518 Abstract Report of Agricultural Discussions. 



In these potasli salts we obtain a great deal of common salt 

 together with the potash. In order, therefore, to imderstaud the 

 effect of the potash it is necessary to eliminate the effect of the 

 salt, and if we neglect to do this we shall be led into mistakes 

 which may be very serious in practice. I cannot better illus- 

 trate this than by referring to the results which I obtained last 

 year in some field experiments with salts of potash, which were 

 fortunately tried in conjunction with common salt. The experiments 

 to which I allude were tried on mangolds. " No manure " produced 

 13 tons per acre of clean roots : potash salts, at the rate of 1 cwt. per 

 acre, produced 15 tons. It would appear that the potash here pro- 

 duced an increase of 2 tons. But side by side with that I tried also 

 common salt : 2 cwt. of common salt produced nearly 17 tons ; so 

 that it would appear that common salt alone produced a better effect 

 than potash and salt. I will give you another result. Potash manure 

 applied at the rate of 4 cwt. per acre produced 21 tons of mangolds : 

 common salt at the rate of 8 cwt. j^er acre produced almost the same 

 quantity. Now this leaves the result altogether doubtful. We do not 

 know whether the increase was due to the effect of the potash. I may 

 observe that diu'ing the last four years I have tried on no less than 

 six different farms experiments with crude potash salts ; and if you 

 asked me plainly the question — " Does potash produce any beneficial 

 effect on farm produce ? " I should be at a loss to answer either in the 

 affirmative or the negative. I cannot say I have as yet obtained a 

 decided result. Each year there has been brought to light some acci- 

 dental circumstance which had been overlooked. Indeed we have to 

 learn how to perform field experiments. 



I have already advised that experiments should be as simple as 

 possible. In the next place care shoidd be taken to reserve two or 

 three plots on which no manure is to be applied. This is necessary 

 in order to ascertain the limits of the natural variations in the pro- 

 ductive powers of different parts of the same field. These limits 

 are in some fields sufficiently wide to spoil altogether the final result 

 of an experiment ; and indeed it would be well to ascertain them by 

 a previous trial, in order that we may except certain fields altogether 

 from our experiments. 



Again, regard should be had to the physical requirements of 

 particular crops. It is vain to try experiments on plants which, 

 on account of their habit of growth, will never succeed in a 

 temperate climate like that of England. It is vain, for example, to 

 try experiments on Indian corn in Scotland, or on mangolds in the 

 colder parts of the world generally. 



Again we are to regard the physical requirements of newly 

 introduced crops, such as kqunes — a most iiscful croj), but it can only 

 grow well in a warm soil. This is the reason why it succeeds so 

 well on even the poor sands. Again I may remark that, perhaps, 

 the failures of field trials made for the express purpose of ascer- 

 taining the cause of the failures of clover, or the clover disease, havci 

 quite as much to do with the physical as with the chemical conditions 

 of the soil. 



