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Seeds with Speed

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.

The spring wheat seedling on the right was treated with a BioCoat Gold and nutritional support at planting. The seed germinated 12 hours after planting in cold soil and challenging weather conditions. The comparison seedling is the grower’s standard program.

 

Root mass development on cover crop with BioCoat Gold and AEA fall soil primer

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.

Low-Quality Seed

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.

Management Actions

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.

Keeping inoculants on the seed

If microbial inoculants are to be effective as seed treatments they need to remain attached to the seed until they arrive in the soil. Some products, such as mychorrizal fungi inoculant, can have a fairly large particle size, and does not stick to seed very well, particularly smooth seeds such as beans.

The last thing we want to see is accumulated inoculant at the bottom of the seed hopper when we get done planting.

When you apply seed treatments yourself, lightly spray a sugar-water solution onto the seed before the inoculant is applied. This serves to make the seed slightly sticky, and microbial powders remain strongly attached to the seed.

2020-04-11T15:39:36-05:00April 13th, 2020|Tags: , |

Impacts of glyphosate residue on seed germination

Some new research1 describes the impact of pre-emerge glyphosate applications on seedling development and yields, and the impact of prior year appplications. The conclusion: you certainly want to avoid any application until well after seedling emergence, and prior year applications are probably impacting your current yields. It seems we need to begin using alternatives immediately.

The article itself is a great read, here are a few excerpted highlights:

  • The seed germination of faba bean, oat and turnip rape, and sprouting of potato tubers was delayed in the greenhouse experiments in soils treated with GBH (glyphosate based herbicide) or with pure glyphosate.
  • The total shoot biomass of faba bean was 28%, oat 29% and turnip rape 58% higher in control compared to GBH soils four weeks after sowing.
  • Grazing by barnacle geese was three times higher in oats growing in the GBH soils compared to control oats in the field. 
  • Our results indicate that the use of GBH, as well as surfactants and other ingredients of commercial herbicide products, have different effects on the seedling establishment of seed- and vegetative-propagated crops.
  • In all the studied seed-propagated crops, germination was faster, and in turnip rape and oats the total germination percentage was higher in the C soils compared to the pure G- or GBH (Roundup)-treated soils.
  • seed-propagated crops with limited endosperms as an energy source are likely to be exposed to GBH residues in soils following water imbibition at the beginning of the seed germination.
  • Our results suggest that the use of GPH may have unintended and undesirable consequences for farmers. The speed of germination and early growth may be crucial for the plants, depending on the abiotic and biotic environmental factors. Especially in spring, earlier individuals may benefit from moisture and a lack of competition. Thus, delayed germination and weakened growth of seed-propagated crops in GBH-contaminated soils may invalidate the intended crop protection if targeted weeds get a head start in early spring.
  • The use of GBH may increase the yield loss caused by flea beetles and further challenge spring-planted oilseed rape and turnip rape cultivation
  • Glyphosate can enhance the attractiveness of plants to vertebrate herbivores. In the field experiment, the oat plants growing in GBH-treated experimental plots experienced heavy barnacle geese grazing while the adjacent plants in C plots were only mildly grazed. 
  • Glyphosate is known to inhibit the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) in the shikimate acid pathway, thereby interfering with the production of tryptophan, phenylalanine or tyrosine, which are precursors of proteins and other molecules, including growth promoters (e.g., indoleacetic acid, IAA) or secondary compounds with known importance for plant defense against herbivores (e.g., tannins, anthocyanins, flavonoids, and lignin.
  • Overall, the effect of pure glyphosate was weaker compared to that of the commercial formulation (Roundup Gold) containing the same amount of glyphosate. This supports other studies suggesting that other ingredients in GBH, such as surfactants, solvents, and preservatives, could also cause adverse effects on non-target organisms.
  • Our results clearly demonstrate that the use of GBH has detectable effects on crop plant germination and growth, and their quality to herbivores, even though we used field-realistic concentrations of GBH and the experimental plants were introduced into the soil after a two-week withholding period.
  • In contrast to seed-propagated crops, GBH treatment boosted the growth of vegetatively propagated potatoes, and glyphosate appeared to accumulate in the potato tubers. This leads to the critical question of whether the residues in potatoes have consequences for the subsequent year’s yield.
  • These results emphasize the importance of a more comprehensive understanding of the effects of GBH on the productivity of crop plants and their chemical ecology, affecting their pest and pathogen resistance and thus the need for crop protection.
  1. Helander, M., Pauna, A., Saikkonen, K. & Saloniemi, I. Glyphosate residues in soil affect crop plant germination and growth. Sci. Rep. 9, 19653 (2019).

 

2020-03-16T13:54:09-05:00January 14th, 2020|Tags: , , , , |

Effective Seed Treatments

For direct-seeded crops, seed treatments are the least expensive and highest return application a grower can apply. 

Seed treatments can contain bacterial inoculants, fungal inoculants, microbial biostimulants, plant biostimulants, and trace minerals. The most effective treatments usually are a synergistic stack that contains ingredients from several or all of these categories. 

Trace mineral seed treatments are most important with poor quality seed that is small in size and light in weight (most commercial corn seed). High-quality seed often contains enough of the more common trace minerals. 

Many seeds, at least those grown on healthy parent plants, vector their own symbiotic endophytic microbes, both bacteria and fungi. In addition to those microbes vectored on the seed, seedlings also recruit symbiotic fungi and bacteria from the soil, particularly mycorrhizal fungi, as well as others, even some of the same species they carry along on the outside of the seed. 

Applying mycorrhizal fungi and other bacterial inoculants as a seed treatment is generally an effective delivery method to achieve early root colonization, particularly for monocots, where the seed remains in the ground. 

For dicotyledon plants, I have always wondered how effective it is to treat the seed when the seed is soon pushed up and out of the ground. Many growers have used seed treatments on these crops effectively, but I suspect we may get better responses from applying them in-furrow right with the seed when the option exists.

One other thought, applying a fungal inoculant on fungicide treated seed doesn’t seem like the brightest idea under the sun. We know the crop does benefit because this is a (surprisingly) common combination. How much bigger might the benefits be if the fungicide was removed and the beneficial fungi permitted to flourish.

2020-03-16T13:53:28-05:00January 13th, 2020|Tags: , |
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