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.

Latest grassland video advice

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

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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.

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

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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.

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Nitrogen: to spread or not to spread?

13 September 2019

Spreading nitrogen (N) from now on should be considered carefully.

The growth response will have to justify the cost.  As we approach winter, excess or unused soil nitrate is something we want to minimise as it constitutes a risk to water quality. NVZ rules on grassland allow for up to 80 kg/ha of mineral nitrogen to be applied between the 15th of September and the 31st of October, with 40 kg/ha of N the maximum allowed in any one application.

Preferably N applications should take place earlier, at a time when grass growth is sufficient to utilise it. Teagasc research on autumn applied N has shown that 30 kg/ha of N applied on 1st August, 1st September and 1st October gave a grass dry matter (DM) response of 27 kg’s, 19 kg’s and 10 kg’s respectively for each kg of N applied. If we assume that this grass DM contains 3% N, then our apparent N recovery rate was 80% for August, dropping to 30% for October.

It’s important that any N applications take into account the requirement for grass, sward quality and soil and weather conditions as grass grown needs to be utilised. A paddock by paddock choice should be made on the rate of N. Drier paddocks receiving more, heavier soil types receiving less. N application rates in my opinion should not exceed 30 kg/ha and be applied no later than mid-October.

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More grassland agronomy advice

The latest grassland fertilser and nutrition advice from the Yara agronomists.

Fertilising short term leys and brassicas

24 August 2019

Fertilising these crops adequately is necessary to obtain the maximum yields they are capable of producing. In general these crops are being sown after a cereal crop, therefore the soil nitrogen supply is likely to be low.
For temporary leys following cereals, we recommend up to 50 kg/ha of nitrogen, phosphate and potash for establishment. The phosphate in particular is important for root development and tillering. YaraMila Actyva S (16-6.6-12.4 + 2.6% S) will provide a consistent and reliable supply of phosphate for the remainder of the growing period.

Remember that for every 1cm of grass growth the N requirement is 7.5 kg/ha. We would expect Italian ryegrass or Westerwolds to grow to a minimum height of 10 cm by the end of October, therefore requiring 75 kg of N. If we apply 50 kg of N from the bag, there will be enough soil residual N to provide the remaining.

The hybrid brassicas such as Redstart and Interval may still be drilled into late August and they have similar nutrient requirements to that of forage rape and stubble turnips. We recommend up to 80 kg of nitrogen, 25 kg of phosphate, 50 kg of potassium and 30 kg of sulphur per hectare. A perfect fit for these nutrient requirements is YaraMila Silage Booster (20-2-12 + 3% S+ Se).

It’s important to get these crops off to a good start, so placing the fertiliser in the seedbed will help to establish strong healthy plants.

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Grow grass now to extend your autumn grazing

02 August 2019

From mid-September daily grass growth will fall rapidly. After this point grass can quickly run out and either livestock performance declines or they will require housing to maintain performance. If we start to manage grass now, we can grow more grass over the coming weeks. This then allows us to build up a bank of grass for extending the grazing period and, if correctly managed, allows for earlier turnout of livestock in the spring.

Grass grown now will remain leafy, albeit not as good as leafy grass grown earlier in the year.  It will not require the same level of purchased feed to maintain a certain level of milk yield, or daily liveweight gain, compared to feeding poorer quality forage indoors or set stocked grazing where there is poorer quality grass with lots of dead material at the base.

If we optimise grass growth over the coming weeks by applying nitrogen and sulphur now and operating a rotational grazing system (even if it’s temporary fencing) then we can save money and shorten the indoor period. This means that livestock will need to graze an area and then be moved onto a fresh area every 1-4 days, allowing the sward to recover and start growing again. The drier or ‘earlier’ parts of the farm should be grazed from mid-September and then closed off as the regrowth on these parts can be carried over the winter months for grazing first in the spring.

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Successful reseeding this autumn

22 July 2019

A new perennial ryegrass (PRG) sward can often be the most challenging crop to establish on a grassland farm. The main benefits of a new PRG sward are improved dry matter (DM) yield, and improved nutrient use efficiency.

Step 1 : identify poorly performing paddocks.

Step 2 : assess their perennial ryegrass content. If this is less than 60% consider re-seeding as annual meadow grass and other weed grasses produce lower yields, poorer feed quality and do not respond well to applied nutrients.

Take a soil test beforehand so that action can be taken to correct soil pH. 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 list and pick those that suit your particular farm and system, with a small range in heading dates. Failure to provide new PGR swards with the correct nutrients at sowing will hinder the success of the ley. Using a quality NPKS compound fertilizer such as YaraMila ACTYVA S (16-6.6-12.4 + 2.6% S), will support the new plant, especially its phosphorus and nitrogen requirements which are critical for establishment.

Applying herbicide to control weeds 4 to 6 weeks post-emergence will prevent weeds from competing for nutrients and space. This combined with a light grazing when grass height is at 8 – 10 cm will promote new shoots and thus the long term productivity of your new sward.

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Don’t be complacent – build forage reserves while you still can

05 July 2019

With reports of good crops of 1st and 2nd cuts being taken, it seems like it’s been a good grass year. Compared to last year, it’s a great year but if you look at the GrassCheck GB average growth figure for the year-to-date we’re marginally below the long-term average at 6.02 t DM/ha.

On intensive grazing farms, pushing grass growth is still key and maintaining residuals of 4 cm. Heavy covers of > 1,500 kg should be cut as surplus bales and maintain grass growth by keeping N + S applications up-to-date whilst growing conditions are still favourable. Slurry should be applied (by low emission spreading equipment to reduce ammonia emissions) where silage/surplus bales are taken off. If slurry is not available, then apply a NPKS or NKS quality compound fertiliser such as YaraMila SILAGE BOOSTER or YaraMila ZERO P CUT to replace P and high K off-take from taking surplus bales.

It’s prudent to check silage stocks now and unless you’ve a comfortable surplus for the winter, consider adding to these stocks with 3rd cuts. If the silage area is going back to grazing, fresh N + S applications will speed up aftermath growth. Growing a surplus of grass now on silage aftermaths, is sensible as it might save silage being introduced to buffer grazed grass in August if it turns dry.

Take advantage of the favourable weather conditions to build forage stocks, because knowing how unpredictable our weather is now; you could have to feed it in August!

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