Philip Cosgrave

Grow Your Grass with Philip Cosgrave

Keep up to date with all the latest grassland agronomy advice with this regular column from Yara's chief grassland agronomist Philip Cosgrave.

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 Four steps to successful reseeding

24 June 2020


Benefit of reseeding on net rofit

Step 1 : Identify poorly performing paddocks.

Step 2 : assess their content of desirable grasses. If this is less than 60% consider re-seeding. Annual meadow grass and other weed grasses produce lower yields, poorer feed quality and do not respond well to applied nutrients. Yield will be reduced by 1 % for every 1 % in weed ground cover.

Step 3: Take a soil test and act on the results. Before you start, be sure to complete this step. On mineral soils the optimum pH for grass is 6.3. Failing to correct pH will severely impact the success of your reseed. Choose only varieties from the Recommended Grass and Clover Lists (RGCL) and pick those that suit your particular farm.

Step 4: Provide new swards with the correct nutrients at sowing. Failure to do so will hinder the success of the ley. Where clover isn’t included, and the soil P & K index is 2, then use 330 kg/ha YaraMila ACTYVA S (16-15-15 + 6.5% SO3) at establishment. New leys have a greater requirement for phosphate to help with root development, and a lower requirement for nitrogen.

My Top Tips: Weeks 4-6 (post-emergence) apply herbicide to prevent weeds competing for nutrients and space. Graze lightly with youngstock or sheep, as soon as the new plants don’t pull out of the ground, which is usually when grass height is at 6 - 7 cm or at the two leaf stage to promote new shoots, and thus the long term productivity of your new sward.

See our new sown grass fertiliser programme

Controlled traffic farming

23 June 2020

Adopting Controlled Traffic Farming (CTF) could help reduce soil compaction risk and boost yields by up to 10.5%, while also reducing nitrous oxide emissions.

Limiting compaction at silage-making

Grassland farmers could benefit from adopting an ‘arable mindset’ and controlling the movements of machinery across fields as a means of limiting compaction and maximising grass yields.
This is according to Dr Paul Hargreaves, grassland researcher for SRUC, who has just completed a three-year study looking at CTF on silage ground. His results show grassland farmers could expect a yield increase of 8.5-10.5% by following a CTF system, while nitrogen use efficiency will also be improved.

Rather than driving anywhere on a field, CTF means machines follow set wheel marks which run parallel to the line of trajection and then around the headland. “It’s about trying to control the movements of machinery around a field to limit the area they cover and running all machinery along similar wheelings. It’s trying to think of grass as an arable crop,” says Dr Hargreaves. SRUC trial work found that about 83% of a field cut three times using a forage harvester, with slurry applied, will be covered in wheelings on a traditional system. These wheelings will suffer from soil compaction and therefore reduced yields. On a CTF system, the area covered in wheelings will reduce to about 19%.

SRUC trial results

The three-year trial at SRUC looked at long-term performance of a perennial ryegrass and red clover ley, which was established at the start of the trial. They looked at different nitrogen application rates and compared CTF and non-CTF. In the non-CTF strips, machinery was driven wherever they wanted. On the CTF strips, the fertiliser and slurry spreaders, mower, tedder, rake and forager, all followed a nine-metre working width.

Dr Hargreaves was keen to see the damage caused to the wheelings on the CTF system over the three years. Although there was an increase in soil bulk density and reduced porosity, he says there was ‘limited damage’ and no issues with water run-off from these areas.
“So far, we’ve seen a reduction in yield on those wheelings and the red clover has disappeared entirely, but the perennial ryegrass is still there,” he says.

He believes this is not a huge issue on a three-year red clover ley as the issue could be addressed as part of reseeding. If a farm was doing CTF on a five to six-year perennial ryegrass and red clover ley, some kind of mitigation work would be needed on these wheelings, such as sward lifting. Wheelings would then need to be shifted across in the next season so improvement work was not compromised.

Overall, Dr Hargreaves says focusing traffic in set areas helps minimise overall field damage.

“You are reducing the structural damage to soils so you are potentially maintaining drainage and the quality of the soil. And you know where the damage is on the field so you can deal with it specifically,” he says.

Why is compaction a problem?

