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Dow Grassland: Weed control is crucial to making most from grass

Sponsored Article

Grassland is a sponsored series brought to you in association with Dow.

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Maximising grassland production to boost profitability is the focus of this new three-part sponsored series.

As livestock producers face ever-increasing pressure on margins, maximising production from low cost, home-grown grass through careful management and targeted weed control will go some way to boosting efficiencies. Grazed grass in particular represents the cheapest, highest value forage available, with the recent Welsh Grass Value Project putting its cost per tonne of dry matter at just £97, together with a substantial feed value of £197/t DM (see table).


Grass value

The Project looked at 12 grass-focused dairy farms between 2011 and 2013 and found herds which grew more grass and produced more milk from forage per hectare had a higher net margin per hectare.

 

Grass Value Project officer and farms manager for Coleg Sir Gar, Gelli Aur, John Owen says this clearly shows the value of grass.

 

“Focusing on producing the optimum dry matter yield of grass per hectare, combined with effective grassland management, results in high levels of grass utilisation, a good proportion of milk from forage, low feed costs and healthy profits,” he says.

 

“The key is to maximise the grass you grow per hectare and ensure you meet the full potential of swards and paddocks.” Mr Owen believes current market challenges means it is more important than ever for livestock producers to look at how they can maximise milk and meat produced from grazed grass to lower costs of production.

 

Together with looking at farm infrastructure, soils, animal type and overall management, weed control forms an important component in making the most from grass.

 

“Swards with a high proportion of weed grasses and broadleaf weeds grow 14 per cent less grass. That is 14 per cent off its value (of £197/tDM),” Mr Owen says.


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Sponsored Article

Grassland

Grassland is a sponsored series brought to you in association with Dow.


Negative impact

Docks and thistles are the main offenders on livestock units. The fact one dock plant can produce 30,000 seeds means a dock infestation can quickly get out of hand and significantly impact on grassland productivity.

 

Andy Bailey, grassland agronomy expert from Dow AgroSciences, explains: “A 10 per cent population of docks or thistles means you are losing 8t DM in a 8ha field producing 10t DM/ha. This means you are losing 88,000MJ of potential energy, or 16,604 litres of milk,” he says (see table).

 

“You need to make up this difference in some way, be that buying-in concentrate or taking on more land.” Weeds also reduce the feed value of the grass crops, with docks having 60 per cent of the feed value of grass.

 

The presence of thistles also affects cattle and sheep grazing patterns, with stock choosing to graze around the weed, creating a ‘halo effect’ and reducing pasture utilisation. Thistles are also linked to the spread of orf in sheep.

 

Weeds can be a particular issue on silage ground, with their presence reducing overall silage quality. The woody stalks of docks are also associated with puncturing bale wrap, allowing oxygen to penetrate and resulting in silage spoilage. This, in turn, leads to reduced palatability, quality and feed intakes.


Grazing

Mr Owen says grazing management can help maximise performance from grass and keep weeds at bay. and-in-hand. Rotational grazing is a good way to keep weeds under control as there is less selection of grazing,” he says.

 

Mr Owen advises producers to start grazing at a platemeter reading of 2,800-3,000kg DM/ha, down to a residual of 1,500kg DM/ha. This will encourage sown species to thrive, leading to fewer weed grasses and broadleaf weeds.

 

Mr Bailey agrees and explains the aim should be address anything which is detrimental to grass growth. He says: “It is all about making sure the grass is at its most competitive (to outcompete weeds). Maintaining dense swards is very important in reducing the prevalence of weeds.”

Management


Management 

Weeds will quickly invade open spaces, so minimising poaching is an important tool in the weed control box. Dock seeds can also survive in the soil for 30 years and will quickly take advantage of any gaps in the sward.

 

To prevent poaching, move troughs around fields, ensure multiple entries to paddocks and set up cow tracks.

 

Regular soil testing to identify and address soil imbalances is also crucial to promote soil health and grass production.

 

Mr Bailey says the end of March is a good time to be identifying weed challenges and selecting appropriate treatments so weed control strategies can be planned in advance.

 

“To make sure you get the most out of a herbicide, the key is to apply it at the correct stage, which is the rosette stage in docks and thistles,” he says.

 

Mr Owen says choosing whether to do a complete spray should be based on economics, with weed infestations of more than 10 per cent likely to yield the best return. "When weed populations are less than 5 per cent it will be more cost effective to use a knapsack product like GrazonPro," says Mr Bailey.

 

“Product choice should focus on long-lasting herbicides which will be translocated down into the roots to give a higher level of control versus a quick-acting herbicide that kills the foliage but not the roots,” says Mr Bailey. “And make sure you use the right dose rate and water volume.”

 

He also advises against topping as a weed control strategy as this is not an effective short-term control method for docks and thistles.


The value of grass lost due to different populations of docks or thistles in an 8ha (20-acre) field

Population of docks Lost grass due to weeds (t DM) ME value of lost grass (MJ of energy) Volume of extra milk that could be produced from the energy lost (litres)
10  8 88,000 16,604
20 16 176,000 33,208
30 24 264,000 49,811
40 32 352,000 66,415


This data assumes the field is capable of producing 10t DM/ha at an ME of 11MJ/kg DM and 100% of the available DM is utilised.

For more advice on controlling weeds in grassland, visit www.grassbites.co.uk, or call the Dow AgroSciences technical hotline: 0800 689 889, or email UKHotline@dow.com

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