No-Till: the Quiet Revolution

The age-old practice of turning the before planting a new crop is a leading cause of farmland degradation. Many farmers are thus looking to make plowing a thing of the past By David R. Huggins and John P. Reganold

© 2008 SCIENTIFIC AMERICAN, INC. 70 SCIENTIFIC AMERICAN July 2008 ohn Aeschliman turns over a shovelful of on his 4,000-acre farm in the Palouse Jregion of eastern Washington State. The black earth crumbles easily, revealing a porous structure and an abundance of organic matter that facilitate root growth. Loads of earthworms are visible, too—another healthy sign. Thirty-four years ago only a few earthworms, if any, could be found in a spadeful of his soil. Back then, Aeschliman would plow the fields before each planting, burying the residues from the previous crop and readying the ground for the next one. The hilly Palouse region had been farmed that way for decades. But the tillage was taking a toll on the Palouse, and its famously fertile soil was eroding at an alarming rate. Convinced that there had to be a better way to work the land, Aeschliman decided to experi- ment in 1974 with an emerging method known as no-till farming. Most farmers worldwide plow their land in preparation for sowing crops. The practice of turning the soil before planting buries crop resi- dues, animal manure and troublesome weeds and also aerates and warms the soil. But clear- ing and disturbing the soil in this way can also leave it vulnerable to erosion by wind and water. Tillage is a root cause of agricultural land deg- radation—one of the most serious environmen- tal problems worldwide—which poses a threat to food production and rural livelihoods, par- ticularly in poor and densely populated areas of the developing world [see “Pay Dirt,” by David R. Montgomery, on page 76]. By the late 1970s in the Palouse, had removed 100 percent of the topsoil from 10 percent of the cropland, along with another 25 to 75 percent of the topsoil from another 60 percent of that land. Furthermore, tillage can promote the run- KEY CONCEPTS

off of sediment, and pesticides into n Conventional plow-based rivers, lakes and oceans. No-till farming, in con- farming leaves soil vulner- trast, seeks to minimize soil disruption. Practi- able to erosion and pro- tioners leave on the fields after har- motes agricultural runoff.

vest, where it acts as a mulch to protect the soil n Growers in some parts of from erosion and fosters soil productivity. To the world are thus turning sow the seeds, farmers use specially designed to a sustainable approach seeders that penetrate through the residue to the known as no-till that mini- undisturbed soil below, where the seeds can ger- mizes soil disturbance.

NO-TILL PIONEER John Aeschliman began minate and surface as the new crop. n High equipment costs and experimenting with the technique in In its efforts to feed a growing world popula- a steep learning curve, 1974 out of concern over the soil erosion tion, agriculture has expanded, resulting in a among other factors, are that was taking place in Washington greater impact on the environment, human hindering widespread adop- State’s sloping Palouse region, where health and biodiversity. But given our current tion of no-till practices. his farm is located. knowledge of the planet’s capacity, we now real- —The Editors

ANDY ANDERSON ANDY ize that producing enough food is not enough—

© 2008 SCIENTIFIC AMERICAN, INC. © 2008 SCIENTIFIC AMERICAN, INC. SCIENTIFIC AMERICAN 71 [history] Agriculture milestones The roots of both no-till and tillage-based farming the plow. Over the past few decades, however, methods run deep, but eventually the latter advances in and machinery have made approach predominated, thanks to the evolution of no-till practical on a commercial scale.

8000 B.C. Planting stick, the earliest version of no-till, enables the planting of seeds without cultivation. Scratch plow the earliest plow, clears a path through the ground cover and creates a furrow into which seeds can be placed. 6000 B.C. Draft animals replace humans in powering the plow. 3500 B.C. Plowshare, a wedge-shaped implement tipped with an iron blade, loosens the top layer of soil. 1100 A.D.? Moldboard plow has a curved blade (the moldboard) that inverts the soil, burying weeds and residues. Mid-1800s Steel moldboard plow invented by John Deere in 1837, is able to break up sod. Early 1900s can pull multiple plows at once. 1940s –1950s Herbicides such as 2,4-D,atrazine and paraquat enable farmers to manage weeds with less tillage. 1960s No-till seeders slice open a small groove for seeds, keeping soil disturbance to a minimum. [THE AUTHORs]

