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Plant Physiology

In the UK, perennial ryegrass is the most widespread species of grass for grazing animals. A perennial ryegrass field is made up of a population of ryegrass tillers. A tiller is made up of a basal stem, a leaf sheath and – at any one time – three growing leaves.

 

When the tiller has developed three leaves it will continue to grow. As a fourth new leaf is produced the oldest leaf starts to die. Then a fifth leaf is produced and the second leaf dies – and so the process continues.

 

Tillers are largely individual but are clumped together, meaning they can (to some degree) exchange nutrients. The average field will contain between 3000 to 5000 tillers per square metre.

 

Perennial ryegrass plants will produce new tillers throughout the growing season with peak production occurring from late April to July. The time it takes for a tiller to produce three leaves will vary, depending on the plant, the local climate and the time of year.

 

 

 
Ryegrass clump   Ryegrass tiller

 

In mid spring it may take 15 days for a tiller to produce three leaves, with a new leaf produced every five days thereafter. In colder periods, it may take up to 50 days for a tiller to reach the three-leaf stage, with a new leaf produced every 17 days.

 

Tiller leaf production


Typically, fields grow in three phases, working in line with tiller production and energy reserves:

  • The lag phase – where grass is typically less than 1200kg DM / ha
  • The linear phase – where grass is typically between 1200 and 3500kg DM / ha
  • The ceiling phase – where grass is typically above 3500kg DM / ha.

 

During the lag phase the tiller grows its first leaf; in the linear phase the second and third leaves develop; and in the ceiling phase the fourth leaf develops and the first leaf starts to die off.

 

When striving for peak grass performance, the aim should be to maintain grass growth in the linear phase of development, where high net growth rates and high grassland quality are achieved.

Three phases of grassland development

 

 

Grass Seed Quality

IMPORTANT FACTS TO CONSIDER WHEN BUYING SEED.

 

Few farmers would rely on genetics from the past for livestock breeding but many stick with the same grass seed varieties and mixtures year after year – even if they aren’t delivering the best results.

 

For some farmers, the prospect of picking a new grass can seem daunting. There are hundreds of different varieties, blends and mixtures available – so how do you know which one will work best?

 

If you are unsure about which product to pick, we advise selecting a grass seed from one of the UK’s Recommended Lists. Bred to perform in UK conditions, grasses included on Recommended Lists have been have been tried and tested by farmers, who’ve seen real results.

 

As a starting place, perennial ryegrass remains the most popular form of grass for grazing animals in the UK. But there are many other varieties that the farming sector relies on including clover, herbs and other forms of forage crops. Used in conjunction with modern grass varieties, in specially devised blends and mixtures, these can bring big yield benefits – giving animals additional essential vitamins and minerals to help weight gain, while also reducing nitrogen fertiliser requirements.

 

Below,  we’ve put together a quick guide to the main species available, and most beneficial to UK farmers.

  

 Species  Description Min germ
temperature		  Seeds/kg
RYEGRASSES All ryegrasses are capable of producing high yields of very high quality, high energy grass for cattle grazing. They are all very flexible and can be used for both cutting and grazing. They are very effective users of nitrogen but must be maintained well to maximise productivity.    
PERENNIAL RYEGRASS
Lolium perenne		 The most popular grass used for dairy enterprises. Generally persistent for up to five years. 7-8°C 600,000 (dip)
290,000 (tet)
HYBRID RYEGRASS
Lolium hybridum		 Can extend the shoulders of the grazing season. Hybrid grasses are also persistent for three to five years depending on genetic capabilities and can produce up to 10% more dry matter than perennials. 5-6°C 450,000 (dip)
269,000 (tet)
ITALIAN RYEGRASS
Lolium multiflorum		 Generally found in short-term silage mixtures, it is a two year species that grow to temperatures as low as 3-4ºC and can extend the grazing season by three to four weeks in spring and autumn. Italian ryegrasses are capable of producing up to 20% more dry matter than perennials. 4-5°C 430,000 (dip)
265,000 (tet)
WESTERWOLD
Lolium mul. westerwoldicum		 Rapidly establishing annual species which gives high productivity within 12 months of sowing. This species is useful for sowing immediately after maize or cereal harvest in autumn or in spring, when high yields are required within 3-6 months of sowing. 3-4°C  400,000 (dip)
221,000 (tet)

