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No-Tillage Crop Production: A Revolution in Agriculture!

^a Dep. of Plant and Soil Scineces, Mississippi State Univ., Mississippi State, MS 39762
^b School of Environment and Natural Resources, Ohio State Univ.–OARDC, 1680 Madison Ave., Wooster, OH 44691-4096

^* Corresponding author (dick.5{at}osu.edu).

	ABSTRACT

TOP NOTES ABSTRACT INTRODUCTION HISTORY OF NO-TILLAGE TILLAGE AND CROP PRODUCTION... NO-TILLAGE AND SOIL EROSION EQUIPMENT AND THE DEVELOPMENT... NO-TILLAGE AND WEED CONTROL CROP RESPONSES TO NO-TILLAGE NO-TILLAGE AND CROP NUTRITION SOIL AND HYDROLOGIC RESPONSES... NO-TILLAGE AND FARM ECONOMICS THE FUTURE OF NO-TILLAGE REFERENCES

 
For thousands of years, agriculture and tillage were considered synonymous. It was simply not thought possible to grow crops without first tilling the soil before planting and for weed control. The advent of modern herbicides permitted no-tillage (NT) to be developed and practiced on actual working family farms. No-tillage is generally defined as planting crops in unprepared soil with at least 30% mulch cover. Adoption of NT after its successful demonstration in the 1950s was slow. However, with better planters, herbicides, and accumulated experience, NT began to be widely adopted in the 1980s in the United States and then in Australia, South America, and Canada. Today, approximately 23% of the total cropland in the United States is planted using NT. No-tillage has revolutionized agricultural systems because it allows individual producers to manage greater amounts of land with reduced energy, labor, and machinery inputs. At the same time, NT is a very effective erosion control measure and improves water and fertilizer use efficiency so that many crops yield better under NT than under tilled systems. Tillage, like crops, can be rotated but the benefits of NT are most likely to be realized with continuous application. We review some of the early work that led to the development of NT and how NT impacts the crop, soil, hydrology, and farm economics. While highly sustainable, there are still many challenges that remain for researchers to solve so the benefits of NT can be realized on expanded land area and for more crops, worldwide.

Abbreviations: CV, coefficient of variability • NT, no-tillage • PT, plow tillage • RUSLE, Revised Universal Soil Loss Equation • T, Soil loss tolerance factors • USLE, Universal Soil Loss Equation • WEPP, Water Erosion Prediction Program

	NOTES

TOP NOTES ABSTRACT INTRODUCTION HISTORY OF NO-TILLAGE TILLAGE AND CROP PRODUCTION... NO-TILLAGE AND SOIL EROSION EQUIPMENT AND THE DEVELOPMENT... NO-TILLAGE AND WEED CONTROL CROP RESPONSES TO NO-TILLAGE NO-TILLAGE AND CROP NUTRITION SOIL AND HYDROLOGIC RESPONSES... NO-TILLAGE AND FARM ECONOMICS THE FUTURE OF NO-TILLAGE REFERENCES

 
All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher.

Received for publication January 3, 2007.

	INTRODUCTION

TOP NOTES ABSTRACT INTRODUCTION HISTORY OF NO-TILLAGE TILLAGE AND CROP PRODUCTION... NO-TILLAGE AND SOIL EROSION EQUIPMENT AND THE DEVELOPMENT... NO-TILLAGE AND WEED CONTROL CROP RESPONSES TO NO-TILLAGE NO-TILLAGE AND CROP NUTRITION SOIL AND HYDROLOGIC RESPONSES... NO-TILLAGE AND FARM ECONOMICS THE FUTURE OF NO-TILLAGE REFERENCES

 
There are few revolutions in agriculture that occur in any one lifetime. In the past 100 yr, several revolutions have occurred that impacted crop productivity and the way we practice agriculture. Included in any listing of such revolutions would be the development of fossil fuel power and mechanization of agriculture, introduction of hybrid and genetically modified crops, increased use of fertilizers, development of synthetic compounds for pest control, and improved data management. To illustrate the influence these changes have made on productivity, average maize (Zea mays L.) yields in the Midwest have increased sixfold since the 1930s and eightfold in the Southeast. This is despite degradation of the soil resource, loss of topsoil, and reduction in organic matter and structural stability through continuous tillage. An additional revolution that has greatly impacted agriculture throughout the world is the development of no-tillage (NT) agriculture.

We can see more clearly today the many benefits of NT because we stand on the shoulders of pioneers who persevered despite initial failures, ridicule, and lack of proper tools and equipment. In this centennial supplement of the esteemed Agronomy Journal, we will provide a brief history of NT development. This will be followed by a summary review of some of the major ways NT affects crop production and our environment. When writing this article, we emphasized older papers in which many of the original observations and ideas about NT were first reported.

	HISTORY OF NO-TILLAGE

TOP NOTES ABSTRACT INTRODUCTION HISTORY OF NO-TILLAGE TILLAGE AND CROP PRODUCTION... NO-TILLAGE AND SOIL EROSION EQUIPMENT AND THE DEVELOPMENT... NO-TILLAGE AND WEED CONTROL CROP RESPONSES TO NO-TILLAGE NO-TILLAGE AND CROP NUTRITION SOIL AND HYDROLOGIC RESPONSES... NO-TILLAGE AND FARM ECONOMICS THE FUTURE OF NO-TILLAGE REFERENCES

 
No-tillage and reduced tillage have been used since ancient times by indigenous cultures. This was because tillage to any depth required more energy and power than was generally possible with hand labor. The ancient Egyptians and the Incas in the Andes of South America used a stick to make a hole in the ground and put seeds by hand into unprepared soil (Derpsch, 1998). North American Indians placed corn seed in a hole with a fish. Even today, in some parts of the world that use shifting cultivation, seed is dropped into a hole after clearing the forest by burning. However, with development of animal power and tillage implements, tillage rapidly became synonymous with agriculture. The International Soil Tillage Research Organization and the journal Soil & Tillage Research has, as its symbol, a pair of oxen pulling a plow in ancient Egypt. Folk wisdom also viewed tillage as a major requirement.

Plow deep
and you will have corn
To sell and to keep
(Ohio folk saying)

Tillage, indeed, greatly aided the enhancement of food production by creating a seedbed for easier planting and by controlling competition by weeds. In many parts of North and South America, European settlers that migrated to the new world did not worry about the long-term sustainability of their farms. "New ground" was highly prized because of higher productivity and if farms were "worn out" by cropping, so be it. There was plenty of land available elsewhere. As land was cleared and farmed, tillage accelerated organic matter oxidation, which supplied N for crop nutrition. Tillage also accelerated soil loss and structural degradation, especially in the southeastern United States due to more rapid organic matter decomposition with warmer temperatures and the greater erosion potential with higher amounts and more intense rainfall that are characteristic of the region. When cropping became unprofitable on eroded and nutrient-depleted fields, these were abandoned or relegated to pasture or forest growth and the settlers moved west seeking uncropped and more productive land. The same pattern was repeated in the upper Midwest, although not as dramatically. Eastern Ohio contains hilly areas that were cleared, farmed, and then abandoned, although not on the scale found in the southeast. Obviously, these types of land use practices are not sustainable. The latest cycle of intense cropping with associated land degradation occurred during the 1970s when crop prices doubled and remained high for several seasons. Fences were removed, pastures were tilled, woodlands were pushed up and burned, and these areas planted to row crops. In short order, both productivity and prices declined to unprofitable levels and cropping was abandoned.

