Like most things in life, there is no simple answer to what causes seed not to germinate or the seedling to die before it gets out of the ground. Alberta’s AgTech Centre in Lethbridge has been looking at mechanical factors such as seed placement, seeding depth and seeding speed as likely suspects playing a role in reducing canola crop emergence rates by as much as 50 per cent. But, AgTech researchers also recognize there are plenty of environmental factors that fit into the equation too.
So the question was posed to crop production specialists across Western Canada: “What do you think is the biggest or couple of key factors affecting seed survival?” The answers were varied whether they were talking about small seed crops such as canola or flax, or large seed crops such as cereals and pulses.
Farmers can do their best to mitigate the risk of reduced crop emergence, but often Mother Nature holds the trump card. One important point from several of the specialists was to start with good quality seed and do your calculations to determine the weight of a 1,000 seed count, to at least insure you’re getting enough seeds in the ground to achieve a target plant count.
Alberta Agriculture, Agronomy Research Scientist
Doon Pauly, agronomy research scientist with Alberta Agriculture in Lethbridge, says there are a wide range of factors affecting seed germination and seedling emergence.
Cereals and other large seeded crops are more forgiving when it comes to soil depth and seed placement. He would expect with a good quality seed batch with 95 per cent germination test, seeded into moisture, he should get 90 per cent emergence. “If you have reasonable moisture you can probably seed anywhere from three-quarters to two inches deep and probably be fine,” says Pauly.
A small seed crop like canola is less forgiving. Again, he says if you can place the seed at one-half to one inch deep and seed at three miles per hour, “you can probably have good confidence in that seeding depth.” If the seeding speed increases to five miles per hour there is bound to be more variability in seed placement.
Openers perform differently as well. With a knife-type opener for example, most seed will be in the seed row, but there might also be some seed spread off to the edge of the seed row and be outside the packer wheel. With poor seed-to-soil contact, or buried 1.5 inches deep it probably won’t germinate.
Just by the nature of the agriculture industry today, farmers aren’t always able to seed under optimal conditions. They have 5,000 to 10,000 acres to seed and they have to get going. Seeding early may mean they seed into cold, damp soil which isn’t conducive to germination, but on the other end of the scale they know there is a yield penalty with some crops if they’re trying to seed after the middle of May or into early June.
Less than optimal seeding conditions is an important factor. Soils can be too cold and damp, with pulse crops for example a slight crack in the seed can allow a pathogen to infect the seed, conditions can turn dry, and depending on soil type soils can crust over. “Farmers don’t always have the luxury of waiting for ideal conditions, and as conditions change many also don’t have the luxury of choosing between two of three different types of seeding systems or openers to better match the conditions,” he says.
Pauly says if the crystal ball works at all, he expects that as the cost of seed increases the industry will focus more on refining and improving seeding equipment to improve seeding accuracy. “Many producers are out there today with massive machines that are 60 and 80 feet wide, with carts carrying tonnes of product so it is pretty hard to call that a precision instrument,” he says. “Some of the machinery researchers working with these large air seeding systems described it as a ‘controlled spill.’ But as seeding costs increase manufacturers and producers will pay more attention to the seeding operation itself.”
Alberta Agriculture, Canola Specialist
Murray Hartman, Alberta Agriculture canola specialist points to some older, yet comprehensive research affecting canola emergence and after a wide range of factors and conditions were analyzed the number one deal breaker turned out to be moisture (or lack of it).
“This research considered all types of factors from soil type, to soil texture, to weather, to seeding dates, soil temperature, different types of seeding systems and types of seed. And after looking at all that, the No. 1 overwhelming factor affecting emergence came down to moisture,” says Hartman. “And it isn’t necessarily the moisture you have just before or right at seeding, but more importantly what happens 10 days to two weeks after seeding.”
He says farmers can seed into dry conditions, but if they get moisture in the next 10 days the crop should be fine. Conversely they may seed into cool, wet soil, but then if the weather turns warm immediately after, the crop should also do well. “So it isn’t necessarily about what conditions are like on the day of seeding, but what happens in the next 10 days after seeding that will impact the success of the crop,” he says. “That’s the real driver.”
While ideally canola should be a shallow-seeded crop, farmers have to weigh the situation, he says. If it is late spring, the soil is dry yet warm, seeding two inches deep to reach moisture, is probably a better option than seeding one-half inch deep into dry soil.
