The -Composition and Use of Fertilizers. 255 



keep all conditions of treatment as much alike as possible, except 

 for the application of fertilizers. 



1 Blank No fertilizer. 



2 Eight pounds Nitrate of soda. 



3 Sixteen pounds Dissolved rock. 



4 Eight pounds Muriate of potash. 



5 Eighty pounds Air-slaked lime. 



_ ( Eight pounds Nitrate of soda. 



' " ' ' ( Sixteen pounds Dissolved rock. 



- { Eight pounds Nitrate of soda. 



' ' ' ' ( Eight pounds Muriate of potash. 



j Sixteen pounds Dissolved rock. 



I Eight pounds Muriate of potash. 



[ Eight pounds Nitrate of soda. 



9 -j Sixteen pounds Dissolved rock. 



[ Eight pounds Muriate of potash. 



Plot No. 10 Blank No fertilizer. 



Plot No. 11 Two hundred and fifty pounds. Stable" manure, well-rotted. 



Plot No. 12 Two hundred and fifty pounds. Air-slaked lime. 



It may be desirable the first year to limit the work to the first 

 five plots, and then extend it as experience is acquired. 



(g) Interpretation of Results. — - If Plots No. 1 and No. 10 give 

 as good results in crops as any other, then the soil is in good 

 condition as regards its present plant-food supply. If Plot No. 

 2 gives increased yields, the need of nitrogen is indicated. An 

 increase of crops on Plot No. 3 indicates need of available phos- 

 phoric acid, and increase on Plot No. 4 shows need of potash. 

 Increase of crops on Plots No. 5 and No. 12 shows probable acid- 

 ity of soil or presence of unavailable potash compounds in soil 

 or else lack of lime sufficient for plant food. If Plot No. 11 

 gives better results than other plots, there is probably a lack of 

 humus in the soil. If Plot No. 6 shows no increase of crop, then 

 nitrogen and phosphoric acid are not deficient in soil. The other 

 plots are to be interpreted similarly in accordance with the be- 

 havior of crops. 



The amounts of plant-food materials indicated above are larger 

 than will be used on many soils and crops. But when once it 

 is found that any particular element of plant food increases a 

 crop, then some additional trials can be made to ascertain the 

 smallest amount of application that will give most economical 

 results. The factors that determine the- amount of plant food 

 needed are: (1) the amount of available plant food present in 

 the soil, (2) the amount of plant food required by the crop 

 grown, and (3) the kind of farming carried, on. 



