Features
06 February, 2020

Foliar phosphate – energising cereal crops for spring growth

By: Mark Tucker

Many cereal crops struggle to get moving in early spring due to low phosphorus levels as a result of low phosphate availability in cold wet or waterlogged soils exacerbated by poor or compromised root systems from delayed drilling and waterlogged soils. Giving these crops a quick 'energy boost' from foliar phosphate is the best way to get them started.


Foliar phosphate – energising cereal crops for spring growth
Foliar phosphate – energising cereal crops for spring growth

The early spring growth period in cereal crops is an essential phase during which the foundation for high biomass is established. High biomass is a fundamental prerequisite to achieving high grain yields. This biomass is the result of achieving a good population of main shoots and tillers. The main shoot numbers are determined by the initial seed rate, and then the subsequent germination % and plant survival.

Tiller numbers are affected by the prevailing conditions during the weeks and months between initial emergence and the growth stage GS 29. The tillering phase commences after leaf 3 is fully expanded and generally finishes when the ‘double-ridge’ stage of development is reached (just before GS 30.) This growth stage is typically reached by mid-March. The final number of tillers can therefore be manipulated through the appropriate use of inputs. One such input is crop nutrition.

Phosphate deficiencies will limit early spring growth

Nutrient deficiencies, especially nitrogen and phosphate, will limit early spring growth and development, thus reducing the number of tillers produced. Such a limitation becomes ever more important in years when drilling is severely delayed, or winter conditions (e.g. water logging or severe cold) prevail.

Water logging has been shown to reduce tiller production by 40% to 85% (Malik et al, 2001). Not only is the tillering capacity restricted, but also the root size and structure. This poor rooting further exacerbates the potential for poor nutrient uptake, making the plants vulnerable to stress periods as the season progresses.

Poor rooting further exacerbates nutrient uptake

To give the plants the best chance of early spring growth and development it is important to focus on those nutrients that are most likely to be limiting. Considering phosphate, the processes in the soil that determine how much phosphate is in the ‘available pool’, which is the one that the plants draw from as they require it, are temperature dependent i.e. cold soils reduce soil phosphate availability.

The developing cereal plants grow at these cold temperatures (approx. 5 – 6 °C), thus potentially exhausting this supply. A poor supply of phosphate restricts the conversion of solar energy into the plants chemical energy (ATP) that is used during photosynthesis to drive new growth and development.

To help overcome this limitation there are actions that can help. Firstly, consider how the root system can be repaired, or improved to enable better access to nutrients that are available. One way of repairing and building a larger root system is to apply some phosphate through the leaves. Research has shown that an application at GS 25 – 29 can significantly increase the root size / area

Foliar application of phosphate gives an ‘energy boost’ to the crop

This foliar application of phosphate gives an ‘energy boost’ to the crop, stimulating growth of roots and consequently shoots. Not only does this give an immediate benefit by way of recovery / repair, it builds in resilience, enabling the crop to overcome further potential stress points such as drought during the spring and summer months.

Secondly it is important to consider the soil nutrient supply and how this needs to be managed. Such an injection of growth through the foliar phosphate application will of course create further demands on the soil nutrient supply to satisfy this new growth. There is the potential that the cold wet soils have a very limited pool of available phosphate that will be quickly exhausted. Therefore to ensure the new growth momentum continues, supply some fresh soil applied phosphate such as a YaraMila grade.

Effect of foliar phosphate on root growth

This combination of a YaraVita foliar phosphate product along with an application of YaraMila soil applied phosphate will energise the crop for early, rapid spring growth and development to recover and build biomass for an improved grain harvest. Indeed, recent Yara trials have shown wheat yield increases from 0.23 – 0.6 t/ha.

YaraVita Magphos K is recomended on on all cereals

An application of foliar phosphate such as YaraVita Magphos K at 5 l/ha during tillering, idealy GS 25-29, will give a much needed 'energy boost' to get crops moving again. This then should be followed up with a solid NPKS fertiliser such as YaraMila Actyva S very soon afterwards so that the crop doesn’t run out of momentum once it's has started.

Read more about YaraVita foliar fertilisers

Wheat agronomy and fertiliser advice
Wheat agronomy and fertiliser advice

Subscribe to arable agronomy advice

Our agronomy team send out regular updates of the latest arable advice. If you would like to receive this advice please use this form to submit your details and let us know which crops you are most interested in.

By submitting the form you confirm that you have been informed that we process your data in accordance with our Privacy Policy.