BORON RELEASE FROM FLY-ASH AND ITS UPTAKE BY CORN

The increasing costs of disposing of fly ash create an urgent need to find potential uses, one of which is land application to improve physi cal or chemical properties of soils. Because fly ash contains consider able amounts of B, which is often deficient in Southeastern soils, B r elease from fly ash and its uptake by corn (Zea mays L.) were investig ated initially under greenhouse conditions. Two fly ashes from Georgia were tested as a source of B for corn grown on two soils of different texture (Cecil: clayey, kaolinitic, thermic Typic Kanhapludult, and L akeland: thermic, coated Typic Quartzipsamment). Fresh (unweathered) f ly ash was applied to Cecil soil at rates equal to 0.0, 3.1, 6.3, 12.5 , 25, 50, and 100 g kg-1 soil, while the Lakeland soil being sandier r eceived one-half of these rates. Hot water extractable B content of fl y ash increased with decreasing pH and both soils showed a linear rela tionship between fly ash rate and hot water extractable soil B. Soil p H was the main factor influencing B release from fly ash in soil-fly a sh systems (at given fly ash rate). Increased rates of B application i n fly ash resulted in much higher tissue B contents and caused marked reductions in growth on both soils. Tissue B contents on the sandy Lak eland soil were higher at the same ash rate than on the heavier Cecil soil. Hot water extractable soil B is a good diagnostic criterion for evaluation of B availability to plants on fly ash amended soils.