M.S.

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Increasing levels of nitrate (NO3-) in groundwater have become a major environmental and health concern. In situations where NO3-concentrations in the soil-water system pose an environmental hazard, water table management may be a desirable practice to reduce such pollution. Careful management of N applications is also believed to reduce NO3- levels. / A field experiment was conducted in 1996 and 1997 at St. Emmanuel, Quebec, about 30 km South-West of Macdonald Campus of McGill University, to investigate the effect of water table management (WTM) and N fertilizer combinations on potentially leachable NO3- and denitrification rates in the top soil layer (0--0.15 m). The field was planted with monocrop corn (Zea mays. L) in both years. Treatments consisted of a factorial combination of two water table managements, free drainage (FD) and subirrigation (SI) (about 1.0 m and 0.6 m, respectively, below the soil surface) and two N fertilizer rates, 200 kg ha-1 (N200) and 120 kg ha-1 (N120). / Water table management had a significant effect on reducing NO3 - concentrations in the soil profile. Subirrigation treatment reduced NO3- in the top soil layer by 41% and 15% in 1996 and 1997, respectively. Similarly, NO3 - levels were 50% and 20% lower in N120 compared to N200 treatment. / Climatic conditions (rainfall and temperature) played a large role in regulating denitrification rates. Due to drier and cooler conditions in 1997, denitrification rates were lower compared to 1996, leaving more NO3 - in the soil profile. Following harvest, this high NO 3- concentration may be subject to leaching.

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No description available.

No description available.

A laboratory study of the mobility of Malathion in the soil environment was conducted. / Master of Science

The objectives of the investigation were to relate yield and P uptake of orchard grass grown on Davidson clay loam to P fertilization and to determine the fate and availability of applied and native P in this soil. A further aim of the investigation was to elucidate mechanisms controlling the availability of P to plants in Davidson clay loam that was limed to several pH values. These objectives were accomplished by a study of orchard grass yield data obtained during a long term field investigation and by performance of greenhouse and laboratory experiments. Annual surface application of 21 lb P/A increased orchard grass yield during the initial phase of the field experiment, from 1948 to 1957. Thereafter, from 1958 to 1962, continued application of 21 lb P/A no longer increased yield. Lack of yield response to P application was attributed to plant uptake of residual P. The conclusion was supported by data from a greenhouse study. In the study, P application did not significantly affect yield or P uptake of alfalfa grown on Davidson clay loam that had received annual application of 21 lb P/A for 15 years. Total inorganic P analysis indicated that the major portion of surface applied P remained in the 0-2 inch soil layer. However, statistical analysis of the total inorganic P data showed a significant downward movement of P into the 4-6 inch soil layer. Fractionation analysis indicated the applied and native P was present in Davidson clay loam predominantly as Fe-P. Iron-P made up greater than 70% of the total inorganic P at the 0-2, 2-4, 4-6 and 6-12 inch soil depths. High accumulation of applied P as Fe-P in Davidson clay loam was explained on the basis of the high free Fe oxide content of the soil. Application of either lime or P increased yield and P uptake of alfalfa grown on Davidson clay loam which received annual application of 0 or 10.5 lb P/A for 15 years. From these results it was concluded that liming increased the availability of native and residual P in the soil. Fractionation analysis indicated that the Fe-P fraction decreased to a greater extent than Al-P or Ca-P during growth of alfalfa on the limed soil. These data indicated that liming increased the availability of the Fe-P. Iron P decreased to a greater extent than Al-P or Ca-P during growth of alfalfa on Davidson clay loam that received annual application of O, 10.5 and 21 lb P/A for 15 years. Coefficients of simple correlation for the data, showed a higher correlation between Fe-P than Al-P or Ca-P with P uptake by alfalfa plants. From these data it was concluded that Fe-P was more important than Al-P or Ca-P in supplying P to plants grown on Davidson clay loam. Higher uptake of P from Fe-P rather than from Al-P or Ca-P was explained on the basis of the greater amount of Fe-P in Davidson clay loam. It is suggested that a large percentage of the Fe-P fraction in the soil consists of relatively soluble amorphous compounds. The presence of relatively soluble amorphous Fe-P as well as the high percentage of this compound in the soil then may account for Fe-P being more available than was anticipated. / Ph. D.

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No description available.