The Effects of Slope Aspect on the Early Growth of Sugarcane in Hawaii Under Mid-Winter Conditions

Abstract

The variation in slope and aspect which occurs in any area with undulating terrains will result in relatively large differences in the climate of a specified area. Mountain slopes are characterized as having low soil temperatures especially in winter months in Hawaii. However, south-facing slopes theoretically have higher soil temperatures than slopes of other aspect because they receive more net radiant energy. This study was conducted to examine the water and energy balance variations between north- and south-facing slopes and their subsequent effects on the early growth of sugarcane. Lysimeters having initial slopes of 20% (11°09') with north- and south-facing aspects were used in the study, The study was conducted in Manoa Valley (Makua Campus, University of Hawaii) under mid-winter 6onditions (December-March). The results showed that soil temperature and net radiation were, respectively, 0.7 C and 21 langleys•day-1 greater on the south-facing slopes throughout the three-month experimental period. The effect of slope-aspect on the water balance was small. As a result of the temperature and radiation differences, cane fresh weight and leaf area at the end of the three month period were approximately 40% greater on the south-facing slopes than on the north-facing ones. Leaf and tiller number of the cane plants on the south-facing slopes were about seven days ahead of plants grown on the north-facing ones. Germination of setts and first secondary tiller were at several days earlier on the south-facing slopes.