Environmental Engineering Reference
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term means that agree closely with the working-day aver-
age: feeding 150 MJ during 140-160 working days and
90 MJ during the rest of the year gives a daily mean of
110-120 MJ. Calculating annual requirements is more
complicated; usually only about two-thirds of animals
worked, and there was a mixture of draft species, most
of them of lesser working capacities and needs.
Rather than preparing hypothetical accounts of
possible requirements, I offer two detailed calculations
for the two extremes of traditional farming: the United
States in 1910 (dependent on horse and mule farming
energized by lavishly feeding grain and good hays), and
China in the early 1950s (the world's largest traditional
agriculture powered by more than 50 million oxen,
horses, water buffalo, and donkeys).
In 1910 there were 24.2 million horses and mules on
U.S. farms and only 1,000 small tractors; eight years
later, horse numbers peaked at 26.7 million but there
were already 85,000 tractors and 89,000 trucks. I assume
two-thirds of all animals working and eating a standard
ration of 110 MJ/day; for the other six months and for
other animals, I assume maintenance feeding. The result:
an annual requirement of about 50 Mt of feed, equiva-
lent (with average yields of 1.5 t/ha) to some 35 Mha.
USDA (1959) arrived at 29.1 Mha, or 22% of the
nation's harvested area in that year, a very close agree-
ment in approximations of this kind. Thus 20%-25% of
farmland was needed to feed the country's working ani-
mals (the addition of horses and mules in cities and
industries increased the area by some 15%).
The Chinese could not afford to devote 20% of their
land to feeding their draft animals. In the early 1950s,
before they started making small-sized and walking trac-
tors, the average weight of their draft animals was only
about 400 kg per adult, maintenance requirements were
about 60 MJ/day of digestible energy, or (given a high
shares of roughage) at least 80 MJ of gross feed energy.
Typical workday needs were about 125 MJ. With 140
days worked on average by two-thirds of the animals
and concentrate feeds accounting for just 25% for work-
ing animals and 10% for other animals (the rest being
roughage from grazing, hay, and other crop residues),
the country needed only about 20 Mt of grain feeds.
That would have equaled a bit more than 10% of all
unprocessed cereal harvests, but because the Chinese fed
their animals a large portion of their grain-milling resi-
dues (for example, between 50% and 75% of wheat bran)
and oil cakes whose total output at that time amounted
to over 20 Mt/year, no more than about 8 Mt of
unmilled grain was needed for all draft animals, claiming
just about 7% of all available farmland.
A U.S. horse thus needed at least 1.2 ha, whereas a
Chinese draft animal claimed only 0.13 ha, nearly a 1-
OM difference, resulting from a combination of smaller
sizes, less work, and poorer feeding in China. The gap
was primarily a matter of farmland availability. In 1910,
the United States had about 1.5 ha per capita and China
in the early 1950s merely 0.16 ha per capita. India's draft
animals were even less demanding, but M. Harris (1966)
went too far when he concluded that India's people
and cattle did not compete for crops. Fodder crops
accounted traditionally for about 5% of India's farm-
land, with the ratio as high as 10%-20% in the north
and northwest (Heston 1971). If only half of this had
been fed to working bullocks, the nationwide average
of farmland claimed by each animal would have been
at least 0.06 ha in the 1970s, roughly half of China's
rate.
With traditional dryland grain harvests not surpassing
1.3 t/ha, these land demands translate to preempting
