June 27th 19.3 18.4 20.5

Remarks. June 4th; The weather is still cold and the summer has not
yet begun.

June 20th: Hot day following on some hot, dry weather.

June 27th: Rain had recently fallen.

When hoeing is done in the early part of the summer it dries the soil,
and the more frequent the hoeing the drier the soil (see June 4th
results). But later on, when the hot weather begins, the hoed soil
loses much less moisture than the untouched plot; the latter lost 6.4
per cent. in 16 days in the top six inches, whilst the soil hoed once
weekly lost 3.1 per cent., and the one hoed three times weekly lost
only 1.4; the two hoed soils are now equal, and are both moister than
the untouched soil. When more rain comes they get just as wet as the
others: hoeing does not prevent water from sinking in, but it does
prevent water from getting lost.

Our experiment has, therefore, shown us that hoeing makes a loose layer
of soil which shields the rest of the soil from the sun's heat, and
prevents it getting too hot or too dry. A hoed soil is cooler and
moister, and therefore better suited for the growth of plant roots than
an unhoed soil.

{90}

The mulch of straw or dried grass was found to have the same effect in
conserving the water as the loose layer of soil obtained by hoeing.
Some results were:--

Percentage of moisture in

Date Hoed soil Mulched soil

1910
Sept. 24th 19.6 20.7

[Illustration: Fig. 43. Cultivation and mulching reduce the loss of
water from soils]

These results are so important that some indoor experiments should be
made to furnish more proof. Fix up three inverted bell jars with corks
and bent tubes as shown in Fig. 43, fill all with dry soil well pressed
down, then add water carefully till it appears in the glass tubes.
Next day mark with stamp paper the level of liquid in each tube and
then leave one jar {91} untouched, carefully cultivate with a penknife
every two or three days the top quarter of an inch of the second, and
cover the third with a layer of grass. After a week notice again the
levels of the liquid and mark with paper; you find that the water has
fallen most in the untouched jar, showing that more has been lost from
this than from the jars covered with a mulch either of soil or of dry
grass.

A slate or flat stone acts like a mulch; if you leave one on the soil
for a few da