Thursday, September 15, 2011

Effect of Freezing on Soybean Seed Yield and Composition

Greg Andrews from Pierce County received many texts from growers this morning that reported temps ranged from 23 to 29 across the county, 23 in valleys and 27-29 lasting from about 3am to 7am for much of the upland corn and soybean growing regions. His early observations in soybean fields with green stem and leaves indicated that cell rupture and wilting was already obvious (Images 1 and 2). The next question is how much yield loss will this injury translate to. Saliba et al. (1982). reported that the latest growth stage at which significant yield loss occurred due to freeze injury (80% leaf loss) ranged from R6.0 to R7.2 with an average growth stage of R6.6. For the most part the WI soybean crop is in the R6.5 to R7.5 growth stage. This suggests that there is a potential for yield loss, but the extent will be variety dependent. Saliba et al. (1982) also reported that the yield loss from this crop injury will be due to a reduction in seed size and not seed abortion. Lastly, Saliba et al. (1982) suggested no impact on seed protein or oil content when freeze injury occurred after R6.3.

Frost injury to soybean (photos courtesy of Bill Halfman)

Given the dairy industry in the state some growers may consider taking the soybean as a forage. Just remember to contact your crop insurance agent before you do anything.

Literature cited:

Saliba, M.R., L.E. Schrader, S.S. Hirano, and C.D. Upper. 1982. Effects of Freezing Field Grown Soybean Plants at Various Stages of Podfill on Yield and Seed Quality. Crop Science. 22:73-78.

Wednesday, September 14, 2011

Potential for Soybean Yield Loss Due to Frost

The threat of a killing frost across WI has many growers concerned about the potential yield loss to soybean. The soybean fields that I have scouted over the last week are well into the the R6 growth stage (full seed: pod containing a green seed that fills the pod cavity at one of the four upper most nodes on the main stem with a fully developed leaf). In fact as of Monday 9/12/11 8% of the soybean varieties had reached physiological maturity (R7) at our Arlington site. On average a soybean plant remains in the R6 growth stage for 18 days; however the range can be as short as 9 days or as many as 30. As we move through the R6 growth stage and into R7 soybean seed moisture declines thus decreasing the risk of yield loss due to frost. Judd et al. (1982) found that seed in green pods which contain 65% moisture are injured at 28 °F whereas seed found in brown pods at 35% moisture was not injured at 10 °F. If frost damage is suspected remember that frost damaged soybeans will dry slower in the field and accuracy of moisture sensors may be suspect (may be 1-2% higher than the moisture meter reading) (PM 1635).

For more information on storage issues and uses of frost damaged soybean read page two of: Frost Damage to Corn and Soybean.

Literate cited:

PM 1635: Frost Damage to Corn and Soybean.

Judd, R., T.M. Tekrony, D. B. Egli, and G.M. White. 1982. Effect of freezing temperatures during soybean seed maturation on seed quality. Agron J. 74:645-650.