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million parts, and clear canal and tank water slightly less, 

 about So or 90 parts in million parts. 



938. Unslaked lime (Cap) hastens the decomposition 

 of organic matter, kills grubs and spores of fungi and 

 decomposes double silicates, setting free the bases, potash 

 &c. In poor soils the setting free of bases is not desirable, 

 and, on the whole, slaked lime is to be preferred to hot lime, J 

 even when it is used as an insecticide and fungicide. Lime 

 renders clays lighter and sands less dry. The presence of 

 limp in soil is also useful for storing up phosphoric acid in 

 seeds which occurs as Ca 3 P 2 8 . It also neutralizes acids 

 generally and precipitates oxalic acid in particular as oxallate 

 of lime, which exercises useful functions in leaves and 

 stems. 



939. Magnesia and soda. Magnesia replaces lime to a 

 certain extent, and acts more or less in a similar manner in 

 soils and in plants as lime does. Magnesia is also widely 

 distributed in Indian soils and occurs chiefly as silicate. 



940. Rain water which contains about 4 parts of N in 

 every 10 million parts, contains no P 2 Os, K 2 O, CaO, MgO or 

 Na 2 O. Clear canal water contains in 10 million parts about 

 2 parts i6f N, 10 parts of P 2 Os, 100 parts of K 2 O, 900 parts 

 of CaO, 700 parts of MgO, and 200 parts of Na 2 ; while in 

 a muddy state the proportions in 10 million parts would be 



N ... ... ... 4 



P 2 O 5 ... ... ... 20 parts 



K 2 O .... ... ... 200 parts 



CaO ... .!. ... i,ioo parts 



MgO ... ... .- 1,000 parts 



Na 2 O ... ... ... 220 parts. , 



; . 941. Well water which is known to be helpful to vegeta^ 

 tion also contains a good deal of lime, i.e. abput 1,009 parts in, 



