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Seed Nutrition – Seed Covers

Evidence is accumulating to show that the nutrient reserve within or placed directly on a seed greatly affects a seedling’s ability to withstand various environmental stresses; that seeds containing low reserves of zinc, manganese and copper have lower resistance to root pathogens, water stress, cold temperatures and acidic soil conditions; and, that the most important factor determining the mineral nutrient reserves in a seed is the nutrient availability to the mother plant during reproductive development.

There was a recent question put to out to our network by agri-coach Richard Limoges, owner of High Performance Agronomy at McLennan Alta., which should make us all think: “If we measure soil nutrient levels to determine a fertilizer plan, and many of us use a tissue test to check up on our crops, can’t we do the same thing with the seed? What kind of information would that give us? How could we use it?”

From research, we know that several macro and micronutrients play critical roles in the germination and early development of the seedling, particularly when germinating seeds or seedlings are facing abiotic and biotic stress. Let’s quickly review a few of the commonly recognized important “early” nutrients:

Zinc (Zn) is needed to orient the radical (the first root) and stem, it is involved in many enzymatic reactions, there is a high Zn content in all meristematic tissues (areas of growth) and it is required to maintain bio-membranes.

We need some calcium (Ca) to help seedlings build cell structure.

Boron (B) is required for cell differentiation. Boron could go on later, but in cereals, if we want to influence the size of the head, it needs to be in place before the three-leaf stage, so logistically it is easier to apply with the seed. Even on brassicas and legumes, boron is better early.

Manganese (Mn) is involved in activating a large number of enzymatic systems, so any lack slows down plant function. Mn is also involved in lateral root development and the more roots we can produce, the better the health of the plant. Mn is another nutrient that is more effective the earlier it is applied. As senior agri-coach Dr. Ieuan Evans points out, in soils high in manganese, most of it is available in the +4 form while the plant wants +2; so we can get a response with an early Mn application, particularly in high pH soils.

There is lots of research supporting the importance of available phosphorus (P) in early seedling development, especially as P is not very mobile so it is a good idea to have lots of feeding sites close to the seed. More recently, we have learned that some of this early P should be in the phosphite form.

Early development

Here’s an analogy to help hammer this discussion home. In western Canada, most crops have 90-120 days in which they grow from a tiny seed to a mature plant. A baby born today can expect to live 90+ years. The first few years of a child’s life are critical developmentally. In these first few months and years every child’s physical and mental potential is set. Same for the crops we grow! Imagine providing inadequate nutrition to a child for the first six years of its life. Not enough iron (Fe), protein, magnesium (Mg) or Calcium (Ca), what would that do to the child’s potential? The genetics would be there but the expression of those genetics would not be possible because of the early shortage. A tragic situation, right? Same for the crops we grow.

In my opinion, a seed test for nutrient concentrations, or quantification of seed nutrient density, would provide another important piece of the puzzle from which we can connect more dots that allows better decisions and more consistently high yielding crops.

Ramifications of seed nutrient density

Seed nutrient density has ramifications in fine-tuning our fertility program. If the seed we are planting has a low nutrient density, then we can adjust our fertility program to offset any early nutrient shortages. We can accomplish this through seedplaced nutrients (beside the covers), seed priming (on the covers), fertilizer impregnation or selecting nutrient dense seed (under the covers).

If nutrients are low in the seed, then nutrients placed close to or on the seed help ensure adequate nutrition for germination and emergence. Plants take up a high percent of their micronutrient requirements during the first third of the growing period. Therefore, it is important to apply these micronutrients before or at planting to get maximum benefit.

If the harvested seed is low in nutrients, protein or oil, then we need to adjust our fertility program and use tissue tests to check on crop uptake and nutrient availability.

Agri-coach Gerald Anderson, owner of AgAdventure Consulting Services out of Coaldale AB says, “Most of my customers have a liquid kit on their drills so we can dribble liquid P in the seedrow to optimize our feeding sites, and carry at least some zinc and boron. In fields where we see the need, we are now adding manganese.”

Seed nutrient density also has implications for seed sale transactions. Which seed would you rather plant? A nutrient dense seed that is able to take care of its own needs or one low in the nutrients essential to speeding robust germination? Select seed that is high in P, Zn, B, Ca and Mn. Remember some of P should be in the phosphite form.

With the change in marketing options, there is the potential for markets that will pay for nutrient density/oil content. As sure as I’m sitting here, this will happen for Canadian growers. How do I know this? It’s already happening all around the planet.

Why this is becoming more important

Increased yields means increased nutrient requirements and nutrient removal from the soil. Enhanced water use efficiency (WUE) and fertilizer use efficiency (FUE) makes for ever bigger crops, but usually with less concentrated nutrients (environmental dilution). In addition, plant breeders striving for increased yields concentrate on increased carbohydrates or oil without a focus on overall nutrient density, resulting in low nutrient concentrations (genetic dilution).

There is historical data that proves this. Between 1938 and 1990, protein in wheat and barley declined by 30 to 50 per cent. Moreover, since 1873 key minerals in hard red wheat have declined. Over the 130-year period, genetic gains in the yield of U.S. HRSW wheat have tended to reduce seed iron, zinc and selenium concentrations. Iron content dropped by about 28 per cent, while zinc dropped by about 34 per cent and selenium by about 36 per cent.

Biofortification is a new term bantered about, usually in the context of genetically engineering a crop to produce a product with a higher nutrient content. However as farmers, we can “biofortify” crops naturally by using a balanced fertility program and connecting a bunch of dots.

Seed nutrient density is important and going forward will become even more important, researchers will develop attention levels similar to what we use with soil and tissue tests.

However, right now if you have the choice between two seed lots, one low in nutrient density and the other high, choose the high. Recent research shows that soils high in P and Zn — especially those with subsequent tissue tests with high P and Zn levels, tend to grow seeds with higher concentrations of these key nutrients. Start your seed analysis with contrasting soil/tissue testing fields. Once you have selected your best seed, consider putting additional nutrient on the seed or very near the seed. Use soil analysis, tissue analysis and grain analysis to guide you. Start with a couple of fields and a couple of crops. Learn as you grow forward. When everything clicks, the results can be staggering! †

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