What if you could get seeds to germinate as fast in challenging conditions as they emerge in ideal conditions?
This article was published in AcresUSA a few weeks ago, and I wanted to share with you here.
Seeds with Speed
How to manage germination speed and seed quality in producing high-quality crops
When seeds germinate quickly and a new crop becomes visible above the soil soon after being planted, it brings smiles to our faces. We know instinctively that plants that get off to a vigorous start have the potential for a healthy crop with abundant yields.
When seeds germinate slowly because of challenging soil or weather conditions, we recognize that this early stress on the young seedlings is likely to produce a yield drag, as the plant seems to struggle to catch up for the rest of the growing season.
There are many benefits of rapid seed germination and seedling emergence. When seeds germinate quickly, they provide little opportunity for insect larvae such as corn seed maggot to begin feeding on the seed. When root systems develop quickly and fill large soil volumes while the seedling is still small, the possible damage from wireworm or rootworm larvae is greatly reduced. For plant species that produce an allelopathic effect from the root system, rapid root development can have a pronounced effect on suppressing germination of other seeds, producing a field that is practically weed free. When seedlings grow very rapidly, and contain balanced nutrition from the seed, they are resistant to slugs and flea beetles feeding on them shortly after germination. However, none of these positive effects occur when seeds germinate slowly or when seeds are of poor quality.
These positive effects have always been appreciated by organic crop farmers who wait to plant until the soil is warm and weather conditions are as ideal as possible. The rapid seedling emergence that occurs when planted in good conditions provides an opportunity for much better weed control, as cultivation can be done earlier and the crop shades out weed seedlings more rapidly.
Planting conditions are not always ideal, however. With the pronounced vagaries of the weather we are all experiencing every year, it is probable that conditions will be less than ideal more frequently in the future than they have been in the past.
Many growers have also been recognizing that purchased seed quality is not what it should be, and not what it used to be. Many seeds appear to lack vigor, and may germinate only very slowly, even when planted in ideal conditions. This is especially true of commodity grain crop seeds, but also for many vegetable seeds.
Several years ago, a colleague obtained several hundred seed corn samples from seed suppliers and planted them in seedling trays in a germination chamber to test vigor. While most of the seed samples reached the germination percentage on the label, many germinated quite slowly, emerging only 5-7 days after being planted. Some emerged 10 days after being planted, despite being maintained in perfect moisture and temperature conditions for rapid germination.
This becomes understandable when we consider the objectives and processes of corn seed production. The objective has become small seed size, which is the opposite of what would be produced if the goal was vigorous seeds. When we think about how corn seed is produced, no special consideration is given to plant nutrition. In fact, it is considered that seed corn can be grown on poorer soil, since yields are not expected or needed to be as high. Before pollination, the plants are “detasseled” by cutting off the plant above the ear with a mower, which removes a third to a half of the plant’s photosynthetic capacity. To keep seed size small, the plants are desiccated as soon as the seeds reach maturity, frequently with a sodium/potassium chloride solution as a desiccant. The end result of this process is a corn seed that is small, lightweight, low in stored carbohydrate energy, low in mineral content, and loaded up with chlorides. The icing on the cake is fungicides and insecticides the seed is treated with before being planted. A safe summary is simply that commercially grown seed corn is generally of atrocious quality.
It should be no surprise that these seeds germinate slowly and are particularly susceptible to insects and disease. We have established with the use of plant sap analysis that anytime chloride levels in plant sap exceed the levels of total nitrogen, plants are particularly susceptible to insects. You can almost always observe large populations of insects feeding on a crop where this ratio is present. These corn seedlings have been set up to be dependent on constant life support for the rest of their life.
For many crops, seed production is not quite as badly screwed up as corn seed production, but little or no consideration is given to producing high seed vigor, other than as measured by germination percentage.
Qualities of Superior Seed
There are two key aspects to superior-quality seed that germinates quickly. The best seed contains abundant nutrition — mineral nutrition as well as carbohydrates, proteins and fats. Seed with generous nutrition will be heavy, have fewer seeds per pound, and have a high test weight. In addition to the nutritional component, the best seed also carries a population of symbiotic microorganisms on the seed surface that immediately colonizes the root system and leaf surface as the seed germinates.
