80 BULLETIN 355, U. S. DEPARTMENT OF AGRICULTUEE. 



LESSON XI. SOIL ADAPTATION TO CROPS. 



Relations hetween soils and crops (Ref. No. 4, pp. 291-306; or No. 

 10, pp. 232-256). — There are a number of important relations between 

 the character of the soils and the crops to which they are adapted. 

 The climate also has an important effect, not only directly on the 

 crop, but indirectly through the soil. Certain crops require long 

 growing seasons between frosts, and they are seriously injured by a 

 freezing temperature. The amount of rainfall is likewise an impor- 

 tant consideration. Some crops growing very early in the spring 

 and maturing in the early summer require much less water than do 

 those growing during the longer summer season when evaporation, 

 not only from the plant itself, but also from the soil, is at the maxi- 

 mum. Moreover, there is an intimate relation between the water- 

 holding capacity of the soil and the character of the rainfall upon 

 crop production. Soils which have a fine texture and deep subsoil 

 are able to retain nearly enough moisture from the early spring rains 

 to mature crops growing through the summer, provided sufficient 

 care is taken to develop a mulch so as to lessen the surface evaporation. 

 Again, there is a close relation between the texture of the soil and 

 the conditions affecting the quality of the crop, and also the use of 

 tools both in planting and harvesting. All of these matters must 

 be carefully considered. The following paragraphs are intended 

 only as suggestions on some of the more important of these relations 

 as they affect some of the more important crops. Crops may, for 

 this purpose, be grouped into three classes, (1) tilled crops, (2) 

 cereals, and (3) grasses and legumes. 



SOILS ADAPTED TO TILLED CROPS. 



While tilled crops, such as corn, potatoes, sugar beets, cabbage, etc., 

 differ among themselves in many important respects, they are alike 

 in that they permit tillage of the soil to kill weeds and for the develop- 

 ment of a soil mulch to lessen evaporation of water. Most of them 

 also grow through the long summer season, making a large growth, 

 which requires abundant supplies of all the essential elements of 

 plant food. 



Corn (Ref. Nos. 7, p. 576; 10, p. 243). — Corn may be grown in any 

 section having a season of 100 days free from frost, but the larger 

 yielding varieties require 120 days, and a maximum growth of this 

 crop occurs only in sections having relatively warm nights. Higher 

 altitudes are therefore not suitable, since they are characterized by 

 cool night temperatures. The larger quantity of water used by 

 heavy crops of corn can be supplied only by soils having large water- 

 holding capacity or in sections where the summer rainfall is relatively 

 large. Hence the best results with this crop are secured on com- 



