Abstract For high-value horticultural crop production in southern Ontario, irrigation is an essential ingredient in overcoming insufficient rainfall and achieving stabilized crop production. In a context where competition for limited water resources intensifies due to the expansion of the agricultural sector, increasing urban development and tourism, and potential climate change impacts, conserving water through efficient irrigation has become a key solution in addressing this growing challenge. The implementation of advanced soil water monitoring technologies and water budgeting methods for improved irrigation scheduling is examined with regard to water conservation and thus as a means to cope with competing demands for limited water supplies. During the 2007 growing season, soil moisture was measured using two sensors at four field sites (comprising a total of six irrigated zones as two sites include two different irrigation/production systems) in southern Ontario. Irrigation water consumption was measured by flow meters at three sites. In addition, a survey was administered to collect information on growers' current irrigation scheduling practices. On-farm irrigation performance was assessed by comparing calculated tomato, green bell pepper, strawberry and peach water requirements (using the water budget method) with growers' estimates of irrigation water use and with soil moisture measurements taken during the growing season. Four out of the six irrigated zones were excessively irrigated, while in one zone, water was insufficiently applied. The crop water requirements were met efficiently exclusively in one zone where tomatoes were grown. Overall, the results of this research show that by implementing advanced soil moisture monitoring technologies, growers can increase precision in water application and reduce the uncertainty in their current irrigation scheduling practices. Dans le sud de l'Ontario, l'irrigation est essentielle à la production de cultures horticoles à haute valeur ajoutée afin de compenser l'insuffisance de précipitations et stabiliser la production des cultures. Dans un contexte où la compétition pour les ressources limitées en eau s'intensifie en réponse à l'expansion du secteur agricole, à la croissance du développement urbain et du tourisme, ainsi qu'aux impacts potentiels des changements climatiques, conserver l'eau grâce à des techniques d'irrigation économes est devenue une solution incontournable pour affronter ce défi grandissant. L'implémentation de technologies avancées de surveillance de la teneur en eau dans le sol et d'un bilan hydrique, pour améliorer les pratiques d'irrigation programmée, est examinée afin de conserver l'eau et ainsi mieux faire face aux demandes concurrentielles pour les ressources limitées en eau. Au cours de la saison de croissance de 2007, l'humidité du sol a été mesurée avec deux sondes pour quatre sites (comprenant un total de 6 zones irriguées) situés dans le sud de l'Ontario. Les quantités d'eau utilisées pour irriguer étaient mesurées par des compteurs de débit installés sur trois sites. De plus, les producteurs ont répondus à un questionnaire ayant pour mandat de recueillir de l'information concernant leurs pratiques actuelles d'irrigation programmée. La performance d'irrigation à l'échelle de la ferme a ensuite été évaluée en comparant les besoins en eau de tomates, poivrons verts, fraises et pêches (calculés à l'aide d'un bilan hydrique) avec la quantité d'eau d'irrigation utilisée telle qu'estimée par les producteurs, ainsi qu'avec les mesures d'humidité du sol prises au cours de la saison de croissance. Dans cinq des six zones irriguées, la quantité d'eau appliquée était soit excessive, soit insuffisante. Une application d'eau d'irrigation excessive a été détectée dans quatre des zones alors qu'une application insuffisante a été observée dans une des zones. Les besoins en eau des cultures ont été comblés efficacement dans une seule zone. Somme toute, les résultats de cette étude montrent qu'en implémentant les technologies avancées de surveillance d'humidité dans le sol, les producteurs pourraient généralement économiser de l'eau en réduisant l'incertitude actuellement imbriquée dans leurs pratiques d'irrigation programmée.
Remote sensing images provide a reliable approach to monitor crop physiological development and can be used to assess crop evapotranspiration (ETc) and irrigation water requirements (IWR). This study compared the suitability of multispectral images acquired from Unmanned Aerial Vehicles (UAV-MSI), PlanetScope, and Sentinel-2A & 2B satellite platforms for estimating ETc. It integrated this ETc data with in situ soil moisture data to estimate IWR of field gown tomato crops (Lycopersicum esculentum) in southeastern Canada. The experimental field was divided into three (3) blocks, and irrigation scheduling consisted of 100, 80, and 60% of soil's field capacity, corresponding to three irrigation regimes. Plants were selected from each of the three blocks, through a systematic grid sampling approach. The sampled plants were georeferenced and identified in the images. Normalized difference vegetation indices (NDVI) obtained from the remote sensing platforms were evaluated for estimating the crop consumptive coefficient and ETc. The ETc predicted from satellite images were compared with estimates of ETc obtained from the FAO 56 Penman-Monteith module of the AquaCrop model. ETc maps from Sentinel-2 were combined with soil moisture data to predict IWR. The results indicate a significant difference in average NDVI values obtained from the UAV-MSI (0.87 ± 0.03) and satellite platforms (0.71 ± 0.03 and 0.82 ± 0.05, for PlanetScope and Sentinel-2, respectively), which suggests that the UAV-MSI overestimated the field NDVI values. There was a good agreement between Kc and NDVI values extracted from satellite images, with R2 = 0.98, p < 0.001, for Sentinel-2 and R2 = 0.78, p < 0.001, for PlanetScope. ETc values estimated from Sentinel-2 satellite platform were closely corroborated with AquaCrop model (with R2 = 0.94; p < 0.01), which shows the suitability of Sentinel-2 imagery for assessing crop canopy cover and IWR at the field scale. The amount of irrigation water that the grower applied using micro-drip irrigation system (342 and 416 mm in 2017 and 2018 growing seasons, respectively) exceeded the estimated IWR (165 and 199 mm in 2017 and 2018 growing seasons, respectively), which suggests that the field was over-irrigated. This study has shown the practicality of integrating soil moisture measurements and remotely sensed crop parameters for mapping actual irrigation requirements. It indicates a significant progress towards the development of a near real-time approach for supporting precision irrigation.
