Evaluation of the Potassium Status of Arable Soils in Ukraine on the Basis of Modern Soil Diagnostic Techniques and Development of Recommendations for the Rational and Efficient Application of Potassium Fertilizers.

The project aims to provide an accurate assessment of K status of arable soils, determine the demand for K fertilizers, establish the efficiency of K fertilizers in the soils of the main soil-climatic zones, and work out fertilizer recommendations for maize, wheat, and sugar beet grown on Chernozems.

In 2012, the agronomy efficiencies of K fertilizers for winter wheat, grain maize, and sugar beet by climatic zone and soil type have been estimated from the database containing information on crop response to K fertilizer applications. This database has been compiled through field trials conducted in Ukraine by State Agrochemical Service stations and geographic data network experiments during the last 40 years. The major factors determined to affect the efficiency of K fertilizers in different climatic zones of Ukraine are the level of precipitation and temperature during growing season, as well as soil K content. The mathematical equations showing relations between soil K levels and agronomic efficiency of K fertilizer, as well as between hydrothermal coefficient (the ratio of the sum of precipitation during the year to the sum of active temperature during the grown season) and agronomic efficiency of K fertilizer for winter wheat, grain maize, and sugar beet have been not yet been determined.

In 2011, a field experiment to determine K fertilizer requirements of a forage maize-wheat-sugar beet crop rotation commonly found in the steep-forest zone of Ukraine, was established. The efficiency of four different K fertilizer rates (varying between 30 and 120 kg of K₂O/ha) with two combinations of NP was studied. Results obtained showed a high efficiency and economic expediency of applying K fertilizers to forage maize. The optimization of N and P supply contributes to the increase in the return on K fertilizers. The highest economic effect was obtained when 90 kg N, 90 kg P and 40 kg K/ha were used. The local application of K fertilizers (before pre-plant cultivation) significantly increased the yield of maize green mass by 14 to 18%. Due to adverse weather conditions during the whole growing season of 2012 (strong winter frost without snow cover followed by summer drought), the yield of summer wheat was lower than expected (varying from 1.7 to 2.4 t/ha). During summer drought, K fertilizers contributed up to 10% of yield increase in plots with optimized NP. Ukraine-01