Welcome to Part 2 of the blog related to the importance of maintaining healthy soil at the Willits Energy Farm. If you followed the first blog, you will know that we will eventually need to do something about compost at the site. The soil is healthy and can sustain the crops that are being grown in it; however, to grow so intensively without the addition of compost is unsustainable. I felt that the addition compost would take the pressure off the land while we continued to work to establish the crops and the desired composting system. I consulted with David Drell and Jason Bradford and we thought that it might be a good idea, in this first year, to possibly import some compost if the source is not too far away. The plan to import soil is defiantly not how we want the site to operate in the long-term, yet, the health of the soil is a first priority and this is a consideration that we cannot afford to overlook, even if it means importing some compost.

There are multiple people offering “compost for sale”, however, one needs to be careful about the quality of compost that you are buying. Some stuff that is touted as “compost” is no better than mulch, and the processes in which the organic material was created may not have been aerobic or hot enough to kill weed seeds (150°F). If the organic material was composted anaerobically, it will contain natural alcohols that can turn a plant to slime by dissolving portions of the cell walls. Finally, anaerobic compost will lack fungi and the compost will thus lack the diversity need for a healthy soil food web. If the material has the potential of causing harm instead of helping the situation we will not bring it to the site.

David and I decided to visit a farm site that as been know for creating quality compost and take samples to view under the microscope. By talking with the person who makes the compost and by looking at the types of microbes inside it we can make a fairly good assessment of whether or not we want it on the site. When we arrived to the farm there were two different compost piles to choose from. One of the compost piles had been created using grape pomace from a nearby vineyard that had been mixed with straw bedding and spoiled hay. There were earthworms in that compost and also a great deal of little white bugs. Some of the bugs were spring tails and others were symphylums. These symphylums are particularly nasty if they do not have a good deal of fungal biomass to eat. If there is no fungi the symphylums will eat plant roots!

The other pile of compost was made in windrows that had not been turned for 8-9 months. It was composed of 70% horse manure, 25% made of goat droppings, and 5% chicken manure. It looked very nice and had an earthy smell, no visible bugs.

After getting the samples home I examined them under the microscope.

Grape Pomace Compost:

The grape pomace had a diversity of organisms. Lots of bacteria and large dark strands of fungal hyphae were present (large dark fungal strands are a good thing). Unfortunately, there seemed to be a large number of ciliates, which are protozoa that thrive in anaerobic conditions. I also noticed bacterial feeding nematodes (small round worms) that feed high on the soil food web. While the fungal strands looked promising, the presence of symphylums and springtails coupled with the knowledge that some of the material might have been fermented into natural alcohols made this compost into something that we did not want to bring to the site at Brookside Elementary.

Animal Manure Compost:

The animal manure compost was bacterially dominated and had beneficial protozoa in it. Beneficial protozoa include testate amoeba and flagellates. These protozoa are important because they eat the bacteria and help cycle the nitrogen contained in the bacteria into plant available forms. I noticed some large, dark fungal strands; however this compost did not have the fungal biomass that the grape pomace compost. I did not notice any nematodes. Out of the two compost samples, I felt that this one was the best.

Grape Pomace Compost

Grape Pomace Compost (Notice it is purple)

Manure-Based Compost

Example of a Bacterial Feeding Neamatode (The Spots Toward the Tail Are Bacteria)

Example of a Fungal Strand with a Red Spore

Example of Two Cilliates (Protazoa). They Are Feeding On Bacteria