Eventually agriculturists recognized the problems associated with excessive tillage and attempted to develop systems that protected the soil resource. These included contour farming, cover crops, and terraces, all of which reduced but did not eliminate soil erosion.

With the publication of his classic book, "Plowman's Folly," Edward Faulkner (1943) challenged the conventional wisdom of the day by stating in the very first sentence of the very first page "Briefly, this book sets out to show that the moldboard plow which is in use on farms throughout the civilized world, is the least satisfactory implement for the preparation of crops." He went on to say, "The truth is that no one has ever advanced a scientific reason for plowing." These were revolutionary ideas at the time and met with ridicule and scorn.

Earlier attempts to grow crops in untilled soil were moderately successful but never widely adopted. Faulkner (1943) advocated a system that included disking and maintaining a surface mulch. Also proposed and evaluated was a plow–plant system in which a strip was prepared for a seedbed in a moldboard-plowed field while the area between rows remained undisturbed (Cook et al., 1953; Fanning and Brady, 1963). Rainfall was trapped in pockets left by primary tillage, reducing runoff and soil loss, but the rough surface between crop rows interfered with cultivation and harvest traffic.

Seeding of forage crops directly into sod began in the early 1950s for pasture renovation and winter forage production. Since pastures are often relegated to sloping sites considered marginal for tilled agriculture, a system that minimized soil disturbance and maintained cover during forage establishment and renovation was especially desirable. Sprague (1952) used herbicides to control weeds in pastures and introduce more productive forage species. Dudley and Wise (1953) seeded small grains into warm-season perennial vegetation for winter grazing. They worked with John Deere in evaluating a Grassland Drill that would plant into untilled soil. In both cases, crop establishment was the most important goal, but competition from surviving vegetation reduced growth of the new seedlings.

The first sustained NT development for corn began in 1960, both in Virginia (Moody et al., 1961) and in Ohio (Triplett et al., 1964). It is not coincidental that the herbicide atrazine was introduced at about this time. Atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) at the maximum use rate (4.5 kg active ha^–1) was most effective when applied in early spring while plants were still in the vegetative state, and would control many C-3 grasses common in the midwestern United States. These included perennials in the Poa, Phleum, Dactylis, Agrostis, Festuca, Agropyron, and Bromus genera. Atrazine also provided broad-spectrum residual control of many germinating weed seedlings. When combined with 2,4-D ((2,4-dichlorophenoxy)acetic acid) or dicamba (3,6-dichloro-O-anisic acid) to control perennial broadleaf species, plus crop oil or a surfactant to improve foliar activity, season-long vegetation control could be reasonably expected. Paraquat (1,1'-Dimethyl-4,4'-bipyridinium dichloride) and glyphosate (N-(phosphonomethyl)glycine) were developed later and, although they certainly made weed control much easier, were not necessary for NT development to be initiated.

Worldwide adoption of NT has been reviewed by Derpsch (1998) and has been rapid since about 1990. In South American countries, NT was initially adopted because it was perceived to be an efficient technology for soil conservation. For example, in Brazil, the spread of arable farming had created widespread accelerated erosion in the southern states. During the 1970s, agronomists worried that land clearing and tilled farming, in response to high soybean [Glycine max (L.) Merr.] prices, would degrade the soil resource so that crop productivity would not be sustainable. However, over time the technology has evolved into a truly sustainable production system with positive economic, environmental and social benefits. Although the biggest area under NT is in the United States, other countries have adopted NT more extensively in terms of total percentage of cropland planted (Table 1 ). In 2004, the most recent year of information available for the United States, more than 24 million ha (23% of total cropland) was planted using NT for production of corn, soybean, wheat (Triticum aesitivum L.), and cotton (Gossypium hirsutum L.) (Conservation Technology Information Center, 2005).

Asia and Europe have been slower to adopt NT, primarily due to their long history of conventional tillage practices and small farms that have traditionally been intensively managed. However, reports from the 2006 Conference of the International Soil Tillage Research Organization (International Soil Tillage Research Organization, 2006) indicate this is changing.

	TILLAGE AND CROP PRODUCTION LIMITATIONS

TOP NOTES ABSTRACT INTRODUCTION HISTORY OF NO-TILLAGE TILLAGE AND CROP PRODUCTION... NO-TILLAGE AND SOIL EROSION EQUIPMENT AND THE DEVELOPMENT... NO-TILLAGE AND WEED CONTROL CROP RESPONSES TO NO-TILLAGE NO-TILLAGE AND CROP NUTRITION SOIL AND HYDROLOGIC RESPONSES... NO-TILLAGE AND FARM ECONOMICS THE FUTURE OF NO-TILLAGE REFERENCES

 
A primary goal of crop management is to identify factors that limit crop productivity and to correct these within constraints imposed by economic considerations. These factors include establishing the crop at the proper time and with a suitable population, supplying moisture and nutrients needed for the developing crop, and control of weed, insect, and disease pests. Tillage, or lack of tillage, can have a major impact on these factors and, in turn, on crop productivity. As agriculture evolved, management factors required for crop production were applied as components of a system, commonly developed by trial and error, and were often site and crop specific.

There are both advantages and disadvantages associated with tillage (Table 2 ). Crops can be grown with either a great deal or very little tillage. Knowledgeable producers can select tillage systems that solve problems without creating others that are unacceptable.

