Abstract

Given the importance of organic soil amendments and the increase in the use of compost and compost tea in Chilean agriculture, the objective of this study was to measure the quality of amendments commonly used in northern central Chile. A total of five samples of solid (compost and humus) and seven samples of liquid (compost and humus tea) soil amendments were evaluated. Analysis of toxicity, human pathogens, microbiological indicators, and physical-chemical composition were assessed and compared to the Chilean compost quality standard. The presence of soil beneficial microorganisms and biochemical parameters associated with dehydrogenase activity (UDH), urease (UU), acid and alkaline phosphatase (UPac, UPalk), and beta-glucosidase (UBG) were also evaluated. Beneficial microorganisms were present in 90% of all analyzed samples, and high enzymatic activity was detected in solid samples (UBG: 103-347 [mu g p-nitrophenol/h*g], UPac: 761-1470 [mu g p-nitrophenol/h*g], UPalk: 811-2615 [mu g p-nitrophenol/h*g], UU: 151-729 [mu g NH4/h*g], UDH: 122-378 [mu g TFP/24 h*g]). This indicates the potential for active mineralization processes that can contribute to nutrient availability in soils. None of the solid samples met the regulatory limit for organic matter content, indicating deficient compost production processes. One in five of all samples exceeded the threshold for fecal coliforms (<1000 NMP/g or ml). It is indispensable to have adequate control processes in place to ensure food safety along with agronomical benefits when these products are utilized in agriculture.