What is More Suitable for Kohlrabi Fertilization – Digestate or Mineral Fertilizers

Abstract

In a one-year vegetation pot experiment, we compared the effect of digestate from a biogas station and mineral fertilisers on yield and quality parameters of kohlrabi, variety Moravia. Four treatments were used in the trial: 1) untreated control, 2) urea, 3) digestate, 4) urea, triple superphosphate, KCl, MgSO4. The N dose was the same in treatments 2–4, 1.5 g N/pot. In treatment 4 the P, K and Mg doses corresponded to those supplied in the digestate treatment (3). The weight of single kohlrabi bulbs in the unfertilised control was significantly lower (39.2%) than in the urea treatment (100%) and the other fertilised treatments. After application of digestate (treatment 3) and mineral fertilisers (treatment 4), the weight of single bulbs significantly increased by 18.6 and 25.2%, respectively, compared with the urea treatment (2). The content of ascorbic acid did not differ among the all four treatments (274–291 mg/kg). There were significant differences between all fertilised treatments (2, 3, 4) in bulb nitrate content (792, 327, 776 mg NO3−/kg fresh matter, respectively). The content of nitrates was the lowest in the unfertilised treatment – 135 mg NO3−/kg fresh matter. After digestate application the nitrate content decreased significantly, to 327 mg NO3−/kg fresh matter. We recommend the use of digestate to kohlrabi as it results in comparable or better yield and qualitative parameters of kohlrabi compared with mineral fertilizers.

Keywords

• digestate
• urea
• mineral fertilisers
• kohlrabi
• yields
• ascorbic acid