Low Nitrogen Doses Research Articles

Linking the effects of nursery light and fertilization and post-transplant first summer irrigation on the field survival and growth of Pinus pinaster seedlings

Seedling size-related functional attributes of Mediterranean forest species are critical traits to be considered in nursery practices aimed at improving the survival and performance of seedlings exposed to summer drought in dryland reforestation projects. We looked at how nursery light regimes and nitrogen fertilization affected the survival and performance of Pinus pinaster Ait. under contrasting post-planting watering regimes. Seedlings grown in the nursery for 13 months were given low or high nitrogen doses and exposed to three light regimes (full sun, medium light and low light). After outplanting, half of the seedlings were watered fortnightly during the hottest months of the first summer and the other half were left unwatered. Seedling size-related variables (shoot height, basal diameter, stem volume and sturdiness quotient) were measured at the beginning and at the end of the study, and summer drought survival was checked three times. Our results showed that fertilization and the nursery light regime influenced initial seedling quality and transplant stress. Post-planting first summer watering also increased seedling survival probability. The medium-light and especially the full-sunlight regimes in the nursery decreased the probability of seedling mortality after outplanting. However, a low-light regime in the nursery negatively affected plant traits and increased the probability of post-planting seedling mortality. In comparison with low-N seedlings, high-N fertilization increased post-planting stress (evaluated in the change of sturdiness quotient after one field growth season), but did not affect survival.

Growth, Productivity, and Essential Oil Content of Fennel Plants Treated with Spirulina Platensis Extract and Compost Tea Under Low Nitrogen Doses

The aim of this study was to find alternatives (even partial) to mineral nitrogen fertilization to reduce its harmful accumulation in the edible parts of fennel. Fennel (Foeniculum vulgare) is a perennial plant of the Apiaceae family grown for its edible shoots, leaves, and seeds. The present work was conducted in two successive seasons, in 2018/2019 and 2019/2020, at the farm of the Agricultural Botany Department, Faculty of Agriculture, Ain Shams University, Cairo, Egypt, to investigate the efficiency of application of two biostimulants—Spirulina platensis algae extract (SP) at 10% and compost tea (CT) at 6.72 ml L−1—with partial doses (75 and 50%) of the recommended mineral nitrogen fertilizer dose on growth, photosynthetic pigments, fruit yield, and essential oil productivity. The results indicated that vegetative parameters, leaf number, branch number, shoot and bulb fresh weight, and shoot dry weight, as well as yield components such as 100-fruit weight and number of umbels per plant were significantly enhanced with application of SP as a foliar spray coupled with 75% of the recommended dose of nitrogen fertilizer (SP + 75% N) as compared to other treatments. Photosynthetic pigments and total soluble carbohydrate were improved significantly when CT was applied as soil drenching coupled with 75% of the recommended N dose (CT + 75% N). In this regard, a clear effect was noticed in terms of oil yield and fruit yield using SP and CT with a 75% N dose. It is concluded that using Spirulina platensis algae extract and compost tea as biostimulants coupled with only 75% of the recommended nitrogen fertilizer dose can be recommended for economical fennel production.

Effect of Nitrogen and Elixr on Soybean (Glaycine Max) Attributes, in New Halfa Agriculture Scheme

To find out the effect of nitrogen and elixr on soybean attributes, this experiment is set up in (RCBD), with four replications. The treatments are zero fertilizer (Z0), two doses of both nitrogen (N1=50; N2 =100 Kg fed-1) and elxir (E1=10; E2=20 L fed-1). The findings show that the treatments have no effect on the plant height, number of branches and days to reach 50% flowering, however the number of leaves increased significantly with increasing nitrogen (N2) and declined with increasing of elixr (E2). The lower nitrogen dose (N1) enhnce plant fresh and dry weight, however treatments of elixr (E1; E2) deteriorated both weights. Number of pod per plant, seeds per pod and seed weight have a liner increase with increasing nitrogen (N1; N2), followed by the higher dose of elxir (E2), however the low dose of elxir (E1) record the minimum. The yield per plant and hectare are a greatest with lower (N1) and higher (N2) dose of nitrogen respectively, followed by control (Z0), however yield attributes fail with applying elxir.

