128 FUNDAMENTALS OF FRUIT PRODUCTION 



Schreiner and Skinner""''' discuss this subject as follows: "Many writers in 

 agricultural literature seem to be under the impression that the only way that a 

 plant can get the nutrients from a solution is to use all the water it can in building 

 tissue and to lose the remainder by transpiration, so as to obtain the necessary 

 nutrients dissolved in the soil water or nutrient solution. In other words, that 

 the plant maintains a current of water entering at the root as the nutrient 

 solution and leaving the plant as pure water at the leaf surfaces, that is, by 

 transpiration or evaporation. From their arguments it follows that if a half 

 strength solution is presented to the plant it will have to take up and transpire 

 twice as much water to obtain the same nutrients. In other words, the plant 

 is supposed to absorb the mineral constituents in the same concentration as the 

 solution in which the roots bathe. This is, however, not in accordance with 

 the facts. The plant has greater difficulty in obtaining the mineral elements from 

 the weaker solution, but it does not accomplish this by expending the extra energy 

 involved in transpiring double the amount of water. 



"For instance, the loss of water from a 250-cubic centimeter [nutrient] 

 solution during this 3-day period is only about 10 per cent., whereas the analysis 

 of the solution after supplying this water showed the mineral nutrients to be 

 reduced from 80 to as low as 23.8 parts per million, or a decrease of 70 per cent. 

 It is obvious that the plants have taken the nutrients faster than the water, and 

 this under conditions of good growth. 



"Not only does the absorbing power of the root enable the plant to take more 

 nutrients per cubic centimeter of water absorbed than is contained in the same 

 volume of the soil solution, but it also enables the plant to obtain a different 

 ratio of the mineral nutrients for its use than exist in the nutrient solution. 



"These facts are extremely important, as they show that the absorbing power 

 of the plant is not regulated by the amount of transpiration, but rather by the 

 life processes within the plant and the requirements of these life processes." 



THE NUTRIENT REQUIREMENTS OF CROP AND FRUIT PLANTS 



Typical crop plants and typical deciduous fruits make distinctly 

 different demands upon the soil. For most crops the soil should not be 

 acid and the nitrogen requirement is relatively low. For most fruit 

 trees, soil acidity, unless very high, is not a factor of concern and the 

 demands for nitrogen are great. It is suggested that this more or less 

 characteristic difference which requires agronomists and horticulturists 

 to adopt correspondingly different attitudes on the problem of soil 

 productivity is connected with the different ecological habits of these 

 plants, together with the type of crop desired. Cereal crops in particular 

 are adapted to an early stage in ecological succession which has not 

 proceeded beyond an association where grasses are dominant. Humus 

 has not yet collected in great amount; hence, crops flourish in soils of low 

 acidity and require relatively little nitrogen (though they may do equally 

 well or better in soils abundantly supphed with it). Fruit trees belong to 

 a much later stage in an ecological succession which has reached an 

 association of forest trees and in which the character of the soil has 



