190 SOILS AND MANURES 



ness of a scientific investigation. The scheme of " joint 

 experiments " published by the Board of Agriculture 

 includes one for the determination of the manurial re- 

 quirements of the soil. It does not differ in principle 

 from that described above, but is drawn up with a view 

 to accuracy rather than simplicity. The results will 

 be of much greater value for purposes of comparison 

 with those of other workers if the instructions given in 

 the scheme of joint experiments are followed in detail. 



The eight-plot test generally affords a fairly reliable 

 indication of the special manurial requirements of the 

 soil, but it is by no means infallible. The results depend, 

 to Borne extent, upon the crop to which the experiment is 

 applied, and the requirements of the crop must, therefore, 

 be taken into consideration in drawing inferences. Apart 

 from this, the experiment sometimes fails to return any 

 definite and satisfactory answer to the question. This may 

 be due, not to any fault in the test, but to the fact that, in 

 certain circumstances, it is not applicable. It does not 

 take into account certain other conditions which have a 

 considerable influence on productiveness. 



The Wire-basket Method. K quick method of testing 

 the manurial requirements of soils has recently been 

 devised by the American Bureau. 1 It consists in growing 

 the plants in small 'wire pots as shown in the illustration 2 

 (Fig. 26) containing the soil to be tested, to which differ- 

 ent kinds and quantities of fertilising ingredients are 

 added. The seeds are sprouted before being planted, in 

 order to secure uniformity and to accelerate the operation. 

 The baskets are coated with an- impervious layer of 

 paraffin, and when the plants have reached a height of 

 about two inches, are sealed with discs of paper dipped 



1 Bulletin 18, March, 1905. 



2 Bui. 2, New Zealand Dept. of Agriculture. 



