No-Till: The Quiet Revolution - Research - Washington State University

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daniela naomi molnarcent less fuel and 30 to 50 percent less labor thantillage-based agriculture, significantly loweringproduction costs per acre. Although specializedno-till seeding equipment can be expensive, withsome sophisticated seeders priced at more than$100,000, running and maintaining other tillageequipment is no longer necessary, loweringthe total capital and operating costs of machineryrequired for crop establishment by up to 50percent. With these savings in time and money,farmers can be more competitive at smallerscales, or they can expand and farm more acres,sometimes doubling farm size using the sameequipment and labor. Furthermore, many farmersappreciate that the time they once devoted torather mundane tillage tasks they can insteadspend on more challenging aspects of farming,family life or recreation, thereby enhancing theiroverall quality of life.Betting the FarmNo-till and other conservation tillage systemscan work in a wide range of climates, soils andgeographic areas. Continuous no-till is alsoapplicable to most crops, with the notable exceptionsof wetland rice and root crops, such aspotatoes. Yet in 2004, the most recent year forwhich data are available, farmers were practicingno-till on only 236 million acres worldwide—not even 7 percent of total global cropland.Of the top five countries with the largestareas under no-till, the U.S. ranks first, followedby Brazil, Argentina, Canada and Australia.About 85 percent of this no-till land liesin North and South America. In the U.S., roughly41 percent of all planted cropland was farmedusing conservation tillage systems in 2004,compared with 26 percent in 1990. Most of thatgrowth came from expanded adoption of notill,which more than tripled in that time, to thepoint where it was practiced on 22 percent ofU.S. farmland. This no doubt partly reflects thefact that U.S. farmers are encouraged to meetthe definition of conservation tillage to participatein government subsidy and other programs.In South America, adoption of no-till farminghas been relatively rapid as a result of coordinatedefforts by university agricultural-extensioneducators and local farm communities to developviable no-till cropping systems tailored totheir particular needs.On the other hand, adoption rates are low inEurope, Africa and most parts of Asia. Embracingno-till has been especially difficult in developingcountries in Africa and Asia, becauseSoil Loss RatioTWO SIDESOF NO-TILLPayoffsReduces soil erosionConserves waterImproves soil healthReduces fuel and labor costsReduces sediment and fertilizerpollution of lakes and streamsSequesters carbonTrade-offsTransition from conventionalfarming to no-till is difficultNecessary equipment is costlyHeavier reliance on herbicidesPrevalence of weeds, diseaseand other pests may shift inunexpected waysMay initially require morenitrogen fertilizerCan slow germination andreduce yieldsSoil saver10.60.2020 60 100Ground Cover(percent)Leaving 30 percent of the soilsurface covered with residuereduces erosion by half as comparedwith bare, fallow soil. Andleaving 50 to 100 percent of thesurface covered throughout theyear, as no-till does, reduces soilerosion dramatically.farmers there often use the crop residues for fuel,animal feed and other purposes. Furthermore,the specialized seeders required for sowingcrops and the herbicides needed for weed controlmay not be available or can be prohibitivelyexpensive for growers in these parts of theworld. Meanwhile, in Europe, an absence ofgovernment policies promoting no-till, alongwith elevated restrictions on pesticides (includingherbicides), among other variables, leavesfarmers with little incentive to adopt thisapproach.Changing from tillage-based farming to notillis not easy. The difficulty of the transition,together with the common perception that notillincurs a greater risk of crop failure or lowernet returns than conventional agriculture, hasseriously hindered more widespread adoptionof this approach. Although farmers accept thatagriculture is not a fail-safe profession, theywill hesitate to adopt a new farming practice ifthe risk of failure is greater than in conventionalpractice. Because no-till is a radical departurefrom other farming practices, growers makingthe switch to no-till experience a steep learningcurve. In addition to the demands of differentfield practices, the conversion has profoundimpacts on farm soils and fields. Different pestspecies can arise with the shift from tillagebasedagriculture to no-till, for instance. Andthe kinds of weeds and crop diseases can change.For example, the elevated moisture levels associatedwith no-till can promote soil-borne fungaldiseases that tillage previously kept in check.Indeed, the discovery of new crop diseases hassometimes accompanied the shift to no-till.Some of the changes that follow from no-tillcan take years or even decades to unfold, andfarmers need to remain vigilant and adaptableto new, sometimes unexpected, situations, suchas those that arise from shifts in soil and residueconditions or fertilizer management. Duringthis transition, there is a real risk of reducedyields and even failed crops. In the Palouse, forexample, some farmers who attempted no-tillin the 1980s are no longer in business. Consequently,farmers looking to switch to no-tillshould initially limit the converted acreage to10 to 15 percent of their total farm.Farmers who are new to no-till techniquesoften visit successful operations and form localor regional support groups, where they shareexperiences and discuss specific problems. Butthe advice they receive in areas with limited notilladoption can be incomplete or contradictory,www.SciAm.com © 2008 SCIENTIFIC AMERICAN, INC.SCIENTIFIC AMERICAN 75
