Agraria Journal Winter 2021

PETER BANE Chicken tractor using alley pastures and fertilizing tree rows to improve soil AGRARIA JOURNAL 2021 23 ferrocement tanks, ranging from 1,500 to 20,000 gallons, are the best solution for large tanks. Art Ludwig’s Water Storage provides a basic guide (Oasis Publications, Sta. Barbara, CA). Always place large tanks in a location where their thermal mass, screening, and windbreak functions can benefit adjacent plants, animals, or structures. ENRICH THE SOIL I have mentioned three forms of water storage: tanks, ponds, and soil, in the order of the quality of water they hold. Of these, soil is the greatest and the cheapest storage. Soil’s capacity to store water is a direct function of its organic matter content. If your soil organic matter (SOM) averages 2.5%, you have very little resilience to flood or drought, but if it is 7-8%, you can handle most rain or drought events, even in a disturbed climate. Importantly, SOM can only be increased with water because it accumulates from the growth and death of plant roots and decomposition by microbes, both of which depend on soil moisture. It is urgent, therefore, to begin building SOM when your climate still has available moisture, whether this is seasonally or over the long term. Compost and cover crops can build SOM, as can manuring, intensive rotational grazing by livestock, and chop-and-drop or coppice management of trees and shrubs. These processes contribute to soil climaxes, or the growing, death, and decomposition of organic matter above and below the ground. Indispensable to success is keeping the soil covered at all times. Tillage, which introduces oxygen to the soil, is the enemy of SOM, causing it to oxidize or burn up, returning carbon to the atmosphere. A limited exception to the need for moisture and cropping to build water-holding capacity is, ironically, the use of fire to create biochar. This is charcoal derived from plant residues which are heated in the absence of oxygen, a process called pyrolysis. Biochar is a special form of carbon, riddled with microscopic pores because charring preserves the original cell structure of the plant material. These pores hold water, microbes, and nutrient at least as well as humus or other forms of SOM, but biochar is durable over centuries as microbes cannot easily break its chemical bonds. FARMING A COLD, WET DESERT BY THE LAKE I farm in western lower Michigan on soils of nearly pure sand. Though we have minimally adequate rainfall, moisture is erratic in summer with large, infrequent downpours which drain away rapidly, punctuated by light rains that do little to wet the soil. For our farm, SOM is a matter of life or death. The only way to grow crop plants in this climate and soil regime is to hold water in the surface layers of soil where most annual and small plant roots proliferate. To do this, we need mulch from woodchip or straw. Together with poultry on range, our trees are the main source of fertility. They can send roots down to the shallow water table, and thus endure the swings of surface moisture. The deep roots of prairie plants can also access this ground water, but garden vegetables and annual crops cannot. They need irrigation. SISKIYOU PERMACULTURE By limiting the oxygen that reaches the fuel, a biochar kiln prevents most of the carbon from turning to gas and ash, leaving a valuable soil amendment that holds water and nutrient when added to soil. "Two broad strategies must become part of every farmer's toolkit: trees and water catchment."