No-till is a way of growing crops without plowing. There is no soil disturbance and fields retain a good cover of living or decaying plant material throughout the year. This protects against erosion and encourages a healthy, well-structured soil for growing crops. The system is also known as zero-tillage or direct drilling and is one of a number of crop production practices that are included in the overall concept of conservation tillage.
There are many benefits that result from creating and maintaining a healthy soil. The global demand for food is forecast to double by 2050 and many more people will want to eat meat. Food energy in beef, for example, requires up to eight times more cropland than an equivalent vegetarian diet. So, more than ever, the pressure is on to increase agricultural productivity and to use land wisely. Protecting the soil is essential for sustainable agricultural production.
Weed control is a fundamental issue in no-till because weeds are not buried by plowing. Although various weed control practices are used in no-till, including the use of cover crops, non-selective herbicides such as paraquat play a key role in an integrated approach to weed management.
This article covers what no-till is, where it is successfully being employed, its benefits and the role of paraquat.
Conservation tillage systems
The place of no-till amongst other tillage systems is described here
Soil-type and condition often dictate whether no-till can be readily adopted. However, with preparation and commitment (e.g. control of problem weeds, adequate drainage) the system can be used successfully in a wide variety of situations. The key objectives of all conservation tillage systems are to minimize the number of passes over the field and to maximize the amount and duration of vegetative cover of the soil.
Crop remains play an essential role in maintaining or improving soil quality. Stubble and straw, which is best chopped and spread evenly over the field, guard against erosion by wind and rain, provide a habitat for wildlife and ultimately help to maintain soil organic matter levels, as do crop roots.
No-Till Benefits
The many benefits of no-till are listed in Table 1 below. There are practical solutions to the few problems sometimes encountered, but skill and appreciation of the soil’s needs are vital to successful no-till. Examples of how these benefits are being achieved in no-till systems using paraquat are given in the final section of this article.
Table 1. Summary of benefits and problems usually associated with no-till.
| Factor | Benefits | Problems |
|---|---|---|
| Soil |
Straw and other unharvested plant materials reduce erosion by wind and water. Organic matter accumulates to provide structure and nutrients. |
Causes lower soil temperatures in spring. Strip-till (clearance of a narrow strip along crop rows during planting) provides a solution. |
| Water |
Good structure allows better retention and drainage of excess. |
Slow spring growth in colder soils in more marginal areas and possible yield reductions. Strip-till avoids the problem (see above). |
| Biodiversity |
Habitats for flora, fauna and microorganisms on and in soil. |
Occasionally disease fungi are encouraged. |
| Crop |
Good environment for root growth and supply of nutrients. Better drought tolerance. Less susceptible to waterlogging. |
|
| Energy |
Reduced use of fuel. |
|
| Climate |
Reduced emissions from fewer farm operations. Carbon sequestration in organic |
Possible increase in nitrous oxide emissions if soil structure is not good and soil is waterlogged. |
|
Farm economics |
Lower costs in fuel and machinery, greater profitability. |
The impact that no-till can have on greenhouse gas emissions has been of particular interest recently. Around 20% of all greenhouse gas emissions, including most methane and nitrous oxide come from agriculture and the burning of unwanted wood from deforestation.2
No-till systems use much less fuel, which will obviously reduce emissions. However, this is a relatively small effect compared to the enhanced potential of no-till soils to sequester carbon in organic matter.
In Europe (the continent, excluding the former USSR), it has been estimated that if all cropland were to be no-tilled, there would be potential to sequester more than 150 million tonnes of carbon dioxide per annum.3 In addition, savings in diesel fuel consumption would reduce emissions of carbon dioxide by nearly 12 million tonnes every year. To put this into perspective, a family car typically emits about 4 tonnes of carbon dioxide in a year’s travel.
