Reed canarygrass yield, crude protein, and nitrate N response to fertilizer N

Reed canarygrass (Phalaris arundinacea L.) Is a high-yielding, cool-season forage that responds to high rates of N. Forage growers need additional inf ormation on N management strategies for improving production without induci ng negative consequences. Three, 1-yr studies were conducted from 1992 to 1 994 on a Webster clay loam (fine-loamy, mixed, superactive, mesic Typic End oaquolls) in southern Minnesota to determine the optimum rate of N and the effect of split applications of N on forage yield, crude protein (CP), fora ge nitrate N concentration, and residual soil nitrate (RSN), Ammonium nitra te was topdressed to established stands of reed canarygrass at rates from 0 to 600 lb N/acre, Single, early-season (April or May) applications were co mpared with split applications (early-season + after first cutting). Total dry matter (DM) production was optimized by N rates totaling 250 to 300 lb/ acre in 1992 and 1993 and by only 150 to 200 lb/acre in the lower yielding year, 1994, Split applications of N did not further improve DM yields above those obtained with the optimum N rate applied as a single, early-season t reatment, Forage nitrate N concentrations ranged from 40 to 7230 ppm (>3000 is considered dangerous) and were greatly influenced by rate and time of N application and growing season conditions. Residual soil nitrate did not a ccumulate until the agronomic optimum N rate was exceeded by 100 lb/acre, R esults from this study indicate that DM yield and CP percentage of reed can arygrass can be optimized with high rates of N applied early in the season, but undesirably high concentrations of nitrate N in the forage should be e xpected when optimum rates of fertilizer N are exceeded.