Conservation Tillage

Compiled by:
Beat Stauffer (seecon international gmbh), Nina Carle (seecon international gmbh), Dorothee Spuhler (seecon international gmbh)

Executive Summary

The adaption of tillage techniques helps improve soil conditions. Less tilling, lesser tillage depth, or no tillage at all has directly positive effects on the agricultural site. Stubbles help protect the soil from splash erosion and crusting through raindrops. The more crop residues are left on the field, the more nutrients stay in the soil. Sometimes less tillage requires higher amounts of herbicides, because plant competitors grow better. The costs for reduce tillage are small, but in some cases costs for herbicides are consequently higher.

Introduction

Through adapted tillage techniques, moisture loss in the soil can be reduced and soil quality and agricultural production can be improved. Thus, water use for irrigation can be decreased and the local water cycle is optimised. Soil moisture loss (and also soil degradation) can be minimised through different techniques of soil moisture conservation: soil cover and reforestation, mulching, soil amendments and different tillage techniques.

Soil tillage comprises all the physical, mechanical, chemical or biological actions conducted to prepare the seedbed for seed germination, emergence and establishment, root development (the amount of soil water available to plants is governed by the depth of soil that roots can explore (the root zone) and the nature of the soil material) and crop growth (INFONET BIOVISION 2011; BETTER SOILS n.y.). Conservation tillage limits the devastating consequences of drought, conserves soil moisture (thus decreasing water use for irrigation) and some techniques even enhance the local nutrient cycle (e.g. mulch tillage)(UNEP 1998; FRANZEN 1997).

Importance of Tillage for Conserving Soil Moisture

  BETTER SOILS (n.y.)

Stages of water holding capacity. Source: BETTER SOILS (n.y.) 

When soil is saturated, all the pores are full of water, but after a day, all gravitational water drains out, leaving the soil at field capacity. Plants then draw water out of the capillary pores, readily at first and then with greater difficulty, until no more can be withdrawn and the only water left is in the micro-pores. The soil is then at wilting point and without water additions, plants will die (BETTER SOILS n.y.).

The amount of soil water available to plants is governed by the depth of soil that roots can explore (the root zone) and the nature of the soil material. Because the total and available moisture storage capacities are linked to porosity, the particle sizes (texture) and the arrangement of particles (structure) are the critical factors. Organic matter, carbonate levels, and stone content also affect moisture storage. Poor structure, low organic matter, low carbonate content and presence of stones all reduce the moisture storage capacity of a given texture class. Clays store large amounts of water, but because they have high wilting points, they need significant rain to be able to supply water to plants. On the other hand, sands have limited water storage capacity, but because most of it is available, plants can make use of light showers regardless of how dry they are before the shower. Plants growing in sand generally have a denser root system to enable them to access water quickly before the sand dries out (BETTER SOILS n.y.) (read also the paragraph “Soil Texture” in the crop selection factsheet).

Texture

Field Capacity

Wilting point

Available water

Coarse Sand

0.6

0.2

0.4

Fine sand

1.0

0.4

0.6

Loamy sand

1.4

0.6

0.8

Sandy loam

2.0

0.8

1.2

Light sandy clay loam

2.3

1.0

1.3

Loam

2.7

1.2

1.5

Sandy clay loam

2.8

1.3

1.5

Clay loam

3.2

1.4

1.8

Clay

4.0

2.5

1.5

Self-mulching clay

4.5

2.5

2.0

Water holding capacity (mm/cm depth of soil) of main texture groups. Figures are averages and vary with structure and organic matter differences. BETTER SOILS (n.y.)

Tillage Techniques

(Adapted from UNEP 1998)

Strip Cropping

Strip cropping is the farming of sloping land in alternate, contoured strips of inter-tilled row crops and close growing grasses (or other ground cover crop), aligned at right angles to the direction of natural flow of runoff. The close-growing strips slow down runoff and filter out soil washed from the land in the inter-tilled row. This control of runoff also allows increased opportunity for infiltration of the runoff and, thus, increased moisture in the soil. The strip widths can be varied depending on the soil type and slope.

Contour Farming

Contour farming involves aligning plant rows and tillage lines at right angles to the normal flow of runoff. It creates detention storage within the soil surface horizon and slows down the rate of runoff, thus giving the water the time to infiltrate into the soil. The contour bunds are earth banks 1.5 to 2.0 m wide, forming buffer strips at 10 to 20 m intervals, and are important for the functioning of the technology. The effectiveness of contour farming for water and soil conservation depends on the design of the systems, but also on soil, climate, slope aspect and land use of the individual fields.

Zero or Chemical Tillage

In this approach, the land is not tilled at all. Chemical tillage uses herbicides to control weeds, avoiding the need to till the soil. This tillage technique conserves water in the soil profile since the soil is not tilled and exposed to the drying (evaporative) elements of the atmosphere. The moisture is retained within the soil profile. The new crop is generally planted directly into the stubble of the previous crop.