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it must also be done sustainably. Farmers need around 10,000 years ago. In the transition from scratch plow scratch (

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tions, make enough money to live on, and be near their dwellings and foraged for other foods epa

socially just to their workers and community in the wild. Some performed the earliest version hong John Deere plow u ( [see “,” by John P. Reg- of no-till by punching holes in the land with a w ); ) anold, Robert I. Papendick and James F. Parr; stick, dropping seeds in each divot and then cov- David R. Huggins (left) is a soil scientist with the USDA-Agricultur- Scientific American, June 1990]. No-till ering it with soil. Others scratched the ground no-till seeder no-till al Research Service, Land Manage- farming is one system that has the potential to with a stick, an incipient form of tillage, to place ( SmithsonianImages ment and Water Conservation help realize this vision of a more sustainable seeds under the surface. Thousands of farmers an Huggins and Reganold and Huggins lm Research Unit in Pullman, Wash. ( ta

agriculture. As with any new system, there are in developing countries still use these simple anderson

He specializes in conservation gh u

challenges and trade-offs with no-till. Neverthe- methods to sow their crops. h

cropping systems and their influ- ); ); andy ence on the cycling and flow less, growers in some parts of the world are In time, working the soil mechanically of and nitrogen. John P. increasingly abandoning their plows. became the standard for planting crops and (

Reganold (right), Regents Profes- hoto controlling weeds, thanks to the advent of the P moldboard plow moldboard sor of Soil Science at Washington WashingtonStateUniversity k (

Plowing Ahead plow, which permitted the labor of a few to sus- iStock he

State University at Pullman, c People have used both no-till and tillage-based tain many. The first such tools were scratch ert ets mb specializes in sustainable agricul- l ture. This is his third article for methods to produce food from the earth ever plows, consisting of a frame holding a vertical a lf ro anel ra l Scientific American. since they started growing their own crops wooden post that was dragged through the top- STEWARTHIGGINS

