Field experiments were conducted to predict optimum tissue sulphur (S) concentration, nitrogen:sulphur (N:S) ratio in leaf tissue and S levels for maximum grain yields of soybean cultivar PK‐327. Various S levels significantly increased the S and N contents in 50‐day‐old plants, straw and soybean grains. Test weight of soybean grains was also increased. N:S ratio wider that 16.0 in soybean leaves of 50‐day‐old plants was considered to indicate S starvation. Leaf N:S ratio of 10.83 produced maximum soybean grain yield. Among ammonium sulphate, superphosphate, and elemental S tried as a source of S, ammonium sulphate was found to be the best source of S for soybean. It is recommended that soil testing programmes should include testing for S status so that only optimum levels of S are applied as higher levels of applied S appear to be luxuriantly consumed.