556 FRUIT CULTURE IN FOREIGN COUNTRIES. 



underneath, and particularly over the parts reached by the radical ex- 

 tremities, which is to say within the circumference covered by the 

 branches of the trees. These manures are buried in the soil, about the 

 end of October, at a depth of from 25 to 30 centimeters. Liquid ma- 

 nures are also sometimes employed, such as fecal matters, skins, and 

 refuse of oily seeds, and guano, the whole mixed together with a sufficient 

 quantity of water, but the effect produced is immediate and of short 

 duration. These should not be made use of except during the heat of 

 the summer and at the moment when the vegetation is most active, for 

 if applied during the winter they might lead to the putrefaction of the 

 roots. In general, they are not resorted to except for such trees as 

 appear languid and seem diseased, and a trench of about the depth of 

 5 centimeters is dug around the spot where this liquid manure is to 

 be placed, which is afterwards covered over. In order that the earth 

 may be fertile, it should contain all the necessary elements required for 

 obtaining the proper development of the plant that has to be cultivated 

 in it, and these must be in a perfect state of assimilation, but compost 

 and vegetable and animal remains that may be added to the earth in 

 the shape of manures do not return to it the principles lost by it yearly 

 with the crops raised; and Liebig, seeing that in all countries the agri- 

 cultural production was diminishing, commenced a series of studies to 

 ascertain the cause thereof, the result being such as to clearly demon- 

 strate what was taking place. He found out that all plants required to 

 assimilate a greater quantity of phosphoric acid than that contained in 

 compost, and consequently proposed the employment of bones and nat- 

 ural phosphates, as also mineral phosphates, coprolites, etc. Hence the 

 necessity of mixing or alternating complete with incomplete manures, 

 so that the earth may always retain its fertilizing properties. 



The method for calculating the substances which in the shape of 

 manure should be given to the soil as a necessity, after the collection 

 of each crop, is as follows : 



1. The cultivator should avail of all the vegetable manure obtainable 

 from the refuse of each crop, to which should only be added the fixed 

 principles of the fruit, the nitrogen required by it being supplied by the 

 ammonia in the air, as also that remaining on the surface soil after being 

 washed there by the rains. To ascertain, in this case, the quantity of 

 nutritive principles required to be incorporated with the soil, the prob- 

 able average weight of the fruit to be produced each year should be 

 calculated, having ascertained which, and taking into account the weight 

 of ashes, this problem is easily solved. Knowing the weight of the ashes 

 of 100 parts of the fruit, a proportion is established which will give the 

 required result. 



2. Should the cultivator not wish to avail of the vegetable refuse of 

 each crop, he should add, first, the fixed principles of the fruit, and, 

 secondly, the fixed principles of the branches and leaves. An analo- 

 gous calculation to the preceding will give the sum of nutritive principles 

 *o be added to the soil in the shape of manures. 



