The assumption underlying this study has been that an application of organic-mineral amendments to acid soil with a moderate content of plant available nutrients can help to meet requirements of more than one crop in a particular cropping sequence. This concept was validated in a micro-plot experiment carried out on light soil. Three series of a two-factorial experiment were based on two biofertilizers as the first factor, with contrary ratios of biomass ash and solids of biogas digestate (BAD: FE1, 2.2:1; FE2, 1:2.2). The second factor was a dose of applied BAD: 0.0, 20, 40, 80, 160 or 320 g m-2. Both biofertilizers, but especially EF2 with a high contribution of digestate, significantly affected the uptake of nutrients by vegetables. The observed patterns of nutrient partition among plants organs were modified by the applied soil amendment. The partition indices for radish showed a predisposition of this crop to accumulating K. Any shortage of macronutrients in the soil medium, as exerted by the low dose of BAD based on bio-ash, resulted in higher accumulation of minerals in the root. Green bean grown on plots fertilized with a biofertilizer rich in digestate (FE2) showed higher content of N, P, K, Na, but also Pb. The high ratio of bio-ash in the biofertilizer (FE1) disturbed the partition of Fe among organs of the radish. The soil amendment based on biogas digestate and biomass ash applied in high doses but without adequate enrichment with K and Mg can create a potential threat to the human health. The shortage of these two nutrients creates favourable conditions for the uptake of heavy metals by edible parts of the radish and green bean. Magnesium can be considered to be a mineral agent decreasing the threat of contamination of vegetables by heavy metals.

23.3.2018