Yield Observations When Shifting to Earlier Relative Maturity Soybeans -  2020

• We continue to see a growing trend for soybean growers to plant “early” soybean products and manage them at a higher level with seed treatments and foliar applications of fungicide and insecticide. This phenomenon, dubbed “relative maturity (RM) shift” is becoming increasingly important in some locations.

• There are many benefits of planting “early” soybeans including, but not limited to, earlier harvest timing, earlier cover crop seeding, and risk management benefits. 

• The objective of this study was to determine the yield impact of planting “early” RM soybean products compared to planting normal RM products for the location.

SITE NOTES:  

• The trial consisted of two sets – North and South. 
• There were five locations planted: 
  • North set – Storm Lake, and Marble Rock 
  • South set – Huxley, Atlantic, and Victor 
• Each set consisted of three unique soybean products. 
  • 3 soybean products were considered early RM for the location: 
    • North set – 1.2 to 1.8 RM 
    • South set – 1.9 to 2.4 RM 
  • 3 soybean products were considered normal RM for the location: 
    • North set – 1.9 to 2.4 RM 
    • South set – 2.9 to 3.7 RM 
  • The 1.9 to 2.4 RM group consisted of the same three soybean products for both of the North and South sets. 
• The trial included a mix of plot sizes, replications (reps), and row spacings: 
  • Storm Lake (2 reps): six row strips with 20-inch row spacing 
  • Atlantic (2 reps) and Marble Rock (3 reps): four row strips with 30-inch row spacing 
  • Huxley (2 reps): six row strips with 30-inch row spacing 
  • Victor (1 rep): eight row strips with 30-inch row spacing  
• Average rainfall during the growing season was very low compared to long term averages with 3 to 15 inches less rainfall, depending on location. 
• Marble Rock was impacted the least with 3 inches less and Atlantic the most with 15 inches less rainfall.  

• With earlier planting dates in 2020 and rainfall events in September, the effects of RM selection on average soybean yield pointed to a clear yield advantage for the normal RM group. 

• The North set normal RM group had a 7 bu/acre advantage over the early RM group (Figure 1) and the South set normal RM group had a 13 bu/acre advantage over the early RM group (Figure 2).

• In 2020, early RM soybean products yielded, on average, 7 to 13 bu/acre less than normal RM soybean products and ranged between +4 to 21 bu/acre less than normal RM soybean products for both locations.

• In 2020, late season rainfall was less than ideal. The lack of adequate rainfall in July and August quickly finished off the early RM group, while the early September rains helped the normal RM group maximize pod fill.

• More research should be conducted in the genetic pipeline to better understand which soybean products can be grown south of their typical production area.

• It should be noted that a RM shift may not be applicable for every operation and any potential benefits can be defined in terms other than yield.

Yield Observations When Shifting To Earlier Maturity Group Soybean Products - 2019

• A growing trend for soybean growers is to plant “early” soybean products (south of their normal adaptation) earlier in the season and managing them at a higher level with seed treatments and foliar applications of fungicide and insecticide.  This phenomenon, dubbed “relative maturity (RM) shift” is becoming increasingly important in some locations.
• There are many benefits of planting “early” soybean products including:
  • Earlier harvest 
  • Earlier cover crop seeding
  • Risk management benefits 
• The objective of this study was to determine the yield impact of planting “early” (for the location) RM soybean products compared to planting normal RM products for the location.

• The trial consisted of two sets – North and South.
• Each set had three Iowa locations: 
  • North Set – Storm Lake, Marble Rock, and Huxley
  • South Set – Huxley, Atlantic, and Victor
• Each RM group consisted of three unique Channel® brand soybean products.
  • Three products were considered early RM for the location:  
    • North Set – 1.2 to 1.6 RM
    • South Set – 1.8 to 2.4 RM
  • Three products were considered normal RM for the location: 
    • North Set – 1.8 to 2.4 RM
    • South Set – 2.9 to 3.7 RM
  • The 1.8 to 2.4 RM group consisted of the same three products for both the North and South sets.
• The trial was a mix of plot sizes, replications (reps), and row spacings:
  • Storm Lake (4 reps)—six row strips, 20-inch spacing
  • Atlantic (2 reps) and Marble Rock (4 reps)—four row strips, 30-inch spacing
  • Huxley (3 reps)—six row strips, 30-inch spacing
  • Victor (2 reps)—eight row strips, 30-inch spacing
• During the growing season, all sites recorded 20+ inches of rainfall with Atlantic receiving 32 inches total. 
• The Marble Rock site received several heavy rainfall events. 

UNDERSTANDING THE RESULTS

• Delayed planting dates in the spring and late rains in the fall favored the normal RM group at the sites tested in 2019.
• The normal RM group had a 6.0 bu/acre advantage over the early RM group at the North and South locations (Figures 1 & 2).

KEY LEARNINGS

• In 2019, the early RM products yielded, on average, 6.0 bu/acre less than the normal RM products and yields ranged between 3 to 10 bu/acre less than normal RM products.
• In 2019, rainfall was plentiful with Marble Rock receiving the heaviest one-time event, and with Atlantic receiving over 32 inches total.
• The 2019 growing season favored the normal RM products, especially with a few delayed planting dates and excessive late-season rainfall that the normal RM group was able to utilize.
• More research needs to be conducted in the genetic pipeline to better understand which soybean products can be grown south of their main area of adaptability. 
• It should be noted that a RM shift may not be for every operation and that its benefits could be defined in terms other than yield.
  
  
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