Effect of nitrogen fertilization on yield of grapes and fertilization efficiency in Gissar Valley of the Republic of Tajikistan

The issue of optimizing plant fertilization is important in quality systems, such as Integrated Plant Production, GLOBAL G.A.P., or SAI. Effective implementation of these systems depends on the use of a plant nutrition technology based on plants’ nutrient demand. In developing countries, low efficiency production technologies are used very frequently, and a significant level of anthropogenic pressure is therefore observable. The objective of this research was to assess grapevine fertilization efficiency according to particular nitrogen fertilization strategies. Within the scope of the research, a two-factor field experiment was conducted in a commercial vineyard located in Gissar Valley, the Republic of Tajikistan, in 2018. The experiment was established on sandy soils and involved the following factors: the overall quantity of mineral nitrogen used, and the number of fertilizer application cycles (one or three). The designed systems were assessed on the basis of commercial yield, productivity ratio, agronomic efficiency ratio, removal efficiency ratio, and physiological efficiency ratio. The findings obtained from the field experiment indicate that the plant yield was the highest, at 24.85 Mg ha-1, in the conventionally fertilized object, with the nitrogen dosage of 250 kg N ha-1. Similar yield was obtained when the amount of nitrogen was divided into 3 doses. In this variant, the values of ratios representing fertilization efficiency, such as the agronomic efficiency ratio, removal ratio and productivity ratio, were the most beneficial as well. No significant variations were determined in respect of the physiological efficiency ratio value, which may be an indication that no factors occurred in any of the variants which would distort the plants’ growth and development. Optimizing fertilization is an important aspect that defines the quality and safety of products of agricultural origin, especially in developing countries.