Ph.D. - Soil Science

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Effect of the use of lime and other soil amendments on amorphous and differentially crystallized subsoil of the Akaka series
(University of Hawaii at Manoa, 1965) Dias, Irwin Patrick Solomon
While calcium has long been known as an essential macro-nutrient for plants, it has had the distinction of having been used as a soil ameliorating agent from the very beginning of organized soil husbandry (Thompson, 1957). Calcium is ascribed several roles in plant nutrition, among which is its role in the formation of cell wall constituents, that of nitrogen metabolism and as activator of several enzyme systems. (Meyer et al., 1960). Even so, Fried and Peech (1946) discussing calcium as a nutrient, carne to the conclusion that supplying calcium as such was not important, on the probable assumption that most well-cultivated agricultural soils have a sufficient supply of calcium for nutritional purposes. Thus, it is no surprise that most of the work done with calcium has been on its role as a soil ameliorating agent, or as a liming material on acid soils, for promoting the growth of certain crops. Under the general term of lime, many materials, such as calcium carbonate, hydrated lime, dolomitic limestone, silicic slags of various descriptions, crushed serpentine rocks, cement kiln dusts, etc., have been included. Numerous reasons have been adduced by several workers for the ameliorating effect of these soil amendments in relation to the growth of specific plants on these acid soils. Among these, some of the more important are: a) Promotion of more favorable soil physical conditions (Coleman et ~, 1958). b) Improvement in the fixation of nitrogen by improved soil microbial activity (Black, 1957). c) Beneficial effect of phosphorus release from the breakdown of organic phosphates (Ghani & Aleem, 1942). d) Reduction of phosphorus fixation in soils (Mitscherlich, 1947). e) Reduction of toxic levels of manganese and aluminum in soils (Mulder & Gerretsen, 1952). f) Increasing the general effectiveness of other elements (Truog, 1953). The literature also gives ample evidence of injury to crops due to overliming (Richardson, 1951; Russel, 1961). In tropical soils, while a great deal of research has been concentrated on the amelioration and utilization of leached-out acid soils, nevertheless many gaps as in a "jigsaw puzzle" yet remain to be filled. 111is situation is best illustrated in the words of Schmehl et al., (1950) " . . . the poor plant growth associated with acid soils is a complex function of many contributing factors, all of which may be modified by liming. Not until the relative importance of the different beneficial effects of liming acid soils is fully evaluated will it be possible to make the most intelligent use of lime . . ." As for the research findings reported in this thesis, it must be pointed out that much work has already been done on the amelioration with lime of these Akaka soils (Monteith, 1961; King, 1961; Rixon, 1962; Clements, 1962, 1963; Reddy, 1964; Rana, 1964). The present work is thus an extension of the work already done, in which Akaka subsoil (2-5 feet depth) has been investigated. The main areas where the work to be reported here would contribute to additional. knowledge are: a) The laboratory study of the progressive dehydration of these soils from the state of field moistness to complete dryness, with respect to certain chemical, physical, as well as mineralogical changes. b) Use of these soils at three different moisture levels (moist, 50% moist, dry)1 for studying their response to liming. This is the first time that an intermediate moisture level has been investigated in fertility studies in these soils. c) An investigation concerning the physical mixing of the moist and dry soils in varying proportions with respect to response to lime and plant growth. d) The use of crushed Olivine Sand as a soil amendment, since this material is found occurring in abundance in the Hawaiian islands. It would prove to be an economic soil amendment if found efficacious. In addition to crushed Olivine sand, crushed coral rock and calcium silicate (TVA) was also investigated.
The genesis of certain Hawaiian palaeosols and their alteration following burial
(University of Hawaii at Manoa, 1963) Beckmann, G.G.
