Out of the Scientist’s Garden

If I was starting a career in agriculture over again, Australia is the place I would go to prepare for it.

Why?

One good reason is Richard Stirzaker, author of “Out of the Scientist’s Garden: A Story of Water and Food” (CSIRO Publishing, 2010, 193 pp.). Expert gardener, tinkerer, educator, raconteur and, Senior Research Fellow at the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Canberra, Australia, Stirzaker melds the rigor of scientific thinking with a profound understanding of scale and problem solving as it affects how we feed ourselves. Stirzaker invites us to ponder the meaning of hard-to-pin-down words like “sustainable” that have ambushed the lexicon of agricultural scientists and emissaries of development (now pivoting to “climate smart^®“). What exactly is the template for sustainable agriculture in a world expected to reach a human population of 9+ billion by 2050?

Today, irrigation accounts for more than 70% of groundwater diversions annually, and for more than 90% of total consumptive water use including surface water (FAO 2010; Siebert et al. 2010). As Stirzaker notes, there is plenty of water on planet Earth, but 97% is salt-laden ocean water. However, if we try irrigating with saltwater, plants will wilt and eventually die. Less than 3% of water is fresh enough for watering plants, and two-thirds of this is locked up in icy blocks. Worldwide, the sustainability of our food system is inextricably linked to the remaining 1% supply of freshwater. We can argue the merits of fertilizing with organic nutrients in compost over that of soluble inorganic fertilizer, i.e. the insufferable and counter-productive “natural” vs. “synthetic” debate. In all cases, the nutrients must be dissolved in water and available at the plant root; and, there must be enough water in the soil to sweep nutrients to the exchange sites on roots if we are to sustain, let alone increase, the food supply. The problem of soil water is the most urgent facing the global food system, and Stirzaker is acutely aware of this. Throughout, the author emphasizes the guiding soil-plant-water principles underpinning agricultural science with a minimum of jargon and, explains how intervention in the food system can flounder in spite of the soundness of an idea.

The book is divided into three parts. Each part has seven chapters in essay form, loosely turning on a theme. Part 1 “The View From Our Garden” traces Stirzaker’s professional roots back to the family garden during his growing years. He opens with this simple premise: “This is not a book about gardening. Yet the story of feeding the world begins in a garden”. It’s not easy to comprehend the unceasing, massive streams of global energy, water, and mega-kilos of fertilizer needed to feed the world. But the garden, Stirzaker contends, is a scale we can comprehend. As a food production system, the home garden is relatively simple. The consequences of crop failure are usually not catastrophic for the gardener. It’s easy to try new things (“innovate” in trendy lingo) without the fear of going hungry or losing one’s shirt. The garden is also an excellent place to learn how plants interact with their environment. Plants respond to temperature, frost, day length, humidity, and moisture in different ways. Once we understand, for example, how onion varieties respond to day length or cabbage and broccoli to temperature, we can take advantage of this knowledge to maximize the variety, quality, and supply of food produced from the garden. The commercial vegetable grower exploits the same knowledge, only on a larger scale.

Louis Bromfield (1896-1956), Ohio-born American novelist and pioneer of conservation farming in the 1940s. Bromfield’s recipe for restoring worn-out land emphasized deep-rooted legumes and grasses. Largely forgotten by the 1970s, the chronicles of Malabar Farm and Malabar-do-Brasil aroused my interest in food systems, soil, and conservation tillage.

