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, MgSO 4. 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 signifi cantly 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 diff er among the all four treatments (274-291 mg/kg). There were signifi cant diff erences between all fertilised treatments (2, 3, 4) in bulb nitrate content (792, 327, 776 mg NO 3 -/kg fresh matter, respectively). The content of nitrates was the lowest in the unfertilised treatment - 135 mg NO 3 -/kg fresh matter. After digestate application the nitrate content decreased signifi cantly, to 327 mg NO 3 -/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.