  • Limiting soil compaction should form part of an holistic approach to soil management which should also look at pH and maintaining key nutrients such as potash and phosphate. There are some key reasons why compaction should be avoided:
    Prevents water infiltration – resulting in wet soils which take longer to drain.
  • Reduces soil pore spaces – so earth worms can’t do their job. Oxygen needs to get into the soils and carbon dioxide needs to escape. This is compromised if soils are compacted.
  • Reduces nitrogen utilisation – anaerobic soils will reduce the mineralisation of key nutrients such as nitrogen.
  • Increases nitrous oxide production (a greenhouse gas) – this gas is a product of denitrification, a biological process by which some nitrate in the soil is reduced to nitrous oxide. The rate of denitrification is increased in compacted soils, because of the lack of air as they’re denser and wetter for longer.
  • Reduces nutrient availability – such as phosphate.

Operating Controlled Traffic Farming

To operate CTF, Dr Hargreaves suggests thinking about the following:

What is the smallest working width of all your machinery?

If your smallest working width is nine metres, all equipment needs to work within this. This includes the slurry spreader, tedder and mower, etc. This means machinery will have to work along three-metre-wide tyre tracks in the field.

Split up fields

Divide the width of each field by the working width of your machinery. If a field is 135 metres wide and your smallest working width is nine, split it into 15 lines. If you end up travelling more on certain areas of the field, make a note of it and target soil improvement work in this area.

Use technology

Dr Hargreaves believes GPS and auto-steering technology is essential to do CTF properly. However, as a minimum he thinks GPS is essential. This will increase accuracy.
“Newer tractors being sold and equipment used by contractors often have GPS. This technology is becoming increasingly common place so it could be a case of just using the technology you’ve already got,” he says.

Use marker posts

If technology is not an option, consider using sight posts or positions in the field so machinery is driven in a particular route. All individual tractor drivers will need to pay care and attention.

Pay attention during carting

The distance between the forage harvester and silage trailers will increase with CTF – potentially to
six metres. This means the team will have to work steadily. Also, consider using high-sided trailers and not filling trailers all the way to the top.

Read more on the benefits of CTF

Keep the pedal to the metal

22 June 2020

With 1st cuts at below average, particularly those cut in the latter half of May, and very slow 2nd cut regrowth, we may be feeling slightly nervy when looking at our silage pits. Grass gowth rates are well back on last year, so we’ll need some good growth in the months ahead to build up silage stocks. The rain has helped lower soil moisture deficits, but they’re still restricting grass growth.

On intensive grazing farms where growth rates have responded to rain, maintaining a 21 day rotation and keeping residuals of 4 cm is crucial. If paddocks have gone stemmy, pre-mow to get them back on track, alternatively target these for silage. Heavy covers of > 3,000 kg should be cut as surplus bales, and maintain grass growth by keeping N + S applications up-to-date. Slurry should be applied where silage/surplus bales are taken off. Remember to keep ammonia emissions as low as possible by using low emission spreading equipment such as trailing shoe. If slurry is not available, then apply a NPKS quality compound fertiliser such as YaraMila Silage Booster to replace P and high K off-take from taking surplus bales.

For N applications on a 21 day grazing rotation, 1 – 1.2 units N/acre/day is sufficient. Between the release of mineralised N from soil organic matter following the rain, together with residual N from fertiliser applications that hadn’t been used by the grass due to the drought, means there’s quite a large pool of nitrate available in the soil to meet the demands of increased growth rates. So, no benefit in over applying N.

With 1st cuts below par and 2nd cuts delayed, it might be prudent to look for alternative ways to put tonnes of silage in the pit. Buying standing crops of spring barley for wholecrop for instance or direct drilling Westerwolds into stubble for a late silage cut, can make up some lost tonnes. Alternatively, drill a forage brassica crop into stubble for grazing in Autumn/Winter.

Read more on increasing grassland yield

Hot topics: New season nitrogen, boosting maize and cow health

08 June 2020

New season nitrogen – do your research

Whether it’s new season or this season’s nitrogen requirements you might be considering to purchase, don’t end up with fertiliser that’s not fit for purpose. This can mean a wrong grade or choosing a product that looks good on price but doesn’t have the spreading quality characteristics. The wrong grade could mean purchasing straight nitrogen instead of nitrogen and sulphur. For quality, some nitrogen products look good but flatter to deceive as the granules look big but they’re soft, so shatter easily on the vanes of the spreader. So, caveat emptor!

