Prospects of Using Seaweed as a Fertilizer for the Development of Organic Farming

The effect of fertilizers from seaweed belonging to different departments (Phaeophyta, Rhodophyta) on the growth and chemical composition of agricultural crops was evaluated. The objects of the study are commercial seaweed Saccharina japonica and Anthelzia tobuchinskaya and fertilizers obtained from them. For application to the soil, dried algae were crushed to a particle size of 1–5 mm, for extracts – to a particle size of 1–5 cm. The extracts were obtained in an aqueous medium with a temperature of 25°C, with an algae : water ratio (1 : 10)–(1 : 15), duration of 16 hours with stirring every hour. Liquid fertilizers were used as root top dressing in the form of irrigation or as foliar top dressing in the form of spraying plants. It was found that fertilizers from Anthelzia tobuchinskaya contributed to an increase in the height of Moscow greenhouse lettuce plants by 39.1–68.5%, fertilizers from saccharina japonica– by 27.4–52.8%. In addition, the number of leaves in the experimental group of plants increased by 3.6–19.7% compared with the control group. The yield of lettuce using algae fertilizers varied from 1.54 to 1.90 kg/m2 compared with the control (1.37 kg/m2). Root fertilization with liquid fertilizers from algae provided a maximum yield increase of 36.7–38.8% relative to the control. The chemical composition of lettuce plants also changed under the influence of algae fertilizers. The content of nitrogen, iodine, magnesium, and easily hydrolyzable carbohydrates in the leaves of all experimental plants increased relative to the control.