Making your nitrogen applications as efficient as possible

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There has been no shortage of news articles lately covering the ‘perfect storm’ that rising fuel and nitrogen prices will have on UK agriculture and the wider economy, with fertiliser prices high, (at the time of writing nearly £1000/t for Ammonium Nitrate) and much still to be delivered to farm, the conclusion drawn by many pundits is that lower application levels will lead to reduced quality and yield at harvest.

Simon Fox of Emerald Research Ltd (ERL) doesn’t believe this has to be the case, and that farmers and growers still have time to ensure harvest tonnages are not reduced due to lower nitrogen applications. He looks at the different strategies that can be utilised over the coming season (and following seasons) to maximise nitrogen efficiency.

The strategies that Simon puts forward to enable crop production to be maximised, even with reduced nitrogen, all have Liebig’s law of tolerance or the ‘law of the minimum’ at their core. In essence, if one of the essential plant nutrients is deficient, plant and yield development will be restricted, even when all other essential nutrients are abundant. To achieve optimum crop quality and quantity, it is essential to ensure all nutrients, not just nitrogen, are sufficiently available at key growth stages, such as tuber initiation and bulking.

Placement at planting

In some areas, planting of sugar beet and potatoes is still to happen, and this is the optimum time to apply nitrogen, phosphate and potash to the soil, as they encourage the tap root to reach a pocket of nutrients when they are needed to boost root development, resulting in better rooting. It is important to remember that while nitrogen is water soluble and can move through the soil, phosphate is immobile and will only travel 1 mm a year, making it imperative that it is placed where it can be reached easily.

Don’t forget the highly important minor nutrients either. Ideally, Calcium and Magnesium should be applied into the seedbed prior to planting and making sure that sulphur levels are current through a combination of soil applied and foliar fertilisers is also essential to support the function of nitrogen.

The key to crop success is early establishment and early crop vigour to create a robust root system. With the current season hike in fertiliser prices, now is the time to ‘cash in’ on any ‘banked’ nutrients from previous seasons. So, planting is also the ideal opportunity to place specialist soil microbial mixes next to the seed that stimulate and promote root growth from the start. These microbes will help to provide an extensive root network that allows the crop to exploit any nutrients in the root zone.

The following strategies offer ways to mitigate shortages in any macro/micro-nutrients, production of amino acids, or elements, as this is where the ‘law of the minimum’ really comes into play. Restricting nutrients will affect the crop’s ability to develop fully, but its reaction and resilience to unforeseen environmental stresses (heat, cold, drought, wet) can also very significantly impact on the overall crop quality and tonnage.


The use of high-quality, well-formulated biostimulants is well-documented, especially at critical growth stages. They can perform several supporting functions to the crop by stimulating or enhancing the crop’s natural processes that, together, increase efficient nutrient usage, improve plant growth and environmental tolerance.  By ensuring plants remain healthy and can effectively continue their growing cycle, the crop has the best chance of meeting its genetic potential.

Foliar applications

Once the canopy is developed, the opportunity to continue broadcast applications with optimum take-up is limited, which is where the use of foliar applied nitrogen, phosphate, potash, micronutrients and biostimulants can be considered the key to more efficient input usage.

Today’s third generation foliar applications have been designed and developed from 1000’s of natural materials using fundamentals of biochemistry technology and have overcome the inadequacies of the previous generations by being:

  • Proven activity
  • Rapidly absorbed and translocated within the plant
  • No crop scorch or phytotoxicity
  • Rainfast in 30 mins
  • Suitable for tank mixing with fungicide and blight sprays

This type of application is particularly suited to potatoes, where significant applications of foliar nitrogen (30 kgs N/Ha or more) can be applied in a single dose without risk of crop damage and with very high Nitrogen Use Efficiency (NUE) of 90% or more.

Along with  other nutritional supplements these applications can be used at tuber initiation in potatoes to increase the number of viable sets and to extend the life of the green canopy, particularly at bulking, or to increase root size and sugar content in sugar beet. The greater the canopy area, the more energy is created through photosynthesis, which leads to increased tuber and root size.

Utilising atmospheric nitrogen through fixing.

We tend to forget about the free source of nitrogen that is around us all the time in the atmosphere. Through the additional use of nitrogen-fixing soil microbes, it is possible to improve the soil’s natural levels of nitrogen at the root level, making this available to the crop.

In-field Sap testing

For optimal nitrogen uptake in potatoes, the levels of magnesium and potassium need to be maintained; any drop in these will lead to inefficient uptake and a reduction in overall crop performance.  Testing these levels can be easily done with in-field Sap testing kits.  The results can be used to tailor any additional magnesium or potassium foliar applications, thereby only applying what’s needed at the most appropriate time.

While the decision to apply less nitrogen maybe driven by cost and supply rather than for the good of the environment, in the long run, it is where UK agriculture needs to move to. The strategies that will need to be applied this year to achieve the best tonnages possible, will need to become part of every season’s planning, if farmers and growers are to produce more with reduced inputs.



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