	NO-TILLAGE AND SOIL EROSION

TOP NOTES ABSTRACT INTRODUCTION HISTORY OF NO-TILLAGE TILLAGE AND CROP PRODUCTION... NO-TILLAGE AND SOIL EROSION EQUIPMENT AND THE DEVELOPMENT... NO-TILLAGE AND WEED CONTROL CROP RESPONSES TO NO-TILLAGE NO-TILLAGE AND CROP NUTRITION SOIL AND HYDROLOGIC RESPONSES... NO-TILLAGE AND FARM ECONOMICS THE FUTURE OF NO-TILLAGE REFERENCES

As soil loss data from NT sites became available, the equations were expanded with benefits ascribed to the C factor. Initially, benefits predicted NT with cover to provide a 5x to 10x reduction in water erosion when compared with moldboard plowing. The early assessment of NT reduction in water erosion was based on a limited data set and may have been conservative in setting benefits for the practice. The earlier versions of the USLE were considered a guide to soil loss potential with different management practices, given different soil and topography conditions, a valuable contribution but with no regulatory function. In the mid 1980s, the USLE was adopted as a regulatory tool for agricultural programs. Various limitations were placed on soil loss and crops for producers who received payment from specified government programs. With this shift in emphasis, more realistic delineation of soil loss with tillage and cropping practices became critical. Van Doren et al. (1984) state that soil loss for sites not tilled for more than 1 yr was 90% less than expected, based on the USLE values at that time. Erosion studies, conducted by comparing results from a set of small, paired, and similarly managed conventional tilled watersheds at the USDA station near Coshocton, OH, are particularly revealing (Harrold and Edwards, 1974). Data from the two watersheds for seven large storms during the period of 1941–1969 showed similar amounts of soil loss. However, after establishing one watershed in NT and continuing the other in conventional tillage, the cumulative soil loss differences in the years from 1970 to 1973 clearly demonstrated the effectiveness of NT to control erosion (Fig. 1 ).

View larger version (20K): [in this window] [in a new window]   Fig. 1. Cumulative soil loss from NT and PT watersheds at Coshocton, OH, for the years of 1970–1973. The erosion events are all rainfall events that produced runoff and erosion during this time period. To visualize the NT values, they were multiplied by 10 before being plotted in the graph (from Harrold and Edwards, 1974).

Several mechanisms serve to reduce water erosion with NT crop production. Raindrop impact provides the major energy source in dislodging soil particles to initiate erosion. Mulch cover on the soil surface intercepts raindrops and absorbs much of this energy. Untilled soil requires more energy to dislodge particles than for bare soil loosened by tillage. After particles are dislodged, they are transported off site in overland flow of runoff. Transport is necessary for erosion to occur. Mulch and vegetative cover from standing plants decrease flow rates, reducing the suspension and transport of soil particles. Plant roots growing at or near the soil-mulch interface bind soil particles and create additional resistance to dislodging particles and soil movement.

A major factor in developing sustainable agricultural production systems is minimizing soil loss so as to protect the soil resource. Soil loss tolerance factors (T) range from 4.5 to 11 Mg ha^–1 yr^–1, depending on soil characteristics. This is generally considered to reflect the rate of soil formation required to renew the resource. However, this rate of soil renewal could be questioned as being too high. Soils providing shallow cover over consolidated parent material that resists weathering would be especially impacted by loss of surface layers and decrease in depth. The Black Belt of Mississippi and Alabama was a natural prairie comprised of soils developed from marine deposits over chalk. Soil loss from tilled agriculture has reduced soil depth and productivity potential in this area. Other soils containing a fragipan too deep to be broken by tillage would have productivity reduced as the upper layer of friable soil is removed.

Van Doren and Triplett (1982) applied the USLE to Ohio data from The 1967 Land Use Inventory (USDA, 1967) to estimate land use potential with various tillage practices and with restrictions applied to soil loss. The most conserving moldboard plow system allowed annual row crop production on slightly more than half the cropland, pasture, and idle land in Ohio, on slopes ranging from 0 to 18%. With the same conditions, the value for the best NT system was 84%. The C factors for the USLE equations used at the time of this analysis (0.026 for NT) were less favorable than those currently in use. With C factors of 0.01 or 0.005 for some NT systems, the land use potential would be from 90 to 95%, even with a more stringent soil loss restriction. Rainfall amount and intensity (R) in the equation varies with location, but this comparison clearly shows that with NT, crops could be grown on much greater areas while protecting the soil resource base.

The energy source for wind erosion is wind velocity at the soil surface. Sand grains set in motion by wind pressure skip across the soil surface, dislodging other particles, but do not become airborne. Loosened silt and clay particles are carried in the wind stream and remain aloft until wind velocity decreases, then are deposited. During the 1930s, dust clouds from wind erosion in the Great Plains of the United States darkened skies east to Washington, DC. Tilling, to roughen the soil surface, temporarily stops the erosion process. Shelterbelts, comprised of trees planted across the prevailing wind direction, reduce wind velocity and soil movement for a distance as much as 20 times the tree height. If crop residues and standing stubble are left on the soil surface, as is the case with NT, this cover reduces wind movement of soil to negligible levels. This, in turn, reduces or eliminates the need for other erosion control measures.

	EQUIPMENT AND THE DEVELOPMENT OF NO-TILLAGE

TOP NOTES ABSTRACT INTRODUCTION HISTORY OF NO-TILLAGE TILLAGE AND CROP PRODUCTION... NO-TILLAGE AND SOIL EROSION EQUIPMENT AND THE DEVELOPMENT... NO-TILLAGE AND WEED CONTROL CROP RESPONSES TO NO-TILLAGE NO-TILLAGE AND CROP NUTRITION SOIL AND HYDROLOGIC RESPONSES... NO-TILLAGE AND FARM ECONOMICS THE FUTURE OF NO-TILLAGE REFERENCES

 
An important crop management consideration is planting at the proper time for the crop being produced and ensuring adequate stands. The seed must be deposited at the proper depth with good seed–soil contact and covered to reduce predation by wildlife and to ensure a dependable moisture supply as the seed initiates germination. Planters designed to function in loose, unconsolidated, tilled soil do not perform well in a firmer, mulch-covered, undisturbed soil environment. Effective planting equipment for untilled soil must have means to cut surface residue while avoiding hairpinning, or pushing residue into the slot, and enough weight to ensure penetration of the undisturbed soil. Openers create a slot in the soil to deposit seed. Since untilled soil does not flow, some means of pushing the soil to close the slot and cover the seed must be employed.

Successful crop establishment presented a challenge for early development of NT systems. No-tillage crop production progress and adoption was highly dependent on development of equipment, especially the NT planter and a well-calibrated sprayer. Moody et al. (1961) had graduate students use soil sampling tubes to plant individual hills of corn in sod—effective, but labor intensive. Triplett et al. (1963) constructed a planter using John Deere "Grassland Drill" openers. The knife openers were preceded by a rolling coulter to cut surface residue and provided good penetration of untilled soil. Their design included potential for fertilizer placement directly below the seed with wings on the side of the opener to loosen soil in the slot formed and separate seed from direct fertilizer contact. Even if no fertilizer was applied in the slot, seedling emergence was often reduced enough to require increased planting rate to assure an acceptable crop population. Improvements in currently available equipment include precise seed depth control and covering devices. Fertilizer application in or near the seed row is not considered essential except to boost early seedling growth.

