Z7Z 



which do not have a high average monthly rainfall — the physical 

 condition of the soil, which in many places is naturally quite por- 

 ous ; and the high slope of the farm lands, on many plantations 

 averaging 500 feet per mile. 



Upland or unirrigated kalo demands at least fifty inches of rain, 

 distributed with fair uniformity throughout the year. Because 

 of this requirement kalo cannot be raised on the leeward slopes 

 of the islands, below 1000 feet elevation, without irrigation. On 

 the windward sides of the larger islands it can be grown, without 

 irrigation, from sea level up to 1500 feet. On many parts of the 

 islands above 1500 feet elevation, the growth is considerably 

 slower, because of the low and variable temperature. Above 4000 

 feet kalo raising is not practicable. 



Necessarily, in order to produce heavy yields per acre, the soil 

 must be very rich. For wet-land cultivation the soil must be 

 capable of being puddled, so that it will hold without seepage the 

 water which is flooded over the field during the greater part of the 

 growing season. According to the natives, regions that are 

 abounding with springs are not suitable for kalo culture, except 

 for the raising of certain wild or inferior varieties. 



The soils of Hawaii are composed almost wholly of dis- 

 integrated lava rock, and are of recent geologic origin. In the 

 valleys and wooded regions there is a small amount of humus ; 

 along certain shores there are lowland plains of coral origin ; but 

 aside from these there is no other soil but that derived from lava. 

 In many places one can observe with striking clearness the various 

 stages in the decay of the original lava-flows. As a rule the 

 soils are very deep, this resulting from either decomposition in 

 situ, or long-continued washing from higher levels. 



There are three important soil-classes, — lava, tufa, and sedi- 

 mentary. Under normal climatic conditions the weathering of 

 lava, which contains an exceptionally high percentage of iron, 

 produces a heavy, fertile, dark-red soil. Soils of this character 

 usually occur on the leeward slopes of the islands. In regions of 

 heavy rainfall (the windward slopes are thus), incomplete oxida- 

 tion of the iron compounds in the basalt gives grayish-yelloiv soils. 

 These are usually not as fertile as the red soils, because the ex- 

 cessive rainfall leaches out much of the soluble plant-food. 



Tufa, or tuff, has a common source with the basaltic lavas, but 

 differs from them decidedly in many particulars, due to its violent 

 ejection thru the action of steam and gases. Tufa soils are light- 

 red or yeUoii'ish, friable and very porous, and not especially fer- 

 tile. The sedimentary soils, mentioned above, sometimes contain 

 sufficient humus to be decidedly dark in color. These are the 

 typical "taro-patch" soils, and are used for taro, rice and banana 

 plantations. 



All of these soils diff'er markedly from the usual mainland ag- 

 ricultural soils, and demand special treatment. Physically they 



