Magnesium fertilizers 2

Magnesium Fertilizers.

Magnesium is often used as a turf fertilizer. Common options include Kieserite fertilizer, Magnesium sulphate fertilizer and Magnesium oxide to manage Magnesium deficiency in plants. But which of these is the best option to address any magnesium deficiency? How do you know what is the best magnesium fertilizer to use in specific soil conditions?

The form of Mg fertilizer has a big effect on the results you get in a fertilizer strategy. For example, in soluble forms the tank compatibility of these varies dramatically.

The Role of Magnesium In the Plant.

The leaves of turfgrass on average contain around 2.1 g/kg (ppm).¹Waddington, DV. and Zimmerman, TL. 1972. Growth and chemical composition of eight grasses grown under high water table conditions. Communications in Soil & Plant Analysis 3(4):329-337.

There are far higher levels of Calcium and Phosphorus in turf but this is about the same as the Sulphur content.

In reality there is a strong suggestion that in turf Magnesium may often be highly deficient due to the sufficiency level on average being greater than 2 g/kg.

• Magnesium (Mg2+) is important for the health, growth, and vigour of turfgrass. It is integral for photosynthesis as it is for chlorophyll formation.

• The pigment in plants that absorbs light is called Chlorophyll. Chlorophyll absorbs blue and red light waves and reflects green light waves, and is what gives plants their green colour.

• Magnesium is the central atom of chlorophyll, although only a fraction (25%) of the total Magnesium is bound to chlorophyll. The balance (about 70%) remains relatively mobile in the plant, and is present in plant sap.
• Magnesium influences over 300 enzymes in turfgrass.
• The uptake of nutrients like N and P needs Magnesium to occur efficiently.
• Magnesium improves the transport of P in turf. 
• Recent research, shows the importance of Magnesium²Rengel, Z, Bose, J, Chen, Q, Tripathi, BN. (2015). Magnesium alleviates plant toxicity of aluminium and heavy metals. Crop Pasture Sci. 66, 1298–1307. doi: 10.1071/CP15284 in improving plant tolerance against several environmental stressors.

Symptoms of Magnesium Deficiency in plants.

Magnesium Deficiency in turfgrass.

Table of Magnesium Nutrient Antagonism³René PJJ. Rietra, Heinen M, Dimkpa CO & Bindraban PS (2017) Effects of Nutrient Antagonism and Synergism on Yield and Fertilizer Use Efficiency, Communications in Soil Science and Plant Analysis, 48:16, 1895-1920, DOI: 10.1080/00103624.2017.1407429.

Soil type.

When does Magnesium Deficiency occur?

The following conditions inhibit Magnesium uptake:

• Excess irrigation or heavy rainfall.  
• Sandy and low CEC soils.
• After you apply high rates of lime.
• In acidic (low pH) soil. Low soil pH soils lock up Magnesium as it reduces Magnesium solubility. This makes it less available
• High rates of potassium fertilizer.
• In cold and wet weather.
• When you box off clippings this leads to a gradual fall in soil levels of Magnesium. 

When to Use a Magnesium Fertilizer:

• When soil Magnesium levels are low.
• When the existing soil pH is high, or you use lime to address low pH soils.
• You use ammonium Nitrogen. This can cause an antagonism between the ammonium and the Magnesium.
• If the soil is compact. 
• In periods of wet/cold weather it can lead to lower mobility of Magnesium in the soil.

Common Magnesium Fertilizers.

To decide on which Magnesium fertilizer to use you must know their specific characteristics. These can be quick-release soluble salts such as Magnesium sulphate fertilizer and Magnesium nitrate or slow-release forms like Magnesium oxide.

Quick-release Magnesium Fertilizers.

• Magnesium sulphate fertilizer, in the form of Epsom salts (10% magnesium).
• Magnesium nitrate (11% magnesium).

Epsom salts contain 10% magnesium and are also known as Magnesium sulphate fertilizer. It is highly soluble and prevents and corrects any Magnesium deficiency in plants. However, due to its high solubility, it tends to leach, especially on sandy soils.

Magnesium nitrate contains 10% nitrogen and 11% magnesium. When you use Magnesium nitrate as a foliar it is an ideal way to deliver Magnesium and nitrate-N.

In fact you can reduce rates by 30 to 50% in comparison to Epsom salts (Magnesium sulphate). It is sulphate-free, and does not have issues with tank compatibility.

However, due to its high solubility this tends to rapidly leach rapidly out of sandy soils.

Use of Foliar Magnesium.

Medium-release Magnesium Fertilizers.

• Kieserite fertilizer (16% magnesium).
• When Magnesium is in the chelated form it is bound to an organic molecule. This makes it more readily available for plants, and is especially the case in high pH soils.

Kieserite fertilizer, a less soluble form of Magnesium sulphate, and is pH-neutral. It does not acidify the soil.

Slow-release Magnesium Fertilizers.

•  Calcium Magnesium carbonate, known as dolomitic lime. This contains 3–12% Magnesium.
• ,Granomag® which is Magnesium oxide, contains 57% magnesium.

Granomag contains 57% Magnesium as Magnesium oxide and is often in fertilizer blends. However, it is insoluble, and not readily available to the turf as it takes so long to break down.

The other disadvantage is due to its large particle size. It is no good to use on close cut turf, such as greens. However it’s fine to use during renovation after hollow tine aeration if you work it down the tine holes.

Why Use Kieserite Fertilizer?

• It produces a consistent supply of Magnesium.
• The release pattern of Kieserite fertilizer matches turf demand.
• As Kieserite moves down through the soil profile, it optimizes uptake.
• It is user-friendly. It is available as a granule or a fine powder.