Keep up to date with all the latest grassland agronomy advice with this regular column from Yara's chief grassland agronomist Philip Cosgrave.
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.
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
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.
The latest grassland fertilser and nutrition advice from the Yara agronomists.
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
When getting the sprayer out to control grassland weeds on autumn reseeds, there is an opportunity to add a foliar fertiliser for two reasons.
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.
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.
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 (16-15-15 + 6.5% SO3) 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 (20-4.5-14.5 + 7.5% SO3 + 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.
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.
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 (16-15-15 + 6.5% SO3), 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.
Against a background of great change, it is even more important to take control where we can to deliver impressive results, whatever the weather or the politics!
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 > 3,000 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 NK SULPHUR 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!
Grass growth has been good, with yields ahead of target in most areas. Where 1st cuts were taken early, 2nd cuts will be about to be in the clamp, if not there already. 1st cuts were very heavy, but recovered quickly and are taking advantage of the current good growing conditions. Whether it’s for grazing or silage, it’s beneficial at this point to reconcile grass offtake with nutrient inputs. This will optimise grass growth over the coming months and prevent soil fertility from slipping further where P & K indices are 2- or lower.
If you know good indices and a good soil pH exist for your fields or paddocks then you have some leeway. However with good yields comes higher offtakes so there are no free lunches to be had when it comes to soil fertility.
Maintenance dressings of P & K are most easily applied as an NPKS compound. This ensures the nutrients are evenly applied. Compounds such as YaraMila EXTRAGRASS (27-5-5 + 6% SO3) or YaraMila STOCK BOOSTER S (25-5-5 + 5% SO3 + Selenium) have 10 times more phosphate landing sites than a similar blended product. Three dressings of either of the products above at 130 kg/ha per application is sufficient to deliver the maintenance requirements of phosphate for grazing.
Grazed grass quality has a direct impact on profitability, and those farmers who are actively managing their grassland will understand how maintaining grass quality during the month of June pays dividends.
Grazing management in June is a fine balance between grass quantity and quality, and cow performance. Trying to graze down to 4cm after poor residuals in the previous rotation is a real problem. We also have to contend with grasses heading out, which can often be compounded by nutrient stress.
Some farmers are using pre-mowing as a means to manage this period and maintain grass quality. Pre-mowing can help grazing management but should not be seen as a replacement. It is most commonly used to put paddocks ‘back on track’ where high residuals are carried over from the previous rotation. It’s difficult in this scenario to have cows graze around dung and urine patches, therefore pre-mowing is beneficial.
It is important to remember that pre-mowing when grass supply is tight or very dry, will lead to a faster rotation and consequently drop the average farm cover and increase the feed deficit.
Grass covers that are 200-300kg DM/ha higher than the optimum can be mowed to counteract losses and increase cow intakes. Mow no more than 2.5pc of the farm on any one day, so that it will require at least two grazing rotations to mow the whole farm. Finally, it's essential to mow tight to achieve the desired post-grazing residual of 4 cm’s.
Selenium (Se) and phosphorus (P) both play a fundamental role in cow reproductive health. Yara Analytical Services data shows that 99% of grass samples received in 2018 were Se deficient and 39% were P deficient. A dietary deficiency in Se is associated with cystic ovaries, anoestrus and early embryo death. While P deficiency results in irregular oestrus, silent heats and low conception rates. Cows not going back in calf is the single most common reason for culling in dairy herds according to the 2018 Kingshay dairy report.
A lactating cow requires daily P and Se intakes of 4 g and 0.3 mg respectively for every kg of dry matter (DM) intake. We can increase the P content in grass and maintain the levels in the soil by applying fresh P in small, but frequent, applications from spring onwards. These fresh applications will raise grass P levels to 4 g/kg DM and will contribute to the 20 kg/ha annually needed to replace grazing offtakes.
