362 



SOILS. 



together with higher nitrogen-percentage, than in the case of the grass. 

 which in the several cuttings annually made, caused a greater depletion 

 in nitrogen and a smaller accession of humus. The grass was very 

 weak in its growth and partially dying out. 



No. 29, the sugar-cane land from Maui, was still in fair production, 

 but beginning to weaken as against its first production. No. 27, 

 the guava land from Hawaii, originally bore a luxuriant cover of 

 Avild guava, but after bearing one fair crop of seed-cane and one of 

 ratoons, the cane planted on it " spindled up " and died so soon as the 

 seed-cane planted was exhausted. Both the island soils, originally 

 derived from the weathering of the black basaltic lavas of the region, 

 were well supplied with mineral plant-food (see above, page 356), and 

 the humus-content in both was exceptionally high ; and neither was in 

 an acid condition. The difference in their nitrogen-content, both in 

 the totals and in the humus itself, suggested that notwithstanding the 

 relatively high total of nitrogen in No. 27, it might be nitrogen-hungry, 

 in view of the low percentage of the nitrogen in the humus. 



Confirmatory Experiment. A pot-culture with wheat, the 

 results of which are shown in the figure below, fully confirm 



FIG. 59. Growth of Wheat on Guava Soil from Hawaii Island. 



this suspicion. One kilogram of soil was used in each of two 

 pots, one being fertilized with half a gram of Chile saltpeter. 



