中部粘板岩沖積土性質與水稻生長及產量之關係研究

Abstract

為明瞭中部粘板岩沖積土性質與水稻生長及產量之關係，在濁水溪灌溉區域內溪州、田尾、西螺及北斗四鄉鎮，每鄉鎮各依當地水稻產量高低選取二處，共計八處，其中包括粘板岩新沖積土一及舊沖積土七，分屬六種不同土系，同時進行田問及溫室水稻栽培試驗。 溫室試驗分施肥與不施肥兩處理，共5重復，計8×2×5=80盆，依完全逢機法分8行排列於溫室內。其中2重複計32盆專供水稻生育期中採取植株，供植物分析用；另3重複則為生育觀察，產量記錄，並於盆底側裝玻璃管，定期採取土壤溶液作物理化學測定。 分析項目除土壤一般性質測定外，並於水稻生長期中定期作土壤溶液及植株分析，以明瞭土壤養分供給量與水稻生長及吸收之狀況，收穫後稱量穀、藁重量，並作植物分析。 本試驗所用8土壤中，產量最高者為西螺東興里、溪州東州村與北斗中寮里3土壤；最低者為西螺茄茗里與田尾溪頂里土壤。一期作中，產量最高與最低者相差幾達一倍；二期作則僅達24%左右。 由水稻插秧後至出穗時止，每兩星期所作土壤溶液分析結果，知穀產量與土壤溶液中PH及HCO3-含量關係最為密切，多呈顯著負相關關係。 本試驗所用土壤PH在6.2至7.8之問，部分屬於鈣質土壤(Calcareous soil)，經浸水插秧六星期後，各土壤PH約在6.2至7.3之間，PH差僅約1單位，PH本身對作物生長影響並不大，但PH能影響土壤溶液中其他元素的含量，而間接及於作物的生長。由本試驗所得資料計計算結果，知土壤溶液中PH與HCO3-及Ca2+、Mg2+含量成顯著正相關關係，而與NH4+、K+及Fe2+含量則成顯著負相關關係。 由本試驗水稻生長期中所作植物分析結果與同時期內土壤溶液中各相關元素含量間的關係比較，知植物體內鉀含量與土壤溶液中HCO3-含量成顯著負相關關係，則本試驗中，土壤溶液內HCO3-量確已達阻礙植物對鉀吸收的濃度。又植物體中磷的含量與土壤溶液中PH成極顯著負相關關係。顯示在本試驗中，PH較高土壤內，作物對磷的吸收已受阻礙，此或由於當土壤在PH 7以上，鈣的含量亦高，土壤中過量的鈣更能阻礙作物對磷的吸收及利用。 是則中部粘板岩沖積土部分低產地區的低產原因，應係由於水稻生長期中土壤溶液內所產生過量的HCO3-、Ca2+及Mg2+所導致。 To evaluate soil characteristics of the slate alluvial soils in central Taiwan as related to the growth and yield of rice, a greenhouse experiment was carried out simultaneously with a field trail. Eight soils were selected from Cho Shui irrigation area, including both new and old slate alluvial soils belong to six different soil series (This report includes only the greenhouse experiment). Two treatments (with and without fertilizer) with five replicates, a total of 80 pots were arranged in eight rows in a completely randomized design in the greenhouse. The fertilizers used in the first crop (April to August)were N, 100 ppm, P, 50 ppm, and K, l00 ppm as ammonium sulphate, calcium superphosphate and potassium chloride respectively. It was the same in the second crop (August to December) except that of K was only 50 ppm. The items analyzed in this experiment were soil properties, soil solution determination and plant analysis in both the vegetative and reproductive phase of the rice plant. After harvesting, the yield and yield components were recorded and the straw and grain were analyzed. Of the eight soils used in this experiment, the highest yielding soils were soils No. 4, 2, and 7. The lowest were soils No. 3, and 5. The difference was much wider in the first than in the second crop. A very significant negative correlation was found between grain yield and the pH values and HCO3- content in the soil solution in most of the sampling period. The pH values of the eight soils used ranged from 6.2 to 7.8, some of them were calcareous soil. Six weeks after transplanting, the pH values were between 6.2 and 7.3, a difference of only I unit. Though pH per se generally is not regarded as an important factor in affecting plant growth, it influences the nutrient content in the soil solution, thus, affecting the growth and yield of the rice plant. It was found in this experiment that the pH values in the soil solution were significantly correlated with the HCO3-, Ca2+ and Mg2+ content in the soil solution, but negatively correlated with the NH4+, K+ and Fe2+ content in the soil solution. By comparing the relation between nutrient content in plant tissue during the course of plant growth and the related nutrients in the soil solution of the same period, it was found that the K content in the rice plant was negatively correlated with the HCO3- content in the soil solution. This shows that the HCO3- content in the soil solution of some of the soils in this experiment did reach the level to retard potassium uptake. The phosphorus content in the rice plant was also found negatively correlated with the pH values of the soil solution. Phosphorus absorption was retarded in some of the soils with higher pH values in this experiment. It is due to the fact that when pH values is above 7, the excess calcium may further hinder phosphorus absorption and utilization. In conclusion, the low yield of some slate alluvial soils in central Taiwan may be caused by the abnormally high concentrations of HCO3-, Ca2+, and Mg2+ produced during the course of rice growth.