What Happened To Soybeans This Year?

With good corn and edible bean yields this year the question must be asked, "what happened to soybeans?" Soybean yields were extremely variable. Although some regions harvested up to 55 bushels per acre, the overall crop was disappointing. In some cases, yields were a total disaster of less than 10 bushels per acre. Seed size was extremely small in some cases. The provincial average will likely be 15 to 20% lower than long term averages.

What took many by surprise is that fields appearing to have a potential of over 40 bushels per acre in August sometimes yielded 30 bushels per acre or less. This problem was not isolated only to Ontario. Low soybean yields right across the U.S. Mid-West helped rally prices this fall.

What Went Wrong?

Before answering this question lets be sure to emphasize that each field had a unique set of circumstances. In most cases the real culprit was a combination of accumulated stresses.

Before answering this question lets be sure to emphasize that each field had a unique set of circumstances. In most cases the real culprit was a combination of accumulated stresses

1. Late Planting

Although some soybeans were planted during May, much of the Ontario crop could not be planted until June due to wet spring conditions. May is the month to plant soybeans for maximum yield potential. Please see Table 1

Table 1. Effect of Planting Date on Yield, Plant Height, Maturity

Planting Date	Yield (bu/ac)	Plant Height (cm)	Days to Maturity
May 10	54	109	137
May 24	48	112	125
June 3	47	112	119
June 13	44	93	112

Ablett, Ridgetown College, University of Guelph.

A cool wet spring, along with poorer seed quality also resulted in slow emergence and thin plant stands. Seed quality was poorer this spring due to last year’s dry conditions. Thin stands have a greater impact on final yields when seeding is delayed, as it was this year. Because of wet spring conditions many fields were planted into less than ideal soil conditions, which further reduced stands and root growth. Poor root growth resulted in the plant having less ability to deal with other stresses later in the season, especially lack of moisture.

2. July Conditions

Cloudy days during the early part of the summer meant less sunlight for photosynthesis. Along with cool nights in July, this slowed reproductive growth and interfered with flowering. Although plant height was considerable, pod set was surprisingly light in some fields.

3. Moisture Stress

In the southwestern part of the province, August and early September was extremely dry. Although sporadic showers in July kept the crop from suffering during early plant development, moisture stress soon became evident during August. August is extremely important to soybean development when plants need considerable moisture to fill pods.

4. Soybean Diseases

Soybean Cyst Nematode (SCN) symptoms were more evident this season than they have been for a number of years. Cyst numbers were high due to some dry years, as well as a lack of crop rotation. SCN has continued to move across the province into new fields. SCN has now been found in fields as far east as Peel Region.

Where moisture was sufficient plants were extremely tall and lush, but this did not translate into yield. Tall growth was partly due to later planting, since early June planted beans are usually taller than early May planted soybeans. These taller plants are more prone to diseases, like white mould. White mould caused considerable damage where moisture was adequate for the disease. A cool wet spring was also ideal for root rot development and caused major plant losses in diseased fields.

5. Soybean Aphids

   Soybean aphid populations were quite low in most of the province until about mid-August. At that time, populations increased rapidly and aphids could be found right across the province. Yield impact due to aphids was most apparent where plants were already moisture or disease stressed. In some fields heavy aphid levels along with dry conditions resulted in poor pod and seed development, as shown in Figure 1. Some pods contained only tiny shrunken seeds.

One thing is clear from this years’ experience - soybeans already stressed due to a lack of moisture or disease cannot tolerate high levels of aphids without yield loss.

Figure 1 - Poor Seed Development

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The Good News

The good news is price! Soybean prices continue to climb, based on strong world demand and U.S. exports. Ontario prices have pushed through the $10 per bushel mark and appear to be headed upward!