Studies on the response of ‘Tifblue’ and ‘Woodard’ rabbiteye blueberries to fertilizers

A field study was conducted to investigate the effects of three fertilizer placement methods and 11 fertilizer formulations on plant survival, economics of replanting, yield, and fruit size of two rabbiteye blueberry (Vaccinium ashei Reade) cultivars Tifblue and Woodard. Fertilizer rates were either mixed with the soil under plants (before planting), sidedressed, or half-rate was placed under plants with the other half sidedressed. Fertilizers at planting caused a total of 34% Woodard and 12% Tifblue plants to die as compared to 6% for Woodard and none for Tifblue when no fertilizer was applied. Fertilizer formulas 2-1-1 and 5-10-10 oxide ratios placed under Woodard plants caused 100% mortality whereas Tifblue fertilized with oxide ratios 2-2-2 and 5-10-10 under plants reached the maximum 50% mortality. Splitting fertilizer placement under the side of the plants resulted in less Woodard plant mortality (30%) than placing all the fertilizer under plants (54%). However, plant mortality for the side/under group was not different than sidedressing all fertilizer (23%). A planted hectare in this experiment consisted of 1852 Tifblue and 926 Woodard plants, providing one Woodard plant to pollinate two Tifblue plants. Based on the results obtained, the 5-10-10 fertilizer placed under plants would be expected to cause half the Tifblue (926 plants) and all the Woodard (926 plants) to be replanted. Plant costs alone was estimated to be $2315 with additional replanting costs of $93 for Tifblue and much higher for Woodard. Sidedressing 5-10-10 fertilizer eight weeks after planting would have prevented plant mortality. Placement of various fertilizers under Woodard or Tifblue plants resulted in a significant increase in plant mortality as compared to side placement of fertilizers. Yield loss due to plant mortality increased linearly with the N level of the fertilizers (ranging from 0 to 2) for both cultivars. Woodard fruit size was not affected by fertilizer placement but placing fertilizers under Tifblue plants produced smaller yields with larger fruit than sidedressed plants. Blueberry plants in a virgin acidic soil may experience no reduction in yield if fertilization is completely eliminated.     

Two-variable periodic perturbation of kinetic oscillations

Using one of the generic models (CO oxidation on Pt with surface-oxide formation) predicting kinetic oscillations in heterogeneous catalytic reactions, we show that the efficiency of two-variable periodic perturbations with respect to converting natural period-1 oscillations to period-l oscillations at the forcing frequency is remarkably sensitive to the kind of perturbations used. Counter-phase perturbations are much more effective compared to in-phase perturbations. The physics underlying these findings is suggestive of their applicability to many other models and/or real systems exhibiting kinetic oscillations.     

Effects of partial acidulation on chemical and mineralogical characteristics of residual phosphate rocks

Original phosphate rocks (PR) and water insoluble residues (WIR) from mixtures of reactive PRs and single superphosphate, known commercially as longlife single superphosphate (LLSSP), and from partially acidulated PRs (PAPR), were compared in terms of their elemental content, chemical reactivity as indicated by the apatite unit cell a dimension and solubility. Phosphate rock reactivity is known to be inversely related to the a dimension. Partial acidulation (20%) with commercial grade phosphoric acid resulted in an increase in aluminium (Al), iron (Fe) and fluoride (F) concentrations in the WIRs. The apatite a dimensions of WIRs from LLSSPs were greater than those of the respective original North Carolina (NC), Khouribga (KR), Jordan (JR), Sechura (SE) and Arad (AR) PRs added to single superphosphate (SSP), made from Nauru PR (NR)) to produce the LLSSPs. This was attributed to the presence of the less reactive NR in the WIRs left-over from the SSP. Partial acidulation with phosphoric acid increased the apatite a dimensions of NC and ElHassa (EH) PRs. The increase in apatite a dimension of NC and EH was probably due to selective dissolution of a more reactive fraction of the PRs during partial acidulation. Changes in the apatite a dimension following partial acidulation with phosphoric acid were not significant for the other PRs studied, e.g. Gafsa (GF), KR and AR, although differential X-ray diffractograms (DXRD) indicated that the material dissolved during partial acidulation was more reactive than the WIRs and the original PRs. The apatite a dimension of NC PR was not affected by pretreatment with 2% or 4% citric acid (CTA). The contrasting response in a of NC PR to acidulation with phosphoric and citric acids may be related to differences in the strength of these acids, and/or to the differing environments under which the reactions took place.The 2% CTA and formic acid (FMA) solubilities of the WIRs from LLSSPs and PAPRs were markedly lower than those of the original PRs. This reduction in solubility of PRs following partial acidulation was probably related to changes in mineralogical and chemical composition of the WIRs as indicated by the increases in apatite a dimension of some residual PRs and shifts in peak positions in DXRD, to increases in the concentrations of Fe, Al and F compounds, and to coating effects of PR particles by Fe, Al and F compounds. This, in turn, may reduce the agronomic value of the residual PR component of PAPR and LLSSP fertilizers, particularly over the short-term.The solubility of residual PRs following pretreatment with 2% or 4% CTA was slightly lower than that of the original PRs. The pretreatment caused no significant change in the apatite a dimension of NC PR. The complexing effects of CTA and its lack of Fe and Al impurities may have prevented the formation of Fe, Al and F compounds. The effect of citric acid on PR reactivity is thus quite different from that of the mineral acids used to prepare LLSSPs and PAPRs.     

