No description available.

The North American cranberry plant (Vaccinium macrocarpon Aiton) is a wetland crop species grown commercially in natural or constructed peat or sandy soil basins. Since production is highly water dependent, water requirements are very significant and have prompted growers to explore new water management practices to improve irrigation efficiency and protect water resources. One way of conserving and better managing water, given the infrastructure in place, would be to develop sub-irrigation. / The design of a subsurface irrigation system requires the evaluation of various soil properties. This was undertaken at four established cranberry production sites, situated near Saint-Louis-de-Blanford, Quebec. Two of the fields contained a sandy soil, and the other two were peat soils. Soil physical properties measured included: saturated hydraulic conductivity, bulk density, porosity, soil moisture characteristic curves and particle size distribution.

The overall goal of this study was to investigate the possibility of reducing NO3-- concentration in the lower soil horizon by promoting denitrification. The study looked at an inexpensive remediation practice for subsurface-drained fields in order to degrade N0j' and consequently diminish NO3-- pollution. The experiments were conducted on a corn field at the Macdonald Campus Farm. The field was composed of sandy loam soil underlined by a clay layer. / In this study, sucrose was injected at a concentration of 20 mg L --1 within the subirrigation water. Furthermore, the water table was maintained at approximately 70 cm from the soil surface in order to create an anaerobic environment that allows for denitrification. The purpose was to furnish dissolved organic carbon (DOC) to the resident microorganisms in order to carryout a higher amount of denitrification. / The NO3-- levels in ground water were monitored weekly. Gas samples were taken from the field to observe whether N2O emissions increased as a result of the treatment This was considered to be important since N2O is a greenhouse gas. / It was found that the addition of sucrose significantly resulted in a faster rate of denitrification. The higher biological activity severely damped the NO3-- peaks in the subsoil, which arose following major rainfall events. / The addition of sucrose at 20 mg L--1 was found to be significant in lowering the amounts of released N2O. Therefore, adding DOC in the subirrigation water not only helped remediate water contamination but also served as a remedy to atmospheric pollution. / In addition, the hydraulic conductivity of the soil was monitored to ensure that no bioclogging arose from an anticipated rise in the bacterial population due to the addition of sucrose. It was found that the addition of sucrose at 20 mg L--1 did not contribute in anyway to reduce the soil's hydraulic conductivity.

Field experiments were conducted on St-Samuel sandy loam soil in 1982 and 1983, with eight replicates of irrigated and non-irrigated maize plots. Soil moisture regime, root density and maize yields were determined to demonstrate the effect of subsurface irrigation and drainage systems. / Laboratory experiments were conducted on large and small undisturbed soil cores to determine pertinent soil properties, relating drainable volume and steady upward flux to water table depth. / A water balance model was developed and used with a stress-day-index to predict water table depth, excessive and deficit soil moisture conditions and effects on corn yield. Economic analyses were made to identify subsurface irrigation/drainage designs which optimize the profit for a corn crop. / A simple method based on first and second order moments was proposed to determine the effects of parameter uncertainty in the relationship of steady upward flux vs water table depth on subsurface irrigation/drainage design parameters. / Based on the above information, a realistic subsurface irrigation/drainage design was proposed and operational recommendations were made for an example field.

This study describes a laboratory scale development of an in-situ bioremediation method, which uses a water table management system to supply nutrients to subsoil microorganisms, for biostimulation and subsequent biodegradation of pollutants such as fertilizer-nitrate and hydrocarbons (e.g., diesel oils), in the unsaturated zone of the soil. The study, which was divided into two parts: first nitrate bioremediation and secondly diesel biodegradation, was carried out on packed soil columns. / For the nitrate study, different levels of glucose were introduced into packed soil columns, 1,000 mm long x 200 mm, diameter, via subirrigation in order to supplement the organic carbon levels in the soil. Two sandy soils were used, with 1.6% and 3.4% organic matter content, respectively; and the water table in the soil columns was maintained at a depth of 350 mm below the surface. Fertilizer-nitrate was applied to the soil surface at a rate of 180 kg/ha nitrate-N. Simulated rainfall was used to leach nitrates to lower depths. The efficacy of using the subirrigation system, as a method for nutrient delivery in the bioremediation of leached nitrate, was monitored with time and with reference to the nitrate residue, redox potential of the soil solution, and solubilized Fe and Mn. / Leached nitrate was denitrified to less than 10 mg/L nitrate-N, which is the limit permitted in drinking water. The ideal organic carbon range was considered to be the glucose level (20 mg/L glucose-C) that reduced mom nitrate and gave redox potential and soluble Fe and Mn levels, similar to the control soil solution, when subjected to 96 days of subirrigation. Successful delivery of nutrient for the bioremediation of nitrate, within the farm boundaries, will be considered a "break through" toward nitrate residue control if this novel approach to nitrate control is demonstrated in the field. The delivery method will offer a technical solution to on-farm nitrate pollution. It is inexpensive, easy to adopt, and does not require major changes in the current farm practices. / In the second part of the study, a diesel contaminated sandy soil was packed in columns, 2,000 nun long x 200 nun diameter. The subirrigation method was used to supply two different combinations of treatments to the microorganisms in the soil for the biodegradation of the diesel namely: air, water and nutrients (N, P etc.), and air and water. The success of using subirrigation, to deliver nutrients to the soil in the columns, was monitored by measuring the trend in the reduction of soil diesel-TPH (diesel-total petroleum hydrocarbon) residue with time. Results obtained from the treated columns were compared with each other, and with the control columns undergoing passive biodegradation. / The study showed that subirrigation can be used as a method of nutrient delivery in the -bioremediaton of diesel contaminated soil. The TPH in the contaminated soil decreased, from an initial 670 mg diesel TPH/kg soil to an acceptable level of 40 mg diesel TPH/kg soil, in 82 days in the columns subjected to a combination of nutrient, air and water treatments. If this method of delivering biostimulants to the subsoil microbial population is demonstrated in the field, it will be invaluable to in-situ bioremediation of contaminated soils.