	NO-TILLAGE AND WEED CONTROL

TOP NOTES ABSTRACT INTRODUCTION HISTORY OF NO-TILLAGE TILLAGE AND CROP PRODUCTION... NO-TILLAGE AND SOIL EROSION EQUIPMENT AND THE DEVELOPMENT... NO-TILLAGE AND WEED CONTROL CROP RESPONSES TO NO-TILLAGE NO-TILLAGE AND CROP NUTRITION SOIL AND HYDROLOGIC RESPONSES... NO-TILLAGE AND FARM ECONOMICS THE FUTURE OF NO-TILLAGE REFERENCES

 
Tillage was traditionally necessary for weed control on all soils and sites. A midwestern U.S. corn farmer might use a moldboard or chisel plow for primary tillage, either in late autumn or early spring. This was followed by one or more passes with a disk harrow to break clods and smooth the soil surface. Before planting, a harrow or field cultivator provided additional firming and smoothing. If the sequence was interrupted by rainfall, the finishing operation was repeated before planting. This would improve control of weed seedlings, including those germinating but not yet emerged. After planting, several passes with a cultivator disrupted weeds emerging between crop rows. For some passes, the cultivator was adjusted to throw soil into the crop row, burying, and thus destroying seedling weeds emerging in the noncultivated zone. Another weed control method was to use "check planters" that placed hills of corn seed 107 by 107 cm apart, which permitted cultivation passes at right angles to each other and often improved weed control. Timing of cultivation was critical. When rainfall during the postemergence period delayed cultivation, weed seedlings could develop too large to be easily controlled. Members of the farm family often had the chore of hoeing or pulling weeds missed by the cultivation.

No-tillage crop production, especially corn production, began in the 1960s and was made possible by the introduction of new, broad-spectrum herbicides. An herbicide program for NT weed control must meet several requirements (Table 3 ). The first requirement listed is unique to reduced and NT systems, because this was previously accomplished mechanically in tilled systems. The second requirement could be either through residual or postemergence application of herbicides with foliar activity. Controlling seedling weeds for 5 or 6 wk is usually adequate for corn and soybean, but as long as 10 to 12 wk may be required for cotton. After this time, competition from the crop helps suppress competition from most late germinating weed seedlings. Avoiding injury to the crop being grown could be through crop tolerance, or application techniques such as directed spray, wick applicators, or banding the herbicide. Cost is important but with multiple herbicides available for major crops, cost effective systems can usually be devised.

No-tillage practices and the continual use of some herbicide combinations have resulted in a change in the weed spectrum present in production areas (Swanton et al., 2006; Cardina et al., 2002). Weeds that escape a specific herbicide combination can increase to become a dominant problem. This was the case for fall panicum (Panicum dicotomiflorum Michx.) after only 3 yr of continuous atrazine use in NT corn (Triplett and Lytle, 1972). Other weeds that became more prevalent included poison ivy [Toxicodendron radicans (L.) Kuntze] and several woody species, plants that were ordinarily controlled with tillage. Biotypes of pigweed and lambsquarter (Amaranthus and Chenopodium sp.) tolerant to atrazine and simazine also developed and became competitive with the crop. The most recent problem with herbicide resistant biotypes is marestail (Conyza canadensis) and water hemp (Acnida altissima) resistant to glyphosate, especially in glyphosate-tolerant crops where other herbicides may not be applied (Feng et al., 2004; Scheiber et al., 2006). The solution to these problems includes proper selection of residual and postemergence herbicides and changing the herbicide program to include chemicals effective on the most problematic weeds. Crop rotation, for example, corn and a broadleaf crop, will permit selection of different herbicides to address specific weed problems. Dicamba and 2,4-D can be used in corn and effectively control water hemp, marestail, Amaranthus sp., and Chenopodium sp. Recent announcement of soybean germplasm with dicamba tolerance will provide a useful tool in dealing with problem weeds.

Development of crops tolerant to broad-spectrum contact herbicides, such as glyphosate and glufosinate (2-amino-4-(hydroxymethylphosphoryl)butanoic acid), have expanded the potential for NT crop production. For example, NT production of corn and soybean is now possible in swards comprised of warm-season perennial vegetation. Glyphosate-tolerant corn or soybean are planted in early spring while the perennial vegetation is dormant. Paraquat or glyphosate are applied preemergence to control cool season vegetation. As the crop emerges, the perennial vegetation begins to make spring growth. At 3 to 4 wk after planting, when the understory is green, glyphosate is applied to control or suppress perennial vegetation on the site. If necessary, a second application of glyphosate could be made to control escapes, and residual herbicides could be included in this system for control of annual species.

	CROP RESPONSES TO NO-TILLAGE

TOP NOTES ABSTRACT INTRODUCTION HISTORY OF NO-TILLAGE TILLAGE AND CROP PRODUCTION... NO-TILLAGE AND SOIL EROSION EQUIPMENT AND THE DEVELOPMENT... NO-TILLAGE AND WEED CONTROL CROP RESPONSES TO NO-TILLAGE NO-TILLAGE AND CROP NUTRITION SOIL AND HYDROLOGIC RESPONSES... NO-TILLAGE AND FARM ECONOMICS THE FUTURE OF NO-TILLAGE REFERENCES

 
Early reports of crop responses to plowed and NT culture in the United States represents a study in contrasts. While workers in Virgiania (Moody et al., 1961) and Kentucky (Blevins et al., 1971) were reporting improved productivity with NT, especially following sod crops, others in Iowa (Mock and Erbach, 1977) were reporting equal or reduced yields. Some of the very early work is suspect, however, because of poor stands and/or inadequate weed control. Satisfactory stands and weed control are necessary for performance of all tillage systems on all soils and sites. In Ohio (Van Doren et al., 1976; Dick and Van Doren, 1985; Dick et al., 1986a, 1986b), and later in Indiana (Griffith et al., 1988), workers published multiyear studies with common treatments on different soils and reported different responses to tillage. In these studies, a positive response to NT generally occurred on soils that developed under forest vegetation and had a comparatively low organic matter content, relatively poor structural stability, and did not crack extensively when dry. Many of these soils are in the Alfasol and Ultisol taxonomic classes. A recent extensive literature review (DeFelice et al., 2006) compared yields of corn and soybean in NT to conventional fall tillage systems in the United States and Canada. The United States average difference in soybean and corn yields between NT and conventional tillage was found to be negligible. No-tillage tended to have greater yields than conventional tillage in the south and west regions of the United States, similar yields in the central region, and lower yields in the northern United States and Canada. No-till yields were typically higher than conventional tillage yields on moderate- to well-drained soils, but slightly lower on poorly drained soils. No-tillage corn and soybean yields, as compared with conventional tillage yields, benefited more from crop rotation as compared with continuous cropping.

Tiarks (1977) investigated reasons for the yield decline associated with continuous NT corn on a Hoytville soil containing shrink–swell clay. These soils crack when they dry and the cracks occur at the same place each year, thus providing less resistance to root penetration than surrounding soil. Corn roots enter the crack zones and follow the cracks deeper into the soil. Pathogens, such as Pythium graminicola that infect corn roots, are present in the crack zone on roots and residues from the previous year and infect the roots of new corn plants entering these areas. Rotation with soybean reduces the disease inoculum and improves crop productivity. Primary tillage destroys continuity of the cracks that must form again during the following growing season. Even though cracks reestablish, following tillage there would be less root material from the previous crop year in the cracks, and thus less disease pressure. Yield of continuous corn, in a system that alternates tillage with NT, are similar to corn yields in a corn–soybean rotation with NT.

