Effects of N and K Fertilization on the Protein, Nitrate and Nonprotein Reduced N Fractions of Timothy and Bromegrass

Timothy (Phleum pratense L.) and bromegrass (Bromus inermis Leyss.) were grown in field experiments to evaluate the effects of N and K fertilization on protein, nitrate and nonprotein reduced N concentration in the forage. Concentrations of all N fractions studied generally increased as the rate of N application was increased. At high rates of N application (448 and 896 kg N/ha) nitrate N concentrations increased when rates of K application were increased from 56 to 440 kg/ha. Highest nitrate N concentrations were 0.37 and 0.43% for timothy and bromegrass, respectively. These were obtained at highest rates of N and K application (896 kg N/ha and 440 kg K/ha). Highest concentrations of nonprotein reduced N were 1.20 and 1.11% for timothy and bromegrass, respectively. Although the highest concentrations of nonprotein reduced N were obtained at highest rates of N and K application, rate of K application had no significant effect on this fraction.