Phosphorus in various Agricultural Crops. 333 



without apparently affecting the growth of the plant, the 

 particular constituent so varying is not of such importance for 

 the plant as when more constant. 



It will be observed that in many plants different parts re- 

 quire different constituents, which indeed is well known ; as 

 for instance in the case of wheat it is probable that an abun- 

 dance of sulphates in the soil would produce fine straw, and 

 of phosphates, fine grain, and the converse, other necessary 

 constituents being present. 



It may also, perhaps, be inferred from these analyses that 

 when grain is growing and ripening the amount of phosphorus 

 increases in greater proportion than the total weight, and di- 

 minishes in the straw, the grain abstracting that constituent 

 from it. Similar inferences may perhaps be derived from the 

 above, many of which are given for such purposes. 



The table given below is a practical application of these 

 analyses, being intended to show the quantities of gypsum 

 and bone-phosphate of lime represented by the sulphur and 

 phosphorus which are removed annually from an acre of land 

 by the respective crops ; being also that which should be 

 added to already fertile land to maintain it in that condition. 

 No allowance for what would be removed by drainage is made, 

 as that is too uncertain in its quantity, and cannot in many 

 cases be at all material, or else uncultivated natural lands 

 would long ago have become sterile. The quantities so re- 

 moved are no doubt compensated for by the disintegration 

 of the substrata, and the superficial removal of exhausted soil 

 by washing. 



In such a calculation as this, however, it is affectation to 

 pretend to great exactness, the elements which unavoidably 

 enter into it being so variable. The quantities on which I 

 have calculated are the greatest which are shown in the 

 analyses, unless where the variations are given, when I have 

 taken the extremes, and the weight of crop per acre is what 

 I learn to be a medium between the very best and average 

 crops ; but I am most willing to confess that I am not myself 

 practically acquainted with this ])art of my subject, and hence 

 cannot answer for their absolute correctness, but have ob- 

 tained them from the best authorities accessible to me. The 

 necessary alterations, however, arc easily made by any one for 

 himself, from the data I have given, but I think they cannot 

 be far wrong. The quantities are pounds of gypsum and bone- 

 phosphate of lime removed from one acre. 



