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|Title:||Effects of dehydration and heavy liming on plant nutrition in the amorphous and crystalline tropical soils of Hawaii|
|Authors:||Rana, Sarit Kumar|
|Keywords:||Soils -- Hawaii|
Liming of soils
Plants -- Nutrition
|Abstract:||The soils of the Akaka and Puhi families represent advanced stages of two fundamental processes of tropical weathering. These processes have been described by Sherman (1949). The Akaka soils (Hydrol Humic Latosol), under extremely high rainfall of 150 to 500 inches per year and with no dry month, have developed into soils dominated by highly hydrated amorphous oxides rich in alumina. Descriptions of these materials fit with the definition of allophane, which was found to increase with rainfall (Tamura et al., 1953). Allophane has been found to be of common occurrence in soils of the Pacific belt area, and it imparts certain characteristic properties to the soils. Low bulk density, high water holding capacity, medium to high exchange capacity, highly acidic reaction, high exchangeable aluminum, highly retentive to applied phosphates and irreversibility of drying are some of the common properties reported. The Puhi soils (Humic Ferruginous Latosol) on the other hand, are the products of an alternate wet and dry system. Here, the dehydrated forms of iron and titanium mostly predominate. The soil properties are accordingly characterized by a high particle density, a dense AZ horizon underlying a concretionary surface soil, reduced specific surface and reduced reactivity of iron and aluminum. The presence of amorphous hydrated oxides is exhibited by properties of irreversible drying. Retention of applied phosphates is also a problem in these soils. Dehydration of the Akaka soils has been found to give rise to the formation of gibbsite minerals (Sherman, 1957). The crystallization of amorphous colloids may reduce soluble and "available" aluminum in the soil and decrease or eliminate a "toxic" concentration of this element. Similar changes may occur in the Puhi soils under dehydration, with respect to iron and titanium availability in the soil. Further, the crystallization process may change the nature and form of phosphate retention and improve fertilizer efficiency and availability. Physical conditions like drainage, aeration and bearing capacity are known to improve with increased degree of crystallinity. Liming of acid soil is a relevant approach to improve mineral nutrition and plant growth. This is related to (a) solubilities of iron, aluminum, titanium and manganese, (b) availabilities of calcium and magnesium, (c) availabilities of phosphates and potassium, (d) solubilities and availabilities of trace elements and (e) population and activities of micro-organism (Coleman et al., 1958). Liming response in Hawaiian agriculture have been controversial. Liming has been found beneficial for sugarcane only when soil calcium was below 100 ppm (Ayres, 1961). Yet, some experimental evidence reveals a liming response over and above that of supplying calcium as a nutrient (Clements, 1961). This response may be attributed to the reduction in aluminum solubility and the concentration of this element in the plant nodal and root tissues. Aluminum in the plant may interfere with normal metabolism in various ways; enzyme activities, uptake and translocation of nutrients, movements of water and solutes, etc., have been mentioned and discussed. Similar behavior could be expected with respect to iron and titanium. Exchangeable manganese has been reported to be high in some Hawaiian soils but the level decreases sharply with liming. The solubilities and availabilities of iron and aluminum in the soil are tied up with phosphate nutrition and fertilizer efficiency. By way of precipitation' double decomposition and chemi-sorption these elements interfere with phosphate availability. In soils dominated by a large fraction of amorphous hydrated oxides of iron and aluminum, liming may become ineffective in completely preventing these elements from complexing phosphates, even at an increased pH (Sherman, 1962). Further, some of these soils show very high buffering capacities (Matsusaka and Sherman, 1950). Therefore, phosphate nutrition in these soils becomes a difficult problem. It could be speculated that heavy liming may bring about with time an increased degree of crystallinity in the hydrated amorphous fraction of these soils. Dehydrated and crystalline oxides of iron, aluminum and titanium have been shown to be comparatively inert and less reactive to phosphates. Calcium silicate has been found to be effective in improving phosphate nutrition in the Humic Latosols of Hawaii. These soils are low in 2:1 layer silicate clays. Silicate application has been found to be beneficial in Puhi soils under some field experimental conditions. Responses to silicate application has been explained by its replacing and solvent action on soil phosphates. Its effectiveness has been especially noted on phosphate deficient soils. Finally, phosphate carriers of varying solubility may interact with liming materials under different soil systems. With the above background, the present experiment was conducted with the following objectives: 1) To investigate the effects of dehydration (air-drying) on Akaka and Puhi soils in regard to their aluminum, phosphorus and manganese status, and to plant nutrition; 2) To investigate the effects of heavy liming in undried and air-dried systems on the degree of crystallinity as may be reflected by phosphate and aluminum availabilities and plant growth; 3) To investigate the effects of calcium silicate and coral stone and their interactions with different soil systems to gain an insight into the phosphate retention mechanisms in these soils; and 4) To obtain an insight into the relative efficiencies of two different phosphate carriers applied in conjunction with different liming materials to varying soil systems.|
Thesis (Ph. D.)--University of Hawaii, 1964.
Bibliography: leaves -157.
xiv, 159 l tables, mounted graphs
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|Appears in Collections:||Ph.D. - Soil Science|
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