Biodynamic preparations influence the biochemical soil properties and the quality of potatoes

Summary
The soil samples were analysed for available phosphorus, available potassium, ammonium nitrogen, nitrogen (sum of nitrate and nitrite), and mineral nitrogen.

• Phosphorus, potassium, and nitrogen are primary macronutrients. Their availability in the soil is particularly important for healthy plant development.

The potato samples were analysed for total phenolic compounds, total anthocyanin content, and free radical activity.

• Phenols are a variety of chemical compounds. In plant cultivation, they often occur as flavouring substances and determine the smell and taste of vegetables and fruits.
• Anthocyanins are plant pigments that, depending on their concentration, lead to a red, violet or blue colour. Anthocyanins also belong to the group of antioxidants.
• The activity against free radicals is a biological defence mechanism against cell damage. Important substances for this defence are, for example, antioxidants.

The highest concentrations of phosphorus, potassium, nitrogen and mineral nitrogen available in the soil throughout the growing season were detected on the 14th day after the soil application of preparation BD 500 (before planting the potatoes). In addition, spray application of preparation BD 500 onto the soil resulted in higher enzyme activity. When preparation BD 501 was applied, the content of total phenolic compounds in the tubers of Blue Congo and Red Emmalie was significantly higher than in plants which were not treated with BD 501, at 20.1% and 5.4% respectively; the content of anthocyanins was significantly higher in the tubers of all three tested varieties. However, the application of preparation BD 501 did not influence the content of total phenolic compounds and the antioxidant activity of the Vitelotte tubers. When both biodynamic preparations (500+501) were applied, significant effects were only measured in the accumulation of anthocyanins in the tubers of Blue Congo and Vitelotte. The application of the BD 500 preparation alone significantly reduced the anthocyanin content in the tubers of the cultivars Red Emmalie and Vitelotte.

Figure 1: Overview of the measured values of total phenolic compounds, anthocyanins and free radical activity for the control group ("Not sprayed") and for the applications of P 500 and P 501. P 500 was applied to the soil and P 501 to the plants.