72 SCIENTIFIC AMERICAN © 2008 SCIENTIFIC AMERICAN, INC. July 2008 © 2008 SCIENTIFIC AMERICAN, INC. soil. Two people probably operated the earliest come to play in farming, conceiving a way to do version of this device, one pulling the tool and without it has proved quite challenging, requir- the other guiding it. But the domestication of ing the reinvention of virtually every aspect of draft animals—such as oxen in Mesopotamia, agricultural production. But specially designed perhaps as early as 6000 B.C.—replaced human seeders have been evolving since the 1960s to power. The next major development occurred meet the unique mechanization requirements of around 3500 B.C., when the Egyptians and the no-till farming. These new seeders, along with Sumerians created the plowshare—a wedge- chemical herbicides, are two of the main technol- shaped wooden implement tipped with an iron ogies that have at last enabled growers to effec- blade that could loosen the top layer of soil. By tively practice no-till on a commercial scale. the 11th century, the Europeans were using an elaboration of this innovation that included a Signing Up for No-Till curved blade called a moldboard that turned Farmers today prepare for planting in ways that the soil over once it was broken open. disturb the soil to varying degrees. Tillage with Continuing advancements in plow design a moldboard plow completely turns over the enabled the explosion of pioneer agriculture ADOPTION first six to 10 inches of soil, burying most of the during the mid-1800s; farmers cultivated grass- residue. A chisel plow, meanwhile, only frac- dominated native in eastern Europe, HURDLES tures the topsoil and preserves more surface res- South Africa, Canada, Australia, New Zealand Although no-till is theoretically idue. In contrast, no-till methods merely create and the U.S., converting them to corn, wheat applicable to most farmland in each planted row a groove just half an inch to around the world, the cost and other crops. One such region, the tall-grass three inches across into which seeds can be of the requisite equipment and prairie of the Midwestern U.S., had resisted herbicides is prohibitive for dropped, resulting in minimal overall soil dis- widespread farming because its thick, sticky sod many growers, most of whom turbance. In the U.S., no-till agriculture fits was a barrier to cultivation. But in 1837 an Illi- have small farms. Necessary under the broader U.S. Department of Agricul- nois blacksmith named John Deere invented a costs aside, poverty itself leads ture definition of conservation tillage. Conser- these farmers to use crop smooth, steel moldboard plow that could break vation tillage includes any method that retains residues and animal dung for up the sod. Today this former grassland, which fuel, for example, and to till the enough of the previous crop residues such that includes much of the famous Corn Belt, is home land for short-term gains rather at least 30 percent of the soil surface is covered to one of the most agriculturally productive than investing in long-term after planting. The protective effects of such areas in the world. stewardship. residues are considerable. According to the Of 525 million farms world­ Agricultural mechanization continued USDA’s National Resources Inventory data, soil wide, roughly 85 percent are through the early 1900s with the development less than five acres. The over- erosion from water and wind on U.S. cropland of many tools that helped farmers cultivate the whelming majority of these decreased 43 percent between 1982 and 2003, earth ever more intensively, including tractors small farms—about 87 per- with much of this decline coming from the adop- that could pull multiple plows at once. Tillage cent—are located in Asia tion of conservation tillage. (above); Africa is home to practices were about to undergo profound scru- Soil protection is not the only benefit of no- 8 percent. The adoption of tiny, however. The Dust Bowl era between 1931 no-till farming in these regions, till. Leaving crop residues on the soil surface and 1939 exposed the vulnerability of plow- where the potential benefits helps to increase water infiltration and limit run- based agriculture, as wind blew away precious are the greatest, is practically off. Decreased runoff, in turn, can reduce pollu- topsoil from the drought-ravaged southern negligible. tion of nearby water sources with transported plains of the U.S., leaving behind failed crops sediment, fertilizers and pesticides. The residues and farms. Thus, the move- also promote water conservation by reducing ment was born, and agriculturalists began to evaporation. In instances where water availabil- explore reduced tillage methods that preserve ity limits crop production, greater water conser- crop residues as a protective ground cover. Spur- vation can mean higher-yielding crops or new

ring the movement was the controversial publi- capabilities to grow alternative crops. cation in 1943 of Plowman’s Folly, by agrono- The no-till approach also fosters the diversity mist Edward Faulkner, who challenged the of soil flora and fauna by providing soil organ- necessity of the plow. Faulkner’s radical propo- isms, such as earthworms, with food from the sition became more tenable with the develop- residues and by stabilizing their habitat. Togeth- ment of herbicides —such as 2,4-D, atrazine and er with associated increases in soil organic mat- paraquat—after World War II, and research on ter, these conditions encourage to develop NationalGeographic/Getty Images modern methods of no-till agriculture began in a more stable internal structure, further improv- ONGER C earnest during the 1960s. ing the overall capacity to grow crops and to

DEAN Considering the pivotal role the plow has buffer them against stresses caused by farming

www.SciAm.com © 2008 SCIENTIFIC AMERICAN, INC. SCIENTIFIC AMERICAN 73 [A PRIMER] HOW NO-TILL STACKS UP Three farming systems for a corn-soybean in the U.S. Corn Belt are contrasted here. No-till requires the fewest passes over a field.

NO-TILL CONSERVATION TILLAGE CONVENTIONAL TILLAGE 1. Apply 1. Till with chisel plow, burying 1. Till with moldboard plow, 2. Plant up to 50 percent burying up to 90 percent of crop residue 3. Apply herbicide of crop residue 2. Till with disk to smooth the ground surface 4. Harvest 2. Till with field 3. Till with field cultivator to prepare 3. Plant the for planting 4. Apply herbicide 4. Till with harrows to smooth seedbed Soybean and After harvest, corn residues standing corn stalks 5. Till with row cultivator 5. Plant cover soil and fallen grain 6. Harvest 6. Apply herbicide surface, provide shelter and 7. Till with row cultivator conserving food for wildlife (bird water and not drawn to scale) 8. Harvest reducing erosion by 70 Soybean residue to 100 covers 30 percent Soil surface is bare, percent leaving it vulnerable of the soil surface, to erosion by wind halving erosion and water

