Grassland advice blog

Fertilising aftermaths to boost grass supply

The importance of aftermath grass will vary on farms, with a whole range of factors affecting how much grazed grass will be required after the last silage cut is taken. There are two considerations to address when fertilising these aftermaths. Ensuring that the phosphate (P) and potash (K) requirements of the previous silage crops have been met and supplying enough nitrogen (N) and sulphur (S) to grow enough aftermath grass to meet livestock demand.

Unless soil P & K fertility is maintained at current levels on silage fields then it is likely that next year’s silage yields will suffer. On most farms, the N rate remains constant for silage crops from year-to-year, but with deteriorating soil P & K fertility you end up with less grass for every kg of N applied. Calculate what the offtakes and inputs are to see if P & K needs topping up. Use a suitable quality true uniform compound fertiliser, such as YaraMila NK Sulphur (YaraMila Zero P cut), YaraMila Silage Booster or YaraMila ExtraGrass.

The N requirement of aftermaths will depend on grass demand. Where there is high demand, then apply up to 35 kg/ha of N per application in August and September. If P & K are not needed, then use YaraBela Nutri Booster at 140 kg/ha and if they are needed use one of the YaraMila compounds mentioned in the previous paragraph at a N rate of up to 35 kg/ha. It’s important to apply this fertiliser on as soon as possible, to get grass off to a good start.  

4 Steps to successful Autumn reseeding

A new reseed can often be the most challenging crop to establish on grassland farms. The main benefits of new swards are improved dry matter (DM) yield, and improved nutrient use efficiency. Reseeding in the Autumn has always been more popular with farmers, but it’s important not to leave them too late to establish as it can make managing them for weeds and grazing more difficult. Here are our 4 key steps to success.

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% of area covered in weeds.

Before you start, be sure to complete Step 3: take a soil test and act on the results. 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 farm.

Step 4: Provide new swards with the correct nutrients at sowing. Failure to do so will hinder establishment. Slurry can be used to provide part or all the nutrient requirements. With good soil fertility (P & K index is 2), then the P₂O₅ & K₂O requirement is 50kg/ha for both. If clover or other legumes are not part of the mixture, then an application of 20-30kg/ha of N can be applied to aid establishment. New leys have a greater requirement for phosphate to help with root development. Good seed soil contact is essential, so roll after sowing.

My Top Tips: Weeks 4-6 (post-emergence) apply herbicide to prevent weeds competing for nutrients and space. Combine this with a light grazing when grass height is at 8 – 10 cm to promote new shoots, and thus the long-term productivity of your new sward.

Keeping up grass supply during May and June with YaraMila ExtraGrass

Grazing conditions have certainly been a challenge this season, and unlike this time last year, we’re looking for the rain to stop. Thankfully, for beef and sheep farmers the outlook looks more promising this year with livestock values up on last year, and a return of nearer to normal fertiliser prices. There is a worry though that the significant drop seen in phosphorus and potash fertiliser applications last year, disproportionately affects beef and sheep farms, which does not bode well for forage production on these farms if not rectified.

From a nitrogen (N) perspective, it’s important to note that for farmers who did cut N fertiliser applications last year, doing so again this year will hit grass growth even harder this year as soil N supply is run down from 2022. Where phosphorus (P) & potash (K) offtakes from grazing and silage were not met from fertiliser or manures last year, then soil P & K fertility will have declined. With lower P & K fertility comes a lower N response!

Applying a quality NPKS fertiliser like YaraMila ExtraGrass (27-2.2-4.2+2.4%S) at a rate of 125 kg/ha in May and again in June will increase grass supply at a critical time now on beef and sheep farms and ensure lactating livestock reach and sustain peak milk production to grow lambs and calves quickly. For growing beef cattle, compensatory growth is still strong during May, but cattle need a supply of grass to take advantage of this phenomenon. With silage fields closed up, the grazing area is at its highest stocking rate so enough grass must be grown during this key period on beef and sheep farms.