Effects of heavy applications of lime to soils derived from volcanic ash on the humid Hilo and Hamakua coasts, island of Hawaii
(University of Hawaii at Manoa, 1962) Rixon, Alan James
The humid tropics provide an environment conducive to active alteration of geological material. Volcanic ash with its high porosity and extensive specific surface area weathers rapidly under these conditions. There is a heavy loss of silica and bases and an accumulation of iron and aluminum compounds. The resulting soils have a low content of crystalline clay minerals in the clay fraction, an acid reaction and a low base status particularly in regard to calcium. Soils derived from volcanic parent material are of considerable agricultural importance in the humid tropics. Abundant sources of lime in the form of coral stone often occur in the vicinity of these acidic soils. Thus an understanding of the effects of lime application to such soils is desirable. In their natural conditions the soils of the humid tropics support a dense vegetation. Lumber is a natural product from such locations. Where there is favorable topography the natural vegetation is often replaced by agricultural crops and pastures. Modifications, which may include liming of these soils are often necessary to obtain the most efficient production of these introduced species. Liming in the temperate regions has been intensively studied. At this stage there is a fairly comprehensive knowledge of the effects of liming on the soils of these latitudes. Frequently, these studies have been conducted with soils having a high percentage of crystalline clay minerals in their clay fraction. Only sparse and fragmentary knowledge regarding the effects of liming in the humid tropics is available. The existing information is often concerned with relatively light applications of lime. The soils derived from volcanic ash, in this study, are located on the humid Hamakua and Hilo coasts on the Island of Hawaii. They are used for growing sugar cane. A series of lime phosphate experimental plots has been installed on the Hilo and Hamakua coasts, with tie aim of increasing the yields of sugar cane. The high aluminum content and low pH values of these soils present the possibility that toxic amounts of aluminum may be a limiting factor in plant growth. These soils are highly amorphous, having a high capacity to fix phosphates, thus making them sparingly soluble for plant use. It is suggested that benefits to sugar cane, because of heavy liming of these soils, are due to either the reduction of the toxic effects of aluminum or improved phosphate availability. In the latter case, applied lime may produce a liberation of fixed phosphate, or reduced fixation when phosphatic fertilizers are added simultaneously, or a combination of both these effects could occur. Accordingly, in the present study, the effects of heavy lime application on the soil properties, leaching losses, and presence of various elements in sugar cane tissues were investigated. Inasmuch as little information in regard to soil modifications and sugar cane response to heavy lime applications is available, the investigation of this problem appeared worthwhile.
Nitrogen nutrition of the pineapple plant, Ananas comosus (L.) Merr., soil nitrogen status, and dynamics of the reniform nematode population, Rotylenchulus reniformis Linford and Oliveira, in relation to the form of nitrogen fertilizer, soil acidity, and fumigation
(University of Hawaii at Manoa, 1969) Englerth, Edward Jerome
Unpublished studies in the files of the Pineapple Research Institute of Hawaii indicate that under present cultural conditions the .pineapp1e plant displays superior performance with a foliar applied combination of ammonium and nitrate nitrogen than with either form of nitrogen alone. The studies presented here were undertaken to evaluate ammonium nitrate as a nitrogen source under different soil pH levels and fumigation regimes, using soil application of the carrier rather than foliar sprays. The studies compared ammonium nitrate with the all-ammonium fertilizer ammonium sulfate and the all-nitrate fertilizer calcium nitrate at rates of 100, 200, and 300 1b/A, using soil pH values of 4.5 and 5.5. Fumigation used in conjunction with the nitrogen sources included no fumigation, fumigation with 1,2-dibromo-3-chloropropane at 3 gal/A, and fumigation with a mixture of 1,3-dichloropropene and related hydrocarbons at 40 gal/A. A separate experiment was set up using the high and low rates of nitrogen to examine the effects of carriers and soil pH on reniform nematode numbers in the absence of fumigation. All experiments were of randomized complete block design with a factorial arrangement of treatments. Plants supplied with ammonium nitrate exhibited a slightly greater uptake of total nitrogen, no difference in protein nitrogen, a soluble nitrogen fraction intermediate in size, and a medium to high nitrate content compared to plants on all-ammonium and all-nitrate nutrition. Leaf calcium remained high compared to plants supplied with the other nitrogen carriers. The relative status of the nitrogen forms supplied was not changed by soil fumigation, though soil nitrification was greatly inhibited, resulting in a greater soluble nitrogen content in plants supplied with the ammonium carriers. The concentration of available soil manganese was increased by fumigation. For reasons not known, both liming and increased rates of ammonium sulfate tended to decrease reniform nematode populations in the absence of soil fumigation.
