Date Percentage of water in the
Untouched soil Soil hoed once Soil hoed three
weekly times weekly
1910
June 4th 21.1 19.5 17.9
June 20th 14.7 16.0 16.0
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.
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