Acute toxicity of experimental fertilizers made of blood meal, spent coffee ground and biomass ash

Abstract

Abstract The study presents the results of research on the acute toxicity of a fertilizer formulas made of spent coffee ground (SCG) with addition of ash from low-temperature combustion of biomass or ash with an admixture of magnesium sulphate and blood meal. The experimental fertilizer formulas included also rape oil used as a plasticizer for controlling the nutrients release from the fertiliser. Mustard (Sinapis alba L.), oats (Avena sativa sp. L.), cucumber (Cucumis sativus L.) and cress (Lepidium sativum L.) were used as test plants species in the experiment. The toxicity tests were performed using a standard procedure of 72 h with the use of Phytotoxkit microbiotest and fertilizer application of 2.5; 5 and 10% (v/v). The obtained results indicated an increase of acute toxicity for all tested plant species, proportionally to the applied doses of the fertilizer. During the 72 h period, the strongest inhibition of seedling growth was recorded in samples consisting of 10% of the tested fertilizers, particularly when they showed considerable level of salinity or low pH values. From the tested plant species, cress (Lepidium sativum L.) turned out to be the most sensitive to the applied fertilizers, the least was cucumber (Cucumis sativus L.) for which only a small inhibition of root system growth was observed. The inhibited growth of roots could be attributed to a reduced oxygen access and excessive salinity of the substratum caused by the applied additives.