Efficiency of mineral fertilizers for growing Althaea officinalis L. under conditions of irrigation

In the Forest-Steppe Zone of Ukraine, a study was carried out to establish the effect of mineral fertilizers and drip irrigation on the yield of dry raw material. It was found that irrigation significantly increases productivity of althaea, by eliminating the deficit of soil moisture in critical periods of growth and development. The yield increase caused by the use of drip irrigation in the first year of vegetation of the crop was 1.27–1.98 t/ha for dry grass, for leaves — 0.69–1.17 t/ha, for roots 0.22–0.39 t/ha. For the second growing season, the yield increase was: 1.52–4.7 t/ha for grass, 0.46–1.35 t/ha for leaves and 1.5–2.76 t/ha for roots. It was also found that increase of the mineral fertilizers main application dose caused increase of the yield. The highest yield of dry raw material of the culture was obtained in both the first and second years of the growing season with the introduction of N180P180K180. With the application of mineral fertilizer at a dose of N180P180K180 under conditions of drip irrigation, the yield of dried althaea grass was 8.09 t/ha, leaves — 3.88 t/ha, roots — 3.08 t/ha, which exceeded the option without fertilizers and without irrigation by 4.08 t/ha for grass, 2.04 t/ha for leaves, 1.44 t/ha for roots. The highest yield was obtained in the second year of vegetation using the variant with the application of the highest dose of mineral fertilizers under drip irrigation, where the yield of dry grass was 15.78 t/ha, leaves — 4.42 t/ha, roots — 6.24 t/ha. On the plantation of the second year of vegetation in the variant without irrigation and without fertilizers, the yield of raw materials was the lowest. It was 6.85 t/ha for grass, 1.88 t/ha for leaves and 2.12 t/ha for roots.