A breakdown of fuel use under various cultivation systems in Illinois (USA) showed that, although some gains from lower fuel use under no-till are clawed-back by more fuel used to plant and spray, no-tilling corn used 14% less fuel, and no-tilling soybeans used 49% less fuel.4
Table 2. Fuel used in growing corn and soybeans in Illinois under conventional and no-till systems.4
| Operation |
Diesel Fuel Use (US gallons/acre) |
|||
| Corn | Soybeans | |||
| Conventional |
No-Till |
Conventional |
No-Till |
|
| Cultivate |
0.7 |
0.0 | 2.4 |
0.0 |
| Plant |
0.4 |
0.5 |
0.4 |
0.5 |
| Spray | 0.3 |
0.5 |
0.3 |
0.5 |
| Fertilize |
0.8 |
0.7 |
0.2 |
0.2 |
| Combine |
1.5 |
1.5 |
1.0 |
1.0 |
| Total | 3.7 | 3.2 | 4.3 |
2.2 |
Adoption of no-till systems
The first experiments on no-till systems started to be conducted in the US in the late 1940s. However, it was not until the 1960s when paraquat became available that adoption by farmers really began. A decade later, no-till started to be practised in Brazil, spreading to Argentina, Paraguay and Uruguay, in particular.5
Fastest adoption rates have been in S. America, where in some regions more than 70% of fields are permanently no-tilled. Over the past 20 years, global rates of adoption have been estimated as growing by about 6 million hectares each year.6
The main barriers to adoption are:
- Lack of knowledge
- Cultural preferences for traditional methods
- Lack of suitable machinery
- Problems with weed control
The most recent estimates put the world area of cropland under no-till at around 120 million ha. Leading countries are USA, Brazil, Argentina, Canada, Australia and Paraguay. The area in Asia where non-till is practised, mainly on smallholder farms of a few hectares or less, is far greater than in Europe. In Africa, the no-till area remains very small.
In the US in 2009, the no-till area was believed to be about 88 million ha (35 million acres). This figure comprised 50% of all soybean crops, 30% of corn, 24% of cotton and 16% of rice.7
The 2007 US Farm Bill Theme Paper on Agriculture and Energy8 stated:
“There is a significant opportunity to realize immediate economic and environmental gains through energy conservation activities ... The measures include: doubling of no-till acreage (from 25 to 50 million hectares), saving 821 million liters of diesel fuel (217 million gallons) and $500 million each year …”
Advantages of paraquat
In no-till, weeds are not controlled by plowing, so its success relies on the use of non-selective herbicides like paraquat. Paraquat is the best choice when fast action and rainfastness are needed.
Paraquat has no soil residual activity because it is deactivated by extremely strong adsorption immediately on contact with soil. New flushes of germination are, therefore, unaffected. A naturally regenerated and managed weed flora provides a vegetative cover to the soil performing a similar function to crop remains spread over the field.
Paraquat also contributes to minimizing soil erosion by only destroying shoot growth. Roots are left intact and provide an anchoring effect.
Many field experiments have shown how using no-till and paraquat can markedly reduce soil erosion.
In addition, paraquat is an essential component when rotating herbicides to avoid weed resistance
References
- Conservation Technology Information Center
- Venterea, R T, et al. (2005). Nitrogen oxide and methane emissions under varying tillage and fertilizer management. Journal of Environmental Quality, 34, 1467-1477
- Smith, P et al. (1998). Preliminary estimates of the potential for carbon mitigation in European soils through no-till farming. Global Change Biology, 4, 679-685
- University of Illinois (2006). Farmdoc Newsletter, April 19 2006
- Huggins, D R & Reganold, J P. No-till: the quiet revolution. Scientific American, July 2008, pp 70-77
- Derpsch, R, et al. (2010). Current status of adoption of no-till farming in the world and some of its main benefits. International Journal of Agricultural and Biological Engineering, 3, (1), 1-26
- Horowitz, J et al. (2010). No-till farming Is a growing practice. USDA ERS Economic Information Bulletin No. (EIB-70) 28 pp, November 2010
- USDA (2006). Energy and Agriculture. 2007 Farm Bill Theme Paper