8 
BULLETIN 57, HAWAII EXPERIMENT STATION 
A second plowing is then made, followed by harrowing, and in another 
month by a third plowing and harrowing. The operation is repeated 
a fourth time if weeds and grass roots have not been wholly destroyed. 
Although such preparation covers three or four months ' work, any 
attempt to curtail it usually results in depressed yields and increased 
costs in cultivating after the crop is planted. Cultivated land requires 
usually only one plowing and disking, and one crop closely follows 
another. The light soils may be plowed immediately after a heavy 
rain to facilitate rotting of the weeds and grass. 
Continuous cultivation should be given the crop until it attains suf- 
ficient size to shade out weed growth. (Fig. 2.) One hoeing is usually 
enough when the field is check planted, permitting cross cultivation. 
The importance of clean culture in the early stages of growth of edible 
canna was strikingly demonstrated in a portion of the experimental 
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Fiq. 2.— A two-month weed growth in a field of canna 
plat where weeds were let grow for the first seven months. Although 
this portion was subsequently weeded and given the same treatment 
accorded the rest of the plat, it yielded 20 tons less per acre at 20 
months than was obtained from the cultivated portion. Animal- 
drawn cultivators equipped with five shovels are the most commonly 
used types, although the seven-tooth type is being introduced. With 
the latter equipment shallower cultivation is possible, the long 
matted grasses are more readily loosened, and the shallow root growth 
of the canna plant is less likely to be disturbed. 
The expensive process of hand weeding might well be dispensed 
with in favor of sodium-arsenate spray, which has been used most 
effectively in the Hamakua and Hilo districts. At Waimea the 
effectiveness of the spray might be lessened somewhat by the frequent 
mists and strong winds. The spray as used in the Hamakua and 
Hilo districts is made as follows (10, p. 54). 
