Monday, August 30, 2010
Soils and testing for Microbes
It's late summer now and soils are becoming depleted and turning rock hard. Some of the depletion is due to low organic matter. I make the analogy to the fridge. You can keep taking food (ie organic matter) out until it is all gone and then you can take leftovers (ie compost) out but finally if you don't refill it the fridge will be empty.
It is the same with the soil. You need to add a lot of organic matter over time to sustain the soil in a garden, especially in a vegetable garden where you are removing so many minerals in the form of food you are eating. Given the right conditions microbes can multiply and grow and this eventually supplies the soil with nitrogen but microbes can't replace all of the micronutrients that have been removed with the food. Protozoa eating bacteria release nitrogen in plant available form and fungus transport phosphorus from afar but what do you do if your microbes themselves have been killed by fertilizers and mistreatment?
I bore you with all this because it is common that gardeners forget to replenish their soil and last week I took a soil biology course to see what is in my soils and compost and compost tea. I was generally happy - especially with the compost. It was alive with all kinds of beneficial organisms. If your soil is getting hard it is probably lacking the microbes necessary for good soil life. Fall is the perfect time to build soil microbes.
Thanks to Martin for the photo included here that he took when I was hard at work last week.