Tm. Reinbott et Dg. Blevins, PHOSPHORUS AND MAGNESIUM FERTILIZATION INTERACTION WITH SOIL-PHOSPHORUS LEVEL - TALL FESCUE YIELD AND MINERAL ELEMENT CONTENT, Journal of production agriculture, 10(2), 1997, pp. 260-265
In a previous study, P fertilization of tall fescue (Festuca arundinac
ea Schreb,) pastures increased early spring leaf Mg and Ca content on
low P soils, However, Mg fertilization of these low P soils increased
leaf Mg content only when P was applied, The objective of this study w
as to determine whether annual P and Mg fertilization of a soil with B
ray-1 soil P levels varying from 8 to 97 lb/acre is required in order
to increase Mg, Ca, and P contents, and yield of tall fescue forage. I
n early March of each year, 25 lb P/acre and/or 15 lb Mg/acre were bro
adcast onto plots near Mt. Vernon, MO, containing a Creldon silty clay
loam (fine, mixed, mesic Mollic Fragiudalf) soil, with Bray-1 P tests
of 8, 15, 26, 51, and 97 lb P/acre, At all soil P levels, P fertiliza
tion increased leaf Mg, Ca, and P content in late March/early April, T
he greatest increase in leaf content of these mineral elements occurre
d when Bray-1 P was less than 16 lb/acre, Magnesium fertilization incr
eased leaf Mg content only when Bray-1 P was 26 lb/acre or greater, wi
th or without P fertilization. Forage yield in May was over 1000 lb/ac
re greater with annual P fertilization than without when soil P was le
ss than 16 lb/acre, Annual applications of 25 tb P/acre were as effect
ive as building soil P above 26 lb/acre for increasing forage yield an
d early spring leaf Mg and Ca content. The Mg and Ca contents of forag
e harvested in May were lower than those of leaves sampled in early sp
ring and this resulted from the large number of stems, which are tower
in Mg and Ca content than leaf blades, Annual P fertilization of tall
fescue on low P soils increased both forage production in May and min
eral element content in early spring and made Mg fertilization effecti
ve.