A review of research on the molybdenum requirements of New Zealand pastures

ABSTRACT

The requirement for molybdenum (Mo) for legume and pasture growth on New Zealand soils was first identified in the 1950s and most of the research was carried out up to the 1980s. This resulted in a recommendation to apply 56–70 g/ha of sodium molybdate every 4–5 years that was later modified to 50 g/ha every five years. On most soils, the availability of Mo increased with soil pH but the rates of lime required were uneconomic on hill country pastures so Mo was applied as the most cost-effective option. Measuring available soil Mo was a poor predictor of pasture yield responses to Mo compared with the Mo content of clover. More recent research showed that the Mo content of clover had to be less than 0.1 ppm and nitrogen (N) content less than about 4.5% for a definite response in yield to applied Mo to occur. High natural levels of soil Mo elevating pasture Mo content above 0.5–1 ppm or overuse of fertiliser Mo where pasture copper (Cu) is low (<5 ppm for sheep, <10 ppm for cattle and deer) can cause less Cu to be adsorbed from the rumen and reduce animal growth.

KEYWORDS:

• Copper
• clover
• molybdenum
• nitrogen
• pasture yield response

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The writing of this review was funded by the Fertiliser Association of New Zealand.