0 inches Dark surface enhances soil warming, which promotes corn growth

10

Plow can smear and compact the soil, forming a “pan” that restricts water movement and root growth 20

30 Earthworms proliferate, creating Granular soil Conservation Tillage disrupts granular channels that foster root growth structure tillage leads , forming achieved with to granular large clods that limit no-till improves soil structure water infiltration, interspersed root growth and small reducing erosion with clods particles that can be dislodged by raindrops, leading to erosion

operations or environmental hazards. No-till main greenhouse gas mitigation strategies is soil can thus enable the more sustainable farming of carbon sequestration, wherein crops remove moderately to steeply sloping lands that are at carbon dioxide from the atmosphere during elevated risk of erosion and other problems. photosynthesis, and nonharvested residues and Wildlife, too, gains from no-till, because roots are converted to soil organic matter, which standing crop residues and inevitable harvest is 58 percent carbon. About half of the overall losses of grain provide cover and food for upland potential for U.S. croplands to sequester soil game birds and other species. In a study pub- carbon comes from conservation tillage, includ- lished in 1986, researchers in Iowa found 12 ing no-till. bird species nesting in no-till fields, compared In addition, no-till can offer economic advan- with three species in tilled fields. tages to farmers. The number of passes over a Furthermore, reducing tillage increases soil field needed to establish and harvest a crop with carbon sequestration, compared with conven- no-till typically decreases from seven or more to EVIN HAND EVIN

tional moldboard plowing. One of agriculture’s four or fewer. As such, it requires 50 to 80 per- K

74 SCIENTIFIC AMERICAN © 2008 SCIENTIFIC AMERICAN, INC. July 2008 cent less fuel and 30 to 50 percent less labor than farmers there often use the crop residues for fuel, tillage-based agriculture, significantly lowering TWO SIDES animal feed and other purposes. Furthermore, production costs per acre. Although specialized OF NO-TILL the specialized seeders required for sowing no-till seeding equipment can be expensive, with crops and the herbicides needed for weed con- some sophisticated seeders priced at more than Payoffs trol may not be available or can be prohibitively $100,000, running and maintaining other till- Reduces soil erosion expensive for growers in these parts of the age equipment is no longer necessary, lowering Conserves water world. Meanwhile, in Europe, an absence of the total capital and operating costs of machin- government policies promoting no-till, along Improves soil health ery required for crop establishment by up to 50 with elevated restrictions on pesticides (includ- percent. With these savings in time and money, Reduces fuel and labor costs ing herbicides), among other variables, leaves farmers can be more competitive at smaller Reduces sediment and farmers with little incentive to adopt this scales, or they can expand and farm more acres, pollution of lakes and streams approach. sometimes doubling farm size using the same Changing from tillage-based farming to no- Sequesters carbon equipment and labor. Furthermore, many farm- till is not easy. The difficulty of the transition, ers appreciate that the time they once devoted to Trade-offs together with the common perception that no- rather mundane tillage tasks they can instead till incurs a greater risk of crop failure or lower Transition from conventional spend on more challenging aspects of farming, net returns than conventional agriculture, has farming to no-till is difficult family life or recreation, thereby enhancing their seriously hindered more widespread adoption overall quality of life. Necessary equipment is costly of this approach. Although farmers accept that Heavier reliance on herbicides agriculture is not a fail-safe profession, they will hesitate to adopt a new farming practice if Betting the Farm Prevalence of weeds, disease No-till and other conservation tillage systems and other pests may shift in the risk of failure is greater than in convention- can work in a wide range of climates, soils and unexpected ways al practice. Because no-till is a radical departure geographic areas. Continuous no-till is also from other farming practices, growers making May initially require more applicable to most crops, with the notable excep- nitrogen fertilizer the switch to no-till experience a steep learning tions of wetland rice and root crops, such as curve. In addition to the demands of different Can slow germination and potatoes. Yet in 2004, the most recent year for field practices, the conversion has profound reduce yields which data are available, farmers were practic- impacts on farm soils and fields. Different pest ing no-till on only 236 million acres worldwide— species can arise with the shift from tillage- not even 7 percent of total global cropland. based agriculture to no-till, for instance. And Of the top five countries with the largest the kinds of weeds and crop diseases can change. areas under no-till, the U.S. ranks first, fol- For example, the elevated moisture levels asso- lowed by Brazil, Argentina, Canada and Aus- ciated with no-till can promote soil-borne fun- tralia. About 85 percent of this no-till land lies gal diseases that tillage previously kept in check. in North and South America. In the U.S., rough- Indeed, the discovery of new crop diseases has ly 41 percent of all planted cropland was farmed Soil saver sometimes accompanied the shift to no-till. using conservation tillage systems in 2004, 1 Some of the changes that follow from no-till compared with 26 percent in 1990. Most of that can take years or even decades to unfold, and growth came from expanded adoption of no- farmers need to remain vigilant and adaptable till, which more than tripled in that time, to the 0.6 to new, sometimes unexpected, situations, such point where it was practiced on 22 percent of as those that arise from shifts in soil and residue oss Ratio U.S. farmland. This no doubt partly reflects the conditions or fertilizer management. During

