CTAHR Ph.D Dissertations

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Effectiveness of microbial solubilization of phosphate in enhancing plant phosphate uptake in tropical soils and assessment of the mechanisms of solubilization
(University of Hawaii at Manoa, 2008) Osorio, Nelson Walter
A series of experiments were carried out in order to evaluate the effectiveness of a phosphate-solubilizing fungus (PSF), identified as Mortierella sp., to enhance plant phosphate (Pi) uptake and growth. The fungus was isolated from the rhizoplane of Leucaena leucocephala grown in a Hawai'ian Andisol. An in-vitro test was developed to test the capacity of this fungus in dissolving rock phosphate (RP) by means of oxalic acid production in the presence of different types of soil. This PSF could desorb sorbed-Pi from soil mineral surfaces. The presence of high Pi sorbing soil minerals impaired the PSF effectiveness to enhance the supply of soluble Pi. The capacity of the fungus to solubilize P was N-source dependent, being enhanced to a greater extent by ammonium than by nitrate. This PSF was aluminum tolerant and moderately tolerant of low solution pH and its capacity to reduce solution pH and absorb Pi was not affected by these factors. In contrast, Mortierella sp. alone was able to increase plant growth and Pi uptake of mycorrhiza-free leucaena grown in a low Pi-sorbing Mollisol without RP addition. In summary, four major factors can control the effectiveness of PSM to increase soil solution Pi, plant P uptake and growth: soil Pi sorbing capacity, mycorrizal association, calcium phosphate content of soils, and the use of ammonium as nitrogen source.
Release of non-exchangeable potassium in Hawaiian sugar cane soil
(University of Hawaii, Honolulu, 1949) Ayres, Arthur
Effects of incorporating sugarcane trash and pineapple residue on soil and plant characteristics
(University of Hawaii at Manoa, 1977) Asghar, Mohammad
Desorption of adsorbed ametryn and diuron from soils and soil components in relation to rates, mechanisms, and energy of adsorption reactions
(University of Hawaii at Manoa, 1976) Mukhtār, Muḥammad
This study was designed to examine in detail the causes of hysteresis (irreversibility) in the adsorption-desorption process' for two herbicides and its impact under field conditions. An effort was made to relate rate, mechanism and energy of adsorption to this phenomenon. Adsorbents employed in this study were four soils which differed greatly in mineralogy and organic matter content, and two clay minerals, montmorillonite and kaolinite. Adsorption was measured by the batch (slurry) method, supplemented by a flow technique when necessary. Adsorption and desorption equilibrium times for each adsorbate and adsorbent combination were determined and the rate of adsorption was related to hysteresis. Desorption was generally slower than adsorption and both took comparatively longer times in the case of Kaipoioi soil (high in organic matter). Both adsorption and desorption proceeded rapidly during the first few hours and slowed down as the equilibrium time was approached. The faster adsorption equilibrium of ametryn was achieved, the larger was the hysteresis. This kind of relationship was absent in the case of diuron. The magnitude of hysteresis increased with the magnitude of adsorption (as expressed by the Freundlich adsorption constant, Kf) for the various systems. The Freundlich constant, l/n, did not exhibit any correlation with hysteresis. It was, however, observed that the constant increased with temperature and its values were relatively higher in the case of montmorillonite clay and Panoche soil (for which montmorillonite is the dominant clay mineral and organic matter is very low). Adsorption mechanisms appeared" to be related to hysteresis. The hysteresis was larger where ionic attraction was the adsorption mechanism (when ametryn is protonated at low pH) than where mainly physical forces were operative. Diuron exhibited more hysteresis with hydrophobic adsorption (on soils with high organic matter) than with the "water bridge" mechanism (on clay minerals and soils with very low organic matter content). Regardless of adsorption mechanisms, some of the adsorbate molecules were held strongly by the adsorbents, giving rise to hysteresis. Thermodynamic parameters were calculated from equilibrium adsorption measurements and were related to the observed hysteresis. In general, the higher the hysteresis, the larger was, the absolute value of the standard free energy change. The absolute values of standard enthalpy and entropy had a tendency to increase with an increase in magnitude of hysteresis. It can be deduced that the more negative the values of standard free energy change, the greater is the bonding strength, and thus the standard free energy change is related to adsorption mechanism. In the field-watershed portion of this study, the largest diuron concentrations in runoff water were found during the initial storms following herbicide application. After about one year the level of the chemical dropped to a few parts per billion and was almost constant thereafter. The bulk of pesticide was carried by runoff water rather than by suspended soil. The concentration of diuron in runoff was dependent on the concentration of the chemical in the soil. Laboratory adsorption-desorption measurements showed hysteresis in the adsorption-desorption process, which probably attenuated downward movement of the herbicide and contributed to its long persistence in the soil. Recently adsorbed diuron was released to a greater extent than residual diuron. Laboratory measurements assisted in predicting pesticide behavior in the field.