 

 

Species Description Min germ
temperature		 Seeds/kg
CLOVER Clover fixes nitrogen in the soil (figures of 170-220kg N/ha/yr are achievable) -
and is therefore a very valuable species in efficient grassland management.		    
WHITE CLOVER An absolute essential for any grazing livestock system. This perennial species provides ‘free’ nitrogen, which has been fixed from the atmosphere, and can feed companion grasses. Adding white clover to grassland can increase sward digestibility, especially in the summer period. It can also improve grass protein levels and trials have proved increase intakes on grass / clover swards compared to grass alone. 9-10°C 1,500,000
RED CLOVER Red clover is a useful plant for lactating cows and can help boost milk production but should be avoided by pregnant and breeding animals. When well managed, red clover can persist for up to five years, fixing around 50 kg N/ha/annum more than white clover. Usually sown with Italian ryegrass in short-term leys, it can also be sown with perennial and hybrid grasses to extend the lifetime of a sward by helping to suppress weeds. Red clover is typically quicker to establish than white clover although not as long lasting or tolerant of poorer conditions/management. 9-10°C 520,000

 

Weeds

Identification

There are lots of weeds that can invade pastures, and here we have tried to list all the ones that are relevant to grassland and pasture in the UK.
For more specific advice on how to control weeds in your grassland visit Dow Agrosciences website at http://uk.dowagro.com/product-category/grassland/

  

   

Annual Meadow-grass is a low-growing grass which is a light green colour.


It grows from a central base, to which all the shoots can be traced, and has a creeping rootstock.


The blade-like leaves are blunt-tipped and the yellow-green flower head is triangular with branched spikelets that contain the flowers.
     
 

There are 150 species of thistles worldwide, with 20 in the UK

  • Thistles need controlling as they compete with grass for space, light, nutrients and water
  • Thistles are unpalatable to stock and reduce the available grazing, whilst increasing the incidences of Orf
  • The two most common and damaging are creeping thistle and spear (Scotch) thistle
  • Creeping Thistle (Cirsium arvense): A perennial that grows from seed or from root sections in the soil Once established, the root mass can be greater than the plant above ground, competing effectively with the grass
  • Spear Thistle (Cirsium vulgare): A biennial that grows from seed, and in the first year often goes unnoticed, since it produces only a small rosette. In the second year the plant can grow to over a metre in diameter before flowering, posing a serious economic threat.
     
  Favouring high-fertility sites, nettles spread through tough roots forming clumps
  • Nettles compete with grass for light, water and nutrients and, where nettles are dense, will out-compete the sward
  • Grazing stock avoids mature nettles, reducing the productivity of the swards
  • Nettles in hay or silage may cause rejection by stock because of the contamination
  • Best controlled in the spring when they are 30-45cm tall
  • Frequently cutting nettles often results in more vigorous regrowth.
     
    Docks (Rumex spp.) are the most pernicious and damaging of all grassland weeds.
  • Docks compete with grass for light, nutrients and moisture and reduce grass yields and have less than 65% of the feed value of grass
  • Docks are unpalatable and, in general, animals will only eat them if there is nothing else available. Excessive quantities of docks in the diet can cause dietary upsets, especially in young animals. When fields become infested with docks, the available grazing is reduced, which then impacts on the planned grazing cycle. Presence of docks in silage can affect fermentation, thus reducing overall quality.
     
  A critical weed to be able to identify, and remove, is Ragwort. This weed is potentially deadly to livestock and is listed in the Injurious Weeds Act, which occupiers can be required by law to control. Under the Ragwort Control Act (2003), a code of practice was developed giving guidance on identification, priorities for control, methods, environmental considerations, and health and safety issues.
  • They have a daisy-like yellow flower, flowering from May to October
  • Ragwort is a danger to all stock, but particularly horses, cattle, free-range pigs and chickens. Alkaloids cause cirrhosis of the liver and there is no known antidote
  • Ragwort is largely unpalatable; ragwort may be eaten when green, particularly when other grazing is sparse. It is palatable when dead or dying because of the release of sugars, so contamination of hay or silage is very dangerous.
     
