George Herald | How to establish clovers successfully in an existing kikuyu sward

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How to establish clovers successfully in an existing kikuyu sward
13:06 (GMT+2), Thu, 28 June 2012

The successful establishment of clovers is the first step in ensuring a sustainable legume component.

AGRI NEWS - Perennial legumes, such as white clover, hold the potential to fix nitrogen, decrease the reliance on expensive nitrogen fertilisation and provide high quality feed for livestock. The recent increases in input costs associated with grass only systems based on kikuyu can potentially be alleviated by the inclusion of such legumes.

Most no-till establishment methods used to over-sow ryegrass into kikuyu are, however, not well suited for clovers. These methods do not meet the requirements of clovers for a well prepared seedbed and shallow placement, while pest and disease loads under no-till systems are often higher than under conditions where the area is cultivated.

Another major challenge is the competition for light, water and nutrients caused by companion grasses, in this case kikuyu and ryegrass (when established in mixtures).

Certain management practices can, however be employed to improve establishment success when over-sowing kikuyu with clovers:

By over-sowing clovers when soil temperatures are approximately 18oC (usually around April in the George area), temperatures are high enough to stimulate clover growth, but low enough to suppress kikuyu growth.

The negative impact of pests and diseases can be controlled by treatment of seed with a fungicide and herbicide, or alternatively by planting during periods when pest and disease load is lower (once temperatures have dropped).

The ideal is to establish clover into kikuyu that had been planted to annual ryegrass during February/March for the previous two years, since the early mulching of kikuyu would have reduced the under-ground reserves and hence competitive ability of kikuyu while clovers are still establishing.

Treatment with herbicide (such as glyphosate) can reduce the ability of kikuyu to recover after establishment and in so doing aid clover establishment.

Nitrogen fertilisation of the pasture to be over-sown should be halted at least a month before establishment to reduce the growth rate and recovery of the grasses after over-sowing.

Shallow cultivation of the kikuyu pasture with a rotavator, followed by broadcasting of the seed, has been reported to be effective in establishing clovers. This method creates an ideal seedbed for clover establishment, but is strictly not classified as a minimum-till system and the effect on subsequent kikuyu production is poorly understood.

If direct drilling clovers it into existing sward, rather than broadcasting it, care must be taken to ensure low speed and shallow placement.

For ryegrass-clover mixtures, the seeding rate of the grasses should be 12 kg ha-1 or lower to reduce the competion from the more rapidly establishing ryegrass.

Removing kikuyu re-growth when it exceeds 8 cm after establishment to ensure adequate light reaches the growing points of white clover is a good strategy to improve survival of seedlings.

Research at the Outeniqua Research Farm near George is investigating the emergence, persistence and dry matter production of grass-clover mixtures over sown into kikuyu using different establishment methods based on varying degrees of cultivation and herbicidal control.

This information will be used to improve the understanding and management of practices when over-sowing clovers into existing kikuyu pastures.

For further information or enquiries please contact Janke van der Colf or Dr. Philip Botha on 044 803 3700.

Article by: Janke van der Colf, Institute for Plant Production, Outeniqua Research Farm, George