Jun 29, 2020
In this episode of the Regenerative Agriculture Podcast, John interviews Dr. David Johnson, a New Mexico State University research scientist, Adjunct Professor for the College of Agriculture at Chico State, and Faculty Affiliate for the Center for Regenerative Agriculture. His research clearly outlines the importance of managing the ratio between fungal and bacterial populations in the soil for plant productivity and carbon sequestration. During his research on the salinity of manure compost, Dr. Johnson and his wife, Hui-Chun Su, developed the BEAM Soil Compost Bioreactor which develops compost with high fungal populations. John and Dr. Johnson discuss carbon cycling and the capacity of biology to sequester carbon and build soil organic matter. The conversation provides a fascinating look at the role of carbon dioxide in agriculture and the environment, how the ratio of fungal to bacterial populations in the soil are key to carbon cycling, and the methodology growers can employ to actively increase soil organic matter while decreasing costs.
Carbon Sequestration (00:02:00)
Dr. Johnson explains that high concentrations of
carbon dioxide are problematic due to the impact on the climate,
increasing the global temperature, rather than the impact of CO2 on
plants, which like high concentrations of carbon. Due to those
effects, carbon sequestration must be part of sustainable
agriculture. John mentions that he has seen organic matter gains in
the fields of half a percentage point per year, a very rapid
improvement. Dr. Johnson believes that rate is possible, but only
with cattle or other grazers in the system. In his experiments
based solely on biology, he sees a little over a quarter of a
percentage point per year increase in soil organic matter, or 10
tons of carbon per hectare.
The Microbial Community
(00:08:00)
In
order to realize these significant results in building soil organic
matter, Dr. Johnson says the microbial community must be balanced.
The microbes cycle carbon, improve carbon use efficiency, and
create a healthy soil system. Plowing and the use of biocides
destroy fungal populations, so those need to be restored in order
for soils to function appropriately. John references a slide in one
of Dr. Johnson’s presentations
comparing fungal to bacterial
biomass ratios and the partitioning of the photosynthates. The
explanation is based on an experiment with compost made in the BEAM
bioreactor, where fungal dominant soils were shown to utilize five
times the amount of carbon in the plants than bacterial dominant
soils. An average of 11% of carbon captured by a plant goes into
the root, shoot, or fruit of the plant in most agricultural systems
today, but in a fungal dominant soil, 55% of the captured carbon
can be partitioned into the plant rather than into the soil. This
can dramatically affect plant productivity and growth. Maximum
productivity and carbon capture happen when the fungal to bacterial
ratio is one to one, which also causes soil respiration to
decrease. There can be increased crop biomass as well as more
organic matter in the soil. Dr. Johnson notices that as fungal
populations in the soil are restored, farmers are often happier.
About 60% of a crop must be left to effectively rebuild the soil
even after the soil microbes are in balance, rather than 100%
removal.
Balanced Systems
(00:27:00)
Dr.
Johnson explains that having the right microbes is a necessary
first step towards building soil health, but is not the complete
solution. The compost his team uses as an inoculant has over 2,500
species of bacteria and over 400 species of fungi, archaea,
viruses, and more. That is a balanced community of varied microbes.
The energy flow and carbon flow is also critical, and the
photosynthetic rate must be increased. All of those work together
to make a much more efficient, restored system. When the soil
biology is in balance, the microbes can make the elemental
nutrients available for the plant. That takes out the human
guesswork of trying to figure out how much of each nutrient is
needed. In a corn trial, the amount of applied nitrogen was
decreased to 15%, or about 37 lb. per acre, and two lb. of compost
per acre were added. The result was a small decrease in
productivity in the first year and $80 more an acre in profits.
Although only 37 lb. of nitrogen per acre were applied, 261 units
of nitrogen were measured in the soil, compared to the control of
256 lb. of nitrogen. The nitrogen was made available from the soil
system rather than as a purchased input. Dr. Johnson believes that
healthy soil biology leads to a resilient system. He has seen
dramatic changes in water absorption and retention when cover crops
are used and soil biology is improved. In compacted soil, it took
10 minutes for an inch of water to infiltrate, and it now takes
only seconds for that same inch of water. The first 1% increase in
soil carbon is associated with a five times increase in the amount
of water the soil can hold. Agriculture currently uses 70 to 80% of
the freshwater on the planet, but utilizing these methods can
double crop productivity and save water.
Importance of Observation
(00:43:00)
Dr.
Johnson explains that the information he has discussed so far was
not the primary goal of his research. He was seeking a way to
compost dairy manure, and his research serendipitously led him to
this information. He believes that holding on to traditional
methodologies is an obstacle, and that the farming of the future
must be based on regular observation and be open to change. Farming
for 40 years provides 40 different experiences, so paying close
attention is the best way to improve. Resources he recommends
include Chico’s Center for Regenerative Agriculture, John Kempf’s
blog, Gabe Brown, Ray Archuleta, Allen Williams, and Will Harris.
His final thought for listeners is to look at soils as a living
organism, pay close attention to biology, utilize observation, and
to transition to a system of regenerative agriculture to rebuild
the soils. Dr. Johnson has seen that it’s possible to rebuild soils
and that it has the ability to make farming fun
again.
Resources: