Sewage sludge as an alternative to organic-mineral fertilizers in buckwheat cultivation

Abstract

The study aims to justify the feasibility and effectiveness of using sewage sludge as an alternative organo-mineral fertilizer under conditions of a shortage of traditional organic fertilizers in buckwheat cultivation. The study was conducted during 2023–2025 under field conditions by investigating the effects of different application rates of sewage sludge on the growth, development, and productivity of buckwheat plants. The experiment was arranged as a two-factor field trial with three replications. During the growing season, phenological observations, weed infestation assessments, and soil moisture control were carried out. After crop maturity, biometric parameters of plants were measured, plot-based yield harvesting was performed, and the results were statistically analyzed using analysis of variance. Sewage sludge was found to have a high agrochemical potential and significantly exceeded soil in the content of available nitrogen, mobile phosphorus, and exchangeable potassium, while the concentrations of heavy metals did not exceed the maximum permissible levels. Meteorological conditions in 2023–2025 were characterized by considerable variability in temperature and moisture, which ensured an objective assessment of the fertilizer effect on buckwheat plants. Application of sewage sludge intensified growth processes, increased plant height, and enhanced the accumulation of aboveground dry matter in the cultivars Volia and Volodar. The highest and most stable grain yield (1.8–1.9 t/ha) was obtained at an application rate of 30 t/ha of sewage sludge. Increasing the rate to 60 t/ha resulted in excessive vegetative growth, lodging of crops, and a decrease in grain productivity despite an increase in total biomass. Sewage sludge is an effective source of organo-mineral nutrition for buckwheat plants. Its application at a rate of 30 t/ha provides optimal conditions for crop growth and development, promotes increased plant height and dry matter accumulation, and increases grain yield by 0.6–0.8 t/ha compared with the control. The use of higher rates (60 t/ha) is impractical due to the risk of excessive vegetative growth and reduced productivity. Therefore, 30 t/ha is the optimal and agroecologically justified application rate of sewage sludge for buckwheat cultivation.