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Control measures

[Plates 20 and 21]

In recent years, the Salagnac project has implemented a number of important activities (a marketing network, a store of inputs managed by a farmers' association, a people's savings and credit bank, individual and communal cisterns). The situation was ripe for an environmental management investment project (PRATIC) based on this approach.

So far as intensification of plant production is concerned, there are three spheres that now offer a promising future for the densely populated mountainous areas:

• the market garden and food crop combination: market-garden crops are the top rotation crops and pay for the applications of mineral fertilizer that often allow a doubling of foodcrop yields;

• fruit tree farming: a sizeable and growing market in the United States;

• dairy farming.

The solutions envisaged addressed production and farm issues at the watershed and individual plot levels alike. Technical proposals were tested for each of the agro-environmental units (Figure 82) for:

• management of surface water;
• management of fertility and biomass;
• management of livestock;
• development of agroforestry;
• support activities to backstop these proposals.

SUGGESTIONS FOR IMPROVED MANAGEMENT OF SURFACE WATER

Harvesting runoff: diverting potentially dangerous water and putting it to good use

Such water is harvested especially in Units 1 and 2, allowing:

protection of areas with good agricultural potential (A and B gardens, soils with good potential) against runoff; 3 km of paved track (US$12/m) have been built downhill of land with strong runoff (rendzinas) and uphill of ferralitic soils, allowing recovery of this water; the feeder road serves as a water harvesting area, and is protected by low walls and reinforced by channels acting as outlets into torrential gullies;

increased availability of water, completely absent in Unit 1, for domestic needs, supplementary irrigation for establishing individual small pre-season market gardening nurseries, and watering semi-penned livestock; farm labour also becomes more plentiful by releasing household members from the time-consuming task of fetching water (2 to 3 hrs/day).

Collective cisterns in the fields (50 to 150 m) store water from tracks, paths or eroded slopes, as do individual tanks (8 to 12 m) from the roofs of houses. About 20 field cisterns (US$40/m) and 550 individual tanks (US$35/m) have been built.

Stone sills (Unit 1) have also been built to help trap sediment load and water in small gullies, with a view to creating islands of fertility, quickly capitalized on by farmers.

All these infrastructures have also allowed:

access to previously hard-to-reach areas: the feeder road facilitates transport of farm produce to markets and will eventually reduce the use of pack animals to carry the produce; this would allow a partial reduction in overgrazing;

an immediate and visible improvement in income by creating employment for the most poverty-stricken (wages for work on structures considered "communal": track, cisterns, low protection walls, and sills).

The choice of structures and their location was made after a study of each sub-basin, and with the participation of the farmers. The study defined areas with heavy runoff, areas with good agricultural potential to be protected, locations for structures to divert excess water into torrential gullies, and the route to be taken by the track. The planning sometimes incorporated elements of production systems - building cisterns near areas where market gardening is well-developed.

Maximum infiltration and dispersion of runoff energy

Several techniques allowing better infiltration - farming techniques such as mulching and hedge-planting, i.e., contour planting of permanent vegetation - have been used on many farm plots, mostly in Units 1 and 3. All these act as buffer strips, halting sediment transport during tillage (mass movement caused by tilling from top to bottom of the slope) or heavy rain (sheet erosion), and should therefore lead in the medium term to the development of gradual terraces. This process requires simple but specific and regular upkeep. It makes use of the traditional techniques of wattle and hedged enclosures, and allows runoff to be slowed when the hedge is reinforced with its own residue (woody offcuts when gathering forage or firewood, or when pruning) and harvest residues (twigs, branches and straw) which are laid against this permanent vegetation. However, vegetation must be reinforced in fragile zones, and new filters of plant residue added when the old ones are destroyed or covered with soil, to prevent breaches.

Planting hedges is one of the techniques most widely extended by the project. It is clearly more beneficial on basaltic soil (Unit 3), for the material weathers very fast, and there are excellent possibilities of restoring soil fertility on degraded soils.

