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Abstract
An irrigated second harvest white clover seed crop (growing on a soil with New Zealand Ministry of Agriculture and Fisheries Quick Test values of sulphate sulphur 2 and Olsen phosphorus 6) was topdressed with sulphur at 20 kg/ha, either as gypsum (110 kg/ha) or as normal superphosphate (200 kg/ha). Total dry matter production from closing (mid November) to harvest (mid February) was 30% higher for fertilised than for control treatments (4980 v. 3800 kg/ha), with a 60% advantage to fertilised treatments for seed yield (500 v. 310 kg/ha). Seed yield for control compared with fertilised treatments contained a higher percentage of ‘seconds’ (14 v. 6%) and a lower 1000-seed weight (0.66 v. 0.71 g). All responses were to sulphur alone. Foliar chemical analyses suggested that even higher sulphur application rates may have been needed to further increase seed yield, particularly in relation to phosphorus utilisation.