The importance of planetary “skin care” for our soils
February 28, 2013
Soil is often called the “living skin” of planet Earth; an essential but fragile part of the biosphere. Attention to soil health (or soil quality) has waxed and waned over the years, but it appears to be making a comeback. In the past few months I have been to two exceptional meetings on soil health – one in Moses Lake (>200 attendees) and one near Spokane (>100 attendees). Growers and crop consultants made up the largest share of the audience, mostly larger commercial growers. In my 25 years of working on soil quality, I have never experienced the level of excitement I saw and the depth of actual change on the case study farms presented. Ideas like the soil food web, that sometimes can be vague and hard to translate to action, were illustrated in actual practices on the ground that are improving the soil and profitability at the same time. Cover crops played a big role in the presentations. These appear to be underused here in Washington relative to some other parts of the country. To me, this spells opportunity.
The simple message from the meetings was that we need to restore the proper functioning of the soil. Soil quality has both an ecological dimension (what soils do in natural systems), and an anthropocentric dimension (what we expect soils to do for us). Typical functions are growing a crop, taking in and holding water, cycling nutrients, and storing carbon. We have tended to ignore the key role of soil biology in favor of chemical and physical aspects, but the biology is critical to restoring soil function. The speakers suggested four core principles for supporting the soil biology, and hence soil quality: minimize soil disturbance; maximize diversity of plants in rotation and with cover crops; keep living roots in soil as much of the year as possible; and keep the soil covered with plants/residues. These steps will create the most favorable habitat possible for the soil food web which in turn will function effectively and benefit us. These steps are understandable (more so than many soil tests we have looked at). We can easily measure our progress towards achieving them. And both the science and grower experience are validating them.
The cover crop innovations being presented were quite remarkable. Mixtures of eight or more species that combine different crop types (e.g. cool vs. warm season, grass vs. broadleaf, legume for N fixation, strong taproot for breaking up compaction, etc.) were the norm, fit into the crop rotation wherever possible to provide the living roots and soil cover. Several spreadsheet-based cover crop tools were shared that helped to make sense of the many choices and combinations possible. Both research data and farm photos illustrated what these mixtures look like and some of their effects. To keep this realistic for farmers, mixes that cost no more than $30 per acre were the goal. Even if the window for a cover crop mix was only a 4-6 week period, the speakers suggested that they would pay for themselves.
Given the goal to minimize soil disturbance, no-till type approaches featured prominently. But the point was made that no-till alone is not sufficient as it does not address the plant diversity that most systems lack. One speaker from North Dakota described the evolution of their crop system from the historic wheat-fallow (with its severe wind and water erosion) to continuous wheat with no-till, to integrating single cover crops, to more diverse crop rotations with multi-species cover crops. In their 15” annual precipitation zone, they now commonly grow 100 bushel per acre corn, unimaginable 20 years ago, with no soil erosion and greatly reduced inputs of fertilizer and pesticides. Grower costs per bushel of corn were shown to be lower than for the typical corn farmer on prime Iowa farmland. And integration of livestock grazing only improves things, both in terms of the soil and the economics. We have significant areas of eastern Washington with 15-20” of precipitation. What might we achieve here? Yes, our precipitation pattern is different as well as the landscape, challenging us to get creative.
We have researched and promoted soil quality for many years in Washington and have made important strides in reducing soil erosion, an obvious imperative for improving soil quality – stop the degradation. What else can we be doing to accelerate the restorative process? The examples presented at the recent workshops are worth considering. Cover crops look like a powerful tool to take more seriously for this job. Let’s learn from others, increase adaptive testing here in our diverse and unique environments, share our findings, and make soil quality happen. As growers recognize the importance of soil health for their livelihood and their legacy, and research and experience provide new ideas and tools, we may be able to improve our “global skin care” substantially.
To access a range of materials from the meetings, go to http://ext.wsu.edu/extras/irg/bsfbcconf.html and http://www.nrcs.usda.gov/wps/portal/nrcs/detail/id/home/?cid=NRCS144p2_046415 . The USDA Natural Resources Conservation Service is launching a new national Soil Quality Initiative in the near future.