EFFECTS OF PREPLANT DEEP TILLAGE OF SOIL AMENDMENTS ON SOIL MINERAL ANALYSIS, CITRUS GROWTH, PRODUCTION AND TREE HEALTH

Two rates of peat, shrimp hull waste, humate, bentonite clay, gypsum, and a calcium humate were preplant strip tilled 1.2 m deep and 1.6 m wide down the center of row in a new citrus grove site 13 km southeast of St. Cloud, FL, to determine their effects on soil mineral analysis, tree growth, fruit production, and health. Gypsum and calcium humate were reapplied to surface soil annually and humate was reapplied twice, 3 and 5 years after planting. Nine months after the first application, Ca, Mg, K, S, Cu, B, Fe and Zn were highest in soil of the humate treatment, no other amendment appeared to influence soil minerals; 27 months after treatment none of the amendments altered major changes in soil minerals. Hexosamines were significantly higher in soil treated with shrimp waste than the control 5 months after application but not 21 months after application. No treatment caused a significant increase in trunk caliper in each of 3 years beginning in 1985. Cumulative ratings for foot rot caused by Phytophthora parasitica for each treatment from 1985 to 1988 showed that gypsum significantly reduced foot rot. This effect may have been the result of the increase in leaf Ca and S and bark Ca, in the gypsum treatment. Fruit production in 1989 and early development of blight symptoms in 1989 and 1990 were not significantly different from the control.