189G. A NEW METHOD IN SOIL-ANALYSIS. 317 



space ; but we will endeavour to put the matter clearly before our 

 readers in a few words. Certain plots have been manured completely, 

 and parallel plots in exactly the same way but with no phosphates. 

 The latter contain 2,730 lbs. per acre of P a 0. 5 , and the former 4,544 — a 

 difference of less than 1:2; but the amounts of P., O, soluble 

 in citric acid are respectively 237 lbs. and 1,259 lbs. — a difference of 

 nearly 1 : 6. From these facts Dr. Dyer infers that the amount of 

 available plant-food is nearly six times as great in the second case as 

 in the first ; and turning to the Rothamstead records we find that 

 the respective yields of barley in 1890 were 38f and 24f bushels an 

 acre — a grand difference truly ! Yet the determination by the old 

 style of merely the total phosphoric acid present would have told us 

 absolutely nothing ; for, as Dr. Dyer says, " the difference between 

 2,500 lbs. of total P. 2 0-„ and 4,500 lbs., per acre appears to be 

 immaterial as a measure of present fertility for a crop that requires 

 only 20 lbs. per annum for its actual sustenance " ! This single 

 example will suffice to explain to our readers the revolution effected 

 by the citric acid test in soil-analysis — one of the most important 

 factors in that scientific farming by which alone we can expect to get the 

 full benefit of Mother Earth's capabilities. We will not yield to the 

 temptation to multiply technical examples nor to adduce the parallel 

 evidence from the estimations of potash in the soils — contenting our- 

 selves with only quoting Dr. Dyer's guarded opinion that soils 

 containing less than *oi per cent, of P 2 0-„ or, perhaps, -005 per cent, 

 of K 2 O, soluble in a 1 per cent, citric acid solution, stand in 

 immediate need of phosphatic or potash manures. 



To sum up the differentia of Dr. Dyer's work. He has applied 

 Stutzer's process of analysing manures to the analysis of soils, and 

 has placed this purely empirical method upon a sound botanical basis; 

 he has then verified it by a laborious analysis of numerous Rotham- 

 stead soils, the history of the crops from which entirely bears out the 

 inferences drawn from his analytical examinations. We may add 

 that Dr. Dyer has since employed his new method in investigating 

 the available phosphoric acid and potash in the Rothamstead wheat- 

 soils, and expects shortly to publish his results, which are awaited 

 with much interest. 



F. H. Perry Coste. 