P is a key nutrient for grass. Its role in energy supply, root growth and tillering makes its availability crucial for grass growth. The plants requirement for P is small in volume when compared to N BUT its availability is essential. For grazing, P applications into May and June are important to maintain grass growth, herbage P concentration for growing livestock, and importantly to maintain and build soil P fertility. We should be looking to apply 10 kg/ha of P per annum to maintain soil P fertility, which can be met in part or full from applying YaraMila ExtraGrass.

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 ExtraGrass 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 for grass.

The latest Teagasc National Soil Fertility Trends for 2021 show over 50% of drystock farms have soil test results that are below the optimum K index, so it’s important K soil fertility is not neglected. Even though K offtakes are low for grazing, it’s a key nutrient to optimise N response.

ExtraGrass is a quality uniform compound which can be spread uniformly, with a maximum of landing sites for each nutrient. Beware blended fertilisers will have only one tenth the number of P & K landing sites that ExtraGrass will have. You also have the assurance with a Yara product that the analysis printed on the bag is the analysis in the bag.    

Fertiliser advice for growing fodder beet

Fodder beet crops needs adequate crop nutrition if they are to meet their energy and protein yield potential. It is only a cost effective crop to grow if it yields well. We should expect a well manged crop to hit dry matter yields in excess of 20 tonne/ha.

Growing fodder beet has been traditionally for feeding to housed livestock but its use for grazing in-situ over the winter has grown in popularity over the last number of years. For these grazed crops it’s about the proportion of root to leaf (or energy to protein) to meet the nutritional requirements of grazing livestock.

A high yielding crop of fodder beet can have nutrient uptakes of 250 kg, 90 kg, and 580 kg of nitrogen (N), phosphate (P) and potash (K) per ha respectively over the course of the growing season, so for these high yields to be achieved, the nutritional requirements of the crop need consideration. Using soil test results to determine the crops nutrient requirements from RB209, is a start.

The P & K requirements can be met in-part or in-full from organic manures with any deficit being made with P & K fertiliser. Part of the K requirement of beet crops can be replaced by salt and there is always a benefit in applying agricultural salt in combination with K particularly on low K index soils. Salt and K containing fertilisers should be applied at least two weeks in advance of drilling to mitigate any effect that the high chloride levels in these fertilisers might damage beet seedlings.

If applying organic manures, they need to be incorporated well in advance and incorporated into the seedbed. Usually all the P & K requirements are applied to the seedbed before planting. We are aiming to supply 150 kg/ha of YaraBela AXAN (40 kg/ha of N) into the seedbed, with a second application of 370 kg/ha of AXAN (100 kg/ha of N) when the crop is established.

Because beet is particularly susceptible to boron and manganese deficiency, we recommend a foliar application of YaraVita Brassitrel at 3 L/ha at the 4 – 6 leaf stage to meet the crops requirement for these necessary micronutrients. A second application 14 days later may be necessary where there is a known soil boron and manganese deficiency. Brassitrel Pro also provides N, molybdenum, magnesium and calcium to meet any shortfall during this critical phase of canopy development. Reaching canopy closure as soon as possible maximises light interception and maximises yield potential.

N is key in establishing the leaf canopy early to capture as much light as possible over the summer months, but also important later on in the growing cycle of the crop to promote and maintain leaf canopy later into the autumn and winter to increase both root and leaf protein content. New Zealand research has demonstrated that in Autumn beet crops can be accumulating up to 250 kg/ha of dry matter per day. So there is still a very high demand for both N and K during the autumn period. Traditionally two N applications are applied on fodder beet, in the seedbed and at establishment but we are also recommending a slow release foliar N application of YaraVita Safe-N 300 at 25 L/ha in August to promote top and root growth during this Autumn period.

For more information on growing fodder beet and other forage brassica crops contact your local Yara representative for advice.

