Reuse of agricultural waste as bio-fertilizer is a key to closing the nutrient cycle and saving mineral fertilizers. To analyze the effect of two bio-fertilizers in an interaction with three crops grown in a consecutive crop rotation, a micro-plot experiment on poor loamy sand was carried out. Three series of a two-factorial experiment included two bio-fertilizers as the first factor with contrasting ratios of biomass ash and solids of BD (BAD): FE1 (2.2:1) and FE2, (1:2.2). The second factor was a dose of the applied BAD: 0.0, 20, 40, 80, 160, and 320 g m-2. Two crops were grown in a fixed cropping sequence: radish à green bean àradish. The applied BAD fertilizers resulted in very rapid changes in the soil pH, the content of plant available nutrients as well as heavy metals. The pre-plant patterns of the content of nutrients and heavy metals were only slightly modified by the grown crops. The key reason of the observed stability in soil agrochemical properties was the variability in the plant available P, which significantly affected the content of the other elements, including heavy metals. The effect of phosphorus depended on the amount of BD introduced into the soil. Its higher doses resulted in a simultaneous increase in both the soil pH and the P and Ca content. An insufficiently low dose of BAD led to nutrient exhaustion, which was most severe with respect to K, Mg and Ca. The content of available heavy metals under the effect of the soil available P can be taken controlled, provided the content of available K and Zn is increased.

23.1.2018