頁籤選單縮合
題 名 | 臺灣紅棕壤之若干理化學性質與改良土壤物料對其物理性之影響=On Certain Physico-Chemical Properties of the Reddish Brown Latosol and the Effects of Some Soil Amending Materials on its Physical Properties |
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作 者 | 陳振鐸; | 書刊名 | 中華農學會報 |
卷 期 | 26 民48.06 |
頁 次 | 頁9-30 |
關鍵詞 | 土壤改良物料; 紅棕壤; 化學性質; |
語 文 | 中文(Chinese) |
英文摘要 | The Reddish Brown Latosol is a principal zonal soil of Taiwan, which climate is subtropical with the annual temperature 22℃ and average rainfall 2,500 mm. This soil group have developed mostly on the terrace table land, less than 500 m. in elevation, and the parent materials are mostly consisted of pleistocene rounded gravel mixed with sand or clay deposits, conglomerate, sandstone, shale and andesite. The laterization is regarded as the principal soil forming process, however, the extent and type of weathering depend largely on the kind of parent materials and the intensity of other soil forming factors. The soil series being classified as the Reddish Brown Latosol in Taiwan totalled 23 up to present. The name of the series, parent material, pH value, SiO2/Al2O3 of the clay and location surveyed are shown in table 1. The table shows that the latosols of the northern section of the island have lower pH and Ki values, which indicate that the difference in parent material and a minor change in the climate have eventually affected these chemical properties. The fertility status of the Reddish Brown Latosol in relation to sugar cane, rice, tea and pineapple growing in Taiwan, have been studied extensively by many soil scientists for many years. The literatures of their studies were reviewed and briefly introduced (1, 8, 26, 27, 28, 29, 30). The present investigation was undertaken for the purpose to know the physicochemical properties of the Reddish Brown Latosol more in detail and also to study on the effects of certain soil amending materials on its physical properties. This paper may be regarded as the continuation of the previous study reported (38). The two soil series the Pinchen clay loam and the Ta pu loam, both belonging to the Reddish Brown Latosol were selected as the samples of this investigation. 1. A kaolinitic clay mineral, metahalloysite was identified as the predominent clay mineral in the Pinchen soil by means of DTA, X ray and chemical analysis and also by determining the exchange capacity which was 22 me/100g. These indicated the clay was the intermediate of the halloysite 4H2O and 2H2O form (5,7). It was observed that this kaolinitic mineral has played a significant role in the displaying of physicochemical properies of the latosols. Certain physicochemical properties of two latosols are shown in table 2, 3, 4 and 5. Table 2 and 4 state that the clay less than 1μ occupied the major portion of the clay fraction and the clay content increased in the subsoil. Most of the clay particles have formed slightly hard small fragment. The porosity was high and bulk density was low. Moreover, due to small contact area and activity on the surface between clay particles, the coherence having been exhibited by particles was generally small and let a fragment crumble easily. The soils also showed friable consistence from a moist to dry state and gave a very small plastic number. It was also observed that the soils exhibited a large change in volume during aggregate formation after they were treated with the amending materials. Table 3 & 5 indicate the soils were strong acid in reaction, pH 4.8-4.2; of low exchange capacity, 8-6 me./ 100g; and with the high content of free iron oxide, 3-5%, with content increased in the subsoil. The SiO2/Al2O3 of the clay fraction was 1.5-1.8 The contents of organic matter, nitrogen and available nutrients were low, and ammonification and nitrification were weak as compared with those of other soil group (32). The phosphorus fixing power was found extraordinarily high (37). 2. It was observed that the latosols had a large portion of coarser pores which diameters were larger than 8.52μ(0.33 Atm.), as well as a large amount of very fine pores with diameters less than 0.19μ(15Atm.). Consequently, the soils ahowed good aeration and percolation on one hand, and exceedingly small content of available water and the easy access of soil moisture to the wilting point in a short interval of drying period on the other hand. The subsoil which contained a high percentage of clay and of poor structure gave an extraordinarily low content of available water. A proper measure should be taken to correct such a poor moisture characteristic when the subsoiling of a latosol will be practiced. The phase distribution of the latosol profiles was obtained by the sampling of undisturbed cores and the investigation of the tension and moisture content relationship. The results are shown in fig. 1 & 2. These reveal that the soils contained within the profiles comparatively large percentage of non-capillary pores (diameter greated than 