Establishing a grass-white clover sward on your farm

Establishing white clover on farm will take a number of years using a combination of reseeding and over-sowing. Incorporating white clover in a full reseed is the most reliable method of establishing white clover and provides the best opportunity for weed control.

Over-sowing is a simple and low cost method of introducing white clover into swards. Success is very much dependent on soil fertility, weather conditions at sowing, soil moisture, post-sowing grazing management and competition from the existing sward. Suitable paddocks for over-sowing are those with good soil fertility, high perennial ryegrass content and low weed content.

Reseeding

Aim to reseed as early in the year as possible (April, May, June) when soil temperatures are high and increasing, and there is adequate opportunity for weed control.
Soil sample for P, K and pH
Spray off the old pasture with a minimum of 5 L/ha of glyphosate; allow a minimum of 7 to 10 days after spraying before cultivating.
Prepare a fine, firm seedbed.
Use grass and white clover varieties from the Irish Recommended List
Cattle sowing rate – 28 to 30 kg/ha of grass plus 5 to 5.0 kg of medium leaved clover.
Sheep sowing rate – 25 to 28 kg/ha of grass plus 5.0 to 6.0 kg of small leaved clover.
Avoid sowing white clover seed too deep – sowing depth approx. 10 mm.
Apply 40 kg N/ha (30 units N/acre) at reseeding
Apply P and K fertiliser as required
Roll well to ensure good contact between the seed and the soil
Apply 25 kg N/ha (20 units N/acre) 4-6 weeks post sowing

Over-sowing

Do not over-sow old ‘butty’ swards with a low content of perennial ryegrass – white clover will not establish well in these swards
Control weeds before over-sowing white clover as weed control options afterwards are more limited.
Some herbicides have a residue of up to 4 months – always check the residual time on the label of the product or seek advice on a suitable weed control product.
Take a representative soil sample for P, K and pH analysis and correct soil fertility prior to over-sowing. Optimum soil fertility when over-sowing will help increase the chances of success.
White clover seed can be broadcast onto the sward or stitched in using a suitable machine.
If broadcasting with a fertiliser spreader:

Mix clover seed with 0:7:30 fertiliser and only add white clover to the spreader when you are in the field to avoid white clover settling at the base of the spreader.
Do a maximum of 1 ha at a time (to avoid seed settling) and spread in 2 directions across the field.

Stitching in white clover seed with a drill/harrow ensures better seed to soil contact. Stitching must be used for over- sowing sheep grazed swards due to the denser nature of swards.
Over-sow directly after grazing (≤ 4 cm post-grazing sward height) or after cutting the paddock for surplus bales – ideally only over-sow three to four paddocks at a time.
Sow at a rate of 5.0 to 6.0 kg of white clover seed/ha.
Soil contact post over-sowing is one of the most crucial factors affecting germination.

Roll paddocks post-sowing to ensure soil to seed contact.
Apply watery slurry (if available) – ideally around 2000 gallons/ac.

Reduce N fertiliser post over-sowing to 15 kg N/ha (12 units N/acre) per rotation for two rotations to reduce grass growth.

Michael Egan, Teagasc gives tips on how to oversow White Clover

White Clover Establishment Blueprint

A targeted multiyear approach should be used in establishing a white clover system, combination of reseeding and over-sowing.

Reseed 10% per year
Over sow 20 % per year

Yr 1- reseed 10% & over sow 20% = 30%
Yr 2- reseed 10% & over sow 20% = 30% (60%)
Yr 3 – reseed 10% & over sow 20% = 30% (90%)
Yr 4 – remaining 10% + any ground that clover didn’t establish on (100%)

Paddocks for a full reseed should be identified (poor performing, age of sward, weed content) as early as possible in the process to avoid over-sowing clover.

Select paddocks for over sowing to give the best chance of establishment:

Optimal soil fertility (index 3 or > for P & K, soil pH 6.5)
High perennial ryegrass content
Open/low density swards – dense swards prevent light getting to new clover plant, hindering establishment
Low weed content

Any paddocks that are not suited for over-sowing in the first year (but not ear marked for reseeding) should have any issues corrected and over sown the following year; correct soil fertility issues, spray any weeds well in advance of over-sowing to allow for residual time frame.

Weed control in reseeded and over-sown grass-white clover swards

Reseed

Use a clover safe herbicide.
Weeds in new reseeds are best controlled when grass is at the two to three leaf stage.
Docks and chickweed are two of the most critical weeds to control; it is important to control these at the seedling stage.

Over-sown

Control established weeds before over-sowing as weed control options post-sowing will be limited.
Consider residue time of non- clover safe sprays from application of spray to over-sowing the white clover – it can vary from one to four months. Contact your local advisor or merchant for advice if spraying before over-sowing.
For established grass-white clover swards ensure the herbicides used are white clover safe options.
All pesticide users should comply with the regulations as outlined in the Sustainable Use Directive (SUD).

Clover Content Scorecard

The clover content scorecard is a tool that farmers can use to identify the level of clover in their grass swards. View or download the Clover Content Scorecard (PDF)