WATER-CULTURE METHOD HOAGLAND AND ARNON 475 



very different matter from producing crops for profit. The experi- 

 ence of the amateur gardener, whether he uses soil or the water-culture 

 method, is not adequate preparation for commercial crop production. 



USE OF PREPARED SALT MIXTURES 



Many amateurs have become interested in the purchase of mix- 

 tures of nutrient salts ready for use, and various individuals and firms 

 have offered for sale small packages of salt mixtures. Clearly a pre- 

 pared salt mixture does not obviate the difficulties which may be 

 met in growing plants in water culture. Recently, some firms^have 

 made highly misleading claims for the salt mixtures they sell. The 

 California Agricultural Experiment Station makes no recommenda- 

 tion with regard to any salt mixture, and the fact that a mixture is 

 registered with the California State Department of Agriculture, as 

 required by the law governing sale of fertilizers, implies no endorse- 

 ment for use of the product. The directions given later will help the 

 amateur to prepare his own nutrient solutions. 



COMPOSITION OF NUTRIENT SOLUTIONS 



Thousands of requests have been received by the California Agri- 

 cultural Experiment Station for formulas for nutrient salt solutions. 

 It is often supposed that some remarkable new combination of salts 

 has been devised and that the prime requisite for growing crops in 

 solutions is to use this formula. Now the fact is that there is no one 

 composition of a nutrient solution which is always superior to every 

 other composition. Plants have marked powers of adaptation to 

 different nutrient conditions. If this were not so, plants would not 

 be growing in varied soils in nature. We have already emphasized 

 in the historical sketch of the water-culture method that within certain 

 ranges of composition and total concentration, fairly wide latitude 

 exists in the preparation of nutrient solutions suitable for plant 

 growth. Many varied solutions have been used successfully by 

 different investigators. Even when two solutions differ significantly 

 in their effects on the growth of a particular kind of plant under a 

 given climatic condition, this does not necessarily mean that the same 

 relation between the solutions will hold with another kind of plant, 

 or with the same kind of plant under another climatic condition. 



Another point concerning nutrient solutions needs to be stressed. 

 After plants begin to grow, the composition of the nutrient solution 

 changes because the constituents are absorbed by plant roots. How 

 rapidly the change occurs depends on the rate of growth of the plants 

 and the volume of solution available for each plant. Even when 

 large volumes of solutions are provided, some constituents may be- 

 come depleted in a comparatively short time by rapidly growing 



