WAX-SEAL METHOD FOR DETERMINING WILTING COEFFICIENT. 



17 



The means of the determinations given in Table II show that in 

 the interval between wilting and death the plants reduced the soil 

 moisture 0.7 per cent, or to 92 per cent of the moisture content at 

 the wilting point. The loss from the dying plants in the constant- 

 temperature room was somewhat less, due to a smaller saturation 

 deficit. 



Another similar series of determinations was made for Kubanka 

 wheat and for water cress, except that the observations were ex- 

 tended to include the period following the death of the plants. The 

 results are given in Table III. 



Table III. — The water content of the soil in sealed pots at the wilting point, at the death 

 point, and at a later period for Kubanka wheat and for water cress. 



Designation of pot. 



Wilting 

 point. 



Time 

 interval 

 in days. 



Death 

 point. 



Time 

 interval 

 in days. 



Final 

 per cent. 



Kubanka wheat: 



4 



7.0 

 7.9 

 7.0 

 6.6 

 7.1 

 7.8 

 6.9 

 7.3 

 8.0 

 7.3 



28 

 25 

 25 

 19 

 27 

 27 

 19 

 27 

 27 

 27 



5.2 

 5.9 

 5.5 

 6.4 

 5.9 

 6.9 

 5.9 

 6.6 

 6.9 

 6.2 



126 

 126 

 126 

 126 

 134 

 134 

 126 

 134 

 37 

 134 



3.1 



6 



2.6 



7 



3.5 



8 



4.9 



9 



4.8 



10 



5.9 



11 



4.3 



12 



5.7 



13 



6.1 



14 



4.9 









7.3 



± .10 

 ± .33 





6.2 

 ± .12 

 ± .39 





4.6 











Probable error of single observation 

















Water cress: 



1 



7.6 

 7.8 

 7.7 

 6.5 



7 

 7 

 7 

 10 



6.0 

 6.5 

 6.3 



5.5 



51 

 129 

 129 

 119 



4.6 



2 



2.4 



3 



4.3 



5 



4.2 







Mean 



7.4 





6.1 





3.9 











The plants were grown in sealed pots containing about 250 grams 

 of soil. Column 2 of the table gives the water content of the soil 

 corresponding to the wilting of the plants. Column 3 gives the num- 

 ber of days intervening between the wilting and the death of the 

 plants, at which time the moisture content of the soil had been 

 materially reduced, as shown in column 4. A still greater loss of 

 water occurred during the subsequent period, at the end of which 

 the moisture content of the soil had been reduced to the point indi- 

 cated in column 6. The mean moisture content of the soil at the 

 death point of Kubanka wheat had been reduced to 85 per cent of the 

 water content at the wilting point, while the mean soil-moisture con- 

 tent at the end of the experiment was only 63 per cent of that at the 

 wilting point. An even greater reduction occurred in the pots con- 

 taining the water cress. 



It is evident, then, from the data already presented that water is 

 being steadily removed from the soil by dying or dead plants and 

 8477°— Bui. 230—12 2 



