται μέσω ειδικά διαμορφωμένων πολυπλεκτών δύο καταστάσεων οι οποίοι εξασφαλίζουν τις σωστές συνθήκες λειτουργίας. Επιπρόσθετες βελτιώσεις που παρέχει η υλοποίηση του κυκλώματος ανάγνωσης σε μορφή ολοκληρωμένου είναι η δυνατότητα εναλλαγής μεταξύ δύο τύπων κυκλωμάτων μέτρησης, με χρήση ενισχυτή διαντίστασης και ολοκληρωτή. Οι δύο τρόποι μέτρησης χρησιμοποιούνται συμπληρωματικά, ώστε να καλυφθεί μεγάλη δυναμική περιοχή λειτουργίας και γρήγορη απόκριση, αλλά και υψηλή ανάλυση, ανάλογα με τις απαιτήσεις κατά τη διάρκεια της πειραματικής διαδικασίας. Για το χαρακτηρισμό των κυκλωμάτων ανάγνωσης που αναπτύχθηκαν και για τις δύο τεχνολογίες αισθητήρων, έγιναν μετρήσεις με πρότυπα φορτία, καθώς και με συστοιχίες, για να εξαχθούν συμπεράσματα για την απόκρισή τους. Κατόπιν των ελέγχων καλής λειτουργίας των κυκλωμάτων και των μεθόδων που ακολουθούνται, πραγματοποιήθηκαν και επιτυχείς μετρήσεις βιολογικής σημασίας, που επιβεβαιώθηκαν από συστήματα αναφοράς. Molecular diagnostics systems have come to the forefront in recent years allowing for automated, reliable, rapid and inexpensive bioassays. Such systems are characterized by complex functionality, which combines variety of actuators and sensors that cooperate to perform biological protocols. Based on these protocols and using microfluidic systems, biological samples and reagents are subjected to various processing steps. Following this treatment, the samples under study are placed on the surface of sensors, which are functionalized to detect specific biological interactions of interest and respond accordingly by changing a physical quantity, measurable by electronic circuits. The sensor readout electronic circuits are one of the main parts of a molecular diagnostics system, as the diagnostic results are based on their response. Consequently, it is recognized that they hold an important role in the overall analytical process. It is necessary that the measurements they perform are highly accurate with high resolution for each sensor element. At the same time, the reliability of the measurement at a biological process level must be ensured. To this aim contributes the use of sensor arrays, with which the same measurement can be performed in parallel on many elements and accompanied by positive and negative control measurements. On the array, additional measurements of multiple samples can be performed, so that the output results give a more comprehensive analytical picture. In this light, large sensor arrays can provide optimal results. This thesis focuses on the readout circuitry for capacitive and electrochemical sensor arrays, two widely used sensor technologies. The operating principle of capacitive sensors is based on the fact that the interactions between the biomolecules under study exert forces and deform the flexible silicon film constituting an armature of a variable capacitor. The consequence of this deformation is a proportional change in capacitance between the film and the silicon substrate, a variation measured by the circuit. In the case of electrochemical sensors, the respective interaction of biomolecules, with the aid of labeling biomolecules, causes a change in conductivity between their electrodes. Under controlled bias voltage conditions, the resulting current that is measured corresponds to the progress of the biological phenomenon. Particular emphasis is given to the scalability potential of each architecture, so it can be optimally expanded for reading very large sensor arrays, maintaining small dimensions for the readout circuits. At the same time, through various strategies it is ensured that measurements of each element are properly acquired, without influence from other members in the array. To read out the capacitive sensor arrays an integrated circuit based on a 0.35 μm technology was designed and implemented, which at its measuring core uses a relaxation oscillator with a current hysteresis loop. It is complemented by programmable excitation current sources to cover a wide range of capacitances for the sensors. The multiplexing system that was developed to connect each member of the sensor arrays on the readout core can handle 'entangled' arrays, where the elements are arranged with common lines and columns of electrical contacts at their armatures. In this way it is possible to create large arrays with a small number of interface terminals. The challenge of reading such arrays lies in the interactions between the elements, because of side paths in the oscillator charging current. A first way to address this crosstalk problem is the use of two-state switches in the multiplexing units, in order to control the way in which the measured element is excited, as well as the other array elements, during measurement. Through successive measurements under different connection configurations on the multiplexers and appropriate mathematical processing, accurate measurements for the status of each sensor in the array can be obtained. The measured system can be considered static during successive measurements, which is a prerequisite for the correct calculation of results, due to the very slow progress of biological phenomena on the surface of the sensors. In the course of this thesis, a redesign of the array readout circuit was made, at a schematic and physical layout design level, the function of which was confirmed by post-layout simulations. In this