Root properties of sugarcane (Saccharum officinarum) in relation to nutrient uptake
(University of Hawaii at Manoa, 1969) AbuZeid, Mohammed Osman
An investigation was undertaken to select the appropriate methods and sampling times for measuring root cation exchange capacity (C.E.C.) and anion exchange capacity (A.E.C.) and these together with root weight and root surface area index (g saturated calcium nitrate solution covering the root surface) were related to the total uptake of N, P, K, Ca, Mg, Si and S by four sugarcane varieties (HSO-7209, HS7-5174, NCo 310, and HS6-5840) grown in solution and soil culture. The three methods selected for measuring root C.E.C. in decreasing order of differentiation between varieties, were equilibration of Ca45 with chilled fresh roots, exchange of Ca40 with chilled fresh roots and a titration method using ground dry roots. Displacing P from P saturated fresh roots with NaOH solution was appropriate in differentiating reproducibly between varieties, for measuring root A.E.C. The root C.E.C. and A.E.C. results were expressed as weight C.E.C. or A.E.C. (m.e./100 g dry roots), surface area index C.E.C. or A.E.C. (m.e./100 g saturated calcium nitrate solution) and C.E.C. or A.E.C./pot (m.e./ pot). Root type (sett or shoot) had no effect on root C.E.C. values. The C.E.C. for sett roots increased with increasing age whereas that of shoot roots decreased with increasing age. The range of C.E.C. and A.E.C. values for shoot roots was narrow for the varieties examined. Better differentiation between varieties was obtained when C.E.C. was measured by equilibration of Ca45.Varietal rankings were consistently reproduced in the several experiments when C.E.C., as measured by the three methods, was expressed on a surface area index or total pot bases. The root C.E.C. and A.E.C. values increased with increasing root weight when greater amounts of potassium were applied in both culture media. The root C.E.C. decreased in soil with better physical conditions. The cane varieties grown in solution and soil were markedly different in their growth and nutrient uptake. In the solution culture the growth and uptake were in the decreasing order of HS7-5l74, HS6-5840, HSO-7209 and NCo 310. In the soil the array was HS7-5l74, NCo 310 and HSO-7209. The C.E.C. and A.E.C. were essentially unrelated to the amounts of cations or anions sorbed by the plant, probably because total ion uptake is primarily controlled by diffusion and active absorption rather than exchange. In solution culture the root weight, root surface area index and exchange capacity values/pot were significantly correlated with shoot weight and, except for P and Si, all nutrients analyzed for. The greatest relationships were obtained with root surface area index. In the soil the root weight was significantly correlated with shoot weight and the uptake of N, Mg and S. The root weight, root surface area index and exchange capacity values/pot measured in the solution culture were related to the root weight, shoot weight and ion uptake in the soil. Possibly the measurement of root weight, root surface area index and exchange capacity values/pot by the solution culture method may aid in making a preliminary assessment of varietal differences in nutrient uptake in the field.
Phosphorus-silicon interactions in soils and plants
(University of Hawaii at Manoa, 1969) Roy, Animesh Chandra
Solute dispersion in selected tropical soils
(University of Hawaii at Manoa, 1969) Cagauan, Bernardino Garcia
The dispersion of chloride, nitrate, potassium, calcium, and phosphate was investigated in three tropical soils represented by three Hawaiian soils through a specially designed flow apparatus. Observed differences in the dispersion of these solutes for the range of velocities tested were attributed to differences in ion adsorption capacity and pore geometry. Tritium showed negligible interaction with these soils and was used to trace fluid dispersion. Tritium breakthrough curves differed because of different dead-end porosities of these soils and were estimated to range from 4 to 30 per cent. Potassium, calcium, and phosphate showed trends in their breakthrough curves that were due to dead-end pores. When dead-end pore volume was large, adsorption was relatively small even when the potential for adsorbing ions was great. Because of dead-end porosity a new dimension is added to the interpretation of adsorption data. This in some cases invalidates predicted adsorption based on traditional equilibration techniques. A theoretical model was found adequate to describe the dispersion of tritium, phosphate, chloride, and nitrate under saturated-flow conditions. The unsaturated breakthrough curves of chloride and nitrate also agreed fairly adequately with theory. The unsaturated and saturated breakthrough curves of chloride and nitrate differed because of the added effect of diffusion and restriction of adsorption sites due to stagnant pores in the unsaturated case. A quantity, Ve, which is a volume measured at the arrival of one-half of the initial concentration appears to be a more useful qualitative (as well as quantitative) index of dispersion and adsorption than the dispersion coefficient, D. The experimentally obtained ratio of Ve/Vo can be interpreted to indicate the following: Ve/Vo > 1, dispersion and adsorption; Ve/Vo = 1, dispersion only; Ve/Vo < 1, dispersion in the presence of stagnant or dead-end pores. Vo is the total pore volume. Since Ve is a function of the type of solute, its concentration and pore velocity, and can be estimated by simple inspection of the breakthrough curve, its usefulness becomes more apparent than D. The dispersion approach to the study of silica-phosphate interrelations yielded results which were not in general agreement with adsorption data obtained by non-flowing, batch equilibration techniques. The adsorption of phosphate as shown by breakthrough curves was enhanced by silica treatment in two soils. Less phosphate adsorption (fixation) reported in the literature which have been attributed to silica treatment was not shown to occur in the test soils. This particular finding suggests that the reasons given for crop response to silicate applications to soil need to be reexamined.
