The effect of sulphur and growth regulators on growth characteristics and grain yield of spring sown wheat

During the year 1999, two field experiments (Experiments 1 and 2) were conducted at the University of Wales Aberystwyth U.K., to investigate the effects of soil and foliar applied sulphur (S) in wheat, in terms of its potential as a growth regulator and to compare the effects with that of commercial growth regulators, chlormequat (CC) and gibberellic acid (GA3). Foliar S (Thiovit 80% S) was applied to the spring wheat variety Axona at Zadoks growth stage (GS) 23 (tillering) in experiment 1, and at GS 30 and 32 (stem extension) in experiment 2. Treatments applied at GS 23 were: untreated control, micronized sulphur (Thiovit, 80% sulphur) at 10 kg/ha and 20 kg/ha, chlormequat (CC) at 2.5 L/ha and gibberellic acid (GA3) at 75 g/ha. Treatments applied in experiment 2 at GS 30 and 32 were similar apart from GA3, which was not included. In experiment 1 (applications at GS 23), grain yield was unaffected by the treatments applied, although both S and CC appeared to increase the number of ears at maturity. The internode lengths and the main stem-lengths were not affected with S application. In contrast, CC applications reduced all but the basal internode lengths, while GA3 application increased internode lengths and overall stem length. In experiment 2 (applications at GS 30 and 32), the grain yield was again unaffected by S or CC. However, the stem length was reduced and the unit stem weight was increased following the application of S, though not to the same magnitude as with CC, and S at 20 kg/ha was more effective than S at 10 kg/ha. It was concluded that S, when applied at tillering (GS 23) in spring wheat, did not show potential as a growth regulator. However, when applied at the beginning of stem extension (GS 30 and 32), it did show potential to reduce the stem length and thereby increase the crops resistance to lodging. This is of particular relevance for use in low input, sustainable, and organic wheat production systems where the use of artificial plant growth regulators is discouraged or forbidden. Here, the use of foliar applied S as a potential stem shortener, coupled with its recognized fungicidal properties, make it an attractive and acceptable input.