Author: Rob Dwyer – IPF Tropical Systems Agronomist

Improving nitrogen (N) management on-farm using an ammonium stabiliser like eNpower® has benefits beyond reducing the potential for N losses.

Ammonium stabilisers can effectively manage the N loss pathways – leaching, denitrification and runoff – making more N available to grow better crops with more yield (Figure 1).

However, eNpower provides more than just a N advantage. Ammonium stabilisers are renowned for their ability to improve N use efficiency. eNpower works by keeping more N in the ammonium form for longer than usual. This stabilisation timeframe can last weeks and even up to three months.

Figure 1: Ammonium stabilisers reduce the potential for N losses and improve N use efficiency. eNpower can also improve energy efficiency balances for crops.
Source: Trenkel (2010).

Ammonium stabilisation with eNpower and crop energy efficiency

eNpower extends the period that ammonium nitrogen (NH4+) is available to crops. Greater access to ammonium leads to the multifaceted process referred to as Partial Ammonium Nutrition (PAN).  Several of these PAN processes can happen at the same time, helping to improve crop quality and yield. Greater N use efficiency is a more obvious driver of improvement, but what about better energy use by crops? 

How crops use less energy

Firstly, it is less energy demanding for a crop to take up NH4+ than nitrate nitrogen (NO3–), particularly when crops are provided with higher amounts of ammonium (Pasda et al. 2001). Ammonium is simply a more energy efficient N form for crops to utilise.

For plants, and all other living things, the provider of energy at a cellular level is the ATP molecule (Adenosine Triphosphate). ATP is the ‘currency’ of energy transfer for plant cells. ATP efficiency facilitates crop energy efficiency,

What drives ATP energy influence?

Plants don’t directly use NO3– – it must be converted to other N forms before it can be used by crops. In comparison, NH4+ can be used directly without being converted. The consequence of this is NO3– nutrition is a more energy intense process as it consumes 12 ATP, as opposed to ammonium-N nutrition which only consumes two ATP (George, et al., 2016).

On a molecular level, this is a six-fold difference, making significantly more energy available for other plant physiological processes with partial ammonium nutrition, compared to nitrate uptake. Ammonium is that much more efficient N form, and more energy efficiency can lead to better crop productivity.

It may sound like this would not make much of a difference, but the reality is a crop’s root system (the below ground parts) is in a constant ‘energy battle’ with a crop’s shoot system (the above ground parts). Crop performance is constantly influenced by the ever-changing energy demands between these two intra-plant systems. Any assistance to better match or balance these demands, especially for the root system, is beneficial.

It is the green leaves of the above ground system, that capture solar radiation and atmospheric carbon dioxide to initially create simple sugars. These sugars are used for energy demands, amongst other things. Distance and flow dynamics often challenge root systems to be able to access and compete for sufficient and timely energy, as demanded by the below ground parts. Often the shoot system and above ground parts win this tug-of-war. Additionally, nutrient and water demands must also be balanced appropriately. With conventional N nutrition, the dynamics of the processes and the linkages between each; natural plant hormones, sugars and nitrogen are represented in Figure 2.

Figure 2: A schematic representation of ‘conventional’ (i.e. not PAN) nitrogen nutrition on the multi-layered root-shoot-root signalling circuits in balancing carbon and N between a crop’s ‘below ground’ and ‘above ground’ systems. The solid blue lines and their length indicate a far greater mass flow and signalling interactions for N towards the above ground plant system as opposed to the below ground system, with ‘conventional’ nitrogen nutrition. The figure represents sugar (green), nitrogen (blue), cytokinin (yellow), auxin (dark red) and both xylem signalling peptides (C-terminally encoded peptides, CEP’s) and receptor protein (Clavatav, CLV) in the phloem.
Source: Wang & Ruan, 2016.

The dark blue, solid arrows and their length in Figure 2 visually highlight the more favoured N access of non-PAN N for the above ground plant systems (i.e. shoot N) compared to the below ground plant system (i.e. root N) sinks.

Enabling longer PAN allows root systems to better access the more energy efficient ammonium-N form to assist in pushing energy balances in favour of root systems.

After all, it is the root system that anchors plants within the soil; performs the vast majority of nutrient uptake; drives water acquisition and uptake; and defends the plant against subsoil constraints and soil pathogens. Healthier root systems drive crop performance and partial ammonium nutrition drives improved root systems.  

This fundamental balance shift due to PAN influences is another reason why eNpower delivers greater crop performance improvements above and beyond that of solely being more than just a N advantage.

eNpower options

eNpower is available on multiple N products from Incitec Pivot. Straight fertilisers that can be treated with eNpower include urea, GranAm, MAP, DAP, Granulock Blue, Granulock Z and Easy N.

These can then be used in fertiliser blends to achieve an eNpower advantage.

eNpower + Easy N provides the flexibility and convenience of using N through fertigation as traditional Easy N liquid fertiliser, but now with the advantage of eNpower.  eNpower + Easy N is designed as a soil applied fertiliser. Do not use eNpower + Easy N for foliar applications in any crops.

All these fertiliser options provide greater scope to use eNpower throughout more of a crop’s growth cycle by providing greater flexibility in use opportunities. 

Summary

  • The advantages of eNpower use are much broader that just benefiting the availability of a single nutrient such as N. eNpower and improved energy balances can improve crop performance and yields. 
  • Consider eNpower treated fertiliser in your next nutrient program.  
  • Discuss the eNpower advantages with your local IPF supplier.  

Further Information

For more information on using eNpower, contact IPF Tropical Systems Agronomist Rob Dwyer on 0428 111 471 or email rob.dwyer@incitecpivot.com.au. 

References

Marschner H and Romheld V (1983). In Vivo Measurement of Root-Induced pH Changes at the Soil-Root Interface: Effect of Plant Species and Nitrogen Source. Zeitschrift für Pflanzenphysiologie, 111, 249-251. 

Pasda G et. al. (2001). Effect of fertilizers with the new nitrification inhibitor DMPP (3,4-dimethylpyrazole phosphate) on yield and quality of agricultural and horticultural crops. Biology and Fertility of Soils. 34, 85-97. 

Trenkel ME (2010). Slow- and Controlled-Release and Stabilized Fertilizers – An Option or Enhancing Nutrient Use Efficiency in Agriculture. International Fertilizer Industry Association. 

Wang L and Ruan Y-L (2016). Shoot-root carbon allocation, sugar signalling and their coupling with nitrogen uptake & assimilation. Functional Plant Biology. 43, 105-113.