Soil compaction due to wheeled tractors and trailed equipment has been a concern since the beginning of agricultural machanization. The interest in this subject has increased in recent years, as tractors and trailers have become heavier. Gantries pass over the field in fixed unplanted paths, between which lay the crop beds. Wheel traction increases due to soil compaction on the pathways, while the elimination of soil compaction in the growing area improves soil tilth, and provides the best soil condition for crops. To obtain optimum performance with a gantry, it must be properly designed to ensure that the structural components are strong, yet light. Since forces arising from various field operations which would act on the gantry were not directly available from the literature, they were estimated from various sources. Finite element analysis was then used to analyze the design and determine the most appropriate material sizes.

This study examines literature on subsurface irrigation of turf using published and unpublished sources to determine its relevance for the designer of irrigation systems. It looks at two installed sites to determine current industry practices and then develops a model to assist the designer of these systems. Finally areas in need of further research and technical development are suggested. Literature is not readily available to the designer and it is sometimes contradictory. Case studies show that subsurface irrigation is an effective method of irrigating turf, especially in arid parts of the world. A model to select tubing and emitter spacing is developed by summarizing existing literature and case studies. Virtually all areas of design, installation and management need further research. Two primary areas that need further investigation are specific design issues and benefits to the end user such as cost, water savings and maintenance procedures.

A ground-based remote sensing system was attached to a linear move irrigation system and successfully collected pixels at an approximate density of 1/meter 2. This low-resolution data was used to create 1-meter resolution images in near real time over a 1-hectare cotton field. A new method using GIS and spatial statistics (kriging) was successfully developed for evaluating the 1-meter images and simulate 2 through 7 meter resolution for determining the effects of scale on data collection for crop management as applied to precision agriculture. The images collected reliably predicted nitrogen and water stress in the field and demonstrated how scale from 1 to 7 meters affects reliability of measuring water and nitrogen stress. A 2X2 Latin square water and nitrogen experiment on cotton consisting of optimal and low nitrogen and water treatments was conducted within 4 replicates of the 4 treatments. The remotely sensed data were used to develop images of the plot to ascertain the ability to detecting nitrogen and water stress. Nitrogen stress was evaluated using the canopy chlorophyll content index while water stress was evaluated using the difference between canopy and air temperature. Four days of field images collected in 1999 at a 1-meter resolution were selected for evaluation. The days represent, one day prior to water and nitrogen treatments, two days of little to moderate nitrogen stress, and one day with severe nitrogen stress and moderate water stress. The image analysis incorporated standard statistics, kriging, and fractals. The 1-meter data was used to produce images with grids of 2 through 10 meters. Standard statistics were used to analyze the four days by grid size. The results indicated no difference in the mean in the data for any grid size within a treatment for either water or nitrogen; however, CV generally decreased with grid size. Kriging was used to evaluate the data for pretreatment day and stressed day for one plot representing each of the four treatments. Data for 1, 3, 5, and 7 meters resolution was kriged and compared to the 1-meter grid to determine reproducibility. It was determined that for temperature it is difficult to reproduce finer resolution data, especially in stressed plots. The nitrogen indice was reproducible to a high degree of accuracy for grids as large as 7 meters. Fractal analysis was used to evaluate the kriged data. The results were mixed in that numbers for some plots increased as grid size increased, and decreased as expected for others.

Wastewater reuse for agricultural purposes has been considered as an alternative strategy for water conservation. This study compared subsurface drip irrigation with furrow irrigation in terms of water use efficiency and crop contamination when microbial-contaminated water was used for irrigation. The effects of temperature and moisture on virus survival in soil were assessed quantitatively. Escherichia coli ATCC 25922, Clostridium perfringens, and coliphage PRD-1 served as the study microorganisms. Subsurface drip irrigation used water more efficiently than furrow irrigation due to lower water requirement for similar crop yields. Subsurface drip irrigation performed better for the deep-rooted crops, cantaloupe and bell pepper, compared to the shallow-rooted crop, lettuce. The more water was held by soil and was available for the crop uptake with the deeper root crops than shallow root crops. Overall, significantly greater microbial contamination of produce and soil surface occurred in furrow irrigated plots as compared to subsurface drip irrigated plots. Direct movement of irrigated water to the soil surface appeared to cause crop contamination in subsurface drip irrigation plots. Coliphage PRD-1 demonstrated greater crop contamination and longer survival in the environment compared to E. coli. The smaller size of PRD-1 than that of E. coli seemed to facilitate its movement through soil matrices and increased the chance to contaminate crop produce. The inactivation rate of PRD-1 increased as temperature increased. A soil moisture decrease from 20.9 to 8.9% appeared to be inversely related to the inactivation rate. Further decrease of the soil moisture content to 5.1% increased the inactivation rate. An optimum or a threshold soil moisture level for PRD-1 survival may exist. Evaporation increased the inactivation rate of PRD-1 substantially in higher temperatures but minimally in lower temperatures. A developed model predicted the inactivation rates of PRD-1 in field conditions with an average error of 11.0%. Subsurface drip irrigation with a proper management can be a sustainable strategy to conserve irrigation water as well as to reduce crop contamination when wastewater is used for crop production. PRD-1 survived better at low temperatures and dry soil moisture conditions.