Studies on the biology of sourgrass (Trichachne insularis (L.) Nees) and of its competition with buffelgrass (Cenchrus ciliaris L.) and guineagrass (Panicum maximum Jacq.)
(University of Hawaii at Manoa, 1975) Pyon, Jong Yeong
Sourgrass (Trichachne insularis (L.) Nees) is one of the most serious pasture weeds in Hawaii. It has ruined many good dryland pastures on Maui, Molokai, and Oahu. Studies were conducted on its distribution, seed germination, seedling emergence and growth and development under natural and controlled conditions and on its competition with the improved pasture species, buffelgrass (Cenchrus ciliaris L.) and guineagrass (Panicum maximum Jacq.). Field surveys showed that sourgrass was most abundant below 540 meters elevation, in dry zones of 120 to 760 mm of annual rainfall. Sourgrass occurred on hillsides or on gentle basal slopes where Prosopis pallida (Humb. and Bonpl. ex Willd) HBK. or Leucaena latisiliqua (L.) Gillis and Stearn grew. Distribution of sourgrass corresponded to shade conditions. The soils of infested areas were commonly silt clay to silt clay loam with shallow soil profiles. Low rainfall, high temperatures, and shade were the more important factors in the distribution of sourgrass. Optimum germination of sourgrass seed was obtained under light with alternating temperatures of 20-30 C or 25-35 C or with constant 30 C. Germination in complete darkness was very poor at most temperatures. Germination of sourgrass seed was best under 8 or 12 hour photoperiod but was reduced under 16 and 24 hour photoperiods. Gibberellic acid, kinetin, and thiourea were effective in enhancing germination at 22 C in the dark. Germination percentages of sourgrass, buffelgrass, and guineagrass decreased as moisture stress simulated with mannitol was increased. Guineagrass and buffelgrass were more affected by moisture tension than was sourgrass. The capacity of sourgrass to germinate rapidly under low soil moisture could give it a competitive advantage over buffelgrass and guineagrass under semi-arid to arid conditions. Sourgrass seedling emergence was greatest from seeds planted near the surface and decreased as the depth of planting increased. Sourgrass was capable of emerging from a maximum depth of 5 cm in the clay loam used in this study. Plant height, dry weight, tillers per plant, and seed yield per plant were greatly decreased as the plant density was increased from 5 plants to 160 plants per pot. Intraspecific competition was probably a major factor affecting seedling development and survival of sourgrass. Sourgrass flowering was found to be day-neutral in response to photoperiod. The plants under longer photoperiods flowered earlier than those grown under shorter photoperiods probably because floral development was slow in response to insufficient light energy under shorter photoperiods. Plant height and dry matter production of shoots of sourgrass, buffelgrass, and guineagrass increased but dry weight of roots and tillers per plant decreased with increasing shade. In addition, flowering was delayed as shade increased. Nitrogen fertilization increased plant height, dry weights of shoots and roots, and tillers per plant for all species. A pot study was conducted to evaluate the competitive ability of sourgrass, buffelgrass, and guineagrass under different levels of shade and nitrogen fertilization. The growth of sourgrass was severely suppressed when grown with buffelgrass, guineagrass or both. Highly significant reductions in height, dry weight, and tillers per plant of sourgrass resulted from competition with associated grass species. Sourgrass was thus less competitive than buffe1grass and guineagrass. It is evident from these results that sourgrass in pastures can be controlled through competition from buffelgrass and guineagrass under proper management of grazing and fertilization. Practices which would enhance the competitive advantage of buffe1grass and guineagrass over sourgrass would include the following: (1) ensuring adequate moisture for germination, (2) fertilization, and (3) prevention of over-grazing.
Weed ecology and economic importance of Emilia javanica (Burm.) Rob. and E. sonchifolia (L.) DC
(University of Hawaii at Manoa, 1975) Floresca, Emmanuel T.
