Ask any organic gardener, farmer, rancher, habitat restorationist, ecologist, agronomist, or organic landscaper – microbes are important.  (See Spring 2010 issue of EDIBLE AUSTIN for more.)  Microbes take a whole corner of the foundational soil triangle:  Microbes – Organic Content (Humus) – Soil Structure.  Beyond that, lack of research lends to a variety of opinions and approaches on the “right way” to support microbial communities in Central Texas soils.  So to take the least fanatical stance, I follow a simple path.

First, build organic matter in soil.   Most folks agree that soils need to have at least 3% organic content to sustain a balanced microbial population, but no higher than 10-15%.  Most disturbed soils in Austin have about 1% organic content.  We rely on soil tests to determine actual organic content for a specific landscape, and slowly apply compost (by topdressing) to get above 3%.  Not all composts are created equal, and different products present trade-offs among price, safety, microbial diversity and viability, and amount of humus, which is the end product of a completely finished product.  Everyone has their own opinion on the best compost, so I try to lay out the options, pros, and cons, and let the end user decide which is best for them.

Second, we consider the soil structure.  Ideal soil is porous, has a nice balance of drainage and water-holding capacity, and has a balanced set of nutrients in a form that makes it easy for plants to absorb them.  Most disturbed soils in Austin are compacted, have higher than ideal clay or rock content, and have nutrient imbalances.  Adding finished compost to soils introduces humus, which binds to clay particles to create crumbles and helps release nutrients that were otherwise tied up in the sticky clays.  In some cases, aeration combined with a compost application is a good first step in improving soil structure.  Proper mowing, irrigation, organic fertilizer application, and thoughtful use of the landscape all help avoid compaction and other soil structure issues.  A soil test can help create a customized soil amendment program, though topdressing with compost 1-2 times per year is usually not a bad general approach.

Then, once organic material is built up to at least 3%, and soil structure and nutrient balances are addressed, we can start building microbes.  The best way to do this is through compost teas.  Compost teas have exceptionally high concentrations of microbes, are relatively inexpensive, and easy to apply.  Most of our tea is purchased by an Austin-based company called Microbial Earth, though Natural Gardener and GeoGrowers also provide teas.

Because compost teas are basically little critter soups, timing is critical.  Although it doesn’t hurt to apply teas in winter and summer, the microbes will be mostly dormant during Austin weather extremes, so spring and fall are ideal application times.  Now is an ideal time to kick off a new season of compost tea applications.

Retail price for a gallon of tea is about $5-8, which can be applied using a simple 1- or 2-gallon pump sprayer.  1 gallon of tea covers about 5,000 square feet, slightly larger than the typical Austin yard.  You might consider a “drench” in early spring and again in late fall, which calls for 3-5 gallons of tea at a time, then follow up with a regular 1-gallon application every month through fall.  Our rates to apply the tea for you is about $35-40, in addition to the cost of the tea.