‘Giant Cavendish’ (‘Williams Hybrid’) banana (Musa acuminata Colla) was grown at the Waimanalo Research Station on Oahu, Honolulu, in 8 blocks with 48 mats per block. Nitrogen was applied as a continuous gradient across the width (6 mats) of each block. Potassium applications varied continuously over the length (8 mats) of the block. A 10 cm wide strip of leaf lamina was secured on a monthly schedule from each side of the midrib at the widest point of the 3rd fully unfurled leaf of (nonbearing) shoots which received the 4th level of N and the 5th level of K. Mats from which these samples were taken were designated as control mats, with the amount and frequency of fertilization applied sufficient to maintain them at about 2.6% N and 3.2% K. Other mats were fertilized on the same schedule as the control mats. Amounts of fertilizer applied were always in a fixed ratio, both greater than and less than the control mats. A leaf sample was secured from each shoot of each mat soon after the flower bud had emerged. The 3rd full-sized leaf below the inflorescence was sampled. Leaf N levels were associated with banana yield. Yields approached maximum at about 2.8% N. Amounts of N fertilizer required were increased greatly by a heavy infestation of Cyperus rotundus L. This weed decreased yields independently of its competitive effects for N. There were few indications of a K deficiency under the conditions of this trial, although heavy K fertilization was required to maintain leaf K at 3.2% in the control mats. The results of K fertilization suggest that surface application is not a very effective means of supplying K to banana plants. The general pattern of K uptake indicated that banana was utilizing K from the subsoil. Suspected incipient sulfur deficiency was not confirmed.
Trifoliate orange [Poncirus trifoliata (L.) Raf.] and various other commonly-used rootstocks, submitted to long-day (LD) of 16 hours, (normal day + 4 hr incandescent light break), normal day (ND) of 12 hours ± 1 hr 10 min and short-day (SD) of 8 hour photoperiods fell into 2 groups—those which responded to LD tratment and those which did not. Rootstocks in the first group, Christianson, Beneke, Pomeroy, Rubidoux and Yamaguchi, trifoliate orange cultivars; Carrizo and Savage citranges [P. trifoliata × C. sinensis (L.) Osbeck.]; Sacaton citrumelo [P. trifoliata × C. paradisi Macf.]. Hawaiian sweet orange (C. sinensis) and Milam lemon (C. jambhiri Lush.), responded strongly to LD treatments in shoot growth and stem diameter. Rootstocks less responsive to photoperiod include Cleopatra mandarin (C. reshi Hort. ex Tan.), Estes lemon, (C. jambhiri), Troyer citrange, Swingle citrumelo, C. macrophylla Webster, C. taiwanica Tan. and Shin and C. volkameriana Pasq. This second group was considered better adapted to tropical conditions because they made better growth under SD conditions.