Fine tuning your second cut fertiliser applications

With a move to more frequent silage cuts on dairy farms, the first two weeks in May are a busy time. With this in mind, it is worth reviewing your 2^nd cut fertiliser application plan and to ensure that you have the right type and quantity of fertiliser in the yard ready for application within the first week post harvesting.

If you are planning to reduce fertiliser inputs on second cut crops, it’s important to note that any savings in fertiliser may be offset by having to source more expensive feedstuffs to address potential reductions in grass dry matter (DM) yield.

Nitrogen & Sulphur

Nitrogen (N) drives grass growth and yield, and for this reason getting the N rate right is important. We thread a fine line with N applications, too much produces grass with lower sugar and higher ammonia and butyric acid levels, which can make silage less palatable. Too little N compromises yield and protein levels can be lower.

For swards with good yield potential then we would advise 90 – 100 kg/ha of total N for 2^nd cuts. In multi-cut systems, this rate may need to be adjusted down where the cutting interval is less than 6 weeks. Calculate the rate by multiplying the rate of N uptake (assume 2.5 kg/ha per day) by the number of days between 1^st cut harvest date and the expected 2^nd cut harvest date.

Each kg of N applied should return 20-25 kg of grass dry matter (DM). If N is costing £1.30 per kg then each kg of DM is costing 5 - 6 pence to grow. In comparison, cake at £400 tonne costs 47 pence per kg DM.

Using the Fertiliser Manual (RB 209) the available N per 11 m³/ha (1,000 gallons/acre) of 6% DM cattle slurry applied during the summer months is 7 kg/ha (6 units/acre) by splash plate and 9 kg/ha (7 units/acre) band spread. Please refer to the examples below to calculate the mineral N requirement with slurry applications.

Applying 20 – 30 kg/ha of sulphur in your 2^nd cut fertiliser is very worthwhile. This optimises N use efficiency, resulting in higher yields and in many instances improves silage quality. Anything that improves N use efficiency will lower soil nitrate leaching.

P & K

Phosphate (P) and potash (K) recommendations should be based on recent soil test results.

Fields regularly cut for silage have a higher requirement for P and K due to the high removal of these nutrients by the crop. A tonne of grass cut for silage will contain 1.9 kg of P and 8.3 kg of K. The addition of K is particularly important to maintain grass yields, and slurry applications should be prioritised on the silage area to replenish the K removed in the previous year’s silage crops. Table 1 outlines the P and K recommendations for 2^nd cut silage.

Table 1: P and K recommendations for 2^nd cut silage (RB 209)

How much P and K will slurry provide? If we haven’t had a sample tested in a lab, then we have to use the RB 209 book value for 6 % DM cattle slurry. This gives us the following P and K values for each 11 m³/ha (1,000 gallons/acre) applied.

Where the soil index is 2-/+ or greater for P and K:

• 13 kg/ha (11 units/acre) of P
• 27 kg/ha (22 units/acre) of K

Where the soil index is 0 or 1 for P and K:

• 7 kg/ha (5 units/acre) of P
• 25 kg/ha (20 units/acre) of K

Example 1: 2^nd cut fertiliser recommendation with a soil P index of 2 and the K index is 2-

Example 2: 2nd cut fertiliser recommendation where the soil P and K index is 1

For example 1, we would recommend 360 kg/ha of YaraMila NK SULPHUR to complement the slurry application and for example 2, the recommendation would be 430 kg/ha of YaraMila Silage Booster. Finally, slurry should be applied as soon after the 1^st cut as possible, and then apply the fertiliser a week later. If slurry isn’t been used, then spread the fertiliser as soon as possible. Delays reduce 2^nd cut yields.

Soil fertility is vital: Test It, Review It & Take Action

At some stage, over the next couple of months, plan to do some soil testing if you haven’t done so already. Once you have the results, don’t file them in a drawer! Review them and use them to put together a nutrient management plan (NMP) for 2023. Your NMP is about prioritising how to use organic and mineral nutrients on the farm in the most cost effective way possible.