  Common Chickweed is the most common annual weed and can persist in rotational grass and establish in long-term pastures where there are gaps in swards due to poaching or slurry injection.
  • With a prostrate habit and fast growth, chickweed restricts tillering of establishing grass and clover and fills in bare spaces in swards
  • Autumn sowings can be a problem as chickweed may overtake the slower establishing grasses and clovers, filling in bare patches
  • Its high moisture content will cause difficulties when trying to wilt for silage and also upset silage fermentation affecting the feed value
  • It will also mean a longer drying time for hay-making with loss of quality
  • Large chickweed populations may cause digestive upset in grazing lambs and calves.
     
  Creeping buttercup is the most common species and is a problem in heavily grazed, poached or wet pastures.
  • Animals tend not to graze areas infested with buttercup as it has an acrid taste and affects grass yield and reduces hay value.

Diseases

Identification

 

 

Characterised by scattered orange spores over the leaves, seen in late August
and September.


Occurs with high rates of grass growth combined with warm days and dewy nights i.e more uncontrolled growth results in more dead material at base of plant (higher probability of harbouring spores).


Tends to reduce yield as a result of plant stress and decrease in palatability.


Spread by wind and rain splash
     
     

A fungal infection that produces brown spots surrounded by yellowing tissue, which is encouraged by wet and cloudy weather.

 

Cattle reject infected areas leading to excess growth and more disease build up.

 

Controlled by variety selection and excess growth management, topping grazing and encouraging new growth.

 

Spread by spores, wind and rain.

 
     
 

Characterised by White “sappy substance” and becomes more active during the spring and autumn periods.

 

Spores are produced in warm, humid conditions and damage leaf area, reducing yield and palatability. Particularly susceptible plants are the faster growing ryegrasses species such at Italians.


Spread by wind and rain splash and remain dormant through winter periods to become active early spring. Dead material and excess growth provide shade and high humidity, the ideal environment for mildew!
     
 

Brown Rust occurs early in the season, during April and May and throughout England and Wales.

 

It only affects ryegrasses and is a different species to the brown rusts that infects wheat and barley.

 

It can reach moderate levels in  some varieties, but most have good resistance.

Pests

Identification

 

 

 

 

The Grey Field Slug (Deroceras reticulatum) is particularly active in wet seasons especially on the heavier soil types.


It feeds on the shoots of newly germinated seeds, killing the plant entirely and may leave large areas completely devoid of plants.

 

Damage is therefore most likely on direct reseeded leys. Other symptoms include shredding of the leaves of older plants. Slime trails would also be obvious.
   
  The larvae of several species of chafer beetle can also cause damage to grassland in various parts of the UK. The adults are 8-10 mm long with a green head and thorax and reddish brown wing cases:
  • The grubs are white and about 18-20 mm long when fully grown
  • The feeding of the larvae produces patches of poorly grown grass that may turn very brown in dry weather
  • Damage is most likely to be seen in September–October
  • Substantial bird activity may indicate infestation, as they actively search out the grubs
  • Once infested, pastures tend to be re-infested in subsequent seasons unless they are treated with an appropriate agrochemical.
   

This larva of the Frit fly (Oscinella frit) attacks all cereal and grass crops, especially those following grassy stubbles or grass.

 

The Frit fly larvae are yellow-whitish in colour and can grow to 5 mm long.


To help prevent Fritfly, leave a 10 week gap between the previous grass crop or grassy stubble. If grass is sown after, grass seedlings will be attacked by larvae migrating out of the old sward in addition to those hatching from eggs laid by incoming adult flies. The problem is more acute in direct drilled reseeds than reseeding after ploughing.
   
Leatherjackets are the larvae of Crane-flies (Tipula spp), also known as Daddylong-legs. These soil living larvae cause considerable damage to roots and stems of many agricultural and horticultural crops, particularly of young plants.
  • Legless, grey brown thick, tough wrinkled skin - growing to about 2 inches in length
  • On established grassland high infestations may result in large bare patches appearing in the field. With low levels of infestation spring growth may be impeded.
  • Reduces yield and, at the economic threshold of 1 million leatherjackets per ha, the weight of leatherjackets feeding below ground can be greater than the  weight of livestock above ground. New sowings or reseeded leys may be completely destroyed
  • The presence of large numbers of rooks, crows and starlings also indicates the presence of large populations of leatherjackets.
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