Studies concerning charged nickel hydroxide electrodes IV. Reversible potentials in LiOH,NaOH, RbOH and CsOH

The variation of reversible potential E_r with log a_moh and has been studied for several nickel hydroxide/oxyhydroxide couples in various alkali hydroxides. Both activated and deactivated -phase couples show only a small dependence ofE _r with log_moh (or where known) in LiOH, NaOH, RbOH and CsOH electrolytes. The change in MOH content on oxidation/reduction is found to be about 0.1 mol MOH per two-electron transfer and is the same as found previously in KOH. These results confirm that the bulk oxidized -phase lattice is devoid of alkali cation although a small quantity may be adsorbed by the surface. On the other hand both activated and deactivated /-phase couples show a marked dependence of 0.45 mol MOH per two-electron transfer in LiOH, NaOH and RbOH (at concentrations > 0.5 m), also in good agreement with earlier data for KOH. On the basis of these results a general stoichiometry can be inferred for the -phase, namely M_0.32NiO₂ · 0.7H₂O where M=Li⁺, Na⁺, K⁺ or Rb⁺. Measurements imply that the Cs⁺ ion or the Rb⁺ ion at low concentration (<0.5 m) do not enter the interlayer structure of the -phase. This behaviour is thought to be related to the low Rb-O and Cs-O bond strengths afforded by the -phase structure.     

Effect of the naturally occurring salt ‘Kanwa’ as a fertilizer on the productivity ofStylosanthes in the subhumid zone of Nigeria

Soil nutrient deficiencies pose a serious limitation to higher crop and forage yields in the Nigerian subhumid zone. Some of the deficiencies may be alleviated by using as a fertilizer a salt mined locally called Kanwa which is traditionally used as a cattle lick. Yields ofStylosanthes hamata cv Verano andS. guianensis cv Cook seed and dry matter increased with Kanwa application at different locations. The effect of Kanwa was enhanced when phosphorus was adequately supplied. Improvements to soil physical properties were proportional to the yield of the legume. The implications of good quality fodder and improved soil conditions in Agro-pastoral Systems in the Nigerian SHZ are discussed.     

Electrochemistry of anodic fluorine gas evolution at carbon electrodes: Part II studies on the ‘CF’ film by the current-interruption,AC impedance,ESCA and auger techniques

The CF films that are formed on the surface of carbon anodes used for the fluorine evolution reaction (FER) in KF·2HF melts at 358 K have been studied by bothin situ electrochemical current-interruption and a.c. impedance methods, and byex situ surface spectroscopy [ESCA (XPS) and Auger] techniques. The surface analysis measurements indicate that a thin CF (CF₂) film, 1.7 nm in thickness is formed on the carbon anodesurface. Results from depth profiling analyses of the film indicate that it is not uniform, higher levels of CF and F components being found towards the carbon anode surface. Thein situ electrochemical measurements demonstrate that an abnormally small interfacial capacitance, (1.6–2.7)×10^–7 F cm^–2, arises in the course of the FER at carbon anodes; this was attributed to the presence of a passive dielectric CF film on the carbon electrodes. The determined interfacial capacitance does not change significantly with potential in the potential range studied, which implies that the thickness of the CF film on the fluorine-evolving carbon anodes may be independent of potential.     