Increasing grass Se levels to the desired 0.3 mg/kg DM is simply and safely possible by applying a quality selenium-fortified fertilizer like YaraMila YaraMila STOCK BOOSTER S (25-5-5 + 5 % SO3 + Se) from early spring onwards. Because this product is a true uniform compound, each granule contains P and Se, which guarantees every bite of grass contains an adequate supply of these nutrients for your cows. By fortifying grass we’re not relying on other forms of Se supplementation, this gives us the flexibility to cut back on concentrate feed without jeopardising Se intakes.
Heavy crops of 1st cut are being taken currently, especially from fields which were not grazed in the spring. Four of Yara’s six Grass YEN participating farmers have taken their 1st cuts at this stage and by all reports, yields are very good.
Early May cut 1st cuts have greened up nicely and N applications for 2nd cut silage will depend on an estimated cutting date. Allow 2.5 kg/day (2 units/day) as a rule of thumb for N requirement, and account for available N in slurry. The book value for N in 6% DM cattle slurry is 2.6 kg/m3, with 20 – 30 % of this available for your 2nd cut. To convert kg/m3 into units per 1,000 gallons multiply by 9.
Heavy 1st cuts at this time of May, could easily be removing 5 tonnes/ha or more of DM, this equates to 165 kg/ha of K2O so 2nd cut fertiliser applications of YaraMila Silage Booster or YaraMila Sulphur Cut will deliver extra K which will replenish soil K if slurry is limited. 2nd cuts are not effected by luxury K uptake to the same degree as 1st cuts.
Grass P levels normally drop at this time of the year, which coincides with a period in the year where farmers are breeding cows and P is a key nutrient in cow fertility. Dairy cows need ~ 4 grams of P (elemental) per kg of intake. Small frequent applications of YaraMila Extragrass or YaraMila Stockbooster S will combat this and go a long way to maintaining soil P levels. RB209 recommends 20 kg/ha of P for maintenance. Herds pushing on greater than 10 tonnes of grazed grass being utilised and not feeding high levels of concentrates will require more than this to maintain soil P levels.
Just because your maize crop is now planted don’t forget about its nutritional needs. Maize has a high demand for nutrients, because of its high yields. 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 deficiency affects the early establishment of the plant which is reflected in reduced crop yield at harvest. Phosphorus and potash are major nutrients, however many soils have not got the capacity to deliver an adequate supply. Commonly, phosphate availability is reduced because of soil pH.
One or more of these nutrients is often deficient in the growing maize plant and this is particularly important as the plant reaches the 4 to 5 leaf stage. It’s at this stage that yield is being set. Maize stressed at this point can result in tall, thin plants, with poor root systems and reduced leaf area. This reduced leaf area captures less light, resulting in lower yields.
We can overcome this risk of a reduced yield through nutrient deficiency by applying foliar nutrients, at leaf stage 4 to 5. On dry soils where phosphate uptake might be impaired, foliar phosphate is translocated from the leaf, to the roots very effectively, maintaining root development.
YaraVita Maize Boost is specifically formulated for foliar applications on maize, to deliver a high concentration of phosphate, zinc, magnesium and potash to maximise yield and quality this harvest.
Zero-grazing is being employed on many dairy farms across the UK as an alternative or supplementary practice to grazing and silage based milk production systems. Increasing herd sizes and the need to reduce feed costs by producing more milk from forage is driving farmers to new ways of utilising grass. It offers farmers greater flexibility, especially those with limited grazing capacity around the milking parlour. It is more labour intensive, but it is an option worth considering.
Research at AFBI in Northern Ireland points to improved cow performance from zero-grazed grass compared to grazed or silage fed systems. These zero-grazed fed cows also maintained heavier live weights over the course of the study. What determines the success of any of these systems is grass/silage utilisation per hectare. Margin over feed costs per hectare was greatest (£3,580) for the zero-grazed cow group, while the silage fed group came out slightly below this, and the grazing group was even lower. The reason for this was the higher stocking rates of the indoor groups which more than compensated for the lower per cow feed costs attributed to the grazing group.