Four types of cable drawn farming systems, a single engine system, a double engine system, a perimeter system, and a double implement system, were analyzed to determine which was best suited for Arizona. The systems were compared in terms of relative cost, reliability/simplicity and field capacity. Field capacity computation variables were implement width, implement speed, tower travel speed, implement carrier travel speed, and implement rotation time. The analysis showed the single engine system was the least expensive, simplest system with a field capacity identical to that of the double engine system, eight percent lower than the double implement system, and approximately thirteen percent higher than the perimeter system. Based on these results, the single implement system was judged superior to the others. The parameters affecting single implement system performance were then examined to optimize performance. The evaluation yielded a recommendation that the system be designed to have a tower speed of 48 ft/min, and a rotation time of 7.5 seconds. A positioning system for the mobile truss of a cable drawn farming system was also developed and tested. The system used a linear move irrigation system's above ground cable guidance system for steering, a wicket positioning system for stopping the machine at the indexing locations, and a wire-alignment system to control inner tower alignment. The system was tested over a length of 280 ft using a five tower, 575 ft long, linear move irrigation system. It was found that the above ground cable guidance system provided ±0.5 ft steering accuracy, the wicket positioning system controlled the power unit and end tower position within ±0.2 ft of the target destination, and that the wire alignment system controlled inner tower position within ±0.3 ft of the target destination. Statistical analysis of the test results showed the probability of position error being controlled to within ±0.4 ft and ±0.8 ft to be at the 99.7% and 99.99% confidence levels, respectively.

The soil preparation in soil bins must be capable of generating a number of soil density profiles varying from uniform to heavily compacted layers lying below more friable soil. A subsurface rotating rod firmed the soil beneath the rod and repeated passes produced desired profiles. Retrofitting the existing instrumentation with virtual instrumentation methods resulted in measurements that were more precise and improved repeatability. A Wheatstone bridge force transducer measured Cone Index pressure as a function of soil penetration depth. Soil surface elevation and implement depths were located with ratiometric linear transducers. Speed and distance were measured with an optical encoder. Prime mover hydraulic oil temperatures and pressures were gauged with current loop sensors. Three Null Hypotheses were tested: a horizontal subsurface rotating rod will not cause an increase in soil cone index; repeated operation of the horizontal rotating rod will not result in increased soil cone indexes; and soil water content is not relevant to the resultant compaction level. The first two Null Hypotheses were rejected at the 5% level in the overall case although not in each case while the third Null Hypotheses was rejected at the 5% level in all cases.

