Timely rains throughout the growing season certainly make it easier to grow soybeans, but there are management practices that can help growers get more predictable yield in rain-challenged years.
If the forecast is calling for a dry year the first thing growers need to do is take a hard look at their tillage practices, says Syngenta Agronomic Service Representative Doug Fotheringham. “We want to retain the moisture we have in the soil profile – that means we should try to avoid spring tillage, if possible, so that we don’t create a uneven, dry seedbed. For growers who need to level fields, maybe a heavy harrow could do the job.”
Seed to moisture
Seeding to moisture is key to getting the crop out of the ground quickly and off to a good start. To help with a fast start, Fotheringham recommends growers seed at three-quarters of an inch to one inch in depth. “We can go as deep as 2 inches, but this is a last resort and we would want to avoid this depth if at all possible,” he says. “If we need to plant deeper, soil temperature becomes even more important. Deeper planting requires warmer soils to ensure faster emergence and establishment.”
Stand establishment can be compromised when the crop is seeded above or at the moisture transition line, explains Fotheringham. “What you need to avoid is having half the seed in moisture and the other half in dry soil. When we plant at the transition line, there’s usually enough moisture for that seed to imbibe and start to germinate, but there’s not enough to maintain it through emergence.”
In dry conditions, many growers try to seed the crop just before a forecast rain. That strategy may sound logical, but it can backfire, says Fotheringham. “When we seed soybeans 12, 24 or 48 hours ahead of a May rain, often there’s a cold front behind the rain and that could create cold shock. This can lead to reduced emergence and poor establishment. In the case of a driving rain, growers could also see compaction issues.”
Row planters prosper in dry conditions
Fotheringham also recommends growers consider using a row planter. “In these situations, planters really prove their worth because they don’t disturb as much soil. When we place seed in rows, we also get a little more consistency and better water use efficiency.”
Growers who use air seeders tend to open the ground and disturb more soil, notes Fotheringham. But that can be minimized by choosing a less aggressive opener. “It’s important to understand the type of opener that you are using. If it’s more of a high-disturbance type scenario, you many need to consider your options.”
Variety selection also plays a role in protecting yield. The first thing to consider is drought tolerance. Many seed companies test their varieties in drought conditions and rate their performance. Fotheringham advises all growers to ask their seed supplier for drought ratings when making a seed choice.
Planting multiple varieties is another strategy to take advantage of available moisture and manage risk, says Fotheringham. He advises growers to seed a combination of early- and late-season varieties. “When there’s moisture available early in the season, early varieties can do quite well, but late-season varieties can deliver stronger yields when rain arrives at the tail end of the season. At that time, early-season varieties have already shut down, but later varieties can use that moisture to fill pods.”
Avoid in-furrow fertilizer applications
When it comes to fertility, Fotheringham says it’s best to avoid in-furrow fertilizer applications if it looks like moisture will be scarce. Either a 2x2 band or a side band would be a better choice. Growers should also look critically at their inoculant choice. “I usually say no form or brand of inoculant is better than other, but in dry season scenarios, granular inoculants will outperform everything else,” he notes.
How about your seeding rate? Does a higher rate make sense if the forecast looks hot and dry? In this scenario, Fotheringham explains that higher seeding rates can help protect yield by maximizing the number of nodes per acre. “When we have a reduction in moisture, we’ll have a reduction in vegetative growth. That generally means fewer nodes on a plant. A higher seeding rate will give us more plants and more nodes so we can offset the impact of reduced moisture.”
A final consideration is the previous crop. “Generally speaking, last year across the Prairies we had fantastic wheat, oats, barley and corn crops, and great canola. When you have great crops, that usually means they not only mined nutrients from the soil but also moisture. Growers should take a close look at the fields they’re seeding soybeans into and make sure they have adequate soil moisture reserves,” says Fotheringham.