Results from soybean nutrient management trials
High Yield Trial
Five practices were evaluated for their effect on soybean yield:
- Breaking apical dominance at V2 to increase branching and pod number
- Applying 5 lb/ac starter N in furrow with split emitters
- Applying foliar nutrient NPK + micronutrient (as above) at R2
- Adding BioForge seed treatment at 4 oz/cwt
- Adding Optimize 400 seed treatment
This was an omission or minus-one trial so that the effect of practices could be tested in the presence of all other practices.
- None of these practices used
- A full package with all five practices used
- Five treatments which consisted of the full package minus one of the above five practices.
- Full package with plants clipped at the second trifoliate stage to break apical dominance replaced by a 12 oz/ac lactofen “Cobra” application
The sites were tilled and planted in 20-inch rows. A strobilurin fungicide was applied at R2 and 25 lb/ac N was soil applied at R3 (beginning pod development) for all plots.
Starter N was applied as diluted UAN in furrow by injecting 5 lb/ac N in the seed furrow using split emitters to minimize N contact with the germinating seed and avoid seedling injury. Foliar nutrient application was as above at the R2 growth stage. Seed was treated with BioForge at 4 oz per 100 cwt to promote vigorous early root growth for improved nutrient and water uptake. Seed was treated with Optimize 400 to promote plant growth and ensure good nodulation for N fixation.
The effects of these practices were consistent for all locations. Clipping and Cobra (lactofen) application reduced yield (Table 3). The other treatments had no positive or negative effect on yield.
- Mean yield was 66 bu/ac in the starter/foliar trial and less in the high yield trial. Treatments had little or no effect on yield and these results from four locations should discourage use of all the practices tested, especially clipping or Cobra application to break apical dominance. Still, it is possible that some of the practices tested may be useful in much higher yield situations.
- Further evaluation of the foliar nutrient application at R2 is justified. NRage and Soygrow might be tested separately to confirm the yield increase and determine which nutrients might cause the yield increase.
- Starter N application had a good test at Bancroft where crop residue cover was heavy and cool weather followed planting. While some starter N treatments enhanced growth, this did not translate to increased yield.
- Treating seed with Bradyrhizobia inoculum is encouraged where soybean has not been grown for four or more years or where flooding occurred, but the results do not support routine inoculation for the corn-soybean rotation.