The Emilia species and types in Hawaii were studied with respect to their taxonomy and life history, importance as disease reservoirs for the tomato spotted wilt virus, and as a weed competitor with crop plants like lettuce (Lactuca sativa L.), mustard cabbage (Brassica juncea Czern. & Coss.), sweet corn (Zea mays L.) and transplanted tomato (Lycopersicon escu1entum L.). Of the four Emilia species reported in Hawaii, only E. javanica (Burm.) Rob. and E. sonchifolia (L.) DC were found on the islands of Oahu and Kauai, while on Lanai only the Red and Orange types of E. javanica were observed. The E. javanica type Purple was found only in limited areas on Oahu and Kauai. The E. javanica types, particularly the Red type, which were referred to as E. sonchifo1ia or E. sagittata (Vahl) DC by other workers, are the most predominant types on Oahu, Kauai and Lanai. The similarities in vegetative and floral morphology of the different color types of E. javanica, in addition to their ability to interbreed indicate that they belong to the same species. Plant height, capitulum size, number of achenes (seeds) per capitulum, number of capitula per plant were influenced by fertilizer and shading •treatments. The E. javanica types were taller (50 to 62 cm) than E. sonchifolia (19 to 30 cm) at flowering. Fertilized Emilias under 55% shade were tallest while unfertilized plants under full sunlight were shortest. The total length of the capitulum of the E. javanica types ranged from 12.5 to 13 mm compared to E. sonchifolia with 10.5 to 11 rom. When fertilized with N-P-K and grown in full sun-light, the Orange, Red and Purple types of E. javanica had 70, 64 and 57 seeds per capitulum, respectively, while E. sonchifolia had 60. Among the Emilias, the E. javanica type Purple produced the greatest number of capitula per plant. The earliest to mature (seed to seed) was the Purple type of E. javanica (48 ± 2 days), followed by the Red (51 + 1 days), Orange (52 + 1 days), and E. sonchifolia (53 + 3 days) was the latest. Seed germination studies showed that seeds of E. javanica matured earlier than E. sonchifolia. However, viable seeds were formed in both species before the capitula were ready to dehisce. All Emilias examined produced both light and dark colored seeds. The seeds of the Emilia species and types required light for germination up to a period of 4 weeks after harvest. Germination and dormancy varied with seed color, species, and types. Newly harvested seeds of E. sonchifolia germinated better under a wider temperature regime (15 to 35 C) than the E. javanica types (25 to 35 C). Flowering response of the Emilia species and types were day neutral with respect to photoperiod. Observed differences in the time of flowering were due to differential rates of inflorescence development than to differential initiation of the floral primordium. Plants grew taller as the photoperiod was lengthened. Transmission studies by sap inoculation of the tomato spotted wilt virus (TSWV) showed that all the types of ~. javanica (Orange, Red and Purple) and ~. sonchifolia harbored and transmitted the TSWV to tomato 'Tropic' and lettuce 'Anuenue'. The two species of Emilia differed with respect to infection with TSWV. E. sonchifolia gave a lethal reaction while the E. javanica types tolerated infection of the virus. The TSWV from tomato and lettuce were re-transmitted back to the Emilias. Pure stands of E. javanica type Red grown at specific densities with lettuce 'Anuenue', mustard cabbage 'Waianae', sweet corn 'H-68', and transplanted tomato 'N-52' demonstrated that the effects of Emilia on crop growth and yield varied with crop species. For example, full season competition of Emilia at 11 weeds per crop plant decreased the dry weights of lettuce and mustard cabbage by 70 to 30%, respectively. Sweet corn fodder was not affected even with 150 weeds per crop plant, while transplanted tomato fruit yield was reduced 18% by 80 to 126 weeds per crop plant. Because non-limiting irrigation was supplied, differences in response to Emilia competition depended on the crop plant's ability to compete for light and nutrients.
