Drought-Proofing Your Farm, part 2
Dec 1 2012
After a Friday evening “teaser” lecture by Darren Doherty of HeenanDoherty land planning and farm design, Saturday morning started the official drought-proofing program. Doherty talked about RegenAG, a series of formal courses that will be introduced in the US next year. The goal of all the regenerative agriculture experts, in Darren’s words, is to “move permaculture…to being an unconscious practice.” Participants will be exposed to the principles and methods of regenerative agriculture, and will be equipped with the knowledge to be able to discuss the practices effectively. Some of the courses include basic Regenerative Agriculture, Holistic Management Grazing and Farming, Fertility Farms (based off Eugenio Gras’ work), and Polyfaces in Practice (based off Joel Salatin’s work).
Then he dug into the real dirty work. Fairly literally, in fact. The talk centered on soil and sequestering carbon. Why so much focus on soil? And what does that have to do with drought-proofing a farm? Essentially, soil carbon = soil water. The more carbon in a soil, the more water it can hold. For every unit increase of soil carbon, soil water-holding capacity increases by eight units. A hectare (roughly 2.5 acres) of soil with 4% carbon can store a half of an Olympic-sized swimming pool worth of water. How many Iowa farmers would have paid for that much water this past summer? Doherty said that the lack of water or rainfall is not often the problem during a drought – it’s the fact that most soils can’t hold what water is given to them, to last the plants through a time of stress. So – how to achieve that?
“Pasture is the fastest healer of land,” he affirmed. Physiologically, grasses are easily able to transport sugars and nutrients up and down from the soil. Trees, meanwhile, primarily cycle nutrients through falling leaves, and grow relatively fewer and smaller roots than do grasses. Clipping a grass plant’s leaves triggers die-off of the roots, which decompose and contribute to soil carbon. If that clipping is done by a grazing animal, then nutrients will be returned to the pasture as well through manure and urine. These nutrients, combined with adequate recovery time, allow the forage plant to regrow. It can then be grazed again, and the roots and animal waste turned into even more soil organic matter.
Evaluating a pasture involves looking at a number of soil and forage parameters. The amount of bare ground and erosion (including ‘pedestaling,’ where plant crown roots are above the soil level because the soil has been washed away), the amount and distribution and incorporation of litter and dung, the desirability and age and diversity of plants, the living organisms in and under the soil, and the plant canopy and vigor and distribution. Inspecting a pasture and noting whether or not these attributes are satisfactory is a good way to identify major challenges to healthy soil in that pasture.
Pasture observations, particularly of present forages, give insight into the pasture condition. Rhizomatous grasses, which spread horizontally rather than send down deep roots, indicate that there’s a hard compaction layer the roots can’t get through. Thistles indicate soils with high cation exchange capacity, which tend to track and often used to be very fertile. The thistles, which have deep taproots, are able to mine for nutrients that have leached downward, and which other pasture grasses can’t reach.
The afternoon session focused on keyline design, which utilizes the natural landscape to collect and control water, and to plan out the entire farm. “Slow it, sink it, spread it” was the mantra. The first step in determining farm layout is to identify the main hills and valleys and to locate their key points. The keypoint in a valley is just below where the slope switches from being concave to convex. Essentially, it’s where water and material flowing down the hill (falling away from the convex part on top) starts to settle (just after the angle changes to be concave). The contour line running horizontally from that point is the keyline. The keypoint and keyline of each valley are used to plan water collection – keypoints are where runoff from hills will congregate, making it an ideal location for a dam or holding pond. Roads built along the keyline will also help channel water to that holding pond; trees are often planted there as well to cement the soil. In addition, to help in slowing, sinking, and spreading water, a keyline plow (similar to a subsoiler) can be used along the keyline. Water running down the hill will be slowed by the disturbed soil and distributed out to either side of the ridge, rather than continuing to run off the landscape or into a creek. Retained water on the hillsides promotes forage growth, which binds soil in place and contributes more organic matter, making the soil deeper and richer. Over time the plowing is unnecessary, as plants and their roots intercept most of the water flowing off of slopes.
In a nutshell, keyline design utilizes the landscape to do as much work as possible, and a farm enterprise is fit within the available resources. Darren outlined plans to supply water for houses just through their placement on the landscape, and recounted work done to clean and purify wastewater just by using plants and proper flow control. He covered the planning and orientation of roads, fences, and bands of trees.
With the basics of keyline design under participants’ belts (or feet, since it’s the soil?) on Saturday, the group looked forward to Sunday’s in-field demonstrations.