Effect of fertilizers on biomass and productivity of amaranth on sierozem-meadow soils of the Zeravshan valley of Uzbekistan

The article presents data on the effects of individual and combined applications of mineral (NPK) and organic fertilizers on the biomass of roots, stubble residues, aboveground plant parts and grain yield of amaranth cultivated in sierozem-meadow soils of the Zeravshan Valley, Uzbekistan. The field experiments followed a two-phase design. First, the impact of different nitrogen fertilizer doses (N150-300) (combined with phosphorus and potassium fertilizers-P150K200) was evaluated. Second, the study examined the effects of separate versus joint applications of chemical and organic fertilizers on amaranth productivity. The application of nitrogen fertilizers against a background of phosphorus and potassium, as well as the combined use of mineral and organic fertilizers, significantly increased the mass of root and stubble residues, aboveground biomass and grain yield in amaranth plants. These findings indicate a deficiency of mobile nutrients in the soil, which limits optimal amaranth growth. Therefore, when applying nitrogen fertilizers against the background of P150K200, complete mineral fertilizers (NPK), 30 t/ha of cattle manure and combined use of 30 t/ha of manure with different NPK rates, the yield of grain and biomass of the aboveground and underground parts of amaranth increases significantly. For example, nitrogen fertilizers at rates from 150 kg/ha to 300 kg/ha against the background of P150K200 increased the amaranth yield by 4.26-27.04 c/ha or by 46.46-94.87 c/ha. The application of complete mineral fertilizers (NPK) compared to the control without fertilizers - by 8.87-20.14 c/ha or 50.06-113.66 %, 30 t/ha of cattle manure - 14.01 c/ha or 79.06 %. The combined application of 30 t/ha of manure with different rates of mineral fertilizers increased the amaranth grain yield by 16.56-20.65 c/ha or 93.45-116.53 %. However, when the rate of nitrogen fertilizers increased from 250 kg/ha to 300 kg/ha, the amaranth yield did not increase significantly. The same pattern was observed when the rate of mineral fertilizers increased from N250P175K125 to N300P210K150. Increasing the rate of mineral fertilizers against the background of 30 t/ha of manure from N100P70K50 to N150P105K75 and to N200P140K100 did not have a significant effect on the amaranth yield. However, there was a significant difference in the amaranth yield between the N100P70K50+30 t/ha of manure and N200P140K100+30 t/ha of manure variants. The best results were obtained in the variants where 30 t/ha of manure+N200P140K100 and 250 kg/ha of nitrogen were added against the background of phosphorus and potassium fertilizers (P150K200). Thus, mineral and organic fertilizers improve the nutrition, growth and development of amaranth plants and significantly increase the biomass and grain yield of amaranth in the conditions of sierozem -meadow soils of the Zeravshan valley.

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