554 FRUIT CULTUKE IN FOREIGN COUNTRIES. 



It will be seen from the preceding there are some guanos which are 

 very rich in phosphoric acid and contain but little ammonia, whilst in 

 others the ammonia predominates, and the phosphoric acid is much 

 less. Potash is found in but very limited quantity, and in some guanos 

 there are no traces of it, as happens with the guano from the Lobos 

 Islands. Magnesia is also met with, but in small quantity. 



The organic substances are of easy decomposition, and cause the 

 formation of carbolic acid, which, decomposing the silica of potash in 

 the soil, liberates both the silica and the potash. Should the soil be 

 poor in potash and magnesia, it soon becomes barren, although the 

 quantity of guano may be increased. This should be well borne in 

 inind in the cultivation of orange trees, rice, and sugar-cane. 



Guano can not by any means replace good stable manure, but it is one 

 of its best complements, its action being immediate, due to the great 

 solubility of its principal fertilizing elements. Owing to the preceding 

 the action of guano is of but short duration, and unless alternated with 

 other manures, such as vegetable ashes, phosphates, stable dung, etc., 

 the soil soon becomes exhausted. It is a very good custom to mix the 

 guano with stable manure, as, in addition to economy and the facility 

 and equality with which it can be spread in this manner, the results 

 obtained are more beneficial, because, without lessening its efficacy, it 

 neither burns nor destroys the young plants, although these might come 

 in contact with it. By means of practical trials it has been found out 

 that 10,000 or 14,000 kilograms of stable dung mixed with 150 or 200 

 kilograms of guano produce much more satisfactory results than 30,000 

 or 40,000 kilograms of stable dung used alone, and that the earth after- 

 wards remain in a better condition for later culture. It has been 

 proved that a ton of guano (1,000 kilograms) is equal in fertilizing effects 

 to 33J tons of stable manure, to 21 tons of horse dung, to 33J of cow 

 dung, and to 14J tons of human excrement mixed. 



One of the most perfect known manures is human excrement. In this 

 is found all the elements required by vegetables, and in such a state 

 that their assimilation takes place with rapidity, their effects being 

 equal. Fecal matters are required as much for strong as for light soils, 

 but nevertheless a distinction should be made, viz, when the excrement 

 is in a desiccated state it is applied to argillaceous soils, and when fresh 

 the preference is given to light ones. The fecal matters are v^ry ener- 

 getic, and their action on the vegetation is rapid, brisk, and of short 

 duration, but whilst contributing powerfully to the first development of 

 the plants they weaken the strength of them during their latter period. 

 In short, it is a manure which quickly gives what it has to give, leaving 

 little or nothing behind it. That human excrement is one of the most 

 perfect manures is proved by its composition. According to Boussin- 

 gault, 100 kilograms of human excrement in an ordinary condition 

 contain 75 kilograms of water and 24.90 kilograms of dry matters, the 

 principal elements being : 