Intramuscular fat levels of pork affect the flavor of pork meat. In the pork industry, two quality attributes namely intramuscular fat (IMF) content and marbling score (MS) are used to represent intramuscular fat levels of pork meat. Conventional determination methods are not suitable for the current requirements of the pork industry as they are either destructive or subjective. This study investigated the use of hyperspectral imaging in evaluating intramuscular fat content and marbling score of pork. Intramuscular fat distribution along the longissmus muscle and the influences of freezing, thawing, and image pattern analysis on prediction capacity were also considered. Near infrared (NIR) hyperspectral imaging technique from 900 to 1700 nm was used for prediction of IMF content and MS. Fresh pork at the 3rd/4th last rib was imaged. Pattern analysis techniques of Gabor filter, wide line detector (WLD), and an improved grey-level co-occurrence matrix (GLCM) were studied and different image features, i.e. spectral, texture, and line features, were extracted. Key wavelengths were identified. Multiple linear regression (MLR) was used to develop prediction models. For determination of marbling score, the MLR model, using the first derivative of Gabor filtered mean spectra, performed best with a prediction accuracy of 0.90 at wavelengths of 961, 1186 and 1220 nm. For intramuscular fat content, prediction accuracy of 0.85 was obtained using the raw mean spectra at 1207 and 1279 nm. The distribution map of IMF content in pork was developed. The results showed the possibility of rapid and non-destructive evaluation of intramuscular fat level of pork using NIR images. Regarding marbling as a visual index, a method for objective evaluation of pork marbling score using red-green-blue (RGB) images was developed by applying WLD-based linear models. The possibility of non-destructive prediction of IMF content and MS using frozen and frozen-thawed pork was studied. Prediction accuracy of 0.90 for MS was achieved for frozen pork. Prediction accuracy of 0.82 for IMF content and accuracy of 0.91 for MS were realized by frozen-thawed pork. The potential of frozen and frozen-thawed pork for assessment of marbling score and frozen-thawed pork for the assessment of intramuscular fat content were demonstrated. Besides the effects of freezing and thawing, the variation of IMF content and MS across the last seven thoracic longissmus muscle was studied. Relationships between IMF content and MS at the last rib and the corresponding attribute at other ribs and the whole section of the loin were determined. The relationship between NIR images of rib end and the IMF level of pork at the six last thoracic ribs was investigated. Close relationships were indicated, especially between the images of rib end and IMF levels at the 2nd/3rd last ribs and the 2nd last/last ribs. / La teneur en matières grasses du porc affecte la saveur de la viande de porc. Dans l'industrie porcine, la graisse intramusculaire (GIM) et la cote de persillage (CP) sont deux propriétés qui déterminent la teneur en gras du porc. Les méthodes conventionnelles de détermination ne sont pas adaptées aux besoins actuels de l'industrie car elles sont destructrices ou subjectives. Cette étude porte sur l'utilisation de l'imagerie hyperspectrale dans l'évaluation de la teneur en graisse intramusculaire et du persillage du porc. Les effets de la répartition de la graisse intramusculaire le long du muscle Longissmus, de la congélation, du dégel et de l'analyse de la forme pour le traitement de l'image ont été pris en compte. Une technique d'imagerie hyperspectrale proche infrarouge (IR) allant de 900 à 1700 nm a été utilisée pour prédire le GIM ou la CP. La viande fraîche au niveau de la 3ème/4ème côte du porc a été utilisée pour recueillir les images hyperspectrales. Des analyses de la forme fondée sur les techniques du filtre de Gabor, du détecteur linéaire à large spectre (WLD) et de la matrice de cooccurrence de niveau gris améliorée (GLCM) ont été étudiées et les propriétés de l'image, i.e spectre, texture et propriétés des lignes, ont été extraites. La régression linéaire multiple (RLM) a été utilisée pour développer des modèles de prédiction. Pour la cote persillage, le modèle de RLM utilisant la moyenne de spectre filtrée pour la première dérivée de Gabor a le mieux performé avec une précision de calibration de 0,90 aux longueurs d'onde de 961, 1186 et 1220 nm. Pour le GIM, une précision de calibration de 0.85 a été obtenue avec un spectre moyen de base à 1207 et 1279 nm. La distribution du contenu de GIM a été illustrée. Les résultats démontrent la possibilité d'utiliser les images hyperspectralces proche IR pour évaluer rapidement et de façon non-destructive le taux de gras intramusculaire du porc. En ce qui concerne le persillage en tant qu'indice visuel, une méthode objective d'évaluation de la cote persillage utilisant des images rouge-vert-bleu (RGB) a été développée en appliquant un WLD basé sur un model linéaire au canal vert. La possibilité d'un contrôle non-destructif du GIM et de la CP utilisant du porc congelé et décongelé a été étudiée. Une précision de la prédiction de 0.90 pour la CP a été réalisée avec du porc congelé. Une précision de la prédiction de 0.82 pour le GIM découle du porc décongelé. Le potentiel du porc congelé et décongelé pour l'évaluation de la cote de persillage et du porc décongelé pour l'évaluation de la teneur en gras intramusculaire a été démontré. Outre l'effet du gel et du dégel, la variation du GIM et de la CP à travers les sept derniers muscles thoraciques Longissmus a été étudiée. Les relations entre le GIM et la CP à la dernière côte et les propriétés correspondantes aux autres côtes et au filet ont été déterminées avec précision. La relation entre les images de proche IR à l'extrémité et le niveau de GIM du porc six dernières côtes thoraciques a été étudiée. Des relations étroite ont été déterminées, en particulier entre les images de l'extrémité de la côte et les taux de GIM aux 2eme/3eme dernières côtes et la 2eme dernière côte.