The speed of microbial colonization on the root system is very important to produce resistance to root diseases. When this beneficial microbiome is not carried through on the seed, the seedling now needs to recruit microbes from the soil to colonize the root surface and develop a healthy microbiome. This process takes time and may require the contribution of more sugar and energy through the root system as root exudates. The length of time for this recruitment process varies depending on plant species and the soil microbiome, but can take up to two weeks. During this recruitment window, when the seedling root system is not yet fully colonized by beneficial and symbiotic microorganisms, there is a window of opportunity for organisms to develop pathogenic relationships with the plant. Fusarium, rhizoctonia, pythium, anthracnose, phytophthora and many other root-rot diseases gain traction in the initial weeks after seed germination when root systems are not immediately colonized by disease-suppressive microbiomes. Seeds that do not carry a healthy microbiome predispose young seedlings to disease susceptibility. Fungicide seed treatments amplify this susceptibility.
The lack of a healthy microbiome on the seed does not only increase susceptibility to disease — it also changes root system development and size. Some of these beneficial bacteria are referred to as PGPRs — plant growth promoting rhizobacteria. These bacteria produce phytohormones that influence plant growth and development, particularly root branching. Many growers have observed that the use of microbial inoculants as a seed treatment produces a much larger root system on seedlings, with a lot of root branching as compared to untreated seed. This effect is produced by microbial colonization and the phytohormones they contribute to the plant. These robust root systems, established immediately after germination, are a critical foundation to produce large crop yields when plants are expected to obtain the majority of their nutrition from microbial metabolites rather than from soluble fertilizers. Without a large root system, plants are unable to obtain enough nutrients during the fruit-fill/grain-fill period to produce exceptional yields.
In addition to producing large root systems, the phytohormones produced by the PGPRs also contribute to overall stem size and expansion. For plants to carry a heavy fruit load to maturity, they require a large water and nutrient-transport pipeline. Frequently, plants have the genetic capacity to produce a lot more fruit, but the pipeline is not large enough to supply the water and nutritional requirements to support a heavier fruit load. Having the plant growth promoting rhizobacteria present from the moment of germination is foundational to increasing yields above average baselines.
Given the value of seed quality, what management actions can we take to improve our crops’ performance?
If you produce seed, manage nutrition and biology to go above and beyond, and produce the heaviest and largest seed size you can. This will also produce very positive epigenetic results, where the following generation is almost certain to be more vigorous than the parent generation, and may begin expressing itself differently, especially over several generations.
If you market seed, produce superior quality, and market it accordingly. Growers care — a lot. This is an easy opportunity to be a market leader.
If you buy seed, get the heaviest and largest seed you can find for a given variety. Check seed counts per pound. Book seed well in advance so you can get it untreated with -cides. This is the nexus of where you want life to proliferate — not death.
To test seed vigor and the effects of inoculants and nutritional supplements, plant test seeds in clear plastic cups so you can observe how quickly roots reach the wall of the cup, and how many are visible.
Given the quality of seeds generally available, it is important to think about how we can enhance seed microbiomes and nutritional integrity in an effort to make up for what was missed during the production process. Adding microbial inoculants and nutrition that can get inside seeds can produce some remarkable results.
I believe it is important that microbial inoculants contain a combination of beneficial bacteria, mycorrhizal fungi, microbial biostimulants and probably other organisms as well. I refer to these combinations as “synergistic stacks,” where one plus one produces something greater than two — sometimes much greater. Living organisms can produce a compounding effect, rather than an additive one. This is exactly what we need at the critical stage of seedling development.
In our consulting work, we recommend an inoculant almost universally on planted seeds because of the rapid germination and root development responses we observe. Microbial inoculation at planting is consistently the lowest cost and highest ROI of almost any application type that a farmer can make.
In addition to inoculation, I am also very intrigued by the possibilities of nutritional seed treatments, where the nutrients are actually absorbed and utilized inside the seed. It is well established that seeds with abundant levels of trace minerals such as manganese, zinc, copper and boron will germinate much more quickly than those without.
We have worked with growers who have applied a combination of chelated trace minerals in amounts ranging from 25 to 100 ounces each of manganese, iron, zinc, cobalt and copper per ton of seed. These liquid trace minerals are combined with water and mixed with seed. The amount of water used will vary depending on seed type, but we want to use just enough to get good distribution and to allow the seeds to absorb all of it, while still feeling dry to the touch and flowing through planting equipment well. It is possible to use small enough amounts of water that seed can be put back in storage for several weeks before being planted.
Think of seed treatments as colostrum for the developing seedling — nutrition it should have gotten from its parent, but probably didn’t.