478 Managing The Soybean Rotation Effect
Soybean acreage in the Red River Valley has dramatically increased in the past 10 years. Prior to 1995 few acres were planted north of Cass and Clay Counties. Today soybeans are commonly planted all the way to the Canadian border. Wheat and barley are becoming less profitable each year. Fusarium head flight, commonly called scab, has plagued small-grain crops often in the last 10 years. Small grain acreage has declined in recent years in sugarbeet producing counties with no reason to suspect this trend won't continue. These changing cropping patterns have greatly increased interest in planting sugarbeet after soybean.
Sugarbeet Production Following Soybean
American Crystal Sugar Company's database clearly showed reductions in sugarbeet yield and quality when following soybean versus wheat in the 1980s and 1990s, Table 1.
Table 1. Sugarbeet yield after wheat and soybean.
|Years||Previous Crop||RSA (lbs)||Loss after Soybean (lbs)|
A comprehensive study conducted by Dr. Alan Dexter and Dr. Larry Smith from 1986 to 1988 documented severe yield losses if sugarbeets were produced following soybean versus barley, Table 2. Yield losses of over 1,000 pounds of recoverable sugar per acre were observed. They determined that (1) excess nitrogen after soybean, (2) potentially reduced available soil water, and (3) increases in root disease did not cause observed yield losses. They did document that use of herbicides like Treflan with carryover potential increased yield loss by up to 2,000 pounds of recoverable sugar per acre following soybean.
Table 2. Influence of previous crop and previous herbicide on sugarbeet yield and plant population. Smith and Dexter, NDSU/UM, 1986-1988.
|Previous Crop||Previous Herbicide||Yield (T/A)||Sucrose||Extractable Sucrose (lb/A)||Sugarbeet Stand (plts/70 ft)|
Sugarbeet Production After Soybean 2001-2005
Sugarbeet production after soybean has resulted in nearly the same revenue per acre compared to production after wheat or barley since 2001, Table 3.
Why the observed change in impact of soybean on sugarbeet yields and quality? Possible reasons might be (1) wetter growing seasons, (2) earlier planting of soybean fields, (3) Roundup Ready soybean reducing weed pressure, (4) no herbicide carryover, and (5) cool springs with warmer soils after soybean allowing better germination and emergence.
Table 3. Effect of preceding crop on yield and quality, 2001 - 2005.
|Preceding Crop||Planted Acres||Tons||Sugar (%)||SLM (%)||RSA (lbs)||Rev/A ($)|
Suggested Management Strategies for Sugarbeet Following Soybean
- Plant early to maximize yield.
- Be sure to use the 40 pounds/A soybean N credit.
- Use a starter fertilizer to maximize yield opportunity.
- Plant a spring cover crop on those prone-to-blow fields.
- Watch out for herbicide carryover if not after Roundup Ready soybean.
- Rhizoctonia root rot is common to both soybean and sugarbeet - monitor disease buildup.
- Consider Amistar use for disease control on fields with a history of rhizoctonia.
- Plant a resistant variety in fields with a rhizoctonia history.
- Contact your agriculturist for a complete data history of sugarbeet after soybean.