Drainage and water table management are essential for crop production in humid regions. Water table management not only increases crop yield, but also reduces nitrate leaching to water bodies. This study investigated the water and nitrogen use efficiency of corn under two water management conditions and three nitrogen fertilizer levels. The sap flow heat balance method was used to measure the daily water uptake of corn, over an extended period of the growing season. The impacts of climate change on grain corn and biomass yield in eastern Canada under tile drained conditions was also evaluated over a 30 year future period (2040 to 2069). The study was conducted at a field scale in 2008 and 2009 at St. Emmanuel, Quebec. The two water management conditions were: conventional drainage (FD), and controlled drainage with subirrigation (CD-SI). The three nitrogen (N) fertilizer treatments (low, medium, and high N) were applied in a strip across three blocks. The seasonal water balance indicated that the plants in the CD-SI plots had more water than required in the wet periods, despite the system automation, while the FD plots exhibited deficit water conditions. Water could be saved in the wet periods by better regulating water supplied by subirrigation. However, in dry years, the CD-SI system increased yield. The grain corn water use efficiency (WUE) for FD plots was 2.49 and 2.46 kg m-3, in 2008 and 2009, respectively. In these years, the grain WUE for CD-SI plots was 2.43 and 2.26 kg m-3. Water management treatments demonstrated significant difference (p < 0.05) in grain yields in 2009, at low and high nitrogen levels. However, at the medium nitrogen level, water management demonstrated no significant effect (p > 0.05) on grain yields. The two water treatments had no effect on the above-ground dry biomass yields in both years. Mean nitrogen use efficiency (NUE) of grain corn and biomass varied from 27 to 99 kg kg-1. Highest NUE (99 kg kg-1) was observed under low N (~120 kg N ha-1) and lowest NUE (41 kg kg-1) occurred in the high N (~260 kg N ha-1). This might be due to higher nitrogen losses due to leaching, residual nitrogen in the soil, and more denitrification in high N plots. The rate of plant water uptake measured by the sap flow method, varied from 3.55 to 5.11 mm d-1 from silking to full dent stage of corn growth. These rates were consistent with ETc calculated by the FAO-56 Penman-Monteith method (3.70 to 5.93 mm d-1) for both years. Although, silking is considered as a critical stage for corn growth, water demand was highest at the milk stage (45.63 to 59.80 mm). Transpiration during this stage constituted 10 to12% of the total water requirement of the corn for the season. The silking to full dent stage accounted for approximately 40% of the total water requirement of the crop. The STICS (JavaStics v1.0) crop model was used to examine the impacts of climate change, under the B1 emissions scenario, on corn yield from 2040-2069. The model was calibrated using 2008 field measured data, and then validated using the 2009 data set. Corn grain yield was underestimated by 1.5 to 2.6 Mg ha-1 for the two years of measurement. Total dry biomass was also underestimated by 0.9 to 2.6 Mg ha-1. Simulations for the B1 emissions scenario using synthetic weather data was run under the same crop conditions as in 2008. Tukey's studentized range (HSD) test of corn grain yield indicated that yields at high and low N, and high and medium N were different at the 95% confidence level. Grain and biomass production from 2040-2069 under B1 emissions scenario responded differently (p < 0.05) for the three N treatments. However, the Mann–Kendall test showed neither increasing nor decreasing trend (MK-stat > - 1.96) at a 95% confidence level. / Le drainage et la gestion de la nappe phréatique des