Evaluation of sulphur status of East Coast pastures of the North Island, New Zealand 1. Soil and herbage survey

Abstract

Two sampling surveys for soil and herbage, the ftrst in autumn and the second in the following spring, were carried out in the East Coast area of the North Island to investigate the relationship between levels of soil and herbage sulphur (S). Levels of phosphate-extractable soil S generally decreased with depth down the proftle to 30 cm and the majority of this soil S was also extracted by 0.01 M CaCl₂ indicating that adsorbed S is not a major component of phosphate-extractable S in the soils examined. The amounts of adsorbed S were related to the phosphate retention capacity, although there was little accumulation of sulphate in soils with phosphate retention capacities of less than 70%. Total S levels and N:S ratios in herbage were related to levels of phosphate-extractable soil S, with 13 μg S/g of soil appearing to be the critical value. Above this value, all herbage samples appeared to have adequate S status. Below this value, there was a wide range in herbage S status from adequate to deficient.

Keywords:

• sulphur
• fertilisers
• soils
• herbage
• survey