Too often, organic manures are applied on the same parts of the farm, year after year. There are plenty of reasons why this is done, but it’s not maximising the potential value of this valuable resource. Using umbilical spreading systems may be an option to target other areas of the farm. Target cattle slurry at low K index soils as it’s a cost effective potash source.

Intensively stocked grassland farms should consider soil testing more regularly. By soil testing every 2–3 years, you’re in a better position to monitor soil fertility trends. Fertiliser recommendations are not an exact science, hence soil testing more frequently together with measuring grass yields will help you fine tune your NMP for every paddock or field on your farm.

Remember, grass requires a continuous and balanced nutrient supply from the soil to achieve its production potential. If a farmer is regularly soil testing, say every three years, then the £1 ha/year cost is money well spent.

For more information on soil testing this spring, visit Yara analytical services.

Grazing management of new leys this autumn

Many new leys sown in August may be fit to graze now, but these newly sown swards require specific management practices to get the most from them.  

There is a tendency to delay the initial grazing of these new leys, which leads to grass covers building up. Then, when animals graze them, there’s a high degree of sod pulling. This first grazing is important. New leys should be grazed as soon as the new roots are strong enough to withstand grazing. We can check for this by using our fingers to see if the root stays anchored in the ground when the plant is pulled.

Early grazing of these leys is important as it allows light into the base of the ley which will encourage tillering. A light grazing by calves, young stock or sheep is preferable. Bigger animals have more of a tendency to cause sod pull and poaching at this time of year. A first grazing can usually take place when the sward is at 6–8 cm’s in height.

Don’t be tempted to allow grass to build up on these new leys for a late cut of silage. This will inhibit tillering, resulting in more open swards which will be more susceptible to weed germination in the spring. Low winter covers will also benefit clover performance come spring.

If you haven’t soil tested before seeding, then it would be a good idea to do so before the spring. New leys are more productive and utilise nitrogen more efficiently but only if soil fertility is adequate.       

Research confirms sulphur benefits on grassland

New sulphur (S) research from Teagasc in Ireland highlights some interesting findings on S applications on grassland. Using lysimeters and a sandy loam soil they found N + S applications increased grass yields by 30%, compared to N only plots over the course of 7 cuts. Treatments received 250kg N/ha, divided over 7 splits. For the two slurry treatments, there was a 24% yield increase by using a N + S fertiliser with slurry compared to N only fertiliser with slurry.

Apparent Fertiliser Nitrogen Recovery (AFNR) which is a measure of how much of the applied N was taken up by the crop was also increased with sulphur applications. N only plots had a AFNR of 39%, compared to 49% for the N + S treatments. For the slurry treatments the addition of mineral S in the fertiliser increased the AFNR by 13%.

The leachate from the treatments amounted to 68% of total rainfall over the 12 month study. Nitrate leaching loses per ha for the N only plots was 48.2kg NO3-N, whilst the N + S treatment was 26 kg NO3-N which was only 2kg greater than the Zero N control treatment. The nitrate leaching losses for the slurry treatments were very surprising. The N + slurry treatment had losses of 82.8kg NO3-N, in contrast to the N + S + slurry treatment which had losses of 33kg NO3-N.

The study concluded that S fertilisation is potentially important for increasing grass yield, N use efficiency and reducing nitrate leaching losses on certain soils.

Autumn grazing management

The focus of autumn grazing management is to increase the number of days at grass and animal performance, but also to set the farm up during the final rotation to grow grass over winter and provide grass the following spring.

Because grass remains leafy, rotation length can be extended from the 2^nd week in August. The focus of this period is to gradually build pre-grazing covers, targeting covers of 3,500kg to 3,700kg DM/ha in mid-September. Be careful to not allow covers build beyond 4,000kg DM/ha for grazing, as utilisation is poorer. We want to avoid taking paddocks out for silage after the start of September, as these paddocks won’t have enough time to re-grow to make a significant contribution to the last rotation.

