122 Commercial Gardening 



cracked condition. The weeds also harbour the grubs of various fruit 

 and vegetable pests that sleep in security until nature calls them forth 

 again to plague the grower who despises knowing anything about 

 them. The prevalence of weeds, therefore, in any garden indicates a 

 penny-wise saving in labour and a pound-foolish extravagance in other 

 directions. 



The Upward Movement of Moisture in Soils Capillary Attraction. 

 We have seen that according to the nature of the soil, and the depth 

 to which it has been cultivated, large or small quantities of water are 

 absorbed and sink to certain depths. If, however, the water were to sink 

 so low as to leave no moisture at all in the root region, plant growth would 

 be impossible. We know, however, that in all well-cultivated soils there 

 is generally a good supply of moisture available, even in the hottest and 

 driest of summers. Whence does it come? Obviously from the supplies 

 deep down below the surface. 



The soil may be looked upon as a kind of sponge. It will not only 

 soak in water from overhead, but also from beneath. Consequently we 

 find that when no rain falls, and the weather is hot and dry, a good deal 

 of moisture is rising from the ground. This is easily proved by placing 

 a piece of glass on the surface of the soil. After a short time it will be 

 noticed that the under surface is covered with moisture that could not 

 escape through the glass. If we dig down for 2, 3, or several feet 

 we see no actual water, but we notice that the soil becomes more moist 

 the deeper we go, until eventually we should reach water. It is evident, 

 therefore, that the moisture rises upwards, and passes from particle to 

 particle of the soil. A kind of invisible stream of vapour is constantly 

 rising from the lower regions, and is given off from the surface of the soil 

 into the atmosphere. This upward stream of moisture or vapour is caused 

 chiefly by the evaporation that is going on from the surface owing to the 

 heat of the sun. The top layer of soil particles are the first to lose their 

 moisture, then the next layer, and so on downwards, until, if no rain falls, 

 and the reserve of water beneath fails, the soil becomes as " dry as dust ", 

 and the crops collapse. 



The ascent of water or moisture in the soil is much the same as it 

 would be in a sponge or in a slab of salt or sugar. The lowest layers in 

 direct contact with the liquid are more saturated than those above them, 

 and the particles composing the different layers have the power of drawing 

 moisture from those immediately below them. According to the nature of 

 the soil this power of raising the water from below upwards varies greatly. 

 Thus, in a heavy clay soil, where the particles are closely pressed together, 

 it is very difficult for the moisture to rise freely. The surface layers lose 

 their moisture after a time, and then, because they are unable to obtain 

 a supply from those beneath, the surface begins to shrink and crack and 

 form fissures in all directions. 



In a sandy soil, where the particles, although closely packed, are no< 

 cemented together as in clay, moisture is given off very freely, and the 



