Organic nutrients impact on the productivity of carrots (Daucus sativus Röhl.) and onions (Allium cepa L.)

Researchers worldwide are looking for ways to ensure crop productivity and soil sustainability and avoid negative impacts on the environment and human health. Organic horticulture needs biologically active substances that increase germination and plant growth processes and improve product quality. Investigation of organic soil supplements and their effect on the growth and quality of organically grown carrot and onion was carried out at the Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry in 2020-2021 in a Calcic Endogleyic Luvisol (LV-gl-n-mL) light loam with medium humus. Two types of biologically active substances were tested: substrate of organic origin that was applied into the soil before sowing, and liquid organic extract that was applied through an irrigation system immediately after sowing and when the plants reached the 3-5 leaf stage. The effect of bioactive nutrients was tested on two genetically different carrot cultivars ‘Garduolės’ and ‘Rodelika’, and onion cultivars ‘Babtų didieji’ and ‘Rawska’. The total yield of carrots during the experimental years varied from 47.14 to 58.62 t ha^‑1 and the marketable yield from 85.5 to 94.0%, respectively. The total yield of onions varied from 32.37 to 36.0 t ha^‑1 and the marketable yield from 82.3 to 90.6%. The obtained results showed that bioactive organic nutrients significantly increased tested vegetables’ total sugar and soluble dry matter. The study established that carrot cultivar ‘Garduolės’ and onion cultivar ‘Babtų didieji’ are more resistant to biotic and abiotic factors. Bioactive organic nutrients increased the amount of humus and the content of potassium and calcium in the soil.