December, 1911.] 



525 



Scientific Agriculture. 



separate plot, and to see which plot 

 gives the biggest yield. Time will not 

 permit me now to indicate how utterly 

 misleading and unpractical such experi- 

 ments are. It would be easy to get 

 all kinds of strange conclusions from 

 such experimenting. For instance, here 

 are the leturns from nine plots in an 

 experimental field harvested a few 

 weeks ago : — 



Plot 1 yielded 20f lbs. per plot. 



„ 2 ,, 37£ ,, 



)» 3 » 29g ,, 



„, I „ 28 



5 ,, 27 ,i 



„ 6 ,, 27f „ 



>, 7 ,, 304 »> 



,, 8 ,, 35 ,, 



„ 9 „ 21 

 The manure applied to each of the 

 above plots had the same money value. 

 Which, then, was the best manure? 

 Clearly, we should say the one given to 

 plot 2. As a matter of fact, however, 

 each plot received identically the same 

 manure. The truth is, none of the plots 

 leceived any manure at all. The vari- 

 ations in the results were due to vari- 

 ations in the soil itself, or to some other 

 accidental circumstances. Now, had we 

 been manuring these plots on the princi- 

 ple of equal money values of trade 

 manures, we might have by chaDce 

 put an absolutely worthless manure on 

 to plot 2 ; and what a splendid advertise- 

 ment this experiment would have given 

 to such a manure. By so-called " practi- 

 cal " experiments of this kind, numbers 

 of farmers have been known actually 

 to injure the crops on some of their 

 plots by the wrong use of essentially 

 valuable manures ; and the anomalous 

 result has occurred of their giving the 

 palm to the least valuable fertilizer, on 

 the ground that it did the least injury 

 to the crops. 



Now, a really practical manure experi- 

 ment takes into account the nature of 

 the food which plants require to feed 

 upon, and it will be so planned as to 

 find out if the soil experimented upon 

 supplies enough of this food to insure 

 the maximum growth of crop. As to 

 which vendor's manures should be 

 selected for carrying out the test is of 

 no consequence whatever to the experi- 

 ment. Preferably, on general grounds, 

 one would choose the manure or manures 

 which supplied the required plant foods 

 at the lowest price and in the most 

 available form. 



Briefly, I may state that in practical 

 agriculture it is found in general 

 necessary to consider only three of the 

 plant foods, namely, nitrogen, phos- 

 phoric acid, and potash, A mixture 



containing these three plant foods in 

 standard proportions is called a com- 

 plete manure. If from this mixture one 

 or two of these constituents be omitted, 

 or be given in considerably reduced 

 proportions, then the quality of the 

 manure is altered. Now, the experi- 

 mental fields, the results of which I 

 have presented to you, are laid out on 

 such a plan as to furnish an answer to 

 the two leading questions which have 

 to be considered in practical agriculture, 

 namely (1) How much manure is to be 

 used? and (2) What kind? 



Thus we have a plot which receives no 

 manure, then we have a plot which 

 receives one measure of manure, that 

 we call the light dressing ; another re- 

 ceives two measures of manure, that we 

 call the medium dressing ; then another 

 receives three measures, and that we 

 call the heavy dressing. These four 

 plots give us a test as to the quantity of 

 manure required. Thus referring to the 

 figures on page 9, and comparing plot 

 1, which had the light dressing, with 

 plot 3, the untreated soil, we find that 

 one measure of complete manure has 

 caused an increase of 81 per cent, in the 

 crop. On plot 2, which had two 

 meausres of complete manure, the 

 additional measure has caused an addi- 

 tional 78 per cent, in the crop, that is to 

 say, twice the quantity of manure has 

 given practically twice the increase. 

 Evidently then the whole of the medium 

 dressing is required. On plot 4, how- 

 ever, which received three measures of 

 manure, the third measure has caused 

 an additional increase of only 14 per 

 cent., and probably this small increase 

 would not repay the cost of the manure 

 required to produce it. With figures 

 like this before us, we should say that 

 the medium dressing was the one of 

 maximum profit. These plots would then 

 have shown us tha quantity needed. 



Then we have another set of plots in 

 answer to the question as to the quality 

 required. On plot 5 we give the same 

 amount of phosphoric acid and potash 

 as on plot 2, but we give no nitrogen. 

 Now, if the soil can of itself supply 

 enough nitrogen, plot 5 will yield as 

 much as plot 2, and we shall naturally 

 conclude then that nitrogen manuring 

 is unnecessary. If, on the other hand, 

 we get no better result off plot 5 than 

 without any manure at all, we say that, 

 all the nitrogen given on plot 2 is need- 

 ed. If we get an intermediate result 

 then we may conclude that only a por- 

 tion of the nitrogen given on plot 2 

 is necessary. Plot 2, in.the above-given 

 returns, yielded an increase of 159 per 

 cent., but plot 5, to which no nitrogen 

 was given, yielded an increase of 107 per 



