should be always conducted in duplicate, two such series of 

 five plots will also make a ten plot experiment. 



66. If none of the applications prove of any'use, i e. if the 

 yield of the cereal and of the pulse crop are about the same in 

 all the manured and unmanured plots, the soil must be con- 

 sidered extremely rich in 'all available plant foods; and if not- 

 withstanding all these applications one does not get any yield 

 or very poor yield of pulses and cereals, the soil should be 

 considered barren or very nearly so, that is (i) containing an 

 excess of some salt, or (2) deficiency of some essential 

 constituent, or (3) containing some poisonous substance. 



67. Another method of carrying out this experiment is 

 to apply a mixture of all the four manures (which is called 

 Ville's Normal Manure) to one plot, the same without lime 

 to the next, the same without potash to a third, the same 

 without phosphoric acid to a fourth, and the same without 

 nitrogen to a fifth. This is called Ville's Five Plot Experi- 

 ment. There should however be unmanured plots for com- 

 parison and the more the number of such plots the better. 



CHAPTER VI. 



CHEMICAL CLASSIFICATION OF INDIAN SOILS. 



U HP HE four main types of soil" says Dr. Leather, 

 " which occupy by far the greater part of the Indian 

 cultivated area, are (i) the Indo-Gangetic alluvium, (2) the 

 black cotton-soil or regur, (3) the red soils lying on the meta- 

 morphicTOcks of Madras and (4) the laterite soil which are 

 met with in many parts of India." (5) Stretches of alluvium 

 which are situated at the mouths of the Mahanadi, Godaveri, 