Studies concerning charged nickel hydroxide electrodes I. Measurement of reversible potentials

Reversible potentials (E _R) have been measured for nickel hydroxide/oxyhydroxide couples over a range of KOH concentrations from 0·01–10 M. It is shown that the couples derived from the parent- and-Ni(OH)₂ systems can be distinguished by the relative change in KOH level on oxidation and reduction. In the case of couples derived from the-class of materials a dependence of 0·470 moles of KOH per 2e change is found compared with 0·102 moles of KOH per 2e change for the-class of materials. Couples derived from the- and-Ni(OH)₂ systems can be encountered in a series of activated and de-activated forms having a range of formal potentialsE ₀ . Activated. and de-activated-Ni(OH)₂/-NiOOH couples are found to lie in the range 0·443–0·470 V whilst-Ni(OH)₂/-NiOOH couples lie in the range 0·392–0·440 V w.r.t. Hg/HgO/KOH. It is demonstrated for de-activated,-Ni(OH)₂/-NiOOH couples thatE _R is independent of the degree of oxidation of the nickel cation between states of charge of 25% and 70%. SimilarlyE _R is constant for states of charge between 12% and 60% for activated-Ni(OH)₂/-NiOOH couples. The constant potential regions are considered to be derived from heterogeneous equilibria between pairs of co-existing phases both containing nickel in upper and lower states of oxidation. Differences inE ₀ between the activated and de-activated couples are considered to be related to the degree of order/disorder in the crystal lattice.     

Chemical effects in commercial and laboratory mixtures of ‘reactive’ phosphate rock and acidulated fertilisers

The chemical analyses of different size fractions of a variety of commerical and laboratory prepared samples of partially acidulated phophate rocks and mixtures of reactive phosphate rock and single superphosphate (called LONGLIFE in New Zealand) have been studied. Whereas only minor chemical segregation effects have been observed for partially acidulated products quite a large bias has been established for LONGLIFE materials, and more especially commercial samples, where larger proportions of phosphate rock were found in the lower size fractions. This inhomogeneity was considered to arise from poor mixing of components and subsequent inconsistent granulation; more stringent rejection criteria for undersize material would greatly assist in improving the product quality. Chemical deactivation of the phosphate rock residue in LONGLIFE materials was also observed; this can be partially explained by a selective reaction of the reactive phosphate rock component with acid still present at the time of mixing with the single superphosphate component.     

Available nitrogen in soils and its determination by the ‘Nmin-method’ and by electroultrafiltration (EUF)

Excess nitrogen fertilizer rates are an environmental hazard. To avoid excess rates, the level of available nitrogen in the soil must be known and considered for assessing the nitrogen fertilizer rate. In arable soils nitrate and exchangeable ammonium in the rooting depth of a crop are directly available to plant roots. These two nitrogen forms are recovered with the Nmin method and they are considered in assessing the nitrogen fertilizer rate for arable crops.Besides nitrate and ammonium recovered by the Nmin method from soil samples taken in early spring, a considerable amount of organic soil nitrogen may be mineralized during the growth period and contribute to crop nutrition. The nitrogen mineralization potential can be determined in incubation tests. The absolute quantities of mineralized nitrogen thus obtained, however, are much higher than the mineralization rates under field conditions. It is for this reason that incubation tests have not obtained a major importance for assessing nitrogen fertilizer rates.With the electro-ultrafiltration (EUF) method nitrate, ammonium, and a minor portion of organic soil nitrogen are extracted from a soil suspension. There is experimental evidence that this organic nitrogen (=Norg) is easily mineralizable. Based on field experiments with cereals and maize formulae were established by which the nitrogen fertilizer rate can be calculated. In these formulae nitrate, ammonium and organic nitrogen extracted by EUF are considered.Advantages and drawbacks of the Nmin method and EUF method are discussed.     

