CHAPTER XXV. 



MEANS OF PROTECTION AGAINST DROUGHT AND 



FROST. 



SIMPLE AND PRACTICAL DEVICES. 

 " Saving is Earning." 



N most localities of the United States the gardener 

 rarely passes through a season without encountering 

 one or more longer or shorter periods of dry weather. 

 Sometimes these periods assume the aspects of a 

 serious drought, and the average crops of vegetables 

 and fruits are often greatly reduced by these period- 

 ically repeated occurrences. Irrigation is the 

 expedient most naturally thought of for meeting 

 such emergencies ; but as we have seen in the chapter treating on 

 that subject, artificial applications of water irrigation or sprink- 

 ling, etc. are useful only under rare conditions, and mere 

 sprinkling can never supplant the rains from the skies, in fact, 

 is often more hurtful than of benefit. But we are not left without 

 means of passing safely over any period of drought of reasona- 

 ble duration. 



PRECAUTIONS AGAINST DROUGHT. During the colder part of 

 the season, when the evaporation from the soil is slow, and the sup- 

 ply of moisture from the clouds abundant, the movement of the soil 

 water is chiefly downward, while during the summer evaporation 

 is usually much faster than rainfall, and necessarily the soil water 

 in the main moves upwards. In other words, the soil forms a 

 sort of reservoir that is filled every winter, and gives off its sup- 

 ply for the use of vegetation (and by evaporation) during the 

 growing season. If this reservoir is shallow, as in case of soils 

 resting upon an impervious clay stratum, the surplus is carried off 

 by surface wash, or in the drains, and the supply is liable to give 

 out when most needed ; but if deep, as in the case of a naturally 

 porous subsoil, or one loosened by subsoiling, the available water 

 supply is large, and not liable to become soon exhausted. It is 

 true that capillary action is also going on in the clay hard-pan, 

 but it is far too slow to satisfy the combined demands of surface 

 evaporation, and absorption by plant roots in a dry time. Hence 

 our first aim must be to secure depth of reservoir. It is essential 

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