The potential is slight for calcareous soil (Unit 1), and the technique is attractive only for plots that still have good potential.

Few live hedges have been planted in Unit 2 areas, which still have good tree cover and were not considered a priority.

On the Aquin plain (Unit 4), hedging techniques have been used to treat gully bottoms. Weirs made of vegetation are built on alluvial deposits (deeper soil, rich in organic matter and with good moisture content) carried down by torrential, rain-caused erosion and trapped by small sills made of sacks of soil. This technique allows cultivation of such financially viable crops as banana, pineapple and coconut.

SUGGESTIONS FOR IMPROVED MANAGEMENT OF SOIL FERTILITY AND BIOMASS

If the productivity of land and labour is to be increased, a vital first step is improved management of water, but also of nutrients and organic matter.

The nutrient turnover cycle should therefore be improved by reconsidering the use of the available biomass, which should be considerably boosted by material from the newly planted hedges.

The project began to extend the practice of surface mulching with a mixture of Leucaena or Gliricidia septum residues and maize or sorghum stubble on the sloping ground of Units 1 and 3. This cover will probably be able to solve 80% of runoff and erosion problems on basaltic soil, and will considerably improve the balance of organic matter in calcareous soil, which is often very deficient. The technique has already been very successful on market-garden plots spread with mineral and organic fertilizer in the form of spot applications of powdered corral dung. The straw-dung combination produces "real manure," which is more effective in fixing the nitrogen in excrete.

SUGGESTIONS FOR IMPROVED MANAGEMENT OF LIVESTOCK

Animals - apart from cattle - are a form of savings that gives a quick return. However, there are considerable difficulties involved in their management in Haiti:

• left free, livestock prevent or destroy any biological control measure;
• tethered animals compact the soil, overgraze it and foster runoff.

TABLE 42
Selection of species on the basis of agro-environmental factors and types of structure

sub-units

vegetation fences

contour hedges

planting in rows or scattered


formed of trees

formed of bushes

formed of trees

formed of bushes

leafy vegetation


1.1

Grevillea robusta
Cedrela odorata (cedar)
Morus alba (mulberry)

Hibiscus rosasinensis (Chinese/Tropical hibiscus)
Erythrina indica (pine nut)
Comocladia domingensis (pagnol wood)

Citrus maxima (chadequier)
Citrus sinensis (orange)
Cedrela odorata

Leucaena diversifolia
• Gliricidia sepium
Hibiscus rosasinensis

Panicum maximum (Guinea grass)
Penisetum purpureum (elephant grass)

nil

1.2

Grevillea robusta
Pinus occidentalis (pine wood)
Ocotea leucoxylon (sand laurel)

Erythrina indica
Comocladia domingensis
Bursera simaruba (gum tree)

idem 1.1 +
Grevillea robusta

Leucaena diversifolia
Hibiscus rosasinensis

Penisetum purpureum
Tripsacum laxum (Guatemala grass)

nil

1.3

Pinus occidentalis
Casuarina equis. (filao)

idem 1.2 +
Leucaena diversifolia

Pinus occidentalis
Casuarina equiset. (horsetail tree)

idem 1.2

Penisetum purpureum

Pinus occidentalis
Casuarina equis.

1.4

idem 1.3

idem 1.3

Persea americana (avocado)

nil

nil

idem 1.3

2

NO INTERVENTION


3.1

nil

Persea americana
Manguifera ind.

