INTRODUCTION. lv 



instituting future experiments!. It would have been better, undoubtedly, to have sown these manures 

 broadcast, except for the difficulty of sowing (hem evenly by hand on so narrow a plot without risk of 

 having some part of the manures blown upon the adjoining plots. 



It will be seen by examining the table, that, although the superphosphate of lime had a good 

 effect during the early stages of the growth of the plants, yet the increase of product did not come up 

 to these early indications. On plot 5, with 300 pounds of superphosphate of lime per acre, the yield 

 is precisely the same as on plot 2, with 100 pounds of plaster (sulphate of lime) per acre. Now, 

 superphosphate of lime is composed, necessarily, of soluble phosphate of lime and plaster, or sulphate 

 of lime formed from a combination of the sulphuric acid employed in the manufacture of superphos 

 phate with the lime of the bones. In the 300 pounds of superphosphate of lime sown on plot 5 there 

 would be about 100 pounds of plaster, and as the effect of this dressing is no greater than was 

 obtained from the 100 pounds plaster sown on plot 2, it follows that the good effect of the superphos 

 phate of lime was due to the plaster which it contained. 



Again, on plot 4, with 150 pounds of sulphate of ammonia per acre, we have ninety bushels of 

 cars of sound corn, and fifteen bushels of cars of soft corn (&quot;nubbins&quot;) per acre, or a tolal increase 

 over the plot without manure, of thirty-eight bushels. Now, the sulphate of ammonia contains no 

 phosphate of lime, and the fact tha* such a manure gives a considerable increase of crop confirms the 

 conclusion arrived at from a comparison of the results on plots 2 and 5, that the increase from the 

 superphosphate of lime is not due to the phosphate of lime which it contains, unless we are to conclude 

 that the sulphate of ammonia rendered the phosphate of lime in the soil more readily soluble, and 

 thus furnished an increased quantity in an available form for assimilation by the plants a conclusion 

 which the results with superphosphate alone, on plot 5, and with superphosphate and sulphate of 

 ammonia combined, on plot G, do not sustain. 



On plot 12 half the quantity of sulphate of ammonia was used as on plot 4, and the increase is a 

 little more than half what it is where double the quantity was used. 



Again, on plot 13, 200 pounds of Peruvian guano per acre gives nearly as great an increase of 

 sound corn as the 150 pounds of sulphate of ammonia. Now, 200 pounds of Peruvian guano contains 

 nearly as much ammonia as 150 pounds sulphate of ammonia, and the increase in both cases is evidently 

 due to the ammonia of these manures. The 200 pounds of Peruvian guano contained about 50 pounds 

 of phosphate of lime; but as the sulphate of ammonia, which contains no phosphate of lime, gives as great 

 an increase as the guano, it follows that the phosphate of lime in the guano had little if any effect a 

 result precisely similar to that obtained with superphosphate of lime. 



We may conclude, therefore, that on this soil, which had never been manured, and which had been 

 cultivated for many years with the ceralia or, in other words, with crops which remove a large quan 

 tity of phosphate of lime from the soil the phosphate of lime, relatively to the ammonia, is not defi 

 cient. If such were not the case, an application of soluble phosphate of lime would have given an in 

 crease of crop, which we have shown was not the case in any one of the experiments. 



Plot 10, with 400 pounds of unbleached wood-ashes per acre, produces the same quantity of sound 

 corn, with an extra bushel of &quot;nubbins&quot; per acre, as plot 1, without any manure at all ; ashes, therefore, 

 applied alone, may be said to have had no effect whatever. On plot 3, 400 pounds of ashes, and 100 

 pounds of plaster, give the same total number of bushels per acre as plot 2, with 100 pounds plaster 

 alone. Plot 8, with 400 pounds of ashes and 150 pounds sulphate of ammonia, yields three bushels of 

 sound corn and five bushels of &quot;nubbins&quot; per acre less than plot 4, with 150 pounds sulphate of ammo 

 nia alone. This result may be ascribed to the fact previously alluded to the ashes dissipated some of 

 the ammonia. 



Plot 11, with 100 pounds of plaster, 400 pounds ashes, 300 pounds of superphosphate of lime, and 

 200 pounds Peruvian guano, (which contains about as much ammonia as 150 pounds sulphate of ammo 

 nia,) produced precisely the same total number of bushels per acre as plot 4, with 150 pounds sulphate 

 of ammonia alone, and but four bushels more per acre than plot 13, with 200 pounds Peruvian guano 