Nonequilibrium and nonlinear sorption of the contaminants in the fractured porous media could significantly influence the shape of the breakthrough curve (BTC). For the fracture-matrix system, there are very few studies which consider these processes. In this study, the nonequilibrium fracture-matrix model with two different nonlinear sorption isotherms, namely nonlinear Freundlich and Langmuir sorption isotherms were developed. The effect of sorption nonlinearity and nonequilibrium conditions on the shape of the BTC was studied using the temporal moments. The developed models along with the linear equilibrium, linear nonequilibrium fracture matrix models, and the multirate mass transfer model were used to simulate the BTC, which were compared with the experimental data available in the literature. Both sorption nonequilibrium and nonlinearity were found to significantly influence the shape of the BTC. Presence of sorption nonlinearity reduces the solute spreading, whereas presence of nonequilibrium conditions increases the solute spreading. Considering the sorption nonequilibrium along with the sorption nonlinearity leads to an improved simulation of the BTC. The nonequilibrium nonlinear sorption models could simulate the extended BTC tailing resulting from sorption nonlinearity and rate-limited interaction in the fracture-matrix system.
Intercropping and water table management have become important tools in reducing nitrate leaching from fields under maize production in Quebec. However, the effects and interactions between these two management practices and soil moisture and water table fluctuations in the region have not been investigated. A water table management study was conducted in Soulanges County, Quebec during the summer of 1994. Three water table levels freely drained (1.0 m) and subirrigated to 0.5 m and 0.75 m from the ground surface; and two cropping systems; monocropped maize (Zea mays L.) and maize with ryegrass (Lolium multiflorum Lam.), were factorially combined. Soil moisture content (SMC) at three depths (0–0.15, 0.15–0.30, and 0.3–0.5 m), and water table depths (WTD) were monitored twice a week, and meteorological data were collected at the site. The 0.5 m and 0.75 m subirrigated plots provided the same SMC trends in both cropping systems, but the SMC in freely drained plots was always lower than in the subirrigated plots. The cropping system did not affect SMC in either water table management system. WTDs were greater in the freely drained plots than in the subirrigated plots. These results are discussed in the context of best management practices for corn production in Quebec.
Jamaica's water resources are under increasing risk of degradation and depletion, especially in light of increasing population growth, urbanization, and climate change. In this study, the soil and water assessment tool (SWAT) was used to simulate the hydrologic characteristics of the Rio Nuevo watershed in Jamaica to assess streamflow availability for irrigation supply during dry periods. Approximately 85% of the watershed consists of aquiclude rock material, thus resulting in low potential for interaction between surface and groundwater. Historical climatic data (precipitation and temperature) were obtained for the watershed, and streamflow data were obtained for the Rio Nuevo, which drains the watershed. The model was calibrated over the period 2002–2004, and validated using the period 2005–2007. This paper outlines the parameterization of SWAT for the Rio Nuevo watershed and describes the potential for its use in agricultural water scarcity management in Jamaica. A Nash-Sutcliffe efficiency (NSE) coefficient of 0.76 was obtained for calibration, whereas a coefficient of 0.50 was obtained for validation. Results indicate that in drought periods, the stream cannot supply the necessary water needed for the agricultural areas.
Abstract Water table management with controlled drainage and subsurface-irrigation (SI) has been identified as a Beneficial Management Practice (BMP) to reduce nitrate leaching in drainage water. It has also been shown to increase crop yields during dry periods of the growing season, by providing water to the crop root zone, via upward flux or capillary rise. However, by retaining nitrates in anoxic conditions within the soil profile, SI could potentially increase greenhouse gas (GHG) fluxes, particularly N 2 O through denitrification. This process may be further exacerbated by high precipitation and mineral N-fertilizer applications very early in the growing season. In order to investigate the effects of water table management (WTM) with nitrogen fertilization on GHG fluxes from corn ( Zea mays ) agro-ecosystems, we conducted a research study on a commercial farm in south-western Quebec, Canada. Water table management treatments were: free drainage (FD) and controlled drainage with subsurface-irrigation. GHG samples were taken using field-deployed, vented non-steady state gas chambers to quantify soil CO 2 , N 2 O and CH 4 fluxes weekly. Our results indicate that fertilizer application timing coinciding with intense (≥24 mm) precipitation events and high temperatures (>25 °C) triggered pulses of N 2 O fluxes, accounting for up to 60% of cumulative N 2 O fluxes. Our results also suggest that splitting bulk fertilizer applications may be an effective mitigation strategy, reducing N 2 O fluxes by 50% in our study. In both seasons, pulse GHG fluxes mostly occurred in the early vegetative stages of the corn, prior to activation of the subsurface-irrigation. Our results suggest that proper timing of WTM mindful of seasonal climatic conditions has the potential to reduce GHG emissions.
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