You’ve decided your target plant population, you know your seed weight, you’ve calibrated your drill — how are you going to achieve that uniform plant stand this year?
Those Pesky Small Seed Crops #
With smaller seeded crops like canola and alfalfa, it’s best to start off with a shallow seeding depth. The optimal seeding depth for canola is about ½” to 1” in depth, while most forage crops benefit from being seeded even shallower at ¼” to ½”.
“As your seed goes deeper into the ground, the seeding rate should be increased to make up for the plants not reaching the soil surface,” said Justine Cornelsen, BrettYoung’s Agronomic and Regulatory Services Manager.
A key component of seeding depth is packing pressure, she said, which needs to be altered under different soil conditions.
“With a dry spring and dry soils, the seed needs to pull water from surrounding soil particles to germinate,” said Cornelsen. “So, packing pressure needs to create a firm seed bed that allows for optimal seed-to-soil contact. In wet soils, packing pressure can be less to minimize the potential of the soil crusting.”
She noted the opener style and placement of fertilizer may not leave the seedbed as firm as small seeded crops need.
Seed-placed fertilizer is a high-risk factor that can compromise uniform plant population if it isn’t planned carefully. For canola, 15 to 20 lb/acre of phosphorus can be placed safely with the seed. For forages, 10 to 15 lb/acre of phosphorus is recommended to be seed placed. You need some phosphorus close to the seed as it’s immobile in the soil and seed utilizes it to have a pop-up effect. Too much phosphorus close to the seed, however, can be toxic. For small seed crops, Cornelsen said placement of your remaining fertilizer is best in a side band.
“Seeding slow allows for uniform shallow seeding,” she said. “Seeding speed should be set based on the drill’s performance to achieve uniform seed depth.”
Corn and Soybeans #
Larger seeded crops can be placed deeper in the soil as they can still achieve uniform plant stands that way. Soybeans can be planted ¾” to 1 ¾” deep, while corn can be pushed to 1 ¾” to 2 ¼” into the soil. Corn needs to be seeded deep so the seminal roots don’t emerge at the soil surface and create a weak anchoring of the plant.
Corn and soybean crops can be successfully seeded with a drill, but Cornelsen said a row planter will help to dial in the seeding rate and can minimize skips or double-ups.
“Corn plants are very sensitive to their surroundings,” she said. “Seed double ups can cause weaker plants within the crop canopy, which hurts uniformity in the end.”
The critical weed-free period for corn and soybeans must be kept exactly that – weed free – to prevent yield loss. With a row planter, you have to do weed management in a timely manner as the crop canopy takes longer to close in, and it’s critical for uniform plant emergence. Uniform crop canopies make that in-crop herbicide decision easier, and they minimize your plants’ risk of herbicide injury.
The Wild Card #
Weather is always the wild card. We can’t control what is has in store, but we can plan for whatever it may throw at us.
Seed emergence is dependent on soil temperature for every and any crop. Soybeans can emerge in as little as four days if they’re seeded into soil with a temperature above 14°C. If soybeans are seeded into cold soils, their emergence can be upwards of a month.
Canola exhibits similar behaviour to soybeans, able to germinate in soil temperatures as low as 2°C. The optimal soil temperature for canola, though, is above 10°C, which allows for a faster plant emergence.
“Seed that germinates but is slow to emerge become susceptible to seedling diseases and runs the risk of using up energy reserves to emerge,” said Cornelsen. “Which leaves it stranded.”
She also mentioned crop rotation can play a role in seedling disease pressure.
“Crop rotations that are heavy on a specific crop type influence the pathogens within the soil,” she said. “The more often a crop is grown in that soil, the more likely the seedling pathogens its susceptible to will be present. Crop seed treatments begin to wear off after time and under specific environmental conditions, so the longer a seed is left stranded in the soil, the greater chance for damage.”
In the end, no matter your seed size, it all comes down to achieving a uniform plant stand to help plan your next in-crop application and maximize yield potential. Yield potential is locked in at plant establishment and the rest of the growing season is where you try to preserve it – a little rain helps.
