November, 1912.] 



349 



PRACTICAL VALUE OF SOIL ANALYSIS. 



The Journal of the Board of Agriculture for September in an article 

 on this subject states that: — In most cases the idea appears to be enter- 

 tained that having a soil analysed is ready means of obtaining an indi- 

 cation of its fertility and a discussion as to bow far this view is correct 

 may therefore not be out of place. 



The fertility of the soil may be defined as its power of growing crops 

 and while this depends to a great extent on the soil's ability to supply the 

 crop with what is often termed plant food, particularly nitrogen, phos- 

 phoric acid and potash in a suitable form, this is by no means the only 

 essential condition. Even if the analyst could give complete information 

 about plant food and were able to measure accurately the mechanical con- 

 dition of the soil, the information obtained in the laboratory could only 

 give a very incomplete idea as to the fertility of any particular field and 

 the farmer would have to supplement it by his own local knowledge, ex- 

 perience and judgment, 



The Limitations of the Analyst. 



Although the analyst is unable at present to give more than very 

 rough and incomplete information even about those factors influencing 

 fertility, some of the difficulties with which he has to contend may be men- 

 tioned here. He can determine as accurately as need be the total amounts 

 of nitrogen, phosphoric acid and potash in the soil and it has been found 

 that, even where external factors, e.,g., climate, depth of soil, etc., do not 

 enter into the case, there is often little or no connection between these 

 amounts and the soil's manurial requirements. Most of the plant food, 

 however, is is an unavailable or locked-up condition and is only gradually 

 set free or made available. 



In the case of phosphates and potash, a method has been devised of 

 roughly measuring the amount which may be regarded as of immediate 

 or prospective value to the plant by finding, not the amount of phosphates 

 or potash present, but the amount which is dissolved out in a given time 

 by a weak solution of citric acid. This method gives results which in 

 many cases indicate fairly well whether a particular soil will respond to 

 applications of either of the two kinds of manure. At the same time there 

 are many cases where the results obtained are at variance with those 

 obtained by actual experiment in the field. 



The Best Manure for the Land is the Master's Foot. 



Two conditions essential for the satisfactory growth of crops are a 

 sufficient supply of water and the proper aeration of the soil. By carrying 

 out a " mechanical analysis," the proportions of particles of different deg- 

 rees of coarseness can be measured, and as the results of such analyses 

 accumulate it will probably become possible to estimate from such an 

 analysis such factors as water retaining power, ease of drainage, ability 

 to withstand prolonged drought, etc.; and even to say with some degree 

 of certainty what systems of cultivation are most likely to result in a 

 good tilth at any particular time of the year, but in most cases an ex.. 



