Effect of Sulphur Fertilisation on Yield and Quality of White Mustard Seeds

RYANT, P.: Eff ect of sulphur fertilisation on yield and quality of white mustard seeds. Acta univ. agric. et silvic. Mendel. Brun., 2009, LVII, No. 2, pp. 95–104 The objective of the present study was to estimate the eff ect of diff erent forms of sulphur on yields and qualitative parameters of white mustard seeds. This topic was studied in 2004 in the form of a pot trial in a vegetation hall and linked up with an identical experiment with spring wheat conducted in 2003. Besides the control variant not fertilised with sulphur (1) we fertilised the soil with elemental sulphur (2), ammonium sulphate (3) and gypsum (4) and applied foliar dressing of elemental sulphur with bentonite (5). For all variants the nitrogen dose was 0.9 g per pot (0.15 g . kg−1 of soil) and for variants 2 to 4 it was 1 g of sulphur per pot (0.17 g. kg−1 of soil). Foliar dressing of elemental sulphur (S0) was not applied until the stage of six true leaves in a dose of 10 kg per ha (0.032 g per pot). Signifi cantly higher yields of white mustard seeds were achieved a er foliar application of S0 which can be also due to its fungicide action. The variants where gypsum was applied showed the highest average number of branches and pods and also straw yields. A er gypsum fertilisation or foliar application of S0 the oil content in the mustard seeds exceeded 25%; this is the minimal content required for the production of good quality mustard. The 1000-seed weight was signifi cantly higher a er foliar application of S0. The proportion of seeds greyish on the surface, a sign of mildew, signifi cantly decreased a er fertilisation with all forms of sulphur, but most of all a er foliar application of S0. Fertilisation with ammonium sulphate reduced the exchangeable soil reaction a er harvest. On the other hand gypsum alkalised the soil environment and increased the content of available calcium and water-soluble sulphur. The soil of the variant where foliar dressing of S0 was applied had a higher content of available calcium a er harvest. The least amount of available sulphur and phosphorus in the soil was seen a er foliar application of S0 signalising a more effi cient uptake of nutrients from the soil for the production of seed yields and for the quality of the seeds. white mustard, elemental sulphur, ammonium sulphate, gypsum, yields, quality In the past most of the demands of agricultural crops for sulphur had been covered by atmospheric depositions. However, in the experimental year 2004 these depositions in the Czech Republic were reduced to 12.1 % of the situation in 1990; in 2004 it was only 8.8 kg of S per ha (Hůnová et al., 2005). This rapid drop was the main reason why the use of sulphur-containing fertilisers has increased so much. On a worldwide scale and also in the Czech Republic the most frequently used fertiliser containing sulphur is ammonium sulphate with a 24 % content of S (Ceccotti et al., 1998). An important source of sulphur in the Czech Republic used to be single superphosphate, which contained 8–12 % of S, and which has now virtually disappeared from the market. Due to its high price also the once used potassium sulphate (18 % of S) is now applied only to a limited extent. On the other hand we see the comeback of gypsum (12–18 % of S), which had been recommended as early as the 19th century (Duchoň, 1948). Side by side with conventional mineral fertilisers containing sulphate ions also S0 – elemental sulphur (80–99 %) is gaining ground. It is an ideal slow-action fertiliser and is not water-soluble; before uptake and utilisation in the plant it has to be oxidised to watersoluble sulphate (Blair, 2002). During foliar application it is also oxidised by bacteria of the genus Thiobacillus on the leaf surface or inside the leaf by specifi c enzymes of chloroplasts (Jolivet, 1993). The condition for its wider use as a fertiliser is based on the re-