Q: What should I consider when planting my soybean crop?
A: There are several important factors to keep in mind when growing soybeans. Consider your climatic conditions including heat units and moisture. Soybeans require a full season of cumulative heat to mature adequately. Varieties with maturities ranging from 2350 to 2500 Heat Units are well adapted to the Manitoba Red River Valley while early maturing varieties (2225 to 2350 HU) are gaining traction in southeast Saskatchewan and southern Alberta.
Adequate soil moisture throughout the growing season is necessary to optimize soybean yields. Annual precipitation in Manitoba and southeast Saskatchewan (where soybeans are commonly grown) amounts to 15 to 20 inches. Maintaining adequate soil moisture in July and August is particularly important. Seed number and bulking up of seed size is highly dependent on this moisture.
Prior to seed, soybean inoculant is essential as soybeans require a high volume of nitrogen to reach full yield potential (four to five pounds per bushel). Fortunately, soybeans fix nitrogen through nodulation. Double inoculation is recommended for soybean fields without a history of soybean production. Proper nodulation is a critical step to ensure nitrogen requirements are met.
Another factor to consider is seedbed preparation. Successful crop establishment is dependent on a warm seedbed (above 10 C). Excess trash can cause challenges with soil warming and crop establishment. Assess and remediate fields with tillage in the fall or spring prior to planting.
Weeds are important to consider as well. Control difficult winter annual, biennial and perennial weeds like Canada thistle in the year prior to planting soybeans.
Finally, consider your crop rotation. A three to four year crop rotation between soybean crops is important for diversity and yield stability over time. Identify and consider the impact of soil factors like salinity, low ph (acidity) and soil texture that may impede crop establishment and productivity. Low levels of salinity and carbonates are preferred as both have an impact on iron deficiency chlorosis (IDC).
Gary Topham is a manager of agronomic services with Crop Production Services in Manitoba.