Read more on nitrogen and sulphur

A nutritional boost for maize

Maize crops are at an important stage right now and nutrition is really important for these crops as they undergo rapid growth and development. With the weather we’ve had, these crops need all the help they can get.
A foliar feed would be beneficial, either as a standalone application or in conjunction with a planned herbicide. YaraVita MAIZE BOOST is specifically formulated for foliar applications on maize and contains magnesium and zinc, the two most widespread nutritional deficiencies seen in maize. It also contains phosphate and potash, which may be limited in these dry soil conditions.

Read more on forage maize nutrition

Heathy grass for a healthy herd

Finally, keep up with P & K applications for grazing. The phosphate keeps levels in grazed grass topped up, which is particularly important in dairy herds. While potash applications where necessary, will help drought tolerance. Use a compound NPKS product like YaraMila STOCK BOOSTER S (25-5-5+5% SO3+Se), which provides the full gambit of nutrients to grow more grass this summer.

Read more on the benefits of selenium

Reach that maize yield potential with foliar nutrition

05 May 2020

Maize has a high demand for nutrients due to its high yield potential. These high yields of 40+ tonnes/ha can only be achieved if the crop can access enough nutrients via its roots, and as the plant grows, through foliar applications.

Zinc and magnesium deficiencies are the two most widespread nutritional disorders in maize. Zinc is important for photosynthetic activity. Magnesium is essential for the early establishment of the plant. A deficiency is reflected in reduced crop yield at harvest.

Phosphorus and potash are primary nutrients, however many soils have not got the capacity to deliver an adequate supply. Where phosphate availability is reduced because of soil pH or where its uptake is impaired due to dry soil conditions, foliar phosphate will help. It is translocated from the leaf to the roots very effectively, maintaining root development.

One or more of the above is often deficient in the growing maize plant. This nutritional shortage is particularly important as the plant reaches the 4 to 5 leaf stage as it is now that yield is being set. Maize stressed at this point can result in tall, thin plants, with poor root systems and reduced leaf area. Reduced leaf area captures less light, resulting in lower yields.

To overcome the risk of nutrient deficiency apply foliar nutrients at the 4 to 5 leaf stage. YaraVita MAIZE BOOST is specifically formulated for foliar applications on maize. It will deliver a high concentration of phosphate, zinc, magnesium and potash to maximise maize yield and quality this harvest.

Read more on forage maize nutrition

Purchase quality compound fertiliser - it pays every time

04 April 2020

At this stage, most 1st cut fertiliser applications are completed, but are you confident that your target fertiliser rate was evenly applied? Yara has demonstrated how, over 24 metres, the physical quality of a fertiliser influences the yield and quality of a grass crop.

Yara has looked at this effect by comparing YaraMila Extra Grass (27-5-5+S) with a blended 27-5-5+S. The target rate for both products was 500kg/ha and the spreader settings were changed for each product on testing. The YaraMila product achieved the target rate across the whole bout width; however the application rate for the blended product varied between 400 to 648kg/ha.

We then analysed separately each of the 23 trays from the blended product, to determine the actual NPK+S content. Because the YaraMila product is a compound, we know that the product in each tray contained 27% N, 5% P and 5% K. The blended product had a variation in N across the bout width of between 91kg and 160kg, for P the variation was 10 to 19kg and for the K it was 34 – 59kg/ha. The target was 135kg, 25kg and 25kg for N, P and K respectively. Accounting only for unevenness of the N, in this blend, compared to the YaraMila Extra Grass, there was a yield loss of nearly 400kg/ha of grass dry matter as a result of the poor spreading pattern of the N. This equates to 1.5 tonnes/ha of silage which, based on barley and rapeseed meal, would have a replacement value of £54.

Don’t take the chance, use a quality compound fertiliser

Read more on YaraMila compound fertiliser

Quality grass silage starts with good crop nutrition

12 March 2020

To understand the difference that making good quality grass silage can have on a dairy farm, we can compare the cost of achieving similar levels of milk output by balancing a diet using either a good or poorer quality silage.

