Potassium the key to clover growth

Some people spend their lives searching for a four-leaf clover. Jeff Morton has a more pragmatic approach to the legume, having dedicated considerable time to researching how to increase clover growth on hill country soil.

Clover is renowned for its nitrogen-fixing properties, and provides a nutritional boost to grazing animals. Four-leafed or not, clover is the jackpot for growing healthy grazing livestock.

In the study, a team of researchers applied potassium fertiliser to five hill country trial sites in the Hawkes Bay with low levels of potassium in the soil. By applying varying amounts to each site they were able to gauge the effects on total pasture production. Jeff pulled the results together in a research report, which has been published in the New Zealand Journal of Agricultural Research.

“We were able to increase the amount of clover we grew by applying potassium,” says Jeff. “The more potassium we applied the more clover we grew.

“What was surprising was that this didn’t result in more total pasture production – we grew more clover but not more grass. Whereas when we didn’t apply any potassium it resulted in more grass growing.”

Most hill soils in New Zealand have adequate potassium levels, Jeff explains. “Sheep most commonly graze hill country pastures and sheep are more efficient at cycling potassium than cattle. The potassium is still there because the soils haven’t been weathered and there’s a lot of potassium that’s yet to be used in the soil.”

Adding potassium to the soil won’t always result in more clover. “You need to have reasonable rainfall to grow clover. If you haven’t got clover in your hill country soil, mainly because it’s too dry, you won’t get any payback by applying potassium.”

The method works best on soil that contains low levels of potassium, with a reasonable amount of existing clover.

The report ‘Potassium requirements of pastures on North Island east coast hill country in New Zealand’ is available at www.tandfonline.com.