• 作者： 高德錚; 林安秋
• 作者服務機構： 台中區農業改良場; 國立台灣大學農藝研究所
• 中文摘要： 著者在高屏地區進行5年之生態調查後，由616個取樣點之土壤肥力與禾根豆根瘤發育之關係，可歸納成下列幾個結論： (1)在播種後，豆農將前作稻草覆蓋於上，而在翌年春作水稻插秧前，將稻草翻埋至土中。此種添加稻草之栽種方式，是造成該地區土壤有機質含量豐富，平均值為3.46%之原因。 (2)在禾根豆生長至生育期間，土壤全氮量高達0.181%，且可交換性氮亦達44.9 ppm，而其中佔75%。此乃因豆農在一、二期水稻種植期間，施用重氮肥及禾根豆栽培時又外加20～50 kgN/ha 所致。 (3)由統計資料顯示，當土壤之可交換性氮小於 37 ppm 時，氮素含量之增加可促進禾根豆根瘤之結瘤數，反則呈現嚴重之抑制現象。 (4)高屏地區的土壤有偏酸的現象，當土壤 pH 值低於5.2時，禾根豆之結瘤數顯然受到抑制。不過，著者發現根圈土比表土 pH 值高約0.6個單位。根圈土與表土之 pH 差值（△pH）越大則越有益於植株根瘤之形成。
• 英文摘要： The relationship between effective-ness of soybean nodules and soilfactors were under a five-year's studies.Soil samples were collected from 616locations of Kao-Ping area where farmersalways spread rice straw over paddyfield immediately after soybean sowingand then to turn it over at the begin-ning of next spring rice crop. Thisannual rice straw mulching practiceresulted in enriching soil organic mattercontents (OM). However, a heavysupply of 20-50 kg N/ha tended toincrease total nitrogen (TN) and totalexchangeable nitrogen (TEN）of soil.The increases in nodular effectivenesswere related to the comcomitant increa-ses in soil OM, but inverted to decreasein soil TN. Influences of TEN on nodulareffectiveness were distinguished withtwo interaction patterns. It was apparentthat nodular effectiveness was severelyretarded when soil TEN was over 37 ppm.Besides, acidic soil also played a roleto lower nodular effectiveness whilesoil pH value was less than 5.2. ThepH value of soybean rhizosphere (p)was 0.6 unit in average higher thanthat from surface soil (p). This extra0.6 unit was significant to affect innodular effectiveness. The above resultsindicated that heavier nitrogen applica－tion and acidic soil were of two majorfactors which caused nodular effective-ness to a lesser extent.
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