Productivity under shade in Hawaii of five crops grown as vegetables in the tropics
1990
Wolff, X.Y. | Coltman, R.R.
'Waimanalo Long' eggplant (Solanum melongena L.), 'Kahala' soybean [Glycine max (L.) Merrill], 'Jumbo Virginia' peanut (Arachis hypogea L.) 'Waimanalo Red' sweet potato [Ipomea batatas (L.) Lam.], and 'Green Mignonette' semihead lettuce (Lactuca sativa L.) were field-grown in two seasons at Waimanalo, Oahu, Hawaii, in the open sun and with four artificially produced levels of shade (30%, 47%, 63%, and 73%). Yields and vegetative growth of eggplant, soybean, peanut, and sweet potato decreased linearly with increasing shade levels. Compared to unshaded controls, yields of semihead lettuce increased significantly under 30% shade in Fall 1986. During Spring 1987, lettuce yields were reduced only slightly from unshaded levels by increasing shade up to 47%. Leaf areas of index leaves of eggplant, soybean, and lettuce were similar to unshaded controls as shade intensity increased, while leaf dry weight decreased under shade. By comparison, both leaf area and leaf dry weight of peanut index leaves decreased as shade increased. Leaf area and leaf dry weight of sweet potato did not respond to shading. The results indicate that, of the five crops studied, only lettuce can be grown successfully under lightly shaded conditions and still receive enough radiant energy for maximum photosynthesis and yields.
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