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Micronutrient seed priming – Is it pocket friendly than soil and foliar applications?qrcode

Oct. 12, 2018

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Oct. 12, 2018

Micronutrient seed priming – Is it pocket friendly than soil and foliar applications?

Crop plants require nearly 17 essential elements for optimal growth and development. When these minerals are required in relatively high amounts, they are called macronutrients and in trace amounts as micronutrients. While micronutrients are required in relatively smaller quantities for holistic plant growth, they are as vital as macronutrients. If even one of these elements is lacking in the soil or not adequately balanced with the other nutrients, it may result in growth suppression or even complete inhibition. Micronutrients often act as cofactors in enzyme systems and participate in redox reactions, in addition to having several other vital functions in plants. But most importantly, micronutrients are involved in the key physiological processes of photosynthesis and respiration and their deficiency can choke these vital physiological processes and thus impacting yield gain.

‘Hidden hunger’ or mineral deficiency in edible food grains is a major health concern in a majority of developing countries. For example, dietary Zinc (Zn) deficiency may result in loss of immunity, poor wound healing and even dermatitis. Whereas an adequate amount of Zn nutrition helps to improve resistance to some infectious diseases such as diarrhea and increase immunity.

Micronutrients are vital for both plant growth and human health. While, foliar and soil applications are the most prevalent methods of micronutrient addition, the initial cost involved and difficulty in obtaining high quality of micronutrient fertilizers are quite costly, which are important factors especially in developing countries.

Enhancing plant micronutrient status in circumstances where micronutrient nutrition is inadequately supplied from the soil has proven to increase yield. However, this requires application of higher doses of fertilizer to soils too because of low nutrient-use efficiency. In crop plants, micronutrients may be supplicated to the soil, foliar sprayed or added as seed treatments. Although the required amounts of micronutrients can be supplied by almost any of these methods, foliar sprays have been most effective in and grain enrichment and yield improvement. However, the high cost restricts a wider adaption, particularly by resource-lacking farmers. Plus, foliar application occurs at a later growth stages when crop stands are already established. On the other hand, micronutrient seed treatments, which include seed priming and seed coating, are an easy and cost-effective alternative.

Hence, seed treatment is a wiser option from an economical perspective as only a small amount of micronutrient is needed, is easy to apply and the seedling growth is improved.

Seed priming

Seeds can either be treated with micronutrients or by soaking in nutrient solution of a specific concentration for a specific duration or even by coating with micronutrients. Seed invigoration is a relatively new term and is interchangeably used for two methods of seed treatment:

Methods of seed priming

In seed priming, seeds are partially hydrated to initiate metabolic events to take place without actual germination, and then dried again (near to their original weight) to allow routine handling. Such seeds germinate much faster than non-primed seeds. In micronutrient seed priming (nutripriming), micronutrients are used as osmotica. Primed seeds usually have higher chance of a synchronized germination owing simply to a less imbibition period and build-up of germination-enhancing metabolites.

The four most common methods of Seed Priming are:

1) Hydro Priming – Hydro priming is a technique for initiating germination without the emergence of the plant. It involves soaking the seeds in a priming agent solution followed by drying. This technique accelerates germination significantly and reduced the time required for plants to emerge. It also improves the seed vigour.

2) Osmotic Priming – In this technique, controlled hydration of seeds to a level that allows pregerminative metabolic activity but inhibits radicular emergence. It is achieved by immersing seeds in an aqueous solution of a chemically inert but osmotically active compound. The osmotic potential is adjusted to allow all the pre-germination processes while impeding cellular prolongation and plant emergence, even after weeks of contact between the seeds and the osmotic solution. This method increases the uniformity of germination and emergence seedlings to establish more rapidly in a field and the planning and allows for execution of cultivation and harvesting to be easily facilitated.

3) Solid Matrix Priming – In this method, the water uptake is controlled by suspending the seed in a defined medium (or matrix) of solids (which can be organic and/or inorganic) whose water holding properties are known. The seed and the matrix then compete for the available water, coming to an equilibrium at precisely the right point for seed priming to occur. The aeration and temperature are controlled with precision throughout the process. After the process is complete, the seed and matrix are separated and the seed is re-dried. It is perhaps the most versatile form of seed priming and less risk prone.

4) Bio Priming - Bio-priming is a new technique of seed treatment that includes biological (inoculation of the seed with beneficial organism to protect the seed) and physiological aspects (seed hydration) for disease control. It is often used as an alternative method for controlling many seed and soil borne pathogens which can result in undesirable effects on plants.

For e.g., with an increases in the soil’s pH level, Zinc’s (Zn) solubility in the soil and its uptake decreases concomitantly. Similarly, in several crops, the higher soil phosphorus (P) contents may induce Zn deficiency. Poor growth and small brown spots on leaves are common symptoms in rice and maize plants grown on Zn deficient soils. Seed priming with Zn can help improve crop emergence, stand establishment, and subsequent growth and yield.

Advantages and effects

Seed priming is also more cost effective compared to soil application with significant savings, it is sensitive and can be affected by various environmental variables and other factors. Oxygen levels, temperature and water potential are amongst the most important factors that impact seed priming.

Even after seed priming with Zn, crops have shown to have no effect on the grain yield and sometimes resulting in even complete crop failure. This is possible due a lack of testing and optimizing the priming levels. Instead, it is wiser to optimize micronutrient seed priming levels in the laboratory and then test in soil for germination prior to priming the entire batch.

Similarly, other factors such as regulating the oxygen supply during seed soaking can improve the effectiveness of the process. There is a substantial difference in the performance of aerated vs. non-aerated solutions during seed priming. Provision of aeration (oxygen) improves seed performance upon sowing.

The temperature of the priming media also impacts the effectiveness of seed priming. For example, low temperature during priming can delay the physiological processes of germination, even though seeds absorb water in optimal amounts.

Overall, there is massive potential of micronutrient seed treatments for enhancing crop growth and grain nutrient enrichment. Micronutrient applications through seed treatments improves the stand establishment, advances phenological events, and increases yield and micronutrient grain contents. Being an easy and cost effective method of micronutrient application, seed treatments has emerged an attractive option for resource poor farmers.

Seed treatment with micronutrients has the potential to address crop micronutrient requirements, enhance seedling emergence, yield, and grain micronutrient enrichment. Seed priming or seed coating, are pragmatic, inexpensive and an easy alternatives of micronutrient delivery especially by small landholders in developing countries. Variation exists within crops and varieties/genotypes/hybrids which researchers are actively working on to:

1. Develop precise techniques using a range of micronutrient sources at varying concentrations and durations

2. Optimizing the temperature range, oxygenation requirements and water potential for maximum benefit

3. Using commercially-available fertilizers for seed coating and priming osmoticum appraising large-scale field trials of using nutriprimed seeds

4. Enhancing the storage potential of nutriprimed seeds, which may be critical for technology transfer in the future

About the author:
Mr. Viejay Bhatia is the director of AVA Chemicals.
AVA Chemicals have been formulating and providing premium-grade chemicals to national and international clients in over 40 countries. In time, AVA Chemicals has progressed to become an accredited supplier of organic chemicals among its other offerings. With a solid value chain in place, AVA Chemicals is a trusted provider for leading Agrochemicals companies such as Aries Agro, Nagarjuna, Coromandel amongst many others. It aims to be known as an ethical company providing specialty chemicals to companies who manufacture products that are used in day-to-day life, thus touching the lives of millions of people.

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