3.2

Swietenia mahogany (cashew)
Macrocatalpa longissma (oak)
Lisyloma latisiliqua (tavernon)
Pithecellobium saman

Gliricidia sepium
Leucaena leucocephala
Jatropha curcas (oil tree)

Persea americana
Manguifera indica
Citrus aurantifolia (lime)
Annonna reticulata (cherimoya/custrdapple/sweetsop)

Gliricidia sepium
Hibiscus rosasinensis

Penisetum purpureum

nil

3.3 et 3.4

Haematoxylon campechianum (logwood)
Lisyloma latisiliqua

Jatropha curcas
Gliricidia sepium

Anacardium occidentalis
Citrus aurantif
Annonna reticulata

Gliricidia sepium
Leucaena leucocephala

nil

nil

4

Stabilization of gullies (r)

Annonna reticulata
Manguifera indica
Tamarindus indica

nil

Musa sp.
Penisetum purpureum
• Ananas

nil

However, the direction of the Salagnac/Aquin project, which is concerned with dairy production, has been towards semi-stabling, with livestock being kept in stables during the night, then being either tethered during the day or led to watering sites. This livestock management method could be developed thanks to increased fodder production (hedges), an increased number of watering points (tanks), but also more fencing to prevent animals from straying.

THE IMPORTANCE OF AGROFORESTRY IN THE SUGGESTED TECHNIQUES

Agroforestry techniques developed under the project meet a variety of needs:

• improving infiltration by slowing flow rate;

• increasing production of biomass (about 3 to 5 t/ha/yr where the distance between risers is about 10 m) to improve fertility organically, spreading the residues from shrub legume cuttings on the ground; this biomass will restore nutrients quickly but steadily, and is also useful for feeding livestock (cut grass and legumes), firewood and, in the longer term, fruit and timber production;

• reducing erosion problems in synergy with the above measures and halting various processes of sediment transport;

• improving protection from wind and straying animals.

The main aim is not to reforest all the degraded areas but rather to:

cover 40 to 60% slopes by replanting trees in well-spaced stands on very degraded land, and in more scattered formation on cultivated plots, in order to check the movement of the soil cover; fruit species have been planted (150/ha) on Units 1, 2 (calcareous-marly) and on Unit 3 in 0.5 m pits with a good dose of organic matter;

partition the countryside with multipurpose risers and surrounding plots with windbreak hedges of forest or fodder species, while promoting the development of gradual terraces; planting hedges to protect against straying livestock, to act as wind-breaks, and to stabilize the risers (along the route of a road or path), and also to mark off property and encourage intensification (market-garden crops, fruit trees); large cuttings are used to form partitions which are then reinforced with forest trees.

Various species have been used (Table 42) for such partitions, chosen on the basis of production factors (tenure, distance, arable land), farmers' needs (fodder, wood, fruit, etc.), but also the physical potential of the plot, according to the sub-units described above. These species are carefully distributed over the area in question:

• forage grass on the risers as they are built to hold them in place and act as a second filter;

• hedges of legumes grown as bushes (2 to 3 prunings a year) on the upper side of the risers every 25 cm;

• forest or fruit trees below the risers (or above, if the soil is very moist), 5 to 8 metres apart depending on the space between risers.

SUPPORT MEASURES

These indispensable measures encompass:

Introduction of more profitable crops - market-garden production. This diversification of crops in Units 1 and 2 is the "transmission belt" between control measures, increased soil fertility and increased productivity and production with the corollary of increased income. The constant expansion in cash crops means that the farmers now hope to protect and therefore better manage their land. Development measures require various kinds of support measures as for cabbage-growing. Cabbage requires a significant investment by the farmer (seed, fertilizer, organic matter, water, treatment products), and although cabbage is often planted in C or D gardens, the farmers would now like to improve these gardens by adding wind-breaks and fences, and planting grass to benefit from fertilizer inputs and existing tanks and fruit trees, thus ensuring protection and a better return on their investment. For the first time, fertility is being transferred to C and D gardens.

Measures concerning livestock. The emphasis today is on increasing milk production, which entails action to improve nutrition, management, and genetic factors.

Diversification of fruit production. A number of double-grafting programmes (grafting on adult trees over 5 years old) have been implemented right across the whole transect in order to introduce improved varieties (oranges, mandarins and grapefruit for the American market) or off-season varieties (mangos, avocados) for the national market.

