PAPER-MILL SLUDGE, PHOSPHORUS, POTASSIUM, AND LIME EFFECT ON CLOVER GROWN ON A MINE SOIL

Pots containing mine soil treated with lime, fertilizer, and bleached, primary papermill sludge (at the rate of 56, 112, and 224 Mg/ha added alone or in combination with fertilizer [P and K]) were planted to subterranean clover (Trifolium subterranean L.) in the first phase of a two-phase study. Fertilizer was found necessary to revegetate the mine soil, and the addition of sludge and fertilizer significantly (alpha < 0.05) increased yield over the fertilizer only. This favorable effect of sludge was observed during the second harvest, with 112 Mg/ha giving the maximum yield. Biological N2 fixation and native N did not raise the N concentration in clover within the normal range (2.9-3.8%). Fertilizer application improved N uptake by the forage. The N concentration in clover declined with successive harvests. However, sludge application minimized this decline. Phosphorus was found to be at normal range (0.1-0.2%) in all cases, except at the sludge rate of 112 and 224 Mg/ha without fertilizer. Excessive tissue concentrations of K, Ca, S, Fe, Cu, Zn, and Al were observed in the unfertilized mine soil and K, Ca, Zn, and Al were excessive in all treatments.