THE EFFECT OF HEAT ON HAWAIIAN SOILS. 
INTRODUCTION. 
Heat as a means of stimulating crops has been made use of in cer- 
tain European countries for centuries. The burning of moorlands 
and the paring and burning of heavy clay sods were extensively prac- 
ticed in times past. Although their use at present is by no means as 
common as formerly, these practices have not been entirely aban- 
doned. The adoption of more intensive methods of farming, the 
use of fertilizers, cost of fuel, recognition of the serious destruction 
of the organic matter, and the demand for a more continuous use of 
the land have brought about the gradual disuse of these ancient 
practices. 
In America soil burning, in the sense it is understood in Europe, 
has never been made use of extensively. In connection with certain 
crops demanding early forcing, however, soil burning is practiced 
well-nigh universally. The seed of tobacco, cabbage in some locali- 
ties, and some other crops that are grown from transplanted seedlings 
are still sown in soil which has been previously burned. In prepar- 
ing seed beds for tobacco the soil is frequently burned heavily, usually 
a strong wood * fire being maintained on the bed for several hours. 
It is a matter of common observation that the growth of seedlings 
on the burned soil is usually superior to that on the surrounding 
unburned land. The effects of burning are by no means confined to 
the germination and growth of seedlings. In newly cleared lands 
crops of various kinds usually grow more rapidly and produce 
increased harvests on the spots where brush or log heaps have been 
burned, and often the effects persist through two or more years. 
In Hawaii the growth of certain crops is enormously influenced by 
the mere burning of small accumulations of brush and undergrowths 
of guava and lantana. The effect on cotton on the uplands of Oahu 
produced by these small fires may represent the difference between 
success and failure. The color and vigor of the crop on these small 
areas dotted here and there over a field attract attention. Other 
crops are affected similarly. 
1 Oil and gas are sometime; used for this purpose. 
(5) 
