Možnosti využití metody Mehlich III k posouzení obsahu přístupné síry v půdě

The aim of this paper was to evaluate if accessible sulphur analyses in soil are relevant for Agrochemical Soil Testing (AZZP). This issue was assessed in the years 2014/2015. Samples to be taken in 2015 were selected according to results on sulphur analyses in Mehlich III extraction agent in 2014. It means that the first sampling was carried on in the autumn 2014 and second in the spring 2015. Plans were sampled together with soil in 2015. Seven regions were included in the sampling scheme (Brno, Planá (České Budějovice), Plzeň, Opava, Havlíčkův Brod, Liberec and Prague) and plots with winter wheat and winter rape were sampled. Majority (78 %) of soils samples measured on accessible sulphur content falls into the range 10,1 - 20,0 mg.kg-1. Average contents of accessible sulphur in soils in the autumn and spring were almost identical and there are no statistical differences amongst regions. Influence of fertilising on sulphur content in soils was not confirmed, however, sulphur fertilization positively influences the sulphur content both in rape and wheat plants. The content of accessible sulphur in soils in the spring positively correlates with sulphur content in rape. Based on current nutrient normative, 59 % of wheat plants are below the value when yield decrease may occur. In the case of rape it is more than 90 % of plants (samples). It does not seem to be suitable to include accessible sulphur measurement in soils into the AZZP system. The six-year cycle of AZZP is rather too long if soil sulphur mobility and dynamics is taken into account