Nature and distribution of organic nitrogen in tropical soils
(University of Hawaii at Manoa, 1969) Briones, Angelina Mariano
Distribution of total nitrogen, organic nitrogen forms, and organic matter fractions was studied in -a number of tropical soils. The mineralizable fraction of organic nitrogen and nature of humic and fulvic acids in soils as well as the interaction of these organic matter fractions with soils were also examined. Amounts of total soil nitrogen and its organic forms (hydrolyzable ammonium-N, amino sugar-N, amino acid-N, unidentified hydrolyzable-N, and acid insoluble-N) were markedly influenced by climate. The most striking difference in the amounts of these fractions in various soils was obtained in the acid insoluble-N fraction. Volcanic ash soils developed under high moisture (150 to 250 inches mean annual rainfall) were found to have high nitrogen contents but contained small amounts of acid insoluble-N. In contrast, the acid insoluble-N content of soils occurring under lower rainfall (20 to 40 inches) was considerably higher. Soils derived from crystalline basalt exhibited similar trends. The Lualualei soil developed from alluvium however contained negligible amounts of acid insoluble-N. Changes In the amounts of the organic nitrogen forms after incubation (12 to 18 months) were determined to pinpoint the mineralizable nitrogen fraction. The amounts of hydrolyzable ammonium-N, amino sugar-N, unidentified hydrolyzable-N, and acid insoluble-N slightly increased or decreased with time. Amino acid-N consistently decreased with incubation time. The decrease in amino acid-N was significantly correlated to the increase in mineralized nitrogen content. Distribution of humic and fulvic nitrogen in volcanic ash soils varied markedly with climate. Humic acids predominated in soils developed under low rainfall while fulvic acids were high in soils developed under high rainfall. Basalt-derived soils behaved similarly except for Waialua and Lualualei soils. The Lualualei soil yielded no humic acid and the Waialua soil possessed a low proportion of this fraction. The trend in humic acid distribution followed the distribution pattern of acid insoluble-N. The chemical nature of acid insoluble-N is still unknown. In order to provide more information on the nature of nitrogen in particular fractions of organic matter, the proportions of acid insoluble and hydrolyzable nitrogen in humic acids were determined. It was found that the amount of acid insoluble-N is significantly correlated to the amount of humic acid in soils. Infrared data showed that humic acids of soils developed under high rainfall had lower amounts of aromatic groups than those from soils formed under lower rainfall. Fulvic acids were found to have a more intense absorption band for carboxylic groups than the humic acids. Adsorption of humic and fulvic acids on organic matter-free soils showed that adsorption was strongly concentration and pH dependent. More organic acids were adsorbed in the acid range, and for a given pH adsorption increased exponentially with concentration.
Rates of ecosystem development on some Hawaiian lava flows
(University of Hawaii at Manoa, 1969) Atkinson, I.A.E.
Prediction and comparison of properties of Hawaiian and Indian red earths using automatic data processing techniques
(University of Hawaii at Manoa, 1969) Pandey, Sheo Ji
Physics of drained paddy soils
(University of Hawaii at Manoa, 1969) Briones, Aurelio Aguila
One way in which the tropical world can surpass the temperate regions in food and fiber production is to employ a system of continuous cropping. In tropical Asia for example large areas of paddy land remain idle during the dry season owing to a lack of water and inability of the farmers to obtain adequate soil tilth. When the water resources of these areas are fully developed soil tilth will become a limiting factor for implementing a system continuous cropping. In Southeast Asia alone 27 to 54 million hectares of additional land area can be planted to crops if the problem of water and soil tilth can be solved. This dissertation concerns itself with the problem of regenerating soil structure in paddy soils so that crops other than rice can be grown on these lands. It focuses its attention on the problem of obtaining adequate tilth so that non-paddy crops might be grown as a second, third or even fourth crop on an annual basis. In this study paddy soils are viewed as rheological bodies which behave viscously in the puddled and saturated state, plastically in the moist state and elastically in its driest state. Since this dissertation concerns itself with the physics of drained paddy soils the Hookian or elastic model finds the widest application. Procedures for obtaining elastic constants from sound velocity measurements are described. Physical models are employed to describe shrinking, strengthening and ultimate cracking in drying paddy soils. An attempt is made to explain how and why soil material breaks down into aggregates. Stress-strain relations in drying paddy soils are discussed and the resultant rupture at critical stresses is described by several failure criteria. Lastly, the structural regenerative capacity of a paddy soil is predicted on the basis of a number of soil physical parameters.