Mineral Fertilization and Maize Cultivation as Factors Which Determine the Content of Trace Elements in Soil

This study has been carried out in order to determine the effect of increasingly intensive fertilization with potassium, applied in combination with nitrogen, on the content of trace elements in soil after the harvest of maize (Zea mays L.). The soil content of trace elements depended on the fertilization with potassium and nitrogen. Potassium fertilization had a stronger effect on the content of trace elements in the pots fertilized with the lower nitrogen dose (130 mg N kg−1 of soil). The increasing doses of potassium led to a higher soil content of zinc (Zn), and especially of nickel (Ni). The impact of potassium fertilization on the content of the remaining trace elements in the soil was less unambiguous, and depended on the dose of potassium and nitrogen fertilization. Nitrogen fertilization resulted in a higher soil content of manganese (Mn), chromium (Cr), nickel (Ni) and cadmium (Cd), as well as a decreased soil content of lead (Pb). It needs to be underlined that changes in the soil content of Ni, Cd, and Pb, effected by nitrogen fertilization, were larger than in the cases of the other trace elements. The influence of potassium and nitrogen fertilization did not result in exceeding the current threshold amounts of trace elements set for agriculturally used soil. An increase in the contents of some trace elements in soil is beneficial from an agricultural point of view. Some of these elements are necessary for the correct growth and development of arable plants.

Role of antioxidant pool in management of ozone stress through soil nitrogen amendments in two cultivars of a tropical legume.

The present experiment was done on two different cultivars of a tropical legume, Cymopsis tetragonoloba L. Taub. (cluster bean) cvv. Pusa-Naubahar (PUSA-N) and Selection-151 (S-151). The experiment was conducted under ambient ozone (O3) conditions with inputs of three different doses of inorganic nitrogen (N1, recommended; N2, 1.5-times recommended and N3, 2-times recommended) as well as control plants. The objective of this study was to evaluate the effectiveness of soil nitrogen amendments in management of ambient ozone stress in the two cultivars of C. tetragonoloba. Our experiment showed that nitrogen amendments can be an efficient measure to manage O3 injury in plants. Stimulation of antioxidant enzyme activities under nitrogen amendments is an important feature of plants that help plants cope with ambient O3 stress. Nitrogen amendments strengthened the antioxidant machinery in a more effective way in the tolerant cultivar PUSA-N, while in the sensitive cultivar S-151, avoidance strategy marked by more reduction in stomatal conductance was more prominent. Enzymes of the Halliwell-Asada pathway, especially ascorbate peroxidase and glutathione reductase, were more responsive and synchronised in PUSA-N than S-151, under similar nitrogen amendment regimes and were responsible for the differential sensitivities of the two cultivars of C. tetragonoloba. The present study shows that 1.5-times recommended dose of soil nitrogen amendments was sufficient in partial mitigation of O3 injury and the higher nitrogen dose (2-times recommended, in our case), did not provide any extra advantage to the plant's metabolism compared with plants treated with the lower nitrogen dose (1.5-times recommended).

Evaluation on morpho-physiological characters of synthetic maize genotypes on low soil nitrogen level condition

A study aimed to evaluate the growth and production of several synthetic maize lines at low nitrogen level was conducted at the Indonesian Cereals Research Institute Experimental Farm in Bajeng District, Gowa Regency, South Sulawesi. The research was carried out from September to December 2018. The study also aimed to determine the nitrogen dose that could be used for selection of synthetic maize genotypes against low nitrogen doses. The study was conducted in the form of an experiment using a Split Plot Design. Five levels of Nitrogen fertilizer were used namely 0, 50, 100, 150, and 200 kg N per hectare. Various genotypes treatment were consisted of 4 synthetic maize genotypes namely Syn 5, Syn 6, Syn 7, Syn 8 and 2 comparative varieties namely Bisma and Lamuru. The results show a significant interaction between the treatment of nitrogen doses and the synthetic maize genotype on the morphological and physiological characters of the maize genotypes. Genotypes gave the best results at nitrogen doses of 100 kg N ha−1 was Syn8 (8.67 tons ha−1) and 50 kg N ha−1 (6.47 tons ha−1). Nitrogen doses of 50 kg N ha−1 and 100 kg N ha−1 can be used for the selection of maize tolerant to low nitrogen condition with productivity of 4.57 tons ha−1 and 8.67 tons ha−1, respectively. There is potential for the Syn8 genotype to be developed for low-nitrogen-tolerant maize varieties due to higher production compared to the comparative variety.

