BACTERIA IN THE INDUSTRIES 1 63 



tutes the excess water (from rains, overflows, melting snows, surface see- 

 page) which percolates downward between the particles of the soil (pore 

 spaces), due to the influence of gravity. This water which is thus carried 

 downward more or less rapidly by the force of gravity, is called hydrostatic 

 water. Very naturally the amount of hydrostatic water in soils depends 

 upon the physical conditions of the soils themselves, more especially upon 

 the porosity and fineness of the subsoils. The hydrostatic water carries 

 with it certain solutes (chemical compounds) and very minute particles 

 (organic, bacteria, colloids, mineral, etc.) and many of these are whpUy 

 lost because carried beyond the reach of the crop plants which might have 

 utilized them. 



While hydrostatic water is instrumental in the distribution of soil 

 bacteria it is of httle significance in the growth and multiphcation of 

 bacteria. The crop soils should be in such condition as to allow the 

 hydrostatic water to percolate to the deeper soil strata (two to eight 

 feet) and even in these deeper strata the pore spaces of the soil should 

 only be partially filled with water and never for long periods of time 

 during the growing season, because souring of soils and root rot would 

 likely result, should temperature conditions be favorable. Farmers in 

 arid and semi arid countries are fuUy aware of the fact that excessive 

 irrigation during the growing season encourages root rot, especially of 

 the deep rooted crop plants. In fact heavy irrigation during the growing 

 season is one of the means employed for exterminating the morning glory 

 and other deep rooted weeds ("drowning out" the weeds). 



Hydrostatic soil water is an agricultural essential as it constitutes the 

 storage water upon which the growing plant must draw during intervals 

 of little or no rain fall. The amount of annual moisture precipitation 

 necessary to the successful growing and maturing of crop plants depends 

 upon the nature of the crop plants, the temperature (during the growing 

 season), the physical character of the soil, and upon the methods and 

 means employed for conserving the soil moisture and also upon the amount 

 of atmospheric moisture present. Thus wheat, barley, corn, peas, beans 

 and other shallow rooted short period (six weeks to three months) crops, 

 can be made to yield well with a seasonal precipitation not to exceed four or 

 five inches, provided, of course, that the precipitation comes in one or 

 several volumes shortly before and during the early growing season. An 

 annual rain fall of from fif teeen to thirty inches is ample for the thrifty 

 growth of all kinds of plants. It is perhaps evident that the deeper soils 

 will retain and store more hydrostatic water than will shallow soils. 

 There are a great number and variety of factors which modify the distri- 

 bution of hydrostatic water. 



It is generally known that if one end of any dry porous substance (lamp 