fact that U.S. farmers are encouraged to meet Soil L 0.2 this transition, there is a real risk of reduced the definition of conservation tillage to partici- yields and even failed crops. In the Palouse, for pate in government subsidy and other programs. 0 example, some farmers who attempted no-till 20 60 100 In South America, adoption of no-till farming in the 1980s are no longer in business. Conse- Ground Cover has been relatively rapid as a result of coordinat- (percent) quently, farmers looking to switch to no-till ed efforts by university agricultural-extension should initially limit the converted acreage to Leaving 30 percent of the soil educators and local farm communities to devel- 10 to 15 percent of their total farm. surface covered with residue op viable no-till cropping systems tailored to Farmers who are new to no-till techniques reduces erosion by half as com- nar their particular needs. often visit successful operations and form local l pared with bare, fallow soil. And o m i On the other hand, adoption rates are low in leaving 50 to 100 percent of the or regional support groups, where they share m Europe, Africa and most parts of Asia. Embrac- experiences and discuss specific problems. But nao surface covered throughout the a l ing no-till has been especially difficult in devel- year, as no-till does, reduces soil the advice they receive in areas with limited no-

danie oping countries in Africa and Asia, because erosion dramatically. till adoption can be incomplete or contradictory,

www.SciAm.com © 2008 SCIENTIFIC AMERICAN, INC. SCIENTIFIC AMERICAN 75 and gaps in knowledge, experience or technolo- exchange among farmers, universities, agribusi- gy can have potentially disastrous outcomes. If nesses and government agencies will no doubt go the perception that no-till is riskier than conven- a long way toward overcoming these obstacles. tional techniques develops in a farming commu- Yet even in the hands of a seasoned no-till nity, banks may not underwrite a no-till farmer’s farmer, the system has drawbacks. No-till crop loan. Alternatively, growers who are leasing land production on fine-textured, poorly drained may find that the owners are opposed to no-till soils can be particularly problematic, often because of fears that they will not get paid as resulting in decreased yields. Yields of no-till much. Improving the quality of information corn, for instance, are often reduced by 5 to 10 [A CASE FOR NO-TILL] PAY DIRT The slow pace at which soil rebuilds makes its conservation essential By David R. Montgomery

