Reclamation of Quartz Sand‐Tailings from Phosphate Mining: I. Tropical Forage Grasses

Abstract

AbstractPhosphate mining in Florida produces waste products of phosphatic colloidal material and quartz sand. Quartz sand‐tailings disposal areas cover 20–60 ha and support no vegetation. A split‐plot field experiment was conducted to study the production, quality, and nutrient concentration of five tropical grasses: (i) ‘McCaleb’ stargrass (Cynodon aethiopicus Clayton et Harlan), (ii) ‘Transvala’ digitgrass (Digitaria decumbens Stent.), (iii) ‘Pensacola’ bahiagrass (Paspalum notatum Flugge), (iv) ‘Ona’ stargrass (Cynodon niemfuensis Vanderyst var. niemfuensis), and (v) ‘Callie’ bermudagrass (Cynodon dactylon var. aridus Harlan et deWet), grown on four amended sand‐tailing treatments. These treatments were: (i) sand‐tailing control (SC), (ii) colloidal phosphate (CP) at 336 metric tons/ha, (iii) CP at 336 metric tons/ha + oven‐dry sewage sludge (SS) at 45 metric tons/ha, and (iv) CP at 336 metric tons/ha + top soil (TS) at 1,460 metric tons/ha.Generally all grasses produced highest dry matter yields when grown on CP + SS and CP + TS amended sand‐tailing treatments during the first 2 years of the experiment; however, during the 3rd year no difference (P <0.05) was obtained among amendment treatments. Highest forage production during all 3 years was obtained from Callie bermudagrass (average of 14.4 metric tons/ha). Amendment treatments had no effect on forage quality (in vitro organic matter digestion [IVOMD] and crude protein) of perennial grasses, with Transvala digitgrass usually averaging the highest percentage IVOMD and crude protein. Transvala digitgrass also contained the highest nutrient concentrations (P, 0.39%; K, 1.55%; Ca, 0.62% and Mg, 0.26%).