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.
  1. 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.

Latest advice background
Latest advice background
Grow the future | Grassland Sulphur Grow the future | Grassland Sulphur

Spreading nitrogen and sulphur at the same time means more grass

Applying fertilisers containing nitrogen and sulphur means the grass uses nitrogen more effectively, you get more kgs of dry matter per kg of nitrogen that you apply

Find out more

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 Maize Boost is specifically formulated for foliar applications on maize. It will deliver a high concentration of phosphate, zinc, magnesium and potash to maximise maize yield and quality this harvest.

Read more on maize foliar nutrition

Don’t risk winter feed stocks – act now with 2nd cut fertiliser

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. 25 – 30 kg/ha (20 – 24 units/acre) of SO3 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

Grassland agronomy advice

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

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 Maize 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 Maize 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 1st 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 (> 6oC) 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.