Ecological Assessment of Cotton Cultivation in the Kura-Aras Lowland

This study investigated the impact of the intensive use of mineral fertilizers in cotton production in the Kura-Aras Lowland of Azerbaijan on the environment. The study focused on the risks associated with the long-term use of nitrogen and phosphorus fertilizers and their impact on soil and water resources. The main aim was the assessment of the environmental impact of these fertilizers by analyzing chemical transport mechanisms, while taking into account the specific agricultural conditions of the study area. To achieve that aim, both field and laboratory experiments were conducted. Soil samples were taken at mid-elevation plots, nitrogen and phosphorus transport rates were determined, and spectrophotometry, colorimetry, and electrochemical analysis methods were used. The studied soil was characterized by low humus content (1.2-1.8%), slightly alkaline pH (7.8-8.3), and overirrigation. Together, these factors significantly alter the storage, transport, and transfer of nutrients, as well as their environmental impacts. The results indicate that the efficiency of mineral fertilizer use in the study area has been decreasing. The use of nitrogen fertilizers at a rate of 180-200 kg/ha leads to a nitrogen deficit of about 90 kg/ha. This means that about 50% of the added nitrogen is not absorbed by plants but instead remains as a mobile compound in the agroecosystem. Most of this excess nitrogen leaks into groundwater, and some of it is also released into the atmosphere. The use of phosphate fertilizers also leads to a nitrogen deficit of about 65 kg/ha in the environment. Over a decade of cultivation, this leads to the accumulation of approximately 650 kg/ha of unavailable phosphate compounds in the soil profile. The data obtained indicate a high risk of groundwater pollution, secondary soil salinization, eutrophication of water bodies, and the accumulation of heavy metals introduced with phosphorus fertilizers. Thus, the study results indicate that current approaches to fertilizer application in cotton production exceed the ecologically acceptable load level for the soil and climatic conditions of the Kura-Aras Lowland and require a transition to more precise and adapted plant nutrition management systems.