Land Regeneration Techniques

Environmental Issues Mechanical degradation of the soil is a consequence of movement and visit of animals, either directly by trampling (surface compacting of the soil), or indirectly as a result of partial or total disappearance of plant cover (wind and water erosion). Mechanical degradation of the soil is produced in areas much frequented by livestock, but is particularly worrying in areas subject to major climatic constraints, especially sub-arid areas. This is one of the causes of desertification. | Environmental Issue Objectives Techniques Costs Targeted Livestock System Impact Context of Application Monitoring: EIA, Indicators References
Objectives One is attempting to restore or increase the water content of soils, and thus watering of plants by improving the structure of these soils and reduction of rain water run-off. Several means are adopted: Breaking up the surface of the soil. Creation of a certain roughness of the soil, thus creating micro-reliefs. Establishment or maintenance of plant cover. Control of animal load. It goes without saying that the causes of degradation should be reduced or eliminated, i.e. manage and control the animal load. This technique enables regeneration of natural grass and tree vegetation, in all their botanic diversity. This vegetation should be considered part of the biological activity of the soil, as a mechanical protector of that soil and a provider of biomass and forage. |
Chad, N ’Djamena Region. Vegetation has almost completly disapeared near a village after a long period of overgrazing and several land clearances for cropping (click on photo to enlarge)

Techniques

Fencing

> Protection for a longer or shorter period of time of a plot or area with a view to removing it from all forms of exploitation (people and herds); to be effective, this requires a long period which should not be less than ten years.

Prevention of surface erosion can be done in different ways:

- Spreading of dead wood or big plant debris on bare surfaces: dust and organic debris are trapped by these branches which filter the wind. This is a fast and fairly effective method of rehabilitation. It can only be recommended in wooded areas or places where it is easy to make hay.
- Stone walling along the contours, or at least perpendicular to the line of the steepest slope with: spacing 30 m or more depending on slope and state of the area; use on sites where there are resources nearby and in difficult areas where other techniques cannot be used.
- Construction of small earth dikes, along the contours, or preferably in crescent formations placed to retain water run-off. Improving water infiltration enables progressive establishment of vegetation.
- Ploughing the soil :

- Surface tilling of the soil: this can break down a superficial crust and encourage germination of plants.
- Results vary depending on the place and period the work is done, and are of short duration.
- Decompacting in depth: this is done using a mechanical plough or other instruments with vertical teeth. This is a fast effective method of rehabilitation, but requires powerful tools. With a tractor and a 3-tooth plough, ploughing to a depth of 20-25 cm, 1 ha. of bare compacted soil is ploughed in 2 hours; a distance of 50 cm between rows is satisfactory.

Re-vegetation

Sowing in pockets: in a hole 3 cm deep dug with a hoe, a few seeds per pocket are sown and covered with a fine layer of sand lightly packed. By sowing every 30 cm in all directions, it is possible to establish 100,000 pockets per hectare. Productivity is connected more to drought than ploughing. Manual ploughing: the period of ploughing plays an important role. With early ploughing (at least 3 months before the rainy season) production is high and can be exploited. With late ploughing (after the most rainy season), production expected is lower but the aim is especially to cover the soil with plants. Mechanical ploughing: this precedes the sowing of cover or forage plants. |
Degraded soil before rehabilitation, Chad. (click on photo to enlarge)

If the degraded soil is very impoverished in organic matter and fertilising elements, it may be necessary to proceed to progressive re-vegetation, beginning with fertilised pockets into which perennial species or trees which are not demanding are introduced, which will progressively form a litter and a seed source for total cover of the soil after a few years.
This technique is especially employed to re-vegetate land which has been mined. It may be useful to improve biological activity of the soil by introducing bacteria existing naturally in the rhizosphere of plants in normal conditions (Rhizobium and symbiotic bacteria, Azotobacter and bacteria facilitating use of nitrogen).