Effectiveness of rock phosphate, coastal superphosphate and single superphosphate for pasture on deep sandy soils

The effectiveness of coastal superphosphate and two rock phosphate fertilizers was compared with the effectiveness of single superphosphate for pasture production on deep, humic, sandy podzols in high rainfall (> 800 mm annual average) areas of south-western Australia. The pastures were subterranean clover (Trifolium subterraneum) or mixed subterraneum clover and serradella (Ornithopus compressus). Coastal superphosphate was made by adding rock phosphate and elemental sulphur to superphosphate during manufacture, as it came out of the den before granulation. One rock phosphate was a 50% mixture of apatite rock phosphate from Nauru and Christmas Islands, and which was also used to make the single and coastal superphosphate used in this study, and superphosphate made in Western Australia at the time these experiments started. The other rock phosphate was Calciphos, the fertilizer produced by heating (calcining), at about 500 °C, Christmas Island C-grade ore, a calcium iron aluminium rock phosphate. There were two types of experiments. In the three Type 1 experiments, levels of each fertilizer were applied annually. In the two Type 2 experiments, levels of fertilizer were applied once only to new plots in different years. Coastal superphosphate was the most effective fertilizer in the Type 1 experiments, with both rock phosphates and single superphosphate being equally effective. All fertilizers were equally effective in the Type 2 experiments. There were large variations in fertiliser effectiveness values between yield measurements in the same or different years. It is known that P leaches from freshly-applied superphosphate in these soils. The extent of this leaching probably varies between yield measurements affecting effectiveness values determined for all fertilizers because the effectiveness values were calculated relative to the effectiveness of single superphosphate. The humic, sandy podzols remain wet during the growing season, are acidic, and are known from laboratory studies to possess adequate hydrogen ions to cause extensive dissolution of North Carolina rock phosphate so that rock phosphates are equally or more effective than single superphosphate in these soils. When elemental sulphur in coastal superphosphate is oxidized to SO₄ hydrogen ions are produced which in previous studies has been shown to enhance dissolution of rock phosphate in biosuper, a mixture of rock phosphate and elemental sulphur.     

The relationship between the growth rate of hydrogen bubbles and the duration of the ‘induction period’ in the electrowinning of zinc from sulphate electrolytes

As a result of detailed polarization, volumetric and optical,in situ investigations of the growth rate of hydrogen bubbles during the electrowinning of zinc from Ni²⁺-containing sulphate electrolytes and in the presence of an inhibitor, a relationship has been established between the shape of the hydrogen bubbles and the duration of the induction period. It has been found that during the induction period hydrogen bubbles alter their shape from spherical at the beginning to cupola-shaped at the end, thus increasing by 10–12 times the extent of the screening of the cathode surface beneath. Experimental confirmation is presented for the validity of the previously proposed [1] physical model for the nature of the induction period.     

Phosphorus efficiency of sugarcane varieties in a tropical alfisol

Varietal differences in P absorption and utilization by sugarcane were studied with the objective of selecting phosphorus efficient varieties which can perform well under conditions of low soil phosphorus availability and at low P application rates. Sugarcane varieties differed significantly in dry matter, cane and sugar yields, P-concentration and P-uptake. Based on the cane and sugar yield phosphorus efficiency indices, varieties were classified as P efficient and P-non-efficient. Phosphorus efficient varieties had low P-concentrations and produced higher dry matter per unit P absorbed.     

Preparation on iron of a polypyrrole (PPy) electrode modified with copper by the electrochemical cementation process

Conducting polypyrrole electrodes obtained under galvanostatic electropolymerization on iron from aqueous solutions of pyrrole and oxalic acid were modified with copper particles using the electrochemical cementation process. The electrochemical response of these modified electrodes was compared to that of the unmodified polymer electrode and also to that of bare metallic copper. The modified polypyrrole electrode showed noticeable enhancement for the rate of proton reduction.     

Electrochemical characterization of Fe-Ni-P alloy electrodeposition

In this study we have investigated the electrodeposition of amorphous iron–nickel–phosphorus alloys from a sulfate electrolyte. Fe-Ni alloys are known to exhibit an anomalous type of plating behaviour in which deposition of the less noble metal is favoured. We have found that the codeposition of phosphorus from hypophosphite in the electrolyte led to a reversal to a normal behaviour. This reversal was due both to the suppression of iron and enhancement of nickel partial currents. The overall deposition process is dominated by the hydrogen evolution reaction. This is exacerbated by the low pH needed to codeposit sufficient phosphorus to achieve an amorphous structure.     

