For a refresher these are the reproductive stages of a soybean plant. The stages seem complicated, but you just have to look at the top of the plant to make the assessment.
R3 - Beginning pod, short pods visible in top 4 nodes of the plant.
R4 - Full Pod, pods 2 cm long at top 4 nodes of the plant.
R5 - Beginning Seed, seed .3 cm long at top 4 nodes of the plant.
R6 - Full Seed, seed in upper pods fills the cavity.
The R5 stage is the most critical for yield development. The soybean plant can shake off earlier problems and still produce high yields if weather co-operates during this stage. It is why Horst Bohner will say it does not matter what happens to the crop until August. He is right. What is sometimes not mentioned however, is the effect of maturity in the yield equation. That is why we are looking at full season soybeans planted early, May 11 and late (for this year), May 26.
The reason we looked at 92Y12 is purely yield. This is one of the highest yielding group 2 varieties on the market. Last year in our strip plot it yielded 72 bu/acre harvested on October 12. We would not be doing our job as a Pioneer rep if we did not push the edge of maturity to see if it makes sense for some of us to try it on a larger scale.
The May 11 planted 92Y12 were still producing a few flowers at the top pf the plant last week. This is the late stages of R4. The upper pods are forming.
The May 11 planting date is just entering the R5 stage.
For comparison we also have late group 0 soybeans planted on May 11. A late group 0 variety is approximately 2750 CHU.
Soybeans in this maturity are well along in R5 and approaching R6. These beans have had extreme heat and drought stress to contend with. The R5 and R6 stages are both about 2-3 weeks in duration under normal circumstances. Where the drought is worse it appears the early varieties have rushed through the R5 period quicker than normal. What effect will this have on yield? Probably negative. It is way too early to make many predictions. August and September weather will decide who wins the gold in this race.