Mulch Tillage

Mulch tilling involves covering bare soil with mulch or plant litter to prevent or reduce the evaporation of soil moisture and minimise the erosive energies of rain falling directly onto soil particles. Mulching is different from soil amendment.The mulch is usually crop residue such as maize stove, sorghum trash and wheat straw. In cases where these are not available, or are eaten up by animals, gravel can be used as mulch.

Reduced or Minimum Tillage

  Planting stick or machete can be used to create holes to plant the seed in an un-ploughed field with stubble/crop residue. The cut hardwood stick from the bush is sharpened at one end and used to make planting holes. The holes are made in lines at evenly spaced intervals that make it easier to weed and apply fertiliser or manure. Source INFONET BIOVISION (2011)

Dibble stick planting. Source: INFONET BIOVISION (2011) 

Reduced tillage is a practise in which the soil is tilled to some extent but not completely inverted. There are several ways of achieving reduced tillage. For example, the plough can be supplemented with discs or a chisel harrow, and the land ploughed in narrow strips, coinciding with the spacing of the row crops, leaving the intervening space untilled. Reduced tillage means a smaller volume of soil is exposed to erosion and moisture loss by evaporation; hence, conserving moisture.

One technique of reduced tillage is called dibble stick planting, where a planting stick or machete can be used to create holes to plant the seed in an un-ploughed field with stubble/crop residue. The cut hardwood stick from the bush is sharpened at one end and used to make planting holes. The holes are made in lines at evenly spaced intervals that make it easier to weed and apply fertiliser or manure.

No-till and Soil Cover

No-tillage is generally defined as planting crops into soil that has remained untilled after the harvest of the previous crop. Conservation tillage includes the WHEN and HOW this tillage is done. The "when" basically refers to the moisture-state of the soil. Conservation tillage takes into account both environmental and tillage factors.This system involves opening a narrow slot only wide and deep enough to obtain proper seed coverage and with at least 30% mulch cover. Permanent, continuous no-tillage should follow, while the soil should remain covered by crop residues or green manure cover crops. Crop residues should remain undisturbed on the soil surface after seeding. Read more about it in INFONET BIOVISION (2011).

Seasonal Influences

The greatest moisture loss is usually experienced during the first tillage trip on the field. However, additional trips result in additional drying in the tillage zone. Moisture loss from tillage is especially high during dry springs, when the seedbed can dry. Spring tillage should be shallow only to limit moisture loss. Conserving spring moisture to allow seed germination is especially difficult with small seeded crops like canola and in dry, windy conditions. Use of a packer or harrow to fill in and seal the ground during the tillage operation may be important.

Fall tillage influences the amount of snow catch, which is important in many years to help recharge soil moisture after a previously dry summer and fall. Snow catch is influenced by surface roughness, but mostly by stubble height. Conservation tillage, and especially no-till, increases the amount of stubble left on the surface.

Operation and Maintenance

There are limited operation and maintenance needs associated with these technologies. Maintenance involves keeping the structures in a functional state, e.g., maintaining the contour bunds to prevent erosive runoff of stormwaters, or maintaining the grass strips to retain their functionality. When mechanised ploughing is carried out, equipment maintenance is important in order to ensure the correct depth of penetration of the ploughs, seed injecting devices and other cultivating equipment. Generally, conservation farming requires equipment modifications relative to conventional farming techniques, and may require some initial capital investment to replace unsuitable machinery, although conservation tillage may be done using more traditional, manual farming methods (adapted from UNEP 1998).

Recommendations

(Adapted from FRANZEN 1997)

  • Consider adoption of no-till farming. In many cases, adoption of no-till does not require purchase of expensive equipment, but some modification of equipment is likely.
  • Use tillage implements that retain crop residues, leave a rough soil surface and limit soil drying, such as undercutters, harrows and sweep style cultivators.
  • Avoid tillage with implements that bury more than 50% of crop residues, such as discs with greater than 60 cm diameters, and mouldboard plows.
  • Limit tillage trips.
  • Perform tillage at right angles to the prevailing winds (usually north and south with a west prevailing wind).
  • Follow the contour of the land in hilly landscapes to intercept water in the event of heavy rainfall.
  • Control weeds through herbicides rather than tillage.

