V 



FIELD CULTURE 163 



about 8 per cent of the total weight. The composition 

 of this ash can be seen from the table of analyses 

 already given. 



The need of fertilizers on the plantation obviously 

 depends in a very high degree upon the use to which 

 the trees are put ; that is, upon the commercial product 

 which is sold from the plantation. If, for instance, oil 

 is sold and the oil-cake is kept on the place, and either 

 applied directly as a fertilizer or fed to animals whose 

 manure is returned to the soil, the theoretical loss of 

 food material is reduced to zero. There is of course 

 a slight actual loss, as nothing can be taken from the 

 soil and kept upon its surface without some being 

 washed away, and as decay is inevitably accompanied 

 by a loss of more or less nitrogen ; but such losses 

 are inconspicuous. If the trees are used for the pro- 

 duction of toddy the loss of mineral food is again 

 very slight. Fresh toddy contains about 0*02 per 

 cent of nitrogen, and the total ash amounts to about 

 one-fourth of 1 per cent. If from the toddy, sugar 

 or alcohol is produced, a considerable part of the 

 fertilizing materials in the sap will be separated as 

 waste products and can be returned to the soil. 



If copra is produced and sold, the amount of 

 material lost from the soil can be calculated from the 

 analyses already given. In making such a calculation 

 it is merely necessary to assume a reasonable number 

 of trees per hectare and a reasonable yield per tree. 

 To make calculations for a given plantation the number- 

 of trees actually present and the actual yield of nuts 

 will furnish a basis for the calculation. As a genera] 

 proposition copra contains from 1 per cent to 3*65 

 per cent of ash ; a convenient approximate figure is 

 2*5 per cent. The larger part of this is potash, which 

 is 1'35 per cent, more or less. Phosphoric acid amounts 

 to about one-half of 1 per cent. If the product 

 marketed is desiccated coco-nut, the loss of food from 

 the soil is the same as when copra is sold. If coir is 

 sold, or if for any reason the husks of the coco-nut 