If Autumn nitrogen is going to be spread, it should be spread in August and September. As you can see from the graph, the growth response to October applications is likely to be significantly lower, and may not be economical. Our Calcium Ammonium Nitrate based fertiliser YaraBela NUTRI BOOSTER, with sulphur and selenium at 120kg/ha, is an appropriate rate for applications during August and into the first half of September.

Drier or ‘earlier’ paddocks should be grazed from mid-September and then closed off from October onwards. Regrowth on these parts can be carried over the winter months for grazing first in the spring.

Are you sowing forage brassicas this summer?

Are you looking to sow a forage brassica crop in July and August in a bid to keep livestock out grazing for longer, and to therefore reduce your livestock feed and housing costs this winter? These crops can be economically established into stubble and then grazed from late autumn onwards. However, they might not fit into every system and site selection is crucial, especially when grazing them.

The nutrient requirements of either Forage Rape, Stubble Turnips or Rape/Kale hybrid crops are similar. They respond well to nitrogen and sulphur applications and good soil phosphate fertility. On fields with good (index 2) soil phosphate and potash fertility, we recommend 370 – 420 kg/ha (3 - 3½ cwt./acre) of YaraMila 52S or YaraMila SILAGE BOOSTER broadcast onto the seedbed in one application. This will provide all the nitrogen, phosphate, potash and sulphur these crops need to establish and maximise growth over a comparatively short growing period.

Brassica crops also have a requirement for boron, and we recommend at least one foliar application of YaraVita BRASSITREL PRO at a rate of 3 L/ha at the 4 – 6 leaf stage. This is a flowable liquid suspension fertiliser with a balanced combination of micronutrients including boron, manganese, magnesium and molybdenum for foliar application on forage brassicas.

Don’t delay sowing these crops, as research demonstrates that the yield of Forage Rape sown at the end of August is less than 30% of that sown in the first week in August.

For more information search online for “Yara forage brassica”.

Don’t let potash hold your 3^rd cut back

If you’re planning to fertilise 3^rd cuts, then we should be aiming to apply between 70 – 80 kg/ha of N. If this is not the final cut, then stay at the lower end of this range, and for those taking only 3 cuts  - then aim for the higher end of the range, as the growing period is generally longer. Spread slurry as soon as is practical after the 2^nd cut harvest, and then a week later follow up with the fertiliser.

From both a yield and silage quality perspective, a sulphur (S) containing fertiliser should be used. At optimum N rates, we see a 10% increase in dry matter yields on average where S is applied, rising to 20% on very responsive lighter soil types. During dry weather, sulphur availability to the grass plant becomes even more important.

Pay particular attention to potash (K) at this stage of the year. A 23 and 15 t/ha crop of 1^st and 2^nd cut respectively, will remove 310 kg/ha of K₂O. A 3^rd cut is likely to remove another 75 kg’s, so it’s worth calculating how much K has been applied. If slurry contains 2.5 kg of K₂O per cubic metre, that’s 154 cubic metres of slurry needed to replenish the K offtake from 3 cuts.

If slurry can meet the P & K demands of the 3^rd cut, then an N + S fertiliser - such as YaraBela Nutri Booster could be used. If not, YaraMila NK Sulphur is an option on 3^rd cuts if P is not required.

To check out Yara’s full range of quality compound fertilisers, please visit https://www.yara.co.uk/crop-nutrition/fertiliser/.  

More effective grassland weed control with foliar nutrition

When getting the sprayer out to control grassland weeds on grass this summer, it’s worth considering adding a foliar fertiliser to the tank for two reasons:

1. The effectiveness of herbicides on grassland can be improved if the correct foliar fertiliser is tank-mixed with the herbicide. This foliar fertiliser is absorbed by both the target and non-target species and stimulates plant growth, including the weeds. The plants which are growing actively are more likely to translocate the active ingredients within the herbicide effectively around the plant and down into the roots. This results in the herbicide working more effectively on the target weed species.

