北海道に分布する各種黒ボク土による硝酸イオンの吸着が移動速度に及ぼす影響  [in Japanese] Relative velocity of nitrate transport as affected by adsorption in different Andosols in Hokkaido  [in Japanese]

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Abstract

北海道に分布する主要な黒ボク土について,陰イオン吸着に伴うNO_3^-の水移動に対する相対移動速度の低下およびNO_3^-吸着に及ぼす土壌化学的特性の影響をカラム浸潤実験により層位別に調査するとともに,相対移動速度の低下が畑地土壌におけるNO_3^-の下方移動に実効的に機能するかどうかを検証した.NO_3^-の水に対する相対移動速度はほぼ0.5〜1の範囲にあり,土壌のNO_3^-吸着能が大きいB,C層で最も小さく,B,C層≦埋没A層<Ap層の順に大きくなった.NO_3^-の相対移動速度は酸性シュウ酸塩可溶ケイ素(Sio)含量と高い負の相関関係を有し,Ap層ではTruog-P含量が,埋没A層では全炭素含量が増加するにつれて高まった.埋没A層およびB,C層では.NO_3^-の相対移動速度と吸着態SO_4^<2->含量の間にも高い負の相関関係が見られた.また,B,C層での相対移動速度は,母材である火山噴出物の降下年代が古くなるにつれて2,000〜3,000B.P.まで顕著に低下し,6,000B.P.以前ではほぼ一定または逆に上昇する傾向が見られた.さらに,埋没A層およびB,C層では噴出源の違いによる差異も認められた.各層位でのNO_3^-の相対移動速度は,Ap層ではSio含量,粘土含量およびTrumg-P含量を,埋没A層ではSio含量,全炭素含量および吸着態SO_4^<2->含量を,またB,C層ではSio含量および吸着態SO_4^<2->含量をそれぞれ説明変数とする重回帰式によって推定が可能であった.圃場条件下においても,NO_3^-吸着能が大きく,水に対するNO_3^-の相対移動速度が小さい下層土を有する千歳土壌では,NO_3^-吸着能の小さい恵庭土壌に比べてNO_3^-の下方移動が明らかに遅れる傾向があった.これらの結果から,土壌によるNO_3^-の吸着と相対移動速度の低下が,施用NO_3^-の下方移動の抑制に実効的に働くことが明らかになった.

Retardation of nitrate transport due to adsorption and its effects on nitrate leaching in the fields were investigated in different Andosols in Hokkaido. Seventy-five agricultural soils differing in the soil horizon and source ejecta were repacked into columns, and one-dimensional unsaturated flow experiments were conducted by supplying 2.3-11.5mM Ca(NO_3)_2. Retardation of nitrate transport was determined from the water and nitrate content profiles in the columns, and correlated with routinely-determined soil properties. The velocity of nitrate relative to water, averaged for soils grouped with respect to the soil horizon and source ejecta, ranged from 0.58 to 1.00, with the general order of B, C&le;buried A<Ap horizons. A highly negative correlation was observed between the relative velocity of nitrate and the acid oxalate-extractable Si content (Sio). Except for the Ap horizons, the relative velocity was negatively correlated (significant at 1% level) with the adsorbed SO_4^<2-> content, which could stand proxy for the anion exchange capacity of the soils. Nitrate velocity in the B, C horizons was also affected by the type and age of source ejectas, with the retardation increasing with age for the source ejectas younger than 2000-3000y. Truog-P and total carbon contents were found to increase the relative velocity of nitrate in the Ap and buried A horizons, respectively. Based on these results, multiple regression equations were developed for predicting the relative velocity of nitrate from Sio, clay and Truog-P contents for the Ap horizons, from Sio, total carbon and adsorbed SO_4^<2-> contents for the buried A horizons, and from Sio and adsorbed SO_4^<2-> contents for the B, C horizons. Nitrate leaching observed in two Andosol fields was in accord with the laboratory assessments, and demonstrated that nitrate adsorption can effectively retard the downward transport of nitrate in the Andosol fields.

Journal

  • Japanese Journal of Soil Science and Plant Nutrition

    Japanese Journal of Soil Science and Plant Nutrition 80(4), 365-378, 2009

    Japanese Society of Soil Science and Plant Nutrition

References:  31

Cited by:  2

Codes

  • NII Article ID (NAID)
    110007504043
  • NII NACSIS-CAT ID (NCID)
    AN00195767
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • ISSN
    0029-0610
  • NDL Article ID
    10405261
  • NDL Source Classification
    ZR7(科学技術--農林水産--農産)
  • NDL Call No.
    Z18-331
  • Data Source
    CJP  CJPref  NDL  NII-ELS  IR  J-STAGE 
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