Deep Placement of Briquette Urea Increases Agronomic and Economic Efficiency of Maize in Sandy Loam Soil

Imbalanced use of fertilizers along with inappropriate sources and application methods has attributed to reduced nitrogen use efficiency (NUE) and crop productivity. The use of the right N source and appropriate application method is essential to reduce N losses and increase NUE, crop yield, and economic return. A field trial was conducted at the Agricultural Research Station, Dasharathpur, Surkhet following a randomized complete block design with seven treatments (three replications) using various N sources (urea, urea briquette, and three different blended fertilizers) and their application methods to assess their fertilizing efficiencies. Treatments showed a significant effect (p<0.05) for all the traits viz. plant and ear height, stover and grain yield, harvest index, and thousand-grain weight. Compared to the recommended dose of fertilizer (RDF), the grain yield advantage of blended fertilizer (10:26:26 NPK) in a combination of Zinc followed by RDF+Zn and urea deep placement (UDP) applied treatments were 7.8, 2.7, and 2.4% respectively. Among all, deep placement of urea briquette was found to be economic for the cultivation of Khumal Hybrid-2 maize variety while producing similar yield (2.4% higher) with 25% lower nitrogen dose, increasing agronomic nitrogen use efficiency by 10.41 kg/kg N, and economic benefit by US$30.4/ha compared to RDF.

Content of Trace Elements in Soil Fertilized with Potassium and Nitrogen

The aim of the study was to determine the effect of increasing potassium fertilization (0, 140, 190, and 240 mg K2O/kg of soil) in the interaction with nitrogen fertilization (130 and 170 mg N/kg of soil) on the trace elements content in the typical, non-contaminated agricultural soil. The trace elements content in the soil depended on nitrogen and potassium fertilization. Potassium fertilization had a more significant effect on trace elements content in the soil fertilized at the same time with a lower nitrogen dose (130 mg N/kg soil). Increasing potassium fertilization increased the content of cadmium by 83% and lead by 32% and reduced the amounts of chromium by 10% and iron by 3% in the soil, particularly in the series with a lower nitrogen dose (130 mg N/kg soil). The effect of potassium fertilization on the content of other trace elements was less unambiguous since, for most of trace elements, lower doses of this fertilizer contributed to growth of trace element, while higher doses lead to a decrease in their accumulation in the soil. Nitrogen fertilization increased the contents of zinc and iron—3%, copper—9%, manganese—12%, chromium—15%, and cobalt—59%, while reducing the contents of cadmium and nickel—24% and lead—45%. Permissible standards for trace elements content in the soil have not been exceeded.

COMO A IDADE DO PERFILHO E A ADUBAÇÃO NITROGENADA MODIFICAM AS CARACTERÍSTICAS ESTRUTURAIS DO CAPIM-MARANDU DIFERIDO?

Resumo Este estudo avaliou as características estruturais de perfilhos, com diferentes idades, do capim-marandu (Urochloa brizantha cv. Marandu) diferido e adubado. Foram avaliadas duas doses de nitrogênio (baixa, 50 kg ha-1 e alta, 200 kg ha-1), três categorias de idades de perfilhos (jovem, &lt;2 meses; maduro, 2 a 4 meses; e velho, &gt; 4 meses;), além de dois períodos (início, 1 a 45 dias e fim, 46 a 90 dias) durante o diferimento. O delineamento experimental foi inteiramente casualizado, em esquema de parcela sub-subdividida, com quatro repetições. De modo geral, o perfilho jovem apresentou melhor composição morfológica (40,0% de lâmina foliar viva, P=0,0074; 39,2% de colmo vivo, P=0,0208; e 20,8% de lâmina foliar morta, P=0,0155), enquanto que o perfilho velho teve pior morfologia (7,3% de lâmina foliar viva; 54,8% de colmo vivo; e 38,0% de lâmina foliar morta) ao término do período de diferimento. A percentagem de perfilho velho foi maior (P=0,0019) no fim (54,0%) do que no início (43,4%) do período de diferimento. No início do diferimento o dossel adubado com alta dose de N apresentou (P=0,0447) maior percentual de perfilho jovem (36,8%) do que aquele sob baixa dose de N (28,6%). No fim do período de diferimento, tanto a alta como a baixa dose de nitrogênio resultaram (P=0,0276) em valores similares de perfilho jovem no dossel diferido (24,3%, em média). A maior dose de N, parcelada antes do período de diferimento, aumenta o percentual de perfilho jovem durante a fase inicial do diferimento. O perfilho jovem tem melhores características estruturais do que os perfilhos maduros e velhos.