The performance above was achieved by zero-grazing quality grass. Harvesting covers of not greater than 3,500kg DM/ha is preferable to reach these performance levels in zero-grazed herds. Harvesting grass at pre-harvest covers of 4,500kg DM/ha rather than 3,500kg DM/ha led to a decrease in cow performance and grass growth, estimated at £0.57 cow/day. Zero-grazing is a viable alternative but only with excellent grassland management.
In a recent AHDB dairy publication, the practice of blanket spreading the entire grazing platform at the one time with Nitrogen was discussed. It’s a labour saving practice, which suits contractors mostly, but can also free up time for the farmer. It’s not practical to spread nitrogen every day or second day, but there are consequences to only spreading once every month or every three weeks.
A sward will recover quicker after grazing or cutting when fresh nitrogen has been applied. The bulk of this freshly applied nitrogen is then taken up by the plant, over the following 21 days. Nitrate concentration in the grass peaks in the first two weeks as the plant needs this nitrate for photosynthesis and protein synthesis. Nitrate levels then begin to drop gradually in week 3 as growth surges. This is due to greater light interception by the expanding leaf canopy which dilutes the nitrate levels within the plant. It’s for the same reasons that we don’t apply nitrogen for our 2nd cut silage the week before the 1st cut is harvested.
Cows that graze paddocks which have just received nitrogen applications in the previous week, will be using up more valuable energy on removing this nitrate from the grass as urine. This is counter-productive as energy is the limiting nutrient on predominantly grass based diets. By increasing urine nitrogen, we’re increasing nitrogen losses to the atmosphere as ammonia. We have to strike a balance, and spreading nitrogen once a week on the paddocks grazed in the previous 7 days works well.
At this stage, most 1st cut fertiliser applications are complete, but are you confident that your target fertiliser rate was evenly applied?
Yara has demonstrated over a 24 metre bout width how the physical quality of a fertiliser influences the yield and quality of a grass crop.
Yara compared YaraMila Extragrass (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 entire bout width; however the application rate for the blended product varied hugely, from 400 to 648kg/ha.
Each of the 23 trays from the blended product were analysed individually to determine their 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 target per nutrient was 135kg, 25kg and 25kg for N, P and K respectively. 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 K it was 34 to 59kg/ha.
Due to the poor spreading pattern of N in this blend, and when compared to the accuracy of YaraMila Extragrass, there was a yield loss of nearly 400kg/ha of grass dry matter. This equates to 1.5 tonnes/ha of silage which would have a current replacement value based on barley and rapeseed meal of £60.
This shows the importance of a quality compound fertiliser where you can be confident of an accurate nutrient application across the entire field.
Calculating the return from using sulphur to grow forage crops is not straightforward, and it’s important that the way we calculate it is transparent, fair and easily understood.
Yara calculates the value of forages, such as grazed grass or silage on their replacement cost, relative to purchased rapeseed meal and barley. Many other companies value forage based on the value of the extra milk or meat produced. This assumes that a litre of milk requires 5.4 MJ ME and a kilo of liveweight gain requires 45-50 MJ ME. We feel this approach does not give the farmer a fair appraisal.
If we apply sulphur on 1st cuts this year using a product such as YaraBela AXAN (27% N + 9% SO3), we are likely to increase dry matter (DM) yields by 20% per ha or 1 tonne of DM. The cost of the sulphur is £15/ha. We assume an utilisation of 80%, the silage is 25% DM and has an ME of 11 MJ/kgDM and protein is 14%. Rapeseed meal is costing £198/tonne and barley £132/tonne. Using the above figures, we can calculate how much this 0.8 tonne (80% of 1 tonne) of extra 1st cut is worth, relative to Rapeseed meal as the protein source and Barley as the energy source.
The value of this extra 0.8 tonne of grass silage is £111. The cost to grow it is £15. This equates to a return of £7.50 for every £1 spent on sulphur using YaraBela AXAN on 1st cuts this spring.
