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Widtsoe, John Andreas, 1872-1952

"Dry-Farming : a System of Agriculture for Countries under a Low Rainfall"


A reason for variation in composition
It is possible to suggest a reason for the high protein content of
dry-farm crops. It is well known that all plants secure most of
their nitrogen early in the growing period. From the nitrogen,
protein is formed, and all young plants are, therefore, very rich in
protein. As the plant becomes older, little more protein is added,
but more and more carbon is taken from the air to form the fats,
starches, sugars, and other non-nitrogenous substances.
Consequently, the proportion or percentage of protein becomes
smaller as the plant becomes older. The impelling purpose of the
plant is to produce seed. Whenever the water supply begins to give
out, or the season shortens in any other way, the plant immediately
begins to ripen. Now, the essential effect of dry-farm conditions is
to shorten the season; the comparatively young plants, yet rich in
protein, begin to produce seed; and at harvest, seed, and leaves,
and stalks are rich in the flesh-and blood-forming element of
plants. In more humid countries plants delay the time of seed
production and thus enable the plants to store up more carbon and
thus reduce the percent of protein.


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