Cultivation of unicellular green algae as an assessment of soil fertility

Abstract This paper attempts to assess the use of the unicellular green lga, Chlorella pyrenoidosa , as an indicator of the fertility of several soil types, namely red-yellow podzol, red earth, garden soil, sludge-amended garden soil, iron-ore tailings and eroded soil (red-yellow podzol). C. pyrenoidosa was cultivated in the water extracts of the above samples in the laboratory. It was discovered that a descending order of growth rate and chlorophyll content of the algae was obtained: garden soil, sludge-amended garden soil, red-yellow podzol, red earth, eroded soil and iron-ore tailings. In order to test the soil fertility for higher plants, tomato Lycopersicon esculentum was cultivated in the soil samples for a period of two months. Dry weights of the crops were measured at the end of the trial period. The results, in descending order of dry weight, were as follows: garden soil, red-yellow podzol, sludge-amended garden soil, red earth, iron-ore tailings and eroded soil. A soil chemical nutrient analysis was also carried out and it was found that the soils which gave higher production of both plants were rich in macronutrients, i.e. total nitrogen, water-soluble phosphorus, exchangeable potassium, calcium, magnesium and sodium, with the exception of the iron-ore tailings. The last possessed a higher content of trace elements, e.g. iron, lead, copper, manganese and chromium, which would inhibit the growth of both flora, although a rather higher content of macronutrients also existed. According to the above results, it was concluded that cultivation of unicellular green algae in soil extracts may be used for assessing the chemical contents of the soils. However, more detailed experiments involving more species of both algae and higher plants and soil types should be conducted before a definite conclusion can be drawn.