DEVELOPMENT AND ACTIYITIES OF ROOTS OF 

 CROP PLANTS. 



INTRODUCTION. 



Some of the most fundamental problems of plant ecology in its mani- 

 fold relations to crop production are those concerned with root development 

 and the relations of roots to soil and subsoil. An exact knowledge of the 

 root development of crop plants, of their position, extent, and activity as 

 absorbers of water and solutes at various stages of growth, is of paramount 

 inportance to a scientific understanding of plant production. Moreover, a 

 knowledge of modifications produced by variations in the subterranean 

 environment, whether due to such natural conditions as excessive water- 

 content or drought, or to tillage or fertilizers, is of no less importance. In 

 fact, many processes and practices will cease to be empirical and come to 

 be exact only when the relation of roots to soil is recognized as having funda- 

 mental value. 



The importance of root extent and distribution in a study of soil-moisture 

 is patent. These should determine not only what depth of sample should 

 be used, but also the maximum depth to which samples should be obtained. 

 The time, method, and amount of the appUcation of water for irrigation 

 studied in the Hght of root development furnish a rich and varied field for 

 investigating problems of the greatest scientific and economic importance. 

 Conversely, the proper drainage of swamps and boglands for pastures, 

 meadows, afforestation, or for cultivated crops, should be determined with 

 reference to root relations. (C/. Howard, 1916, 1918; Osvald, 1919.) 



A knowledge of root systems is again fundamental in the scientific appUca- 

 tion of fertihzers. In fact, it should furnish the criterion not only for time 

 and amount, but also in regard to the manner and depth of such appHcation. 

 In securing soil samples for chemical analysis, root extent and activity at 

 different levels should determine the depth at which the samples are taken. 

 Moreover, it will clear up the whole problem of the relative values that should 

 be placed upon chemical analysis of surface soil and subsoil. 



Preliminary studies of root systems of native plants in soils impregnated 

 with alkaU point out clearly that the adaptation of plant to habitat is often 

 largely one of root distribution above or below the layers of greatest salt 

 concentration. With adequate knowledge of the variabiUty of the root 

 systems of different varieties of crop plants, selection of those most suitable 

 for cultivation in such areas should be less difficult. 



In problems of crop production on acid soils, if attacked from the more 

 modern and logical viewpoint of lime requirement of the plant, rather than 

 that of the soil, the root system again plays a decisive role. The Hme require- 

 ment of the plant is determined not only by its lime-content and rate of growth, 

 but especially by its feeding power for Ume. The latter is in proportion to 

 the character and extent of the root system, the internal acidity of roots, 



