Monday, March 11, 2013
Soil Rhizobium Counts
"Ed, Where do you send your soil to test for Rhizobia counts? We are talking here in EKS about the low counts from the last 2 hot dry years. but would like to test soil to know for sure. What caused your low counts? heat, low moisture ?
My detailed reply: "Good morning, Robert.
I have 2 friends that look at soil for me on the side who don't do this as a business. I made friends with a couple of lab people and their time is limited. I saw enough to say what I did. I got some spadefuls of soil in my travels of farms where the soil was pretty biologically dead.
Your inoculant supplier might have a lab where they can do this, it is not easy or cheap work. I can't name you a lab that does, maybe someone can.
I found my quote from last fall in my blog but the link doesn't take me to the article! http://hymark.blogspot.com/2012/08/swoga-and-rhizobia-survival.html
"Soybean rhizobia bacterial cells survive best when they are in a moist soil environment and an ambient soil temperature of 40-80 degrees F. The drought throughout the Ohio in 2012 has resulted in the top six inches of soil becoming extremely dry and very hot in many fields. Either a very dry soil environment or a very hot soil environment causes the rapid death of rhizobia cells and the combination is lethal. Therefore, we would expect a reduction in the population of residual soil rhizobia cells in many Midwestern soybean fields in 2012 due to those soil conditions.
Although many cells will survive the extreme environmental conditions, those cells will have evolved into survival mode and will have lost much of their potential to provide nitrogen to soybean plants in 2013. That means the surviving rhizobia population will likely be less productive next year than in previous years. That reduced productivity should translate into increased yield responses to inoculating soybeans and other legume seeds in the spring of 2013."
This link says BDS labs in Saskatchewan do counts for $30.
I would think someone near Kansas can peform the test you need? The lab needs to be able to culture and estimate soil rhizobium counts but it could be a needle in a haystack!
I hope this helps, Robert.
What caused my low counts? Continuous corn, lack of soybeans, 3 years of hard weather, lack of cover crops from newly acquired farms or farms I have not farmed and probably various other reasons.