tions more than five or six hundred feet above sea level are, in
England, as a rule, too bleak and {80} exposed for the ordinary
cultivated crops. Such land is, therefore, either grass land,
moorland, downland or woodland.

The roots of plants are living and require air. The soil must not be
trodden too hard round them or air cannot get in, nor can it if too
much water is present.

Grass can put up with more water and less warmth than most cultivated
crops.

[Illustration: Fig. 39. Rough grass pasture near the river, above that
is arable land and still higher is woodland]

Instances of these facts may be found in going down any hill 500 ft. or
more in height: the top is usually wood or waste, being too cold for
crops, below this may come grass land, lower still arable land. It is
both warmer and moister in the valley (since water runs down hill), and
so we can account for the proverbial fertility of valleys. But just
near the river, if there is one, the ground may be too wet for crops,
and therefore grass is grown. Clay land that is rather too wet to
plough is usually left in grass.

{82}

CHAPTER IX

CULTIVATION AND TILLAGE

Apparatus required.

_Plot experiments, hoeing and mulching. Thermometer. Soil sampler
(Fig. 42, p. 88). This tool consists of a steel tube 2 in. in diameter
and 9 in. long, with a slit cut along its length and all the edges
sharpened. The tube is fixed on to a vertical steel rod, bent at the
end to a ring 2 in. in diameter, through which a stout wooden handle
passes. It is readily made by a blacksmith._

Farmers and gardeners throughout the spring, summer and autumn, are
busy ploughing or digging, hoeing or in other ways cultivating the
soil. Unless all this is well done the soil fails to produce much; the
sluggard's garden has always been a by-word and a reproach. In trying
to understand why they do it we must remember that plant roots need
water, warmth and air; if the soil is too compact or if there is too
much water the plant suffers, as we have seen.

[Illustration: Fig. 40. After harvest the farmer breaks up his land
with a plough and then leaves it alone until seed time]

One great object of cultivation is, therefore, to prevent the soil
being too compact and too wet. After the harvest the farmer breaks up
his ground with a plough and then leaves it alone till seed time (Fig.
40). A gardener does the same thing with a fork in his kitchen
garden--he