RESPONSE OF TALL FESCUE TO FERTILIZER PLACEMENT AT DIFFERENT LEVELS OF PHOSPHORUS, POTASSIUM, AND SOIL-PH

Fertilizer application, particularly nitrogen (N), is important in coo l-season grass forage production. Subsurface (knife) placement of N of ten has resulted in higher forage yield and N uptake of tall fescue (F estuca arundinacea Schreb.) compared to surface-broadcast fertilizatio n, but further studies were needed to indicate whether soil pH, phosph orus (P), or potassium (K) modifies the response. Experiment I tested responses of forage yield and N and P concentration to N, P, and K amo unt and placement. Two types of fertilizer placement - broadcast and k nife - were used with 13, 112, or 168 kg N; 0 or 19 kg P; and 0 or 37 kg K/ha in a factorial arrangement. Yields increased by 53% as N ferti lization went from 13 to 112 kg/ha and by 69% as N increased from 13 t o 168 kg N/ha. Forage yield was increased 26% from knife compared to b roadcast fertilizer placement. P application increased forage producti on by 13%, but K application had no effect on yield. Forage N concentr ations increased by 25% as N fertilization went from 13 to 112 kg/ha a nd by 38% as N increased from 13 to 168 kg N/ha. Effects of added P an d fertilizer placement on N concentration often resulted in interactio ns among factors. Forage P generally was increased by added P, with so me effects of interactions among N rate, P rate, and placement. In Exp eriment II, fescue responses to N placement were tested where differen t soil characteristics had been established by previous lime and ferti lity treatments. Forage yield, N concentration, and N uptake were high est where 9.36 Mg/ha of lime were applied as compared to the control. Previous fertility treatments had no significant (P<0.05) effect. When N was knifed, forage yield was related positively to available soil P but not to pH or K. Yield and forage N concentration and uptake were increased by 20, 11, and 33%, respectively, as a result of knife versu s broadcast N application.