Part 1 also delivers the mea culpa agricola “The Lapsed Organic Gardener”. Early on, Stirzaker was an avid reader of gardening books. A particularly influential favorite was “The Complete Book of Self-Sufficiency” by John Seymour. I never read Seymour’s epistle, but there were many books in this vein making rounds in the 1970s written with urban exiles and suburban back yard growers in mind. I, too, had teenage dirt hog idols, principal among them the works of Louis Bromfield set forth in books like “Pleasant Valley” (1943), “Malabar Farm” (1945), and “Out of the Earth” (1948). Bromfield’s literary star had long since faded by the 1970s and with it, his prolific writings, mainly surviving as obsolete, forgotten tomes moldering on the shelves of the public library where I first discovered them. Bromfield was never an advocate of organic agriculture, but he adapted organic concepts if they fit his operation. Early on, he abandoned the idea of the generalized self-sufficient farm, to specializing in livestock and dairy. The pattern of the specialist farm has intensified in the post-WW II era, with little hint of changing direction. This is one of the irresistible forces driving contemporary food systems, Stirzaker concedes. Eco-friendly gardening methods as described in books like Seymour’s are often ill-suited to commercial-scale production. Still, one idea from the Malabar Farm sagas that has stuck with me over the years is the potent but generally neglected influence of the subsoil. In spite of poor topsoil inherited from years of bad plowing, Bromfield was convinced that his glacial Ohio soils were fertile, advocating “farming from three to twenty-feet down”. There, locked away in the rich subterranean fabric are stocks of water, nutrients and trace minerals awaiting discovery by plant roots. His recipe for restoring worn-out land emphasized deep-rooted legumes like alfalfa. Stirzaker seems to have hit upon the same idea decades later, mixing shallow-rooted vegetable crops with strips of alfalfa (aka “lucerne” in Australia). In this system, the deep-rooted alfalfa picks up nutrients that filter past the vegetables and brings them back to the surface. Cuttings of alfalfa are then placed in the vegetable rows where they decompose, releasing the dodgy nutrients. The difference is, Bromfield’s approach worked commercially, whereas Stirzaker’s vegetable-alfalfa system did not.

This brings us to the subject of “agroecology”. Nowadays there is a great deal of buzz about agroecology, at least within academic circles. Agroecology emphasizes biological complexity like Stirzaker’s vegetable-alfalfa system. On a non-mechanized artisan level, mixed cropping systems may be successful but it is difficult to implement them on a commercial scale. Mechanization involves a degree of simplification. Under mechanization it is not practical to have many species coexisting on a plot of land. In reality, a sustainable food system has many interlocking facets that impart buoyancy to the whole. Foremost is creating a soil environment where roots are unhindered by compaction, pH and mineral salts, and water. This depends on human intervention in the food system, not biological complexity. Sustainable soil and water management should invoke a modus operandi that is adaptive, free of taboos provided it builds production, quality, and income following the precepts of sound land husbandry. The idea that there is one path leading to sustainability, as prescribed by the organic canon, biodynamics, net zero, clivus multrum, or what have you, is a conceit advanced mainly by those with little direct knowledge of modern agriculture or that do not comprehend the massive, interlocking infrastructure involved in feeding the world. Agriculture isn’t natural, and leaving things to nature ensures that a large part of what we produce will be intercepted by our competitors. This doesn’t mean, Stirzaker stresses, that better, more ecological solutions shouldn’t be sought after for sustaining the global food system. The task ahead is reducing agriculture’s ecological footprint as it becomes more productive, which it must. On the other hand, we must accept that there are constraints to how things get done in the world of commercial farming. As spectators, we’re not free to foist our cherished ideas upon farmers.

Part 2, “A Journey Through Soil” gets down to the business of soil water, water supply, and irrigation; why, as Stirzaker asserts, it is so difficult to know how much water there is in the soil and, why irrigation is often so inefficient or damaging to plants. Having been in the irrigation business myself, much of what Stirzaker says rings true. Chapter 10, “The Machingalana is Talking to Me” relates the author’s approach to solving a particularly thorny problem for the irrigator: measuring how much water is in the soil in a simple, straightforward way. Stirzaker’s answer is the FullStop wetting front detector, a simple mechanical device designed to detect the depth that water infiltrates in the soil. For now, I pass on the wetting front detector and related chapters because they deserve a separate blog which I shall postpone for later. Here I want to focus attention on chapter 8, “The Tale of Clever Clover”. The clover in this tale is subterranean clover (Trifolium subterraneum), or sub clover for short. Clovers are legume plants. This means that they have to ability to produce their own nitrogen fertilizer, literally out of “thin air” (Earth’s atmosphere consists of about 78% nitrogen). A soil-dwelling bacterium called Rhizobium colonizes the roots of legumes, forming small nodules where they live. The bacteria come equipped with special enzymes needed to convert atmospheric nitrogen, which plants can’t use, to ammonium nitrogen that plants can use for protein synthesis. The bacteria fix the nitrogen and pass it on to the clover plant. In exchange, the bacteria get energy in the form of sugars from the clover (clover still needs potash, phosphorus, and lime so it’s no free lunch). The name “clever” clover presumably derives from this clever act of nature, or so it appeared to the science journalist who interviewed Stirzaker. The tale begins with an extra garden bed Stirzaker had seeded with sub clover. After blooming the clover dies off naturally, leaving behind a nitrogen-rich organic mulch. Under the decaying mulch, Stirzaker finds transformed soil: soft, crumbly, aromatic. Eureka! At last, the Rosetta stone of no-tillage organic vegetable production is revealed, all from a humble clover plant growing in a tiny garden plot. What follows is an avalanche of media attention directed at the Clever Clover plots and the man behind their discovery. Clever Clover kits are quickly assembled and sell like hotcakes. It must have been a classic Watson and Crick light-bulb moment: Announcing you’ve just discovered DNA or something equally game-changing!

