6 BULLETIN 50, HAWAII EXPERIMENT STATION. 
The number of sweet-potato cuttings required per acre is indicated 
in the following table: 
Number of sweet-potato cuttings required per acre when planted at different distances. 
Distance 
apart of 
rows. 
Distant ' ^ umber of ' 
auarthi i sweet-potato 
a ^V ! cuttings : 
r0Wi> - per acre. 
Distance j Distance 
apart of apart in 
rows. rows. 
Number of 
sweet-potato 
cuttings 
per acre. 
Feet. 
2 
f 
3 
Feet. 
2 
10, S90 
6,008 
9,680 
7,260 ; 
Feet. 
3 
3} 
4 
Feet. 
3 
? 
4,S40 
8,297 
5,445 
CULTIVATION. 
The sweet potato requires careful cultivation when it is grown in 
soil other than sand or sandy loam. The shape and size of the roots 
are materially affected by the physical condition of the soil. Cultiva- 
tion loosens and aerates the soil, and puts the plant food in such 
condition that it can readily be assimilated by the crop. It also keeps 
down weed growth and helps to conserve soil moisture. 
The first cultivation should be given when the vines are about 
8 inches long, or sooner, if the field is weedy. Cultivation consists 
in turning under the weeds and throwing the soil from the furrow to 
the ridge with a small one-horse plow, supplemented with hoeings 
to bring the soil up around the plant. When the vines are grown 
under level cultivation, a harrow should be used on the soil. Usually 
three or four cultivations are sufficient to keep the soil in good tilth 
until the field is overrun with vines. Weed growth is promoted dur- 
ing the rainy season, and the ground then requires frequent cultiva- 
tion. Sweet potatoes can best be cultivated with a hoe when they 
are grown on small areas. 
FERTILIZERS. 
The sweet potato readily responds to applications of fertilizer. At 
the experiment station an increase of 42 per cent in yield resulted 
from the application of a mixture of sodium nitrate, potassium 
sulphate, and acid phosphate, in the proportions of 75, 150, and 400 
pounds, respectively, per acre. At the substation at Haiku, Maui, 
sodium nitrate, potassium sulphate, and equal parts of reverted 
phosphate and acid phosphate, in the proportions of 100,150, and 250 
pounds, respectively, per acre gave the best results. 
It is suggested that the potassium sulphate be increased in the 
first formula to 200 pounds for very sandy soil, half of the fertilizer 
being applied when the plants have been set for about five weeks, 
and the rest five weeks later. The fertilizer should be uniformly 
applied. The Haiku formula is recommended for use on areas where 
the soil is adapted to the production of sweet potatoes, but on elevated 
regions maturity is delayed by reason of the altitude, the reverted 
phosphate being gradually made available to the plants during the 
protracted period of growth. 
