lo May, 1912.] IiifliH'iiCi of Soil Moisture upon Xiirificafinu. 



neck il inches, and of 500 c.c. capacity. Sufficient tapping was given to 

 make the soil compact. A mark was placed on the bottle at the soil level, 

 the .soil was replaced by water to the same mark, and from the weight of 

 water required the api)arpnt S.G. of the soil was determined. From this 

 and the real S.G. as found by the disi)lacement method, the porositv of 

 the soil, and from this the total water-holding capacity was found bv 

 calculation. There were two sets of experiments in consecutive periods, 

 using about 100 bottles each. In the first experiments water was added to 

 bring the original soil moLsture up to 10, 20, 30, 40, 50, 60, and 70 per 

 cent, of its total water-holding capacity in different bottles. In the second, 

 the steps were 10, 20, 30, 50, 70. and 90. All the bottles were marked to 

 the same volume, and the same weight of dry soil was used in everv. 

 case. 



Before charging the bottles, tlie weighed soil was thoroughly mixed 

 with its proper quantity of water in a Wedgewood mortar. One-half of 

 the bottles got water only, the other half got 5 c.c. standard ammonium 

 sulphate solution in their water. After filling, the bottles were placed in a 

 dark cupboard in the laboratory, and the temperature of the cupboard was 

 read daily at 9 a.m. and 5 p.m. The bottles in the cupboard were corked. 

 Twice weekly each bottle was taken out, uncorked, aspirated for 5 seconds 

 with the suction pump, corked, and replaced in the locker. 



The method of using closed bottles and aspirating seemed better than 

 the method of using open bottles and adding water lost, which has been 

 adopted elsewhere in investigating this subject. In order to judge of the 

 two methods, six bottles were left open, and the results compared with 

 closed aspirated bottles after a period of twenty-eight days. The follow- 

 ing figures were obtained : — 



Table I. 



Original moisture per 100 of dry soil 



Loss from Closed Bottles 

 Loss from Open Bottles 



24-08 



- 68 



8-8 



With closed bottles the losses were insignificant, while with open bottles 

 usually more than one-half of the original moisture was lost. The lost 

 water in open bottles cannot be replaced in a satisfactory manner, because 

 at the point where the water is added the soil will be much wetter than at 

 other points in the soil mass. To demonstrate this, a glass tube of i-inch 

 bore was packed with soil to the same degree as in the experiment bottles, 

 and to a depth, of 10 inches. Water was then added from the top equal 

 to 10.70 parts per 100 dry soil (40 per cent, of its water-holding capacity). 

 At the end of seventeen days the tube was cut into four sections of 2| 

 inches and the moisture in each determined. Of the total water in the 

 soil there was found in the top .section 35 ,; in the second, 31 ; the third, 

 24 ; and in the fourth. 10 per cent. With a smaller quantity of water, 

 or with a shorter time allowed, the differences would probably have been 

 greater than here noted. 



In each experiment the ammonia bottles and the control blanks were 

 done in duplicate, and the average results are taken where the figures 

 are close, when wider, the average is marked doubtful. This happens in 

 two instances with the very wet soils of the second experiments. 