parcelles agricoles permet non seulement d'augmenter la production des récoltes, mais aussi de réduire les pertes de nitrates par lessivage, qui contribue à leurs transferts vers les étendues d'eau. Cette étude a examiné l'efficacité d'utilisation de l'eau et de l'azote du maïs grain sous deux conditions de gestion de l'eau et trois niveaux d'application d'azote. Les facteurs climatiques jouent un rôle important dans la production du maïs-grain. Les impacts des changements climatiques sur les projections de maïs-grain et de la production de biomasse en sol drainé ont aussi été évalués pour l'est du Canada pour une période futur de 30 ans (2040 à 2069). L'étude a été accomplie à l'échelle du champ en 2008 et en 2009 à Saint Emmanuel au Québec. Les deux scénarios de gestion de l'eau étaient (a) le drainage conventionnel (FD) et (b) le drainage contrôlé combiné à l'irrigation souterraine (CD-SI). Les trois traitements d'azote (N) (dose faible, moyenne et élevée) ont été appliqués en bande sur trois blocs. L'efficacité d'utilisation de l'eau du maïs (WUE) pour les blocs en FD était de 2.49 kg m-3 et 2.46 kg m-3 en 2008 et 2009 respectivement. Pour ces années, L'WUE du maïs-grain pour les blocs en CD-SI était de 2.43 kg m-3 et de 2.26 kg m-3. Les traitements relatifs à la gestion de l'eau ont permis d'améliorer la production de rendement du maïs-grain significativement (p <0.05) en 2009, que cela soit avec des doses d'azotes basses ou élevées. Cependant, pour des doses intermédiaires, la gestion de l'eau n'a démontré aucun effet significatif (p> 0.05) sur les productions de maïs-grain. Les deux traitements relatifs à la gestion de l'eau n'ont eu aucun effet sur la production de biomasse sèche au-dessus du sol pour les deux années. L'efficacité moyenne de l'utilisation de l'azote (NUE) du maïs grain et de sa biomasse variait de 27 kg kg-1 à 99 kg kg-1. La plus haute NUE (99 kg kg-1) a été observée pour une dose de N faible (~120 kg N ha-1). La plus basse NUE (41 kg kg-1) s'est produite pour une dose de N élevée (~260 kg N ha-1). La consommation des plantes en eau mesurée par la méthode d'écoulement de la sève, vari de 3.55 mm d-1 à 5.11 mm d-1 pour la période de l'apparition des soies jusqu'à la croissance complète du maïs-grain. Ces taux sont en accord avec l'ETc calculée (3.70 mm d-1 à 5.93 mm d-1) pour les deux ans. Bien que, le développement de la soie soit considéré comme le stade critique pour le maïs-grain, la demande en eau fut la plus élevée lors du stade laiteux du développement du maïs (45.63 mm à 59.80 mm). À ce stade, 10 à 12% des besoins totaux de la plante en eau pour la saison furent transpirés. Du stade de la soie jusqu'au développement complet de l'épi de maïs les besoins en eau de la plante ont représenté environ 40 % de son besoin total. Le modèle de récolte STICS (JavaStics v1.0) a été utilisé pour examiner les effets du changement climatique sur la production de maïs- grain, de 2040 à 2069 et sous le scénario d'émissions de gaz à effet de serre B1. Le modèle a d'abord été calibré en utilisant les données mesurées au champ en 2008 et, a ensuite été validé avec l'ensemble des données de 2009. La production de maïs-grain est sous-estimée de 1.5 Mg ha-1 à 2.6 Mg ha-1 pour les deux ans de mesure. La biomasse sèche totale est aussi sous-estimée de 0.9 Mg ha-1 à 2.6 Mg ha-1. Les simulations pour le scénario d'émissions B1 en utilisant des données météorologiques synthétiques font été utilisées dans les mêmes conditions de récolte que 2008. Les prédictions de la production de maïs-grain et de sa biomasse pour la période 2040-2069 sous le scénario d'émissions B1 sont différentes (p <0.05) selon les trois traitements de N. Cependant, l'épreuve de Mann-Kendall n'a montré aucune tendance à la hausse ou à la baisse (MK-stat> - 1.96) pour un niveau de confiance de 95%.

