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Cropping Into Kikuyu

Cropping Into Kikuyu
Herbicide use and regrowth of pastures

Nuts & Bolts

  • rejuvenates kikuyu and improves sub-clover, kikuyu mixture;
  • a low cost, low input system;
  • double knockdown, glyphosate followed by Sprayseed® if late break, or one application of glyphosate, if early break;
  • two applications of atrazine (pre and post emergent) in canola to control silver grass
  • two years of cropping, provides a cash crop and hay crop;
  • controls silver grass; and
  • kikuyu regrows well with summer rain, pasture comes back with more vigour.

The perennial pasture grass kikuyu is highly suited to some parts of the South Coast sandplain of Western Australia, but even when well managed, the pastures gradually decline in productivity. To look for solutions South Coast NRM through the Climate Action on Farms project, talked to two South Coast farmers who are rejuvenating their kikuyu pastures by cropping into them.

Ken Reddington and son Paul crop canola followed by oats or triticale for hay on their Bremer Bay farm, while Adrian Anderson uses a standing lupin crop to fatten his prime lambs and add nitrogen to the following pasture phase on his Wellstead property.

The South Coast sandplain is at high risk of wind erosion. Kikuyu pastures, in areas with suitable rainfall, help stabilise sandy soils; provide out-of-season feed; and fill the autumn feed gap. The kikuyu, sub-clover mixture in winter pastures provides high quality feed for sheep and cattle. 

Although kikuyu is a good option for sandy soils, farmers have reported noticing reduced productivity because of thatching, decreasing amounts of sub-clover and increasing silver grass when kikuyu has been long established. One solution is to pasture crop. The Reddingtons and Adrian Anderson have different cropping systems, but both found that after the cropping phase, provided there is spring and summer rainfall, kikuyu responded with good regrowth. The sub-clover also returns with winter rain and the silver grass disappeared, providing much higher quality pasture.  

The Reddingtons system at Bremer Bay.

Cropping into kikuyu picture 1

Ken and Paul opened up the thatch in their 20-year old kikuyu paddocks by working up the kikuyu.

mechanically.  After noticing this caused it to respond by coming back with more vigour, Paul suggested that cropping with canola into the kikuyu paddocks might be the answer to rejuvenating the kikuyu and canola’s long taproot may help aerate the soil. Thinning out the kikuyu would also prevent it choking out the sub-clover. As a result over the past four years, they have now cropped 75-150 ha per year into their kikuyu.

Ken and Paul’s approach in cropping into perennials is to keep the system low cost, low input. Under their current system they get a cash canola crop, followed by a hay crop. So far they have been in front financially, because of the return on the crops and the improvement in the pasture phase.

The Reddington’s first tried one year of cropping and then let the kikuyu regrow, but they found that two years of cropping thins out the kikuyu more effectively and is important in removing the silver grass. They now crop the first year with canola and follow with a hay crop of triticale or oats. The system has also assisted with weed control where Silver grass and geranium are their main weed problems. Two years of cropping is effective in controlling the silver grass, although they have had to use 2,4-D on geranium which grows  in gaps between the kikuyu.

In future Ken and Paul plan to  crop each kikuyu paddock once every five years or so in rotation, but also see the advantage in keeping the system flexible and being able to respond to the season. In a good year they might put extra paddocks into crop.  If the season is shaping up to be a dry one they will crop less and use less inputs.

Herbicides, knockdown and re-establishment of kikuyu

Cropping into kikuyu picture 2

As all farmers would know the amount of herbicide required to suppress the kikuyu depends on seasonal conditions. The Reddingtons generally do a double knockdown, with 540 g/litre glyphosate at 2 litres/hectare (ha), followed up with Sprayseed ® (1.5 litres/ha). With an early break, the glyphosate   effectively suppresses all the kikuyu. They have used atrazine at 2 kilogram (kg)/ha post seeding to control silver grass in the canola crop, but in future will split the atrazine to two applications of 1kg/ha, one pre-emergent and one six weeks later for better control.

Ken and Paul use a disc coulter in front of a double disc V shaped opener to cut through the kikuyu, with press wheels behind. The discs cut through the kikuyu and release the nitrogen bound up in the thatch. They seed Triazine tolerant (TT) canola at 3.5-4 kg/ha and apply 100 kg/ha Agras at seeding in two applications, followed by one or two applications of up to 75 kg/ha NS31, depending on the season. They use alpha-cypermethrin (400 ml/ha) and 150 ml/ha of Le-mat to control mites in the canola. They use 80 kg/ha  Agras in seeding the following cereal crop.

The regrowth of the kikuyu after cropping has been good, particularly in seasons with more summer rain. When they cropped for only a single year, the kikuyu came back too strongly to allow good sub-clover recruitment. The Reddingtons' get good kikuyu regrowth even after two successive years of cropping because they average 25-30% of their annual rainfall in summer. Experience is showing they can use a lower rate of glyphosate on the kikuyu in the second year because there is less regeneration of kikuyu.

