EFFECT OF SULFUR FERTILIZERS ON THE GRAIN-YIELD AND SULFUR-CONTENT OFCEREALS

In order to determine whether cereal crops require fertilizer sulphur (S) in areas estimated as receiving < 20 kg S/ha per year from the atm osphere, the effects of applying agricultural gypsum (10, 20, 30, 40, 60 and 80 kg S/ha), ammonium sulphate (24 and 48 kg S/ha) and foliar-a pplied elemental S (10 kg S/ha) fertilizers were compared with a nil-S control in replicated field experiments at 12 sites in England and Wa les during 1987-90. Averaged across all S treatments, significant (P l ess than or equal to 0.01) positive yield responses of 0.4 t/ha were o btained in winter barley at three sites in 1990 on sandy soils in Wale s (two sites) and in south-west England (one site). There was no yield advantage in applying > 10 kg/ha of S as gypsum at these sites. Yield responses were best predicted by a nitrogen:S concentration ratio gre ater than or equal to 17:1 in leaf tissue at anthesis and a S concentr ation of less than or equal to 0.1% in the grain dry matter at harvest . Significant increases in total S and sulphate-S concentrations in le af tissue at anthesis were obtained from increasing the rates of gypsu m applied at ten of the sites, but a significant increase in the conce ntration of S in the grain at harvest was obtained at only one site. T here was no difference in effectiveness between gypsum and foliar-appl ied elemental sulphur when compared at a single rate of 10 kg S/ha. Co mparison of the increases in leaf-S status from maximum application ra tes of ammonium sulphate and gypsum suggested that ammonium sulphate w as the more effective S-fertilizer source. The results confirm that S deficiency is starting to appear in cereal crops in England and Wales.