Deep soil profile bacteria – recent findings affected by Strip Till.

Science of soils, a pursuit I have engaged in for over 50 years has been rewarding and yet quite challenging to consider the wide spectrum of physical, chemical and biological factors that affect plant growth.  From the very start of a seed placed into the surface horizons of the soil profile to the time the plant transcends to senility and is ready for harvest or the completion of the flowering stage and dies – the soil is intricately stitched into the plants life cycle.  Considering all of the physiology of the plant, it’s chemistry of what goes on via photosynthesis, the association of microbes on the roots, those microbes that live on the outside plant tissues, heat and cold responses of the above ground parts to the roots in the soil, what a complex and intricate system.

The graphic to the right depicts when soils dry out what happens to the soil bacteria populations in the upper reaches of the soil profile in many cropland soils.  This information I read twice to absorb all the terms from “Frontiers in Plant Science” by Naylor and Coleman-Derr.

Conceptual diagram of drought stress changing biology in soils. Courtesy: Naylor & Coleman-Derr, Frontiers in Plant Science, 2018

For the grower of foodstuffs we far too often take for granted this all happens with very few glitches.  Oh sure the rain does not come as we like or prefer, wind blows like the nasty derecho of 2020, frozen water in the form of hail stomps and rips plants to pieces and we take our lumps even shed tears.  We at Orthman consider how we engage with growers to minimize tillage, help with you managing your soils to minimize any and all erosion by wind and water, offer you good options to place nutrients in the pathway of the crops root system and a systematic approach of growing your row crops.  Strip tillage ever since the concept arrived back in the 1980’s and hesitantly has been adopted, we offer the Orthman 1tRIPr originating out of southwestern Nebraska by a good friend of mine to be a tool in a farmers crop management toolbox.   A useful and good tool is known beneficial by the worn paint, replaced parts at the right times, placed under a roof, known exactly where to be found, talked about how handy it is and how long it has been in use.  Much like my grandfathers 12 ounce hammer he passed on to me with the original handle of ash, handle is worn where gripped since the early 1920’s, few chips and has tapped in thousands of nails.

 

 

 

 

 

 

Proteobacteria – very mobile with flagella to push them around in soil solution

IMPORTANCE OF SOIL MICROBIAL FAMILIES:

What does that you say, have to do with roots, green leaves and here soon planting seeds for much of the U.S. to grow green crops across the summer months?  For you strip tillers, knowing that your strip till unit will till the narrow strip right where you want to place seed, at a specific depth you can apply and place nutrients, accomplish this at a best thought out rate and the right time with the right material.  Following this you are doing the best to protect the soils resources from erosion keeping last years crop residues (which some growers have dubbed as hay – why hay, because one man told me it is hay/feed for the microbes) to maintain the cycle of life in the soil.  I find what this grower in North Texas told me that I knew he has the right attitude and concept of soils in order to grow sustainable top yielding crops.  The science of how soils churn and turn in situ (right in it’s rightful place) and give up water or take it in, make nutrients available in a correct form, exchange gases, cool and heat up, and continue as a medium for plants to live and thrive continues to fascinate me.  From all this love affair with “Dirt” I want to bring items I learn about to you all, get to experience and yes fill your heads to a breaking point of slow down Petersen.

For those of you who are paying attention to soil health and what all that means to being successful and continuing to grow crops that are high producing and economically steady for your budget; I am learning more and more about microbial families that inhabit soils at depths all the way to 😯 inches deep.  Unfortunately the talking heads about soil health usually don’t discuss the one celled critters down below 40 inches, we are reading about and finding certain species are more prevalent below than in the upper 1 foot of the soil profile.  Several of the deep to very deep living bacteria of the Proteobacteria are known to fix nitrogen for spruce and Lodgepole pine trees. Others will use organic acids from root secretions and in turn deposit elemental sulfur potentially available for uptake.  Alcaligenes are found deep in soils where nitrates or nitrites are present and will digest raw minerals in the soil making it available to plant root uptake.  Proteobacteria are the largest group of bacteria below 45 inches in many of agricultural soils.

TILLAGE PLAYS A ROLE IN MICROBIAL LIFE OF THE NEAR SURFACE AS WELL AS DEEPER PARTS OF THE SOIL PROFILE

Another important find, conventional tillage will enhance different species at depths compared to Conservation till such as Strip tillage or No-Till.  Specific bacteria  thrive in the upper 30cm (12 inches) and others like the cooler less range in temperature of the depths below 39 inches.  Quite interestingly with depth and higher bulk densities, the richness of soil bacteria may be under 280 different species down to as low as 11 different species in over 700 hundred soil thin sections analyzed.  This suggests that within a neighborhood of bacteria in deeper sections of a soil profile (>36 inches deep) the diversity of bacteria is low and tells us something about how they interact with cultural events such as tillage above them in the upper reaches of the soil profile. Also microbiologists are accounting for the lack of variability in bacteria species at deeper depths due to the organic substrates from plant/root tissues.   As I consider this it makes sense unless the management of soils includes several crops in rotation and deep rooted crops versus less prolific rooted crops.

A conclusion made from several scientists that deep soils are a critical zone for carbon sequestration and too often today the issue of what goes on below 30cm (12 inches) is not considered and those bacteria down deeper (Proteobacteria) are aiding in storage of carbon. This begs the question for students of soil health, who is doing what and how do they interact with one another to store carbon and if less tillage accentuates the potential to store carbon and nutrients deeper – this needs studied more.

We can say to these findings; great stuff, we already knew strip tillage was beneficial to healthier soils, now this may indicate it is making a difference down deep.  At Orthman Manufacturing we are wanting to know more about the entire soil profile, not just the upper 12 inches.  As we learn what Strip Tillage accomplishes by our own research and what others across the globe learn, it is our intent to make it available to you.

 

REFERENCES:

Naylor, D., and Coleman-Derr, D. 2018, Drought stress and root associated bacterial communities. Frontiers in Plant Science, January 2018 | https://doi.org/10.3389/fpls.2017.02223