upon mainly. It travels up and down and sideways, 

 carrying with it the soluble fertilizers. 



As moisture evaporates at the surface, it is con- 

 stantly supplied from below by the capillary 

 movement. The dissolved fertilizers contained 

 remain on the surface after the water evaporates ; 

 hence they accumulate so that top soils are always 

 the richest. The next rain or irrigation carries the 

 plant food down only to rise again as evaporation 

 progresses at the surface. There is thus an oscillation 

 of water up and down many times a year. 



Certain forms of fertilizers, such as the nitrates 

 (both soda and potash) ammonium sulphate, the 

 sulphate of potash, and the acid and super-phos- 

 phates are easily carried by water. If applied just 

 previous to an irrigation they go to the deepest 

 roots, wherever water can go. If there is any waste 

 water a part of them is lost. 



If the grade at the flume is very steep for fifty or 

 a hundred feet, the trees in that space will be the 

 first to turn yellow, although they are nearest the 

 flume and received the most water. The nitrates 

 have been washed to lower levels. Manure or straw 

 should be used in such places so that the water will 

 move more slowly and the nitrates retained where 

 they belong. 



On account of the solubility of many forms of 

 plant food, irrigation water should be handled very 



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