Soil amendments can improve soil quality by neutralizing soil acidity and increasing soil's holding capacity for nutrients and moisture. The objectives of this greenhouse study were to evaluate the agronomic effectiveness and the nutritional value of the organic amendment, and to assess any potential risk of heavy metals in using the material. The organic amendment used in this study was made of biosolids, palletized and containing significant amounts of nutrients and organic C. Application of organic amendment at 1.25, 5, and 10 g kg-1 increased plant dry matter yield on a Spodosol, but no significant difference in yield was observed among the three treatments. Plant biomass yield on the Alfisol slightly decreased at low application rate (1.25 g kg-1), but increased at higher application rates (5 and 10 g kg-1). There was no difference in leave chlorophyll content and plant N concentration among the different treatments for both soils. Plant N concentrations were around 20 to 23 g kg-1 P. Plant concentration was similar for all treatments on both soils except for the treatment of 10 g kg-1 of organic amendment on the Alfisol, in which plant P concentration was slightly lower. However, organic amendment increased plant K concentration on both soils, but had minimal effects on plant nutrition of Ca, Mg, Fe, Al, and Na. Plant Zn and Mn concentrations generally increased, whereas plant Cu and Cr concentrations decreased in Alfisol by organic amendment. The effects of organic amendment on plant Cd, Co, Ni, and Pb concentrations were either minimal (Pb) or inconsistent (Cd, Co, and Ni). These results indicate that use of the organic amendment seems beneficial to crop production and poses minimal risk of heavy metal contamination to food chain.
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