Effects of Rates of N and P on the Accumulation of NO3-N in Wheat, Oats, Rye and Barley on Different Sampling Dates
1971
Baker, J. M. | Tucker, B. B.
The NO₃-N concentration of wheat, oats, rye, and barley forage was found to be a function of rate of N fertilization, P fertilization, and date of sampling. The crops were not very different with respect to NO₃-N accumulation, though barley and wheat appeared to accumulate more nitrates than rye or oats during periods of highest concentration. Nitrate-nitrogen concentrations were highest hi samples collected March 18 and 24 when the plants were in the “joint” or “preboot” stage of growth. Concentrations greater than 3,500 ppm were not uncommon in barley and wheat samples collected at these stages of growth, whereas oat and rye samples rarely exceeded 3,500 ppm. The NO₃-N concentrations rarely exceeded the potentially toxic level of 2,100 ppm when 90 kg/ha or less N was applied, a rate that is as high as is typically applied to dryland winter wheat. The NO₃-N concentration declined sharply after the March 24 sampling date and continued to decline through the April 13 sampling date. A slight increase in concentration appeared late in the season, especially in oats. The tendency for NO₃-N accumulation to be increased by a deficiency of P was also found. The concentration in wheat forage was reduced from 1,300 ppm to 300 ppm NO₃-N with the application of 15 kg/ha P. P rates beyond that necessary for maximum grain production did not further reduce the NO₃-N content of the forage.
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