Organic manures as sources of fertiliser sulphur

Summary in the original language of the document

On a global scale, S excretion from domestic animals may be estimated to around 8 million t per year, corresponding to 80% of the World S consumption for mineral fertiliser manufacture. The utilisation of this potential source of fertiliser-S is discussed focusing on the use of manure from housing and manure storages applied to agricultural land. Especially in the developed countries the S content of manure collected from cattle and pigs (1 million t S per year) has a potential as S-fertiliser, as legal demands on the utilisation of manure N and/or P already require the use of animal wastes as fertilisers. Content and composition of manure-S from both monogastrics and ruminants may be extremely variable, depending on the S content of the feed. If the diet has an S content balanced according to the animal requirement then the S content of the manure will be relatively low and the main part of S is expected to be in organic forms not available to plants. If the manure is stored under anaerobic conditions over a time span of months there is considerable risk of microbial transformations of sulphate into organic S and gaseous compounds that may be lost by volatilisation. In this situation the plant-availability in the year of application may be too low to be taken into account in fertiliser practice. A residual long-term effect of the organic S fraction must be expected. The ability of a cropping system to use mineralised S depends on the length of the growing season of the crops, but mineralisation is unlikely to fully meet the S-demand of a crop. There is a need for quantitative investigations of the relations between dietary S input, loss during storage and plant utilisation in the field.