INFLUENCE OF SOIL AND PLANT ON WILTING COEFFICIENT. 33 

 Table XI. — Wilting coefficients of various soils for different plants — Continued. 



Soil and species or variety of plant. 



Coef- 

 ficient. 



Soil and species or variety of plant. 



Coef- 

 ficient. 



Soil No. 14 (clay loam). Moisture equiva- 

 lent 29.3— Continued. 



Tomato: Livingston's Golden Queen — 

 Do 



16.5 

 16.5 

 16.2 



Soil No. 14 (clay loam). Moisture equiva- 

 lent 29.3 — Continued. 



Mean for all determinations, soil No. 14. . 



17.1 

 ± .10 



Do... 



Probable error of single observation 



Soil No. 6 (clay loam). Moisture equiva- 

 lent 30.2. 



Wheat* Kubanka G I 1440 



± .56 









16.4 









Squash: Yellow Summer Crookneck 



16.6 



16.3 

 16.9 



Wheat: Kubanka, G. 1. 1440 



17.3 

 17.3 

 17.8 

 18.3 

 15.4 

 16.5 

 17.8 

 17.4 

 17.4 

 16.0 



Do 



Do 



Do... 



16.8 



Do 



Do 



16.4 



Do 



Do 



15.5 



Do 



Do 



15.7 



Do 



Do 



17.3 



Do 



Do 



15.6 



Do 



Do 



16.0 



Do 



Do 



16.0 



Do 



Do 



16.2 





Do 



16 3 



Mean 



17.1 

 ± .22 

 ± .68 



Do 



16.7 





Do 



16.2 



Probable error of single observation. 



Do 



16.3 



Do 



16 7 





16.4 

 17.9 

 17.7 



18.8 

 17.6 



Mean for all determinations, soil No. 6. . 







16.3 





± .08 





Probable error of single observation 



± .33 











RELATIVE INFLUENCE OF THE SOIL AND THE PLANT ON THE 

 WILTING COEFFICIENT. 



An inspection of the results given in Table XI makes the great 

 influence of the soil texture upon the wilting coefficient at once 

 apparent. The mean wilting coefficient of the different soils used 

 ranges from less than 1 per cent to over 16 per cent. The range is 

 even greater for extreme types of soil, as we shall show later, the 

 wilting coefficient of the heaviest clays being as high as 30 per cent. 

 In other words, the moisture content of the heaviest clay soils when 

 reduced to the point where plants wilt is more than 30 times as great 

 as in dune sands under similar conditions. Plants will wilt in the 

 heaviest clay soils when the water content is greater than sand soils 

 can possibly hold if drainage is provided. It is thus seen that the 

 great differences in the wilting coefficient encountered as we go 

 from soil type to soil type are due simply to the difference in the 

 moisture retentiveness of the soils. 



On the other hand, the results given in Table XI show that the 

 use of different plants as indicators of the wilting point produces only 

 a relatively small change in the wilting coefficient of a given soil. 

 Representing the mean value of the wilting coefficient of a given 

 soil by 100, a range from 95 to 105, approximately, would result 

 from the use of different plants as indicators. The influence of the 

 8477°— Bui. 230—12 3 



