62 



WILTING COEFFICIENT FOR DIFFERENT PLANTS. 



Fig. 8.— Chart showing the daily moisture detenrhhations in 1-foot sec- 

 tions to a depth of 6 feet in a soil on which Kubanka wheat was grow- 

 ing. The heavy horizontal straight lines on the chart represent the wilt- 

 ing coefficient as calculated from the moisture equivalent independently 

 of the moisture determinations or of field observations. The wheat 

 wilted on July 1 and was cut July 22. The graphs show that the mois- 

 ture curves are either coincident with or below the wilting coefficient on 

 July 1, indicating that there was no longer moisture available for growth. 

 The continuous loss of water from the soil after wilting takes place is 

 also shown. 



230 



June 26. Wheat well 

 headed; just about to 

 wilt. 



June 27. In good con- 

 dition. 



Note.— Weather cool 

 and cloudy during June 

 26, 27, and 28. 



July 1. Beginning to 

 wilt. 



July 4. Almost dry. 



July 7. Almost dead. 



July 8. About two- 

 thirds of the stem is 

 dry. 



July 9. Leaves nearly 

 all dead. 



July 10. No evidence 

 that the plants are get- 

 ting water. 



July 11. Very dry. 



July 19. Extremely 

 dry. 



July 22. Dead ripe; 

 harvested. 



The heavy hori- 

 zontal straight line 

 shown in connec- 

 tion with the deter- 

 minations for each 

 foot-section repre- 

 sents the calculated 

 value of the wilting 

 coefficient. This 

 value was calcu- 

 lated by means 

 of the relationship 

 already established 

 from moisture- 

 equivalent deter- 

 minations made 

 upon a composite 

 of all the samples 

 taken in that sec- 

 tion. It is thus 

 entirely independ- 

 ent of any direct 



