Cereal Growth & Nutrition

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a. Nitrogen in the environment and plant uptake

Plants contain 1% – 6% Nitrogen (N) by weight and absorb N as Nitrate (NO3), Ammonium (NH4) and Amine (NH2 – ureic nitrogen), however in moist warm, well aerated soils, soil solution NO3 is generally greater than either NH4 or NH2. This occurs due to the naturally occurring ‘nitrogen cycle’ whereby ‘mineralisation’ of organic N forms (Ureic or Amine-N) to NH4 by soil organisms is followed by ‘nitrification’ by soil bacteria converting the NH4 to NO3. Therefore, regardless of the form of nitrogen supplied, the form in most abundance and therefore taken up by crops will always be NO3.

b. Nitrogen metabolism and ‘Growth Partitioning’

There are several implications for plant growth resulting from the uptake of different forms of N;

1. Plants metabolise NO3 to NH4 and then on to amino acids and proteins, the reduction of NO3 to NH4 is an energy requiring process that uses nitrate reductase. The use of NH4 or NH2 removes the requirement for the plant to convert the NO3 to NH4 and therefore is more energy efficient, NH2 and NH4 cost the plant 12 times less carbon to process into a protein than NO3!

   This has implication for crop growth, especially during periods of crop stress when unnecessary use of carbohydrate (used to metabolise NO3) can have detrimental effects on plant growth, impacting such physiological processes as tiller survival and spikelet determination between double ridge and terminal spikelet, around G.S. 30.

2. The form in which plants take up N and then metabolise it dictates where plants allocate growth through a process known as ‘growth partitioning’. This is due to the influence of N on the endogenous production of plant hormones, particularly auxin and cytokinin, the balance of which within the plant influences plant growth.

   Auxins are made in plant leaves and transported to the roots, with the opposite holding true for cytokinins which are made in the roots. When plants (wheat in this case) metabolise NO3, which occurs in the leaves, this stimulates the production of auxins which conveys apical dominance with the knock on effect of suppressing lateral bud (tiller) initiation in favour of vegetative (leafy) growth, whilst causing stems to stretch excessively, putting crops at more risk of lodging.

Modern wheat varieties have been bred to accommodate this trait [to an extent] using dwarfing genes, to allow the use of high amounts of artificially applied N taken up predominantly in the NO3 form to push yields, however the use of Plant Growth Regulators (PGRs) is still required to avoid lodging! When plants metabolise NH4 and NH2 [which takes place in the root] it stimulates cytokinin production which has the following influence on plant phenotype:

• Increased root length and proliferation
• Increased tiller number and survival.
• Increased stem thickness
• Improved leaf angle/position

These phenotypical responses favour reproductive growth (the parts you harvest) and resource capture that supports higher levels of grain yield, whilst use during periods of stress [that may compromise yield] can help counter the effects of stress where NO3 may potentially inflame the situation.

What is LimiN Technology?

Elona products contain Levity’s ‘LimiN Technology’ providing Stabilised Amine Nitrogen (SAN) which influences a plants growth habit via ‘growth partitioning’ when plants are exposed to SAN at critical growth stages and/or prior to or during periods of crop stress. Trials carried out using a modern wheat variety (var. Anapolis) at Myerscough College (2018) have demonstrated it is possible to enhance tiller angle [and thus improve light capture], improve root architecture [to enhance nutrient and moisture scavenging], whilst also enhancing leaf chlorophyll content [to improve photosynthetic yield]. Read our paper on ‘Stabilised Amine Nitrogen’s’ affect on wheat here.

Foundation Phase and LimiN

This phase of wheat growth includes germination, emergence, tillering and overwinter survival, all contributing to shoot number/m2 at the start of the construction phase. The following factors will influence plant growth and surviving shoot numbers in the spring:

• Plant population
• Soil fertility
• Pest damage
• Environmental conditions
  • Temperature
  • Moisture

• Drilling date
• Drilling rate
• Drilling depth
• Seed bed/Soil structure
• Germination %
• Plant population
• Soil fertility
• Pest damage
• Environmental conditions
  • Temperature
  • Moisture

Each of the listed factors will contribute individually, whilst also interacting with one another to contribute to shoot number in the early spring, providing the base from which crop yield is built at the beginning of the construction phase.

In addition, towards the end of the foundation phase is when the number of spikelet’s is determined per spike (ear) laying the foundation for grain number of each viable shoot (tiller). Crop stress and adverse environmental conditions (drought, heat, etc.) that occur during this time can adversely affect spikelet number and thus yield potential. 

The use of LimiN during the foundation phase

LimiN can be used during the foundation phase to encourage the following plant phenotypes to the benefit of crop yield:

• Improved root architecture helping to scavenge for more soil nutrients to support/enhance shoot (tiller) numbers.
• Metabolism of SAN resulting in higher levels of cytokinin as opposed to auxin within the plant favours reproductive growth as opposed to apical dominance and leaf proliferation.

In addition LimiN requires less carbon (energy) to metabolise it, therefore placing plants under less stress allowing them to make better use of resources for growth.

Construction Phase

This phase of crop growth generally starts in early April when the first node is detectable as stem extension begins. Canopy expansion accelerates in late April as temperature rise and the largest [yield contributing] leaves start to emerge.

