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Biochar is being studied for few decades as it finds various applications in mitigating climate change, improving soil properties and water retention which subsequently potentially improves the crop yields. One of the parameters potentially predicting the crop yield is the crop density during the vegetation period as it represents the number of plants per area unit that can photosynthesize and potentially bring yield at the end of vegetation season. The paper presents the observations on the changes in canopy density during the vegetative part of the vegetation season of maize (Zea mays L.) which was estimated using non-destructive method of close canopy imagery. The field observations were done at the experimental site in Dolna Malanta near Nitra (Slovakia). In 2014, a commercially purchased soil additive (biochar mixed with compost - BC) was applied to plots (4 x 6 m of size) of agricultural land in the rates of 0, 10 and 20 t/ha. The application rates of BC were combined with 3 levels of NPK fertilizer application (0, 160 and 240 kg N/ha). During the observation period from mid-May 2015 up to beginning of July 2015, images of maize canopy parallel to soil surface were taken from above the crop canopy with camera built up in the mobile. The canopy density was evaluated using the Breedpix software. The canopy density three weeks after sowing ranged from 1.7 to 2.1 % at the control treatments (without BC) at different fertilization levels. The values at treatments with BC ranged from 2.1 up to 2.4 and from 1.9 up to 2.6 % at the application rate 10 and 20 t/ha, respectively. Although in general higher values were observed at treatments with BC application, the differences were not significant. The canopy density over the studied period increased in all treatments, at the end of June the values ranged from 39 to 40 % at the treatments without BC and from 39 to 46 % at treatments with BC at 10 t/ha and from 38 up to 58 % at the treatments with BC at 20 t/ha application rate. Although majority of differences were not statistically significant, it can be concluded that overall biochar mixed with compost slightly increased the density of the maize canopy at least in the early stages of the development. As the maize height was increasing, the sampling method was not suitable as it was not possible to take image of the full canopy within the row. For such applications it might be useful to take photos from larger height preferably with UAV. [ABSTRACT FROM AUTHOR]