Small grain plots on the Thompson Farm, site of my Clever Clover epiphany. The green strip in middle is where we cut grain, now flush with weeds. Compare to the weed-free under-canopy (inset) photo taken in mid-June in the uncut plots (the greenish crust is moss growing on the soil surface). I thought we could duplicate this weed-free effect in full-season annual row crops with the cover crop roller, thus saving farmers the cost of spraying and reducing the ecological footprint of agriculture. It didn’t work out that way.

It was not to be. While Clever Clover was a big hit with home gardeners, it did not influence commercial vegetable production. As Stirzaker explains, innovations that solve one set of problems often create new problems, and scale matters. Planting systems designed for the garden may be eco-friendly innovations, but it is difficult to implement them on a commercial scale. New risks are introduced to the system, and farmers do not like taking risks with their livelihood. Problems like: What happens if the clover gets infested with weeds or slugs? (Cutworms, wireworms, and rootworms are the under-mulch nemesis in North America). How do you plant and irrigate through the mulch, and what happens to the mulch after harvest? All were unknowns, and the Clever Clover did not provide answers.

Cover crop roller machine. Cover cropping adds a layer of complexity to the food system. For example, if termination of cover crop growth isn’t timely, it can exhaust profile soil water, increasing the risk of drought stress for the principal summer cash crop. Richard Stirzaker urges that we understand the consequences of our interventions in the food system. Sustainability has many facets, and future events may change the way we interpret it.

The Clever Clover tale parallels a similar epiphany I had about a decade ago when I thought I had discovered something vitally important, only to find that it, too, didn’t prove up under testing. This tale involves rye, a grass, but could apply equally to legumes like sub clover. At the time I was involved with a project testing subsoil nitrogen recovery beneath small grain plots.  The above-ground plant biomass-grain, leaves, and stems, all were cut in April and May, except for the “check” plots (these are control plots in agricultural field experiments). The checks were left to grow and, as I had no reason to visit the field plots through mid-June, the rye and other small grains went to seed uncut. The rye, in particular, had grown very tall because we had planted corn on that land the previous year and some of the nitrogen fertilizer that was applied to the corn crop carried over to the rye. In my absence the uncut rye slumped over from the weight of its top-heavy mast (known as “lodging”), forming a perched canopy. Beneath this canopy, I detected no weed growth. In contrast, plots that had been cut clean were heavily infested with weeds. It is well known that rye releases toxic phytochemicals during decomposition that inhibit the germination of small seeds, a phenomenon known as allelopathy. What happens to those chemicals after the rye has been terminated is not well understood, but it is presumed they leach into the soil and are broken down by microorganisms. Eureka redux! Immediately the question arose: Could we duplicate this weed-free effect under annual row crops? Eventually, the mulch would decompose into a soft, spongy, organic mold, earthworms would improve aeration and recycle nutrients with their castings, the soil would be conserved, all in one nifty package. This was my Watson and Crick moment. I thought the conundrum of organic no-tillage was solved, and conventional no-tillers would benefit to boot. About that time, reports of mechanical roller-crimper tools began to circulate in the agricultural world. Brazilian farmers were using the roller-crimper to flatten standing cover crops, and prototypes soon appeared in North America. It wasn’t long before I got my hands on one of these tools. Field trials were initiated in soybean and cotton comparing high-density rye cover crop mulch with and without herbicide treatment. Turns out, as the herbicide application was reduced, weeds increased and soybean and cotton yields declined. The worst plots were the organic no-herbicide plots, some of which looked like triple-canopy jungle by the end of the season (summaries of this research are available here and here).