Triplett et al. (1973) recognized differences in crop response to NT on different soils and suggested a classification system for tillage, of Ohio soils, based on drainage characteristics. Better-drained soils, which were considered more suited for NT production, were primarily located in areas of sloping terrain where plow-based production can result in excessive soil loss. Although drainage is a factor in response to NT, clay content and the tendency of soils to form cracks when dry has also emerged as important, as noted above. Taxonomic descriptions of soils do not commonly feature their shrink–swell characteristics, except for Vertisols. Inclusion of this characteristic in soil descriptions could be useful in selecting management practices.

Morrison et al. (1990) describes a tillage system for Vertisol clay soils of the Texas Blackland Prairie. Crop production problems on these soils include a high potential for erosion, poor internal drainage, large clods created by primary tillage that require extensive weathering or multiple secondary operations to form a seedbed, and rapid drying due to secondary tillage leaving inadequate moisture for seeds to germinate. Initial attempts to use NT on these soils were not satisfactory. The system described by Morrison et al. (1990) consists of planting the crops on contour in one or more rows on wide beds with furrows between beds to minimize soil loss and provide surface drainage. Crops are rotated and choices include cotton, wheat, corn, and grain sorghum [Sorghum bicolor (L.) Moench]. Yields of NT crops were equal to or greater than tilled systems once the practices were in place and appropriate management determined.

More recently, zone or strip tillage systems have been developed that take advantage of the benefits of NT but help overcome yield limitations often associated with finer-textured, poorly drained soils and in colder climates on all types of soils (Vetsch and Randall, 2002; DeFelice et al., 2006). However, additional research is needed to develop such systems so that they consistently overcome the limitations of NT under these conditions.

Application of NT systems in low rainfall areas helps maintain or even increase crop yields (Peterson et al., 1993), while facilitating increased cropping intensity. Instead of crops grown every other year, they can be grown using NT in 2 of 3 yr or in 3 of 4 yr. As cropping intensity is increased, rainfall use efficiency can double and grain yield on an annualized basis can also approach a doubling compared with the tilled system (Peterson et al., 1993). Soil erosion can be reduced by 95% and, with greater amounts of residue returned, the trend of soil organic matter losses can be slowed or reversed. Wicks (1986) also points out that NT increases the potential for opportunity farming. In this system, soil moisture is measured in spring, and if enough has accumulated to support a crop, sorghum is planted using NT rather than continuing the fallow period. This system works because tillage is a drying operation but mulch-covered soil, planted using NT, conserves existing soil moisture supplies and improves crop emergence.

When changing from tilled to NT culture, particularly on noncracking soils, 3 yr may be required for the system to become fully functional. This was the case for Brown et al. (1985) and Stevens et al. (1992). Although neither author noted this in their papers, an inspection of their data shows improving yields with time. Griffith et al. (1988) reported NT yields improved with time on a poorly drained, Clermont soil (fine-silty, mixed, superactive, mesic Typic Glossaqualfs) with low organic matter content. By the fourth year of the study, NT yields were greater than moldboard plow treatment, which was attributed to improved soil physical characteristics. In another study, Triplett et al. (1996) compared yield of tilled treatments converted to NT with a long-term NT treatment. At the end of 3 yr, the NT treatments were within 90 to 95% of the long-term NT. Addition of mulch accelerates these processes (Triplett et al., 1996).

No-tillage and cover crops are currently being combined for production of organic NT vegetable crops. Weed suppression and marketable broccoli (Brassica oleracea L.) yield with NT were found to be equal to or higher than with conventional tillage (Infante and Morse, 1996). Weed control in such systems, obviously, has to rely on use of tools other than tillage and herbicides and most commonly this is through the judicious choice of a cover crop (Peachey et al., 2004). A table listing a wide variety of annual cover crops for NT vegetable production has been posted online by Schonbeck and Morse (2004).

With increasing pressure to harvest grain and cellulosic crops for production of biofuels, NT may be the best management option to maintain soil quality. However, even with NT, a cover crop may be required to provide adequate input of organic matter back to the soil. Cover crops not only introduce organic matter to the soil, they also prevent soil erosion, prevent NO₃–N contamination and P enrichment of water thereby safeguarding water quality, and aid in the reversal of C loss from the soil to the atmosphere. In Brazil, soil organic matter was higher under NT than conventional till soils and the use of legume cover crops with NT resulted in the highest amounts of soil organic matter accumulation (Amado et al., 2006). Work is progressing to develop cover crop systems that can be used with a wider range of crop and climate combinations than has traditionally been possible in the past. For example, a study was recently conducted on the use of winter cover crops with a corn–soybean rotation in Illinois (Villamil et al., 2006). Similarly, use of cover crops in Georgia for production of sorghum and cotton has been studied (Sainju et al., 2006). Where systems have been developed to kill the cover crop via winter frost, or other means such as a roller-crimper as is done in South America (Derpsch et al., 1991) or in Alabama (Ashford and Reeves, 2003), then the cover crops can also serve as an important component in the development of organic NT. The killed cover crop serves as a means of nonchemical weed control.

	NO-TILLAGE AND CROP NUTRITION

TOP NOTES ABSTRACT INTRODUCTION HISTORY OF NO-TILLAGE TILLAGE AND CROP PRODUCTION... NO-TILLAGE AND SOIL EROSION EQUIPMENT AND THE DEVELOPMENT... NO-TILLAGE AND WEED CONTROL CROP RESPONSES TO NO-TILLAGE NO-TILLAGE AND CROP NUTRITION SOIL AND HYDROLOGIC RESPONSES... NO-TILLAGE AND FARM ECONOMICS THE FUTURE OF NO-TILLAGE REFERENCES

 
In the early development of NT, a frequent question was, "If the soil is not tilled, how do you plow down fertilizer"? Fertilizer application commonly occurred either as a broadcast application before tillage or was knifed into the soil at planting with placement ideally 5 cm below and 5 cm to the side of the seed row. With tillage, the applied fertilizer is mixed with the soil, if not in the current crop year, before the next planting season. With NT, applied nutrients remain banded in the injection zone or on the soil surface, and this provides both challenges and opportunities for crop nutrition and environmentally sound management.

Soil sampling methods for nutrient status are still being evaluated for NT. Instead of a 20-cm soil layer sample, the top 1 to 2 cm of soil may most accurately reflect changes in surface pH that affect both nutrient and herbicide use and also nutrient accumulation from surface application and residue deposition. Soil analysis methods may also need to be recalibrated. Guertal et al. (1991) reported that Bray-1 extraction removed more P from surface NT soil than from tilled soil because of lower retention characteristics.