My following calculations are based on a 120 cow herd producing 9,000 litre/cow, housed all year round with the forage component split 25% maize and 75% grass silage. A 30 litre cow requires 10.85kg of concentrate to achieve production using poorer silage, where as a cow fed the better silage requires 7.54kg daily. This additional feed saving would translate into £32,000 with a potential additional increase in £13,000 of improved milk yield if cows were fed the better grass silage.

The feed efficiency translated from 0.35kg/litre to 0.24kg/litre between both forages, with a purchased feed cost saving of 3.19ppl using better forage. If we incorporated the forage cost, there would be a 2.43ppl difference between the diets. This difference is less than the purchased feed cost because we are gaining more milk from forage and so must feed more forage per cow.

The first step to making quality silage, is providing the right crop nutrition. If slurry has been applied, the nutrients should be accounted for in this and the balance should be supplied using a quality NPKS compound like YaraMila Silage Booster or if N+S only is required then use a product like YaraBela Nutri Booster.

See our silage fertiliser programmes

Soil phosphorus levels impact greenhouse gas emissions

12 March 2020

The role of soil fertility in mitigating Greenhouse Gas emissions has up to now been based on improving nutrient use efficiency. For example, soils at the correct soil pH can utilise soil phosphorus more efficiently. Microbial breakdown (mineralisation) of organic matter into plant available nutrients is at its highest when soils are at their optimum pH. However, new research seems to show that soil phosphorus levels have a direct effect on soil nitrous oxide (N2O) gas emissions on permanent grassland. N2O is a very potent Greenhouse gas, and hence the importance of this research.

It is thought that certain soil microbial populations that are more dominant in low soil phosphorus situations produce more N2O. With increasing soil phosphorus levels these microbes become less dominant resulting in lower N2O emissions. These low nutrient soils are more fungi dominated, and these fungi lack a particular enzyme which predisposes them to producing more N2O. It is very welcome that this research adds another positive dimension to the existing body of knowledge that supports the key role that soil fertility plays in the future sustainability of grass-based production systems.

With the continuing poor soil conditions, very little fertiliser has been applied. So, for those with no fertiliser in the yard, order your fertiliser now. Don’t wait until field conditions are improved to order. Those that wait, may be faced with delayed deliveries if lots of farmers order at the one time.

Read about planning spring phosphate applications for grass

Nutrient watch – advice for spring fertiliser and slurry applications

14 February 2020

Daily grass growth rates are still low, so not much nitrogen (N) is required at this stage. Only apply if soil temperatures are at 5OC and above. If soil conditions are too wet or frozen, then delay application until they improve. Early fertiliser applications are appropriate on drier soils with productive PRG swards which respond to early N applications and allow early grazing. Depending on livestock demand, apply up to 30 kg/ha (24 units/acre) of N with sulphur as a 1st application for grazing.

There is scope to apply slurry rather than fertiliser N on paddocks with the lowest grass covers. Avoid slurry on heavier covers until after 1st grazing. Remember that ammonia (N) losses from slurry double for every 5OC rise in air temperature. This is why spring applications are encouraged, to reduce ammonia emissions and increase N use efficiency.

Prioritise slurry for paddocks with a potassium index of 0 or 1 (especially ones which had bales removed last year) and silage fields. Reduce the fertiliser N application rates on paddocks that have received slurry. Allow for 6 units/N per 1,000 gallons with splash plate and 9 units/N with trailing shoe. Don’t apply slurry and N fertiliser at the same time, it’s best to leave at least a week between them.

Target paddocks with a phosphorus (P) index of 0 or 1, with a YaraMila compound, such as Stock Booster S (25-5-5+5%S+Se). These colder and wetter spring conditions reduce P availability and can lower grass growth.

Read more information on grassland nutrition

Nutrient watch – spring grassland

07 February 2020

The monthly rainfall data from the Met Office from September to January confirms what we already know: its’ been a very wet autumn and winter. The rainfall for England is 35% above average for the period. However, soil temperatures are running slightly above average which is a help. But what’s the upshot of all this rain? Nitrogen and sulphur are the obvious nutrients that will be affected, but soil phosphorus availability should be considered also.

