Barley response to the soil reserve of sulphur and ammonium sulphate in short-term experiments under controlled conditions of cultivation

The objective of the paper was to determine an appropriate concentration of available sulphur in soil for the initial growth of plants. Based on previous researches two methods of soil extraction were used to acquire information on the soil reserve: water extraction (H2O 1:5, w/v) and extraction in 0.5M ammonium acetate with addition of NH4F (KVK-UF soil test). Spring barley was used as a test crop to determine the soil reserve of sulphur and its response to sulphur addition to the soil. A collection of 48 samples of topsoil from agriculturally important localities in the CR was made up for this purpose and the parameters of the nutrient status of the soil were remarkably different. A set of soils was used to establish short-time vegetation experiments in a plant growth chamber according to the scheme: A) control - without sulphur application and B) response variant with application of 30 mg S/kg of soil in the form of (NH)4SO4; nitrogen in variant A was adjusted by application of NH4Cl. Index of nutrient efficiency (IE = Y/N where Y = yield and N = nutrient concentration in the plant) and boundary lines of the point field were used to evaluate the efficiency of barley nutrition with sulphur. The efficient soil reserve of sulphur for the soil test H2O (1:5) when the ICP analytical technique was used was indicated in the range of 8-11 mg S/kg; 6-10 mg S/kg for sulphate detection on a SKALAR analyser. The efficient utilisation of sulphur by barley plants for the KVK-UF soil test was in the range of 7-12 mg S/kg. The conversion of the KVK-UF S-test to the index of soil reserve of sulphur by adding up a variable portion of the CEC value to the value of sulphur determined by the soil test (0.0167CEC + 9.1667) improved the closeness of the relationship between soil and plant.