Phosphorus and magnesium fertilization interaction with soil phosphorus level: tall fescue yield and mineral element content.
1997
Reinbott T.M. | Blevins D.G.
In a previous study, P fertilization of tall fescue (Festuca arundinacea 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 was to determine whether annual P and Mg fertilization of a soil with Bray-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. In early March of each year, 25 lb P/acre and/or 15 lb Mg/acre were broadcast 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 fertilization increased leaf Mg, Ca, and P content in late March/early April. The greatest increase in leaf content of these mineral elements occurred when Bray-1 P was less than 16 lb/acre. Magnesium fertilization increased leaf Mg content only when Bray-1 P was 26 lb/acre or greater, with or without P fertilization. Forage yield in May was over 1000 lb/acre greater with annual P fertilization than without when soil P was less than 16 lb/acre. Annual applications of 25 lb P/acre were as effective as building soil P above 26 lb/acre for increasing forage yield and early spring leaf Mg and Ca content. The Mg and Ca contents of forage harvested in May were lower than those of leaves sampled in early spring and this resulted from the large number of stems, which are lower 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 mineral element content in early spring.
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