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pounds potash. A crop of thirty tons will therefore remove about 102 

 pounds nitrogen, 45 pounds phosphoric acid, and 65 pounds potash. 

 How much of these ingredients are supplied by our soil ? This ques- 

 tion can only be answered by experiments. For twelve years the Su- 

 gar Experiment Station has tried to solve this problem by a series of 

 •ystematic experiments. (^^) Three permanent plats have been dedicated 

 to replies to this question, known respectively as the nitrogen, phos- 

 phoric acid and potash plats. These plats have been divided into 

 twenty experimeats, and the question asked of the 



NITROGEN PLAT 



ii : " Does this soil need nitrogen to grow cane successfully ?" If so. 

 what forms of nitrogen are best adapted to the wants of cane and soil, 

 and in what quantities shall they be supplied ? The forms of nitro- 

 gen used were Nitrate of Soda, Sulphate of Ammonia, Cotton 

 feeed Meal, Dried Blood, Fish Scrap, and Tankage. These were used 

 in such quantities as to furnish twenty-four and forty-eight pounds ni- 

 trogen per acre, former experiments having demonstrated that larger 

 quantities could not be appropriated in our average season. These 

 forms were used alone, and combined with excessive quantities of phos- 

 phoric acid and potash in highly available forms. At regular intervals 

 through the plat there were left experiments unfertilized to test the 

 natural fertility of the soil, and to each group of nitrogen experi- 

 ments was attached one containing only phosphoric acid and potash. 

 These experiments have been conducted on this plat for eight years 

 and wlQ be continued indefinitely in the future. The results up to 

 date show conclusively, that this soil needs nitrogen to grow cane suc- 

 cessfully, and while sulphate of ammonia has shown annually slightly 

 better results, the high cost gives no advantage over the lower priced 

 forms. Cotton seed meal comes next to the sulphate of ammonia, fol- 

 lowed closely by dried blood and nitrate of soda. Fish scrap and 

 tankage are slightly behind the rest, for reasons assigned below. 



It has been found also that but very few of our seasons give us rain- 

 falls in quantity and distribution sufficient to enable the cane plant to 

 aj^ropriate 48 pounds of nitrogen. Hence a larger quantity is exces- 

 sive, and it may be a waste. It is therefore safe to recommend quan- 

 tities of nitrogen varying between 24 and 48 pounds per acre for our 

 cane crop. Again, different soils and different kinds of cane require 

 varying quantities of nitrogen. Plant cane upon pea vine land, will 

 not require the same amount as upon succession" land, i.e., upon soils 



(2) Field experiments are absolutely necessary in order to answer questions of 

 this kind. It is a mistake to suppose that analytical investigations of the soil 

 can supply the answer. Chemical analysis can indicate broadly the character of 

 a soil »nd show what elements of plant food are present in large or in deficient 

 quantities, but it is impossible by this means to indicate with certainty whether, 

 for instance, it will prove remunerative to apply, say, 401bs, of potash per acre to 

 a particular soil ; nor is this to be wondered at when we remember that an acre 

 of soil to a depth of 12 inches weighs about 5,000,000 pounds, so that 40 lbs of 

 potash would represent -00008 per cent., and yet the addition of 4'J lbs. of potash 

 per acre may result in a large increase in the yield, and that, perhaps, on soil al- 

 ready containing from -2 to -5 per cent, or 10,000 to 25,000 pounds of potash, 

 combined in various ways. It is now universally admitted that laboratory in- 

 vestigations must be supplemented by field experiments. — F. W. 



