Seeds And Seedlings With Speed

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 of corn seed production 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 that 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. With the use of plant sap analysis, we have established 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. Seeds that do not carry a healthy microbiome predispose young seedlings to disease susceptibility and 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. 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.

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

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.

Seedlings With Speed

It is common for seedlings to emerge and remain a pale yellow-green color for several days after emergence. In challenging weather conditions with overcast skies, I have observed light-green color in seedlings as late as two weeks after germination. Every day that goes by with the seedling not having enough chlorophyll is a day of photosynthesis and energy generation lost. Chlorophyll synthesis is triggered by exposure to light photons. When a seedling emerges, the cotyledons should turn dark green and be filled with chlorophyll within 24 hours of first being exposed to the light. As soon as chlorophyll is present, the seedling begins generating carbohydrate energy, the majority of which is transported to the root system, where it is utilized both to build root biomass and to build microbial populations in the rhizosphere.

Sometimes infections by soilborne organisms such as pythium, phytophthora, rhizoctonia, fusarium, anthracnose do not become visually observable until weeks or months afterward, when plants switch from rapid vegetative growth to reproduction. The visual expression is delayed for the infection, which occurred much earlier and only developed slowly until the plants came under stress. The two-week window after germination is the critical time to establish an abundant population of disease-suppressive organisms in the rhizosphere. Each day that colonization is delayed is an additional opportunity for potential pathogens to gain entry to the root system and produce a low-grade infection.

Root mass development on cover crop with BioCoat™ Gold and AEA Soil Primer

Establishing an abundant population of disease-suppressive organisms around the rapidly growing root tips of a germinating seed requires the release of root exudates to provide a food source and a biostimulant for the organisms that came along for the ride on the seed surface, as well as any additional organisms that are recruited from the soil profile. However, a seed has limited energy reserves. As I understand it, very little root exudates are produced from the sugar reserves carried within the seed. The sugars within the seed are kept in reserve to maintain (not

grow) the seedling in the case of challenging weather conditions. The seedling only begins moving a lot of sugars out through the root system as root exudates to feed biology once it can generate those sugars from photosynthesis. Every day photosynthesis is delayed or reduced is a day with fewer root exudates, a day with fewer disease-suppressive organisms, and a day for potential pathogens to gain entry.

Ideally, seedlings should emerge and immediately turn dark green — as dark green as when they are healthy and approaching their mature size, or right at the end of the framing stage, when they are building rapid vegetative growth. The idea that seedlings are naturally supposed to be a light-green color is monkey business. In order to do this, they specifically need the nutrients such as iron, magnesium and nitrogen that are required as enzyme cofactors for chlorophyll synthesis. Ideally, these minerals would have been provided in abundance to the seed parent and would already be stored inside the seed. Sadly, though, this is seldom the case.

It is worth pointing out that the mineral deficiencies present within the seed can not be corrected by a microbial inoculant alone. Well-designed seed treatments with microbial inoculants have demonstrated their economic and crop performance value, but even when they are used, a great deal of opportunity remains untouched. If the seed’s parents are unlikely to have provided the nutrients that are necessary for strong photosynthetic activity in a newly emerged seedling, how can a grower fill that gap? Soil treatments and foliar sprays are possibilities, but they are not as likely to provide the nutrition as directly as a nutrient-rich seed treatment.

Mineral nutrition treatments can be sprayed onto seeds at rates as low as a few quarts per ton of seed and as early as months ahead of planting. The treatment is absorbed into the seed, and at such low volumes, it doesn’t make the seed soft or moist, which means that the seed can run through any type of planter system without damage — as can occur with seed soaking. Growers can apply these treatments themselves with a single spray nozzle as seeds travel down a conveyor, or they can often have their supplier treat the seed for them, since many are optimally equipped to do so.

We want seed to germinate quickly, and then we want the seedling to take off and go like a horse out of the gates. In our work at AEA, we find that nutritional and microbiome support at this critical seedling stage consistently produces visually observable results in root biomass and seedling development. This doesn’t necessarily mean larger seedling size. For continuous fruiting reproductive crops like cotton and soybeans, we want the node spacing to remain compact, which may mean the seedlings themselves don’t appear to be larger, but the increased number of fruit is substantial.

A consistent stand of dark green seedlings right after emergence is a landscape of beauty, one that we too seldom get to see. A well designed synergistic combination of nutrient and microbial seed treatments can be the most impactful — and highest ROI — application you can make.