Now that they're finished with harvest, corn and soybean growers are sending in yield and other final data on replicated strip trial studies they've done in 2012 in cooperation with the On-Farm Network. "We're processing those results now and analyzing the data as quickly as possible," says Tracy Blackmer, director of research for the On-Farm Network. "The results for 2012 of the various trials that we have finalized so far are posted on our website, by trial type."
The On-Farm Network is a testing program sponsored by the Iowa Soybean Association. Various agronomic and crop management practices were compared in real field conditions on the farms of the farmers who participated in the Iowa On-Farm Network's 2012 testing program.
"While several of the trials revealed some interesting yield responses, one final report in particular sticks out," says Blackmer. "You may remember that we reported finding significant rootworm damage in one of the trials where we were testing a half rate versus a full rate application of Aztec insecticide for corn. That was reported earlier this fall in our September 20 newsletter."
The accompanying photo shows an aerial view of lodging of corn in the insecticide trial in a field in north central Iowa. This lodging was caused by rootworm feeding. Blackmer says the lodging was documented by taking aerial photos using a fixed-wing, radio controlled drone aircraft on August 27, 2012.
Lodging in this Hardin county trial was severe enough that it was easily picked up from the aerial imagery collected in late July and early August, says Blackmer. On-Farm Network staff followed up on the imagery by scouting and documenting the lodging differences in these fields. The final report on the half-rate of insecticide vs. full rate of insecticide trial is now posted on the On-Farm Network website. This particular trial was continuous corn, planted to a hybrid with a Bt gene for rootworm control.~~~PAGE_BREAK_HERE~~~
"While the lack of rootworm control in the half-rate insecticide strips was evident in the aerial imagery and in several subsequent scouting trips where we walked into the field and took a look, the corn yield difference was not as great as we might have expected," says Blackmer. "Where the full rate of insecticide was applied, the strips yielded an average of 3.4 bushels per acre more than the half-rate strips. Economically, the full rate paid well. It paid to apply the full rate of insecticide."
Final yield results for 2012 are also now in on four other central Iowa trials on the same subject, also in continuous corn. Three of the trials testing Aztec at full rate vs. no insecticide applied had yield responses of 7.1, 11 and 12.4 bushels per acre. The fourth trial tested SmartChoice insecticide against no insecticide applied. Yield response to the added insecticide in those strips averaged 24.9 bushels per acre. "Final reports on these trials will be posted soon on our website," says Blackmer.
Better yield from applying a full-rate of insecticide isn't the whole story, however
Better corn yield from applying the full-rate insecticide is not the whole story on the Hardin county trial mentioned earlier. Despite the amount of root damage and the serious drought that hit this field this year, the average yield for the entire trial area of the field was more than 200 bushels per acre, not far below the grower's long-term average corn yield for this field.
"This brings up a lot of questions we don't have data to answer," notes Blackmer, "like what might have happened in a year with normal rainfall? But it does speak well of the grower's decision to keep growing corn on this particular field and it also suggests a lot about the full genetic make-up of the corn hybrid he chose to plant there."
"You should take a look at the rest of the 2012 On-Farm Network strip trial results as we get them posted," says Blackmer. "You may find some other surprises among them. As always, if you'd like to talk about something you see in the trials results, or would like more information about any of the On-Farm Network studies, feel free to contact us at the Iowa Soybean Association office in Ankeny any time."