Phosphorus and K are relatively immobile and are partially fixed in slowly available or unavailable forms when mixed with soil. Increases in organic matter concentrations in the soil surface layer with NT can influence the nature of fixation and exchange sites in this zone for P and K (Karathanasis and Wells, 1990). Phosphorus fixation is also reduced with NT since application zones remain intact and can become saturated. Halvorson and Havlin (1992) reported equal uptake for surface applied or banded P in wheat culture. McGonigle and Miller (1993) reported increased early uptake of P in untilled soil, which was attributed to mycorrhizae colonizing roots of crop seedlings earlier, thus improving early uptake. Also, mycorrhizal networks in NT systems are not disrupted by tillage.

Tillage accelerates organic matter oxidation and release of nutrients contained in organic matter. During the initial years of NT, organic matter containing nutrient elements such as N and S accumulates in the surface soil layer. Thus, the nutrients in this accumulating soil organic matter are not as available for crop uptake and increased fertilizer application rates are often required. However, at some point, equilibrium between organic matter accumulation and oxidation occurs and the difference in fertilizer needs between tillage systems is less pronounced. In fact, because soil loss and loss of nutrients attached to soil particles is decreased with NT, the net effect will be increased efficiency of applied nutrients.

Crop response to N is clearly affected by tillage. Phillips et al. (1980) reported lower corn yield for NT with no applied N and higher yield at the maximum N rate, compared with N response to tilled corn. The explanation for this is less N released and greater water availability in the untilled soil, supporting higher maximum yield only at the high rates of N, when N is not limiting. As previously discussed, continuous maintenance of NT should even out or reverse the crop response to N between tilled and NT crop production systems. Nitrogen sources for NT are also important. Formulations containing urea, when surface applied, can sustain significant losses due to high urease concentrations (Fig. 2 ) (Dick, 1984), leading to ammonia volatilization. However, work with additives that stabilize surface-applied urea is promising. Solution forms of N and subsurface injection minimize losses. Ammonium nitrate can be broadcast on the soil surface without major danger of loss. Applicators for anhydrous ammonia in untilled soil are available and effective.

View larger version (26K): [in this window] [in a new window]   Fig. 2. Distribution of urease activity in soil profiles as affected by tillage intensity (Dick, 1984).

Sulfur deficiencies may occur in the seedling stage of early-planted corn. This is likely a function of reduced organic matter oxidation and release of S in the NT system. Application of S will correct the deficiency. No major problems with other minor elements have been reported to be associated with NT.

The mulch-covered NT soil surface retains moisture and facilitates crop root development at the mulch–soil surface interface (Triplett and Van Doren, 1969). If both roots and nutrients are concentrated together in the soil surface layer under the mulch, this provides for efficient uptake of nutrients. Only in extremely dry conditions when roots can no longer remain active, does the accumulation of organic and inorganic nutrients in the soil surface layer inhibit nutrient uptake by the crop. However, if nutrients need to be placed deeper into the soil, equipment designed to inject liquid, gas, or dry forms of fertilizer into untilled soil is available.

	SOIL AND HYDROLOGIC RESPONSES TO NO-TILLAGE

TOP NOTES ABSTRACT INTRODUCTION HISTORY OF NO-TILLAGE TILLAGE AND CROP PRODUCTION... NO-TILLAGE AND SOIL EROSION EQUIPMENT AND THE DEVELOPMENT... NO-TILLAGE AND WEED CONTROL CROP RESPONSES TO NO-TILLAGE NO-TILLAGE AND CROP NUTRITION SOIL AND HYDROLOGIC RESPONSES... NO-TILLAGE AND FARM ECONOMICS THE FUTURE OF NO-TILLAGE REFERENCES

 
The most visible effect of applying continuous NT is the rapid development of a mulch cover on the soil surface. Crops that produce less residues and more easily degraded residues, such as soybean, when grown in rotation with corn will result in a lower amount of mulch cover. If disturbance is avoided, the amount of mulch cover on the soil surface can be considered at equilibrium. However, even a slight disturbance, and one that may be considered to be an appropriate conservation tillage practice, can greatly decrease the amount of mulch cover and the length of time the soil remains covered.

With the passage of time, the continued addition and decay of residues enriches the surface soil layer with humified organic matter. The C in this organic matter is more resistant to decomposition than the residues from which it is derived. The distribution of the organic C is also changed from that in a plowed soil, specifically, there is a stratification that occurs (Table 4 ). It is not known how long it takes for a soil profile to reach a new equilibrium level of organic C concentration for a specific soil and climatic region if NT is continuously maintained. If soil is not tilled, plant roots and various natural soil processes continue to increase the levels of organic C from the surface of the soil downward.

Of all the plant nutrients, probably most affected by continuous application of NT is P, because it is relatively immobile. Fertilizer inputs remain where they are placed and for NT that often means on the soil surface. In addition, plants roots remove nutrients from the subsoil and deposit them on the soil surface. In our studies of soil P concentrations, we observed a strong interaction between tillage and soil type. Total P levels in soil for the PT and NT treatments for the Hoytville (fine, illitic, mesic Mollic Epiaqualfs) and Wooster (fine-loamy, mixed, active, mesic Oxyaquic Fragiudalfs) sites were similar (Table 5 ). However, extractable P was 7.4 times higher in the 0- to 7.5-cm soil layer under NT than PT in the Hoytville soil, a soil that strongly fixes P. In the Wooster soil, where P fixation is not as strong, there was a difference of only 3.6 times between NT and PT. Soil fertilizer recommendations must be adjusted to account for these changes. However, the stratification of P also impacts environmental quality. Phosphorous loadings into surface waters were traditionally associated with P attached to eroded sediments during high volume runoff events. Conservation tillage and specifically NT greatly reduced this loading. With time, however, a shift became evident with P loadings once again rising, this time associated with baseflow and tile drainage. The saturated P fixation sites at the soil surface released P into water that then exited the fields as surface flow or as preferential flow through macropores or cracks open to the tile drains. Fertilizer placement strategies thus need to be changed to take advantage of reduced P loadings associated with sediments while at the same time reducing P loadings due to increased solubilization caused by the high surface soil P concentrations. Subsurface injection of fertilizer nutrients is one potential strategy.

Early studies showed that mulched-covered NT soils reduced surface evaporation, maintained moisture near the soil surface at a higher level, and created a favorable environment for root development at or near the mulch–soil surface interface (Triplett and Van Doren, 1969). Blevins et al. (1971) reported less water use under mulch provided by a killed sod early in the growing season, compared with a tilled treatment. After the crop canopy developed, water use was similar for NT and tilled systems and reflected transpiration losses. Van Doren and Triplett (1969, 1973) used regression analysis to evaluate corn yield as a function of percentage of soil surface covered by mulch. On a noncracking soil, corn yield increased 34 kg ha^–1 for each percent increase in mulch cover.