Studies on nitrogen transformation and nitrate adsorption in soils
(University of Hawaii at Manoa, 1968) Singh, Budh Ram
Studies on nitrogen transformation and nitrate adsorption were conducted with Hawaiian soils belonging to the Akaka, Wahiawa, Paaloa, Koko, and Lualualei series. There was no definite or conclusive trend of NH4- or NO3-N accumulation with time in the Akaka (virgin), Akaka (cultivated), Wahiawa "A", and Wahiawa "B" soils in situ. However, under laboratory conditions both NH4- and NO3-N were affected. The Akaka (virgin), Akaka (cultivated), and Wahiawa "A", stored In polyethylene bags at room temperature, showed a substantial increase in NO3-N with time but practically no change in NH4-N. In contrast, when two of the above soils [Akaka (virgin) and Wahiawa "A"] were oven dried at 90°C, NH4-N increased with time but N03-N remained unchanged during the entire course of oven drying. Possibly, increased NH4-N resulted from the splitting of ammonium from the proteinaceous parts of organic matter. The Akaka (virgin) and Wahiawa "c" soils were treated with chloride salts. NH4-N mineralization was generally a direct function of salt concentration and length of incubation. Probably NH4-N release resulted from microbial cell breakdown and/or chemical processes. Presumably once the NH4 ions were released from soil organo-inorganic complexes, the subsequent exchange reaction between cations in soil solution and NH4 ions on surface was mainly involved with bringing NH4 ions in the soil solution. A consideration of the overall effect of cations on NH4-N release in the two soils led to the series, Al > Fe> Ca > Mg > K > Na, in order of decreasing NH4 replacing power. However, the series was true only to a concentration of O. 1 M. Beyond this, Al and Fe ions were probably complexed in the soil. The added salts had little or no effect on NO3-N content of the two soils. The Akaka (virgin), Wahiawa "C", Paaloa, Koko, and Lualualei soils were subjected to varying dosages of gamma radiation. The release of NH4-N generally increased with increasing dosages in all soils, while NO3-N decreased in the first three soils, possibly due to certain chemical reactions rendering the loss of nitrate. The rate of NH4-N mineralization in irradiated soils was highest during the first seven days and declined during subsequent incubation periods. Irradiation decreased the recovery of added NH4-N in the Koko and Lualualei soils and N03-N in all soils. In another series three acid soils, Akaka (virgin), Wahiawa "C", and Paaloa, were limed before irradiation. Liming decreased the recovery of added NH4- N and increased the recovery of added NO3-N. Possibly chemical reactions responsible for nitrate loss were inhibited by liming. The adsorption of NO3 was studied with the Akaka (virgin) and Wahiawa "e" soils. Adsorption increased with increasing concentration and decreasing pH of the electrolyte solution. The nitrate adsorption in the two soils followed the Freundlich type of isotherm.
Influence of soil structure on water retention, water movement and thermodynamic properties of adsorbed water
(University of Hawaii at Manoa, 1966) Sharma, Munna Lal
The relationship between soil classes, soil properties, plant growth and soil management treatments in the Goondi Mill area of North Queensland, Australia
(University of Hawaii at Manoa, 1967) Monteith, Nigel Hugh
Most definitions of soil have included references to its function as a medium for plant growth. Several investigators believe that because correlations between soil classes and crop yield are weak, conventional soil surveys are of little value. According to these workers, soil groupings based on "edaphic" trials are more useful for predictions of crop yields. Argument is presented in this dissertation to show that soil properties are most unlikely to correlate directly with crop yield but relationships between soil properties and plant growth responses to management treatments should be feasible. The study reported here sets out to establish the following hypotheses: 1. That each soil class based on a combined morpho1ogica1genetical system of classification has a different group of "key" properties. 2. That each different group of properties has a different influence on plant growth and the response to management techniques. The hypotheses are examined by studying soils growing Sugar Cane (Sacharrum offinarum) in the Goondi area of North Queensland, Australia. The geology and physiography of the area is described. Soils of the area are described, classified, and mapped. The more important soil types are selected for further study and for quantifying those soil properties which are related to the root environment and plant growth. Charge characteristics, charge population, clay mineralogy, and "free" iron oxide content assist in predicting the nature of nutrient pools within soils and the wastage of plant nutrients through chemical reaction or leaching. Atterberg limits are related to water retention characteristics, and soil aggregate strength. Macroporosity and Atterberg limits are related to permeability. The important soils are characterized in terms of these factors. Methods for recognizing the possibility of root impedance, the degree of oxygen shortage for root respiration, and the relationship of root impedance and oxygen shortage to root and plant growth have not been clarified, according to the available literature. Experiments are therefore undertaken to show that macroporosity, bulk density, and soil strength can all be related to root growth but the measurement of soil strength (using a penetrometer with a fine tip) is a satisfactory means of predicting root growth restriction. Several workers have shown that for unsaturated conditions, soil strength is more likely to limit root growth than a shortage of oxygen. If this is so the problem of a shortage of oxygen in soils only occurs under saturated or near-saturated conditions. Preliminary experiments indicated that oxygen in saturating waters was used rapidly although metabolic processes continued to operate. Oxygen may be supplied to the plant roots by transfer from the air through the plant stem. Morphological characteristics of soil profiles can be related to water table fluctuations but water table movement can only be related to plant growth in general terms. It is shown that each group of properties has a different influence on plant growth and soil management and that, by correlation methods, each soil class has a different group of properties. Therefore, each soil class has a different influence on plant growth and the response to management practices.