Soil Compaction

Heavy vehicles can lead to soil compaction and reduce water infiltration by reducing the soil pore volume. Consequently oxygen and water are squeezed out and can hardly infiltrate again (WIKIPEDIA 2011). The four key principles to prevent it are (FAO 2003):

  1. Reduced or zero tillage
  2. Controlled traffic
  3. Permanent soil cover
  4. Rotations and cover crops
  5. Costs Considerations

For minimum tillage, labour and operation cost are about $40/ha. For zero tillage, the costs are a function of the cost of chemicals and work out at about $120/ha (Zimbabwe). In general terms, the methods are cheaper than conventional tillage due to the reduced demand for ploughing, but are subject to some opportunity costs at the time of conversion from conventional tillage (UNEP 1998).

At a Glance

Working Principle

A reduction of tilling or the adoption of no-till farming combined with plant residues on the field surface (soil cover or mulch) helps improve the soil texture. Different tilling methods have different advantages for the farmer’s purpose.

Capacity/Adequacy

A decreasing frequency and depth of tilling has a huge potential to enlarge the capacity of production of the field.

Performance

Easy to perform, but requires knowledge.

Costs

Besides the costs for herbicides, tillage adaption requires only little financial investment, but investment in know-how.

Self-help Compatibility

The self-help-compatibility is high; already the crop residue improves the soil conditions.

O&M

Regularly no till or less deep till combined with plant residues on the field.

Reliability

Scientifically investigated tool to lower the loss of soil moisture, and to improve soil fertility.

Main strength

Sustainable approach to improve soil conditions.

Main weakness

Use of herbicides often necessary.

Applicability

Adapting tillage techniques is a very helpful tool to lower soil moisture loss through evaporation. It is applicable for small and large agricultural areas. For no-till, it has to be considered that herbicide use may be required.

Conservation tillage and reduced tillage are suitable under most conditions, provided other factors, like slope and rainfall intensity, are taken into account in the practices. Mulch tillage, soil cover, and soil amendment are suitable under most conditions. Strip cropping is effective on well-drained soils on slopes of 6 to 15%. Contour farming is suitable on slopes of between 3% and 8%. These methods also enhance soil structure, nutrient status and reduce soil erosion (e.g. through rain drops or wind). Unfortunately, the grass strips and mulching, if not properly applied, can harbour pests and vermin that can destroy crops; hence, conservation tillage is usually implemented as part of an integrated nutrient and pest management strategy. Chemical tillage is suitable on most soils and slopes, and is especially suitable for use on hydromorphic soils with poor internal drainage. Chemicals used under zero tillage can be harmful to the environment (UNEP 1998).

Advantages

  • Quick and easy way to improve moisture loss of soil
  • Greater water holding capacity of the soil
  • Greater nutrient capacity of the soil
  • Lesser loss of water evaporation
  • Lesser crusting of soil surface through splash effects of raindrops
  • Optimised tillage helps to conserve to soil moisture
  • Optimised tillage helps to conserve to soil moisture. Mulch tillage, soil cover, mulching, soil amendment and strip cropping additionally protect the soil from erosion through raindrops and wind. Moreover, infiltration is improved, protecting the soil from runoff erosion and enhancing the soils capacity to store moisture
  • Contour farming is effective in soil loss control, yielding up to a 50% reduction in erosion. Chemical tillage or zero tillage saves energy and time

Disadvantages

  • May require the use of herbicides
  • Requires some basic knowledge of soil treatment
  • May require some investment for agriculture equipment
  • No-till, conservation tillage and reduced tillage can result in the deterioration of soil condition over time, if it is not used in conjunction with other rotational practices
  • Mulch tillage, soil cover and strip farming can create conditions that harbour pests, diseases and vermin that can destroy crops if not managed correctly
  • Contour farming results in less benefit to compacted or poorly permeable soils because these soils become saturated quickly. This can prove harmful to certain crops. On steep slopes, contouring alone can be deleterious, since water concentrating in the furrows may breach the bunds and cause even more erosion
  • Chemical tillage or zero tillage requires significant inputs of chemical herbicides, which can have quite high costs. Moreover, the chemicals can cause considerable harm the environment. Zero tillage needs to be used in rotation with other techniques

References Library

BETTER SOILS (Editor) (n.y.): Soil Water Holding Capacity. South Australia: The Agricultural Bureau of South Australia. URL [Accessed: 01.05.2012].

FAO (Editor) (2003): Soil Compaction: An unnecessary form of land degradation. Rome: Food and Agriculture Organization (FAO). URL [Accessed: 01.05.2012]. PDF

FRANZEN, D. (1997): Tillage Techniques That Can Save Moisture. Fargo: North Dakota State University.

INFONET BIOVISION (Editor) (2010): Conservation Tillage Systems. Zuerich: Biovision. URL [Accessed: 19.06.2012].

UNEP (Editor) (1998): Sourcebook of Alternative Technologies for Freshwater Augmentations in Africa. Conservation Tillage. Water Conservation. Harare: Institute of Agricultural Engineering. URL [Accessed: 14.02.2012].