To optimize irrigation water use, temporal and spatial sensor-based data related to soil water content were integrated. Nine locations in a 37-ha agricultural field were selected using field elevation and soil ECa maps for monitoring the soil matric potential and temperature at four depths (18, 48, 79 and 109 cm) with a wireless sensor network. Using a linear regression approach, a series of time-specific equations were developed to quantify both the temporal and spatial soil water stress status through a Water Stress Index (WSI). The WSI was estimated using soil matric potential measurements along with supplemental soil characteristics, such as site-specific soil matric potential corresponding to 25% soil water depletion that was derived based on soil physical properties. Further analysis was performed to quantify the percentage of the field that undergoes a potential shortage in water supply. These results could be used to optimize irrigation scheduling and to assess the potential for variable-rate irrigation. The second study investigated the way in which the WSI prediction quality is affected by the number and placement of temporal soil water content monitoring sites. The concept, potentially, could be used to investigate a variety of site-specific crop management strategies. It was developed to assess WSI predictability in context that the modeled relationship between WSI and spatial field data (ECa and elevation) is not perfect at any given point of time. The established regression model between ECa, field topography maps and WSI from the first study was applied to construct WSI maps representing a specific point in time in six experimental fields with different crop growing conditions located in Nebraska, USA. Artificial regression error models with different degrees of spatial structure were superimposed onto these maps to simulate actual WSI distribution across the fields. Both random and optimized monitoring site placement strategies were evaluated in terms of the ability to predict the simulated WSI maps. The results showed that it was necessary to optimize the selection when the number of monitoring sites was low. However, a random placement method was equally efficient when the number of monitoring sites was high. Careful selection of representative field areas representing significant field areas with extreme conditions should allow only 2 or 3 monitoring sites to produce results with relatively low WSI prediction error.Through the process of water management optimization, it was noted that the ability to detect site-specific water storage capacity is an important task. Since it is related to the change of soil physical properties with depth, a third study was conducted to develop a dynamic scanning of soil profile tools using a galvanic contact resistivity approach. Transmitting and receiving electrodes were configured in an equatorial dipole array. An automated scanner system has been developed and tested in the agricultural field environment with different soil profiles. While operating in the field, the distance between the current injecting and measuring pairs of rolling electrodes was varied continuously from 40 to 190 cm. The resulting scans were evaluated against 1-m deep soil profiles and that of an electromagnetic induction instrument at various depths, up to 3 m. / Pour atteindre l'utilisation optimale de l'eau d'irrigation, des données spatio-temporelles provenant de sondes et reliées au contenu en eau du sol ont été intégrées. Ainsi, dans un champ agricole de 37 hectares, neuf sites ont été sélectionnés en utilisant les cartes d'élévation et de CEa du sol afin d'assurer le suivi du potentiel matriciel et de la température du sol à quatre profondeurs (18, 48, 79 et 109 cm) avec un réseau de capteurs sans fil. Utilisant une approche de régression linéaire, une série d'équations spécifiques au temps a été développée pour quantifier l'état de stress hydrique du sol dans le temps et l'espace à l'aide d'un Indice de Stress Hydrique (ISH). L'ISH a été estimé en utilisant des mesures de potentiel matriciel du sol combiné à ses caractéristiques supplémentaires, telles que celles calculées à partir de ses propriétés physiques et du potentiel matriciel spécifique au site correspondant à un appauvrissement de 25% des eaux du sol. Une analyse additionnelle a permis de quantifier la fraction du site ayant un potentiel d'approvisionnement en eau déficitaire. Ces résultats pourraient être utilisés afin d'optimiser la planification de l'irrigation et d'évaluer le potentiel d'irrigation à débits variables.La seconde étude a permis un examen plus approfondi de la qualité de prédiction de l'ISH influencé par le nombre et l'emplacement de sites chronologiques de surveillance du contenu hydrique du sol. Le concept pouvant potentiellement être utilisé pour étudier une diversité de stratégies de gestion de cultures a été développé afin d'évaluer la prévisibilité de l'ISH en tenant compte de la relation imparfaite entre cet indice et les données spatiales à tout temps donné. Le modèle de régression établi entre la CEa, les cartes topographiques du champ et l'ISH de la première étude a été appliqué afin de construire des cartes d'ISH représentant un moment spécifique pour six champs expérimentaux sous différentes conditions de croissance au Nebraska, USA. Des modèles artificiels d'erreur de régression avec différents degrés de structure spatiale ont été superposés sur ces cartes pour simuler la distribution réelle de l'ISH à travers ces champs. Autant de stratégies aléatoires et optimisées de placement de sites de surveillance ont été évaluées en termes de leur habilité à prédire les cartes d'ISH simulées. Les résultats démontrent qu'il était nécessaire d'optimiser la sélection de sites de surveillance lorsque leur nombre était bas. Cependant, la méthode de placement aléatoire était tout aussi efficace lorsque le nombre de sites était élevé. Une sélection rigoureuse des régions du champ permettant de représenter ses aires significatives avec des conditions extrêmes devrait permettre la production de résultats ayant une erreur de prédiction de l'ISH très basse à partir de seulement deux ou trois sites de surveillance.À travers le processus d'optimisation de la gestion de l'eau, il a été noté que l'aptitude à détecter la capacité d'emmagasinement d'eau spécifique au site est une tâche importante. Puisqu'elle est liée au changement de propriétés physiques du sol avec la profondeur, la troisième étude a été menée afin de développer un outil de balayage (scan) dynamique des profils du sol en utilisant une approche de résistance du contact galvanique. Les électrodes émettrices et réceptrices ont été configurées suivant un dispositif dipôle équatorial. Un système de scanner automatisé a été développé et testé dans un environnement de terre agricole avec différents profils de sol. Lors de l'utilisation sur le terrain, la distance entre les pairs d'électrodes roulantes d'injection et de mesure variait continuellement de 40 à 190 cm. Les balayages résultants ont été évalués avec des profils de sols de 1m de profondeur, alors que ceux fait à partir d'un appareil d'induction électromagnétique ont été évalués à des profondeurs variées allant jusqu'à 3m.

