Agrochemical use of waste elemental sulphur in growing white mustard

In a one-year pot experiment the effect of waste elementary sulphur on the following parameters was observed: 1. on the chemical composition of mustard plants during the growing season, 2. on the yield of seeds, straw and oil, 3. on the chemical composition of seeds and 4. on the content of the water-soluble sulphur in the soil after the harvest. Elemental sulphur was obtained as a waste material of petroleum refining and was incorporated into a 15-15-15 NPK fertiliser where it comprised 4%. The experiment had the following variants: 1) control (unfertilised); 2) NPK 1; 3) NPK 2; 4) NPKS 1; 5) NPKS 2. The smaller dose amounted to 3.3 g, the higher one to 6.7 g of the fertiliser per pot (6 kg of soil). Moreover all variants were performed in 2 different soils - a medium soil with neutral pH value and a heavy one with alkali pH value. At the stage of 6 true leaves, the content of nitrogen in plants increased in accordance with its dose. Simultaneously, sulphur applied in the NPKS fertiliser improved nitrogen utilization. The difference between the variants fertilised with NPK and the variants with NPKS amounted to 38.9% in the neutral medium soil, whereas in the alkali heavy soil it was as low as 1.4%. The yield of both seed and straw in the fertilised variants was statistically significantly higher than in the unfertilised control variant. However, there were observed no statistically significant differences between the variants with sulphur and the variants without sulphur although both the yield of the seed and straw in the variants with NPKS was higher than in the variants with NPK. The application of elemental sulphur into the neutral medium soil increased the concentration of both nitrogen and sulphur in the mustard seed in comparison with the variants fertilised with NPK only. The difference between them comprises 1.8% and 9.0% in variants with the small and high dose, respectively. In the heavy soil, the trend was opposite. The application of sulphur into both soils resulted in the increase of the oil content in comparison with the NPK variants. Sulphur addition to NPK had a positive impact on the augmentation of the available sulphur content in the soil which can positively affect, particularly the following crops. Still, a drop in the pH value was not confirmed.