FERTILIZERS 61 



96. Certain forms of fertilizers, such as the ni- 

 trates (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, or -wherever water can go. If there is any 

 waste water a part of them is lost. 



If the grade from the flume is very steep for fifty 

 feet or more, the trees in that space will be the first 

 to turn yellow, although they are nearest the flume 

 and receive 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 

 carefully. Do not turn a heavy head of water into a 

 furrow until after the furrow is soaked a little and 

 the fine earth compacted. This will lessen washing. 

 The ideal movement of water is up and down, with 

 as little movement on the surface as possible. In 

 this way the rich top soil with its humus and fer- 

 tilizers will be retained where it belongs. 



VALUE OF SOIL ANALYSIS. 



97. Soil analyses are valuable for determining in 

 a general way the needs of a crop. The greater the 

 number of samples examined, the more accurate will 

 be the information obtained. Very little can be con- 

 cluded from one sample. Taken in connection with 

 the appearance of trees and vegetation raised on the 

 soil, many a useless expenditure for fertilizing ingre- 

 dients may thus be avoided. 



