Nitrate-N and Total N Concentration Relationships in Several Plant Species
1976
Terman, G. L. | Noggle, J. C. | Hunt, C. M.
Accumulation of NO₃-N in plants is important in regard to plant N nutritional status, in the formation of NO₂-N toxic to animals and people consuming the plants, and as a producer of lethal gas in silos. This paper describes relationships between NO₃-N and total N concentrations in plants grown in several greenhouse pot experiments, as affected largely by response to applied N and by continuing growth. Corn (Zea mays L.) was grown in soil with 200 to 800 mg of N/pot and in nutrient solutions with 2 to 16 ppm of N. Both crops were harvested at 4-day intervals. Spinach (Spinacea oleracea L.) and mustard (Brassica pervirdis L.) were grown in soil with several rates of N, P, and K, and tall rescue (Festuca arundinacea Shreb.) with 1.0 and 2.0 g of N/pot. These experiments conducted on N-deficient soils resulted in marked yield response and higher concentrations of total N and NO₃-N with increase in rates of applied N. Concentrations decreased with age, dry matter accumulation, and depletion of N. Total N was higher in leaves than in stems, but the reverse was true for NO₃-N. Concentrations of NO₃-N started to increase in various crops above minimum total N values of 1.5 to 4.5%, which were highest for leaves, intermediate for leaves + stems, and lowest for stems or petioles. Below these minimum total N values, NO₃-N remained near zero (< 0.1%). Discontinuous regression models appear most satisfactory to fit the entire range of the relationships between total and NO₃-N. It was concluded that NO₃-N concentrations in plants are negligible if the total N was < 1.5% to 4.5%, depending largely on plant part composition, plant species, and N source.
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