For a grass sward, 70 - 80% of all root mass down to a depth of 23cm is in the top 7.5cm. Below 23cm root mass drops considerably. In reasonable winters you’d expect that some nitrate and sulphate would remain in this surface root zone, but with over a third more rain having fallen during autumn and winter it’s reasonable to expect that very little nitrate and sulphate remains. This observation in the case of sulphur is supported from data on soil samples received in Yara’s laboratory in Pocklington during December and January.

In saturated fields phosphorus availability will be reduced. These conditions increase the solubility of soil iron and aluminium which in turn affect the availability of soil phosphorus. It’ll be important to get some NPKS fertiliser like YaraMila Stock Booster S (25-5-5+5%S+Se) onto grass fields as soon as conditions allow, to kick-start and maintain grass growth this spring. Remember that with the prevailing soil conditions nitrogen on its own won’t be enough. In drier years a 23% growth response is usual with early sulphur and phosphorus, so be sure to use a compound NPKS fertiliser to get your grass off to the best possible start.

Read about making your fertiliser work harder

Phosphate applications this spring

25 January 2020

Phosphate (P) is a key nutrient for grass. Its role in energy supply, root growth and tillering makes its availability crucial for grass growth in the spring. Although the plant’s requirement for P is small compared to that of nitrogen, its availability is essential.
On grazing farms, a portion of your total annual P requirement should be applied in early spring and have the lion’s share of it applied by the end of April. A fresh P application boosts availability, first in early spring when its natural availability is reduced in wet cold soils, and then in April and May when there is a very high demand for P from peak grass growth.

Typically, the phosphate in fertiliser is 100% water soluble; this however creates its own problems. As soon as you apply water soluble phosphorus to a soil, it becomes slowly fixed by iron and aluminium. The phosphate contained in YaraMila Stock Booster (25-5-5+5% SO3) is a mix of water soluble phosphate and Di-Calcium Phosphate (DCP). This DCP is not fixed by the soil but becomes available when triggered by the weak acids from grass root exudates. This ideal combination of two phosphate fractions, rather than one, results in superior availability of P for grass.

The maintenance requirement for phosphate (P2O5) on grazed swards is 20 kg/ha, however if your grazing platform is growing 15 t of dry matter with 80% utilisation, then your maintenance will be closer to 30 kg/ha.

Read about making your fertiliser work harder

Improving nitrogen use efficiency on livestock farms

10 January 2020

Agricultural nitrogen (N) management remains a key environmental challenge and has implications for water quality, greenhouse gas and ammonia gas emissions. More efficient use of N, has a significant effect on a farmer’s bottom line. Where N is not being recovered by the grass or by the cows and turned into saleable products (milk and meat) this is a financial loss to the farming system. Increasing N efficiency by improving utilisation of N by grass will result in lower losses of N to the air and water. If a farmer can get more production (grass, milk or meat) for the same quantity of N input, or get similar production using less N input, it will lead to higher levels of nutrient efficiency. It could also potentially offset the need for expensive additional feeds or to help increase the total milk or liveweight gain from each hectare.

N fertiliser planning should not just consider the seasonal grass feed demands of the herd, but also the potential of the different soils/fields and swards to utilise applied N inputs over the season for grass production. Improvements in nitrogen use efficiency (NUE) and pasture productivity can be achieved by putting together a nutrient management plan for the year, utilizing manure N sources efficiently, including low emission slurry spreading application methods, using the right N fertiliser type at the right-rate and the right time, improving grazing management, reseeding poorly preforming swards and optimising soil fertility, especially soil pH

Read more about making your fertiliser work harder

Latest grassland video advice

Healthy soils for quality grass

29 November 2019

With over 40% of UK grassland soils deficient in phosphate and potash, and 25% reading below 5.5 for pH, there is potential to make simple corrections to improve grass yield and quality. Awareness of the benefits of improved soil health is driving more farmers to soil test regularly and with a more holistic approach beyond testing for just P, K, Mg and pH. The basics of a soil test are still vitally important, potentially revealing pH and macro nutrient imbalances. When these are addressed they can improve dry matter yields by 50% in some cases.

