WAX-SEAL METHOD FOR DETERMINING WILTING COEFFICIENT. 11 



sifting, is thoroughly mixed, special care being taken to avoid the 

 separation of the fine and coarse particles. Variation in the amount 

 of gravel and coarse sand in the different pots causes irregularities 

 in the wfiting-coefncient determinations, due to the fact that the 

 coarse particles add to the weight of the soil without appreciably 

 contributing to its water-holding properties. 



In certain soils, notably those deficient in lime, it is best to add 

 a small amount of calcium carbonate to the soil before planting 

 to insure the growth of the seeds. 



(2) The proper amount of water to be added to the air-dried 

 soil is dependent upon the soil texture, varying from 5 per cent 

 for sand to 30 per cent or more for clay. The quantity to be used 

 is best determined by adding water slowly from a graduate to a 

 small weighed portion of soil until a condition of good tilth is reached. 

 A heavy soil can be moistened without puddling by placing it on a 

 slab or table in a cone-shaped pile with a large crater in the top 

 into which the required amount of water is slowly poured. The 

 crater is then filled with dry soil from the sides, and the whole mass 

 is covered to prevent evaporation and allowed to stand until the 

 water permeates the mass. The soil is then thoroughly mixed. 

 During the process of mixing it is sifted through a screen of ^-inch 

 mesh so as to remove any pellets of soil having more than their 

 proportionate amount of water. After mixing, the moist soil should 

 be kept in a tight receptacle until ready for use. 



Impervious pots must be used, of course, in order to prevent 

 the soil in contact with the pots from drying out below the wilting 

 coefficient. We have found that ordinary straight-walled drinking 

 glasses are very satisfactory for this work when seedling plants 

 are used. During the process of filling, the soil is slightly compacted 

 by jarring the bottom of the glass against the hand. Three to five 

 seeds are planted in each pot, about 1 centimeter in depth, after 

 which the surface soil is smoothed and compacted slightly. The 

 soil surface after planting should be about 1 centimeter below the 

 edge of the glass. It is often advantageous to plant seeds which 

 have just begun to germinate. This method insures a perfect stand 

 and avoids excessive respiration beneath the wax seal. 



(3) In sealing the pots the wax is heated slightly above the melting 

 point and a sufficient amount is poured into the pot to cover the soil 

 surface to a depth of about 3 millimeters. The pot is rocked slightly 

 so as to bring the wax into thorough contact with the inner walls of 

 the pot, after which the excess wax is poured off. If the wax is at 

 the proper temperature this will give a perfect and uniform seal over 

 the entire surface. If the seal is not perfect the process is repeated. 

 The wax layer should be approximately 1 millimeter in thickness and 



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