Potassium did not accumulate in these soils in spite of re-
cycling by the grazing animal and annual K application. In some
years, extractable K in the surface soil was higher than in virgin
soil, but in 1972 extractable K in soils treated for 21 years and
in virgin soils was essentially identical. Small additional amounts
were present in the soil profile, and some was utilized by grasses
fertilized with N. However, for legume-grass pastures annual
K fertilization is essential.
 Calcium and Mg were adequate for optimum plant growth as
evidenced by soil levels and plant composition. Calcium/Mg
ratios throughout Phase 3 of this study were in the range of
12 to 20. These were somewhat higher than considered ideal for
many soils, but the strong affinity of exchange sites on organic
matter for Ca relative to Mg permits adequate Mg for plant nu-
trition over a wide range of ratios. Probably a more important
consideration is maintenance of reasonably high levels of Mg in
the soil. Quantities in the range of 110 to 150 pounds per acre
were adequate.
 Supplementary studies confirmed the continuing need for N
and K in pasture production and the adequacy of other accumu-
lated nutrients over a 3-year period of intensive forage pro-
duction.
 Excellent legume-grass pastures can be grown following
treatments used at the Beef Research Unit, if the correct legume-
soil combinations, based primarily on moisture relationships, are
selected. The first priority is a lime program which will maintain
soil pH at approximately 6.0 and Ca/Mg ratios in the range of
10 to 15. Soil analyses will be useful in maintaining adequate pH
and nutrient levels. Annual fertilization with P, K, and S is es-
sential. Eventually P fertilization can be reduced, as this element
accumulates in the soil. Potassium must be applied annually.
Micronutrients should be applied initially and periodically ac-
cording to recommendations.

 Literature Cited
 (Soil Studies)
 1. Andrew, C. S., and D. O. Norris. 1961. Comparative responses to cal-
 cium of five tropical and four temperate pasture legume species. Aust.
 J. Agr. Rev. 12:40-55.
 2. Blue, W. G. 1970. The recovery of autumn and winter applied potassium
 by a warm-season grass from Leon fine sand. Soil and Crop. Sci. Soc.
 Fla. Proc. 30:9-15.
 3. Blue, W. G. 1970. The effect of lime on retention of fertilizer phos-
 phorous in Leon fine sand. Soil and Crop Sci. Soc. Fla. Proc. 30:141-150.