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.

In 2011, a three-year project was established in Ukraine with objectives to: a) provide an accurate assessment of K status of arable soils, b) determine the demand for K fertilizers, c) establish the efficiency of K fertilizers in the soils of the main soil-climatic zones, and d) work out fertilizer recommendations for maize, wheat and sugarbeet grown on chernozems based on data obtained by improved methods for a K soil test. Project activities included: a) field experiments on K fertilization for target crops, b) evaluation of soil K status through summarization of database on Ukrainian soil properties and last soil survey, and c) systematic generalization of the data obtained in long-term trails.

Statistical processing of the database on agrochemical certification of agricultural lands and the results of field experiments yielded regression equations for changes in soil K status parameters in different climatic zones of Ukraine. According to the prognosis developed, the average weighted content of plant-available K forms in most Ukrainian soils will remain almost on the natural level corresponding to the average K supply (no more than 8 to 9 mg/100 g of soil) up to 2020.

The results of trials with maize grown for silage showed a high agronomic and economic efficiency of applying K fertilizers to chernozems. The optimization of N and P supply contributes to an increase in the return of K fertilizers on chernozems. A mathematical model was developed for the relationship between the yield of maize green mass and the application rates and proportions of K and NP fertilizers. The highest economic effect was received at the application rate of 90-90-40 N-P₂O₅-K₂O. Similarly, the results of trials with sugar beet showed that the banded application of K fertilizers gave the highest effect on the yield of tubers and the yield of sugar per ha under drought conditions of 2011 while the optimum application rate was 120-120-120 N-P₂O₅-K₂O.

The comparison of the values for the content of plant-available K obtained by different methods showed that the Chirikov method (extraction with 0.5 M acetic acid [CH₃COOH]) recommended and used for routine K soil test in Russia, Ukraine, and Kazakhstan usually overestimates K supply of fine-textured chernozems. Ukraine-01