fundamental drawback of conventional farming is that it fosters centuries to millennia per inch and soil erosion rates of inches per century A topsoil erosion, especially on sloping land. Tillage leaves the under plow-based agriculture, it would take just several hundred to a ground surface bare and vulnerable to runoff, and each pass of the plow couple of thousand years to plow through the soil in these regions. This pushes soil downhill. As a result, the soil thins over time. How long this simple estimate predicts remarkably well the life span of major agricul- process takes depends not only on how fast plowing pushes soil down- tural civilizations around the world. With the exception of the fertile river hill—and wind or runoff carries it away—but also on how fast the valleys along which agriculture began, civilizations generally lasted 800 underlying rocks break down to form new soil. to 2,000 years, and geoarchaeological studies have now shown a con- In the 1950s, when the Soil Conservation Service (now known as the nection between soil erosion and the decline of many ancient cultures. Natural Resources Conservation Service) began defining tolerable rates Clearly, then, if we are to conserve resources for future generations, of soil erosion from agricultural land, hardly any data on rates of soil we need alternatives to conventional farming practices. No-till systems production were available. The agency thus determined the so-called simultaneously reduce the erosive force of runoff and increase the ability soil loss tolerance values, or T values, on the basis of what farmers could of the ground to hold onto soil, making these methods remarkably effec- do to reduce erosion with- tive at curbing erosion. In a out “undue economic study published in 1993, impact” using conventional researchers at the University of farming equipment. These T Kentucky found that no-till values correspond to as methods decreased soil erosion much as an inch of erosion by a whopping 98 percent. More in 25 years. But recent recently, investigators at the research has shown that University of Tennessee reported erosion rate to be far faster that no-till tobacco farming than the rate at which soil reduced soil erosion by more rebuilds. than 90 percent over conven- Over the past several tional tobacco cultivation. decades, scientists have Although the effect of no-till on determined that measuring erosion rates depends on a num- the soil concentrations of ber of local factors, such as the certain isotopes that form at type of soil and the crop, it can a known rate permits direct bring soil erosion rates down WIND EROSION in the Southern Plains of the U.S. during the Dust Bowl era quantification of soil pro- close to soil production rates. revealed the perils of plow-based farming. duction rates. Applying this In the mid-1990s Cornell technique to soils in temper- University researchers estimat- ate regions in coastal California and southeastern Australia, geologist ed that undoing damage caused by soil erosion would cost the U.S. Arjun Heimsath of Arizona State University and his colleagues found soil $44 billion a year, and that it would take an annual investment of about production rates ranging from 0.00118 to 0.00315 inch a year. As such, $6 billion to bring erosion rates on U.S. cropland in line with soil produc- it takes 300 to 850 years to form an inch of soil in these places. My own tion. They also estimated that each dollar invested in soil conservation recent global compilation of data from soil production studies, pub- would save society more than $5. Because it is prohibitively expensive lished last year in the Proceedings of the National Academy of Sciences to put soil back on the fields once it leaves, the best, most cost-effective USA, revealed an average rate of 0.00067 to 0.00142 inch strategy for society at large is to keep it on the fields in the first place. a year—equivalent to 700 to 1,500 years to form an inch of soil. The soil on undisturbed hillsides in temperate and tropical latitudes is David R. Montgomery is a professor of geomorphology at the University AGES

generally one to three feet thick. With natural soil production rates of of Washington and author of Dirt: The Erosion of Civilizations. M GETTY I GETTY