The electrochemical quartz crystal microbalance as a sensor in the gold thiosulfate leaching process

A technique was developed for measuring the thiosulfate concentration in gold thiosulfate leaching solutions containing copper and ammonia. The method, which is based on the relationship between thiosulfate concentration and the oxidation rate of silver, was firstly studied using the rotating electrochemical quartz crystal microbalance (REQCM). It was found that the measured silver oxidation rate is directly related to the thiosulfate concentration. The silver oxidation rate was also shown to be unaffected by the presence of other species likely to be found in gold leach solutions. The technique was then evaluated for use as a method of flow injection analysis, utilizing a flow through electrochemical quartz crystal microbalance (EQCM) cell.     

Effect of resistivity on the corrosion mechanism of mild steel in sodium sulfate solutions

Electrochemical impedance spectroscopy (EIS) was used to study the corrosion behavior of mild steel samples immersed in 1, 0.1, 0.01 and 0.001% Na₂SO₄ aqueous solutions at room temperature in order to analyze the corrosion mechanism and obtain representative values of corrosion rates in environments with different resistivity. The EIS technique was used to measure corrosion current densities in 1 to 0.01% Na₂SO₄ solutions, and the measurement corresponding to 0.001% concentration gave a scattered Nyquist plot, whereas in the Bode representation a response associated with solution resistance was obtained. Other electrochemical techniques such as linear polarization resistance, LPR, Tafel extrapolation method and electrochemical noise (EN) were used in order to compare the results obtained by EIS. The charge-transfer resistance (R _ct) parameters obtained in the EIS technique agree well with the corresponding values of polarization resistance (R _p) values obtained by the LPR technique, whereas the electrochemical noise resistance (R _n) parameters obtained by the EN technique gave the highest values for all concentrations. These parameters generally tended to increase as the concentration of the solution decreased.     

Cathodic behaviour of IrO2 electrodes in alkaline solution Part I: Electrochemical surface characterization

IrO₂ electrodes prepared by thermal decomposition of IrCl₃ on a titanium support at temperatures of calcination between 300 and 500°C have been characterized by cyclic voltammetry and potential steps. Standard voltammetric curves have been recorded between –0.65 and 0.35 V vs SCE (prior to H₂ and O₂ evolution) as a fingerprint of the surface state, and the associated charge,q ^*, has been used to monitor the morphology of the active layer. The effect of hydrogen evolution has been investigated by progressively decreasing the negative potential limit, and by increasingly holding the electrode under hydrogen evolution at a constant potential. Phenomena of proton penetration beneath the outer surface into an inner surface have been quantified by potential step experiments. The effect of storing the electrodes in water rather than in the open air has also been investigated. The thermal oxides lose their typical features at calcination temperature < 350° C. Cathodic load does not appear to cause macroscopic modifications of the surface state.This paper is dedicated to Professor Brian E. Conway on the occasion of his 65th birthday, and in recognition of his outstanding contribution to electrochemistry.     

Synthesis and characterization of α-methylstyrene-butadiene-α-methylstyrene linear block copolymers

Summary -methylstyrene-butadiene- -methylstyrene linear block copolymers with a pure block structure were prepared by sec-butyllithium and coupling agent in a four-step process. Their morphology is built up of microdomains of poly- -methylstyrene, including the unbonded segments, dispersed in a polybutadiene matrix. Cylindrical domains arranged in a hexagonal lattice or irregularly shaped domains in a disordered phase are observed, depending on the molecular weight of the poly- -methylstyrene segment.     

Potassium fertilization in relation to plant water potential of wheat

The water potential of wheat plants increased during the mid-day noon, probably as an adaptation; the rise was greater with less frequent irrigation and was increased by KCl application.     

Electrochemical and thermal behaviour of LiNi0.8Co0.2O2 cathode in sealed 18650 Li-ion cells

The electrochemical performance of LiNi_0.8Co_0.2O₂ cathodes in Li ion cells was investigated under static and dynamic load conditions, which prevail in electric and hybrid vehicles using constant current constant voltage and hybrid pulse power characteristic procedures.The thermal properties of this cathode were investigated using the differential scanning calorimetric and accelerated rate calorimetric techniques. The cell fabricated with a LiNi_0.8Co_0.2O₂ cathode showed excellent power performance. The specific energy produced by the 18650 cell was 90 Wh kg^–1 at 100 W kg^–1 power level.