Environmental Engineering Reference
In-Depth Information
At that time Egypt's total cultivated land was about
2.7 Mha, and assuming 90% of it was planted with
grains yielding no less than 900 kg/ha, the country pro-
duced (with 25% reserved for seed and 10% storage loss)
about 1.5 times as much food as it needed for its nearly 5
million people and became the Roman empire's largest
food surplus area. After centuries of decline and stagna-
tion only perennial irrigation (introduced after 1800)
boosted the multicropping index. By the mid-1920s it
surpassed 1.5, and the still basically traditional farming,
but one already helped by inorganic fertilizers, was feed-
ing six people from every hectare of cultivated land (Wa-
terbury 1979).
China, although far from immune to turmoil and stag-
nation, was a considerably more innovative civilization
than Egypt. Chinese contributions to the art of irriga-
tion, ranging from the invention of the square-pallet
chain pump to extensive regional irrigation systems,
have been outstanding. Other improvements included
the horse collar harness and, about a millennium earlier
than in Europe, an integrated dryland cultivation tool
complex consisting of iron moldboard plow, multitube
seed drill, and various horse-drawn hoes and ridgers for
effective weeding. This traditional farming, able to sup-
port the world's largest culturally cohesive populations,
was richly documented in classical Chinese writings. It
survived largely intact until the 1950s, which afforded an
outstanding opportunity for reliable quantification of its
operations (Buck 1930; 1937; F. Bray 1984; Shen 1951;
Perkins 1969; Ho 1975).
Intensive multicropping, extensive recycling of organic
wastes, and widespread irrigation have been the hall-
marks of traditional Chinese farming, but none of these
practices is truly ancient. Clear evidence of manuring
dates only after 400
B
.
C
.
E
., and before the third cen-
tury
B
.
C
.
E
. there was no large-scale irrigation and little or
no double-cropping and crop rotation. Dryland millet in
the north and rice in the lower Yangtze (Chang) basin
dominated the first millennia of Chinese farming; pigs
were the most abundant and the oldest domestic animals.
More than 2,000 years of subsequent intensification
produced the world's most persistently self-sustaining
farming system, admirably complex yet heavily labor-
intensive and recurrently vulnerable. The typical size of
fields was only about 0.4 ha, and they were on average
just 600 m away from a farmhouse (Buck 1930; 1937).
Nearly half (47%) of farmland was irrigated, 25% ter-
raced, 95% cropped (buildings, ponds, roads, and graves
covered the rest). Just over 90% of cropped land was
in grains, about 4% in sweet potatoes, 2% in fibers, 1% in
vegetables.
The second survey counted an astonishing 547
cropping systems in 168 localities. Recycling of organic
wastes was the norm; dryland cereal yields were between
900 kg and 1400 kg, rice harvests up to 3.5 t/ha. The
average farm family of six people put in 275 10-h days of
labor measured in adult work units. Crops claimed the
bulk of draft labor (90% for rice, 70% for wheat); manual
tasks were more evenly divided among tillage, cultiva-
tion, and harvesting. Except for plowing and harrowing,
Chinese fieldwork relied on human labor, and because
oxen and water buffalo were fed hardly any grain, energy
returns can be calculated by using only human labor
budgets. Food energy returns (harvested energy/labor
energy) were around 25 for staple grains and sweet pota-
toes, about 40 for corn, 15 for pulses, and 10 for plant
oils. Virtually all edible crop harvests were consumed di-
rectly; the grains provided 90% of all food energy.
Repetitive diets dominated by wheat and millet flour,
rice, cornmeal, beans, sweet potatoes, and cabbage, with