Pore-geometry effects on solute dispersion in aggregated soils and evaluation of a predictive model
(University of Hawaii at Manoa, 1974) Rao, Palakurthi Suresh Chandra
Interactions between phosphate adsorption and cation adsorption by soils and implications for plant nutrition
(University of Hawaii at Manoa, 1974) Stoop, Willem Adriaan
Interactions between phosphate adsorption and cation adsorption were studied in four Hawaiian soils. These belonged to the following soil groups: Hydrandept, Gibbsihumox, Eutrustox and Haplustoll. Relevant ion adsorption mechanisms were investigated by electrochemical techniques and direct adsorption measurements by means of adsorption isotherms. Implications for the availability of P, Ca, Mg and K for plants were investigated in pot experiments. Interactions between phosphate adsorption and cation adsorption were important in highly weathered soils containing mainly variable charge clay minerals such as Fe and Al hydrous oxides. These soils could be characterized by their zero point of charge (ZPC). The ZPC will increase with increasing contents of oxidic colloids. Consequently the adsorption of anions, particularly phosphate, will increase. For the soils in this study ZPC and P adsorption decreased in the following order: Hydrandept > Gibbsihumox > Eutrustox > Haplustoll Calcium was adsorbed specifically by the hydrous oxides present in the highly weathered soils, especially the Hydrandept and Gibbsihumox. The ZPC value of oxidic soils therefore should be determined in CaCl2 solutions to prevent the interference from adsorbed Ca in soil samples. This interference did affect ZPC measurements with NaCl or Na2SO4 as supporting electrolytes since the non-specifically adsorbed Na ion does not compete with Ca adsorbed in the Stern layer. Consequently no ZPC was determined but an isoelectric point (IEP) which refers to the charge o at a distance of several A units away from the colloid surface. A similar problem applied to the extraction of exchangeable Ca by NH40Ac. Non-specifically adsorbed NH4+ ions did not compete effectively with specifically adsorbed Ca, causing incomplete Ca extraction from these soils. With decreasing ZPC values cation adsorption became relatively more important than anion adsorption. Consequently, adsorbed phosphate, which lowered the ZPC, was associated also with increased cation adsorption. The adsorption of 700 ppm P by the Gibbsihumox lowered the ZPC of that soil from 4.10 to 3.85 and increased the cation adsorption by 1.35 me/100g soil at pH 5.5. This amounts to 0.6 me/mmol P adsorbed/ 100g soil. The increase in cation adsorption was more pronounced for specifically adsorbed divalent cations than for non-specifically adsorbed monovalent cations. Because of specific Ca adsorption, applications of NH 4 phosphates had greater effects on the adsorption of other cations (Na, K, NH4 , Mg, Ca) than had Ca phosphates. Hence if all P in these highly weathered soils was applied as Na(or NH4) phosphates, deficiencies of Mg, Ca and certain trace elements could be induced. In addition dispersion of inorganic and organic fractions occurred in the Gibbsihumox. Phosphate solubility in the oxidic soils depended mostly on salt concentration and cation valency. It was decreased by the accompanying cation according to a lyotropic series: K < Mg ≤Ca. This cation effect on P solubility decreased with increasing contents of layer silicate clay minerals and/or increasing base saturation of the soil. Consequently it was almost absent in the Haplustoll, which contains montmorillonite and kaolinite. The cation effect on P solubility has direct practical implications for oxidic soils because it affects P availability to plants at low P application rates, as was demonstrated by pot experiments with the Eutrustox. Increasing Ca concentrations were significantly related to lower P solubility and as a result lower P uptake and lower yields of Sudangrass. Consequently the Ca : P molar ratio in applied fertilizers has implications for P and also cation availability. It was demonstrated that by manipulating the Ca : P ratio one could increase nutrient (P, K and Mg) uptake and yields of Sudangrass and decrease the leaching losses of cations (Na, K, NH4 , Mg, Ca). As a result the efficiency of applied fertilizers can be improved considerably.
Adsorption, denitrification, and movement of applied ammonium and nitrate in Hawaiian soils
(University of Hawaii at Manoa, 1974) Balasubramanian, Vethaiya
The factors influencing adsorption, denitrification. and movement of applied ammonium and nitrate in tropical Hawaiian soils were investigated. Suggestions are incorporated to maximize crop utilization of field-applied fertilizer nitrogen and to minimize loss of mineral nitrogen through leaching and denitrification. Some oxidic tropical soils, such as the Hydrandepts and Gibbsihumox, in Hawaii were found to adsorb nitrate significantly in pH ranges below 6. Non-specific anion adsorption is believed to be the major mechanism by which nitrate was adsorbed. The zero point of change (ZPC), which has a close relation with non-specific anion adsorption, is defined as the pH where the net sum of charges is zero. The high ZPC of the subsoil of the Hydrandepts was attributed to the extensive hydration of their iron and aluminum oxides. Hydrolysis and polymerization of the hydrated oxides were suggested as major mechanisms for the decrease of ZPC and pH on drying the Hydrandepts. Any change in the ZPC was shown to vary the nitrate adsorption. The significant decrease of nitrate adsorption due to dehydration of the Hydrandepts was explained by the change in the ZPC, pH, crystallinity, and surface area on drying. Since this dehydration process is irreversible, it was concluded that these soils should not be allowed to dry excessively by exposure to direct sun and wind so as to preserve their high exchange capacities, both for anions and cations. The surface of the Hydrandepts and Gibbsihumox became less positive or more negative on liming, and this was reflected in the (increased) ammonium and (decreased) nitrate adsorption by the limed soils. The finding that raising of soil pH beyond 5.5 with liming produced N03 repulsion in these soils should be taken into consideration in any liming program. Denitrification loss was found to be important only in soils with large amounts of water-soluble organic matter and nutrients. Available energy source appeared to play a dominant role in denitrification. N2 and N2O gases were the prime denitrification products in all the soils studied. Denitrification potential was very low in Oxisols with poor organic carbon (both water-soluble and total) content. In an infiltration study, it was found that the practically irreversible adsorption of ammonium was responsible for its retention in the Molokai soil. It was further shown that the higher the amount of water infiltrated, the deeper was the position of nitrate peak. An explanation is given on how to take advantage of the lag of nitrate peak with respect to the wetting front in the initially moist soil during transient water flow. For soils with the same initial moisture content, the depth of nitrate peak was in direct proportion to its wetting front. Thus by controlling the wetting front, one can control the depth of maximum solute concentration, irrespective of the rate of water application. In short, modified management practices based on the knowledge of nitrogen transformation and transport in soils as well as nitrogen uptake by crops will ensure efficient (nitrogen) fertilizer use in crop production with a minimum chance for the pollution of ground water by nitrate.
