Sunday, June 12, 2016

Char Your Lawn

Of the nutrients that pollute the Chesapeake Bay lately, phosphorus has been the worst. "Why, of course, with all those chicken factory farms on the eastern shore," might be one's reaction to this statement. In fact, the major phosphorus inputs are coming from tributaries on the western shore of the Chesapeake. The cause has not been identified, but it could well be leaching from residential yards. Maryland soils are generally high in phosphorus, so soil disturbances by developers could also play a role.

In 2012, Maryland passed a law that prohibits the use of phosphorus on lawns except for one-time applications in cases of repairing patches, establishing a new lawn, renovating an entire lawn, or if a soil test shows a deficiency. As the phosphorus gets used up over the years, lawns will then suffer, more soil testing will be needed, and more phosphorus. Biochar can help here. Along with its many other soil enhancing benefits, biochar is very good at adsorbing phosphorus and feeding it to plants, including turfgrass. Most biochars, e.g. those made from wood, also produce a temporary liming effect in the soil, raising high acid soils' pH to one more suitable for turf (6.0 to 6.8). By applying biochar to turf, you can avoid frequent repeat applications of phosphorus and help to reduce pollution of your watershed.
Photo by Mr Thinktank (CC BY 2.0)

The steps to take when renovating a lawn include dethatching with a thatch rake or machine, and then using an aerating machine to remove small plugs throughout. After aeration, apply fertilizer-charged biochar with particle sizes small enough to drop into the newly created holes. (If phosphorus is adequate per soil test results, fertilizing with biochar will still help preserve other nutrients added, as well as the extant soil phosphorus). Spray with water to wash the char into (but not off) the lawn, then seed and water again. The biochar will also help keep the lawn moist while the seed germinates. Check the pH semi-annually to see if lime is needed and don't mow it less than 3 inches.

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