26 SHADE IN COFFEE CULTURE. 



contain a large amount of fertilizing material. Similar facts have been 

 established by M. Grandeau with the leaves of AZbizzia Jebbek. The 

 decaying leaves are incorporated with the soil in the processes of culti- 

 vation, and undoubtedly make a considerable addition to its fertilit} r , 

 and also improve its mechanical condition. The addition of lime is 

 supposed to add greatly to the value of this leaf manure bj neutraliz- 

 ing the acids formed in the deca} r of the vegetable tissues, and by lib- 

 erating free nitrogen or soluble nitrogenous compounds. There is, 

 however, a belief in Venezuela that the use of lime in coffee planta- 

 tions is dangerous, for, although the immediate benefit is admitted, the 

 ultimate result is said to be the rapid impoverishment of the soil. 

 According to Dr. Delgado, this erroneous view is based only on the 

 excessive use of lime beyond the amount required for the utilization 

 of the vegetable food materials already available; but if employed 

 with reasonable moderation lime is held by Jiim to be of great and per- 

 manent value. How far the alleged benefit attaches in reality to the 

 effect of lime upon the humus, and how far we are dealing with the 

 now well-established fact that many of the tubercle-forming bacteria 

 require lime for functional activity with leguminous plants, are matters 

 which can be determined only by careful experiment. 



It is of further interest to note Dr. Delgado's insistence upon the 

 fertilizing value of a stirring of the soil, quite outside of what may 

 be necessary in the removal of weeds. The regular use of the creole 

 plow between the rows of coffee is advised as extremely beneficial, 

 and the injury to the superficial roots of the coffee is said to be more 

 than compensated by the efficiency of the new ones put forth in the 

 newly stirred and aerated soil. But here again the possible effects 

 of stimulating the activity of the roots of the leguminous shade trees, 

 as well as the fertilizing value of the detached tubercles, are to be 

 taken into account in scientific experiments for determining the lines 

 of rational culture. 



A further suggestion from Venezula, of possible utility in Porto 

 Rico, is that for the utilization of the fallen leaves of shade trees on 

 slopes so steep that they are washed away in the rainy season. The 

 leaves are raked into windrows placed a little above the middle of every 

 second space. Just below the windrow a trench is dug 2 or 3 feet 

 wide and more than half as deep. The leaves are sprinkled with lime, 

 and the surface soil from the trench is also thrown over them, after 

 which they are pulled into the trench with a hoe, and the earth taken 

 from the trench is thrown back upon them. This plan is evidently a 

 modification of the system of open pits in use in Central America, and 

 already discussed under the subject of erosion. 



NITRIFICATION THROUGH SHADE. 



In the Boletin de Agricultura Tropical for September, 1899, an 

 ingenious explanation of the value of shade in the coffee culture of 