A study designed to evaluate the mulch effect included NT bare (i.e., without mulch cover), NT with sheet metal strips driven into the soil to impound rainfall and prevent runoff, and NT with metal strips plus mulch cover (Triplett et al., 1968; Van Doren and Triplett, 1969). Preventing runoff during the early period increased grain yield by 470 kg ha^–1. Preventing runoff and having mulch cover increased yield by 1490 kg ha^–1 during the same period. The mulch also increased vegetative growth of plants, reflected in a greater leaf area index. Van Doren and Triplett (1973) also evaluated the mulch effect on crop productivity during seasons with adequate rainfall and/or irrigation and other years with less favorable precipitation amounts. During years with adequate rainfall, crop yields were greater with only small variation attributable to mulch or tillage treatment. During years with limited rainfall, overall yields were half to two-thirds those during favorable years and yields under NT bare (i.e., where mulch had been removed) was 30% less than NT with corn stalk mulch. Removing mulch and then cultivating before replacing the mulch improved crop productivity above that observed where NT practices had been strictly applied alone during seasons with limiting moisture. However, the NT experimental area had only been NT for 1 yr and macropores and soil structural stability may not yet have fully developed.

Paltineanu and Starr (2000) measured flow of rainfall down corn plants after canopy formation and infiltration into soil for NT and plow systems. They reported more rapid infiltration in and near the crop row in the NT system and improved utilization of small rainfall events. Real-time soil water dynamics data showed that the smaller rainfall events (<15 mm) resulted in a significant (P < 0.05) water infiltration advantage for the NT in-row position compared with the NT interrow positions and compared with the plow–tillage in-row position. Soil on the site was classified as an Ultisol with a silt loam texture containing 9% clay in the A_p horizon, almost certainly a noncracking soil.

Surface mulch decreases solar radiation directly reaching the soil surface and acts as an insulator decreasing heat loss at night. A higher soil moisture content also increases the energy needed to warm the soil. The net effect is less diurnal temperature variation for the mulch-covered surface. Effects of this are complex. In temperate zones with cool spring temperatures, early planted crops may emerge more slowly than crops planted into tilled, bare soil. As the growing season progresses, temperatures increase and are no longer limiting plant growth for either tilled or NT systems. In the tropics, where planting is at the onset of the rainy season, soil surface temperatures may reach 50°C and thus can damage emerging crop seedlings. Surface mulch protects the developing plants. In the northern wheat belt, small grain stubble in NT plantings traps snow and insulates winter wheat seedlings from cold temperature extremes. This has served to move the winter wheat belt further north, into the Canadian provinces.

	NO-TILLAGE AND FARM ECONOMICS

TOP NOTES ABSTRACT INTRODUCTION HISTORY OF NO-TILLAGE TILLAGE AND CROP PRODUCTION... NO-TILLAGE AND SOIL EROSION EQUIPMENT AND THE DEVELOPMENT... NO-TILLAGE AND WEED CONTROL CROP RESPONSES TO NO-TILLAGE NO-TILLAGE AND CROP NUTRITION SOIL AND HYDROLOGIC RESPONSES... NO-TILLAGE AND FARM ECONOMICS THE FUTURE OF NO-TILLAGE REFERENCES

 
The demand for frequent tillage operations during critical periods of crop establishment and early development limited the area a farm family could manage. In the Corn Belt of the United States, farms of 30 to 50 ha were common with 8 to 12 ha devoted to corn. Cotton production was even more labor-intensive with 300 to 370 h of human labor required per hectare to prepare a seedbed, plant, weed, and harvest the crop. A farm family could only handle from 4 to 6 ha of cotton. For corn producers, a rotation with grain following a legume (N source) in a 3- to 4-yr sequence was almost universal. When draft animals were used for primary tillage, a team pulling a moldboard plow could cover only 1.2 to 1.6 ha d^–1. As tractors became available and more widely used, time required for individual tillage operations was reduced. Although this expanded the area that could be handled by a farm family, the number of operations remained essentially the same. The first widely used herbicide, 2,4-D, controlled many troublesome broadleaf weed species with postemergence applications. This decreased the need for hand labor and allowed reduction in the number of cultivations.

Increased farm size with reduced need for labor has helped maintain the tradition of the family farms in the United States. However, assessing the economics of a farming system, especially NT systems, is not always straightforward. Partial budgeting is a common approach used to compare economics of NT with tilled production systems. With this method, purchased inputs for NT (seed, fertilizer, pesticides) are usually greater than for tilled production while labor and equipment costs (fewer operations, less equipment investment) are lower. Total costs are often similar for the two systems and crop yield drives profitability. The amount that gross income exceeds stated costs is defined as return to land, labor, and management and is usually compared on a per-hectare basis. Assumptions common in partial budgeting include labor at a specified rate per hour, labor is considered neither limiting nor slack, and fixed costs of equipment are spread over a specified area. Crosson et al. (1986) recognized that less labor was required for NT than conventional crop production. Potential savings in equipment cost were also not thoroughly addressed in much of the earlier economic analyses. Planting and spraying are low draft, rapid operations that require smaller, potentially less expensive power units than required for primary tillage of cropped areas of equal size. Anecdotal evidence suggests that equipment life is extended because of fewer hours of use and lower draft requirements. Thus, the fixed costs for equipment will be reduced on an annual basis.

Comparing tillage systems based on costs derived through partial budgeting may not provide a true evaluation of the systems. Generally, as labor costs increase, returns became relatively more favorable for the NT system. This is because production of various crops is characterized by intense activity during planting and harvest periods with little or no time required otherwise. Hiring skilled labor only during periods of peak demand is often not an option. The optimum season for planting corn and soybean includes 3 or 4 wk with some overlap. As the season is extended and planting is delayed, crop productivity decreases. Delayed harvest reduces productivity through shattered seed, decreased quality, and feeding of insects and wildlife. In humid areas, precipitation during planting season may limit fieldwork to 3 or 4 d wk^–1 for tilled production. Seedbed finishing operations before planting utilize labor and limit crop area individual workers can handle on a timely basis. Sloping fields in upland areas where primary tillage is delayed until spring because of erosion potential further limits worker productivity. Fortunately, NT is generally well adapted to soils on upland sites and crop productivity is often greater than for tilled systems. Planting NT fields is possible when soil will support equipment for ground operations and this occurs earlier in the spring season and sooner following rainfall events because the firm, untilled soil resists compaction and facilitates traffic. While some farmers may enjoy more leisure with time saved by adopting NT, as suggested by Crosson et al. (1986), others expand operations to plant additional area. Expanded crop production could be on land purchased, or rented, or through more intense cropping of land considered marginal because of erosion potential with tilled production systems.

