27 
Limestone containing 10 per cent of magnesium carbonate pro- 
duced as intense a chlorosis as a limestone containing 1 per cent of 
magnesium carbonate. 
The plants usually showed a slight chlorosis four or five months 
after planting and at the ninth month were strongly chlorotic. In 
all the experiments it was observed that the chlorosis was somewhat 
dependent on the growth. Plants which grew slowly at first did not 
become chlorotic as quickly as those which made a quick start. 
Also, the plants originating from small slips became chlorotic much 
sooner than those originating from large ones. Plants coming from 
very small but vigorous slips, which made a quick growth at the 
start, were the type that showed the chlorosis first and most intensely. 
From these observations it would appear that the chlorosis was 
dependent either on the exhaustion of a nutrient stored in the slip, 
which the plant was later unable to obtain from the calcareous soil, 
or on the absorption of an injurious amount of an element from the 
soil. 
CONCLUSIONS FROM SOIL INVESTIGATIONS. 
The results of the culture experiments confirm the conclusions 
arrived at by the soil survey. It is evident that the chlorosis of the 
pineapples observed on certain plantations is caused by an excessive 
amount of calcium carbonate in the soil. Experiments show that 
additions of calcium carbonate to soils that produce healthy plants 
cause these soils to produce chlorotic plants. Soils unusually rich 
in humus and organic matter require a large amount of carbonate of 
lime to cause them to produce chlorotic plants. Soils of this latter 
type do not exist in Porto. Rico to our present knowledge. 
No attempt was made to find by pot experiments the smallest 
amount of calcium carbonate in.soils that would cause this chlorosis, 
since the analyses of the different pineapple soils found actually pro- 
ducing chlorotic plants show this more accurately than could be 
determined by pot experiments. In reviewing the analyses it will be 
seen that the highest content of calcium carbonate found in any soil 
producing healthy plants was 1.15 per cent. The lowest content of 
calctum carbonate found in any of the soils producing chlorotic 
plants was about 2 per cent. This was a loose sandy soil. Thus, for 
sandy soils, a content of 2 per cent of calcium carbonate renders them 
unfit for pineapples. Possibly a sandy soil containing 2 per cent of 
carbonate of lime and at the same time a good content of humus 
might produce healthy plants, but in general it can be safely said that 
sandy soils containing 2 per cent or more of calcium carbonate are 
unfitted for pineapples. The danger limit for loamy soils may be a 
trifle higher. The only loamy soil which was found producing 
chlorotic plants contained 4.62 per cent of calcium carbonate. 
[Bull. 11] 
