MANUAL FOR SUGAR GROWERS. 31 



they undergo decomposition with the carbonate of 

 lime in the soil, forming carbonate of potash or am- 

 monia and sulphate of lime, and the potash and am- 

 monia in this form is retained by the soil. From 

 this it will be seen how necessary it is to have a suf- 

 ficient quantity of lime in the soil, and why marling 

 tends to improve certain soils. 



Now, for certain substances the soil possesses but 

 little retaining power, such as nitrates and chlorides, 

 and these substances are always found in drainage- 

 waters ; it will at once be seen that this fact has an 

 important bearing on the application of nitrogenous 

 manures. It will be remembered that all compounds 

 of nitrogen are converted into nitrate by the action 

 of the nitrifying organism of the soil, and now it is 

 seen that soils have but little retaining power for 

 nitrates ; hence it follows that if heavy dressings of 

 nitrogenous manures, particularly nitrates, are placed 

 on the soil, there is a risk of loss by washing out in 

 the form of nitrates, unless the substance nitrifies 

 slowly and at about the same rate as the plant ab- 

 sorbs its nitrate. Nitrate of soda or sulphate of am- 

 monia should therefore be applied in small quanti- 

 ties, at tolerably frequent intervals, while organic 

 matter containing nitrogen, which nitrifies more 

 slowly, may be applied in larger quantities and at 

 greater intervals. In the tropics, the high tempera- 

 ture increases the rate of nitrification, and this, with 

 the usually heavy rainfall, renders the risk of loss of 

 nitrogen greater than in cold climates ; hence the 

 proper comprehension of the relationship of soils to 

 nitrogen, and particularly to nitrified nitrogen, is a 



