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Combining strategies will produce higher soybean yields.

Obtaining higher soybean yields is a great goal. However, the true challenge is doing it sustainably and profitably, year after year and beyond. Think of each soybean plant as a factory. As with any factory, it’s all about how efficiently the factory produces an output and overcomes its potential limiting factors.

When evaluating a soybean plant or “soybean seed factory,” its efficiency and limiting factors can be determined by a mathematic formula: Yield = Pod/Acre x Beans/Pod x Weight/Bean. Several production concepts are being evaluated and will be on display at the 2017 ILSoyAdvisor Field Day on July 20 at the SIUC Research Center in Bellville, Illinois.

Influencing yield factors being observed at the ISA Field Day trials include planting date, planting population, soybean maturity and fertility. All the treatments in the study have an influence on the soybean yield formula. These management decisions are evaluated both as individual factors and combined as a systems approach. 

Planting Date: The industry and its many growers are seeing the benefits of planting earlier and earlier to obtain more sunlight/photosynthesis. Planting dates vary relative to a given area and soil condition. Seed treatments have allowed growers to plant with reduced risk. For this trial, the selected planting dates are May 16 for early and May 30 for the later. Earlier planting tends to yield higher.

Planting Population: Soybean planting populations have been reducing for the past 10 years due to  planting equipment, genetic improvement and seed treatments. In recent years standard populations have dropped to or below 160,000 seeds per acre. For this trial the selected populations are 100,000 for low and 140,000 for high. We may all remember planting at 180,000 or even 220,000 seeds per acre.

Soybean Maturity: Knowing the genetic potential of each soybean variety is important when it comes to proper placement. Depending on planting date, the relative maturity of a soybean can impact both the total nodes produced and its ability to handle stress. For this trial the relative maturities used are a 3.5, which would be early for this environment, and a 4.4, which would be more standard for the regional area. Fuller maturities tend to yield higher.

Fertility Management: For years the fertility program was 200 pounds of DAP and 200 pounds of potash applied per acre. Whatever the corn didn’t use was left over for the next soybean crop. We now need to evaluate the true needs of a soybean plant during key growing times. A lot of questions come up regarding potassium (K) and nitrogen (N) as potential limiting nutritional factors. This trial is observing treatments of additional K, additional N, and additional P and K as a combination It’s a best practice to fertilize soybeans separately from corn.

Key development mileposts:

1. Soybean seeds need 50 percent of their weight in water

2. Cotyledons supply energy and nutritional needs 7 to 10 days after VE or until V1

•  Losses prior to V1 could see up to 8 to 9 percent yield reduction.

3. V1: Photosynthesis starts

4. V3: Weed pressure competes for moisture, nutrients and sunlight

5. Yield is factor of pods/plant + beans/pod + weight of each bean

• The largest yield swing comes from increasing pods per plant. Increasing nodes increases pod set
• R1-R5 stresses can greatly impact yield because the plant can’t handle the stress
• 60 to 75 percent of flowers abort and have no yield. Half abort prior to pod development and the other half abort after

6. R5.5: Maximum height, pod numbers, leaf area

• At this time the seed starts a rapid nutrient accumulation
• N fixation drops off
• Seed N increases significantly

CCA Todd Steinacher is an agronomist at AgriGold. He works with growers to better manage their nitrogen and weed control needs, along with understanding the best way to estimate cost to generate a strong ROI. He is a 2017 Illinois Soybean Association CCA Soy Envoy.