Horticultural producers are in need of efficient and timely techniques for determining crop water requirements. The question of when and how much to irrigate, termed irrigation scheduling, is particularly important for high-value crops such as strawberries (Fragaria ananassa). During the growing season, irrigation scheduling decisions are influenced by climatic variables such as rainfall, temperature and humidity, which directly impact soil moisture levels. A field study was therefore conducted to evaluate two soil moisture sensors for irrigation scheduling of commercial strawberries on a farm in Simcoe, Southern Ontario. Strawberries were grown on raised beds with plastic mulch under two management practices – open field and plastic high tunnels. For each practice, two soil moisture sensors based on time domain reflectometry (TDR) were evaluated. The sensors, Campbell Scientific's water content reflectometer (WCR) and ESI's Gro-point (GP) monitored soil moisture continuously over the growing season (May to October 2007). Soil samples were collected to obtain volumetric water content as a unit of reference for the purpose of comparison and evaluation of the two sensors. Equivalent water depths (EWD) were calculated for an effective strawberry rooting depth of 0.3 m. The calculated EWDs were compared with the grower's irrigation scheduling practices. The study found that the WCR and GP reliably recorded continuous trends in soil moisture throughout the growing season. For the WCR sensor, gravimetric analyses of soil samples showed excellent correlation, resulting in R2 of 0.94 and 0.97 for the open field and plastic high tunnel, respectively. The R2 for the GP sensor was good at 0.88 for the open field but poor for the plastic high tunnels, due to a malfunctioning sensor. The EWDs for the two plots were calculated to be 699 mm for the open field and 711 mm for the plastic high tunnels. A significant fin / Les horticulteurs ont besoin de déterminer avec précision les besoins en eau d'irrigation des cultures. En effet, la bonne gestion de la production et l'obtention d'un meilleur rendement des fraises (Fragaria ananassa) nécessitent la planification de la quantité d'eau à apporter et le jour de l'irrigation. Le climat, la pluviométrie et la variation de la température durant le stade de croissance des plantes sont des variables importantes qui compliquent la tâche de la planification de l'irrigation. La problématique de cette étude s'inscrit dans l'optique d'évaluer l'apport de deux capteurs d'humidité du sol de type TDR (Time Domain Reflectometry) à la planification de l'irrigation des fraises à Simcoe, au sud d'Ontario. Il convient de noter que les fraises ont été cultivées avec la technique du paillis de plastique, en plein champ, ainsi qu'avec la technique du tunnel en plastique. Pour atteindre les objectifs assignés à cette étude, l'utilisation de deux capteurs de type WRC (Campbell Scientific water content reflectometer) et GP (ESI's Gro-point) a permis de suivre d'une manière continue l'humidité du sol pendant le stade de croissance (mai à octobre 2007). Aussi, des échantillons du sol ont été collectés afin d'obtenir la teneur volumique en eau. Cette dernière a été utilisée comme référence et a permis ainsi de comparer et d'évaluer les résultats obtenus à l'aide des différents capteurs. Également, nous avons calculé l'équivalent d'eau en profondeur (EEP) pour une zone racinaire des fraises de 30 cm. Ce procédé nous a permis de comparer l'EEP calculé pour les différentes pratiques d'irrigation adoptées par les producteurs. Les résultats obtenus ont démontré que le WCR et GP représentent la variabilité de l'humidité du sol pendant le stade de la croissance. Pour le capteur WCR, nous avons pu établir une corrélation très intéressante avec l'analyse