Not essential to plants, very valuable for animals
Sodium is a useful element because it does not meet the criteria of a plant nutrient, since plants can complete their life cycle without sodium and its function can be replaced by plant nutrients. Nevertheless, sodium is a valuable component of plants used for animal nutrition. Sodium promotes basal feed performance and keeps animals healthy and fertile. In the plant, sodium – similar to potassium – regulates the osmotic pressure of the cells and leads to more efficient water utilization.
Sodium has a high propensity to be leached
Sodium is found in the soil only in a bound state, predominantly as salts.
In areas with humid or semi-humid climates, only little sodium is present in the soil, as it can be very easily washed out with rainwater into deeper soil layers. Sodium is less well retained on clay minerals than the potassium ion.
In arid or semiarid areas, on the other hand, Na often accumulates in the topsoil as increased evaporation causes water to move upward. Here, soil structure often deteriorates, negatively affecting water and air balance. Likewise, the pH value increases with increasing Na content.
Sodium in relevant for sugar beets and has similar functions as potassium
Sodium does not fulfill the criteria for a plant nutrient because plants can also complete their life cycle without sodium and it can be replaced by plant nutrients for the function it performs (e.g. by potassium in osmosis). However, it is a valuable constituent of plants used for feed. Sodium is one of the beneficial elements.
- One exception is natrophilic crops (e.g. Chenopodioideae) – Positive effects on yield and quality from the application of fertiliser with sodium can be demonstrated. Sugarbeet as the most important crop species in this group is well known example which has a relatively high sodium requirement. Sodium supports the synthesis of glucose and its conversion to fructose which is stored in the beet.
- Sodium controls osmotic pressure in plant cells and results in a more efficient use of water.
- Na ions can often substitute K ions in some metabolic and osmoregulatory functions and therefore the two nutrients are interchangeable to varying degrees according to plant group
- Sodium is important for some C4 plants (e.g. amaranth) for CO2 uptake
In animal nutrition, sodium plays a key role for health and productivity
- In animal nutrition, a sufficient supply of sodium is an important factor in maintaining the productivity of the animals. Sodium deficiency results in loss of appetite, decreased milk production, weight loss, and has implications for health and fertility of the animals.
- Approximately 2g Na kg-1 DM in the basic ration is necessary to satisfy the daily requirement for Na in dairy cattle. Field studies have demonstrated that in many regions the average sodium content of grassland is only at 0.1-1g Na kg-1 DM and therefore clearly below the required amount.
- Sodium containing fertilizers such as Magnesia-Kainit have been successfully used for over a century for greatly increasing the sodium content of grassland and can guarantee meeting the Na demands of the animals.
- Studies and trials have demonstrated that besides an improved Na supply from the nutritional point of view, the increased sodium also has a major effect on palatability of forage which can increase dry matter intakes by around 10%.