sweet corn, silage maize) groups. The sensitive plants can be treated by digestate only in their certain life stages, for example, young alfalfa is very sensitive after sowing while old alfalfa is very sensitive before cutting. In the case of sensitive plants the burning effect of digestate can be observed but it follows a strong and quick recovering process. For the non­sensitive plants the digestate can be used in any developmental stage. It is favourable, because for example, in rainy period the digestate technically could not be applied (Makadi et al., 2008).

The right application rate of liquid or solid digestate depends on the plant nitrogen demand. It should be applied when plant N demand arises. This time for non-legume scpecies is the late winter and spring (Stinner et al., 2008). Similarly, Wulf et al. (2006) used 70% of the digestate in spring and 30% in autumn, while Makadi et al. (2008) and Nyord et al. (2008) split into two and three the applied rate through the vegetation period.

Because of its high available nutrient content, digestate application resulted in significantly higher aboveground biomass yields in the case of winter wheat and spring wheat than the farmyard manure and undigested slurry treatment. The effectiveness of a digestate depends on the composition of co-digestied material, the treated plant species and the treatment methodology. Co-digestion of different organic materials results in more effective digestate. (Moller et al., 2008; Stinner et al., 2008).

After the burning effect of digestate the soybean plants recovered and grew more, but lower sprouts. These sprouts were very productive, the number of pods was also higher in the treated samples, therefore the yield and thousand seed weight were also higher (Table 7, Makadi et al., 2006)

These yield parameters are close correlations with some soil parameters changing after digestate amendment. Increasing in important nutrient contents contribute to the better development of plants (Makadi et al., 2008b, Table 8).

Comparing the effect of liquid digestate and the equal quantity of water to the yield of sweet corn and silage maize, significantly higher yields were found in the digestate treatment. In this case the applied digestate on the bases of plants N demand was split into two parts (Makadi et al., 2006). That means that the favourable effects of digestate are caused by its soluble macro — and micronutrient content.

Comparing the effect of digestate and a bacterial manure (Phylazonit MC, the experimental conditions can be found in the section 4.5). The Phylazonit MC treatment increased the green weight of silage maize by 47.18% while the digestate by 142.34%, comparing to the control. The results obtained can be seen in Table 9 (Makadi et al., 2007).

The positive effect of Phylazonit MC treatment was the result of its microbes, plant growth promoters and microelement content, while the favourable effect of digestate treatment was caused by its macro — and microelement and high water content and the increase of soluble macroelement content of soil because of the increased microbial activity.