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This is Dr. Nathan Mueller, your local agronomist with Nebraska Extension for Dodge and Washington Counties. We must scrutinize inputs and focus on finding profit for our estimated 5.3 million acres of soybeans in Nebraska this season. During soybean planting season we often think of planting date, seeding rates, and seed treatments. In regard to seed treatments, one of the choices being made right now is “Should I inoculate my soybeans?”
The process of fixing nitrogen in the soil air to ammonia occurs through the symbiotic relationship between soybeans and the Bradyrhizobium bacteria within the nodules of soybean roots. This process provides soybean plants up to 75% of the N they need; the remaining amount is taken up from the soil.
Your soybean field likely fits into one of three situations. First, your field has no previous history of soybeans, but rather few fields like this are left. Second, it has been more than five years since soybeans were grown or soybeans have been grown in rotation every two to three years, but an environmental factor may have negatively impacted survival of the bacteria. Third, soybeans have been grown in the rotation every two or three years and environmental conditions have been good.
In the case of situation number two, several environmental factors can cause poor nodulation, decrease nitrogen fixation, and reduce survival of these bacteria, including non-optimal soil pH, an extended flood or drought. In these situations, yield increases of 1 to 10 bushels per acre could be expected by using inoculants.
The probability of a yield response in fields with a recent history of soybeans and good conditions for bacteria is extremely low. An eight-year study from 2000-2008 tested 51 inoculant products in 73 experiments in Wisconsin, Iowa, Indiana, Minnesota, and Nebraska and the average yield response of 0 bu/ac. If you have managed soil pH well, planted soybeans recently, have medium to heavy textured soil, and have not experienced extended droughts or floods, direct your money away from inoculating soybeans and move it to other management options that have an improved chance of return.
For more information on the need to inoculate soybeans in Nebraska, call me at 727-2775 or visit our local website at croptechcafe.org. Know your crop, know your tech, know your bottom line. This is Dr. Nathan Mueller, your local agronomist with Nebraska Extension on KTIC radio.
