REPORT OF THE 'CHEMIST. 159 



Table I.— lite weight and average composition of ordinary crops, tfc— continued. 



Bwedea, roots (14 tons*). 

 Leaf (14 tons") 



"VTeight of 

 crop. 



Lbs. 



31, 360 



4,704 



3 1 1 



H i S 



Lb». \Lb3 Lbs Lbs. Lbs. Lbs. Lbs. 



3,349 163 74 14.6 63.3 22.8 19.7 



706 75 28 I 3. 2 I 16. 4 I 9. 2 22. 7 



Total crop \ 36,064 | 4,055 238 i02 ;17. 81; 79.7 | 32. ; 42.4 



Mangels, root (22 tons*) 

 Leaf 



Total crop 



Potatoes, tubers (6 tons) 

 Haulm t 



Lbs. Lbs. ' Lbs.] Lbs. 

 6. 8 I IS. 9 , 6. 8 ! 3. 1 



2. 4 4. 8 I 8. 3 3. 6 



9. 2 21. 7 15. 1 



6.7 



'A ton of 2.240 pounds. 



t Calculated from a single analysis only. 



From the above table we can judge of the quantity of the different 

 Boil-constituents which various crops absorb from an acre of ground, 

 and how certain plants demand some one i)articular ingredient more 

 than others. In general, we may say that the cereal crops apparently 

 possess a capacity for feeding on silicates not enjoyed by other crops, 

 and contain a less amount of nitrogen than either the root or legumi- 

 nous crops; nevertheless they respond the most readily to nitrogenous 

 manures. The amount of phosphoric acid is the most constant of all 

 the constituent of crops, being concentrated in the grain. The root 

 crops contain a large amount of potash, and arc the most exhausting 

 to tbe soil in consequence; they take up more nitrogen than do the 

 cereals, besides other ash constituents, as phosphoric acid. Legumi- 

 nous crops contain about twice as much nitrogen as do the cereals, and 

 the potash anil lime occurs in large proportions. Silica is nearly absent. 

 They resi)ond most readily to potash manures. 



The growth of forests is far less exhausting to a soil than are most 

 ordinary farm crops, especially where the leaves from the trees are left 

 to manure the ground by their decay. 



PERMANENT FERTILITY. 



The investigations of Messrs. Lawes and Gilbert in regard to the ex- 

 haustion of land by the same crops grown year after year on the same 

 Held, left unmanured, which they have been carrying on at Ebthamsted, 

 England, for the past forty years, leads them to conclude that all lands 

 left unmanured for a longer or shorter number of years have a certain 



