Use of an unsorted pasture sample in herbage testing for sulphur, phosphorus, and nitrogen

Abstract

The nutrient status of grazed pasture is often assessed by a herbage test. Of the macro‐nutrients (sulphur (S), phosphorus (P), and nitrogen (N)) influenced directly by fertiliser inputs, most interest is generally taken in S as the soil test for this nutrient is of limited usefulness. It is often argued that more useful information is obtained from dissecting out and restricting analysis to the legume component of a pasture sample. To investigate whether this practice is necessary, legume and unsorted pasture samples were collected from sites covering a range of soil fertilities, slopes, and aspects during spring, summer, autumn, and winter, and analysed for S, P, and N. There was a strong correlation (r = 0.81,0.92, and 0.89 for S, P, and N, respectively) between legume and unsorted pasture samples suggesting that an unsorted pasture sample would provide similar information concerning the nutrient status of the pasture to a legume sample. The strong correlation between the nutrient concentration of the legume component and pasture samples, and the fact that the relationship is approximately unitary for S and P implies that the critical levels developed for legume samples could also be applied to an unsorted pasture sample.

Keywords:

• herbage test
• pasture sampling
• legume component
• sulphur
• phosphorus
• nitrogen