A genetic study of the gray hydromorphic soils of the Hawaiian Islands
(University of Hawaii at Manoa, 1967) Hussain, Md. Sultan
Aluminum sorption by plants as influenced by calcium and potassium
(University of Hawaii at Manoa, 1967) Gangwar, Mahendra Singh
The uptake of K, Ca and Al by plants was studied in three steps: first, adsorption; second, absorption by excised roots; third, uptake by the intact plants. Cation exchange capacities of the plant roots were as follows: Ananas comosa (pineapple) 7.0, Saccharum officinarum (sugarcane) 9.5 Zea mays (corn) 13.6, and Desmodium canum (kaimi clover) 20.0 m. e. per 100 g. dry roots. Cation adsorption on root surface was observed to be a function of plant species, cation involved and cation concentrations in equilibrating media. The adsorption of Ca and AI on roots of all species increased with increasing cation exchange capacities. However, the adsorption of K was preferential on corn roots. The amount of cations adsorbed increased with their increasing concentrations in equilibrating media. The effects of one cation upon the adsorption of another cation A were reciprocal. At equivalent cation concentration in the saturating solution, cation adsorption by all roots decreased with increasing cation valency. The Al adsorption was influenced by the complementary cation, being higher with Ca than with K. In pineapple and kaimi clover roots, aluminum depressed the sorption of Ca, but stimulated that of K at low concentration. A highly significant correlation was observed between adsorption and absorption of individual cations within each plant species. It is suggested that absorption of a cation is related to its adsorption and amount of appropriate metabolically produced carrier by roots. Pot experiment was conducted to investigate the effect of 5, 20 or 60 percent Ca and 1 or 10 percent K saturations on the dry matter yield and mineral composition of corn and kaimi clover. When the soil pH was allowed to vary from 5.2 to 7.0 depending upon K and Ca applications as hydroxides, K added in excess of 1 percent saturation decreased the yield of both plant species at all levels of Ca. At pH 4.9, corn yield increased by increasing K saturation at 20 or more percentage Ca, but markedly depressed at 5 percent Ca saturation. However, regardless of Ca levels, the yield of kaimi clover decreased with higher K saturation. The amount of cations distribution from the root to the top was shown to depend considerably on the individual ions. More than 80 percent K and Ca absorbed were in the' plant top, but most of Al remained in the roots. Apparently plants differ in their capacity to transfer Al into their aerial portions. The net translocation of Al in kaimi clover was twice than that in corn.
Immobilization and mineralization of nitrogen in Hawaiian soils
(University of Hawaii at Manoa, 1967) Agarwal, Anand Swaroop
Immobilization and mineralization of nitrogen was studied in five Hawaiian soils. Of the two energy sources, a readily available source, sucrose, accelerated and increased the magnitude of immobilization of native as well as added nitrogen more than did the slowly available source, sugarcane bagasse. With no energy source added, the Akaka silty clay, a high organic carbon and high C: N ratio soil immobilized the greatest amount of nitrogen. In acid soils maximum immobilization occurred when lime was added at the highest rate. Liming stimulated carbon dioxide production but calcium chloride had a depressing effect. Calcium chloride either decreased or did not influence the immobilization of nitrogen. Without any treatment the Koko and Paaloa soils, the high total nitrogen-containing soils, manifested maximum mineralization of soil nitrogen. The dominantly amorphous soil, Akaka, although highest in total nitrogen content, showed very low mineralization of nitrogen, presumably because of the existence of a nitrogen-containing inorganic-organic complex. This soil consistently displayed the greatest nitrogen and carbon release upon drying and rewetting, and nitrogen release when limed or treated with calcium chloride and when subjected to gamma irradiation. Significant correlation was found between C: N ratio and nitrogen released during drying and rewetting followed by incubation. In the high release soils, namely the Akaka, Koko and Lualualei, the N: C ratio of mineralized elements increased with the temperature of drying. The radiation significantly reduced the nitrate content in the Paaloa and Wahiawa, the reduction being 23.5 and 16.8 percent for Wahiawa and Paaloa, respectively. Liming increased the mineralization in the Wahiawa, Paaloa and Akaka soils, while calcium chloride effected a greater release only in the Akaka. Increasing osmotic pressures obtained by addition of salts resulted in increased mineralization of soil nitrogen In the Akaka. Different salts on the basis of their effectiveness In bringing about nitrogen release are arranged in the following decreasing order: CaCI2.2H2O > KCl > NaCl > K2SO4 > Na2SO4 > CaSO4.2H2O. Immobilization of nitrogen in sucrose-treated and lime-treated soils was related to corresponding carbon dioxide production values. A chemical release of nitrogen from an inorganic-organic complex in Akaka soil was proposed. The release of nitrogen was shown to be affected by the replacing power of cation, kind of anion and solubility of salt. It was postulated that calcium of Ca(OH)2 may act similarly to calcium from CaCl2.2H2O in effecting nitrogen release. Evidence was presented for the direct effect of heat on the chemical breakdown of organic matter, resulting in the release of some nitrogen. It was speculated that the nitrate loss by irradiation in the Wahiawa and Paaloa soils IS influenced by pH of the soil, and by processes such as denitrification and reduction to ammonium.
