Soil Field Condition vs Lab Tests

These pics are examples of WW crops from two different tillage systems.  Both of these crops look pretty good as of April 13th, 2021.

<-----  Pic on the left is an example of 2021 WW on long term conventional ground.  This  crop was seeded on chemical fallow grnd.

<---- Pic on the left is an example of 2021 WW on ULD grnd.  This area was seeded too shallow and got a late start.

        This winter/spring I had a unique opportunity to run a lab test on two soils that have very different history.  One soil has ~30 years of no-till, with the last eight years being ultra-low disturbance no-till.  The other field, a couple hundreds yards away has a history of one hundred plus years of conventional tillage/cropping, with no no-till history.  Both locations were fairly level with low erosion from weather, although a difference in tillage erosion would be apparent.  The no-till field has a large amount (mat) of residue, and the tilled field has a small amount (a lot of open ground) of residue.   I had high expectations of seeing a dramatic difference in OM, EC, BD, Respiration, and some differences of several macro and micro nutrients.  WHAT A DISAPPOINTMENT!!  Some numbers were the same, and some showed slight differences, but all in all, no revelations.  This lab is not the general run of the mill type that we are all accustomed to.  I have used this lab for a couple of years for different projects. 

    Physically there is a world of difference between these two fields.  April 13th with no measurable rain since March 23rd the ULD grnd was soft to walk across, where the tilled field was hard under foot.  Sinking a 1"diameter soil probe into the ULD field was easy, down the full 4 ft length of the probe, where the conventionally tilled field was very difficult down to ~18", where resistance eased up (maybe even softer than the ULD field in the lower 2'.

        Why didn't the lab show differences as expected?    Two things come to mind.  1)- In my mind this was such a no brainer that I was careless taking the samples.  My process of taking an undefined slice of soil using a narrow trenching shovel was bad technique.  A lot of possible error could result.   2)- This supports my comments on earlier posts about lab testing, and difficulty in trying to show value of no-tilling through our long recognized lab protocols. 

     I'm convinced that no-till deals primarily with the physical component of soil health, but secondary to other processes like biological diversity and nutrient recycling.  Biological activity has to be helped with cover crops and possibly reintroducing microbiological species through well prepared compost and compost teas.   No-till is significant in improving soil drainage, and it reduces destruction of soil organisms community life.    No-till is the first step required for us (in the Palouse) in developing a healthy soil.  With few exceptions, our environment will not support tillage and develop a healthy soil.   Comparing infiltration rate, wet aggregate stability (SLAKE test), visual soil structure, and earthworm count is easy to do and shows dramatically what no-till brings to the table relating to soil health.  Bulk density should be an easy comparison, but the penetrometer is effected by moisture content, soil type and other factors that vary from point to point.   So, what do I conclude?  As many of my earlier posts mention, a no-tillage farming system, is very effective in building soil structure over time.  A no-tillage farming system, when coupled with high surface residue (soil armor) is very effective in controlling erosion from tillage, water, and wind.  A no-tillage farming system is helpful in slowing evaporation when coupled with a protective mat (soil armor) on the ground, and even more effective if also coupled with standing stubble.  Moisture is lost principally through evaporation, not crop production.  Keeping soil surface temperature down, and a low wind velocity along the soil surface, saves moisture that can be used by the crop.  Another benefit to a no-tillage system and heavy mat of residue is reduced competition from weed species, either broadleaf or grasses.  We see it consistently year after year when comparing our neighboring fields with either conventional tillage or high disturbance no-till.  Unfortunately, we still have to apply herbicides like everyone else.

Value of low disturbance Direct Seeding

I had the opportunity to compare a field with long term low disturbance direct seeding history with a bordering field having a 100+ year history using a conventional tillage system. 

The pic on the left represents the field with the 100+ history of tillage.  The pic below (middle) represents the field with a long history of low disturbance direct-seeding.  In 2020 both fields were in chemical fallow.  The field in the top pic was chem fallow on spring wheat stubble. and seeded with a high disturbance drill.  The field in the middle pic was chem fallow on spring canola stubble.  It was seeded with a low disturbance drill.

  Observation:  Both fields were thawed.   This condition followed 10 days of hard freeze that provided ice sufficient to skate on our pond.  A quick thaw followed.  The field (top pic) was squishy, wet underfoot.  The near-surface was well above field capacity for moisture.  My loafers were mucked some when walking over the field.   The field (middle pic) was firm, indicating water moved down into the profile leaving the near-surface soil near field capacity for moisture.  Along with the surface armor, there was no danger of mucking up my loafers anywhere in the field.  I could have driven my F150 over this field.    

     The pic to the left (bottom) shows a part of the same fied that has a long history of conventional tillage.  Shown is winter wheat stubble that is cut very short.  This field is likely to be chem fallowed in 2021 and seeded to winter wheat in the fall of 2021.  This stubble area is soft and mucky on the top 2" and frozen below 2", making it difficult to walk.  The recent 0.29" of moisture (snow/rain) that helped thaw the surface is held in that top 2".  I was able to compare this condition with a field on it's border with tall standing stubble that has a long history of low disturbance direct-seeding.  That field was thawed and firm underfoot indicating that the 0.29" of moisture (snow/rain) had moved deep into the soil profile leaving the surface firm and near field capacity for moisture.

     These field areas are close together and likely received the same weather, so what is making the difference in field conditions?   Two possibilities come to mind.

    1) there is no question that the soil structure is improved providing more porosity (lower bulk density) in the long term direct-seeded field compared to the long term conventionally tilled field.  The slake test would easily prove that; however, in winter, with freezing or frozen conditions, soil structure with more porosity isn't the full answer.  

    2) There has to be a temperature factor involved.  How does this factor in?  Well, --there is 34 years where our direct-seeded fields have reduced or eliminated erosion compared to conventionally tilled fields.   That's nearly a 1/3 of the time since native grass was removed from the landscape.  That time has to have an impact on soil organic matter loss (SOM).  Add to that, the time that SOM may have been building since 2010 with the introduction of our ultra-low disturbance no-till system, which includes the stripper-header, expanding our rotation to add more crop diversity, and beginning the introduction of cover crops.   My bet is that we have been able to improve our "soils health" to the point that we are getting more biological activity.  More biological activity results in more heat which in turn warms the ground resulting in faster frost melt, and along with increased porosity, allows moisture to enter deep into the soil profile drying down the surface soil to field capacity.

    I have yet to followup by doing some simple tests, and I have missed the timing for the temperature component of my theory.  My HOBO's should have been in the ground last fall and left until now.  There are several simple physical in-field tests that can be done now that indicates a comparison of bulk density and soil porosity.  I hope to get them done this spring/summer.