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.

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

Latest grassland video advice

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

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

Silage mineral analysis - what does it all mean?

14 October 2019

Silage mineral testing is usually carried out to calculate livestock mineral supplementation rates. However, tests can also help review how well your silage crop was fertilised. A simple interpretation of your mineral analysis may shine a light on a particular problem, such as poor yields or low silage protein. The results quoted on these mineral analysis will be in elemental form and on a dry matter basis.

Nitrogen (N) – Disappointing grass yields combined with a low N % (and protein %) on the report, even though the grass was cut with high to medium proportion of leaf to stem, could be symptomatic of sub-optimal N applications. This is not surprising since N is required to facilitate growth through chlorophyll production and build plant proteins.

Sulphur (S) – Your silage should have an S % of more than 0.25 %, and an N:S ratio of between 10:1 and 13:1. The N:S ratio is calculated by dividing the N % by the S%. S is associated with plant N uptake and is a building block of plant proteins. Any deficiency is usually not noticeable in the grass before harvest but low yields and lower proteins levels are associated with low sulphur. The essential amino acids cysteine and methionine are usually low in S deficient grass.

Potassium (K) – Low K % (< 2 %) in silage might indicate that the crop didn’t receive enough K. Low grass yields and poor responses to N can often be associated with poor K crop nutrition. Soil test if you haven’t done so and apply K as per recommendations (RB 209).

Phosphorus (P) – Low P % (< 0.25 %) could indicate that the crop did not receive adequate soil phosphorus supply. This can be prevalent in 1st cut silages, as rapid growth in combination with cold and/or wet soils can reduce the availability of soil phosphorus during this period of growth. Soil test and apply P as per recommendations (RB 209). There is evidence from AFBI in Northern Ireland, that highly productive swards can experience a P deficiency if grown at the lower range of soil P index 2. Hence, keeping these soils at the upper range (21-25 mg/l) of index 2 for P may be preferable.

Selenium (Se) – If you haven’t used a Se fortified fertiliser, then it’s most likely that your silage will be very low in Se. Typical Se levels in silage are less than 0.07 ppm (<0.7 mg/kg). At these levels, there is not enough Se in this silage to meet the demands of cattle and sheep. By using a Se fortified fertiliser next season, you can simply remedy the problem.

Regular testing and analysis are essential to get the best from your silage crop

Read more about grassland nutrition

More effective weed control on autumn reseeds

26 September 2019

When getting the sprayer out to control grassland weeds on autumn reseeds, there is an opportunity to add a foliar fertiliser for two reasons.

  1. The effectiveness of herbicides on autumn reseeds can be improved if a foliar fertiliser is tank mixed with the herbicide. The foliar fertiliser works by stimulating the weeds to grow more actively, which results in more of the active ingredient being taken up by the weeds.
  2. Spraying reseeds with herbicide can knock the young grass plant back, especially in late autumn when growing conditions are not ideal. The use of a foliar fertiliser with the herbicide helps the grass plant cope better with the stress of being sprayed. Grass which is supplied with a full complement of nutrients at the onset of an environmental stress is more resilient. The improved growth of grass seedlings will help fill in bear patches, reducing light and space for any new germinating weeds.

We recommend YaraVita Croplift Pro at a rate of 2.5 kg/ha or 1 kg/acre in conjunction with your grass herbicide. It contains a full complement of nutrients to ensure the long-term success of your new ley. YaraVita Croplift Pro can be safely tank mixed with almost all common grassland herbicides, if in doubt ask your supplier about compatibility.

Read more about grassland nutrition