Newsletter and Technical Publications
<Sourcebook of Alternative Technologies for Freshwater Augumentation
PART C - CASE STUDIES
4.1 Tied Ridging -- Domboshawa, Zimbabwe
Zimbabwe has experienced low and erratic rainfall for the decade prior to
1995. To offset agricultural losses related to low rainfalls and variations in
rainfall related to these vagaries of nature, researchers investigated tillage
methods that conserve soil moisture. The major objective in moisture
conservation tillage methods is to conserve moisture in the soil in order to
increase germination and yields. Runoff is greatly reduced and infiltration
rates are increased. Moisture conservation tillage technologies include
tied-ridging, mulching, contour ploughing and minimum tillage, described in Part
B, Chapter 1, "Agriculture".
This case study looks at ridging and tied-ridging in Domboshawa, an area
about 30 km north of Harare, the capital city of Zimbabwe. It is located in the
Highveld of Zimbabwe at an altitude of about 1200 m above sea level. The average
annual rainfall ranges from 800 mm to 1 000 mm per annum. The rainfall is
seasonal with approximately 90% falling in the months of October to March.
Ridging and tied-ridging as carried out in Zimbabwe is widely documented (FAO,
1966). Most of the equipment used for ridging and tied-ridging was locally
manufactured, and designed to be animal-drawn. A typical, ox-drawn disc ridger,
developed by the Department of Agricultural and Technical Extension Services (AGRITEX)
in conjunction with GTZ, is illustrated in Figure 42. The high wing ridger body
is used for making the ridges, and is an accessory to the mouldboard plough.
When making ridges, the ridger body is attached to the plough instead of the
mould board. The ridger produces ridges which are 250 mm high.
The high wing ridger is of French design but is manufactured locally. The
ridger has two adjustable discs angled to form a wide `V' shape. Although the
unit looks heavy, the draft requirement is actually less than that required for
the conventional mouldboard ploughs. Depending on the ridge requirements, the
disc sizes and shapes can be varied.
Ridges made using this technology can be tied using hand hoes. In Zimbabwe,
simple ox-drawn tie-makers have been produced locally. As illustrated, these can
be made from old mouldboard plough shares or discs fitted on to metal or wooden
uprights. In order to avoid having too many operations, ties can be coupled to
the ox-drawn disc ridger (Figure 43). They can also be fitted onto cultivators
(Figure 44). Ties are made by scraping the tie-maker along the furrows between
the ridges until enough soil has been collected. The collected soil should be
about 1/2 to 2/3 the height of the ridges.
Figure 42. Ox-drawn disc ridger with tie-maker attached.
Source: Makoholi Research Station
Extent of Use
The Ministry of Agriculture, through AGRITEX and the Department of
Research and Specialist Services (DR&SS), was responsible for the
research and extension of the technology. The programme started with field
trials. During trials a few farmers were selected to participate. Results
from the trials proved that the tied-ridging method of tillage produced
better yields than the conventional methods of tillage traditionally used
by farmers in this area. The fact that farmers saw the benefits of the
system made it easy for the extension personnel to convince the rest of
the communities to adopt the method.
Nevertheless, there has been some measure of resistance to changes in the
traditional methods of cultivation. This resistance was compounded by shortages
of labour and draft power. Shortages of labour resulted from male migration to
urban areas in search of employment, while the shortage of draft power resulted
from reduced animal stocks due to the drought. All of these obstacles have not
yet been overcome, and, although the method is acceptable to the farmers, it is
not widely practised. Only 1% of the farmers in the area use the method (Elwell,
Operation and Maintenance
Ridgers and tie-makers do not require any special skills to operate or
maintain. There are few components that need replacement, and, hence, the
technology is very suitable for communal operations. Disc--ridgers and ridger
bodies wear out with time, but replacement is not a problem since the equipment
is locally manufactured.
Level of Involvement
The government, local communities and non-governmental organizations were all
involved in the project. The government provided the personnel for the research
and extension while GTZ provided some of the funding.
Figure 43. Ox-drawn disc-plough tie-maker.
Source: Institute of Agricultural Engineering, Harare,
Figure 44. Light Cultivator with tie-maker mounted.
Source: Institute of Agricultural Engineering, Harare,
The major cost is the purchase of the ridgers and the tie-makers. Where the
farmers already have mouldboard ploughs or cultivators, the cost will be low
because the ridger body and the tie-maker can be fitted easily. A new ox-drawn
ridger costs $300 and a new mouldboard plough costs $30. If the farmers do not
have their own implements, the cost of hiring the equipment to have one hectare
ploughed and tie-ridged will be $250. Effectiveness of the Technology As shown
in the following table, the results of the field trials showed that there was a
reduction in runoff from fields with tied-ridges compared to those with
The advantages of tied-ridges include reduced erosion and conservation of
soil moisture. The equipment used is simple and easy to use, and capable of
being locally manufactured and maintained. The field trials clearly showed
improved crop yields.
Tied-ridgers require new or additional equipment, and substantial time and
effort required to prepare the lands each year. This increases farmers' costs.
In areas with highly variable rainfall, ridges can fail due to overtopping. When
this occurs, greater soil losses may result.
Further Development of the Technology
The technology has great potential for use in arid and semi arid regions.
However, in order for the technology to be accepted and adopted, much effort has
to be put in the research and extension services. The government has to be
strongly involved in the exercise. The technology is easy to adopt if the
farmers are mechanized and they have enough draft power. Availability of draft
power is essential because substantial time and effort is required for the land
preparations. For countries wishing to adopt this technology, it is very
important to make sure that an effective extension service, adequately financed,
is in place.
Sources of Information
D. Dube, ARDA, Post Office Box CY 1420, Causeway, Harare,
Institute of Agricultural Engineering, Post Office Box BW 330,
Borrowdale, Harare, Zimbabwe, tel. 263-4-860119 or 263-4-860055.
I. Nagambie, Conservation Specialist, Institute of Agricultural
Engineering, Post Office Box BW 330, Borrowdale, Harare, Zimbabwe, tel.
263-4-860119 or 263-4-860055.
G. Nehanda, Chief Planning Officer, Head of Station, Institute
of Agricultural Engineering, Post Office Box BW 330, Borrowdale, Harare,
Zimbabwe, tel. 263-4-860119 or 263-4-860055.
A. Senzanje, Department of Soil Science and Agricultural
Engineering, University of Zimbabwe, Post Office Box MP 167, Mount Pleasant,
Elwell, H.A. 1993. "Development and Adoption of Conservation Tillage
Practices in Zimbabwe." FAO Soils Bulletin 69, Soil Needs in Africa
Needs and Challenges. FAO, Rome.
FAO (Food and Agriculture Organization of the United Nations) 1966. Equipment
of Tied Ridge Cultivation from Power and Machinery. Informal Working
Bulletin No. 28, Rome.
Vogel, H. 1992. Conservation Tillage for Sustainable Crop Production
Systems. Project Research Report 5, Institute of Agricultural Engineering (IAE),