Better land tenure. The proposed control measures represent a significant outlay in labour and sometimes money. When farmers have good land tenure security, they are much more interested in improvements that do not offer an immediate return. Otherwise the real owner may very well want to recover a plot that has been rented out or sharecropped, or perhaps increase the rent. Most control measures have been confined to owner-operated plots - which restricts interventions aimed at a whole hillslope or sub-watershed.

Similarly, the introduction of intensification techniques (the use of mineral and organic fertilizers) will be difficult if the plot is share-cropped or in short-term tenancy, even if returns may be immediate, for such an investment can work to the advantage of the owner, who can then take back his/her land the next year. It has been seen that the most degraded plots are those where land tenure security is weakest, and that fertility is constantly being transferred from these plots to others.

Trials of long-term leases (8 to 10 years) were started when the contract between the project, the owner and the tenant was signed (the situation is more complicated for share-croppers), thereby giving greater tenure security and entitling the tenant to benefit from what his/her investments produce.

On-site trials. These are very important, and must serve as demonstrations. They have consisted in:

• introduction of the technique of tied ridging to replace potato mounds on steeply sloping ferralitic soil (sub-units 12); this trial could not be continued;

• trials on different horizontal biological structures with different plant materials (Gliricidia septum, Calliandra);

• more exacting studies on the relation between erosion risks and runoff under different cropping systems, and on the effect of contour hedges and hedge management on total water, fertility, erosion, and biomass: production; political events prevented the implementation of these trials.

CONCLUSIONS

There have been many projects to develop the rural sector in Haiti which have often disrupted the physical environment by implementing poorly integrated erosion control structures which were, moreover, seldom properly maintained.

Land husbandry offers new hope in terms of interventions in the rural sector. Its methods show that there is no contradiction between development of agricultural production (intensification and diversification of plant and animal production) and protection and conservation of the environment (fertility, soil and water) which is the true basis of such production. This strategy must be identified with the human landscape. Its success depends on understanding how farming systems operate, and on knowing the physical environment and more particularly the potential of the soil.

Erosion problems vary enormously because of the great variety in physical, social and economic contexts. However, peasant farmers continue to use management techniques that cause the least imbalance in the environment. It is vital that these be taken as a starting point and improved, if integrated solutions are to be found. This approach will ensure that the farmers adopt and maintain the various measures and structures, intensifying production and protecting, the environment.

Figure

Chapter 13. Agricultural erosion in the Ecuadorian Andes

A NATURAL AND HISTORICAL PHENOMENON

G. De Noni and M. Viennot, ORSTOM, Montpellier, France
G. Trujillo, Ministry of Agriculture and Animal Husbandry, Quito, Ecuador


The situation
Soil erosion: diagnosis and source
Hazards: the impact of erosion on the agricultural environment
Suggested improvements


The situation

Although Ecuador is a small country (270000 km) in terms of the South-American continent, it contains a remarkable mosaic of landscapes. This variety, which encompasses the juxtaposition of cold, temperate and hot ecosystems within a short space, is a result of the huge mountain barrier of the Andes, locally called the Sierra. This range, running from north to south through the centre of the country, is bordered on the west by the Pacific coast and on the east by the Amazonian foothills. Wedged between two low plains, the Sierra is hence a classic mountain environment with striking variations in altitude.

Human activity, traditionally agricultural, has had to adapt to this high mountain environment. Early on, during the two thousand years preceding the Spanish conquest, the Sierra was the centre of a flourishing agriculture, for the population, which never exceeded 200000, was able to develop an approach that was in harmony with the environment. These long-ago societies spontaneously practiced crop diversification and land use involving different ecological zones, and developed an irrigation system with channels following the contour of a tight network of terraces. Over the centuries, the troubled history of the Spanish conquest and more recently the social effects of population pressure have forced an imbalance in the relationship between human beings and environment. At present the agricultural frontier is expanding upwards and is coming up against the constraints imposed by mountains (those of climate and slope). This is the context that has seen the development of the minifundio area - which, in the very difficult conditions of foodcrop plots of less than 1 hectare, is now facing acute erosion problems.


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