(Bulletin No.4) A Study On The Use Of The Plaster Of Paris Absorption Block Electrical Resistance Method For Measuring Soil Moisture

Abstract

在五種不同構造之焦石膏電極中，以容積為6.2×3.6×0.7cm，鎳線長度為30cm之E型電極示最佳之成績，因此類電極之水份_電阻變化銳敏，適宜於土壤有效水份之測定。 對各種土壤之水份當量，E型電極指示之電阻為70-100歐姆，對枯萎係數約為1000-7000歐姆，在此有效水份範圍內，土壞水份＿電阻之變化均甚顯著，且於數次重複巾均獲得同樣結果。 溫度對電阻測定有影響，在50℃至5℃必間，電阻隨溫度之降低有逐漸昇高傾向，惟共變化甚緩，且較一致，5℃以下則有加速度之進展。溫度每昇降一度，由於電阻之變異而引起之上壤水份差異，在粘土中約±0.1%在壤土中則僅0.03%而已。 The use of the plaster of paris absorption block electrical resistance method f or measuring soil moisture has already been studied and improved by G. Bou-youcos, Alfred B. G. Anderson and N. R. Edlefsen and others. The present investigation was carried out by limiting the purpose to the following points:- (a the proper construction of the electrode used in the absorption block, (b) the conditions and corrections needed for the measurement