Effect of P, K, and Lime on Growth, Composition, and 32p Absorption by

this isotope satisfactorily reflected the absorptive ca­ Information is needed concerning the effects of dif­ fercllt soil fertility IcveI.~ on the activity of turfgrass roots in that part of the soil profile sampled for routine soil tests. In Pennsylvania, a sampling depth of 5 to 7.5 em is suggested for established turf. A study was cond ucted on 'Merion' Kentucky bluegrass (Poa praten­ sis L.) to determine relationships among lime, phosphorus, and potassium applications; soil test results; foliar growth and elemental analysis; and mot activity as determined by ""P uptake from three soil depths. In the field, soil pH values were 5.8 and 7.0, P ranged from 13 to 137 ppm, and K ranged from 0.14 to 0.43 meq./loog. Liming increased the Ca content in clippings fwm 0.35 to 0.42%. Phosphorus treatments increased P from 0.32 to 0.44%, and K was increased from 2.00 to 2.45% by K fertiliza· tion. Clipping yield was increased by P treatments. Sod plugs from the field were used in the greenhouse to detennine root activity. Agar discs containing :l2p were placed at a depth of 1.3, 3.8, or 6.4 em, and clippings were assayed for B2p after 20 and 33 days. Shallow place­ ment of "'P resulted in more absorption. A soil P X depth interaction was found for "'P absorption. A sig­ nificant positive correlation between soil P and "2P ab­ sorption was obtained for the 1.3 em depth, whereas a nonsignificant correlation was found for the 6.4 em placement. Results indicated that P enhanced root­ ing, and the magnitude of absorption from the I.3·cm depth exemplified the need fm· P lIear the soil surface for optimum turf establishment.