No description available.

Subirrigation systems are generally used in humid areas to provide suitable moisture conditions for plant growth. These systems can also be used to reduce pesticide loadings from agricultural lands, since they tend to keep the discharging waters within farm boundaries for extended periods of time. This allows for greater pesticide microbial and chemical degradation. / A three-year field lysimeter study was initiated to investigate the role of subirrigation systems in reducing the risk of water pollution from the three most commonly used herbicides in Quebec, namely atrazine (2-chloro-4[ethylamino]-6[isopropylamino]-1,3,5-triazine), metribuzin (4-am ino-6(1,1-di meth yl eth yl)-3-(meth yl thio)-1,2,4-tria zin-5(4H)-one), and meto lach lor (2-chlo ro-N-(2-eth yl-6-methyl phen yl)-N-(2-meth oxy-1-meth yl eth yl)acet amide). Eighteen PVC lysimeters, 1 m tall x 0.45 m diameter, were packed with a sandy soil. Three water table management treatments, i.e. two subirrigation treatments with constant water table depths of 0.4 and 0.8 m, respectively, and a free drainage treatment in a completely randomized design with three replicates were used. Grain corn (Zea mays L.) and potatoes (Solanum tuberosum L.) were grown on lysimeters, and herbicides were applied each year at the locally recommended rates at the beginning of each summer. Soil and water samples were collected at different time intervals after each natural or simulated rainfall event. Herbicides were extracted from soil and water samples and were analyzed using Gas Chromatography. / From the three years results (1993--1995), it has been concluded that all three herbicides were quite mobile in this sandy soil, as they leached to the 0.85 m depth below the soil surface quite early in the growing season. This suggests that if the drainage effluent or seeping waters from sandy soils of agricultural lands in southern Quebec drain freely, they may be considered to be a serious non-point source of pollution to the water bodies. The results have also shown that herbicide concentration decreased with soil depth as well as with time, meaning that the higher herbicide residues were found at top layers, and soon after the herbicide application. The herbicide mass balance study revealed that when the drainage effluent was kept within the lysimeters under the subirrigation setup, there was a statistically significant reduction of atrazine and metribuzin residues (shorter half lives) in the adsorbed and liquid phases. However, the reduction in metolachlor concentration under the subirrigation system was not statistically significant. These findings suggest that subirrigation, combined with certain herbicides can significantly reduce the herbicide loadings from corn and potato farms in southwestern Quebec, and become environmentally beneficial. / A computer simulation model (PRZM2), was used to simulate atrazine, metribuzin, and metolachlor leaching in the lysimeters, under subsurface drainage conditions. The simulated values for all three chemicals in most of the cases followed the leaching pattern of observed data. But the model either under- or over-estimated the herbicide concentrations in the soil. This could have been caused by simplistic instantaneous linear adsorption/desorption of herbicides, and inadequacy of conventional Darcian approach for the treatment of matrix flow.

Field water table measurements were taken at two sites in Southern Quebec in order to validate DRAINMOD, a field scale water table management model. Two growing seasons of data were collected on a loamy sand soil near Sorel, Quebec and one year of data on a clay soil to the south-west of Montreal. Several water table management schemes were investigated, ranging from conventional subsurface drainage to automated subsurface irrigation. / DRAINMOD was used to simulate the measured water table fluctuations and relative corn crop yields over the growing season. Verification of the model was needed to determine if it could be a useful tool in the design and operation of water table management systems for the Quebec region. / It was found that DRAINMOD output closely simulated the water table fluctuations for conventional drainage and subsurface irrigation plots provided no exceptional circumstances existed. More study is needed in some areas such as bedded fields and in the use of fluctuating water level control structures.

