14 BULLETIN 55, HAWAII EXPERIMENT STATION 
able bed for the plants. Loosening the soil gives better drainage 
and a greater feeding area for the roots, which then become deeply 
established and enable the plant to withstand heavy winds. Thor- 
oughly preparing the land also greatly increases nitrification and 
other chemical processes releasing plant food in the soil. 
IMPROVING THE SOIL 
In addition to deep plowing and good drainage, banana soils 
often need some kind of fertilizer. Fertilizing materials include 
barnyard manures, green manures, lime, and chemical or commercial 
fertilizers. The soils usually have most of the necessary elements. 
Nitrogen, potassium, phosphorus, and calcium are the elements 
most likely to become exhausted and to require replacement by the 
use of fertilizers. Numerous experiments with fertilizers for bana- 
nas have been made by private growers, fertilizer concerns, and by 
the station, alone and in cooperation with growers. Barnyard 
manure has been found to be very beneficial, especially at the central 
station in Honolulu. 
In using fertilizers the grower must be guided not only by his 
general knowledge of the needs of the plant but also by close study 
of its growth, including its composition and the action of the soil 
under treatment. Considerable experience is required to determine 
the kind of fertilizer necessary and the best method of applying it. 
Sufficient nitrogen is shown in a vigorous growth of rich green fo- 
liage, whereas nitrogen deficiency is generally indicated by poor 
growth of foliage of yellowish color. Nitrogen deficiency is often 
corrected by the application of barnyard manure and the incorpora- 
tion of an abundance of humus in the soil, with more moisture. 
Green manures also assist in maintaining humus, which aids in nitri- 
fication. Nitrogen deficiency may be temporarily overcome by using 
nitrate of soda, sulphate of ammonia, or dried blood. Potash also 
often improves the fruiting quality of banana plants. Both Higgins 
and Fawcett state that where vigorous plants produce bunches of 
fruit of inferior size and quality the condition may often be cor- 
rected by using potash in some form, such as sulphate or muriate of 
potash. The need of phosphoric acid is probably not so easily 
determined, but the fact that phosphorus is present in practically 
every plant cell indicates its importance. Applied as superphos- 
phate, which is phosphate rock treated with sulphuric acid, phos- 
phoric acid is often believed to be the correcting element for stunted 
growth. Lime in excess of that already present in the soil may 
sometimes be required as a soil amendment, or, what is known as 
an indirect fertilizer, rendering the potash more available to the 
plant. It aids nitrification and may also correct soil acidity, result- 
ing in an improved physical condition. (For fuller discussion of the 
use of fertilizers, see 11, p. 69.) 
PLANTING DISTANCES 
The distance between the rows and the plants in the row varies 
somewhat with the character of the soil, the amount of moisture 
available, and the variety to be planted. Different distances are 
used in setting the Chinese banana, the leading commercial variety 