During this period however root growth will also increase markedly by approximately 18mm/day! This is extremely important to support robust above ground growth (canopy expansion), ensuring uptake of less mobile [yet highly important] nutrients such as phosphorous (P), whilst also maximising root growth into the subsoil to improve water supply, both for the construction phase and later the production phase to aid grain fill, esp. if dry conditions prevails during this phase.

The construction phase ends at anthesis (flowering) during which time the following critical yield determinates would have been set:

• Final shoot number (at least 400 ears/m2)
• Root distribution (root growth slows after anthesis)
• Canopy architecture

These three physiological characteristics of crop form are critical to both resource capture and use efficiency, without one you cannot have the other!

The use of LimiN during the Construction phase

Exposure of plants to SAN as LimiN Technology has been shown to enhance root growth whilst also aiding tiller survival, both crucial during the construction phase. Whilst growth partitioning actively encourages a robust crop canopy that is less wasteful and more effective at capturing the natural resource (sunlight) that drives photosynthesise and crop yield.

Experiments at Myerscough College showing the effects of Stabilised Amine Nitrogen (using Elona with LimiN technology) on tiller survival in winter wheat on the 17th May:

Production Phase

This phase of crop growth occurs from approximately the second week in June, from flowering until harvest. During this period grain number per ear is set as florets [per spikelet] are fertilised. Heavy rain, heat and drought can potentially impair pollination at flowering reducing grain number.

After flowering rapid grain filling begins, starting at G.S. 71 (Grain watery ripe) and ending at about G.S 87 (Hard dough). Early canopy senescence due to stresses such as drought or disease can bring grain filling to a premature end reducing yield.

The use of LimiN during the Production phase

The use of SAN as LimiN Technology throughout the crop growth cycle to manipulate plant form via ‘growth partitioning’ will aid the production phase so that during the period when crops can potentially make the most of both sunlight levels and day length the crop should remain greener and potentially less susceptible to stress. This is due to the following characteristics promoted by the use of SAN:

• A frugal yet robust canopy architecture that maximises sunlight capture, whilst also minimising moisture loss.
• Leaf chlorophyll levels that are more efficient at processing the sunlight captured, and are therefore required to dissipate less excess light energy as heat, maintaining a cooler canopy which is both more energy efficient and less likely to succumb to stress.
• A root system that can mine the soil more effectively for nutrients and moisture.
• Shoot and spikelet numbers that the plant can fill during the production period.

Experiments at Myerscough College showing the effects of Stabilised Amine Nitrogen (using Elona with LimiN technology) on leaf chlorophyll index on 21st May:

Whether you are trying to increase yields through the targeted use of higher inputs above that provided naturally or manage crops through stress LimiN Technology is a tool that can be used to both support and manipulate crop form and optimise resource use efficiency.

4. The Elona Range

It is widely accepted that it is not always possible for crops to access the nutrients they require for optimum growth throughout their entire growth cycle due to soil or climatic factors that are outside of the grower’s control. Critical periods during their development can also leave them more susceptible to reduced yield potential if they are deficient in any essential nutrient or exposed to stress during these times. For this reason targeted applications of [soluble] topical nutrients are justified, for example, in high pH, calcareous soils, or soils rich in organic matter it is often common place to apply the essential micronutrients Manganese (Mn), Copper (Cu) and Zinc (Zn) due to soil lock up conveying poor availability to the crop. Whilst, as crops grow and canopy size increases [and especially if dry conditions prevail] the macronutrient Magnesium (Mg) may become an issue due to limitations on uptake and its importance to formation of chlorophyll and carriage of phosphorus within the plant (to name but a few).

The Elona range of foliar applied products incorporating ‘LimiN Technology’ has been formulated to supply the nutrients that are most often required by cereal crops in the UK, but unlike other products do so whilst also suppling SAN with the added benefits of ‘growth partitioning’. The Elona range consists of:

Elona (121g/l N, 22g/l MgO, 80g/l Mn, 5g/l Zn, 1.3g/l Cu)
Elona may be used at 1.5-3l/ha from the 3-leaf stage in the autumn with repeat applications as required or the following spring to encourage robust root and shoot growth whilst also addressing Mn, Cu and Zn deficiencies.

Elona Max (180g/l N, 84g/l K2O)
Elona Max may be used at 2-4l/ha from the onset of tillering in the autumn and/or in the spring to promote strong tiller development/survival.

Elona Top (135g/l N, 150g/l MgO, 15g/l Zn)
Elona Top should be used at 2-4l/ha where there is a requirement to maintain/enhance leaf chlorophyll and/or support tiller survival from early stem extension onwards.

Application Rates & Timing

The Elona range of products has been designed with favourable tank mixing characteristics to allow growers and agronomists the peace of mind that use on farm alongside other crop nutrients (if required) and crop protection products won’t compromise work rates and crop safety.

Catalyst Technology

In addition to LimiN Technology the Elona range of products also contains ‘Catalyst Technology’ which uses a unique natural growth stimulant developed by Levity that increases the crops capacity for growth and increases the speed of uptake and utilization of nutrients with which it is formulated.