Co-op Growers Day 2019: Horst Bohner on Soybean Management
Horst Bohner, OMAFRA soybean specialist, spoke at Co-op Regionale’s Annual Grower’s Day in December.
Bohner opened his presentation by mentioning that it was a rough growing season for many people, including himself. He related an experience he had during planting. He had left his pickup truck in a field, had returned later, turned it on, and left the field. He then promptly ran out of gas, and quickly realized that someone had drilled a hole in his gas tank to drain the gas out, and the tank had to be replaced. Unfortunately, the 18 dollars of stolen gas cost him some 1800 dollars in repairs. Perhaps the moral of Bohner’s opening story was that things are never so bad that they can’t get worse.
On that positive note, Bohner addressed the growing season itself. For soybeans, the planting was the latest on record, followed by a variable summer in which some areas had good rainfall while some had drought-like conditions. All that, combined with early snows in many places, made yields unpredictable. The provincial average is expected to be about 44 bushels an acre, which would be a surprisingly good yield considering the conditions. Both the 10 year and 5 year yield averages are 47 bushels per acre, so 44 turns out to not be the catastrophically low yields some were expecting.
One point Bohner addressed was whether using a short season variety of beans would be wise if planting is delayed, like it was this year. In Southwestern Ontario, where testing was done on this subject, the general guideline is that if planting is delayed past June 5, a shorter season variety is recommended to ensure that it can actually mature and be harvested before the season ends. This year, however, since the fall was relatively open, both long and short season varieties of soybeans had about the same yield. But up in northern Ontario, where the growing season is shorter, it may be a good idea to select a short season variety if planting is delayed.
Bohner also recommended tilling in a cooler environment like northern Ontario. It breaks up the ground and gives soybeans a better start, allowing for better growth in the spring. Varieties also play a big role on yield. Bohner suggested always trying a few different varieties each year to see what works best on an individual farm or field.
For nutrient management, sulphur is important. Bohner spoke about whether application of sulphur fertilizer was able to increase yields. In one test, 100 pounds of ammonium sulphate was applied per acre to a field of soybeans. Planting was delayed, which may have affected the data, but the added fertilizer did not result in an increased yield. Soybeans also need nitrogen, and another test was conducted with nitrogen, though again the planting was delayed. Like the previous test, they did not result in an increased yield. Soybeans certainly need both nitrogen and sulphur, but it seems that adding additional nutrients do not have a huge effect.
In terms of seeding rate for soybeans, tests have revealed that 165 000 seeds per acre resulted in a yield of 64 bushels per acre. 130 000 seeds per acre resulted in a 62 bushel yield, and 95 000 resulted in about 63 bushels. Overall, the seeding rate seems to make little difference on yield at the end of the year. This is because soybean yield depends less on the number of plants in an acre, and more on the number of nodes in an acre. Nodes are the bits on soybeans where the actual beans hang off. The more nodes, the higher yield. Bohner said that the ideal number of nodes per acre was two million, regardless of planting date, planting row width, or variety. In the north, where the individual plants have less opportunity to grow, a higher number of plants are necessary to reach that two million goal, and therefore a higher seeding rate is necessary. Bohner suggested that a seeding rate of 194 000 is the general recommendation to reach the two million node goal, and if planting is delayed, increasing seeding rate to 225 000 per acre could be considered.
Bohner talked about a farmer in Michigan who regularly wins yield competitions, with about 100 bushels per acre every year. His soybeans grow about 20 nodes per plant, but his productivity comes from the number of pods that grow from each node. How can farmers try to maximize the number of beans that grow on each node? First, is fertility. Trials conducted in Elora found that high soil fertility is the most important factor in increasing the number of pods per plant. Trials conducted this year found that soil where the fertility had been built up over several years resulted in higher yields than low fertility fields that had a ton of fertilizers applied to them. For built up fertile soils, the aim would be to have test values of 20 to 30 phosphorus, and 120 potassium.
To summarize simply, in order to have the best yield possible, Bohner said that soybeans need to be planted in good, fertile ground, preferably early in the season with a good variety that fits the conditions of a certain location. Other determinants of growth, such as pests or nutrient issues, need to be dealt with as they arise. Beyond that, most of the yield potential for soybeans, for better or worse, depends on the weather.