development extra submodules were incorporated and existing ones were improved. One of the main features of this design is a buffer unit, which offers a second way of addressing the crosstalk problem between the elements, by preventing the oscillator charging current to excite undesirable elements. Furthermore, the redesigned circuit uses two oscillation units for simultaneous sensor readout and faster scanning of large arrays, with the range of their programmable current being greater, covering a larger spectrum of sensors. Finally, this version of the circuit has a more autonomous nature, by incorporating a serial communication and control subsystem. For the second sensor technology covered by this thesis, the electrochemical sensors, array readout circuits were designed and implemented using discrete components, as well as circuits with the basic measurement core being implemented in integrated form using a 90 nm technology. For these designs the technique of hybrid multiplexing was developed, whereby the members of the array are grouped appropriately to achieve the required performance in sampling rate from the readout circuit, while the size of the circuit remains small. Hybrid multiplexing combines sequential and parallel element reading, using multiplexers and the appropriate number of measurement subsystems that are reused for many sensing elements. The particularity of this type of measurements is the requirement for continuous biasing of all elements without interruptions in the current flow through them, which is addressed by specially configured two-state multiplexers that ensure the correct operating conditions. Additional enhancements offered by the implementation of the readout circuit in integrated form is the ability to switch between two types of measurement circuits, using a transimpedance amplifier and an integrator. The two modes of measurement are used in complement, to cover a wide operating dynamic range and fast response, and also high resolution, depending on the requirements during the experimental process. For the characterization of the readout circuits developed for both sensor technologies, measurements were made using standard loads, as well as arrays, to draw conclusions about their response. Following the validation of the proper operation of the circuits and methods used, successful measurements of biological significance were made, which were confirmed by reference systems.

Chufa (Cyperus esculentus L. var. sativus Boeck.) is an important vegetable crop in Valencia (Spain), where its tubers are used to produce a refreshing drink called 'horchata'. Water is relatively inexpensive, there are no data regarding the volumes of water used to grow chufa, and the irrigation water use efficiency (IWUE) has neither been determined. The aim of this research was to compare the productive responses of the chufa crop to two irrigation strategies (IS). The volumetric soil water content (VSWC) was monitored with capacitance sensors. Trends in VSWC were used to determine the in situ field capacity (FC), beginning each irrigation event when the VSWC reached either approximately 45% (H1) or 60% (H2) of the FC at a soil depth of 0.10 m. The experiments were conducted over three consecutive seasons. An area velocity flow module measured the water flow. The yields, the water volumes used, and the IWUE were calculated. Plants were periodically sampled and the harvest index and relative growth rate were determined. The yield was affected by the year and by the IS. The greatest yields were obtained with the H2 strategy (on average 2.18 kg m-2 for H2 vs. 1.94 kg m-2 for H1; p≤0.01), and the average tuber weight (ATW) was affected (p≤0.01) by the year and IS interaction. IWUE was affected by the year, and none of the considered factors affected the harvest index (p≤0.05). It can be concluded that maintaining a higher VSWC would increase both yield and ATW without affecting IWUE., La chufa (Cyperus esculentus L. var. sativus Boeck.) es el cultivo hortícola más representativo de L’Horta Nord de Valencia (España). Sus tubérculos se utilizan en la elaboración de la horchata. No existen datos del volumen de agua utilizado en el cultivo, ni de la eficiencia en el uso del agua de riego (EUAR). El objetivo de este trabajo fue analizar la respuesta productiva de la chufa a dos estrategias de riego (ER). El contenido volumétrico de agua del suelo (CVAS) fue monitorizado mediante sensores de capacitancia, La evolución del CVAS fue utilizada para determinar los valores de capacidad de campo (CC), iniciándose cada riego, cuando el CVAS a 0,10 m de profundidad alcanzaba valores de 45% (H1) o 60% (H2) de la CC. Los experimentos se realizaron durante tres campañas consecutivas. Se calculó el rendimiento, el volumen de agua utilizado y la EUAR. Las plantas se muestrearon periódicamente y se determinó el índice de cosecha (IC) y la tasa de crecimiento relativo. El rendimiento fue afectado tanto por el año como por la ER. Los mayores rendimientos se obtuvieron con la estrategia H2 (2,18 kg m-2 en H2 frente a 1,94 kg m-2 en H1; p≤0,01) y el peso medio de los tubérculos (PMT) fue afectado (p≤0,01) por la interacción año-ER. La EUAR fue afectada por el año y ninguno de los factores analizados afectó al IC (p≤0,05). Se concluye que con los niveles más elevados de CVAS se aumentaría el rendimiento y el PMT, sin afectar a la EUAR.

