In this Part II it shows how does Magnesium deficiency looks like, how to resolve this Magnesium deficiency problem and when & where to apply Magnesium.
The most serious concern is very High levels of nutrient imbalance caused by use of fertilizers without following recommended practices of universities and ICAR. Farmers are falling in to the trap of dealers, quack doctors and highly unprofessional and incompetent consultants suggesting use of nutrients in a very highly unscientific way. The mistakes normally done by farmers are
Addition of no or low amounts of organic manure
Indiscriminate use of DAP and MOP without proper soil test. Calcium and ammonium in DAP seriously compete with magnesium and makes it difficult for plants to take up magnesium.
No practice of magnesium application. Seriously saying there is no recommendation of magnesium available for different crops.
Very unfortunate use of equal amounts and very frequent application of N, P and K like water soluble fertilizers like 20:20:20., 19:19:19, 18:18:18 etc.
No care and forgetting intentionally of otherwise magnesium while applying high levels of potassium and lime.
Drip irrigation systems supplying water continuously lead to leaching of magnesium from the root zone. Roots of drip irrigated crops gets restricted to wet zones as water is made available continuously. Roots also become lazy and do not grow beyond the wet zone. This leads to exploitation of only wet zone soil leading to magnesium deficiency.
Natural soil conditions such as, low soil pH and dry soil conditions, sandy soils reduce the availability of magnesium. Under such conditions, magnesium deficiency is more likely.
It is not that other deficiencies are not there. But farmers are applying all such elements either through soil application or through foliar application. Magnesium is not so. Even manufacturers of micronutrient mixtures do not use magnesium sulphate as feeler material as It is hygroscopic. Hence magnesium application is ignored from all angles.
In all farmers fields some or all of these are responsible. So magnesium deficiency is emerging in all farmers fields. Today it may be a hidden deficiency and tomorrow it will show up symptoms and become severe in all the fields.
How does magnesium Deficiency looks like
First symptom is leaves start losing green colour and turn yellow from the tips of old and middle leaves. Gradually it starts expanding along the margins and spreads towards mid rib and shows an inverted “V” shape. The veins mostly remain green and the interveinal region becomes yellow and in some plants small brown dead spots also appear.
When do we feel magnesium is needed by crop
First think over what mistakes you have done in management like are you growing very high yielding crop varieties without caring for magnesium., are you having ultra high density planting, liming, continuous use of DAP, MOP, 19:19:19 like fertilizers, excess of calcium and potassium or other reasons like growing crops off season, soil condition etc. In that case you have to consider magnesium application to crops.
How to know how much magnesium to apply?
Before sowing/planting go for soil test and apply magnesium based on soil test report. If your soil tests less than 125kg Mg/ha then apply 100 kg magnesium/ha. If your soil tests between 125 to 375kg Mg/ha then apply 50 kg magnesium/ha. If soil test is above 375kg Mg/ha then there is no need to apply magnesium.
Where do we get magnesium? Sources of magnesium?
Magnesium sources are many. But the cheapest are dolomite, Epsom salt, magnesium oxide, SOP magnesia and even irrigation waters contain sufficient magnesium in some places.
If field deficiency is seen then It is better to go for leaf analysis for mid term correction through foliar spray. When the tissue concentration falls below critical level then go for foliar application of magnesium at the rate of 0.2 to 0.5% magnesium sulphate
The best way is to get leaf tested. Let us see normal magnesium concentration in some plants.
Cabbage Outer rapper leaf0.4 to 0.7 per centTomato, potato, brinjal and chilli Fourth leaf from top.0.3 to 0.6 per centMaize Flag leaf 0.2 to 0.4 per centWheat Whole plant top 0.15 to 0.5 per centCotton 5th topmost leaf 0.15 to 0.25%Soybean and other food legumes Middle trifoliate 0.25 to 0.8 per centGrapes Young leaf petiole 0.3 to 0.4 per centMango 4 months old leaf 0.3 to 0.5 per cent
If soil is highly acidic then take up foliar spray of magnesium. During severe winter months also take up magnesium foliar sprays at the rate of 2 to 5 kg magnesium sulphate per 100 liters of water.
If you have any further query then please contact soulofkrishi.com
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