Journal of the Japanese Society for Horticultural Science
Online ISSN : 1880-358X
Print ISSN : 0013-7626
ISSN-L : 0013-7626
Response of Satsuma orange trees to phosphate fertilization in field condition
Tatsuma SAKAMOTOSusumu OKUCHIMinoru MIYOSHI
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1969 Volume 38 Issue 3 Pages 230-238

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Abstract

1. In order to investigate the response of Satsuma orange trees to phosphate fertilization in field condition, P rate experiments were carried out in two orchards on diluvial loamy land of Ehime Fruit Tree Exp. Sta. which had received phosphate fertilizer for past 10 years.
2. One experiment, Exp. 1, was started in 1960 in 11-year-old orchard, and consisted of 4 treatments receiving 0 (P0), 200 (P0.5) and 400g (P1) of P2O5 per tree annually under the mulching of rice straw, and 0 (P0-C) under the clean culture. The superphosphate was buried with the soil into 30 holes of 40cm in depth and 6-7cm in diameter around the trees. The tree vigor and yield were not appreciably affected by P rate during 9 years from 1960 to 1968. Fruit qualities were not greatly different among P treatments until the 5th year and also in the 7th year. Fruits grown on P1 treatment in the 6th, 8th and 9th year showed the delay of color development, and had lower soluble solids and acid content than fruits on P0-C and P0 treatment. Leaf P in P0-C and P0 treatment was maintained at the satisfactory level throughout 9 years period. Phosphate application increased P content of the leaves after the 8th year, but the increase was small.
3. Other experiment, Exp. 2, was started in 1963 in 3-year-old orchard, and consisted of 5 treatments receiving 0 (P0), 430 (P1B), 860 (P2) and 1, 720g (P4) of P2O5 per tree, and receiving 430g (P1A) of P2O5 by the surface application during 6 years. Superphosphate used in the P1B, P2 and P4 treatments was buried into soil layers of 40cm depth in the areas of 1 meter around the trees prior the transplanting. No significant response of tree growth and yield due to P rate occurred during 6 years from 1963 to 1968. After the 4th year, fruits showed that with increased amounts of applied phosphate, soluble solids and acid in juice were lowered, and ratio of soluble solids to acid increased slightly. In the 5th and 6th years, the delay in development of deep orange color became remarkable in fruits grown on high P treatments. No difference in leaf analysis was found until the 4 th year. However, there was the significant increase in leaf P during late 2 years in the P2 and P4 treatments, and the decrease in leaf N and K.
4. The significant difference in fruit qualities between no P and high P treatments was remarkable in 1967 where the rainfall during 6 months from late-spring to mid-autumn was very scarce, attaining only to one-sixth of the average precipitation for recent 10 years. This trend was recognized in both of Exps. 1 and 2. Especially, the decrease of acid content in fruits grown on P1 treatment of Exp. 1 and on P2 and P4 of Exp. 2, was greater than that in fruits grown on trees without the application of K fertilizer for 4 years. Above facts will suggest that the effect of P fertilization on fruit qualities may be accentuated greatly by the climatological condition.

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