Orientadores: Roberto Testezlaf, Edson Eiji Matsura Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola Resumo: A subirrigação tem potencial para reduzir as perdas de água e nutrientes em sistemas de produção de mudas cítricas por permitir a recirculação e o reuso da solução nutritiva (SN), promover economia de fertilizantes e reduzir o seu descarte inadequado no meio ambiente. O objetivo desse experimento foi estabelecer o manejo hídrico e nutricional para produção de porta-enxertos (PE) de limão Cravo em tubetes, na fase de sementeira, usando mesas de subirrigação automatizadas por sensores capacitivos para monitoramento da umidade e controle da irrigação. Os tratamentos testados foram quatro conteúdos volumétricos de água (CVA) do substrato para acionamento da irrigação (0,12; 0,24; 0,36 e 0,48 m3 m-3), três concentrações de nutrientes na SN (25%, 50% e 75% da recomendação de adubação para PE em tubetes) e um tratamento adicional (sistema de produção do viveirista, com irrigação manual por chuveiro), arranjados no delineamento experimental inteiramente casualizado em esquema fatorial 4×3+1, com três repetições. A automação foi realizada conectando-se sensores capacitivos a um sistema de controle computacional formado por data logger, multiplexador e controladores de saídas, que acionavam bombas submersas de irrigação de acordo com valores de CVA estabelecidos como tratamentos. Ao longo do período experimental, houve monitoramento do CVA e do número de acionamentos da irrigação. Semanalmente, realizou-se a reposição e medição do volume total de SN aplicado, determinação de pH e condutividade elétrica (CE) dos substratos, avaliação da presença de pragas e doenças e do índice de área foliar (IAF). Aos 0, 30, 60 e 90 dias após o início do experimento, realizaram-se amostragens para análises de macro e micronutrientes nas plantas, substratos e SN, e determinação da altura das plantas, diâmetro de caule, massa seca de parte aérea e das raízes e área foliar total (AFT). Ao final do experimento, realizou-se análise fitopatológica para detecção de Phytophthora spp. no substrato e na SN, avaliação da diagnose nutricional visual e das perdas na produção, aparecimento de algas, determinação nas folhas das plantas da concentração intracelular de CO2 (Ci), transpiração (E), condutância estomática (gs), fotossíntese líquida (A) e da eficiência do uso da água (E.U.A.). Os resultados indicaram que os sensores foram eficientes no monitoramento da umidade e controle da subirrigação, sendo que os tratamentos com maior valor de CVA apresentaram maior umidade e número de acionamentos da irrigação (p < 0,0001). Houve aumento de aproximadamente 100% no volume total de SN aplicada à medida que se elevaram os valores de CVA a cada 0,12 m3 m-3 (p < 0,0001), decréscimo do pH e aumento da CE no substrato dos tratamentos com maior concentração de SN e maior CVA para acionamento da irrigação (p < 0,0001). As plantas apresentaram aumentos significativos do IAF, altura, diâmetro de caule, massa seca de parte aérea e das raízes e área foliar total (AFT) (p < 0,0001) à medida que os níveis de SN e CVA aumentaram. Houve resposta significativa aos diferentes tratamentos de SN e CVA de acionamento para concentração de nutrientes no substrato e na SN dos reservatórios de 121 L e para o teor de nutrientes na parte aérea e sistema radicular. Os tratamentos com CVA de 0,12 m3 m-3 promoveram a morte de diversas plantas por estresse hídrico. Os valores de Ci, E, gs, A e E.U.A. foram significativamente maiores nas plantas com maiores concentrações de SN e valores de CVA (p < 0,001). O tratamento com a concentração de SN 50% e CVA de 0,48 m3 m-3 promoveu maior crescimento em altura, diâmetro, massa seca e área foliar total dos PE de Limão Cravo. A subirrigação permitiu a antecipação no período de transplantio para realização da enxertia, possibilitando um ciclo de cultivo extra no viveiro por ano. O período de retorno da substituição do sistema convencional de irrigação manual por chuveiros obtido somente com o valor economizado pela redução do uso de mão de obra, redução da concentração de SN para 50% e eliminação do descarte de fertilizantes foi de 5,6 anos Abstract: Subirrigation has the potential to reduce water and nutrients losses in citrus seedlings production systems due to the nutrient solution (NS) recirculation and reuse, promoting fertilizer savings and the reduction of its improper disposal into the environment. The objective of this study was to establish the water and nutritional management for Rangpur lime rootstock production in cone-tainers at the sowing stage, using subirrigation benches automated by capacitance sensors to monitor moisture and control irrigation. The applied treatments were four substrate volumetric water content (VWC) to trigger irrigation (0.12, 0.24, 0.36 and 