NASS OBJECTIVE YIELD SURVEY FOR SOYBEANS
Below is a chart supplied by NASS indicating what they used for an “Implied Pod Weight” after calculating todays’ yields in the 11-State Objective Yield Survey. The enumerators have gathered information on the number of PODS in each 18 Square Foot test-plot, but due to immaturity unable to provide an actual pod weight.
So if NASS is 100% certain on yield forecast, they are then able to (back into) provide the public with an Implied Pod Weight. The formula for calculating the soybean yield for 11-Objective Yield-State is # of pods * pod weight* 0.0889 = Yield. So if we know the # of pods 1,561(they’re counted) *0.3492 (Implied pod weight backed into)* .0899= 48.459 BPA for an 11-State average yield.
What would happen to yield if “implied pod weight” falls to the 5 year average weight of 0.3157?
# of pods 1561*0.3157 (5-Y-A) *.0899= The above 11-State Objective Yield is now 43.8 BPA
NASS argues that the number of pods always increases during the growing season (not the case in 2012). So if we take the 5 year average gain from Sept to Final, the increase amounts 103 additional pods for a total of 1,664. Normalized gain in pod count of 1,664 * 5-Y-A pod weight of 0.3157 * 0.889= 46.70 BPA.
On the next page, are a couple charts depicting history of monthly pod weights and pod counts.
The following questions remain to be answered;
- With 8% of soybean crop w/o pods as of last Sunday, would this justify a significant increase in # of pods in the future NASS production reports?
- With many producers acknowledging that the majority of the crop is 2-4 weeks behind conservatively, could pod weights fall even below the 5YA?
Example pod count increases to 1,613 (1/2 normal gain) * 0.3025 (poor pod weight)*0.889 = 43.37 BPA
What would occur to pod weights & pod counts should killing freeze occur early, possibly @ normal time of year?
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