Tillering and ratoon cropping of grain sorghum (Sorghum bicolor (Linn.) Moench)
(University of Hawaii at Manoa, 1973) Escalada, Rodolfo G.
Comparative rheological behavior of suspended clays with varying ionic composition
(University of Hawaii at Manoa, 1973) Dangler, E. W (Edgar W.), 1920
A rheological study was conducted on six clays with the objectives of studying the dependence of viscosity on clay concentration (water content) for important soil mineralogical groups, evaluating the effects on viscosity of chemical treatment induced by changing pH, electrolyte concentration, and composition of the exchange complex, and using interpretation, based on interparticle interactions and predictive model equations to explain observed viscosity differences. The clays were selected to represent 2:1 (montmorillonite and vermiculite), 1:1 (kaolinite and halloysite), and amorphous metal hydroxides and alumino silicate (Akaka and Choyo) structural types. Viscosities of various suspensions were measured by use of a rotational, the MacMichael, viscometer. Supporting experiments were conducted to investigate interparticle configurations by direct electron-microscopic examinations. development of gel structures was monitored by tension measurements in suspension. Results showed that: 1. The order of increasing viscosities for similar concentrations of clay in water was generally as follows: Choyo clay, vermiculite, halloysite, Akaka clay, kaolinite, and montmorillonite. 2. The presence of magnesium on the exchange complex of clays decreased the viscosities of three clay-water systems, namely montmorillonite, kaolinite, and Choyo clay in water. This was attributed to reduction of the extent of the electrical double layer around the clay particles which favored a decrease in number of particles through face-face attraction. The other three, vermiculite, ha11oysite, and Akaka, became more viscous when the exchange surface was saturated with Mg2+. 3. Addition of NaC1 first caused a reduction in viscosity of sodium saturated montmorillonite, vermiculite, and Choyo clay suspensions. This was attributed to hydrolysis and subsequent formation of more flocculated H, A1-c1ays in the absence of electrolyte. Further increases in NaC1 concentration resulted in increased viscosities. In contrast to these three clays, an inverse relationship existed between viscosity and NaC1 concentration for Na-kao1inite and Na-Akaka clay systems. No definite effect of electrolyte concentration was noted on Na-ha11oysite. 4. Addition of MgC12 to Mg-Choyo clays resulted in a viscosity increase that varied directly as the concentration of MgC12• Conversely, viscosities of the five other Mg-c1ays were inversely related to MgC12 concentration. 5. Sodium saturated crystalline clays suspended in dilute NaC1 generally showed viscosity highs at pH 4 and viscosity lows at pH 10. On the other hand, sodium saturated amorphous clays, had viscosity lows at pH 4. Na-Akaka clay had maximum viscosity at pH 7. The viscosity of Na-Choyo showed a continued rise to pH 10. 6. All the Mg-c1ays suspended in dilute MgC12 solutions had their highest viscosity values at pH 10. However, the Mg-kao1inite system had essentially equal viscosities at pH 4, 7, and 10. 7. Measurable tensions of 1-2 cm were detected in very dilute Na-montmori11onite and Na-vermicu1ite systems indicating that interparticle configurations may occur at clay concentrations far below those necessary to form observable rigidity or gel structure. Sodium clay systems that yielded the highest viscosities required the most clay for tension response. 8. Electron micrographs of freeze-dried clay suspensions failed to reveal edge-face or edge-edge interparticle configurations. Evidence was found for face-face positioning of sheets in Na-montmorillonite that had been freeze-dried in NaCl as well as in Na-kaolinite freeze-dried in HCI.
