Soybean Production: Maturity, Weeds & SCN (USA & Canada)

Updated 2026-07-11 · Crop guides

Soybeans pair with corn to anchor most North American rotations, and they are forgiving of everything except three things: the wrong maturity group, weeds that got ahead of you, and soybean cyst nematode robbing yield you never see. Manage those and soybeans reward you with nitrogen-fixing, low-input economics.

Match the maturity group to your latitude

Soybeans are photoperiod-sensitive, so maturity group (MG) is tied to how far north you are. Plant a group that flowers and fills at the right time and matures before frost:

• Western Canada / northern Prairies: MG 00 and 0.
• Upper Midwest, Ontario, Quebec: MG 0–II.
• Central Corn Belt: MG II–IV.
• Mid-South: MG IV–V (often in an early planting / early group system).

Choose varieties with the genetic package your fields need — SCN resistance, plus the herbicide trait (Enlist E3, XtendFlex, or conventional) that fits your weed plan.

Plant early into warm soil — and inoculate new ground

Research now favours earlier planting (late April into May, once soil is 55°F/13°C and warming) to build more nodes and capture light — often ahead of or alongside corn.

• Population: aim for a final stand of 100,000–140,000 plants/acre; narrow rows (15" or drilled) close the canopy faster and shade weeds.
• Depth: 1–1.5 inches (2.5–4 cm) into moisture.
• Inoculate with the correct Bradyrhizobium japonicum on any field new to soybeans (or out of them 3+ years). On established soybean ground the native population is usually adequate.

Because soybeans fix their own nitrogen, they need little to no N fertiliser — skip it and let the nodules work.

Soybean cyst nematode — the invisible yield thief

SCN is the single largest cause of soybean yield loss in North America, and it often shows no above-ground symptoms until damage is severe. Manage it before it manages you:

• Test your soil for SCN egg counts — you cannot manage what you haven’t measured.
• Rotate with non-hosts (corn, small grains) and plant SCN-resistant varieties.
• Rotate the source of resistance — most varieties use the PI 88788 source, and the nematode is adapting to it; alternate with Peking-source resistance where available.

Stay ahead of herbicide-resistant weeds and white mold

Waterhemp and Palmer amaranth resistant to glyphosate (and more) are the defining weed challenge. Beat them with a plan, not a single pass:

• Start clean and apply a pre-emergence residual, then a timely post before weeds exceed 4 inches.
• Layer and rotate sites of action; overlap residuals to cover the whole emergence window.
• White mold (Sclerotinia): worst in cool, wet, high-yield canopies — widen rows or cut population on high-risk fields, choose tolerant varieties, and time fungicide at early flowering (R1).
• Scout for soybean aphid and treat at the 250-per-plant, increasing threshold — not before, so you conserve the predators that often crash the population for free.