WIKIPEDIA (Editor) (2012): Soil Compaction. URL [Accessed: 14.02.2012].

Further Readings Library

Reference icon

FAO (Editor) (1993): Soil tillage in Africa. Rome: Food and Agriculture Organization (FAO). URL [Accessed: 01.05.2012].

In 1991, a training course on tillage and residue management in Africa was held in Nigeria to give participants the opportunity to discuss technologies of tillage practices in the various countries, update their knowledge on the subject and provide them with the basic principles on which to develop appropriate tillage and residue management packages for the specific soils in their countries. It was hoped that the course would give the participants a firm foundation and would stimulate the beginning of programmes for sustainable agricultural production. The background material from the course has been consolidated into this online publication, as it is felt that other readers may well benefit from the experiences presented at the training course.


Reference icon

FAO (Editor) (2003): On-Farm Trials for Adapting and Adopting Good Agricultural Practices. Suitable Methods of Tillage for the Farm. Rome: Food and Agriculture Organization (FAO) . URL [Accessed: 01.03.2012].

These online guidelines work upon: increasing understanding of the local environment and how it, the crop and other yield-determining factors interact; improving management of cropping systems and thus, sustainable yield; and increasing crop diversification. They are not a set of static rules; on the contrary, they encourage modifications in order to address local needs and circumstances after a cycle of learning, thought and discussion among all collaborators.


Reference icon

FAO (Editor) (2003): Soil Compaction: An unnecessary form of land degradation. Rome: Food and Agriculture Organization (FAO). URL [Accessed: 01.05.2012]. PDF

This factsheet talks about soil compaction and the four key points to prevent it: reduced or zero tillage, controlled traffic, permanent soil cover, rotations and cover crops.


Reference icon

ISU (Editor) (2005): Tillage, Manure Management and Water Quality. Ames, Iowa: Iowa State University (ISU). URL [Accessed: 01.05.2012]. PDF

Tillage and manure application practices significantly impact surface and ground water quality in Iowa and other Midwestern states. An integrated system approach to manure and tillage management is critical to ensure efficient nutrient use and improvement of soil and water quality. This approach, however, requires changes in manure application technology and tillage system management to ensure the success of an integrated system.


Reference icon

MURRELL, S. (n.y.): Tillage Systems. Efficient Fertilizer Use Manual. Mosaic. URL [Accessed: 01.05.2012]. PDF

The way in which tillage systems change fertilisation practices is a complex issue. Tillage systems are sequences of operations that manipulate the soil in order to produce a crop. Operations include tilling, planting, fertilisation, pesticide application, harvesting, and residue chopping or shredding. The ways in which these operations are implemented affect the physical and chemical properties of the soil, which in turn affect plant growth. The first step in making fertiliser management decisions is to understand the practices associated with each tillage system.


Reference icon

GTZ (Editor) (1998): Conserving Natural Resources and Enhancing Food Security by Adapting No-Tillage. An assessment of the potential for soil-conserving production systems in various agro-ecological zones of Africa. Eschborn, Germany: Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) GmbH . URL [Accessed: 18.07.2012]. PDF

This study assesses the various methods employed in agro-ecological zones of Africa in enhancing soil conservation through no-tillage practices.


Reference icon

UNEP (Editor) (1998): Sourcebook of Alternative Technologies for Freshwater Augmentations in Africa. Conservation Tillage. Water Conservation. Harare: Institute of Agricultural Engineering. URL [Accessed: 14.02.2012].

The countries of Africa have seen growing pressure on water resources, with increasing demand and costs, for agricultural, domestic and industrial consumption. This has brought about the need to maximise and augment the use of existing or unexploited sources of freshwater. There are many modern and traditional alternative technologies for improving the utility and augmenting the supply of water being employed in various countries, but with limited application elsewhere due to the lack of information transfer among water resources managers and planners.


Important Weblinks

http://www.infonet-biovision.org/ [Accessed: 14.02.2012]

Infonet-biovision.org is a web-based information platform offering trainers, extension workers and farmers in East Africa a quick access to up-to-date and locally relevant information in order to optimise their livelihoods in a safe, effective, sustainable and ecologically sound way.

http://bettersoils.soilwater.com.au/ [Accessed: 09.02.2012]

A very useful modular tool of the Agriculture Bureau South Australia. Information about soil management, how to describe the own soil and get to know about soil profiles. Module 1 provides an overview of the characteristics of healthy soils, soil classification and erosion potential. Modules 2 and 3 examine the links between soil and nutrition, module 2 from the perspective of crops and module 3 from that of pasture. Soil biota make a significant contribution to the health of your soil and module 4 examines this is in detail. Module 5 focuses on the management of soil moisture including soils' storage properties, summer weed control and PAW. Module 6 is concerned with the barriers-physical, chemical and biological- to effective root growth.