474 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 8 



production under outdoor conditions. Before planning any invest- 

 ment in this field, the most careful consideration should be devoted 

 to the economic and technical factors concerned. It seems improbable 

 in view of the present cost of a commercial water-culture installation, 

 that crops grown by this method could compete with cheap field- 

 grown crops. Recently, popular journals have discussed a project 

 for growing vegetables in tanks of nutrient solution, on Wake Island, 

 in Mid-Pacific, to supply fresh vegetables (which constitute only a small 

 proportion of the total food requirements) for the inhabitants of the 

 island and for passengers of the clipper airships. This, however, is a 

 special case, and there is no reason to assume that it has any general 

 agricultural significance. 



GROWING OF PLANTS IN WATER CULTURE BY AMATEURS 



Most numerous among the inquiries for information about the 

 water-culture method are those from persons who wish to grow plants 

 in this way as a hobby. These persons usually seek exact directions 

 as to how to proceed to carry on water cultures. For reasons, which, 

 we hope, will be made clear through reading this circular, it is not 

 possible to describe a general procedure that will insure success. 

 Many technical difficulties may be met: character of water, adjust- 

 ment of acidity of the solution, toxic substances from tanks or beds, 

 uncertainty as to time for replenishing salts in the nutrient solution, 

 or for changing the solution, and the like. 



Why, it may be asked, do not most of these technical difficulties of 

 the water-culture method arise when plants are grown in soil? Because 

 in a naturally fertile soil, or one which can be made fertile by simple 

 treatment, there occurs an automatic adjustment of many of the 

 factors determining the nutrition of the plant. 



Some amateurs have recently reported results satisfactory to them- 

 selves, with certain kinds of plants grown in water culture, and similar 

 success can presumably be achieved by others through a fortunate 

 combination of nutritional and climatic conditions. Yet without 

 knowledge and control of the factors involved, no assurance can be 

 given that success with one kind of plant at one season can be con- 

 sistently repeated with other kinds of plants, or at other seasons. 

 True, not every successful gardener has a thorough training in plant 

 and soil science, nor can such training, by itself, always insure suc- 

 cess in gardening. However, since the growing of plants in soil is 

 one of the oldest occupations of mankind, the gardener can often 

 obtain guidance based on a rich store of accumulated experience. 

 Such experience is lacking for the growth of plants by the water- 

 culture method. 



In any case, growing of plants as a hobby, in either soil or culture 

 solution, without regard to cost of labor and materials, is, of course, a 