Herbicides in the Reddington system

  • For canola, a double knockdown with 2 litres/ha of 540 g/litre glyphosate plus Sprayseed® (1.5 litres/ha), one application of glyphosate is sufficient in early breaks
  • For the following cereal crop, 1.5 litres/ha of glyphosate
  • Atrazine (2 kg/ha) for silver grass in the canola ( in future will split into two applications pre and post emergent)
  • Two years of cropping controls silver grass and thins out the kikuyu sufficiently to allow good regeneration of clover
  • 2,4-D to control geranium in kikuyu gaps as it regrows

The South Coast, like  many regions in Australia, has a variable climate and the Reddingtons know flexibility in adapting to seasonal conditions is the key to cropping into perennials. Paul is keen to trial other perennials to complement the system and increase flexibility.   

After four years of cropping into kikuyu Paul said,

“We are still feeling our way with the system because everything depends on the particular season.”

Adrian Anderson’s system at Wellstead

Profile

Farmer: Adrian Anderson

Location: Wellstead

Property: 5000 ha,

Rainfall: 550mm

Enterprise mix: Merino self replacing,

prime lambs (Wiltshire, Dorper, Van Rooy), beef cattle, sheep and cattle trading

Soils: sandy duplex, south coast sandplain

Nuts and bolts

  • system rejuvenates kikuyu, brings sub-clover back into the pasture, controls silver grass
  • lupins provide extra nitrogen and provide high quality feed for fattening prime lambs
  • re-growth of kikuyu can be slow with low spring and summer rainfall

Adrian Anderson planted his kikuyu after the Reddingtons but also found his kikuyu pasture quality was declining over time. He now crops into kikuyu to break up the thatch and rejuvenate the pasture, control silver grass and bring back clover, but in his case with lupins. He doesn’t harvest the lupins but grazes them as a standing fodder crop to fatten his prime lambs. The lupins provide extra nitrogen for the kikuyu and his rejuvenated kikuyu, clover pasture provides fattening quality feed for lambing in August.

To achieve best results Adrian sprays his declining kikuyu paddocks in late May with 1.5 litre glyphosate plus 1.1 kg simazine, ammonium sulphate, wetter, 400 ml cypermethrin, and 100 ml omethoate per hectare. Adrian stresses the need to include cypermethrin to control wire worms and balaustium mite “both of which can devastate emerging lupins”.

The lupins are sown in early June at 100 kg/ha using a disc drill with coulter discs and Baker Boots. He includes granula inoculant at 8 kg/ha and manganese sulphate at 20kg/ha.  Adrian found the lupin seed needs to be placed under the kikuyu thatch or germination is poor. He also broadcasts SuperPotash 4:1 at 200 kg/ha. He generally doesn’t have to spray again unless there is a re-invasion by balaustium mite. Adrian found this mite can appear in large numbers in kikuyu and “can devastate lupins”. If there is a major germination of grasses he indicated he would follow up an application of Fusilade®.

Fattening prime lambs

Adrian generally stocks his lupins at 20 lambs/ha for two months beginning mid- December.  They fatten very quickly growing at about 2 kg/week. He has been able to stock the lupin paddocks for as long as five months, gradually reducing his stocking rate to 10 sheep/ha.

The kikuyu re-growth in spring depends on rainfall. However Adrian has found that as long spring rainfall is average or more, the kikuyu re-establishing under the lupin crop is up to 100 mm high and provides greater than 70% groundcover. However, during a dry springs it can be too thin and subject to wind erosion in autumn. During the year following the lupin crop, the pasture has a higher proportion of clover, is silver grass free and has much higher animal production than the old kikuyu paddocks. The rejuvenated kikuyu persists in that state for several years.

Cropping into kikuyu picture 3Herbicides in Adrian Anderson’s system

  • 1.5 l/ha glyphosate plus 1.1 kg/ha of simazine in tank mix with ammonium sulphate, spray adjuvant, and cypermethrin for balaustium mite control.
  • Follow up spray with grass selective herbicide if major germination of kikuyu (it can regenerate densely in July

Conclusion

Experience from the Reddingtons and Anderson’s has proven that cropping into kikuyu paddocks on the South Coast sand plain is an effective way of rejuvenating pastures. The regrowth of kikuyu after herbicide suppression is dependent on spring and summer rainfall.  With good rainfall the kikuyu rapidly provides sufficient ground cover to prevent wind erosion in autumn. By the following winter the pasture is highly productive. In locations or seasons with less late spring and summer rain there may be poorer regrowth after cropping and increased risk of wind erosion in autumn. One of the main problems pasture cropping with canola or lupins on the south coast experience is controlling the balaustium mite which build up in large numbers in kikuyu pasture.

With one year of cropping it is likely some of the regeneration of kikuyu is from rhizomes and some from seed. With two years of cropping it is more likely that most of the recruitment is from seed.

Cropping into kikuyu allows farmers the ability to take advantage of unseasonal rainfall events and be opportunistic and grow a cash crop if conditions are favorable, making their farming systems more robust against future climate variability with the added bonus of rejuvenating old kikuyu pastures.

Farmer Profile

Farmers: Ken and Jan Reddington, son Paul and his wife Alice
Location:  Bremer Bay, Western Australia
Property: 2000 ha
Rainfall: 520mm, with 25-30% as summer rainfall
Enterprise mix: 80% livestock, 20% cropping (some for hay), sheep for prime lambs and fine wool merinos, cattle for vealer production. Tactical cropping.
Soils: south coast sandplain, sandy duplex, non-wetting

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