2. A phytotoxic effect of grass herbicides is often seen as a ‘check’ in growth on newly sprayed swards, and especially when growing conditions are not ideal. The application of a foliar fertiliser, in combination with the herbicide, helps offset any side effects of the herbicide on the sward. An added bonus on newly established leys is the improved growth of grass seedlings, which in turn will promote tillering - reducing light and space for any new germinating weeds.

We recommend YaraVita Croplift Pro at a rate of 5 kg/ha (2 kg/acre) for inclusion in a tank mix with your chosen grass herbicide. This foliar fertiliser, containing multiple nutrients and micronutrients for foliar application on grassland, is ideal at times of stress or periods of rapid growth. It has excellent plant absorption properties, giving an immediate and long-lasting feeding effect on stressed grass crops.

A fine balance between quantity and quality

As I watch farmers about to start taking their second cut of the season, I reflect that not so long ago, the three-cut system used to dominate. In recent years we’ve seen farmers shift to a four and even five-cut system. But why have we seen that shift?

Whilst three cut silage systems can yield extraordinarily well and produce good quality silage, they do require higher inclusion rates of concentrate feed to balance milking cow rations. By moving to 4 and 5 cuts per season, silage quality improves because you’re cutting grass with a higher leaf-to-stem ratio. There are some drawbacks, such as higher machinery costs with cutting more frequently and there can be lower overall DM production, but in general, the advantages outweigh the disadvantages. Milk from forage figures improve as well as herd production and health as forage makes up a greater proportion of the ration.

A trial conducted in Northern Ireland a few years ago, comparing 3-cut and 4-cut silage systems, found total silage dry matter (DM) yields for the 3 and 4-cut systems were 13.4 t DM/ha and 12.3 t DM/ha respectively. The average DM of the 3-cut system was 31.9% and 34.4% for the 4-cut system. The average metabolizable energy (MJ/kg DM) was 10.7 and 11.3, and average protein (% DM) was 14.3 and 16.4 for the 3 and 4-cut systems respectively.

Cows on the 4-cut system had higher silage intakes (+9.5%), and produced more milk (+6.4%) with higher milk protein (+2.1%) but slightly lower fat content (-2.4%). Silage production costs were calculated as £114 and £135 t/DM for the 3 and 4-cut system respectively. This includes a land charge, reseeding cost and a contractor for harvesting.

Total feed costs of 23 pence/cow/day higher with the 4-cut system, but the value of milk produced was 71 pence/cow/day higher. The margin-over-feed cost was 48 pence/cow/day higher for the 4-cut system. At the time this was calculated for a 100 cow herd over a 180-day winter period, the 4-cut system resulted in a £8,640 increase in margin-over-feed costs.

Fertiliser application advice

To give your growing grass just enough fertilizer to flourish, whilst maximising nitrogen use efficiency and saving on input costs, we would recommend that you plan how much nitrogen is required to grow this 3rd cut efficiently. You’ll want to apply 70-80kilos of nitrogen per hectare on third cuts. The lower end of this range for shorter growing periods and upper end of this range with longer growing periods.

But don’t forget to take into account any slurry applications. To calculate how much nitrogen you’re likely to apply through your slurry you can do one of three things: (1) use RB209, (2) use a slurry analysis taken earlier in the year, or for the most precise calculation (3) undertake a new slurry analysis to calculate exactly how much nitrogen is present. Once you know how much you’re able to apply through your slurry, you’ll know how much mineral nitrogen fertiliser you’ll need to top it up with. Remember sulphur is a key nutrient on these crops to optimise nitrogen use efficiency.

Spread your slurry straight after you’ve taken your third cut and then follow that up with your mineral fertiliser six days later.

If you’re worried about your input costs, don’t forget to use AHDB’s new grassland cost-benefit fertiliser calculator to protect your return.

Improve your maize yield potential with foliar nutrition

Due to its high yield potential, Maize also has a high demand for nutrients. Therefore 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 and Magnesium is essential for the early establishment of the plant. A deficiency can often be reflected in reduced crop yield at harvest.

