20 MANUFACTURE OF TABLE SIRUPS FROM SUGAR CANE. 



hydrochloric acid at a constant temi^erature of 40° C, with con- 

 tinuous shaking-. I'his process applied to the soils in question show- 

 that the potash, although xu'esent in extremely minute quantities in 

 most of the soils, is very highly available; that is, practically all the 

 potash in the soil is at the disposition of the growing plant. On the 

 contrary, the phosphoric acid which exists in these soils, as a rule in 

 much larger quantities than potash, has a very much lower degree of 

 availability. Therefore, while a growing crop might take out all 

 of the potash in a soil, it would remove only a small quantity of the 

 phosphoric acid pi-esent. In other words, the phosphoric acid which 

 is present is so locked up in mineral combination as to be largely 

 insoluble in dilute, cold, or lukewarm hj'drochloric acid at the tem- 

 perature mentioned. 



These figures show that the potash present in the soil is practically 

 all availal)le for the growing crop, and the crop therefore takes as 

 much of it as may l)e necessary to meet its demands. On the con- 

 trary, the growing crop is able to take only a small fraction of the 

 phosphoi-ic acid pi-esent. Hence it appeal's that the general rule to 

 be followed in the case of these soils is to give them largely the two 

 essential elements of plant food which are least available in the quan- 

 tities in which thej^ exist in the soil, viz, phosphoric acid and nitrogen. 

 Of course there are many of these soils in which potash is also defi- 

 cient, but it is evident that the quantity which is present, although 

 minute, is very highly available. Ah a rule, therefore, if any one of 

 the three essential elements of plant food is omitted in the fertilizer 

 applied it would be safer to leave out potash than either phosphoric 

 acid or nitrogen. At the same time it is evident that in many of the 

 cases the judicious application of i)otas]i would be highly advisable. 



j In this connection, however, it must be remembered that, as a rule, 



l)lants take a lai-ger quantity of potash from the soil than of phos- 

 phcn'ic acid, and hence the presence of available potash, as deter- 



j mined by the dilute hydrochloric acid method in two or three times 



the quantity of available i)hosphoric acid, would indicate that the soil 

 was in equal iiee(] of both phosphoi'ic acid and potash in case either 

 was necessary to nuike the crop. 



Illustrations of what is meant l»y this can best be drawn from the 

 table of aiuilyses abo^e. Koi- instance, in No. i'2441 the potash solu- 

 ble in hydrochloi-ic acid is o-J pacts per million and the phosphoric 

 acid 14. 'I'liis soil needs potash ev(!ii more than phosphoric acid. In 

 the next number the proportions are as 85 to 20, respectively. This 

 is a soil in which phosphoric acid is probably needed more than potash. 

 In the next number the i)roportions are 20 to 5. Here both elements 

 are deficient, but phosphoric acid in a more marked degree than 

 potash. P^'or the next number the proi)ortions are 2!) to 20. This is 

 a soil which needs especially potash. In Uio next numbers the pro- 

 portions are as 50 to 1 and 51] to 1, and, in fact, in many of the numbers 