Cation exchange equilibria in irrigated tropical soils
(University of Hawaii at Manoa, 1972) Sinanuwong, Somsri
Gene action in the inheritance of agronomic traits in intervarietal diallel crosses and relative importance of gene effects for quantitative characters in Zea mays L
(University of Hawaii at Manoa, 1972) Shin, Han Poong
An investigation was undertaken to determine gene action in the inheritance of agronomic traits in a diallel set of eight inbred lines of sweet corn and all possible Fl hybrids, including parents. Data were analyzed by Jinks and Hayman's diallel analysis for plant and ear height, weight with and without husk, shank and ear length, ear and cob diameter, kernel depth, and mid-silking days. Additive effects and environmental variations were significantly different from zero for April, June, and Combined dates of planting. Estimates of the component of variation due to dominance effects were significantly different from zero except for shank length and cob diameter in June and ear length in April planting. The parents carried an excess of dominant genes for plant height, ear length, weight with and without husk, mid-silking days, and an excess of recessive genes for shank length. Dominant and recessive alleles of each gene were distributed nearly equal among the parents for ear diameter, cob diameter, and kernel depth. Ear length, shank length, cob diameter, and mid-silking days for the June planting and ear height in Combined dates of planting were within the partial dominance range. Heritability estimates supported the conclusion that selection for weight with and without husk, mid-silking days, and ear height would be most effective and that selection for ear diameter, plant height, ear length, shank length, and kernel depth would be least effective. Eight inbred lines of sweet corn, including parents, Fl's, F2's, and first backcrosses were tested at two locations in one year. The population means obtained were used to estimate additive, dominance, additive x additive, additive x dominance, and dominance x dominance gene effects for nine quantitative agronomic traits. Additive gene effects appeared to be the most constant over locations for plant and ear height. Dominance gene effects for weight with and without husk, and ear length were more important than those of additive effects. The remaining types of gene effects indicated very little stability over locations for most of the agronomic traits studied. The relative magnitude of expected genetic gain expressed as a percentage F2 mean would suggest that rapid progress should be accomplished by selecting and recombining in early generations for plant height in the crosses AA 11 x AA 18 and AA 8 x 190a. Slower progress should be expected from crosses AA 18 x 190a, AA 11 x 245, AA 2 x AA 11, and AA 20 x P 39. For ear height, rapid progress should be expected from crosses AA 18 x AA 20, AA 11 x AA 18, AA 8 x 190a, and AA 2 x AA 11. For weight with husk, good progress should be expected from crosses AA 11 x AA 18, AA 11 x 245, AA 8 x 190a, AA 2 x AA 11, and AA 20 x P 39. For ear length, rapid progress should be expected from crosses AA 18 x 190a, AA 11 x AA 18, and AA 20 x P 39. For the nine crosses considered, it was concluded that most of the variation was due to additive and dominance gene effects with epistasis being some importance.
Seed pelleting as an approach to herbicide selectivity in directseeded rice
(University of Hawaii at Manoa, 1972) Nangju, Dimyati
Fate of ametryne in soil, nutrient solution-sugarcane and soil-sugarcane systems
(University of Hawaii at Manoa, 1972) Goswami, Kishore Puri
Ametryne (2-methylthio-4-ethylamino-6-isopropylamino-~-triazine) is used in sugarcane, pineapple and banana cultivation for weed control mainly in the tropics, and very little has been published concerning its fate in soil and sugarcane. This investigation was carried out utilizing ring-14C ametryne to determine its degradation and metabolism and to develop a 14C-balance account for each experiment. A simple procedure was developed for the simultaneous extraction of ametryne, atrazine and hydroxyatrazine (HA) in acidified methanol from soil by shaking, and quantitative separation of HA by liquid-liquid partitioning. Quantitative extraction was achieved when the pH of soil extract (soil/solvent = 1/10) was between 2.0 and 2.5, without causing hydrolysis of the two parent triazines to HA during the extraction. HA was quantitatively partitioned in the aqueous phase by first treating the soil-extract with 0.25N HCl (HC1/extract = 0.25), mixing with water (water/extract = 1) and then chloroform (chloroform/extract = 5). Degradation and metabolism of ring_14c ametryne. ring-14C HA and ethyl-14C HA were determined for 30 days in a nutrient solution-sugarcane system. Sugarcane roots rapidly converted ametryne to more polar compounds (90% at 30 days); the major degradation products were dealkylated ametryne (32.9%) at 20 days and 2-methylthio-4,6-diamino-~triazine (12.5%), and ammeline (34.4%) at 30 days. Metabolism of ring14C ametryne, ring_14c