Foliar nitrogen options for milling wheat – which product works best?

 A recent blog from SOYL looked at how variable rate applications of foliar nitrogen could help to maximise protein levels in milling wheat.

While this is an advantageous method to help meet the target, it's also worthwhile considering the type of foliar nitrogen being used and which is best suited to the job.

This year it is vital for those aiming for the quality market to achieve the 13% protein target, especially with such a significant amount of milling wheat varieties in the ground this year. Reasonable premiums (around £15/t) are currently available for meeting full specification but it's unlikely there will be much demand for sub-12.5% protein. Now we are in the absolute key stage for growth and yield production, it is essential to monitor crop development and assess yield potential.

Yield dilution

Clearly everyone is aiming for high yields but in milling wheat this make the challenge of hitting 13% protein even greater. Consider the sobering figures in the table below which show the affect a crop not taking up enough nitrogen has on grain protein and the sheer quantity of nitrogen required as the yields increase:  

The key from now onwards is to continually assess the yield potential of your milling crops in comparison to the previous performance on the farm over the last few years. Results in 2014 and 2015 harvests should give most farmers an idea of their best yield potential. It is important to note that the pass rate for achieving 13% protein in these years was only 16% and 37% respectively, because of yield dilution.

As explained in the blog from SOYL, their expert team are developing another, more accurate method for giving indications of potential yield levels within fields through the use of biomass imagery. As this develops, it could certainly make managing high yielding milling wheat crops easier.

As well as looking at yield potential, you can also look at the nitrogen level within the crop either by lab analysis or its correlation to the Yara N-Tester reading. This will give you an idea of whether the crop has taken up enough nitrogen to achieve the optimum yield and protein, or if more is potentially required. 

The role of foliar nitrogen

With the final solid and liquid (UAN) applications now applied, the only option remaining to influence the nitrogen levels within the crop are foliar products. These products will increase grain protein levels but it is important to understand their limitations.

Generally the increase they contribute to will be in the region of 0.5 to 0.75%, so unless your nitrogen program applied so far will produce grain protein above 12.25%, it will not get you to the 13%.

Simply applying a foliar product on top of a normal feed wheat base program will not generally work, especially as yields increase. 

Which foliar product is the most effective?

Foliar products fall into two camps, either straight foliar urea or formulated products.

• Foliar urea

As you would expect, foliar urea (Protein Plus) is simply a liquid urea either with or without a small amount of sulphur.

The use rate is high (usually 200lts/ha with extra water) and it supplies a reasonable amount of nitrogen which can give decent lifts in grain protein. However, there are drawbacks.

The product can sometimes scorch the crop, affecting final yield, and it is also prone to nitrogen losses. Firstly, ammonia gas can volatilise off the leaf surface before is taken up by the crop and secondly, it isn't at all rainfast, needing a considerable dry period after application.
A further complication is the general need for liquid storage on farm to take the pump off deliveries.

• Formulated products
  The formulated product, Multi N (33% N & 25% SO₃) on the other hand is very different.

Firstly, the use rate is significantly lower at 33-40lts/ha (with 100lts/ha of water) which reduces workload and also means that no storage is required as it is delivered in IBC tanks. This does reduce the rate of nitrogen applied, but the significant improvement in crop uptake generates a more consistent uplift in grain protein.
The greater uptake comes from reduced losses, along with improvements in leaf penetration.

An incorporated latex adjuvant reduces ammonia losses and also makes it rainfast in 30 minutes. This is a significant benefit if the weather is catchy during the optimum application window (end of flowering to milky ripe grain).

Multi N also poses a greatly reduced scorch risk and can even be tank mixed with some fungicides, although this isn't generally the ideal time for a T3 application.
The significant sulphur content of Multi N is also very important, as deficiency can limit protein production even when adequate amounts of nitrogen have been supplied to the crop.

To further improve the product, it now contains magnesium to optimise photosynthesis and to help increase specific weights.

Although previously stressed, it's worth reiterating that you must comply with the nitrate vulnerable zones (NVZ) N-max rules for your milling wheat crops. It should be fine given the historic high yields in 2014 and 2015 and Multi N also helps here, given the lower rate of nitrogen that is applied.

Consider how your crops could benefit

 Achieving 13% protein will be essential this year to gain full premiums, so please consider the yield potential of your milling crops as they develop over the coming weeks.

There is still a long way to go (roughly 40% of biomass is produced after ear emergence) but good crops could yield very well if the sun continues to shine and adequate rains fall.

Foliar nitrogen products, like Multi N, are already integral on many farms but they could be an even more important component in getting enough nitrogen into crops this year.

​​Edward Downing​
National crop nutrition technical manager