<departmental bulletin paper>
Correlations between Nitrogen Mineralization Potential or Mineralization Rate Constant and Physicochemical Properties of Paddy Soils

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Abstract 可分解性有機態窒素量(N_0)と無機化速度定数(k)は,水稲の生育期間において地力窒素の無機化量を推定する際に用いられる主要な特性値である.しかし,N_0 とk は時間と労力を要する培養試験によって決定されるため,施肥設計に利用する観点からは簡易に推定することが求められる.そこで本研究では,N_0 とk の簡易推定を検討する際の基礎資料を提示するために,未風乾水田土壌のN_0 およびk と土壌の理化学性の指標の相関関係を明らかにした.まず,福岡県糸島市の16 筆の水田土壌について,反応速度論的解析法によりN_0 とkを算出した.次に,土壌の理化学性の指標の中で,CHN コーダー等で簡易に測定できる全窒素(TN)と全炭素(TC),もしくは一度測定した値を経年的に使用できる粘土・シルト・砂含量ならびに陽イオン交換容量(CEC)とN_0 およびk の相関解析を行った.その結果,N0 についてはTN がr =0.602 の1% 水準で有意な正の相関を示した.TC,粘土含量およびCEC が,それぞれ,r =0.569,r =0.526 およびr =0.431 の5%水準で有意な正の相関を,砂含量はr = − 0.504 の5%水準で有意な負の相関を示した.k については,砂含量がr =0.481 の5% 水準で有意な正の相関を,シルト含量がr = − 0.460 の5% 水準で有意な負の相関を示した.ただし,k と砂含量およびシルト含量の有意な相関は,その分布範囲が広い場合に限り示されることが示唆された.
Nitrogen mineralization potential (N_0 ) and mineralization rate constant (k) are major parameters used to estimate soil mineralizable nitrogen during the rice growth period. These parameters are determined with soil incubation tests, which are laborious and time-consuming. Thus, simple estimation of N _0 and k are required to use the parameters for planning fertilizer applications. The objective of this study was to investigate correlations between N0 or k of moist paddy soils and soil physicochemical properties. First, N_0 and k were calculated using kinetic analysis for soils collected at 16 paddy fields in Itoshima city, Fukuoka Prefecture. Next, correlations were analyzed between N_0 or k and soil physicochemical properties including total nitrogen (TN), total carbon (TC), clay, silt, sand contents, and cation exchange capacity (CEC). TN and TC are simply measured with a CHN analyzer, while clay, silt, sand contents, and CEC can be referred over years when the properties are measured once. For the relationship with N_0 , TN showed a positive correlation (r =0.602) at 1% significance level. TC, clay content, and CEC showed positive correlations (r =0.569, 0.526, 0.431, respectively) at 5% significance level, while sand content showed a negative correlation (r = − 0.504) at 5% significance level. For the relationship with k, sand content showed a positive correlation (r =0.481) at 5% significance level, while silt content showed a negative correlation (r = − 0.460) at 5% significance level. The result implicated that the correlations between k and sand or silt content are significant only when the ranges of the values are large.
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Created Date 2017.10.10
Modified Date 2017.10.12