Grass is the cheapest source of energy for deer. But managing the grassland to optimise nutritional content of the grazing land, or more crucially forage, takes time and effort. Asking the right questions is the key.

Creating a plan to produce forage that has a high nutritional content needs to be created from an in-depth understanding of the available nutrients in the soil, and then correlating that information with a tissue test to confirm exactly what nutrients are available in the forage. Appropriate supplements can then be provided to ensure that deer growth is optimised.

The most crucial action in relation to soil nutrition for producing forage is to measure the nutrients in the soil that are actually ‘available’ to the plant. Rather than as in the case of the Standard Soil Test, which just measures the quantity of nutrients that the soil contains.

Many nutrients are inescapably bound into the soil colloid by their interaction with the other nutrients and the fundamental soil configuration. This consequently renders them unavailable for plant utilisation without the crucial soil fungi (Arbuscular Mycorrhizal Fungi), and significantly contributes to poor quality forage

Just to recap on the key nutrients tin the soil to balance, and therefore the nutrition available in the grass that is harvested.

Magnesium (Mg)

Magnesium regulates the uptake of Phosphorous; structural component of ribosomes; major constituent of chlorophyll production; and plays a crucial part in transforming sugar and starch within the plant to utilisable energy.

Magnesium is also a crucial component of nerve and muscle function in all creatures. Hence animals that are short of this nutrient tend to be hyperactive and unpredictable.

Once magnesium has been broken down from the parent soil material over the millennia (e.g. dolomite) it is deposited in the soil solution.

The Magnesium in the soil solution can only be depleted in three ways:

  • Absorbed by living organisms – used for productivity.
  • Adsorbed by surrounding particles – rendered unavailable without appropriate intervention.
  • Leached – as a result of applications of fertilisers containing sulphates and excessive use of chlorides (e.g. Muriate of Potash – MoP)

Soils that naturally contain a high level of magnesium are difficult to manage. The magnesium ions naturally swell and absorb water weakening the structures that hold the soil particles together and generating an anaerobic glutinous consistency in the soil that further reduces infiltration rates and hydraulic conductivity – drainage.

Under these circumstances both plants and soil microbes struggle to survive, and valuable yield and productivity will be lost during the season.

Plants grown on high magnesium soils invariable suffer from a lack of stem strength and often collapse after inflorescence (flowering). This is due to the lack of calcium available from the soil.

To manage a high magnesium soil for productivity:

  • Regularly incorporate organic matter which will increase the aggregate stability of the soil, while progressively slowing down the soil degradation.
  • Incorporate calcium into the soil. Calcium helps to flocculate the clay and magnesium particles creating a greater aggregate particle size which will increase the infiltration of air and crucially allow water to drain through the soil rather than coagulating it.

Calcium application options:

If Gypsum can be accessed and incorporated this would provide the necessary calcium levels as well as sulphate and is cheap if locally available from plasterboard production facilities. Alternatively, regular applications of Calciprill / Calcifert [prilled limestone] can be applied in a form that can easily be spread from any fertiliser spreader – give us a call if you need help calculating rates.

Soils in the United Kingdom often have a low calcium level. This is NOT strictly related to the pH of the soil but relates to the soil function.

Calcium (Ca)

Calcium is an integral part of all cells, and the major constituent of the middle lamella which is formed during cell division.

Calcareous soils break down and create the large regions of the UK have high concentrations of limestone or chalk. In these situations, the high calcium levels will significantly benefit the grass development, but also restrict the availability of other crucial nutrients – especially potash and magnesium. Conversely, available calcium will increase the absorption and efficiency of nitrogen utilisation.

Only young roots are able to absorb calcium, and translocation will be dependent on available soil moisture. Calcium plays a significant role in muscle contractions within animals, and a shortage will lead to cramp. In extreme cases the autonomous peristaltic function within the gut can stall, with the obvious dire consequences.

Phosphate (P)

Available phosphate stimulates root growth, and energy production, and also plays a key role in grass palatability.

In the soil, phosphates are subject to rapid and complex antagonistic interactions with calcium, magnesium, iron, and manganese, which makes phosphate relatively immobile for root recovery.

But, by encouraging Arbuscular Mycorrhizal Fungi (AMF) development with aeration will help liberate phosphate. AMF produces significant levels of glomalin protein that is specifically designed to release phosphate from the soil for plants to utilise

Potassium (K)

Potassium crucially drives and regulates the Transpiration process: the movement of dissolved nutrients in water (sap) up the plant to sites of utilisation

Potassium significantly contributes to many of the plants physiological processes, as well as regulating the plants respiration rate. Also, available potassium facilitates the synthesis and translocation of carbohydrates within the plant which ensures that the cell walls thicken correctly, and the plant remains standing.

Potassium combines with boron and calcium within the plant to allow the correct development of cell walls.

One of the most notable advantages of available potassium is that it is integral to increasing the hardiness and winter survival of young grass plants. This hardiness also confers an increase in general disease resistance for the life of the plant.

Grazing grass is inherently shorter that grass destined for winter keep. Therefore, the requirement for potash is low. This is because the potash moves the nutrients up the plant to ensure that the ear (seed head) has enough energy to promote the grasses genes. Grazing grass will function perfectly adequately on low potash levels, but care and attention must be taken to ensure that is to be harvested has access to adequate levels of potash.

Care must be taken to ensure that potash applications are disproportionate to available magnesium levels, as the high potash will induce Grass tetany.

Grass tetany occurs when the ungulates diet is too high in potassium. This consequently means that the extra cellular fluid stays permanently high in potassium. This upsets the delicate sodium / potassium ratio in the nerve channels and as a consequence the nerves and muscles cannot relax, creating restless hyperactive animals that lack body condition and display a lack of ability to increase weight despite access to good grazing grass..

These points highlight the importance of ensuring that the forage crop has access to potassium to maximise both nutritional quality and yield.


When to harvest grass?

The schematic above demonstrates the difference between dry matter (DM or the volume of crop harvested) at various timings, and the nutritional content of the harvested grass, the D-value (digestibility related to nutrient content), at that timing.

In essence the plant wants to promote its genes by ensuring the seeds have as much nutrient as possible, so that they will ripen and survive once scattered on the soil.

Therefore, if we calculate the flowering date of the grass (dependant on the sward species mixture) and consider the fourteen days before that date. Those 14 days up to flowering are when the plant contains the most nutrition for grass conservation as hay / haylage / silage.

Dry hay is harvested at 15 per cent moisture

Always tricky to achieve with the variable British weather! But given the opportunity this will be the cheapest way to conserve grass. Optimised cutting and wilting will need to be adhered too, with the obligatory extended length of the wilting / turning process often precluding hay production. The longer the wilting process that is required extends the risk of rain ruining the wilting grass.

Haylage is harvested at 50 to 60 per cent moisture

Haylage is grass forage that is cut just before flowering, wilted, and baled when it is at a 50 to 60 per cent moisture content, and then stored in a sealed plastic wrap. It is imperative that all air is excluded so that the natural fermentation process can take place within the bales. Assuming that harvesting and wilting process have been optimised, then it is advisable to double wrap the bales to ensure the longevity and quality of the ensiled grass.

Silage is harvested at 50 to 60 per cent moisture

Apply the same criteria as for haylage, but the harvested crop is stored in a clamp. Again, it is imperative that all air is excluded so that the natural fermentation process can take place. Ideally with double sheets weighed down with unusable tyres. Rats and birds must also be controlled to ensure that they do not make holes in the plastic and allow air in which encourages the proliferation of crop spoiling organisms.

Get in touch for further help on creating nutritious hay, haylage
or silage for deer and other animals.