10 



state is almost 84%, and even when air dry they still retain 15.79% of 

 moisture j it is quite probable though that part of this loss of weight on 

 drying is due to decomposition of the organic matter. Almost three 

 fourths (72.57%) of the perfectly dry substance volatilizes upon igni- 

 tion. Most of this volatile matter is of an organic nature, since the 

 loss due to the presence of hydrated silicates, oxide of iron and alumina, 

 and that due to carbon dioxide, cannot be very high. Thus the soils 

 are by their chemical analysis also characterized as of vegetable origin. 

 No. 1 is typical of these soils. The residue insoluble in hydrochloric acid 

 amounts to less than 1%, and the rest of the inorganic material is 

 principally calcium and magnesium carbonate. The soils are well provided 

 with carbonate of lime and the quantity of magnesia is quite small as 

 compared with that of lime. As regards the other plant food ingredients, 

 we find the percentage, of potash and of phosphoric acid to be rather 

 small, while the nitrogen is exceedingly high. This we would naturally 

 expect to be the case in a soil of this character. However, the actual 

 percentages calculated on the perfectly dry soils would be entirely 

 misleading, should we base any conclusions on them regarding their crop 

 producing power, hi the tropics, 0.2% of potash and 0.1% of phosphoric 

 acid would, in an otherwise good mineral soil, be considered quite 

 sufficient. But if we calculate the actual quantity of plant food per 

 acre foot of this vegetable soil, we find that the quantities of potash 

 and phosphoric acid arc exceedingly small, as may be seen from the 

 following consideration. The volume weight of the soil, i. e., the weight 

 per unit volume in its natural state, in five samples, was found to be 

 1.06 on the average, therefore the weight per acre foot amounts to a 

 little less than 3,000,000 pounds. Since 100 parts of soil contain only 

 16.14 parts of solid material, the total weight of solid material per acre 

 foot is roughly 500.000 pounds. One tenth of one per cent of this is 

 equal to 500 pounds, and we thus find that the soil contains on an 

 average only 500 pounds of phosphoric acid and 1,000 pounds of potash 

 per acre foot, and all of this is probably not immediately available for 

 the crop. The nitrogen, however, amounts to 11,000 pounds per acre foot, 

 and 7,000 pounds of this are found in the humus matter alone. According 

 to Hilgard. the uitrogen that is not found existing in the humus, is of 

 practically no value to growing crops, only the humus nitrogen being 

 used in nitrification. Hilgard also maintains that the percentage of 

 nitrogen in the humus should not be below 4' /', , as otherwise the soil may 

 become "nitrogen hungry". Whether this is true in the case of these 

 soils, remains to he seen; at all events the average percentage of nitrogen 

 in the humus is above 1', . and moreover, the actual quantity of humus 

 nitrogen per acre fool in our soil is higher than in 63 out of 72 soils 

 quoted hy Hilgard. 



