This study was conducted to determine the effect of N fertilizer and irrigation management on potato (Sotanum tuberosum L,) tuber N0,-N levels and the relationship to the potential health hazard created by high nitrate levels in food products.Russet Burbank' potatoes grown using different N fertilizer rates, methods of application, and irrigation levels were analyzed for N0,-N concentration. The NO,-N concentration in the tubers on a wet weight basis varied from 36 to 131, 34 to 75, and 25 to 50 ppm in the 3 years of this study. The NO,-N concentration for each year of study was found to be directly related to the level of applied N fertilizer. The initial concentration and increase in N0,•N due to N fertilizer varied with the season. The addition of manure did not increase the N0,-N level above those to be expected from similar quantities of inorganic sources of N. Phosphorus fertilizer did not increase the N0,-N level. The N0,-N concentration in the tubers where more water was applied at each irrigation was less than on the lower level of applied water at each N rate. These data indicate that greater NO,-N levels in the tubers will result by increasing N fertilization rates. The levels of N0,•N obtained in this study were not expected to contribute substantially to the methemoglobinemia health hazard. There is considerable concern that use of these high nitrate containing vegetables could cause methemoglobinemia, especially in infants. Although nitrites are the toxic principle which may be formed prior to ingestion or during digestion and absorption of food, nitrates may be considered as the index or precursor to the amount of nitrite which may be formed. If foods contain high levels of nitrate, the potential hazard may be increased if conditions during storage or processing are conducive to conversion to nitrite (11). In spite of the appreciable nitrate content of some vegetables such as beets and spinach, no authenticated cases are known for nitrate poisoning of human adults. However, several cases of methemoglobinemia and one death have been reported recently when children, aged 2 to 10 months, were fed spinach purchased as a fresh vegetable and held under questionable storage conditions (1).In recent years, there has been a steady increase in the use of nitrogeh fertilizer to achieve maximum potato production. Also, an increasingly common practice is to add N to the irrigation water 1 Contribution from the Western Region, Agricultural Research Service, USDA; Idaho Agricultural Experiment Station cooperating. Received Aug. 13, 1973. 'Soil Scientist and Physcial Science Technician, respectively, Snake River Conservation Research Center, Rimberly, ID 83341.Mention of trade names or companies is for the benefit of the reader and does not imply endorsement by the USDA. throughout the season, The abundance and low cost of N fertilizer has encouraged the use of high fertilization rates in attempts to obtain maximum tuber yields. No reported cases could be found in the literature where high nitrate level...
Nitrate-nitrogen in sugarbeet petioles is used to evaluate current N status of sugarbeet crops. Since the NO,-N changes rapidly during the season, better relationships are needed to interpret these data relative to sugarbeet N nutrition.Sugarbeets (Beta vulgaris, L.) were grown at four N fertilization rates and two irrigation levels to determine the root yield, sucrose percentage, sucrose yield, and N uptake in relation to the NO,-N concentration in the petioles. NO,-N in beet petioles increased to a peak concentration and then decreased exponentially during the two growing seasons on all treatments. The exponential decrease after the peak enables prediction of the NO,-N in the petioles during the remainder of the growing season. This rate of change approach can be used to predict N needs when adding supplemental N for sugarbeets and to characterize the N status of soil-crop systems.Additional index words: Petiole analysis, Nitrogen uptake.
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