Soil Vitality

“Middle Earth” (New Zealand) soils may show unusual vitality with high soil microbial activity. A 5 hour Solvita test releases CO2 rapidly (inset graph). Field shots where Solvita tests were conducted on pastures gave Soil Health Scores >15. Yet, soils are beset with high Aluminum locking up Phosphate.

Imagine an ideal soil climate, little or no soil tillage, and rotational animal grazing: what’s the soil health of that system? We ran Solvita on soils from the North Island of New Zealand (near where the epic fantasy film The Hobbit was shot) and saw some unusual results: “the Solvita test seems to be all done after only a few hours” NZ consultant Horatio Payne reported.  On close examination, the respiration (and soluble carbon and SLAN) were also unusually high. The sheep paddock soils gave off as much CO2 in 5 or 6 hours as most soils on USA farms do after 24 hrs.

Further lab work showed the microbes to be respiring at over 200 ppm/day – almost twice what Solvita measures on normal soils (infrared pulse analysis was used to confirm this).  These soils are “fast risers”- a term Dr. Rick Haney (USDA-ARS) uses to describe unusually vibrant Solvita response. Brinton’s theory: the liveliness is associated with pastures and animal grazing systems.

Our lab has not often observed soil activity this high. However, samples arrived recently from a 250-acre organic farm in NE Pennsylvania: the respiration fell on the same curve with our New Zealand soils: fast risers, with sufficient CO2 in the first few hours to turn Solvita yellow. In this case the clue was: long-term pastures, flax-undersown with clover, small grains and cover crops. Such soils have large natural nutrient cycles and excellent nitrogen mineralization potential.

The challenge with very active soils is leading to a new Solvita application: a 5 hour test. If fast risers are involved and the color changes rapidly, Solvita is read at the 5 hr mark and the result multiplied by 2.5 (according to regression equations) to get the equivalent 24 hr value. “Similarities between soils like this from two differing regions of the world suggests this is not just a ‘Middle Earth’ phenomena, but associated with high-functioning systems with plenty of OM and microbial rates” says Brinton.

Soil health is more than respiration and includes evaluating nutrient cycles with methods appropriate to plant systems: The nutrient portion of the Soil Health test provided a clue to what is holding these NZ soils back: high levels of active aluminum which act to tie up P. “That fits” says Horatio Payne: “There’s a saying in New Zealand: the farms are built on superphosphate and lime”.