Thursday, March 10, 2011
Soybean Yields: Are RR2 Beans Really Better Than Original RR Varieties?
You have been raising Roundup Ready soybeans since 1996 or thereabouts and probably don’t plan to change any time soon. They have made life easier, and the older you get, the better that is. But now there are Roundup Ready 2 Yield or RR2 beans and there may or may not be a yield improvement. What is the difference between RR and RR2 soybeans anyway?
Purdue soybean agronomist Shaun Casteel presents a webinar on the Plant Management Network that you can listen to at your convenience. One of his first points is the rate of yield increase, which began at 10 bushels per acre in the 1920’s and has risen to 43 bushels, which equates to an increase of one third of a bushel per acre per year. Interestingly, IA and IN have had a yield increase of .44 and .43 bushels per acre per year, MN comes in at .42, IL is at .39, and OH is at .36.
RR soybeans make up about 91% of all soybeans planted. When the Genuity RR2 beans were released in 2009, about 11 varieties were available for 1.5 million acres. In 2010, 87 varieties were available for planting, and that will increase to 239 for 2011. Casteel quotes Monsanto materials in says that RR2 beans have a 7 to 11% yield improvement over RR beans, and the varieties to be released in 2011 have a 1.1 bushel advantage over the varieties released in 2010 in the tests that were conducted last year. Monsanto has indicated that 3-bean pods will number about 50 on RR beans and 55 on RR2 beans, with an additional 5 beans per plant. But Casteel says there cannot be any direct comparison since the varieties are different, and questions if the older varieties can really yield as much as the newer varieties because of the genetic differences.
Casteel says yield consistency not only depends on genetics, but also on weather, soils, cultural practices, diseases, insects, SCN pressure and other factors. To help evaluate the yield difference, Casteel has gathered multi-state data http://www.ag.purdue.edu/agry/pcpp from IN, IL, OH, MI, and KY, which can be separated out by variety, state, maturity, and trait, with combinations of comparisons. Among the growing regions in IN, where Casteel’s tests were taken, the same variety may have as much as a 25% difference in yield among various test plots. Across states, RR2 beans in maturity group 2 in MI had a 1.4% advantage, but a 2.9% disadvantage in IL and a 1.6 disadvantage in OH. Yields were equal in IN. When maturity group 3 beans were compared, KY had a 2.9% yield disadvantage for RR2 beans, but they outyielded RR beans in other states, anywhere from 0.6% in IL to 2.8% in OH. For maturity group 4, IL had no yield difference between RR and RR2 beans, and the RR2 beans had lesser yields than RR beans in IN and KY.
When Casteel looked at yield trials in WI, RR2 beans usually had a yield advantage over RR beans. In MN, Casteel says the beans raised in southern MN indicated that RR2 beans had a greater tendency to reach their maximum yield. Of the top 5 varieties RR2 had a 3.3 bu yield advantage over RR beans. In central MN, the RR2 varieties were again closer to their maximum yield, and they had a 3.9 bushel yield advantage. The outcome of the tests indicate that upper latitude states, such as MI, MN and WI will all see a greater yield with RR2 beans over RR beans. That could be the result of earlier maturity groups that might have a better genetic potential, along with the potential benefits of seed treatments due to cool soil, diseases, and early season insects.
When seed treatments were examined, all of the RR2 beans had a fungicide, insecticide and some had a growth promoter. He says the goal is yield potential and consistency, but each kind of beans scored at the top, middle and bottom of the comparison. Once comparisons are made with the same type of soybean and the same environmental and cultural practices, differences may be minimized.
Summary:
While RR2 varieties are said to be better yielding than original RR beans, there may be differences in the way the soybeans were raised, instead of the genetic potential. Frequently, newer varieties will have benefits not provided to earlier varieties, and yields will be different. When comparisons are made, all relevant factors should be equal.
Posted by Stu Ellis on 03/10 at 01:44 AM | Permalink