Penning: this consists of making animals stay for a long or short period to encourage trampling of the soil and the dropping of faeces. After removal of the pen, vegetation develops in the surface mixture of soil and droppings.

Costs

- Some examples in Sahelian Africa:

- Fencing:, 1 ha. of fencing was evaluated in 1989 at 340 Euro.

- Small dikes:

- Spreading dead wood: from 10 Euro/ha. (with free wood close by) to 100 Euro/ha.
- Stone contour walls: for 100 m of walling you need 8 or 9 people/day with a pair of oxen and a cart. Maintenance of the walls requires 0,5 people/day/year for 1000 m of walling.

- Ploughing the soil:

- Manual ploughing: from 145 hours/ha. on bare, compacted humid soil to 450 hours on dry soils.
- Mechanical ploughing: Costs are no higher than those for manual ploughing, this but requires appropriate organisation of the work.
- Costs of rehabilitation: between 17 - 43 Euro per ha, ( for 30 kg/ha of phosphorus, it requires 20,6 Euro per ha).

Targeted Livestock System

Pastoral systems and mixed systems

Grazing System

LGA | LGS1 | LGS2 | LGS3 | LGH1 | LGH2 | LGH3 | LGT1 | LGT2 | LGT3
Y | Y | Y | Y | Y | Y | Y | Y | Y | Y

Mixed System

MCG | MCR | MCC | MFF | MEF
Y | Y | Y | Y | Y

Industrial System

IFP | IPL | IPG | IRM | IDU | ISL | ITN | IMP
N | N | N | N | N | N | N | N

Impact

- Positive environmental impact

- Fight against wind and water erosion.
- Improvement of soil fertility.
- Regeneration of vegetal cover.
- Development of wild animals.

- Negative environmental impact
Risk of introducing weed and unwanted species (in situations where exotic species are introduced).
- Impact on Livestock productivity (milk, reproduction, meat, health, etc.)
This technique, through its effects on forage potential, enables all the livestock and herd parameters (milk, reproduction, meat, health) to be improved.

Context of Application

After a series of campaigns to moderate the phenomena of drought/desertification and their effects on the environment on both social and economic life, the international community, in partnership with countries in the affected areas, now has new arguments to defend among other things the restoration and rehabilitation of land which was formerly productive and rich in natural resources.

- Favourable factors:

- Mobilisation of actors on the issue of soil degradation.
- Reduction of rangeland areas to the benefit of other economic activities.
- Reduction of soil fertility.
- High costs of fertilisers.
- Opportunity of animal products valorization.

- Unfavourable factors:

- Costs of operations, inputs and materials (fencing) compared to the economic gains expected.
- Status of communal lands.
- Lack of mastery of the practice by the rural people.
- Insufficiency of construction materials.
- Labour requirements.
- Limited number of rural people who own livestock (pens).

Monitoring: EIA, Indicators

- Rate of plant cover of the soil.
- Apparent density of the soil.
- Biodiversity co-efficients.
- Retention of nitrogen or organic matter of the soil.
- Co-efficient of run-off or capacity for infiltration of the soil.

An example of Land Rehabilitation near Arusha, Tanzania.

One side of a small valley: No land rehabilitation has taken place. Heavy sheet and gulley erosion. Almost no grazing resources are available. | The other side of the same valley: A range of land rehabilitation techniques have been used at individual household levels.

References
Ruelle P. et al. 1990. Défense et restauration des sols - fiches techniques Vol 1, n°1-6 ISRA/CIRAD-IRAT

Rochette R.M., 1989. Le Sahel en lutte contre la désertification. Leçons d’expérience. GTZ éd., Weikersheim, RFA, pp. 592.

Boudet G. et al. 1987. Pâturages et élevage au sud de la Mauritanie (Kaédi). Etude intégrée sur les pâturages, leur conservation et leur restauration. IEMVT, Maisons-Alfort, pp. 282.

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