By Anthony E. Hall
The semi-arid zones of the realm are fragile ecosystems that are being sub stantially converted by means of the actions of mankind. expanding human populations have led to higher calls for on semi-arid zones for offering human susten ance and the prospect that this can increase desertification is a grave main issue. those zones are harsh habitats for people. The famines that resulted from drought throughout the past due 1960's and the 1970's within the African Sahel illustrated the unreliability of current agricultural structures during this area. huge fluctuations in ag ricultural creation have happened in semi-arid zones of Australia, North Ameri ca, and the Soviet Union as a result of periodic droughts, even if enormous ag ricultural expertise has been dedicated to agricultural improvement in those zones. The problem to mankind is to regulate those varied semi-arid zones in order that professional ductivity is elevated and stabilized, and environmental deterioration is reduced. Irrigation can be utilized to extend and stabilize agricultural construction in semi-arid zones as mentioned in quantity five of this sequence, Arid sector Irrigation. the current quantity, Agriculture in Semi-Arid Environments, specializes in dryland farming in semi-arid zones, and is correct to the massive parts of the realm the place rainfall is proscribing and the place water isn't really to be had for irrigation. This quantity is designed to help agricultural improvement in those parts and comprises reports and analyses of accessible details through scientists operating in Africa, Australia, and on the U ni versity of California.
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Extra resources for Agriculture in Semi-Arid Environments
The main canals show an average grade of a little over a meter per kilometer, very close to the figure advocated for earth ditches today (Haury, 1976). That silting was a constant problem is evident, however, from the mounds of silts that were removed from the canals in antiquity. In all probability, the Hohokam of Snaketown found it necessary to leach the salts from their fields as arid land irrigators do today. Had they not mastered this Ancient Agricultural Systems in Dry Regions 31 problem, it is doubtful that the village could have survived for a millennium and a half.
1 The Hohokam The agricultural system of the Hohokam has been studied in perhaps the greatest detail. The Hohokam were the master irrigators of the Gila and Salt river valleys of Arizona. Recent work at Snaketown, one of the largest Hohokam villages (Haury, 1976), reveals that the roots of the culture probably lie in a direct migration from Mexico. C. Throughout the more than 1500 years of occupation, the major crop was maize, and the common bean (Phaseolus vulgaris) was grown from about the time of Christ.
The tepary bean (P. ), and probably the bottle gourd (Lagenaria siceraria) were also grown, but their dating is less certain. Some of the irrigation canals of the Hohokam were of large proportions. Woodbury (1960) reported that the main canals at Pueblo Grande were traceable for up to 15 km and were as much as 3 m deep and 11 m wide. D. At Snaketown none of the canals was this large. The earliest main canal was broad and shallow, but they took on a narrower and deeper profile over time. Work at Snaketown has revealed the details of how smaller canals or ditches branched off from the main canals.
Agriculture in Semi-Arid Environments by Anthony E. Hall