66 PRODUCTIVE FARMING 



fine soil made with a rake, called a dust mulch, will have 

 the same effect in keeping garden soils moist during dry 



FIG. 37. Spike-toothed harrow, producing a dust mulch in a peach orchard. 



(Experiment Station, N. J.) 



weather. A dust mulch can be made with a fine-toothed 

 harrow or weeder over a large field very rapidly (Fig. 37). 



REVIEW. 



1. Name the three forms of water in soils. 



2. Which form is most useful to growing plants? 



3. How can we determine the amount of capillary water in a soil 

 sample? 



4. How does free water in soil help the farmer? 



5. Under what circumstances is the free water harmful? 



6. What becomes of the moisture taken up by a growing crop? 



7. Describe the movement of capillary moisture in soils? 



8. What are pore spaces in soils? 



9. What kinds of soil have the largest pores? 



10. In what soils is the capillary movement of moisture most rapid f 

 What is the effect of rolling the loose soils? 



11. What soils hold the most capillary moisture? 



12. What kind holds the least? 



13. Suppose humus soil and sandy soil were mixed, what would be 

 the effect on their moisture-holding powers? 



14. What is a dust mulch? How made? 



15. What is the effect of a dust mulch? 



Reference. Dry Farming, by Widtsoe. 



