REDUCING WATER AND MINERAL FERTILIZER CONSUMPTION IN VEGETABLE GROWING UNDER WATER SCARCITY CONDITIONS: POSSIBILITIES OF ORGANOMINERAL MELIORANT

Abstract

This thesis analyzes the possibilities of an organomineral meliorant based on local raw materials and describes the experimental methodology for reducing water and mineral fertilizer consumption in vegetable cultivation on irrigated soils of the Surkhandarya region under conditions of climate change and water scarcity. The main part of Uzbekistan's water resources comes from neighboring territories, with agriculture consuming approximately 90% of the annual water use. Due to climate change, water scarcity in the country could reach 7–15 billion m³ by 2030. Only 30% of irrigated lands utilize water-saving technologies. In hot regions like Surkhandarya, evaporation is intense, leading to rapid moisture loss from the soil, and nitrogen fertilizer uptake by crops is low. Therefore, there is a high demand for affordable, local raw material-based solutions that can simultaneously reduce water and fertilizer consumption. The study considers an organomineral meliorant consisting of bentonite, phosphorite flour, and humic substances as a means to increase the soil's water retention and sorption capacity. Bentonite retains water and cations due to its high cation exchange capacity; humic substances improve soil structure and can aid phosphorus uptake from phosphorite flour by forming complexes with phosphates. The working hypothesis is that the meliorant will retain moisture longer in the soil, slowly release nutrients, and maintain tomato and cucumber yields even when irrigation water and NPK rates are reduced. A field experiment will be conducted in four variants with four replications: control (without meliorant, 100% NPK); meliorant 300 kg/ha + 75% NPK; meliorant 500 kg/ha + 75% NPK; meliorant 700 kg/ha + 50% NPK. This research aims to determine optimal meliorant norms for Surkhandarya conditions and the potential for saving irrigation water and mineral fertilizers, forming the basis for developing agrotechnical recommendations for farmers.