Over the last two weeks I’ve been asked by a number of farmers what effect has fertiliser quality on grass yields and quality. Essentially what we are concerned with is the uneven application of nutrients across the spreader bout width and its effect on yield and quality. The coefficient of variation (CV%) is a term used to describe this unevenness, a CV of <10% is considered very good and a CV of >20% is a problem. Work in New Zealand on phosphate applications found that grass yield losses trebled, as the CV increased from 20 to 30%.
We must distinguish between the uneven application of the product and the uneven application of individual nutrients. With true uniform compounds, like YaraMila the granules or prills are uniform and each contains the same analysis as the product. With blended fertilisers, there can be up to 4 individual components making up the NPKS. Therefore, you have 4 different materials with each possibly having a different spreading pattern. When carrying out a tray test on a blended fertiliser you also need to focus on the evenness of spread of each individual component.
Pay particular attention to the evenness of spread of the phosphate component in a blend. If we take a blended 25-5-5 product being applied at 225kg/ha and compare this to a quality compound, there are 50 phosphate landing sites per m2 with the blend and 500 with the compound. The aim is that each of the 400-500 grass plants/m2 in a sward has access to fresh phosphate in spring to optimise growth.
High yielding grass crops have a high requirement for potassium (K). The majority is required for the essential role of maintaining water balance within plant cells. Since grass is made up of 80% water, the availability of soil potassium is key to optimal grass growth.
Within the grass plant potassium is found in similar levels to nitrogen and it helps improve both the uptake of nitrogen from the soil, and the conversion of nitrogen to protein within the plant. During peak grass growth in early May, daily K2O uptake can be as high as 4-5kg/ha.
The K in grazed grass is efficiently recycled by livestock, however silage crops remove 10 times more K from a sward than grazing. This means for every 1 tonne of grass dry mater eaten or harvested, grazing removes 3.6 kg and silage 36 kg. A 1st cut yielding 5 t/DM/ha will remove 180 kg of K, and it is because of these large removal rates that soil K indices must be carefully monitored as they can decline quickly over 2 or 3 years.
Mineral K will be required each year if organic manures are not being imported onto the farm as K is not recycled with 100% efficiency. Milk and livestock remove K and in addition a small portion will be leached from the soil. Slurry/FYM should be targeted to areas where silage has been taken from and application rates should be proportionate to silage yields.
This spring we should not overlook the potential of fortifying grass for grazing or for silage with selenium (Se). Data from Yara analytical services shows more than 90% of grass and grass silage samples tested are deficient in selenuim. Increasing the Se levels in grass can significantly reduce health problems in your livestock. Using a fortified fertiliser ensures that grass or silage has Se levels which meet the animal’s requirements of 0.2-0.3 mg/kg DM.
We might believe that using fertiliser fortified with Se, such as YaraMila STOCK BOOSTER S (25-5-5 + 5 % SO3 + Se), is only useful for grazing livestock but this is not the case. If grass silage is fertilized using our YaraMila SILAGE BOOSTER (20-4.5-14.5 + 7.5% SO3 + Se), this silage will have enough Se to meet the needs of ewes and cows. Livestock utilise the Se in grass and silage more efficiently than the Se found in boluses, licks and TMR mineral mixes.
Whether it’s a lactating ewe or cow, there is an increased demand for Se because of milk production. It’s therefore important to maintain Se intakes in this spring period when lactating livestock go out to grass to avoid high cell counts, increased rates of mastitis and poor reproductive performance. Yara use sodium selenate to fortify their Booster range of fertilisers. Sodium selenate is used as it’s taken up by the grass more efficiently, upon application. Unlike blended fertilisers, the Booster range of fertilisers contain Se in every granule, ensuring the same levels of Se in every bite.
