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Abstract
‘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.
Abstract
Phosphorus fertilizer was applied as specified by adsorption curves to establish 8 concentrations of P in the soil solutions of a soil developed in volcanic ash with a large capacity to immobiize P. Chrysanthemum morifolium Ramat. cvs. Indianapolis Yellow and Iceberg produced similar vegetative growth with the same P levels in soil solution. There were cultivar differences in percentages of P in the recently matured leaves. Growth of a ratoon crop of one cultivar required less external P than was required by the plant crop and the internal P requirement of both was less than the same cultivars grown as a plant crop. For “Indianapolis Yellow’, maximum flower diameter was obtained at much lower external P concentrations than was required for maximum total fresh weight.
Abstract
The response of 9 vegetable crops to P concn in the soil solution was determined in field studies on soils with a relatively high capacity for immobilizing P. Adjusted P concentration in the soil solution ranged from 0.003 ppm, doubling at each level, to 1.6 ppm. Most crops produced maximum yields at 0.2 to 0.3 ppm P in soil solution, although transplanted head cabbage (Brassica oleracea L. Capitata Group) and sweet potato (Ipomoea batatas (L.) Lam) produced maximum yields at 0.04 and 0.1 ppm, respectively. At suboptimal P concentration in soil solution, crop response varied greatly. Sweet potato produced about 70% of maximum yield, while lettuce (Lactuca sativa L.) produced about 1% of maximum yield. P levels in plant tissue at 95% of maximum yields ranged from 0.3% in lettuce to 0.7% in Chinese cabbage (Brassica campestris L. Pekinensis Group).