The effect of combinations of mineral and organic fertilizers with biochar on the soil properties and sunflower and green pepper yields

A number of studies have shown that biochar from biomass waste pyrolysis is a promising soil amendment material which has the potential to improving soil quality and thus increase crop yields. The objective of this study, therefore, was to determine whether the addition of biochar and biochar with other mineral or organic fertilizers affects soil quality and increase the crop yield in the soils with different particle-size distribution. This study was conducted in two localities (1. Dolná Streda: sandy soil, and 2. Veľké Uľany: loamy soil) with different soil texture. Biochar (B) was applied at rates; 0, 10 and 20 t.ha-1, in sandy soil in combination with urea (M) in dose of 100 kg.ha-1 and in loamy soil in combination with Italpollina (organic fertilizer: OH) in dose of 850 kg.ha-1. Soil samples were taken in autumn 2018. In sandy soil, the tendency of soil organic carbon content (Corg) increase was observed in all treatments, while in loamy soil in B10 and B20 the Corg increased by 11 and 12 % respectively, compared to B0. In sand soil, in B20 + M, soil pH in H2O increased by 0.37 pH unit, while values of soil pH in KCl were significantly increased in B20 and B20+M treatments. Application of biochar and its combinations had significant effect on increase of soil pH in loamy soil. In sandy soil, the values of sum of basic cations in B10, B20, B10 + M and B20 + M increased by 70, 25, 30 and 73%, respectively, compared to B0. On the other hand, the differences between fertilized and unfertilized treatments in loamy soil were not significant. Between soil pH and available P significant negative correlation was observed. Higher soil pH due to biochar application decreased availability of Fe, on the other hand, it increased availability of Ca, Mg, Mn, Cu and Ni. Our results showed that Corg had positive effects on increase of availability of Mg, Cu and Ni, but on the other hand, it decreased availability of P, Fe and Zn. Application of biochar at rate of 20 t.ha-1 together with urea had statistically significant influence on increase of sunflower yield (by 37 %) in sandy soil. In loamy soil, the highest yield of green pepper (81.5 t.ha-1) was observed in B10+OH treatment.