Phosphorus and potash are primary nutrients, however, many soils do not have 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 – and 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 Crop 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 maize foliar nutrition

Don’t risk winter feed stocks – act now with fertiliser on second cuts

Where second cuts are being grown to fill clamps for the winter ahead, thought should be given to the nutrient requirements of these crops. Second cuts are capable of very high yields, with 15 – 17 t/ha (6 – 7 t/acre) of grass achievable on swards which have good yield potential.

New swards have excellent yield potential and respond to higher nitrogen (N) rates of up to 100 kg/ha (80 units/acre). Older swards with a high proportion of perennial ryegrass (PRG) can be fertilised to 90 kg/ha (72 units/acre) N and old meadow swards which don’t contain much PRG should receive 70 kg/ha (56 units/acre) N.

With slurry, if none or low volumes are applied, on account of the risk of slurry contaminating second cut grass at harvest, then make sure to use an NPKS fertiliser like YaraMila SILAGE BOOSTER. Don’t forget sulphur on these second cuts. 10 – 12 kg/ha (8-10 units/acre) of S is enough.

A good second cut requires a proactive approach to ensure these crops are optimally fertilised, so in the long run, only using slurry and straight N may not be the most cost-effective option. Just think about the cost of homegrown silage versus purchased feed at current cost levels!

Finally, don’t delay in applying slurry and fertiliser. The slurry should be applied immediately after the first cut is harvested and then apply the fertiliser 5 – 7 days later. If slurry isn’t being applied, then get the fertiliser out ASAP

Maize needs an efficient form of phosphate

A crop of maize can produce up to 50 t/ha of fresh weight in just 4 months. For this amount of growth over a short timeframe to happen there needs to be a healthy, extensive root system for nutrient uptake from the start.

Phosphate (P) is a very important nutrient, key for growing the root system the crop requires to sustain the rapid growth, as well as being part of the transfer of energy within the plant. Weather plays a role in the availability of P, if soils are cold and wet when the maize is planted then P in the soil will have a very low level of availability, which is why placing some at drilling helps this by providing immediately available forms.

Nutrient availability in general decreases in dry soils, as we’ve had recently, and this will restrict root growth and therefore the ability to support the crop later in the season.

So how do we get around this? A foliar application of phosphate is the best way to overcome these early deficiencies and give the crop a boost in energy levels, both of these will help the crop develop a better root system to support later growth. YaraVita Crop Boost contains foliar phosphate, together with useful amounts of zinc, magnesium and potash. Applying it at the 4-6 leaf stage is effective for fast, efficient uptake through the leaf.

Biostimulants can also help during periods of abiotic stress, such as dry conditions. Trial work carried out in 2021 showed that YaraVita Biotrac, a biostimulant product, increased the yield in maize when applied in combination with YaraVita Crop Boost, by up to 4.4t/ha.

Read more about maize foliar nutrition

Foliar nitrogen for grassland?

There are farmers committing to replacing a large chunk of their soil-applied nitrogen (N) with foliar N in a bid to save money. This is certainly a risky strategy, considering the lack of grassland specific data for these foliar N products on first cut silage crops.

If we analyse one aspect of this strategy, that is – if we substitute 50 – 80 kg/ha of soil-applied N and replace it with 20 - 30 litres of a product that contains 30% N, we are expecting similar yield and protein content by applying only a fraction of normal practice.

If you expect that a good 1^st cut yields 5.5 tonnes of dry matter (DM), with 3.0 tonnes of this coming from the soil's own N reserves through mineralisation etc. This means that approximately 2.5 tonnes is attributed to available N (as bagged N and/or slurry). If the crop contains a modest 14% DM protein, this equates to 123 kg/ha of N contained in that crop as protein. Since 2.5 tonnes is grown with N applied as slurry/fertiliser, that means this portion of the crop requires at least 56 kg/ha of N to synthesise the protein.

