IV.] 



CULTIVATION AND S'6/L WATER 



101 



During the first period, the month of May, a dry 

 spell prevailed, only 018 inch of rain fell, while the 

 evaporation amounted to 3-45 inches; despite this 

 loss the top foot of soil only contains 1 inch of water 

 less than at the beginning, so that the rest of the 

 excess of evaporation over rainfall must have come 

 from the subsoil, which had in fact to furnish 2-27 

 inches. In the second period more water fell as rain 

 than was evaporated ; the surface soil gained 1-4 inch, 

 which did not account for all the excess of rain over 

 evaporation, a further -17 inch must have descended 

 into the subsoil. 



The following figures, obtained by King, illustrate 

 how a spring ploughing preserves the soil moisture 

 during a period of dry weather, by establishing a 

 loose protecting layer over the water bearing subsoil. 

 The upper line shows the water content of the top 

 4 feet of a certain piece of land on 29th April, on 

 which date part of it was ploughed and part left 

 untouched. On 6th May, no rain having fallen, 

 the soil was sampled again, both on the ploughed 

 and the unploughed piece, with the results set out 

 in the lower figures : — 



It is seen that the ploughed land practically lost no 

 water during the week ending 6th May, whereas 

 during the same period the land not ploughed lost 

 9* i lbs per square foot of surface, a quantity equivalent 

 to if inch of rain. 