Triplett et al. (2002) compared tilled and NT production in a whole farm economic analysis. Inputs included crop yields from tilled and NT systems on a highly erodible loess soil unsuited to fall or winter tillage for warm-season crop production. Equations for different size land areas were solved for crop selection and operations, tilled or NT, that provided maximum economic return. Labor was considered a finite resource with operator labor utilized initially and any additional labor required was hired on an annual basis. Cropland remaining idle or enrolled in government programs was an option if additional labor was not profitable. All solutions selected NT as most profitable with the site and soil constraints given above. An alternative solution for tilled production was generated to compare different tillage systems. A producer using NT could tend crops on >400 ha without hiring additional help, whereas, with a tilled system, the producer could handle only 320 ha. At 320 ha, the per-hectare net was 1.83 times greater for NT than a tilled system consisting of a crop mix of corn and soybean. At 400 ha, the net for a NT system that included a corn, soybean, wheat–soybean double crop system was 2.2 times greater.

Chase and Duffy (1991) evaluated returns from continuous corn and a corn–soy rotation comparing four tillage systems on a Mollisol in eastern Iowa. They reported that yield stability was no different for moldboard plow and conservation systems over a 10-yr period. Returns for NT were less than moldboard plowing for continuous corn but were more favorable for a corn–soybean rotation, reflecting improved corn yield with rotation in the NT system. This yield pattern is similar to results from Indiana (Griffith et al., 1988) and Ohio (Dick et al., 1991) for heavier soils. Hussain et al. (2005) compared tilled and NT cotton yields from a highly erodible loess soil in northern Mississippi in a risk analysis with 25- to 100-yr planning horizons. No-tillage cotton yields were greater than tilled systems and as depth of soil above a fragipan was reduced by erosion in the tilled system, productivity was further decreased. The coefficient of variability (CV) was lower for NT than tilled systems. Thus, risk was less for the NT system and was more sustainable than the tilled system. Featherstone et al. (1991) evaluated crop yields from 78 farmer sites in Wabash County, Indiana. Data were analyzed with a simulation model, regression, and partial budgeting. When rainfall differences, soils, and moisture stress between sites were considered, there were few differences in productivity influenced by tillage systems. The study also provided empirical evidence that, as moisture stress increased, net returns to those corn producers using NT systems increased over those obtained for other tillage systems.

For sites where NT yields are greater than tilled, NT production reduces soil loss and makes more profitable crop selection possible, or NT qualifies the producer for government payments and still does not decrease productivity, the NT choice is obvious. For sites where fall or winter tillage are common and crop yields are equal or slightly less with NT, increased worker productivity and machine efficiency may still make NT a preferred choice.

	THE FUTURE OF NO-TILLAGE

TOP NOTES ABSTRACT INTRODUCTION HISTORY OF NO-TILLAGE TILLAGE AND CROP PRODUCTION... NO-TILLAGE AND SOIL EROSION EQUIPMENT AND THE DEVELOPMENT... NO-TILLAGE AND WEED CONTROL CROP RESPONSES TO NO-TILLAGE NO-TILLAGE AND CROP NUTRITION SOIL AND HYDROLOGIC RESPONSES... NO-TILLAGE AND FARM ECONOMICS THE FUTURE OF NO-TILLAGE REFERENCES

 
Responding to Changing Conditions to Solve Problems
Modern agriculture depends heavily on the use of gasoline and diesel fuel in tractors for plowing, planting, cultivating, and harvesting. Irrigation pumps use diesel fuel, natural gas, and coal-fired electricity. Natural gas is used to synthesize ammonia, the basic building block in N fertilizers. Phosphate and potash fertilizer production is also energy-intensive as the mining, manufacture, and international transport of phosphates and potash all depend on oil. In the United States, for which reliable historical data are available, the combined use of gasoline and diesel fuel in agriculture has fallen from its historical high of 29 billion L in 1973 to 17 billion in 2002, a decline of about 40% (Brown, 2006). For a broad sense of the fuel efficiency trend in U.S. agriculture, the liters of fuel used per megagram of grain produced dropped from 138 in 1973 to 54 in 2002, an impressive decrease of approximately 60%. One reason for this was a shift to minimum and NT cultural practices on roughly two-fifths of U.S. cropland (Brown, 2006).

Long-term use of NT should be encouraged (Dabney et al., 2004; Grandy et al., 2006). The many benefits of NT, such as erosion resistance, is due to both residue cover and improved soil quality factors. However, the erosion-resisting soil quality factors, developed over several years of NT management, may be lost within a single year of fallow management. If NT fields must occasionally be tilled, and this practice should be discouraged as much as possible, these fields should be returned to NT management as quickly as possible.

An increase in commodity prices is currently occurring because of the demand for agricultural stocks to support biofuel production. Producer response will be expanded production by increasing cropped area. Land not now in crop production may have lower production potential than land currently cropped, be located in small, irregular fields, or on slopes with unacceptable erosion potential with tilled cropping. Much of this uncropped area is covered with permanent vegetation and may have been retired from production by enrolling in the Conservation Reserve or other programs. No-tillage provides an opportunity to rapidly expand production while protecting soil against erosion. Desirable soil conditions formed under permanent vegetation, increased organic matter and stable macropores, will be retained with NT production.

There is also a long-term trend toward increased agricultural worker productivity. Larger equipment, fewer operations for soil preparation, less cultivation, and increased use of herbicides have all contributed to this trend. Larger tracts of land are farmed with fewer workers. No-tillage farming has accelerated this trend by further reducing operations used for crop establishment and will continue to do so. No-tillage improves harvest efficiency by providing better traffic support during wet harvest seasons. However, occasional tillage may be necessary to smooth ruts created by harvest operations.

Weeds that escape the action of specific herbicides will increase and they will compete with the crop. For example, fall panicum in corn can escape control by some triazine herbicides. Biotypes of weeds resistant to certain herbicides can also develop and Amaranthus and Chenopodium sp., resistance to triazines, and a currently expanding population of Conyza sp. and Alcnida tolerant to glyphosate are evidence. These problems can be managed with rotation of crops and herbicides. Recent development of crops with tolerance to multiple herbicides, such as glyphosate plus glufosinate and the recent announcement of a soybean cultivar tolerant to both glyphosate and dicamba will improve control options. Control of other pests such as slugs and disease pathogens may also be more difficult under NT than where tillage is practiced. New problems will continue to challenge researchers so that the benefits of NT can be realized on an expanding amount of land worldwide.

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	REFERENCES

TOP NOTES ABSTRACT INTRODUCTION HISTORY OF NO-TILLAGE TILLAGE AND CROP PRODUCTION... NO-TILLAGE AND SOIL EROSION EQUIPMENT AND THE DEVELOPMENT... NO-TILLAGE AND WEED CONTROL CROP RESPONSES TO NO-TILLAGE NO-TILLAGE AND CROP NUTRITION SOIL AND HYDROLOGIC RESPONSES... NO-TILLAGE AND FARM ECONOMICS THE FUTURE OF NO-TILLAGE REFERENCES

 

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