76 SCIENTIFIC AMERICAN © 2008 SCIENTIFIC AMERICAN, INC. July 2008 © 2008 SCIENTIFIC AMERICAN, INC. [WHERE IT IS USED] percent on these kinds of soils, compared with yields with conventional tillage, particularly in NO-TILL ACREAGE northern regions. And because the crop residue Less than 7 percent of the world’s cropland is farmed using no-till methods. Of these blocks the sun’s rays from warming the earth to 236 million acres, about 85 percent are in North and South America. the same degree as occurs with conventional tillage, soil temperatures are colder in the spring, U.S. Brazil which can slow seed germination and curtail 62,528,000 58,317,000 Indus and the early growth of warm-season crops, such as Ganges River corn, in northern latitudes. Basins* 4,695,000 In the first four to six years, no-till demands South the use of extra nitrogen fertilizer to meet the Africa 741,000 nutritional requirements of some crops, too —up Canada Argentina 30,943,000 to 20 percent more than is used in conventional 45,144,000 tillage systems—because increasing organic mat- Paraguay ter at the surface immobilizes nutrients, includ- 4,201,000 ing nitrogen. And in the absence of tillage, farm- ers depend more heavily on herbicides to keep Australia weeds at bay. Herbicide-resistant weeds are Spain Venezuela Others 741,000 741,000 (estimate) 22,239,000 already becoming more common on no-till farms. 2,470,000 The continued practice of no-till is therefore highly dependent on the development of new her- bicide formulations and other weed management Bolivia Uruguay Chile Colombia China France 1,359,000 650,000 297,000 252,000 247,000 371,000 options. Cost aside, greater reliance on agrichem- icals may adversely affect nontarget species or *Encompasses much of India, Pakistan and Bangladesh. contaminate air, water and soil. Source: United Nations Food and Agriculture Organization. Data from 2004. Integrating No-Till No-till has the potential to deliver a host of ben- appealing to farmers. But the current emphasis efits that are increasingly desirable in a world on corn to produce ethanol in the Midwestern facing population growth, environmental deg- Corn Belt, for instance, is promoting monocul- ➥ m ore to radation, rising energy costs and climate change, ture—in which a single crop, such as corn, is explore among other daunting challenges. But no-till is grown over a wide area and replanted every Corn-Soybean Sequence and — not a cure-all; such a thing does not exist in year and will likely make no-till farming more Tillage Effects on Soil Carbon agriculture. Rather it is part of a larger, evolv- difficult in this region. Experts continue to Dynamics and Storage. David R. ing vision of sustainable agriculture, in which a debate the merits of growing fuel on farmland, Huggins, Raymond R. Allmaras, diversity of farming methods from no-till to but if we decide to proceed with biofuel crops, Charles E. Clapp, John A. Lamb and Gyles W. Randall in Soil Science Soci- organic—and combinations thereof—is consid- we will need to consider using no-till with crop ety of America Journal, Vol. 71, No. 1, ered healthy. We think that ultimately all farm- rotation to produce them sustainably. Develop- pages 145–154; January/February ers should integrate conservation tillage, and ment of alternative crops for bioenergy produc- 2007. no-till if feasible, on their farms. tion on marginal lands, including perennials Future no-till farming will need to employ such as switchgrass, could complement and pro- Constraints to Adopting No-Till more diverse pest and weed management strate- mote no-till farming, as would perennial grain Farming in Developing Countries. Rattan Lal in Soil & Tillage Research, gies, including biological, physical and chemical food crops currently under development [see Vol. 94, No. 1, pages 1–3; May 2007. measures to lessen the threat of pesticide resis- “Future Farming: A Return to Roots?” by Jerry tance. Practices from successful D. Glover, Cindy M. Cox and John P. Reganold; Dirt: The Erosion of Civilizations. systems may be instructive in that regard. One Scientific American,August 2007]. David R. Montgomery. University of California Press, 2007. such technique, crop rotation—in which farm- Today, three decades after first attempting ers grow a series of different crops in the same no-till on his Palouse farm, John Aeschliman No-Tillage Seeding in Conserva- space in sequential seasons—is already helping uses the system on 100 percent of his land. His tion Agriculture. Second edition. no-till’s war on pests and weeds by helping to adoption of no-till has followed a gradual, cau- C. John Baker et al. CABI Publishing, break up the weed, pest and disease cycles that tious path that has helped minimize his risk of 2007. arise when one species is continuously grown. reduced yields and net returns. Consequently, he More information about conservation To that end, the capacity to grow a diverse is one of many farmers, large and small, who is agriculture from the United Nations selection of economically viable crops would reaping the rewards of no-till farming and help- Food and Agriculture Organization is EVIN HAND EVIN

K advance no-till farming and make it more ing agriculture evolve toward sustainability. n available at www.fao.org/ag/ca

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