Soil temperature, moisture, date, farm size, forecast and other factors all contribute to the decision whether to plant on a given day
By Jackie Clark
Planting season is underway. Every day, producers across Ontario are making decisions on when to get their seed in the ground. Some debate exists over which parameters, including soil temperature, moisture, and the weather forecast, should contribute most to determining optimal planting timing.
Ultimately, planting decisions depend on many factors, including geography, date, and farm size, Paul Hermans told Farms.com. He’s the Eastern Ontario territory manager for Corteva Agriscience.
In Eastern Ontario, “if it’s before April 25, I like looking at the soil temperature and the time of day. But once it gets to April 25 and that calendar starts marching on, I say ‘to heck’ with the thermometer. I look at if the ground is fit, the conditions, and the forecast for the next three to five days,” Hermans said.
The size of the operation may also factor into the equation. If a producer has fewer acres to plant, he or she may be able to afford to hold off on seeding for longer. But the larger grower might not be able to wait, Hermans said.
As we know, soil conditions affect seed germination.
In terms of soil water temperature, “it’s the first half hour of water that the seed takes in that’s most important,” Hermans explained. “Corn needs (to imbibe) about 30 per cent of its weight in moisture before it germinates. Soybeans need about 50 per cent (of their weight in moisture). … But, in general, it’s that first uptake” that has the biggest influence on germination.
To prevent the seed from chilling during that first half hour of imbibing soil water, farmers seeding early in the spring should plant in the heat of the day. Depending on soil conditions, farmers can start between 9:00 or 10:00 a.m. and should end by around 5:00 p.m. if it is going to be a cool evening, Hermans said.
Producers should also look at planting depth, Hermans said. “Some people (might suggest) planting shallower (an inch and a half) because the soil will warm up quicker and the seed will germinate quicker. Well, correspondingly, if you plant shallow … that soil will also cool down quicker.
“So if you’re planting earlier on with cooler conditions, you have a bit of an insulation buffer at a depth of two or two and a quarter inches. The temperature of the soil at that level doesn’t fluctuate as much,” he said.
“Corn seed especially doesn’t like up and down temperatures,” he added.
If planting early in cooler conditions, growers may want to adjust their seeding rates. “A little higher percentage of that seed might not germinate. So, we want to offset (the potential loss) with a higher seeding rate in those challenging conditions,” Hermans explained.
Later in the spring, farmers can make decisions based more on moisture conditions than temperature.
“I look at soil conditions – I want to make sure that it’s not too wet. We want to avoid side wall smearing and side wall compaction. If it’s too wet, the planter is just going to smear that soil cause a lot of other challenges throughout the growing season,” Hermans said.
Early planting – especially of soybeans – can lead to a yield advantage because the crop has more time to form side branches, research shows.
Because of our northern climate, producers want to “avoid a fall frost and the crop not making it (to maturity). So, that’s why this earlier planting time really comes into effect. Just don’t mud it in,” Hermans said.
Growers who had to wait out the winter to harvest some of their 2019 crops should be good to move ahead with planting as soon as soil conditions allow, Hermans said.
Producers can use software like Corteva Fields to input their hybrids, planting date, and weather data to help track the development of their crops, and predict the timing of emergence.
Zoran Zeremski\iStock\Getty Images Plus photo