VI. The appearances of drought. 



Having become acquainted with the laws of water circulation in 

 soil under various technical modes of culture such as leaving fields in 

 clear black fallow, green June fallow, waste land, and then under culture 

 of various plants, we shall proceed to examine those concrete cases where 

 plants are exposed to drought, and must inevitably face its. 



A temporary scarcity of water in the soil, affecting plants and hol- 

 ding back the normal course of their life processes, is what is known as 

 drought. But the scarcity of water in soil does not only depend upon a 

 small quantity of atmospheric residue (rain dew etc). 



The farmer way lose many of the advantages of the falling residue -- 

 principally in the form of rain-through bad management: the adoption 

 of an incorrect mode of tilling the soil when preparing it, for sowing or 

 when attending to plants, an unsuitable rotation of crops, one after anot- 

 her, and finally an irrational organisation of the whole farm. 



We have already seen that leaving fields lying waste, gets injuri- 

 ously upon their state of moistness. By spring, only a small thickness of 

 layer is moistened, and the expediture of water increases from the begin- 

 ning of the vegetation period. Naturally the extremely compact surface 

 of waste fields prevents water from accumulating therein, for a conside- 

 rable portion of rain-water runs off the slopes and declivities. And it 

 must be remembered that the same quantity of rain falls on waste fields 

 as on the neighbouring ploughed ones. 



It may be seen from the following figures, that insufficient advan- 

 tage taken of the falling residue, may have a great deal to do with the 

 appearance of drought. There falls in the sonthern governement of Russia 

 from 320 (the v/estern part on the Black Sea) to 400 mm. of residue per 

 year. If we exclude a third of this quantity (about 30" n) such as small 

 deposits which evaporate quickly from the soil, and certain fractions which 

 run off the surface without being absorbed we have still remaining not 

 less than 150 mm. which enters the soil and may be used by cultivated 

 plants. Bearing in mind that 1 mm. gives 650 poods ") of water to a dessiatin*") 



") Pood=36,ll pounds. 

 ^•^) Dessiatin^2,70 acres. 



