392 SOILS 



The fertiliser should be applied broadcast and 

 harrowed in lengthwise, not crosswise, of the plots. 

 The amount used should be somewhat larger than 

 in the field at large; if the plot is -fa of an acre 

 satisfactory amounts are 8 pounds of nitrate of 

 soda, 8 pounds of sulphate of potash and 16 

 pounds of superphosphate. The fertiliser may 

 be mixed with dry soil or sand in order to dis- 

 tribute it more evenly. Throughout the season 

 give all plots the same care. 



In comparing the crops grown under the dif- 

 ferent methods of fertilising it is well to take only 

 the inside rows of each plot, if no unfertilised strips 

 have been left between plots, because the outside 

 rows may have been affected by the fertilising of 

 the adjacent plots. The yields of the several plots 

 may be measured for comparison. Such a test as 

 this, even though not carried out in every detail, 

 gives valuable results to the man who is obliged to 

 use commercial fertilisers. It is well to repeat the 

 experiment two or three years and upon the same 

 land if possible. 



The Needs of Different Crops. The chemical 

 analysis of a crop is of very little practical value to 

 the man w T ho wishes to know what fertiliser to 

 apply to that crop. The proposition looks plaus- 

 ible, however. The chemist tells the cotton farmer 

 that the crop of cotton plants which produce 190 

 pounds of lint per acre draws an average of 40 

 pounds of nitrogen, 16 pounds of phosphoric acid 

 and 25 pounds of potash from the soil. The farmer 

 will then apply these amounts of the plant food each 

 year, but adding a little more, because probably 

 part of it does not reach the crop. 



But the chemical analysis of a crop is no more 

 reliable as a guide to fertilising that crop than the 



