Micro-hydro Power (MHP) Projects - Mitigation and Intervention Techniques - Soil Fertility Management and Biological Soil Conservation

Overview

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Soil Fertility Management and Biological Soil Conservation

Compost Making

Objectives: To promote compost making at household level for cost-effective soil fertility improvement and to support local level compost entrepreneurship linked to natural resources management activities at watershed level. CM will improve soil fertility, increase water storage within the soil profile and reduce surface runoff, thus reduce soil erosion. It is one of the best “hidden” water harvesting methods available (compost absorbs water 4-7 times its own weight). CM can be undertaken at very large scale and linked to area closure management and the upgrading of terraces into “cash crop production belts”. CM can become a business: groups of households (landless, etc.) can decide to become compost makers and provide “fertilization” services to other farmers.

Fertilization and Manuring

Objectives: The current cropping systems in Ethiopia is highly organic as chemical fertilizers are expensive and not always readily available. Manure is used in most areas as fuel or income source. As open grazing manure is not readily available,mulching is not practiced. Furthermore,the crop residues is also used for forage. Low levels of organic matter are leading to reduced soil stability, infiltration, water holding capacity and increasing erosion. Application of fertilizers will increase yields, while manure and mulching will improve long term soil quality and nutrient levels.

Live Check Dams

Objectives: Live check-dams are established by planting/seeding or plugging of cuttings in gully bottoms to replace or reinforce physical check-dams. The main objective of the establishment of live check-dams is to reduce the cost of establishing physical check-dams. Live check-dams can be applied by individual farmers and does not need the organization of a large group of people to undertake physical structures.

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Mulching and Crop Residues Management

Objectives: Mulching is the covering of the soil with crop residues such as straws, maize/sorghum stalks or standing stubble. The cover protects the soil from raindrops, drastically reduces splash erosion and velocity of runoff. It then minimizes erosion, increases soil infiltration and permeability, prevents the formation of hard crusts and contribute to improve fertility. The second major advantage of mulching/crop residue maintenance, is its potential for sustaining productivity. Mulching, in addition to its positive effects on soil structure also helps in reducing evaporation and maintaining soil moisture. The improved soil structure also will have an effect on moisture retention and consequently higher water budgets for the growing crop.

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Grass Strips along the Contours

Objectives: Grass strips are vegetative barriers made out of grass planted in narrow strips of 0.5 to 1.5 m width laid out along the contour. Grass strips control erosion rather effectively in gentle slopes but above 5-8% slope their effect decreases. While contributing to protect soils against erosion they also provide valuable biomass meant to increase animal feed or used for different purposes (eg. roofing, etc.). Grass strips cause less interference than other measures as they can easily be crossed by oxen and plough. Moreover, grass strips take out little amount of arable land. Cost of construction is much lower than physical structures.

Stabilization of Physical Structures and Farm Boundaries

Objectives: Stabilization refers to the planting of crops, grass, shrubs and trees in different combinations in order to strengthen the resistance and stability of physical structures such as bunds, trenches, check dams, SS dams, etc, against rain drops splash effect, runoff and cattle trampling. At the same time, stabilization has the purpose of making productive the surface area occupied by the structure. Stabilized structures would need less maintenance and damages are less likely to occur, even during heavy rainstorms. Trees or shrubs help to demarcate farm and homestead boundaries, thus provide additional sense of ownership. Particular plants are also hosts for insects able to control pest incidence. Stabilized areas are an additional source of timber, fuelwood, fiber, food and forage, palatable grasses and legumes, fruits and other products (dyes, gum, medicinal, etc.).

Vegetative Fencing (VF)

Objectives: Vegetative fencing (VF) is a conservation practice which consist of a combination of vegetative planting materials resistant to cattle grazing planted in rows and with grass/legume plant species sowed behind these rows. Used to protect and enrich reclaimed areas like closures and gullies, farm boundaries and specific community assets like ponds. By doing so it also helps controlling runoff and erosion. It is the “first level of defence” against animal interference that allow other valuable trees to be planted after the fence is established. VF can be exercised as a “grid system” in closures, around reclaimed gullies, and farms, providing increased sense of ownership to users.

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Ley Cropping

Objectives: Ley cropping is a cropping system in which legume based pastures are rotated with purely grown crops. Legume based pastures are grown on fallow lands for a few years to improve fertility of the soil and thus the yields of subsequent crops (mainly cereals). The establishment of dense, productive forage crops during the fallow period (1-3 years) provides a thick ground cover, supply forage of good quality after the rainy season, prevent soil erosion, restore soil fertility quicker than bare (and overgrazed) fallow, increase the water holding capacity of the soil and have a beneficial effect on future crop yields.

Integration of Food/Feed Legumes into Cereal Cropping Systems

Objectives: Better and full use of production resources such as water, radiation, nutrients, space and time. Integration of cropping optimises productivity by producing higher combined yields from the crops and greater economic returns from a given area of land than the same crop grown in monoculture. Lower risk in intercropping than with mono cropping. Better distribution pattern of labour demand. For example, land preparation is done only once for all crops and therefore the labour situation is less constrained. Control pests, diseases and weeds in the absence of biocides. Better control of soil erosion realised.

Intercropping

Objectives: Intercropping is a practice of growing two or more crops along the contour simultaneously in the same plot in a fixed pattern in one season. The aim of intercropping is to increase crop production and provide protection to the soil against erosive forces. Different planting times and different length of growing periods spreads the labour requirement of planting and harvesting, but also allows midseason change of plan according to the rain in the early part of the season. The various leaf arrangements of different plants allow light to be better intercepted over time. The contrasting patterns of root growth, which utilize different soil layers, optimize the use of available soil moisture and nutrients. Mixed stands protect the soil surface more effectively than pure stands. Overall output per unit area can be much greater from intercrops than single crops and chances of total crop losses are lower than in pure stands.

Crop Rotation

Objectives: Crop rotation is one of the oldest practices known to man for fertility restoration and pest/ disease control and it consists of growing different crops one after the other on the same piece of land. Plants of the same crop develop their roots at the same depth of soil profile and thus the proliferation of the root systems in the same depth results in a strong competition for moisture and nutrients. Therefore, if the same crop is grown on the same land year after year, the soil nutrient in that layer decreases sharply and the crop yield consequently declines. On the other hand, if different crops are rotated, the depletion of soil nutrients and decline of crop yields are not as serious as when the same crop is grown year after year. Different crops have different characteristics that enable them to exploit the soil at different depths. Crops also differ in terms of their effect to the soil. Some crops restore or build fertility while others deplete fertility.

Strip Cropping

Objectives: Strip cropping is a cropping practice where strips of two or more crops are alternately established on the contour or, it is a system of establishing more than one crop in alternate strips following a contour pattern for the purpose of erosion control, crop diversification, and decrease the risks associated to the use of single crops only. This cropping system is designed as a defence mechanism against soil erosion in areas where the cropping system is dominated by row/sparsely growing crops that exposes the ground to erosive forces. For instance, crops like sorghum and maize are susceptible to erosion and need to be grown alternately with soil conserving crops.

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Further Information

• Hydro Portal on energypedia

References

• DESTA, L. et al. (2005): Part 1: Community Based Participatory Watershed Development: A Guideline. Addis Ababa: Ministry of Agriculture and Rural Development.