Nitrogen fixation by three tropical forage legumes and the utilization of legume-fixed nitrogen by their associated grasses
(University of Hawaii at Manoa, 1966) Whitney, A. S (Arthur Sheldon), 1933
Three tropical legumes, Desmodium intortum, Desmodium canum and Centrosema pubescens, were grown alone and in combination with napier grass (Pennisetum purpureum) and pangola grass (Digitaria decumbens) in fresh volcanic cinders under continuously moist climate on the Island of Hawaii. D. intortum gave high yields of both dry matter (ca. 17,000 pounds per acre) and nitrogen (ca. 300 pounds per acre) in a 12-month period, and transferred small but significant amounts of nitrogen to its associated grasses. D. canum yields were low under these conditions, and the nitrogen yields of grasses associated with this legume were depressed. f. pubescens in pure stand was intermediate in yield of dry matter, but equalled D. intortum in nitrogen yield. However, when combined with grasses, the dry matter and N yields of this legume were reduced by one-half. Transfer of nitrogen to the grasses by C. pubescens was noted only when a 6-month growing period was allowed. The total fixation of nitrogen from the atmosphere during the test period averaged 340 pounds per acre for D. intortum, 82 pounds per acre for D. canum, and 156 pounds per acre for C. pubescens. Of the total nitrogen fixed by D. intortum, 5% or less was transferred to the associated grasses; but with C. pubescens, transfer amounted to 11% of the nitrogen fixed in one instance. Transfer due to the release of nitrogen from roots of these legumes was evaluated by circulating nutrient solution through the root systems of plants growing in cinders in the glasshouse. The roots equilibrated with only trace amounts of solution nitrogen, but marked increases in the levels of ammonium and amino nitrogen occurred immediately after defoliation. When the root systems of nitrogen-starved pangola plants were included in the perfusion systems, significant transfer of nitrogen occurred from the more vigorous legume plants', especially following defoliation. Of the nitrogen mobilized in the legume roots in the 3week period after defoliation, the proportions transferred ranged from slightly over 1% for D. canum to 9% for the more vigorous D. intortum plant. Transfer of nitrogen through the leaching of nitrogen from legume leaves was studied by shaking intact leaves of varying ages in distilled water. The amounts extracted were small, between 0.4% and 0.7% of the total leaf nitrogen. Extractable amino nitrogen tended to be relatively high in rapidly expanding leaves, yellowing leaves, and shaded leaves. Leaf fall accounted for significant nitrogen losses from D. intortum and C. pubescens in situations where leaf senescence equaled the rate of production of new leaves. Under these conditions, the dead leaves from these legumes supplied nitrogen equivalent to over 1.2 pounds per acre per week. This pathway could thus account for appreciable transfer if long growing periods were allowed. The combined action of these three pathways provides an adequate explanation for the nitrogen transfer observed in the field. A number of ways in which transfer by these means would be affected by management and by soil and weather conditions are discussed.
