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The Science Bulletin of the Faculty of Agriculture. University of the Ryukyus >
No.25 (1978/12) >

Title :沖縄における農地保全の基礎的研究 VII : 国頭マーヂの土壌侵食標準試験区における流亡土量について(農業工学科)
Title alternative :Fundamental Studies on Farmland Conservation in Okinawa VII. : The Relationship Between Soil Loss and Rainfall Energy on Standard Soil Erosion Testing Plots (Department of Agricultural Engineering)
Authors :翁長, 謙良
Authors alternative :Onaga, Kenryo
Issue Date :1-Dec-1978
Abstract :本研究の観測期間中(昭和52年6月1日∿53年4月30日)における連続13mm以上の降雨回数は34で, それらの総和は約2,000mmであるが, その中で2回連続降雨の場合を除き, 毎降雨ごとの流亡土観測可能回数が27回であるが, 実際は欠測や2∿3回の降雨による1回の観測等もあって, 13回(20回降雨回数)の観測をもとにまとめたものである。結果は次のように要約されよう。1)観測期間中の降雨エネルギーは924(10^3mmt/ha・hr.)であり, Table 4のその期間の平均値689をはるかに上回るものである。2)観測された流亡土量(t/ha.)は8度区, 5度区, 3度区でそれぞれ506,353,202,であり土壌の仮比重(1.4)をもとに土層厚に換算するとそれぞれ3.6cm, 2.5cm, 1.4cmとなり極めて大きい侵食量といえる。3)一般に傾斜度が増せば流亡土量も増大する。4)降雨エネルギーと各傾斜別の流亡土量との間にはY=aX^bの関係が成り立ち, 特に5度区と3度区はXとYの相関が比較的高い。
This study has been done in order to establish criteria and guidelines applicable to field problems in northern parts of Okinawa, which excell in Kunigami Maji soils. These soils are usually acidic, infertile and erosive physically but productive of both pineapple and tea. The textural composition and physical properties of the soils are shown in Table 1. Three field plots have been selected for soil erosion experiment at Yaka, Kin-son. The plots were set at inclines of 8(A), 5(B), and 3(C) degrees, respectively. The period of observation is from June, 1977 to April 1978 and the rainfall of the area was calculated for this period. The data obtained are as shown in Table 5. The results of this observation are as follows : 1. The rainfall at Yaka was 924 (10^3mm tm/ha, hr, ) during the period of observation and this amount surpassed the annual average rainfall (689) in Naha. 2. The soil loss from the plots A, B, and C is 506t/ha. 353t/ha. and 202t/ha. respectively. 3. Generally, the soil loss increases with the increase of inclination. 4. The relationship between the amount of rainfall and the loss of soil is formulated as the equation Y=aX^b, where Y is soil loss in tons per ha. and the rainfall in 10^3mm・m・t per ha. hr.
Type Local :紀要論文
ISSN :0370-4246
Publisher :琉球大学農学部
URI :http://hdl.handle.net/20.500.12000/4209
Citation :琉球大学農学部学術報告 = The Science Bulletin of the Faculty of Agriculture. University of the Ryukyus no.25 p.351 -359
Appears in Collections:No.25 (1978/12)

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