Dry-Farming : A System of Agriculture for Countries under a Low RainfallWidtsoe, John Andreas
Science
Dry-Farming : A System of Agriculture for Countries under a Low Rainfall
Widtsoe, John Andreas
Dry farming
An important and unique demonstration of the possibility of bringing
crops to maturity on the moisture stored in the soil at the time of
planting has been made by Alway. Cylinders of galvanized iron, 6
feet long, were filled with soil as nearly as possible in its
natural position and condition Water was added until seepage began,
after which the excess was allowed to drain away. When the seepage
had closed, the cylinders were entirely closed except at the
surface. Sprouted grains of spring wheat were placed in the moist
surface soil, and 1 inch of dry soil added to the surface to prevent
evaporation. No more water was added; the air of the greenhouse was
kept as dry as possible. The wheat developed normally. The first ear
was ripe in 132 days after planting and the last in 143 days. The
three cylinders of soil from semiarid western Nebraska produced 37.8
grams of straw and 29 ears, containing 415 kernels weighing 11.188
grams. The three cylinders of soil from humid eastern Nebraska
produced only 11.2 grams of straw and 13 ears containing 114
kernels, weighing 3 grams. This experiment shows conclusively that
rains are not needed during the growing season, if the soil is well
filled with moisture at seedtime, to bring crops to maturity.
What becomes of the rainfall?
The water that falls on the land is disposed of in three ways:
First, under ordinary conditions, a large portion runs off without
entering the soil; secondly, a portion enters the soil, but remains
near the surface, and is rapidly evaporated back into the air; and,
thirdly, a portion enters the lower soil layers, from which it is
removed at later periods by several distinct processes. The run-off
is usually large and is a serious loss, especially in dry-farming
regions, where the absence of luxuriant vegetation, the somewhat
hard, sun-baked soils, and the numerous drainage channels, formed by
successive torrents, combine to furnish the rains with an easy
escape into the torrential rivers. Persons familiar with arid
conditions know how quickly the narrow box canyons, which often
drain thousands of square miles, are filled with roaring water after
a comparatively light rainfall.
The run-off
The proper cultivation of the soil diminishes very greatly the loss
due to run-off, but even on such soils the proportion may often be
very great. Farrel observed at one of the Utah stations that during
a torrential rain--2.6 inches in 4 hours--the surface of the summer
fallowed plats was packed so solid that only one fourth inch, or
less than one tenth of the whole amount, soaked into the soil, while
on a neighboring stubble field, which offered greater hindrance to
the run-off, 1-1/2 inches or about 60 per cent were absorbed.
Public-domain text, read in full here on John Shaqi.
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