The properties of the black earths of Hawaii
(University of Hawaii at Manoa, 1965) Raymundo, Martin Eusebio
Morphological, physical, chemical, and mineralogical properties of six Black Earth profiles from the island of Oahu, Hawaii were studied. 1he probable source of the dark color was also investigated. The properties of these soils were compared with those of the Black Earths in other countries. The soils were classified by the new V.S.D.A. Comprehensive Soil Classification System. Dark color, heavy clay texture, granular mulch, and slickensides on the surfaces of parallelepipeds were characteristic of most of the profiles. Hence, they are similar to other Black Earths in morphology. The silt contents and bulk density values shown by the profiles were lower than other Black Earths. The clay contents and, subsequently, the moisture retention at saturation, at moisture equivalent, and at 15 atmospheres were higher. The pH values of the Hawaii Black Earths were similar to those from other countries but the ΔpH values were much higher. Calcium and magnesium status was high. Exchangeable calcium was similar in range and magnitude to other Black Earths, but the exchangeable magnesium was In the higher extreme of the range of this particular group of soils. Organic matter levels, exchangeable sodium and potassium, and cation-exchange-capacity values were comparable to other Black Earths. Total SiO2 and total Fe2O3 levels suggested that one of the profiles was perhaps a Black Earth intergrade to Red Earths. Montmorillonitic clay was dominant. Kaolinite and halloysite were also components of the colloidal clay fractions. Feldspars dominated the sand fractions, while magnetite, ilmenite, and hematite occupied the greater bulk of the silt fractions. The magnetic opaque minerals in the silt and sand fractions were perhaps the main contributor to the dark color of the soils. Classification of the soils according to the categories prescribed by the 7th Approximation was not very satisfactory. A modification of the scheme using the same principles was proposed.
Effects of adsorbed cations on the physical properties of soils under arid conditions
(University of Hawaii at Manoa, 1965) Ahmed, Saleem
Arid regions make up a significant percentage of the total land surface of the world. It has been estimated (Dickson, 1957) that of the 57 million square miles of the exposed land surface, about 14 million, i. e., a quarter of the total, receive an annual rainfall of less than 10 inches in any given year. (This excludes the Arctic and Antarctic regions), Broadly speaking, it is this area which has been classified as the "Arid Region of the World" by UNESCO and is shown in Figure 1. Historians trace back the birth of the earliest civilization to arid environment requiring irrigated agriculture. In fact, ancient civilizations could flourish only where irrigation could flourish, and this was possible only along the banks of the big, perennial rivers like the Nile, the Tigris, the Euphrates, the Indus, and the Yang-tze. It has only been during the last 1500 to 2000 years that the scene of greater and greater agricultural activity has gradually shifted to the humid regions. The prime factor contributing to the decline of arid region agriculture has been the development of poor physical condition in the soil caused by the accumulation of soluble salts. This problem has been further aggravated by unwise methods of cultivation which could not be checked because of lack of technical know-how. With the re-emergence of independent nations in the arid regions since the Second World War, greater efforts are being made to study the nature, properties and management practices of the soils of these areas thoroughly. Also contributing to the amount of interest in these soils has been the rapid increase in the population of the world. With the cultivatable lands of the humid regions more or less completely utilized, it is becoming essential to turn to the arid regions to increase food production. The soils of the arid and semi-arid regions are quite different from those of the humid temperate and humid tropic regions. Hilgard (1906) is attributed by Thorne and Peterson (1949) as being the first to recognize and record these differences. Broadly speaking, while the problems of the humid regions are due to excessive leaching, loss of bases, soil acidity and low lime content, those of the arid regions are due to restricted leaching, accumulation of bases, soil alkalinity and high lime content. The soluble salts accumulating most commonly in the arid region soils are the chlorides, sulphates, bicarbonates and carbonates of calcium, magnesium, sodium and potassium. These may be brought up to the surface from a saline water table at shallow depth, or may have been derived from a parent material high in them, or they may be brought in by irrigation water (United States Salinity Laboratory Staff, 1954) and ac cumulate in. those areas where enough "later is not applied to meet the leaching requirement (Wilcox and Resch, 1963). The processes of salt accumulation cause the soil solution to become highly saline. This saline solution is not removed from the soil because of the low precipitation and high evaporation rates, and consequently affects the exchange complex of the soil. Salts may also accumulate in low lying areas due to flooding by saline waters, particularly ocean water. Kelley and Brown (1925) have shown that an equilibrium exists between the cations in the soil solution and those on the exchange complex, and thus the soil will adsorb Ca, Mg, Na and K ions from the soil solution in proportion to its composition and the concentration of the cations therein (Kelley and Cummins, 1921). The physical and chemical properties of the soil are known to be greatly affected by the nature of the cations on the exchange complex. In soils of the arid and semi-arid zones Na is usually the dominant cation, while in the soils of the humid regions, Ca may be the dominant cation. The effects of these cations have been well studied in the literature. The effects of Mg and K have, however, received much less attention. The purpose of this investigation has been to study the effects of the different cations on the physical properties of soils, with special emphasis on the roles of magnesium and potassium. It will be worthwhile to mention that the effects of excess salts have not been investigated--only the effects of the cations, when adsorbed on the exchange complex, have been studied.

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