Influence of nitrogen fertilization on the seed yield and the content and quality of fat in pot marigold (Calendula officinalis L.) cultivars

Pot marigold seeds contain oil with a specific composition (presence of calendic acid); hence, they can be used as an alternative oil raw material. In 2011–2013, a field experiment was conducted to determine the effect of different nitrogen doses (0, 30, 60, 90, 120, 150 kg N∙ha-1) on the seed yield, oil content, and fatty acid composition in four pot marigold cultivars. Nitrogen fertilization exerted a positive effect on the number of flower heads and seed yield. However, the response of marigold cultivars to nitrogen doses applied varied, i.e. the yield of the ‘Tokaj’ and ‘Radio’ cultivars was significantly increased up to the dose of 60 kg N∙ha-1, whereas such an increase was noted in the ‘Orange King’ and ‘Persimmon Beauty’ cultivars at the dose of 90 kg N∙ha-1. Nitrogen fertilization modified the content of fat: the low nitrogen doses (30 kg N∙ha-1) did not influence the fat content in the seeds, whereas the increasing doses resulted in its gradual decline. The cultivars were characterised by significant differences in plant morphology, seed yield, and fat quality. During the three-year period, the highest seed and fat yields were determined for the ‘Orange King’ cultivar (1857.3 and 339.3 kg·ha-1, respectively) and the highest proportion of calendic acid in the oil (54.86%) was detected in the ‘Persimmon Beauty’ cultivar. The yield and quality of marigold oil depended on both nitrogen fertilization and the weather conditions prevailing during the growing seasons. The increase in the nitrogen doses was accompanied by an increase in the content of linoleic acid and a decrease in the level of oleic acid. The cooler and wetter growing season in 2011 turned out to promote the highest fat and calendic acid accumulation.

Effect of nitrogen fertilizer on biomass production and nodulation behavior of Pongamia pinnata Pierre seedlings under nursery conditions

At the seedling stage, a small amount of N is required to boost growth of leguminous plants. A pot experiment was conducted to observe the effect of N fertilizer on various growth parameters and nodulation behavior of Pongamia pinnata under nursery conditions. After the establishment of seedlings, four nitrogen treatments, 0, 40, 80 and 100 kg·ha−1 N were applied in two equal splits. Monthly observations were taken for the morphological parameters viz. plant height, collar diameter, leaf number, root length, root shoot ratio, nodule number and weight per plant. Maximum plant height was recorded after application of N at 40 kg·ha−1. Seasonally, the difference in collar diameter in rainy season was significantly higher than in winter or summer. However, more leaves were produced per plant at N-40 and N-100 treatments in winter and rainy seasons. Higher root length was recorded in rainy season than in winter or summer. Root biomass was higher than for stems or leaves. Seasonal effects of N-80 and N-40 treatments on leaf dry weight were significantly higher than for N-100 or N-0. Stem dry weight was higher at N-40 than at other treatments in winter and summer seasons. Root:shoot ratio was higher throughout winter to early summer. Nodule biomass was 2–3 times higher in rainy season compared to winter or summer. Maximum nodule number and biomass per plant were highest at N-40, followed by N-0, N-80 and N-100 treatments. New nodule formation started from June to the end of September. Maximum biomass per plant was recorded at N-40, followed by N-80, N-100 and N-0. Nitrogen treatment effect and seasonal behaviour interaction were not significant. Significantly higher numbers of nodules per plant were recorded in rainy season followed by summer and winter for all treatments. Higher nitrogen doses suppressed growth while lower doses promoted growth in Pongamia pinnata. Therefore, the lower nitrogen dose i.e., N-40 Kg·ha−1 applied in two equal splits was suitable at the initial nursery stage for the increase in nodulation and biomass production.

