GROWING PLANTS WITHOUT SOIL 

 FOR EXPERIMENTAL USE 



By M. Blankendaal, R. H. Hodgson, D. G. Davis, R. A. Hoerauf, and R. H. Shimabukuro, Metabolism and Radiation 

 Research Laboratory, North Central Region, Agricultural Research Service, United States Department of Agriculture, Fargo, N. Dak. 



Crop plants have been grown in soil for cen- 

 turies. With the discovery of the many chemical 

 substances in the soil, methods were developed for 

 growing plants without soil. They were grown in 

 such media as cracked rock, vermiculite, and 

 coarse sand — all inherently very low in essential 

 plant nutrients. The nutrients were supplied dis- 

 solved in water. This allowed researchers to regu- 

 late the kinds and amounts of nutrients available 

 to the plant. However, because of the adhesive 

 properties of the supporting media and because 

 they could not always be relied on as purely 

 inert materials, it was often necessary to use 

 hydroponics or nutrient solution culture. 



The original technique of growing plants hydro- 

 ponically (11) l is still widely used (7) and has 

 proved satisfactory in many instances. Many 

 plants can be grown from seed to seed without 

 ever coming in contact with soil. Some of the 

 techniques used to grow plants without soil are 

 described in detail (5, 7, 8, 9, 12). For a historical 

 sketch of the development of the water culture 

 method, see references 8, 9, and 11. 



Plants grown in soilless culture have the advan- 

 tage of a consistent supply of moisture and 

 nutrients, resulting in steady growth (2). How- 

 ever, plants grown in solution culture may require 

 more intensive care than those grown in soil to 

 insure adequate moisture and to prevent develop- 

 ment of nutrient toxicity or deficiency symptoms. 



Much of the current research in experimental 

 plant biology requires highly uniform plants. This 

 quality of plant material is best grown under con- 

 ditions in which the environment is carefully 

 manipulated. Some research groups have centered 



1 Italic numbers in parentheses refer to Literature Cited, 

 p. 16. 



their efforts on determining the environmental 

 conditions under which maximum plant growth is 

 achieved, with a view toward understanding the 

 factors that limit plant growth, determining maxi- 

 mum growth rates, and exploring the potential for 

 economical production of plants under controlled 

 conditions. 



In contrast, our objective has been to produce 

 vigorous, healthy, uniform plant material in 

 regulated environments for experimental purposes. 



This publication is intended for those with some 

 knowledge of plants who want to grow one or more 

 species for experimental purposes, for demonstra- 

 tions in schools, or for science projects where 

 limited facilities are available. Techniques and 

 equipment are described that are used at the 

 Metabolism and Radiation Research Laboratory, 

 Fargo, N. Dak., to raise crop and weed species in 

 the absence of soil for experiments in which pesti- 

 cides and their metabolites are applied to plants or 

 plant parts, often in radioactive form. Some of the 

 techniques have been adapted specifically for use 

 with radioactive tracers, where consideration must 

 be given to the absorptive properties of the 

 containers and their disposability or ease of 

 decontamination. 



The growth procedures described here can be 

 modified considerably to meet the facilities and 

 budget of others who attempt to use them. The 

 equipment is described here in some detail, but 

 this degree of sophistication is not essential for 

 growing plants, even for experimental purposes. 

 The ingenious experimenter may have to modify 

 the described techniques for his particular situa- 

 tion. For example, instead of a growth chamber, a 

 converted room or part of a laboratory may suffice. 

 We use vermiculite in many instances, but other 

 inert supports such as "Jiffy Mix" may have to be 



