Water, Water, by David Libbenga
It’s the first week of May and, in our part of Southern Ontario, it looks like we might be growing rice this year along with watercress. But, hearken back to last year. Last summer, for most of us, was the driest since at least 2012. Many were obliged to put in irrigation systems and run them all season to try and maintain yields.
Besides the immediate effect on yields, does dry weather effect soil fertility in the longer term? The existence of deserts would seem to suggest that low rainfall does indeed mean the end of fertility. On the other hand, there are those who say that all deserts on this planet are man-made.
In the arid Sahel region of Africa, we find a possible answer to this question. Yacouba Sawadogo could be said to be the North African counterpart of Jean Giono’s “The Man Who Planted Trees”.
Yacouba has almost single handedly revived an ancient farming technique called Zai, which uses shallow basins dug in the soil to catch rainwater and prevent runoff. Yacouba’s innovation was to add manure or compost to increase water retention and fertility. A thriving 50-acre forest was the result of his pioneering efforts. Yacouba’s ongoing campaign to teach Zai to his fellow Africans is said to be more beneficial to the region than the combined relief efforts of international agencies.
Closer to home, the insight of landscape designer Mathis Natvik explains the high fertility of Carolinian forest land. Centuries of trees growing up, dying and falling over create a microtopography of basins and mounds. The land occupied by a mature forest is dimpled like the surface of a giant golf ball, and it soaks up rainfall like a sponge. In his reforestation projects, Natvik uses an excavator to recreate these basins and mounds before planting any trees. The resulting water retention allows for a diverse and rapidly growing forest.
Of course, the natural topography of the forests was lost when the land was turned over to agriculture. Is it possible for cultivated land to retain high fertility in an environment of less frequent but heavier rainfall events? That was the question which occupied Australian P.A. Yeomans. The book Water for Every Farm gives us his “Keyline Plan” for harvesting and retaining rainwater. First hand accounts from Hugh Williams tell of Yeoman’s farm being lush and green when surrounding lands were brown and scorched.
The foundation of Keyline is the use of off-contour cuts in the soil, which allow rainwater and air to penetrate lower levels of the soil. On rolling terrain, these cuts can direct water from upper parts of valleys onto ridges, using gravity. The plan can be scaled up or down to fit any farm and can incorporate swales, creeks and reservoirs as needed. Keyline concepts are widely used in permaculture also.
As biodynamic practitioners, we have other tools we can use as well. Peter Proctor writes in Grasp the Nettle about comparative water infiltration tests carried out in New Zealand on biodynamic and conventional soils. Water soaked into biodynamic soil two to four times faster than it did on conventionally farmed land. (See also Hugh Lovel’s article in the July 2016 newsletter.)
The common feature of these natural and man-made systems is that they slow the transit of rainwater across a given piece of land. They also maintain a more even distribution of rainwater in the soil, so that runoff which otherwise might result in some areas remaining too wet, is reduced. Consistent moisture levels in soil support the activity of mycorrhizal fungi, which promote plant growth and good soil structure — i.e. fertility. While many of us, myself included, store irrigation water in tanks or cisterns; in natural systems and traditional practises, water is stored in the soil, where it is then benefits soil microbiology and sustains fertility.