1919.] NITROGEN CONTENTS OF CACAO SOILS. 



The total nitrogen and nitrates were estimated on the air-dried 

 fine soil and the results calculated on the fine soil dried at 100 deg. 

 Centigrade. The figures obtained and the rainfall on the estate are 

 given in the table below. 



From the figures recorded above it will be seen that : — 



1. The organic matter, total nitrogen and nitrates decrease during 

 the .Tune and September quarters with the heavier rainfall and 

 increase during the December quarter with the lowQr rainfall. 



2. With the exception of the December sample, the total nitrogen 

 is higher in the No Shade than in the Full Shade plot for each period 

 respectively. But with regard to the nitrates it is just the reverse 

 i.e. there are more nitrates present in the Full than in the No Shade 

 plot. Owing however, to the fixation of nitrogen from the air by the 

 bacteria in the nodules of the immortel roots and to the additional 

 supply of nitrogen derived from the immortel flowers, leaves and pods 

 bearing seed, the percentage of organic nitrogen in the soil is practically 

 no less than in the No Shade plot. There is no evidence, however, 

 that the larger amount of nitrates producad in the Full Shade plot 

 is beneficial to the cacao trees as the average yield of the past two 

 years for the Full and No Shade plots respectively, is practically the 

 same as the average of the previous five years. 



Another question presents itself and it is this. Is the smaller 

 amount of nitrates generated in the No Shade plot sufficient to 

 produce a maximum crop ? As far as can be judged at present the 

 amount of nitrates formed in the No Shade plot appears to be sufficient 

 as the yield from the No Shade plot shows a smaller decrease (408 

 against 662 pods per acre) during the past two years than the Full Shade 

 plot compared with the average yield of the first 5 years after the shade 

 had been cut out. 



The smallest amount of nitrates found, -00042 per cent., was in the 

 September sample for the No Shade plot and it represents what has 



