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Agriculture in dry lands: principles and practice

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The dry lands with which this work is concerned, are the areas of meagre or undependable rainfall, in which the average precipitation is deficient in relation to water requirements. These include the arid zones, in which arable crop production is not possible without irrigation, and also their semi-arid fringes, in which rainfall, though precarious, is sufficient for certain types of crops, requiring special management techniques.

It is an interesting fact of history that in most of the dry lands in the Near East, India, North Africa, and Central Africa, very advanced agricultural civilizations developed, flourished, and eventually disappeared.

Whatever the reasons that prompted early man to choose the arid and semi-arid lands, in preference to the more favourable conditions for agriculture of the temperate regions with more reliable rainfall, it is clear that he chose an environment in which the balance between his own activities and the environment is extremely precarious. The central problem of sustained land use in the dry regions has always been to find and maintain a balance between man's requirements and the productive capability of the land. This has rarely been achieved in the long run.

Throughout history, man has, by over-use, consistently reduced the productive capacity of dry lands. Originally, a large proportion of the more or less scanty vegetative cover consisted of palatable and nutritious grasses and shrubs. Overgrazing caused an overall reduction of the plant cover, and the large-scale replacement of useful plants by unpalatable species. The reduced cover intensified erosion by wind and rain, starting a process which is frequently irreversible. Gullies cut through alluvial valleys, water run-off increased, and water-storage reservoirs filled with silt. Where the original plant cover of areas on the fringes of the arid regions was ploughed up for crop production, the consequences were still more disastrous. The classic, though by no means isolated, example is that of the 'dust bowl' of the Great Plains of North America.

In most dry land areas in which irrigation agriculture was developed, the consequences of cultivation were in the long run no less catastrophic; salinization and water logging have reduced once-fertile regions to barren wastes. Economic deterioration was accompanied by political instability and the inability to withstand invasions of nomadic tribes. Wide areas were gradually abandoned, and the erstwhile cradles of civilisation became man-made deserts.

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Informasi Detail

Judul Seri

DEVELOPMENTS IN AGRICULTURAL AND MANAGED-FOREST ECOLOGY 26

No. Panggil

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Penerbit

Amsterdam : Elsevier Science Publishers B.V.., 1992

Deskripsi Fisik

SB110.A76 - 631 .5'86—dc20 92-12960 CIP

Bahasa

English

ISBN/ISSN

0-444-88912-4

Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

PERTANIAN.

Info Detail Spesifik

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Pernyataan Tanggungjawab

agus

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