Reducing Land Degradation
- Improving Water Management
(Page 1)

The importance of water management in reducing land degradation cannot be over-emphasized. In large parts of the world the soil’s capacity to store water has decreased, because the raw material for soil organic matter is reduced when people use too much of the produced plant biomass.
A reduction in the amount of soil organic matter in turn means lower crop production, as the ability to retain plant-available water and nutrients in the soil decreases.

Below, Professor Nils Nykvist shared some of his knowledge on how how water can be better managed to bring about reduced land deterioration.


By Professor Nils Nykvist

Increasing organic matter in soil

One of the most important measures for better water management is therefore to increase the amount of organic matter in the soil by not destroying the plant biomass by, for example, burning.

Better availability of firewood through forest plantations would also improve the soil in many parts of the world where most of the residues from the harvesting of agricultural crops are used as fuel, instead of increasing the soil organic matter.

When plant remains decompose in the soil, substances are formed that act as glue between the clay particles and contribute to the formation of soil aggregates that improve the penetration of air and water into fine-grained soils.

If the water cannot infiltrate into the ground fast enough after a rain, the soil become temporarily waterlogged, which impedes roots from taking up oxygen, and if the ground slopes, the fine and most valuable soil particles are lost by soil erosion (Fig. 25).
Figure 25. During the rainy season, a thick porridge of soil and water flows in the rivers. During the dry season, they are completely dried out. Tanzania.

Managing the flow of water down slopes

The surface runoff of rain-water and thus also soil particles increases with slope length and can for long slopes become so great that the water flow is difficult to stop.

Measures to reduce the surplus of water must therefore start at the upper part of the slope, where simple earth or stone walls perpendicular to the slope can be enough to stop the excessive flow of water. The walls also capture soil particles eroding down the slope, which contributes to better plant growth and thus to further decrease of water volume due to the plants’ water consumption.
In many parts of the world, soil erosion has reached a stage where most of the soil has been eroded away from the hills and deposited in the valleys or in the sea. Since soil and plants no longer stop the water movement down the slopes, large, often catastrophic, floods can occur further down the slopes and in the valleys.

However, even if the mountains are almost barren, they still can have a significant impact on agriculture in dry areas. The rain that falls on the mountains is not lost to any great extent by evaporation or plant transpiration, but runs downhill to lower-lying areas, where the water can be used for irrigation by pumping from the aquifer in the valley bottom.

See the references for this article.

>> Page 2

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