Question

25 )An effective method to control wind erosion
i.Terrace farming
ii. Contour bunding
iii. Planting of shelrer belts​

Answer 1

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i.Terrace farming

Answer 2

Answer:

Most Australian soils are old, have low levels of nutrients and have very thin topsoils.

Explanation:

Most Australian soils are old, have low levels of nutrients and have very thin topsoils. These topsoils take a very long time to form and can be eroded by even slight winds.

Shelterbelts can provide a relatively cheap and long-term option for reducing wind erosion on farms. Shelterbelts are used to decrease windspeed within the sheltered zone and reduce the erosion of fertile soils on agricultural land. This can increase the productivity of agricultural land by protecting this valuable topsoil and nutrients.shelterbelts provide a high level of protection but over a reduced area when compared to less dense belts. Moderately dense belts (~40% density) will provide a considerable reduction in wind speed to a distance of at least 20H. Dense belts generally provide good shelter to a distance of at least 15H.

To control wind erosion over a large area the height of a belt needs to be maximised. Therefore it is wise to incorporate at least one row of tall species within the belt.

It is important to incorporate shrubs into a belt where an even density is required from the ground to the top of the belt. It is also advisable to fence out a belt to prevent stock grazing on the lower limbs of vegetation and creating gaps. If gaps occur within a belt, wind will tunnel through the gaps at an accelerated rate. This can result in blowouts near the gaps and also be detrimental to stock and crops.

Wind speed accelerates around the ends of shelterbelts. By increasing the length of the belts or joining them to other belts this impact is reduced. Belts can be joined where they can form a right angle for protection from a range of wind directions as illustrated in Figure 1. Stock should not be able to graze below or at the ends of a shelterbelt as these areas are very susceptible to erosion. The more effective a belt is in reducing wind erosion, the more eroded the sites at the end of the belt can be, unless the ground surface is protected.