172 AGRICULTURE 



action of the two phosphatic substances 

 will be indicated. Similarly, if we desire to 

 compare the relative effects of nitrate of soda 

 and sulphate of ammonia, a plot may be 

 dressed with 5 cwt. super., f cwt. sulphate 

 of ammonia, and 5 cwt. kainit, when a 

 comparison of the yield of this plot, with that 

 of plot 2, will give information as regards 

 the relative action of these two nitrogenous 

 manures. Similarly with regard to a com- 

 parison of the effects of kainit and muriate 

 of potash, 1 cwt. of the latter substance 

 (90 per cent, pure) being about equivalent 

 to 5 cwt. of the former. 



Even when every care has been exercised 

 in selecting and measuring the land, and in 

 applying the manures and weighing the 

 crop, one series of plots, confined to a single 

 season without any check, can hardly be 

 expected to give thoroughly trustworthy 

 information. The most reliable line to follow 

 is to duplicate all the plots, and if it is found 

 that there is marked consistency in the 

 yields of the two series, the results may be 

 taken as sufficiently reliable for ordinary 

 practical purposes. But duplicating all the 

 plots means doubling the expense, and, in 

 order to keep down the cost, it will gener- 

 ally be sufficient to duplicate certain of the 