Without a soil test, applications of nutrients to soils pose not only a risk of environmental pollution, but an unnecessary cost to the farmer. Phosphorous applications to soils at pH 6.0 reduce its availability by almost half. The same effect will occur to nitrogen and potassium applied to soils at pH 5.0. High levels of rainfall this autumn have depleted nutrient reserves and accelerated soil acidification, another reason why a soil test might be timely.

If you are soil sampling, remember that a soil test is required for each field and tests should be no older than 5 years old for the purpose of nutrient management plans. It is worth considering testing soil trace elements, plus cobalt, iodine and selenium, within Yara’s Animal Health Soil test to help identify if the full dietary requirements of livestock are being met from grass.

Read more about soil analysis

It’s time to start thinking soil sampling

01 November 2019

Since April 2019 soil sampling has changed from something we should do, to something that we must do. DEFRA introduced the new rules to help protect water quality in England. They make it necessary to soil test, and then use the soil test to plan and apply fertiliser or manure to improve soil nutrient levels and meet crop needs. These soil test results must not be more than 5 years old.

The rule change is no surprise as regular soil analysis is the key to nutrient management on a farm. Tests provide a reliable guide to assessing soil fertility and provide the basis for sound applications of lime, organic manures and mineral fertiliser. Much of what a soil test allows us to do is to distribute valuable manures within your farm to make the best use of purchased fertiliser.

If you are an intensively stocked grassland farmer, it may be worthwhile to soil test annually. Fertiliser recommendations are not an exact science, hence soil testing more frequently together with measuring grass yields will help you fine tune your nutrient management plan (NMP) for every paddock.

Wait at least 3 months to soil sample after an application of organic manure or mineral P & K. Sample to a depth of between 7 and 10 cm’s on permanent grass leys. A soil test taken every 3 years will cost £1 per ha/year. However, it’s only value for money if you use your soil analysis results to implement a farm NMP

Read more about soil analysis


Interesting findings from Grass YEN 2019

22 November 2019

Grass YEN, the industry-science platform had its end of year meeting back in October. Yara were once again co-sponsors of the event, and I would like to take this opportunity to thank the five farmers that we sponsored for their time and energy in participating in this year’s competition.

At the core of Grass YEN is the accurate measurement of grass yields. It’s a cause for concern and an impediment to progress that so little is known about grass silage yields on UK farms. Most of the farmers who participated in this year’s YEN weighed the grass in a 3 metre length of swath at 5 random locations after mowing.

It would be preferable to weigh all grass over a weigh bridge, but not many farms have this luxury. ADAS & John Deere this year carried out a trial to test the relative accuracy of a number of different methods. They compared these methods to a whole field yield weight from trailers run over a weigh bridge. The swath method was shown to be accurate when it was compared to a whole field weight using trailers and a weigh bridge.

It’s important that we continue to build on the data that has been gathered from the last two years of Grass YEN, as this collaborative approach between farmers, industry and research is capable of delivering a cost effective improvement in grass silage management.

If you would like to participate in Grass YEN for 2020, please get in touch with us via email, facebook or twitter

Read more about grassland nutrition


Managing winter grazing

14 November 2019

Good management of grazing from autumn through into early spring can increase the quality of first cut silage.

Managing winter grass residuals can increase first cut D-value 

If producing high D-value silage is the objective on farm, then good grazing management this winter and spring has an important role to play. Good grazing conditions have allowed fields to be grazed to the desired residual, without causing too much damage to the sward.
Grazing down to a residual of 5cm from late autumn into early spring – is the key to ensuring that re-growth is of a high D-value. Longer residuals can lead to dead vegetation accumulating and therefore the quality of the sward will be reduced significantly.

Although weather conditions are favourable at the moment, if soil conditions deteriorate and livestock begin poaching then they should be removed or this will also affect 1st cut yields and quality. Weather conditions can make grazing difficult and the desirable height a challenging target to hit during early spring. It might be an option to graze fields now that are intended for 1st cut silage.

Research has shown that fields un-grazed from late autumn into early spring will produce lower D-value silage compared to those that were grazed. Un-grazed fields during this period that are harvested for silage in late May will have an estimated D-value that is on average 7% lower than if they were grazed.

However, there was no difference in silage D-value if grass was grazed in late autumn/winter versus early spring and harvested in late May. The quality of silage also depends on harvest date, growth stage at harvest and fertilisation.

Read more about grassland nutrition