Soil biology numbers change across seasonal cycles.  Understanding what mediates the flurries of activity of these wee beings is helpful in deciding when and how to check who is home in your soil.  Numbers peak when plants are actively growing and excreting “liquid sunshine” through their roots.  Soil temperature, moisture and other types of microbe food (organic matter) also play a role.

As perennial plants wake up in the spring and annual seeds germinate, photosynthesis kicks off a downward flow of sugary goodness – a delicious call-out to the beneficial microbes hanging around in the soil reservoir below (that is, we and the plant very much hope they are still there).  This flush of food and the microbes drawn to it lasts while the plant is growing.  As reproduction begins, nutrients instead flow upward into fruits and flowers and microbial populations around the roots drop. This is why spring is the perfect time for sampling, and why we sample from a standard place around root zones.  Sampling bare ground can provide a general starting point, perhaps quantifying the hit the biology just took from the tillage…

Summer sampling works if there is adequate soil moisture and cover, though we expect lower numbers.  Looking at the biology around the corn plants out at Hope Farm last September, we were able to measure a difference between the control plots and plants grown with chemical treatments + biologically complete compost (a 2.5-fold increase in the ratio of fungi to bacteria) and in plants grown with biologically complete compost without the chemicals (a 5.5-fold increase).  Yields increased by 14.6% and 75.1% respectively, showing the incredible difference those microbial partners made.

Fall moisture brings increased microbial activity again.  Annual plants and perennial leaves fall and become organic matter (food) for microbes.  Perennials draw any nutrients that are left back down into their roots and on the cycle goes.  Without year-round photosynthesising plants or adequate food, much of the biology will go dormant, awaiting signals for the right conditions to re-emerge.

So if you are curious about measuring the biology in your soil, spring is the best time to give me a buzz.  I invite you to bring in your samples and learn more about biologically complete compost in my CVRD Recreation workshop series beginning March 27th.  See www.springhillsoil-lab.ca for details.