[A CASE FOR NO-TILL]PAY DIRTand gaps in knowledge, experience or technologycan have potentially disastrous outcomes. Ifthe perception that no-till is riskier than conventionaltechniques develops in a farming community,banks may not underwrite a no-till farmer’sloan. Alternatively, growers who are leasing landmay find that the owners are opposed to no-tillbecause of fears that they will not get paid asmuch. Improving the quality of informationThe slow pace at which soil rebuilds makes its conservation essential By David R. Montgomeryexchange among farmers, universities, agribusinessesand government agencies will no doubt goa long way toward overcoming these obstacles.Yet even in the hands of a seasoned no-tillfarmer, the system has drawbacks. No-till cropproduction on fine-textured, poorly drainedsoils can be particularly problematic, oftenresulting in decreased yields. Yields of no-tillcorn, for instance, are often reduced by 5 to 10fundamental drawback of conventional farming is that it fostersA topsoil erosion, especially on sloping land. Tillage leaves theground surface bare and vulnerable to runoff, and each pass of the plowpushes soil downhill. As a result, the soil thins over time. How long thisprocess takes depends not only on how fast plowing pushes soil downhill—andwind or runoff carries it away—but also on how fast theunderlying rocks break down to form new soil.In the 1950s, when the Soil Conservation Service (now known as theNatural Resources Conservation Service) began defining tolerable ratesof soil erosion from agricultural land, hardly any data on rates of soilproduction were available. The agency thus determined the so-calledsoil loss tolerance values, or T values, on the basis of what farmers coulddo to reduce erosion without“undue economicimpact” using conventionalfarming equipment. These Tvalues correspond to asmuch as an inch of erosionin 25 years. But recentresearch has shown thaterosion rate to be far fasterthan the rate at which soilrebuilds.Over the past severaldecades, scientists havedetermined that measuringthe soil concentrations ofcertain isotopes that form ata known rate permits directquantification of soil productionrates. Applying thistechnique to soils in temperateregions in coastal California and southeastern Australia, geologistArjun Heimsath of Arizona State University and his colleagues found soilproduction rates ranging from 0.00118 to 0.00315 inch a year. As such,it takes 300 to 850 years to form an inch of soil in these places. My ownrecent global compilation of data from soil production studies, publishedlast year in the Proceedings of the National Academy of SciencesUSA, revealed an average rate of 0.00067 to 0.00142 incha year—equivalent to 700 to 1,500 years to form an inch of soil.The soil on undisturbed hillsides in temperate and tropical latitudes isgenerally one to three feet thick. With natural soil production rates ofWIND EROSION in the Southern Plains of the U.S. during the Dust Bowl erarevealed the perils of plow-based farming.centuries to millennia per inch and soil erosion rates of inches per centuryunder plow-based agriculture, it would take just several hundred to acouple of thousand years to plow through the soil in these regions. Thissimple estimate predicts remarkably well the life span of major agriculturalcivilizations around the world. With the exception of the fertile rivervalleys along which agriculture began, civilizations generally lasted 800to 2,000 years, and geoarchaeological studies have now shown a connectionbetween soil erosion and the decline of many ancient cultures.Clearly, then, if we are to conserve resources for future generations,we need alternatives to conventional farming practices. No-till systemssimultaneously reduce the erosive force of runoff and increase the abilityof the ground to hold onto soil, making these methods remarkably effectiveat curbing erosion. In astudy published in 1993,researchers at the University ofKentucky found that no-tillmethods decreased soil erosionby a whopping 98 percent. Morerecently, investigators at theUniversity of Tennessee reportedthat no-till tobacco farmingreduced soil erosion by morethan 90 percent over conventionaltobacco cultivation.Although the effect of no-till onerosion rates depends on a numberof local factors, such as thetype of soil and the crop, it canbring soil erosion rates downclose to soil production rates.In the mid-1990s CornellUniversity researchers estimatedthat undoing damage caused by soil erosion would cost the U.S.$44 billion a year, and that it would take an annual investment of about$6 billion to bring erosion rates on U.S. cropland in line with soil production.They also estimated that each dollar invested in soil conservationwould save society more than $5. Because it is prohibitively expensiveto put soil back on the fields once it leaves, the best, most cost-effectivestrategy for society at large is to keep it on the fields in the first place.David R. Montgomery is a professor of geomorphology at the Universityof Washington and author of Dirt: The Erosion of Civilizations.GETTY IMAGES76 SCIENTIFIC AMERICAN © 2008 SCIENTIFIC AMERICAN, INC.July 2008
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