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What’s the difference between compost and peat moss?

Compost is manufactured from recycled materials derived from plants and animals.  Peat moss forms naturally over many, many years – also from decaying plants and animals.  Both are rich in organic matter.  But it takes so many years for nature to form peat moss that the product is not considered “sustainable.”  Peat also tends to be too expensive to be used in large projects.  Fortunately, compost can be substituted 1:1 for peat in any media mix or soil recipe.  

Section 2(d) of Executive Order 13514 establishes a 20 percent water reduction goal for federal agencies by fiscal year (FY) 2020 relative to baseline use (FY2010).

A reported 87 percent of all water consumed in the U.S. is utilized for irrigation, with “consumed” meaning no longer available for other purposes. An estimated 80 percent of consumptive use is by agriculture, as much as 90 percent in the western states.

Whether at home, in the landscape or on-farm, more efficient irrigation systems, moisture monitoring and other best management practices (BMPs) for water management are certainly important conservation tools. But compost use has been proven to reduce water consumption by 30 to 50 percent, because as organic matter (OM) content of soil goes up, water use goes down.  Optimum recommended OM content is 5 percent.

Compost is 40-50 percent organic matter and a better choice than either raw manure or peat moss to replenish and maintain OM at ideal levels.

For the typical 5,000 sq. ft. lawn, bringing soil OM content up 5 percent saves about 9,400 gallons of water a year. In the U.S., a national policy supporting a 5 percent increase in organic matter content just for single family detached homes (91+ million) would save about 855 billion gallons a year.

That’s the approximate volume the Mississippi River dumps into the Gulf of Mexico every three days and would be enough to water all the golf courses in Florida for the next four or five years or provide water for the City of Raleigh, NC, for the next 50.

There are more than 61.1 million irrigated acres in the U.S. – about six times the surface area of all suburban lawns. Six times 855 billion gallons saved is more than 5 trillon gallons every year.

If everyone (federal government included) with an irrigation system would raise the organic matter content of those irrigated landscapes and cropland to 5 percent and keep it there, the impact on water use would be staggering.

The simultaneous impact on stormwater runoff is also an eye-opener, but we’ll save those mind-boggling numbers for another day.

Resources for this post: consumptive water useU.S. irrigated acreage