As Várzeas Tropicais no estado do Tocantins são exploradas intensivamente com duas safras anuais irrigadas: arroz irrigado pelo método de inundação na safra do período chuvoso e diversas culturas de maior valor agregado pelo método da subirrigação na entressafra durante o período de estiagem. Existe uma carência de informações técnicas sobre este bioma e sobre a prática da subirrigação. O trabalho Análise da Subirrigação em Várzeas Tropicais foi realizado com o objetivo de analisar o comportamento deste método de irrigação, através do monitoramento dos níveis de água nos canais e no lençol freático, da produtividade e outros parâmetros complementares. A pesquisa foi realizada na àrea do Projeto Rio Formoso em Formoso do Araguaia – TO durante a entressafra 2009, explorada com a cultura da soja destinada à produção de sementes, local onde esta prática é utilizada constantemente desde o ano de 1981. O acompanhamento da cultura e os resultados obtidos demonstraram que este método de irrigação atendeu parcialmente a demanda hídrica básica da cultura instalada. Nos trinta pontos monitorados, tanto a produtividade como o nível médio do lençol freático apresentaram individualmente grandes variações entre si. Não houve correlação significativa entre a variação do nível do lençol freático com a produtividade, com a distância dos canais terciários de irrigação e drenagem e com a evapotranspiração máxima. Também não houve correlação da produtividade com a distância dos canais terciários de irrigação e drenagem e nem com a granulometria do solo. / The Tropical Floodplains in the state of Tocantins are intensively farmed with two annual irrigated crops: flood irrigated rice in the rainy season and various higher added value crops using the subirrigation method between harvests during the dry period. There is lack of technical information about this biome and about the practice of subirrigation. The study “Analysis of Subirrigation in Tropical Floodplains” was done to analyze the behavior of this irrigation method by monitoring the water levels in the canals and water table, yield and other complementary parameters. The study was performed in the Rio Formoso Project area, in Formoso do Araguaia, state of Tocantins (TO), during the period between harvests in 2009, with a soybean crop for seeds. This has been a continuous local practice since 1981. The follow up of the crop and the results obtained showed that this irrigation method partially covered the basic water demand of the installed crop. At the thirty points monitored, both yield and mean level of the water table individually presented great variations in relation to each other. There was no significant correlation between the water table variation and yield, distance from the tertiary irrigation and drainage canals and maximum evapotranspiration. There was also no correlation between yield and distance from the tertiary irrigation and drainage canals or soil grain size.

As Várzeas Tropicais no estado do Tocantins são exploradas intensivamente com duas safras anuais irrigadas: arroz irrigado pelo método de inundação na safra do período chuvoso e diversas culturas de maior valor agregado pelo método da subirrigação na entressafra durante o período de estiagem. Existe uma carência de informações técnicas sobre este bioma e sobre a prática da subirrigação. O trabalho Análise da Subirrigação em Várzeas Tropicais foi realizado com o objetivo de analisar o comportamento deste método de irrigação, através do monitoramento dos níveis de água nos canais e no lençol freático, da produtividade e outros parâmetros complementares. A pesquisa foi realizada na àrea do Projeto Rio Formoso em Formoso do Araguaia – TO durante a entressafra 2009, explorada com a cultura da soja destinada à produção de sementes, local onde esta prática é utilizada constantemente desde o ano de 1981. O acompanhamento da cultura e os resultados obtidos demonstraram que este método de irrigação atendeu parcialmente a demanda hídrica básica da cultura instalada. Nos trinta pontos monitorados, tanto a produtividade como o nível médio do lençol freático apresentaram individualmente grandes variações entre si. Não houve correlação significativa entre a variação do nível do lençol freático com a produtividade, com a distância dos canais terciários de irrigação e drenagem e com a evapotranspiração máxima. Também não houve correlação da produtividade com a distância dos canais terciários de irrigação e drenagem e nem com a granulometria do solo. / The Tropical Floodplains in the state of Tocantins are intensively farmed with two annual irrigated crops: flood irrigated rice in the rainy season and various higher added value crops using the subirrigation method between harvests during the dry period. There is lack of technical information about this biome and about the practice of subirrigation. The study “Analysis of Subirrigation in Tropical Floodplains” was done to analyze the behavior of this irrigation method by monitoring the water levels in the canals and water table, yield and other complementary parameters. The study was performed in the Rio Formoso Project area, in Formoso do Araguaia, state of Tocantins (TO), during the period between harvests in 2009, with a soybean crop for seeds. This has been a continuous local practice since 1981. The follow up of the crop and the results obtained showed that this irrigation method partially covered the basic water demand of the installed crop. At the thirty points monitored, both yield and mean level of the water table individually presented great variations in relation to each other. There was no significant correlation between the water table variation and yield, distance from the tertiary irrigation and drainage canals and maximum evapotranspiration. There was also no correlation between yield and distance from the tertiary irrigation and drainage canals or soil grain size.