The Plant as Related to the Soil 51 



82. The Condition of the Soil has great influence on 

 the distribution of the roots. Where the surface layers 

 are moist the roots will grow freely in these layers, but 

 if dry spells come the plants will suffer more than plants 

 that have been growing on soils less favorably supplied 

 with moisture. This explains why it is best, in watering 

 lawns, to give them a heavy drenching rather than a 

 frequent sprinkling of the surface, so that the water 

 will soak down into the deeper layers. 



83. Grass-like Plants are without tap-roots. They 

 form a number of fine roots near the surface, and are 

 hence known as "surface feeders." Other plants, like 

 cotton, alfalfa, peanuts and beans, have strong tap-roots 

 that branch out in the lower layers of soil, and are for 

 this reason called "deep feeders." We must not conclude 

 from this that the small grains do not have deep-feeding 

 roots. Notwithstanding the small diameter of the root 

 branches, some of them penetrate the soil much below 

 the surface layers, as illustrated in Fig. 32. 



QUESTIONS 



1. What conditions of open-field culture are under our control? 

 2. What are the uses of soil to a plant? 3. What kinds of roots 

 grow in moist, fertile soils? 4. What kind in poor soil? 5. What is 

 an ideal soil for plants? 6. What conditions of soil particles prevent 

 the right supply of food? 7. What are the three general ways of 

 changing the texture of the soil? 8. When is a soil in good tilth? 



9. Why is it necessary for a plant to have a large root surface? 



10. What is the general rule as to the distribution of roots? 11. What 

 is the effect of moisture on the downward distribution of roots? 



12. Shall crops be tilled deep or shallow? Discuss this question. 



13. Why are the grasses called surface feeders? 14. Explain how 

 deep breaking of the soil makes a larger and better home for the 

 roots. 