50μ: 0.06 Atm.). And the pores that existed within the capillary pores (diameter smaller than 50μ) and contained available water, comprised only a minor portion. From this finding, it may be expected that in a field condition, a latosol may also exhibit such characteristics, i.e. good aeration and water percolation, large loss of moisture and plant mutrients and very low content of available water. Meanwhile it was observed that the surface soil, with higher content of organic matter and better structure, contained a larger amount of available water. This denotes there may be still a possibility to improve the moisture characteristics of the soil. The phase distribution within the soil profile of tea field and that of uncropped field are shown in fig. 1, A & B. By comparing A and B, it may be noted that in the A, the percentage of non capillary pores was significantly larger at the portion where roots had made the most vigorous growth. This indicates that the growing of trees or perennial grasses may increase the non capillary pores of a latosol and is beneficial for storing water and preventing surface erosion. Besides, they cover soil surface to diminish the loss from evaporation. 3. The results from the experiments on the effects of soil amending materials, VAMA, Ca(OH)2, compost and green manure, may be summarized as follow: a). VAMA showed significant effect on the aggregate formation or the Y value, as shown in table 6 and fig. 3. This gave more pronounced effect in a coarse texture soil. Ca(OH)2 and compost did not show noticeable effect in aggregate formation. However, green manure exhibited significant effect, and its function on aggregate formation was similar to VAMA. b). With respect to the effects of these materials on modulus of rupture, which are shown in table 7, it was indicated that VAMA brought the most pronounced effect in the decrease of rupture value. While green manure was the next. Ca(OH)2 also decreased the rupture value, but there was no consistent relation between the amount added and the change in rupture value. Applying a small amount of compost decreased the rupture value, but, when the amount was increased, the rupture value was increased also. This may be due to the cementation of soil particles through the organic gels of compost. c). The effects of materials on volume change of the soils, △V% and on the bulk density of the puddled soils, P2 are shown in table 8 and fig. 4. This indicates that VAMA significantly increased the △V% and decreased the P2 values, and its effect was specially remarkable in a coarse texture soil. Ca(OH)2 brought a limited change in △V% and decreased the P2 value. As for compost, when it was added in a clayey loam, there was no effect neither on the △V% nor on the P2 values, but when a large amount of compost was applied in a loam, the △V% valus was remarkably decreased showing shrinkage had happened. This result may explain why the rupture value in the previous experiment was increased through the same treatment. Green manure did not show pronounced effect in a clay loam, but in a loam, it did increase the △V% and decreased the P2 value. These results agreed closely with those of VAMA. d). The effects of these materials on the moisture contents under 0.33 Atm. and 15 Atm. tensions were investigated. The results shown in table 9 and fig. 7. indicate that the effects of VAMA and green manure on the available moisture content of the latosols were alike. The addition of both materials did not increase the available moisture content of the soils, while Ca(OH)2 and compost did not give a consistent result. 4. The examination of the present and past experiment (38) revealed that following properties may be mentioned as the paricular physical characteristics of the Reddish Brown Latosol, i.e. (1) large content of stable aggregate, (2) friable consistence exhibited in a wide moisture range, (3) small plastic number, (4) small content of available water. The experiment results in fig. 3 & 4 and table 10 & 11, denote the significance of these properties and the effects of soil amending materials on these properties as compared with those of an old alluvial soil. In addition, a discussion on the causes and functions of these properties and their bearing on soil management were presented. 5. During the investigation, it was observed that there was a striking difference in the effect between green manure and compost. The effects of the two materials on the Y value, modulus of rupture, △V%, P2 values and the available moisture content are shown graphically in figure 5, 6 and 7. It was observed that green manure was much alike VAMA in the function, and gave higher Y value, lesser modulus of rupture, greater change in △V%, lesser P2 value than that compost gave. It was conclued that fresh green manure would exert a better effect than that of compost on the physical properties on the latosols. |
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