Therefore, a first cut at 14% protein requires at least 56 kg/ha of applied N as slurry and/or fertiliser. So where does the N come from to make this protein if you’re only applying 6 – 9 kg/ha of foliar N to replace the 50 – 80 kg’s of soil-applied N? Worth noting that this approach could also lead to nitrogen use efficiency (NUE) greater than 100%, which goes against the guidelines to target 80-90% NUE for sustainable yields and future production security.  

A successful first cut starts now

Tonne for tonne, first cut silage is the most economical to make and usually the highest quality.

At the field level, the single biggest factor contributing to the cost of producing silage is the yield of the crop. The challenge for farmers is to maximise silage yield while at the same time achieving target silage quality for the production system on the farm.

Whether or not the first cut silage area is being grazed this spring, the important thing is that swards with yellow/dead material at the base must be grazed off. Where this material is not removed before closing, silage D-values will be 5-7 points lower. As for winter grazing sheep, they should certainly be away at this stage. Not doing so will lower your first cut yield.

As for slurry applications, if not applied already then it needs to be on as soon as possible, but only on very short grass and when field conditions allow. Using trailing shoe equipment gives some scope to apply where there are slightly higher grass covers. Make a note of application rates on each field, as this will need to be known to calculate the fertiliser rate.

With the current cost of fertiliser, it’s worthwhile testing slurry, especially if you haven’t done so before. Then by using both slurry and soil test results, we can calculate how much fertiliser is required on each field to grow a crop that fulfils both yield and quality expectations.

There will certainly be more scrutiny on fertiliser rates and timings this year. With many farmers looking to cut rates or use less conventional methods to fertilise first cuts in a bid to offset some of the rises in fertiliser prices.

As mentioned above, the fertiliser rate should be determined on a field-by-field basis, using the recommendations from Section 3 of RB209. On perennial ryegrass swards (PRG) with good growth potential and good soil fertility, the recommended nitrogen (N) rate is 120 kg/ha N where forage demand is high. For less productive swards (low PRG content) or where demand is lower, the N rate should be reduced to 90 kg/ha.

Where slurry has or will be applied, don’t feel rushed to apply N too early as the available N in the slurry is sufficient to keep grass growing during this early March period when grass N demand is low. Where no organic manures will be applied, then a third of your N rate should be applied as soon as soil conditions and soil temperatures (> 6^oC) allow, with the remaining 2-3 weeks afterwards.

Where fields have a soil P or K index of 2 or less, and slurry/manure hasn’t met the requirement of 40kg/ha P and 80kg/ha K for the first cut, then an NPK fertiliser with sulphur should be applied. If not, Liebig’s law of the minimum will apply, and growth will be dictated by the scarcest nutrient!

Sulphur and selenium applications are essential

Three Welsh Farming Connect demo sites took part in a project to establish the effectiveness of sulphur and selenium applications using YaraMila Silage Booster and YaraBela Nutri Booster against standard fertiliser blends on silage swards in 2021. Independent grassland and soil specialist Chris Duller provided technical support to the trial.

Mr Duller sampled the grass, and analysis showed that across all sites, in both fresh herbage and silage, the Booster fertilisers increased the selenium content – typically by five times in fresh grass, and by up to three times in silage.

“Raising the selenium status of forage through the use of fertilisers containing selenium has the potential to improve productivity, and can be a useful addition, or an alternative, to mineral supplementation and bolusing,’’ he says.

Yield benefits of up to 11% were recorded on all three farms. With the typical cost of adding sulphur to each silage cut at around £7/ha, the extra grass grown in this trial (300kgDM/ha) is worth nearly £50 in terms of energy and protein. “That’s a healthy 7:1 return on investment,’’ says Mr Duller.

Crude protein and energy levels were very variable in the fresh herbage, with no clear trends, but sugar levels were higher in the grass where the Booster fertilisers had been applied on five of the six sample runs. “Silage analyses recorded an increase in ME at all sites/silage cuts and an increase in crude protein in three of the four samples,’’ says Mr Duller.