HA and ethyl-14C HA to 14CO2 by sugarcane was confirmed for the first time; of the absorbed 14c, 1.7%, >8.0% and >23.0% 14CO2 were evolved respectively from ping_14C ametryne, ring_14C HA and ethyl-14C HA treated plants. In the same study a volatile 14C metabolite (1.9% of applied 14C) was discovered for the first time in the condensed transpired water from ametryne treated sugarcane; it was not 14CO2 but a basic, water soluble compound. No 14Cwas found in the transpired water from HA treated plants. Ametryne and HA were degraded through different mechanisms in sugarcane. Ametryne was not degraded to HA by sugarcane, but cane was able to metabolize HA faster than ametryne. Proposed degradation pathways for HA and ametryne have been presented. Degradation of ametryne-14C in sterilized and non-sterilized soils was measured for 60 days. In non-sterilized Hilo and Molokai soils, 36 and 25% ametryne was converted to polar-products against 4.2 and 4.9% in the sterilized soils respectively; evolved 14CO2 was 0.19 and 0.08% respectively in non-sterilized soils. The concentration of the polar-products, and not of ametryne, was the rate-limiting step for 14CO2 evolution. Assimilated-14C was 19 and 9% respectively in non-sterilized Hilo and Molokai soils, and 0.1% in sterilized soils. Ametryne degradation in a Molokai soil-sugarcane system was determined for 60 days with soil-root and shoot components enclosed separately. The respective percent 14C-constituents measured at 60 days in soil-root and bare soil were: polar-products, 84.1 and 19.5; 14C02 evolved, 4.04 and 0.08; and biomass, 19.4 and 1.4. The shoot evolved only 0.03% 14CO2. Nearly 5% of the absorbed-14C was volatilized from the shoot and measured in the condensed transpired water. Ametryne was degraded both through N-dealkylation and 2-hydroxylation in soil. The major discoveries were: (1) Sugarcane plants metabolized ring-14C ametryne, ring-14c HA and ethyl-14C HA to 14CO2. (2) A volatile 14C-metabolite was present in the condensed transpired water from ametryne treated plants but not from HA treated plants. (3) Ametryne and HA were degraded by sugarcane through different mechanisms. (4) Ametryne degradation in bare soil was mainly (N-dealkylation) a microbial process with limited simultaneous chemical hydrolysis. (5) Sugarcane roots accelerated ametryne degradation (N-dealkylation) by several fold in nutrient solution and in soil (2-hydroxylation). (6) Simultaneous extraction of HA and parent triazines from soil in acidic-methanol and partitioning of HA in chloroform with added water was quantitative.
Analysis and prediction of the properties of Western Samoa soils
(University of Hawaii at Manoa, 1970) Schroth, Charles Lorenz
Degradation of atrazine and related triazines in Hawaiian soils
(University of Hawaii at Manoa, 1970) Obien, S. R (Santiago Rigonan)
Effect of pH, silicon and phosphorus treatments on growth and yield of papaya (Carica papaya L.)
(University of Hawaii at Manoa, 1969) Adlan, Hassan Ali
Field and laboratory experiments to evaluate pH, silicon and phosphorus effects on papaya were conducted on the island of Kauai on an aluminous ferruginous latosol. The main plots were soil pH (5, 6 and 7) attained by liming, subplots were Si levels 0, 833 and 1166 kg per ha and three P levels, 0, 560 and 1120 kg per ha were superimposed on the Si subplots in a 3x3x3 factorial with three replications. With addition of P there was a highly significant (P=0.01) increase in plant height with age. Growth was suppressed in zero-P treatments, culminating in death of the plants. Silicon treatment produced a very limited growth response. At pH 7 plant growth increased significantly (P=0.05) . In general growth was highly influenced by the relative sufficiencies of lime and P. Although analysis of variance indicated no significant effect due to Si application, multiple regression equations revealed a positive effect of Si at later stages of growth. Papaya fruit yields, both total and total marketable, increased significantly (P=0.01) with P treatment, and with pH levels (P=0.01). A trend for increased yield with Si treatment was not statistically significant. Monthly yield increased under all levels of treatment. Trees in the zero-P treatment produced almost no fruit. Fruit quality, as determined by pH of fruit juice, titrateable acidity, Brix percentage and Brix-acid ratio, did not differ with treatment. A Brix percentage of 11.5 is tentatively suggested as a measure of fruit maturity in papaya. Plant and soil analyses related closely to growth effects. With increased P, P concentrations increased in petioles and blades. In zero-P treatments, P concentrations remained almost constant throughout the soil pH range. Intermediate levels of Si increased plant P, but these values decreased with highest Si application. Multiple regression equations revealed a close relationship between P, Si and Ca in the plant. The petiole was more sensitive to Si treatment than the blade. Silicon concentrations in both petioles and blades increased with increasing pH and P applied. Whole