Sulphur deficiency is now widespread across Northern Ireland. AFBI research has shown that dry matter yield losses of 30% are now occurring at 1st cut or 1st grazing as a result of sulphur deficiency. Lower protein levels in grass and silage are another consequence of sulphur deficiency, as sulphur plays an integral part in protein synthesis. The protein content of grass declines, and this not only reduces its value as a protein source for ruminants, it also hampers its ability to accumulate sugars and thus impairs its fermentation quality when ensiled. A shortage of sulphur in herbage (<0.2% S in DM) can also reduce the digestibility of forages. Rumen microbes require both nitrogen and sulphur to produce their own protein, and a shortage of S will therefore curtail important metabolic functions.
Sulphur deficiency can occur in spring on all soil types, regardless of whether or not slurry has been applied. The availability of slurry-S for spring grass is highly variable and often low, largely because variable amounts of sulphate (the plant available form) are converted into sulphide (a potential plant toxin) under anaerobic slurry storage conditions.
We should manage sulphur applications the same as N applications. If we apply all our sulphur in one application then we risk losing it to leaching. S leaching is wasteful but also very acidifying to soils. The ‘little and often’ approach to S applications does not have negative effects that ‘once off’ applications have. Similar to efficient nitrogen management, we apply the right amount of S as and when the plant requires it.
YaraVera Amidas is a urea based nitrogen (N) and sulphur (S) granular compound fertiliser from Yara, with 40% N and 14% SO3. Because it contains urea it’s well suited to spring use, delivering a stable and sustained supply of nitrogen in the weeks following application. 100% of the sulphur in Amidas is in the plant available form, unlike the S in organic manures. Therefore, you can rely on Amidas to provide a constant supply of sulphur over this critical spring period.
YaraVera Amidas has lower ammonia emissions than straight urea. The sulphur has an inhibitory effect on ammonia production during the conversion of urea to ammonium-N which is due to the Amidas granule containing both urea and S. This effect is not seen with blended urea and ammonium sulphate (AS) products. Because there is less ammonia lost, there is more N available for the crop to support grass growth, the S component has the double effect of reducing N losses while meeting the grass crops requirement for S to support higher grass yields.
Phosphate (P) is a key nutrient for grass, and its role in energy supply, root growth and tillering makes its availability crucial for grass growth in the spring. The plants requirement for P is small when compared to nitrogen but 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 April. A fresh P application boosts availability at a time when its natural availability is reduced by low soil temperatures in early spring and then by April and May, when grass growth is peaking, there is a very high demand for P.
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, this soluble phosphorus becomes slowly fixed by iron and aluminium. The phosphate contained in YaraMila NPK’s such as YaraMila Actyva S (16:15:15 + 6.5% SO3), is a mix of water soluble phosphate and Di-Calcium Phosphate (DCP). This DCP is not fixed by the soil but becomes available as it is triggered by weak acids from grass root exudates. This ideal combination of two phosphate fractions rather than one results in superior availability of P during the spring.
The recommended (RB 209) 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.
After a challenging year and depleted forage stocks, early grass growth has never been more important. So it is crucial to get the timing of your first fertiliser dressing correct. Research by Teagasc, Moorepark on early spring applications of nitrogen (N) demonstrated that there was a return of at least 10 kg DM per kg N applied and a first dressing applied late, can delay grass growth by up to 3 weeks.
Why is this early fertiliser critical? As day length and soil temperatures begin to increase in spring, the grass plant is at its lowest ebb in terms of energy. It needs nitrogen to trap sunlight and therefore grow, if we supply nitrate that’s easily taken up by the root system then photosynthesis and grass growth will begin earlier.
The other problem to address is sulphur lost over the winter period through leaching. We know sulphur availability is crucial for nitrogen to work effectively so by applying nitrogen and sulphur together we will see a boost in grass growth.
On intensively stocked grazing farms a first dressing of 160-120 kg/ha of YaraBela Nutri Booster (25% N, 5% SO3 and selenium) is the ideal choice because it contains nitrate nitrogen, sulphate (rather than elemental sulphur) and sodium selenate. The nitrate and sulphate can be immediately taken up by the roots, and this will kick start grass growth while the sodium selenate in every granule will provide selenium in every bite of grass for healthier livestock.
