[357] SCIENTIFIC MANUAL. 71 



sition ; and taking into consideration the character of the 

 soil to be planted, the nature and analysis of the plant to 

 be cultivated, and the fact that the so-called organic ele- 

 ments, except nitrogen, are supplied by the air, the farmer 

 may supply the mineral ingredients in quantity and ratio 

 necessary to the production of a given crop. 



Prof. Levi Stockbridge, of Massachusetts, has reached 

 some remarkable results by experiment on different crops, 

 in which he predicted beforehand the increased produc- 

 tion, as the effect of the fertilizers applied. Some of his 

 results are very remarkable, and show a wonderful triumph 

 of science, as applied to agriculture. 



His experiments, conducted for several years, illustrate 

 two important facts, viz.: that potash, nitrogen and phos- 

 phoric acid are generally the only elements of plant-food 

 necessary to be added artificially to the soil, for the pro- 

 duction of our agricultural plants, (except, perhaps, tobac- 

 co, which requires more magnesia than is usually found in 

 soils.) and that by the application of these three elements, 

 dn an absolutely soluble condition, in the ratio to each 

 other in which analysis shows them to enter into particu- 

 lar plants, a given number of bushels or pounds of these 

 particular plants may be produced, within certain yet un- 

 known limits, in a measure proportionate to the quantity 

 of the fertilizer applied. 



A few out of the number of experiments conducted, 

 -either by himself or by others under his direction, with 

 uniformly satisfactory results, will suffice to illustrate the 

 method pursued and the results attained. 



Two equal plots at the college farm were planted in 

 corn, and treated alike in every respect, except that one 

 had no manure, while enough potash, phosphoric acid and 

 nitrogen, mixed in the proper proportion, and used in suf- 

 ficient quantity to make twenty-five bushels of corn, with 

 the natural proportion of stalks, were applied to the other, 

 with a small surplus, which he supposed the roots of the 



