Soybean School: Ranking yield impact of management practices


Which management practices help boost soybean yields and give you the best return on investment?

That’s a question Wisconsin soybean specialist Shawn Conley and his colleagues have been working on for four years, and the answers may be surprising for many growers. On this episode of the RealAgriculture’s Soybean School, Conley shares how the researchers looked at data from across the north-central U.S. (representing 82 per cent of the country’s soy production) to rank management practices and the impact they can have in farmers’ fields.

“It really is a big data approach to figuring out what farmers are doing on-farm to influence their soybean yield and rank the factors based on what farmers are seeing at the ground level,” says Conley, who is based at the University of Wisconsin Madison. Data from 8,000 fields and 600,00 acres was used for the study.

Topping the list of the management ranking was sowing or seeding date. Conley notes that over the past 10 years, mounting data shows the benefit of planting soybeans early — April 20 in Wisconsin, for example. There’s also growing evidence to support the practice of planting soybeans before corn.

“What we’ve seen is… there’s really not a big penalty for planting soybeans early,” says Conley. Based on the data, on average farmers can expect to realize an additional 0.2 to 0.3 bushels per acre, per day when planting starts April 20. “Over ten days that’s three bushels of free yield. That’s big,” he says. (Story continues after the video.)

Number two on the management list is latitude. Conley says this is essentially an acknowledgement of the importance of heat units and maturity groups and the higher yield potential of longer-season soybeans grown in more southern growing areas.

Surprisingly, soil pH occupies third place in the ranking. Conley says a key factor in driving this ranking is the relationship between pH and soybean pests such as soybean cyst nematode and soil-borne diseases. When soil is above or below a pH range of 6.2 to 6.5, growers can run into trouble with disease. He notes that local conditions such as weather and other background factors (e.g. soil fertility) do influence the impact pH levels can have on the crop.

In the video, Conley also comments on the importance of topsoil organic matter and seeding rates. The impact of starter fertilizer and seed treatment is also discussed. Although these two variables score low in the ranking, they can have a significant impact depending on local conditions. For example, seed treatments can play a critical role when seed is planted into cool, wet conditions; starter fertilizer can deliver significant ROI when soil tests reveal low levels of P and K.

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