This spring was unusually late, however should we be surprised with the way the weather has been! According to the Met office we are experiencing more of these extremes. Whether you believe that these changes are a result of humankind’s efforts or not, we will have to factor in these weather events on how we manage our farms.
A prime example of this would be this year’s trial results on 1st cut silage from the south-west of England. It is apparent how a simple fertiliser choice could mean entering the winter period with just enough forage or face buying some to meet a shortfall. Because of the late spring, depending on your soil type and location, 1st cut fertiliser applications were not applied until the end of April or early May.
The result of the trial highlighted how urea was the wrong choice this year. The slurry + urea plots yielded an average of 3.44 tonnes/ha of dry matter, whilst the slurry + YaraBela AXAN (27% N + 9% SO3) plots yielded an average of 5.76t. There must have been significant nitrogen loss in the few days after urea was applied.
We can demonstrate the differences between fertilisers in a trial, but on farm we don’t have the luxury of comparisons as usually the products are bought in advance with no thought on what the spring might bring. When purchasing fertiliser for your 1st cut, remember sulphur and ammonium nitrate will deliver heavier crops.
On attending the end of year meeting for the inaugural Yield Enhancement Network (YEN) for grass, it became apparent that the potential of grass as a crop is well and truly underestimated. The aim of this network is to close the gap between current yields and potential yields for grass silage crops.
Each farmer received a detailed report on each field entered in the competition. This includes the potential yield and what percentage of the potential yield was achieved. The average for all 1st cut entries was 66% of the potential yield, with the highest achieving 110%, this translated into an impressive crop of over 20 tonnes of DM per ha from a grass clover ley which was harvested in the first week of June. The average DM yield for 1st cuts was 6.8 t/ha and for 2nd cuts 4.8 t/ha.
The potential yield model calculates a theoretical maximum based on the information provided by the farmer for the field entered and that crop capturing more than 90% of total light energy and 75% of the available water to a rooting depth of 1.5 m over the growing period. The model will require further refinement as the factors that underpin yield are better understood.
It is widely accepted that grass leys on many farms are underperforming, probably as a result of the lack of information on performance. Any effort, such as Grass YEN which endeavours to capture information on grass silage leys in the common interest of increasing forage productivity must be welcomed.
The interest this autumn in short term leys and brassicas is phenomenal but hardly surprising as farmers do whatever they can to fill a forage shortfall caused by a late spring and an extended drought. It’s important for these crops to ‘hit the ground running’ to make best use of the growing days available to these crops.
Fertilising these crops adequately is necessary to obtain the yields they are capable of producing. In general these crops are being sown after a cereal crop and therefore the soil nitrogen supply is likely to be low.
With temporary leys following cereals we recommend up to 50 kg/ha of nitrogen, 50 kg/ha of phosphate (P2O5) and 50 kg/ha of potassium (K2O) applied at drilling. The phosphate in particular is important for root development and tillering. YaraMila Actyva S (16-15-15 + 6.5% SO3) contains ‘P-Extend’ which will provide a consistent and reliable supply of phosphate for the remainder of the growing period. Not forgetting that these fast growing grass leys have a requirement for sulphur which is often forgotten.
Remember that the N requirement for every 1cm of grass growth 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 which will require 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/ha of nitrogen, 25 kg/ha of phosphate (P2O5), 50 kg/ha of potassium (K2O) and 30 kg/ha of sulphur (SO3). A perfect fit for these nutrient requirements is YaraMila Silage Booster (20-4.5-14.5 + 7.5% SO3 + Se) with ‘P-Extend’.
Preferably on these short term leys and brassicas, the fertiliser should be incorporated into the seedbed and not broadcast afterwards. If the option exists when drilling the brassicas to use a drill which will combine the fertiliser application also then this would be advantageous for the quick establishment of the seedling.