What We’ve Learned From Compost
by Stephen Scott of Chino, AZ
Having been gardening for 15 years and composting for almost as long, we quickly realized that with our climate and native soils, improving the soil’s health and quality were one of the most important things we could do to help our garden. We are located in North-central Arizona, which is a semi-arid high grassland environment. Historically there would be 18 – 20 inches of moisture per year, but we have been lucky to see 10 – 12 inches in a good year over the past 20 years. There is almost always a south-westerly breeze which pulls moisture from any unprotected ground. The soils are really varied in structure with many different types in close proximity to each other. It is not uncommon to have a good productive soil with a caliche or high sandy soil within 20 – 50 feet. Our garden is a good sandy loam, with decomposed granite about 30 feet to the east and a heavy clay caliche soil 20 feet to the west.
Good, aged compost has helped us build the health and fertility of our soil and overcome many of the challenges we face in our garden. It improves the soil structure, brings the micro nutrients and biological life to the soil, along with earthworms and larger soil dwellers. Mulching the compost helps to retain needed moisture and brings the soil moisture level from about 2 inches down to the surface of the soil/mulch interface. We use a combination of straw and wood chips for our mulch.
There is much we have learned that we have applied to our approach in creating great compost, along with observations and education we have sought out along the way. We are happy to share some of our experiences and knowledge about compost.
We don’t turn our compost, partly from being busy and not wanting to invest in machinery or equipment, also partly from research, reading and talking with those who have learned how to create some incredibly rich, earthy compost that looks like highly fertile soil. Most compost tumblers are too small for our needs and a tractor or turning equipment is an expensive purchase for the occasional use.
Our compost piles will age for at least a year before being added to the garden. We have learned that the slow aging is more beneficial to the decomposition process as well as not losing nearly as much nitrogen to off-gassing as happens with the hot and fast methods. Another benefit is the decomposition is much more thorough, destroying weed seeds, pathogens and any unwanted chemicals much better in a slower composting setup. In our climate, we need to water our compost occasionally to keep it going. This is easy to gauge, as the rich earthy smell goes away when the moisture level drops. We water about every 2 weeks on average during warmer weather.
In our research and education of how to make great compost, we consistently saw traditional, proven methods from different countries, climates and approaches that worked. Many of them were very similar, adjusted to adapt to the particular environments of where they were used. The French intensive method used 3 feet of fresh horse manure and straw to heat the cold frames over the winter in Paris, then were pulled out and added to the compost piles to finish decomposing. In the fall the aged compost was added back to the growing beds for the upcoming winter. The Russian dacha gardening tradition shows how continuous composting and mulching with wood chips will improve the soil, overcoming both heavy winters in the north and drought conditions in the south.
Another thing that we found is that European traditions and older American traditions applied compost thickly, about 3 – 4 inches at a minimum, while modern gardening applies it rather thinly – like expensive imported marmalade on toast – and then wonder why they don’t get the results they expect.
After the year of aging and decomposing, our compost looks and smells like rich dark soil. This is especially pleasing to see in comparison to our pale tan native soils! Once we apply it to the garden beds, we mulch it with several inches of straw, watered well to keep it in place. Recently we have begun experimenting with wood chips as mulch, with good results. The wood chips help retain and gain moisture better than the straw, with the added benefit of attracting earthworms faster. The wood chips act like a layer of permeable insulation, attracting the cooler and moist early morning air that sheds its water when it meets the warmer temperature of the soil. This moisture travels into the soil and is retained. It is surprising to see and feel how moist the soil is under 2 – 3 inches of wood chip mulch when there has been no rainfall or drip irrigation at all!