'IRAQ AND THE PERSIAN GULF' [‎291v] (585/862)

450 IRRIGATION, AGRICULTURE, AND MINOR INDUSTRY
loams. The stronger loams, which bake hard after drying, are the
most frequent. Some very sandy soils occur, consisting of coarse and
fine sands with very little silt; these are useless except for the pro
duction of scanty pasturage. Generally soils are very rich in calcium
carbonate (up to 20%), well supplied with potash and adequately
with phosphates, but are generally deficient in nitrogen. Soluble
salts are always present, and accumulation of alkali takes place in
soils which have been long under cultivation. This is mainly due to
the rise of alkalis from the subsoil as a result of bad drainage of
irrigated lands, and also to the concentration of salts in the irrigation
water or the continuous evaporation of seepage water from rivers
and canals. Well-drained lands and lands not long cultivated contain
only a minute percentage of toxic alkali salts, of which the chief
are the chlorides of calcium, magnesium, sodium, and their sul
phates; sodium carbonate or ‘black alkali’ is rare or non-existent.
Soil salination is generally worse on lands watered by flood than on
those watered by lift, as flood water is used more extravagantly than
lift. The use of silt-laden water simply for fertilization is a particu
larly common cause of salination. Experiments in soil-washing have
shown that in some areas soils wash clear of alkalis readily if drainage
can be provided. As much as 62-7 tons per acre of soluble salts have
thus been cleansed away from experimental plots.
In the Assyrian plains of northern Iraq the soils are also of alluvial
origin though of greater geological age. They are generally more
friable than in the south and seldom suffer from salination even under
irrigation, because there is natural drainage.
Tools and Methods
The agriculture of Iraq is primitive both in its tools and its methods.
The plough, the principal and almost the sole cultivating implement,
is little more than a wooden prong shod with iron and harnessed to
a beast; there is no curved ploughshare, and a very narrow and shallow
furrow is driven (photos. 170, 172). The plough is extremely light,
and easily dismantled and transported from plot to plot, and is drawn
by donkey, mule, horse, or cattle. Ground that is too broken or too
intersected by watercourses is cultivated by hoe and mattock or by
spade. Reaping is done by the slow and tiring hand-sickle. For
threshing there are two methods: the corn may simply be trod by
animals tied by a bridle to pegs in the ground, or else the threshing
plough of the Middle East is used, called hulwa in southern Iraq
and jar jar in the north (photo. 171). This resembles a sled with