However, at the same time, farmers are also wondering if the cover crop will suck up too much moisture from the soil and aggravate the already excessively dry subsoil moisture conditions. "These two questions are good questions, and they are just a few of the questions we're hearing from farmers," says Blackmer.
In order to collect Iowa data that will better address growers' questions, the On-Farm Network is coordinating a number of cover crop trials on the fields of cooperating farmers this fall.
More on-farm trials will be conducted this fall to find better answers to these questions
"We have conducted cover crop studies in the past and they have shown that a cover crop can produce a significant amount of cover to protect soil and a lot of nitrogen can be taken up with less chance of the N being lost to leaching," says Mick Lane, communications director for the On-Farm Network. Lane and Blackmer encourage you to go online to 2008 Replicated Strip Trial Summary pages 12-13 and read the article and look at the results of those previous trials in the tables accompanying that article.
"One thing to keep in mind is that since the nitrogen taken up by the cover crop is then tied up in the organic matter, just when it will again become available for the corn crop or soybean crop to use is unclear," notes Lane. "What we do know is nitrogen release from organic matter (such as crop residue and manure) is dependent on a number of factors including soil moisture, soil temperatures and activity of soil microbes. Even in states like Indiana where there's much broader use of winter cover crops and they've been using cover crops for a number of years, there are no nitrogen credits for cover crops listed in their fertilizer recommendations at this time."
What most growers seem to be concerned about is how cover crops might impact yield of the corn or soybean crop that's planted in the spring after the cover crop is killed. "To answer this question for Iowa soils and Iowa conditions, we need a lot more data for many different scenarios in Iowa," says Lane.
So, if you're seeding cover crops this fall (or just considering the idea) and would like to be part of a project to collect the data needed for a more complete assessment, "please contact us," says Lane. "We have seed available for a few trials, or if you have your own seed, we can help you design a replicated strip trial that will generate the type of data needed to advance our knowledge of cover crops for Iowa."
Whether you have cover crops or are just interested, if you have questions about them, email them to Mick Lane, the On-Farm Network communications manager and he will attempt to collect the information to answer your questions.