How Long Does it Take for Compost to Be 'Orchard Ready'?
Thank you for the great responses to my first article in "Christophe’s Compost Corner".
As I mentioned in my last blog post, at Frog Hollow Farm, we measure the temperatures of our compost piles every week. At any point in time time at the farm, we have about 8 piles of compost, in various stages of their life cycles (they were constructed at different times), which are being monitored for temperature, moisture and presence of various beneficial and important microorganisms (biology).
The compost that is made in our compost piles (windrows) has to be applied to the orchard soil as soon as it is ready (cured-mature) because we have to make sure that the whole orchard receives compost before the growing season starts and because we don’t have enough land area to store the finished product over long periods of time. Also, we constantly receive fruit, woody materials and other residues (waste) and new piles have to be constructed so that the residues do not pile up and create odor problems.
The piles are turned and watered frequently in order to maintain uniform temperatures and moisture throughout the pile for the microorganisms that produce compost.
In theory, compost can be made in 15 days and applied to the orchard if it reaches a temperature of 130F or more and is turned five times in this 15-day period. This protocol meets the standards of CCOF (California Certified Organic Farmers). At Frog Hollow Farm, our temperatures are higher and cycles are longer and consequently composting times are longer. However, we do meet the standards of CCOF.
Let’s look at one of the piles that we measured Jan. 15, 2014.
The name of the pile is S-33 (we constructed about 33 piles in 2014).
This pile was started Jan. 7, 2014. On that day, its construction was finished (all the materials were added) and it was turned with a windrow turner and watered. Turning is the equivalent of mixing a pile in your garden with a shovel. However, in our case, we use a mechanical turner that gently lifts and inverts the entire windrow bringing materials from the outside to the inside and bottom to top. At the same time, the turner waters various parts of the turning pile efficiently.
We have been checking the temperature of this pile every few days and it went up from about 100F to an average of 157F as of today (Jan. 14, 2014). We want to make sure that all areas of the pile reach temperatures of 130 F (or more) so that most weed seeds, plant and human pathogenic organisms are killed. The decision was made to turn S-33 today. No water was added because a moisture test showed that water content was adequate. Temperatures of the other 7 piles were also taken and decisions were made as to turning cycles.
So what exactly happens in the piles during the temperature changes that we are recording? Microorganisms that are active at cooler temperatures (50-100 F) start the initial phase of decomposition and create an environment suited for secondary organisms that can function at higher temperatures (120-150 F). High temperatures support degradation of tough materials like wood and elimination of weed seeds, plant and human pathogens. Once all the degradable “food” becomes exhausted, the pile dissipates more heat than it produces and when that happens, the temperature of the pile drops and it can be applied in the orchard.
- Christophe Kreis