0.48 m3 m-3), three nutrient concentrations of the NS (25%, 50% and 75% of the fertilizer recommendation for citrus rootstocks production) and an additional treatment (nursery production system with manual irrigation using a shower), in a completely randomized experimental design with three replications in a 4×3+1 factorial. Automation was accomplished by a capacitance sensor connected to a data logger, a multiplexer and relay drivers, which were plugged to submersible pumps. The irrigation was performed according to the VWC thresholds. Throughout the experiment, we monitored VWC and the number of irrigations. Weekly, we replenished the tanks and measured the total volume of NS applied, and determined the substrate pH and electric conductivity (EC), the presence of pests and diseases and the leaf area index (LAI). At 0, 30, 60 and 90 days after the experiment starting, we sampled plants, substrates and NS for macro and micronutrients analyzes, and determined plant height, stem diameter, shoots and roots dry mass and total leaf area (LA). At the end of the experiment, we performed phytopathological analysis to detect Phytophthora spp. in the substrate and NS, diagnosed visual symptoms of nutritional deficit, assessed the production losses, counted the number of benches contaminated with algae, and determined the leaf intracellular concentration of CO2 (Ci), transpiration (E), stomatal conductance (gs), net photosynthesis (A) and water use efficiency (WUE). The results indicated that the sensors were effective to monitoring the substrate moisture and controlling subirrigation, and the treatments with highest VWC had higher moisture and number of irrigations over time (p < 0.0001). There was an increase of approximately 100% in the total volume of water applied as VWC values increased 0.12 m3 m-3 (p < 0.0001), a decrease in substrate pH and an increase in the substrate EC in treatments with higher substrate concentration of NS and higher VWC to trigger irrigation (p < 0.0001). The plants showed significant increases of LAI, height, stem diameter, shoots and roots dry mass and LA as the levels of NS and VWC increased (p < 0.0001). There were significant responses to different treatments of NS and VWC to trigger irrigation in the concentration of nutrients in the substrate and in the NS of 121 L tanks, and in the nutrient content in shoots and roots. Treatments with VWC of 0.12 m3 m-3 promoted the death of several plants by drought. The values of Ci, E, gs, A and WUE were significantly higher in plants with higher concentrations of NS and VWC thresholds (p < 0.001). Treatment with NS concentration of 50% and VWC of 0.48 m3 m-3 promoted higher plant height, stem diameter, dry mass, and total leaf area of Rangpur lime rootstocks. Subirrigation permitted the anticipation of transplant for grafting, allowing another cultivation cycle in the nursery during the year. The payback period for the replacement of the manual overhead system by subirrigation only with the savings obtained for the labor elimination to perform irrigation, the reduction in the NS concentration of 50%, and the elimination of the fertilizer disposal was 5.6 years Doutorado Água e Solo Doutor em Engenharia Agrícola

Chufa (Cyperus esculentus L. var. sativus Boeck.) is an important vegetable crop in Valencia (Spain), where its tubers are used to produce a refreshing drink called ¿horchata¿. Water is relatively inexpensive, there are no data regarding the volumes of water used to grow chufa, and the irrigation water use efficiency (IWUE) has neither been determined. The aim of this research was to compare the productive responses of the chufa crop to two irrigation strategies (IS). The volumetric soil water content (VSWC) was monitored with capacitance sensors. Trends in VSWC were used to determine the in situ field capacity (FC), beginning each irrigation event when the VSWC reached either approximately 45% (H1) or 60% (H2) of the FC at a soil depth of 0.10 m. The experiments were conducted over three consecutive seasons. An area velocity flow module measured the water flow. The yields, the water volumes used, and the IWUE were calculated. Plants were periodically sampled and the harvest index and relative growth rate were determined. The yield was affected by the year and by the IS. The greatest yields were obtained with the H2 strategy (on average 2.18 kg m¿2 for H2 vs. 1.94 kg m¿2 for H1; p ≤ 0.01), and the average tuber weight (ATW) was affected (p ≤ 0.01) by the year and IS interaction. IWUE was affected by the year, and none of the considered factors affected the harvest index (p ≤ 0.05). It can be concluded that maintaining a higher VSWC would increase both yield and ATW without affecting IWUE., This study was funded by the Regulatory Council of Denomination of Origin Chufa of Valencia of Spain.