Fall cabbages planted in pearl millet (Pennisetum glaucum) mulch after flattening with the cover crop roller. Short-season crops like cabbage and broccoli were a better fit for no-till cover crop systems because the cooler days of fall curbed warm-season weeds, leaving winter annuals small enough to ignore.

What went wrong? We were not able to reproduce the weed-suppressing effect of the rye observed in the small grain plots. The physical barrier of the flattened rye residue coupled with leaching phytochemicals was not enough to thwart weeds in the cotton and soybean plots. Worse yet, many of the weeds that became established in the plots were noxious perennials like horseweed and pokeweed that would return next year ever larger, making planting more difficult. This was my Clever Clover escapade. It’s the reason I dwell at length on this particular chapter of the book. I understand just how Richard Stirzaker must have felt after realizing that it was all much more complicated; there’s no easy recipe for eco-friendly productive agriculture. At first, we pitched the idea of rolling cover crops to the commodity groups because we needed money to continue the research plots. There were no takers. Producers were well aware of the cover crop roller and made it clear that they had no interest in it. The project died, and we moved on. There are still a few cover crop rollers in operation in North Carolina. But overall, the cover crop roller has not influenced commercial row crop production in North Carolina for the same reasons that Clever Clover was unsuccessful.

The Clever Clover tale points up two enduring lessons as Richard Stirzaker tells it: (1) it is not easy to intervene in the food production system; and (2) there’s a big difference between having an impact and having an influence. “Impact” is something that rivets attention over a short span of time, i.e. the proverbial “flash in the pan” or “fifteen minutes of fame” syndrome all too common nowadays, especially for projects with short investment turnabouts. To have an influence takes a lot of persistent, painstaking work over a long time because it involves fundamental changes in the way people do things. When we tinker with agricultural systems, the full effect of our intervention is often obscured by short-term objectives. I suspected that there were establishment effects hindering the efficacy of the cover crop roller. Long-term plots would be needed to calibrate the system, including a transitional phase where the surficial weed seed bank could be exhausted through a combination of cover cropping and prescription herbicide treatment. This plan was never realized.

To Stirzaker’s list, I would add a third lesson: It is not easy to discover something new. Farmers have been tinkering with clover and cover cropping for ages. Few of these experiments have garnered the media attention of Clever Clover, but their stories have appeared in over a century’s newspapers, agriculture journals, and magazines. In fact, the Clever Clover idea had been tested well before the advent of Richard Stirzaker. But who knows? Maybe someday, in a world very different from that of today, we’ll reach back to the Clever Clover innovators like Stirzaker and others for guidance.

Part 3, “Feeding Ourselves” examines the global food production system, paying attention to the balance of productivity and ecological footprint. Tillage is a big part of this picture, and Stirzaker devotes a chapter to how our concept of land husbandry has changed over time. Should one double-dig the garden beds or no-till them? How does tillage affect the infiltration of water into the soil? Does soil structure matter? Is permaculture the answer? How are we to educate the next generation of agricultural scientists? Stirzaker explores these and other topics, each arising from questions about what we eat, how we use water, and how to think about agricultural efficiency in a realm of competing interests. “Out of the Scientist’s Garden” is not a “how-to” manual. It will not teach you to make compost or become self-sufficient. There are no recipes for sustainable agriculture; no answers to humanity’s pressing need for ever more food, housing, and fuel. It’s about “how to think about things”, using water as a didactic prop. Stirzaker’s hope is that readers will bear witness of their own stories, perhaps reaching different conclusions. That’s what I’ve attempted to convey in this blog with words and images from my experience. I strongly recommend this book to anyone interested in agriculture, water, sustainability, and natural resources. If you’ve been around the block a few times, there’s bound to be something here that echoes the good ole’ boys refrain “Yeah, I know how that works!”

Further Diggings

FAO: AQUASTAT-FAO’s global information system on water and agriculture, FAO. http://www.fao.org/nr/aquastat, last access: 16 March 2013, Rome, Italy, 2010.

Siebert, S., J. Burke, J.M. Faures, K. Frenken, J. Hoogeveen, P. Döll, and F.T. Portmann. 2010. Groundwater use for irrigation-a global inventory. Hydrol. Earth Syst. Sci. 14(10): 1863-1880. www.hydrol-earth-syst-sci.net/14/1863/2010/, last access: 16 March 2013.