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1.
The response of two okra (Abelmoschus esculentus L. Moench) varieties (White velvet and NHAE 47-4) to fertilization in northern Nigeria was examined using four rates of nitrogen (0, 25, 50 and 100 kg ha–1) and three rates of phosphorus (0, 13 and 26 kg ha–1). Nitrogen application significantly increased green pod yield, pod diameter, number of fruits per plant, number of seeds per pod and pod weight. Application of phosphorus also significantly increased green pod yield, pod number and number of seeds per pod. The two varieties responded to nitrogen application differentially with respect to green pod yield. For optimum green pod yield of White velvet 35 kg N ha–1 is suggested while for variety NHAE 47-4, N fertilization can be increased to 70 kg ha–1. There was no differential response of varieties to phosphorus fertilization for green pod yield; however, the application of 13 kg ha–1 enhanced the performance of both varieties.  相似文献   

2.
Nitrogen (N) management in the ‘De Marke’ dairy farming system   总被引:2,自引:0,他引:2  
In the sandy regions of The Netherlands, high losses of N from intensified dairy farms are threatening the environment. Therefore, government defined decreasing maximum levy-free N surplusses for the period 1998–2008. On most dairy farms, the current N surplus has to be reduced by half at least. Farmers fear that realizing these surplusses will be expensive, because it limits application of animal manure, which then has to be exported or additional land has to be bought. Moreover, farmers are worried about the impact on soil fertility. To explore the possibilities for reducing surplusses of average intensive farms by improved nutrient management, farming systems research is carried out at prototype farm De Marke. Results are compared with results of a commercial farm in the mid-1980s, the moment that systems research started and introduction of the milk quota system put a halt to further intensification. Results indicate that average intensive farms can realise a reduction in N surplus to a level below the defined final maximum, without the need to buy land or to export slurry. Inputs of N in purchased feeds and fertilisers decreased by 56 and 78%, respectively. Important factors are reduced feed intake per unit milk, as a result of a higher milk yield per cow, less young stock and judicious feeding, an improved utilization of home-made manure and a considered balance between the grassland and maize area. Changed soil fertility status did not constrain crop production. Nitrate concentration in the upper groundwater decreased from 200 to 50 mg l-1, within a few years.  相似文献   

3.
Fluorine-evolving carbon anodes exhibit unusually high overvoltages characterized also by remarkably large Tafel slopes having values 0.4–0.8 V per decade of current density change. Also, at high current densities, a so-called anode effect associated with a type of passivation sets in. Experiments are described which aim to distinguish high polarization arising from an intrinsically large Tafel slope, generated by a non-ohmic charge transfer barrier layer effect due to CF film formation, from effects due to difficulties of F2 bubble detechment and F2 gas film formation at the CF film. Steady state polarization measurements have been made at a rotating carbon cone electrode from which F2 bubbles, which otherwise remain attached to the electrode and block access to the electrolyte, can be spun away. At the rotated electrode, at low and intermediate current densities, linear Tafel behaviour is still observed but with high slopes associated with the barrier layer film effect. At higher current densities an anode effect, associated with the F2 gas film, is developed, leading to a type of passivation of the electrode. The two sources of unusually high polarization in the F2 evolution reaction at carbon are not independent as it is also the formation of the CF film that causes difficulties in gas bubble detachment owing to the lyophobic properties of the fluorinated C/F2/KF·2HF interface. Polishing effects confirm this conclusion.  相似文献   

4.
A new continuous process combining electrochemical reaction and chromatographic simulated-moving-bed (SMB) separation is presented. To demonstrate the potential of process integration, this reactor concept is applied to the direct electrochemical production of arabinose by means of simulation. Experimentally verified models of reactor and column units are combined with a model of the electrochemical SMB-reactor. These process units are characterized individually and their model parameters are discussed. The electrochemical reaction inside the microreactor can be described by a series reaction, which has an impact on the design of the integrated process: as the reaction should take place in areas of the SMB-process with maximum educt concentration, the reactors are switched on and off during operation. The integrated process shows interaction between the reaction and the separation to diminish side reactions. Case studies prove the theoretical feasibility of the integrated process. Compared to a conventional process with a reactor followed by a SMB-separation, higher yields can be obtained.  相似文献   

5.
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.  相似文献   

6.
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.  相似文献   

7.
Strontium ferrates and cobaltates with compositions SrFeO3- (0.060.40) and SrCoO3- (0.040.30) were synthesized. The dependence of the oxygen electrode properties on the value was examined in 1 mol dm–3 KOH solution. In the SrFeO3- series, the samples with 0.24<<0.29, showed the highest activity in both oxygen evolution and reduction reactions. In contrast, no strong dependence on the value was observed in SrCoO3-, which also showed a high catalytic activity for oxygen evolution.  相似文献   

8.
Summary The interaction of -cyclodextrin(-CD) with sodium 1-pyrenesulfonate(PS) was studied spectrophotometrically. -CD was found to cause much larger decrease in the absorption maxima of PS than -CD. The fluorescence spectra of PS in the presence of -CD showed excimer emission, while those of PS with -CD showed only monomer emission, indicating that -CD forms 12 (-CDPS) complexes in which two PS molecules are included in the -CD cavity in a face-to-face fashion. The binding isotherm showed a sigmoidal curve. The association constants were estimated by computer simulation of the binding curve. The 12 (CDPS) complex was found to be much more stable (K=106 M–1) than the 11 complex (K=1 M–1). At high concentration of -CD another -CD cooperates in binding two PS molecules, resulting in the formation of a 22 complex.  相似文献   

9.
Summary Hot drawing at 150°C has been applied to high molecular weight polyethylene fibers produced by flow induced crystallization in a Couette apparatus, referred to as the surface growth technique. A distinct improvement of the tensile properties of the fibers was noticed upon drawing. A tensile strength at break of 4.7 GPa was reached. Drawability is discussed in relation to fiber morphology. The shish-kebab like structure of the surface growth fiber was transformed into a morphology consisting of smooth fibrils upon drawing.  相似文献   

10.
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.  相似文献   

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