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Adsorption and precipitation of Cd2+ in soil suspensions were investigated as possible factors controlling Cd2+ levels in soils. Both adsorption of Cd2+ onto soils surfaces and possibly precipitation of cadmium minerals were evident in this study. At low cadmium levels solubility relationships in soils are best described by adsorption and fit the empirical Freundlich adsorption isotherm. Based on current thermodynamic data the solid phases CdCO3 (log Ksp = −12.07) and Cd3(PO4)2 (log Ksp = −32.61) most likely limit Cd2+ activities in soils. Under alkaline conditions, Cd2+ activity decreased approximately 100‐fold for each unit increase in pH. In this study, CdCO3 precipitated in sandy soils, having low cation exchange capacity (CEC), low organic matter, and pH values >7.0.DTPA‐extractable cadmium levels in soils were highly correlated (r = 0.96) with Cd concentrations in corn (Zea mays L.) seedlings grown on soils amended with Cd solutions, sewage sludge, or Cd‐spiked sewage sludge. Increasing Cd additions to the soil increased plant Cd regardless of the form of Cd added. Addition of inorganic Cd to the soil increased the Cd concentration of corn seedlings more than equivalent Cd additions in the form of sewage sludge or Cd‐spiked sludge.

Sugarcane (a complex trispecies hybrid of Saccharum) is one of few crops which are highly responsive to applications of silicate materials. Variety ‘C.P. 63‐588’ was grown on a Pahokee muck soil (euic, hyperthermic Lithic Medisaprist) to evaluate effects of silicate sources and rates on growth of cane and sugar yield. Data were collected from the initial planting and a subsequent ratoon crop. Silicate materials were applied to 79.2 m2 field plots at the rates of 0, 5, 10, 15, and 20 metric tons/ha of TVA slag, Florida slag, and Portland cement. A factorial experiment was established in a randomized complete block design with five replications. The silicate materials were broadcast by hand and then thoroughly mixed with the soil by a disc harrow. Growth was measured as plant height, stem diameter, and number of millable stalks. Yield was determined as metric tons of cane and sugar per ha. Application of silicate materials increased plant height, stem diameter, number of millable stalks, and cane and sugar yields in both plant and ratoon crops. Addition of 15 metric tons/ha of silicate materials increased cane and sugar yields by 68 and 79% in the plant crop, and by 125 and 129% in the ratoon crop, respectively. Although there was no significant difference among the silicate materials in the plant crop, Florida slag increased growth and yield more than the other two materials in the ratoon crop. The vital role of Si in sugarcane growth was evident by increased plant size and increased tillering.