“With moisture the big factor, farmers don’t have a lot of control,” he says. “And there are a lot of ifs and buts to be considered. If it is early May and conditions are a bit dry chances are you can expect rain in the next week or so, so the best option might be to seed shallow. If you are seeding in late May, it might be best to seed a bit deeper to find the moisture.”
Hartman says regardless of how farmers are seeding, the real measure is how many plants are coming out of the ground. His cut-off minimum is four plants per square foot and ideally farmers should target eight to 10 plants.
“Farmers ask me what they are doing wrong because they aren’t getting the emergence or crop stand they expected,” says Hartman. “And I tell them if they are getting six, seven or eight plants per square foot they are doing okay. Regardless of whether they are seeding three or eight pounds of seed per acre, if they are getting six to eight plants that will certainly produce a good crop.”
He says specialists have revised their thinking from the original canola production manual which called for 17 to 18 plants per square foot. That’s too high for canola varieties of 2015. “If farmers are getting 15 plants per square foot today, perhaps they need to cut back on their seeding rate,” he says. “But, what is more common is producers seeding four pounds per acre and getting three plants per square foot. That will produce a crop, but my advice is to increase the seeding rate so there is a minimum of four plants per square foot and preferably more in the seven, eight, to 10 plants per square foot range.”
Manitoba Agriculture, Oilseed Crop Specialist
Anastasia Kubinec, oilseed crop specialist with Manitoba Agriculture considers soil temperature and soil moisture as the two factors most affecting canola stand establishment.
“You are going to get a higher percentage of seeds germinating if you have a warmer soil temperature,” she says. “And along with that you need proper soil moisture. There is a sweet spot there that is sometimes hard to find or doesn’t last very long, but ideally you don’t want the soil too dry or too wet.”
The longer seeds sit in cold soil the more susceptible they are to disease and insects, says Kubinec. In cool soils, seeds can germinate, but if they are slow growing the seed treatment wears off and disease or insects can kill the seedling. And she has seen years when seeds germinate but then conditions turn dry and the seedling just dies.
Seeding rate wise, she says her advice changes depending on the point of the seeding season. If it is early in the season, with cool damp, less than ideal conditions she would advise farmers to increase the seeding rate. Whereas later in the season — mid May and beyond — if soil conditions are warm perhaps they can cut back a bit and still achieve that optimal crop stand.
Manitoba Agriculture, Crop Nutrition Specialist
John Heard, crop fertility specialist with Manitoba Agriculture says obviously, if farmers can wait for warm soil conditions they will probably have the best chance of good stand establishment, but in real life that isn’t always possible.
In his area of expertise, he says, fertilizer placement is always a balancing act. Farmers need to place fertilizer as close to the seed as possible without causing seed or seedling damage.
“Some crops are more sensitive than others,” says Heard. “But generally if you have good moisture conditions in the seed bed the crop is better able to tolerate fertilizer than if you have drier conditions.”
He says as a general rule, with seed placed fertilizer — nitrogen in particular — a crop will recover from 15 per cent loss in the stand due to fertilizer damage. “It can handle that loss, cereals will tiller more, and canola plants will expand their plants and crops will still maintain yield,” he says. “But again it depends on soil moisture. If it is too dry losses will be higher.”
University of Lethbridge, Plant and Soil Sciences
Jeremy Hummel, a researcher and instructor in plant and soil sciences at the University of Lethbridge says seeding under less than optimal conditions might give crop pests the advantage.
Hummel, who has a specialty in insects and diseases, says seeding early into cool soils will increase the risk of seeds and seedlings being exposed to root rot and damping off type pathogens.
“It will depend on the crop and type of seed, but even if the seed is well placed in the soil under cooler conditions it will be more susceptible to pathogens,” says Hummel. “The longer it sits there the higher the risk of being infected with soil borne diseases — root rots are the big one — and insect pests can also be an issue.”
Seed treatments will help to reduce losses, “but I hesitate to call it a guarantee”, says Hummel. “Peas and other large pulses are particularly susceptible to disease under cool temperatures. If the seedling doesn’t break the soil surface and start growing, the seed treatment may not be enough to prevent mortality.”
With soil temperature being a big factor, he says it becomes a balancing act for farmers to get the crop seeded within a limited time frame and still have optimal conditions. Early seeding allows the crop to use soil moisture, often puts the crop out of sync with pests that may come along later in the year, and helps avoid the risk of a killing frost in the fall. Those benefits have to be balanced against the risk of having a slow emerging crop affected by soil borne disease or insect losses.