Sulphur Availability from Organic Materials Applied to Winter Wheat

Keywords: Sulphur, fertiliser, organic materials, manure, biosolids, wheat.

The aim of this research was to quantify sulphur (S) supply from organic materials to winter wheat crops, in order to improve current recommendations on the use of farm manures and biosolids as sources of available S for arable crops.

Analysis of databases of organic material S contents found good agreement with the ‘typical’ values given in the UK Defra Fertiliser Manual (RB209) for livestock manures and most biosolids types; however, for digested cake and composted biosolids, the mean total SO₃ content was higher than the ‘typical’ values. The S content of organic materials (both total and ‘extractable’ SO₃) was variable; hence, analysis of a representative sample is advisable to ensure that crops grown on potentially deficient sites receive adequate S.

Field experiments were carried out at 3 sites cropped with winter wheat over 2 harvest years at each site. There were 7 organic material treatments comprising autumn applied cattle farmyard manure (FYM), pig FYM, broiler litter and two biosolids products, and spring applied broiler litter and pig/cattle slurry. Inorganic (water soluble) fertiliser S response treatments (0 – 75 kg/ha SO₃) were established to determine the fertiliser S replacement values and hence S availability of the applied organic materials. There was a response to S in 3 of the 6 site/years. For the spring applied organic materials, ‘extractable’ SO₃ (i.e. readily available SO₃) was a good indicator of crop available S, ranging from c.15% of total SO₃ for cattle FYM to c.60% of total SO₃ for broiler litter. Results showed that for spring applied organic materials, ‘extractable’ SO₃ was equivalent to inorganic fertiliser S i.e. the S use efficiency for spring applications was 15% of total SO₃ for cattle FYM, 25% for pig FYM, 60% for broiler litter, 35% for slurry and 20% for biosolids. Lower S use efficiencies were measured from the autumn applied organic materials i.e. 5—10% of total SO₃ for livestock manures and 10—20% of total SO₃ for biosolids, because readily available S was lost via overwinter leaching.

This work has led to a better understanding of the crop available S supply from organic materials. Guidance for farmers on S availability from organic materials is likely to improve farm profitability by ensuring that crops receive adequate amounts of S.

Lizzie Sagoo¹, Ken A Smith², Fiona A Nicholson³ and Steve P McGrath⁴

¹ ADAS Boxworth, Battlegate Road, Boxworth, Cambridgeshire, CB23 4NN, UK.

² ADAS Gleadthorpe, Meden Vale, Mansfield, Nottinghamshire, NG20 9PD, UK.

³ ADAS Wolverhampton, Pendeford House, Pendeford Business Park, Wobaston Road, Wolverhampton, WV9 5AP, UK.

⁴ Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK.

26 pages, 8 figures, 8 tables, 22 references.