Forage Production and N Contents, and Soil Changes During 25 Years of Continuous White Clover-Pensacola Bahiagrass Growth on a Florida Spodosol

This experiment was established in 1952 with white clover (Trifolium repens L.) and Pensacola bahiagrass (Paspalum notatum Flugge) on virgin Myakka fine sand (sandy, siliceous, hyperthermic Aeric Haplaquod) at the Beef Research Unit near Gainesville, Fla., to evaluate the effects of lime and micronutrients on white clover-grass production and N fixation, the persistence of this combination of plants under good management, and their effects on the soil. Initial treatments consisted of one without lime and nine with calcitic lime at 5 metric tons/ha incorporated into the soil to a depth of 15 cm. Two of the limed treatments were without micronutrients; the remaining seven included a variety of B source and experimental frit materials. The experimental area was seeded to Pensacola bahiagrass in July and overseeded with white clover in October. Nitrogen, P, and K were uniformly applied to all plot areas through 1957; subsequently only P and K were applied. Micronutrients were reapplied periodically to plots which received them initially and lime was surface applied as needed. All forage was removed from the experimental area. Oven-dry forage was increased by lime from 3,870 to 9,660 kg/ha per year. The percentage increase in forage N was similar even though N was applied to all treatments during the first 5 years. Forage yield and N content were increased additionally by micronutrient treatments. Soil organic matter was approximately twice as high in 1977 as in 1953. Total soil N increased from 1,180 to 2,560 kg/ha where lime was applied. Where lime was omitted and white clover did not grow, soil N still increased by approximately 800 kg/ha. Exchangeable A1 was eliminated by liming, but was reduced only slightly by phosphate additions. Cation exchange capacity determined by NH₄,OAc (pH 7.0) was 2 meq/100 g for each percent of organic matter in soils collected in 1953. In 1977, it was 1.36 and 1.68 meq/100 g for each percent organic matter in unlimed and limed soils, respectively. Very little K accumulated even in unlimed soil where removal by plants was small.