plant samples at flowering indicated similar patterns of nutrient accumulation in the stem and petiole. Phosphorus, Si and Ca increased in all tissues with increasing treatments. Dry weight of whole plants increased with increased treatment levels. Increasing P caused a marked decrease in the number of days to flowering. Total nutrient uptake at flowering by the papaya was calculated in kg per ha. Nutrient uptake increased with increasing treatment and with higher pH. Calcium increased in both blades and petioles with age. Generally Ca was higher in the blade than the petiole. There was a trend of increased Ca concentration with increased P applied especially at high pH. Leaf Ca also increased with increasing pH. Exchangeable soil Ca values increased with higher pH. Extractable soil Si increased with Si treatment; within one Si treatment extractable soil Si increased with higher P applied. Silicon increased from pH 5 to pH 6 and then decreased from pH 6 to pH 7. In zero-P treatments soil Si remained constant throughout the whole range of sampling intervals. There was a tendency for extractable Si to decrease with time. Silicon application did not affect the native soil P, but with increasing P treatment, Si seemed to cause an increase in extractable soil P. A relationship was established between incidence of Phytophthora parasitica blight of papaya and pH 6, in that maximum spread of the blight occurred at pH 6.
Effects of different levels of N, P and K fertilization on the growth and yield of upland and lowland taro (Colocasia esculenta (L.) Schott, var. Lehua)
(University of Hawaii at Manoa, 1967) De la Pena, Ramon S (Ramon Serrano), 1936
Nitrogen, phosphorus and potassium were applied separately from 0 to 1120 kg/ha to upland and lowland taro. A 2 x 2 x 2 N-P-K interaction experiment was also conducted in pots using 0 and 15 grams of each element per plant. Nitrogen fertilization increased the N contents of the taro leaves but decreased both the P and K contents. Applications of P fertilizer increased the P content in the leaves but decreased the K content. Potassium fertilization increased K and decreased Ca and Mg contents of the taro leaves. The N content of upland taro leaves increased with K fertilization but the N content of the lowland taro leaves decreased. Potassium in the leaves of lowland taro regardless of treatments was lower than the K content of upland taro due to the higher Ca and Mg contents of the lowland soil. Both upland and lowland taro plants exhibited luxurious P and K consumptions. The N, P, and K contents of the leaves, regardless of treatments, decreased with age ..• The total N content of the soils was negatively related to the N fertilization, while soluble P and exchangeable K were directly related to the rates of P and K fertilizers applied. Yields of both upland and lowland taro were significantly increased by N and P fertilization. Potassium fertilization increased the yields of upland taro only. Delayed harvesting up to 15 months increased the yields of lowland taro, while yields of the upland taro at 12 to 15 months old did not differ significantly. In the lowland taro, the significant yield increase due to fertilization was attributed to the increase in number and weight of the sucker corms. In the upland taro, however, yield differences among fertilized plots were attributed to the main corms. Nitrogen fertilization decreased the density of both upland and lowland taro corms significantly. Phosphorus fertilization did not have significant effects on the corm density. Potassium fertilization increased the corm density, especially in the lowland. Protein content of the corms of upland and lowland taro which were fertilized with N increased by 53.5% over the control. In the pot experiments, the increase in protein content was 250%. The P and K contents of the corms also increased with P and K fertilization. In the pot experiment, only N fertilization gave significant increases in the weights of the corms, roots and leaves of the plants. Nitrogen deficiency was observed in all plants which did not receive N fertilization. Analysis of the leaves showed that plants which received N had an average of 2.8% and 4.6% N in the petioles and blades, respectively, compared with 1.1% and 3.3% N in the petioles and blades of plants without N fertilization. No P and K deficiencies were observed. The N, P, and K contents of the individual leaves showed a tendency to decrease from the youngest leaf to the oldest, except for P which increased from the youngest to the oldest when the P supply was not limiting. Results of the experiments showed that soil and plant analysis can be used to evaluate the fertilizer requirements of taro. In soil analysis, however, other methods of extracting soil N should be used to give a reliable index for the N requirement of taro.
Kinetics of adsorption/desorption of nitrate and phosphate at the mineral/water interfaces by system identification approach
(University of Hawaii at Manoa, 2004) Shuai, Xiufu

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