THE ACCUMULATION OF BORON IN AGROPYRON ELONGATUM GROWN IN COAL FLY-ASH AND SEWAGE-SLUDGE MIXTURE

A greenhouse pot experiment was conducted to investigate the boron (B) release capacity of coal fly ash and sewage sludge mixtures, and the accumulation of B in Agropyron elongatum after two consecutive growing seasons. Sludge was amended with fly ash at application rates of 0, 5 , 10, 35, and 50% (w/w), and each mixture was then mixed with a loamy soil at either 1:1 or 1:5 (v/v). Both water soluble B (WS-B) and hot w ater soluble B (HWS-B) increased with increasing fly ash amendment rat e. Shoot B concentrations also increased significantly according to th e rate of ash amendment. The ash-sludge mixture improved plant growth with the highest total dry weight yield at 10% ash amendment rate. Bor on toxicity symptoms in leaf rips were observed at 35% and 50% ash ame ndment rate at both soil mixing ratios. Hot water soluble B and WS-B d ecreased significantly after consecutive cropping of Agropyron especia lly at low ratio of mixure with soil i.e., 1:5 (v/v). However, soil av ailable B contents at greater than or equal to 35% ash application rat e and 1:1 (v/v) soil mixing ratio were still excessive for normal plan t growth, suggesting that deleterious effects or! plant growth would b e experienced in later seasons owing to the high amounts of residual B .