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Mg ha-1

Low

0.9

1.1

1.6

0.7

0.7

2.2

2.0

High

3.5

4.6

6.4

3.0

3.0

9.1

12.2

Low

0.6

0.8

1.0

0.4

0.4

1.5

1.0

High

1.8

3.0

4.2

2.0

2.0

6.0

8.1

Low

0.3

0.4

0.5

0.2

0.2

0.7

0.3

High

1.2

1.5

2.1

1.0

1.0

3.0

4.0

equipment are known they remain out of reach due to supply shortcomings or cost. These farmers however still work to achieve the traditional fine

tilth, which in most cases is unnecessary. With ongoing shortages hitting tillage, weeding and other labour needs, animal traction will continue to have a place in the smallholder farming system.

Table 4: Yield potential of crops+

Land capability Input

Very suitable

Suitable

Marginal

+From FAO (1978)

Millet Sorghum

Maize Soybean

Bean Sweet Cassava Potato

Conservation tillage has been defined in various ways which all capture the need for less soil manipulation, hence reduced energy requirement and capacity to leave crop residue on the soil surface during all tillage operations (primary or secondary). The common theme is one of reduced soil and water losses.

Due to continued use of traditional manual, animal drawn and even tractor drawn mouldboard ploughing, many farms in ESA have

lost large amounts of soil to erosion.

Especially

where disc animal and consistently,

and mouldboard ploughs (both tractor drawn) have been used hard pans have formed and soils no

longer

have

capacity

to

allow

easy

percolation

of

water and nutrients from plants as roots are unable to dig into lower soil zones. Overall, a case of increased runoff results. Traditional tillage systems generally are energy intensive and leave behind overly pervourized soils with destroyed soil structure. The high energy tropical rain storms easily carry away soil from the desirable but vulnerable fine tilth seedbeds, which farmers insist on having.

Oldreive, (1993), a practising farmer helped show clearly the gains of higher input agriculture as well as conservation tillage. Chart 1 below shows how a higher investment in better farming standards can easily translate into higher profits per unit of land.

rain or irrigation water. for humid, as it is for

This situation is semi- and arid

as bad areas.

Reduced

percolation

leads

to

deprivation

of

9,

This paper is published in: Kaumbutho P G and Simalenga T E (eds), 1999. Conservation tillage with animal traction. A resource book of the

Animal Traction Network for Eastern and Southern Africa (ATNESA). Harare. Zimbabwe. 173p. A publication supported by French Cooperation, Namibia. For details of ATNESA and its resource publications, see http://www.atnesa.org

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