The Year in Review : the 2005 growing season will be remembered

Sitting here in subzero temperatures and looking back at the 2005 growing season, I think it will be a season that many of us will remember for a long time. Many growers have been frustrated with soybean yields for a while, and have talked about a yield plateau in soybean. Now I hope that we can start to reconsider that soybean yield plateau: our record soybean yields in 2005 were estimated by the United States Department of Agriculture (USDA) to have averaged 53 bushels per acre across the 10.1 million acres of soybean in Iowa.

During the past two years, we have harvested the third largest and the largest soybean yield per acre on record in Iowa and many farmers were able to make as much or more money on soybean than on corn in 2005.

So, why were our soybean yields so high? Well, there are many reasons. It all started in April, when the dry topsoil encouraged growers to get their corn planted early. Then a cold period followed, and some farmers hesitated to plant soybeans because the soil was not 55° F. But most farmers went ahead and followed our recommendation to plant at the optimum time because of the good seedbed conditions. The optimum planting date for the southern two-thirds of Iowa is the last week of April, and the first week of May for the northern one-third of the state.

Planting date is extremely important for high soybean yield. We have conducted 18 experiments over the last 3 years and 15 of them have showed a definite relationship between planting date and yield. There are risks associated with planting early, but, with the exception of a late spring frost, most of them can be managed.

Timely rainfall then followed for most of us throughout the season. We know that soybean and other plants with deep taproots, such as alfalfa, don't like to have "wet feet". The rainfall patterns definitely helped the plants develop good lateral roots. On the other hand, eastern Iowa had one of their worst droughts for many years and only received 5 inches of rainfall from early April to mid-August. I think we can all agree farmers in eastern Iowa were lucky that they picked up some "timely" rainfall at the end of August. I know for sure that our friends in Illinois appreciated the rain they got in August.

It could have been much worse, but as we have seen some many times before, rainfall during seed filling in August can have a significant impact on yield since a greater seed size on the few seeds that are set can increase yield significantly.

Only a few foliar diseases were observed in our fields during the 2005 season, which is typical for Iowa. Bacterial blight and septoria brown spot were the two most commonly observed.

Bean leaf beetles were present early in the spring, but not many fields reached threshold. Soybean aphids on the other hand showed up in early June in northeast Iowa. It is estimated that approximately 2.1 million acres were sprayed for aphid management in Iowa. Yield loss from soybean aphids is assumed to have been minimal since fields were scouted intensively, with good knowledge of threshold levels, and growers pulled the "trigger" at the right time when needed.

On the other hand, we again lost yield from the soybean cyst nematode (SCN). Greg Tylka has warned us for many years about the widespread yield loss from this nematode and we still don't seem to get the message. Many farmers learned this the hard way in 2005 since the greatest damage from SCN occurs in dry years. In our high-yield studies this year, our top 8 or 9 soybean varieties all had resistance to SCN - even in locations where SCN was not a significant problem! There is no yield drag associated with SCN-resistant varieties as there may have been in the past. Yield loss from SCN was estimated to be around 50 million bushels in 2004. Who wants to take a guess on 2005?

2005 was a good year for soybean producers. Hopefully, it restored some promise that we can achieve high yields. I think that many will start to realize that it is not impossible to obtain high soybean yields, but that it takes a lot of effort. It is not as easy as plant a "random variety", spray a herbicide, harvest 3 months later and expect a bumper crop. It takes a lot more. Variety selection is the foundation for a bumper crop and that is something we just can't afford to compromise on anymore. After that, fundamental agronomics should be optimized for each field. And finally, scouting should be done frequently and follow Integrated Pest Management (IPM) guidelines to be sure that no pathogens, weeds, or insects are limiting our yield.

From all of us here, we wish you a Merry Christmas and a Happy New Year.