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LAND SUCCESSION

 As land changes from desert to grassland to shrubs to young forest to old growth forests, different fungal to bacteria ratios (F:B) can be seen in each of them.  Bare soil devoid of plants normally contains all bacteria and no fungi.  On the other end of the spectrum, mature forests are more fungal dominant with F:B of 5:1 to 10:1 in deciduous forests and 10:1 to 100:1 in coniferous forests.

 

 FUNGAL:BACTERIA RATIO - WHY IS IT IMPORTANT?

Different plants thrive in soils with certain F:B ratios. Increasing the fungal biomass to achieve the targeted crop F:B ratio will lead to reduced weed pressure and improved yield and productivity of the plant.

Weeds, F:B = 0.1

Brassicas, F:B = 0.3

Vegetables, F:B = 0.75

Row crops, F:B = 1

Shrubs & bushes, F:B = 2 to 5

Deciduous trees, F:B = 5 to 10

Old growth forests, F:B = >10

 

HOW DO YOU DETERMINE YOUR F:B RATIO? 

A soil sample is taken and analyzed using a microscope and the number of bacteria are counted and the fungal biomass is estimated to determine the F:B ratio. This takes training and practice to become proficient.

 

THE SOIL FOOD WEB

The soil food web consists of plants and organic matter, bacteria and fungi as the basic decomposers, protozoa and fungal/bacterial feeding nematodes as predators, and higher level predators such as nematodes and arthropods. As the predators eat the lower level organisms, they release excess nutrients which causes "nutrient cycling" which provides nutrients to the plants.

A healthy food web will provide nutrients to the plants at the correct rate and time, retain nutrients, improve soil structure, suppress disease, and decompose toxins.

 

PROBLEMS...WEEDS, POOR YIELDS, HIGH GROWING COSTS, SOIL COMPACTION, SHALLOW ROOT DEPTH, NUTRIENTS LEACHING, ...AND ON AND ON...

You have weeds. So you spray herbicides to kill them. But you also killed most/all of the biology in your soil. Or you till the ground to kill the weeds which breaks up any fungi that were also there. Now you're missing one or more of the links in the soil food web chain. Congratulations, you are now farming dirt, not soil. Most likely the only microbes you have left in any considerable numbers are bacteria. You will have to add fertilizers to get a response and better yields from your crop.

 

HOW DO I GET THE BIOLOGY BACK?

If you stop spraying and tilling, it will come back naturally, but it may take many years. But we are an impatient society - we want it back now! This is not an easy question to answer and there is no answer that works 100% of the time because each problem has its own unique challenges.

You need to get ahead of the weeds - try planting cover crops to shade out the weeds to make it difficult for them to survive. Then you want to apply a good quality compost and/or vermicompost that contains the biology that you are missing. If the compost you are using contains mostly bacteria and lacks fungi and predator organisms, then you are not making a big step forward. Whatever organic matter you are adding should contain the organisms you are missing. The only way to tell is to look at a sample under a microscope or have a lab analysis done that looks at soil organisms.

Keep plants in the ground year round as much as possible. The exudates from the plant roots will feed the microbes. It will take time for the micro-organisms to multiply. If you are planting a crop in the spring, then spreading biologically complete compost in the fall will give them several months to multiply versus spreading compost a few weeks ahead of spring planting.

 

WHY USE COMPOST TEAS OR EXTRACTS INSTEAD OF ACTUAL COMPOST OR VERMICOMPOST? 

It comes down to cost. There are millions of microbes in 1 teaspoon of compost. The goal is to get these microbes back into the ground and/or on the foliage.  Depending on the quality of the compost, you may need 1 or 2 tons per acre to see an effect. But that amount is mainly because it can be difficult to spread a very thin amount over a large area without a precision manure spreader or top dresser.  With a quality compost, you may only need to extract 30 or 50 lbs if spraying over the same acre.  So for small gardens and beds, spreading the physical compost is probably easier, but for larger areas, spraying is usually more economical.

Applying the biology is different than spreading fertilizers which require a certain number of pounds per acre. With a lack of biology in the soil, the chemicals are needed to see a plant response. They will be used by the plants and/or could be leached away without something to hold onto them.  But when applying the microbes, we are inoculating the soil with living organisms that should reproduce and increase their numbers. The microbes, especially the fungi, will help hold onto the elements and supply them to the plants in the amount the plant requires and at the right time the plant needs them.

 

COMPOST TEA VS COMPOST EXTRACT: WHAT'S THE DIFFERENCE?

In general, a compost tea is made by suspending a mesh bag of compost in a tank of water and using an air pump to aerate the water. Foods are added to the water to encourage rapid reproduction and multiplication of certain microbes such as bacteria and fungi. Some examples of foods are unsulphured molasses to increase bacteria numbers. Kelp, humic acid, and fish hydrolysate are used to increase fungi. Brewing time can vary based on ambient temperature but is typically in the 24-48 hours timeframe. The tea should be used immediately as once aeration is stopped, the dissolved oxygen can be used up quickly depending on the number of microbes present leading to anaerobic conditions which normally produce unwanted organisms.

Compost extract on the other hand is similar to compost tea except that foods are not added. The goal is not to increase the microbe population but rather to transfer them from the compost to the water solution to be applied by spraying. Because there is no brewing time required, extracts can be made much quicker than teas.  Also they tend to last longer than teas as there are fewer organisms which will consume the dissolved oxygen at a slower rate.  The extract should be used immediately but could remain aerobic for several days depending on temperature and the amount/quality of the compost used which will directly correlate to the amount of microbial life that is present in the extract.

For both compost teas and extracts, a shadowing microscope should be used to check the number and type of organisms present to ensure that it remains aerobic. This will allow you to quantify the quality of the mixture.  

Compost teas are typically used for foliar applications as the microbes tend to stick to the foliage better.  Compost extracts are usually applied as soil drenches with the goal of getting them below ground where they can reproduce and interact with plant roots.