The effect of foliar application of Ekolist fertilizer on maize yielding and chemical composition

A pot experiment was conducted in Wagner-type pots of 5 kg soil capacity. The medium used for the investigation was light loam containing 22% of silt and clay. The plant subjected to testing was Blask variety of maize collected in caryopsis milk stage. The experimental scheme involved foliar application of Ekolist fertilizers: Mikro K, Mono Zn and Mono B within the frames of two levels of N fertilization 0.8 g (N1) and 1,6 g ( N2) per one pot as well as control object without foliar fertilizer used. The research showed that foliar application of Ekolist fertilizers at a lower nitrogen dose did not significantly affect the increase of maize dry matter yield in com-parison to control object. Fertilization with a higher nitrogen dose by foliar application of Ekolist Mono Zn and Ekolist Mono B fertilizers did significantly affect the increase in dry matter yield of maize in comparison to the control object. The highest content of microelements applied (Zn and B) was found in leaves and stems of maize for foliar application of Ekolist Mono and the mean content of analyzed microelements in aboveground parts of maize was higher with N-1 nitrogen dose in comparison to a higher nitrogen dose N-2.

The effect of foliar application of Ekolist fertilizer on maize yielding and chemical composition

Summary. A pot experiment was conducted in Wagner-type pots of 5 kg soil capacity. The medium used for the investigation was light loam containing 22% of silt and clay. The plant subjected to testing was Blask variety of maize collected in caryopsis milk stage. The experimental scheme involved foliar application of Ekolist fertilizers: Mikro K, Mono Zn and Mono B within the frames of two levels of N fertilization 0.8 g (N1) and 1,6 g ( N2) per one pot as well as control object without foliar fertilizer used. The research showed that foliar application of Ekolist fertilizers at a lower nitrogen dose did not significantly affect the increase of maize dry matter yield in comparison to control object. Fertilization with a higher nitrogen dose by foliar application of Ekolist Mono Zn and Ekolist Mono B fertilizers did significantly affect the increase in dry matter yield of maize in comparison to the control object. The highest content of microelements applied (Zn and B) was found in leaves and stems of maize for foliar application of Ekolist Mono and the mean content of analyzed microelements in aboveground parts of maize was higher with N-1 nitrogen dose in comparison to a higher nitrogen dose N-2.

Effect of nitrogen fertilization of corn on the development, survivorship, fecundity and body weight of Peregrinus maidis (Hom., Delphacidae)

Abstract: Corn plants, Zea mays L. cv. Saccharata ‘Guardian’ fertilized with low (100 mg N/l), medium (300 mg N/l) and high (500 mg N/l) nitrogen doses at three times per week were used to study the effect of foliar nitrogen on the development, survivorship, reproduction, intrinsic rate of increase and adult body weight of Peregrinus maidis (Ashmead), a serious pest and the vector of maize stripe tenuvirus and maize mosaic rhabdovirus in tropical and subtropical areas. The results showed that the higher nitrogen treatments resulted in the higher nitrogen concentrations in the plants. The insects that developed on corn plants receiving more nitrogen had a significantly shorter development time and higher immature survival rate and laid significantly more eggs. Plants with higher nitrogen concentration also resulted in significantly greater adult mass. Heavier body weight is advantageous because heavier adult females have greater daily oviposition rates than lighter ones. These life history parameters as well as population intrinsic rate of increase were positively correlated with the nitrogen levels in the treated plants. The differences of adult longevity and preoviposition period among different nitrogen treatments were also significant; however, no significant correlation was found between the nitrogen fertilization rate and adult longevity, as well as preoviposition period.

Efeitos da fertirrigação sobre a produção de palmito da pupunheira

Com o objetivo de avaliar o efeito da aplicação de lâminas de irrigação e níveis de adubação nitrogenada na produção de palmito de pupunheira (Bactris gasipaes Kunth), foi conduzido um experimento a campo, durante 22 meses, em Piracicaba (SP). Empregou-se o delineamento em blocos casualizados, com tratamentos distribuídos em esquema fatorial 3 (nitrogênio) x 4 (lâminas). Os níveis de nitrogênio corresponderam a 0; 200 e 400 kg ha-1 ano-1 de N, aplicados por meio de fertirrigações semanais. As lâminas de irrigação foram equivalentes a 0; 50; 100 e 120% da evapotranspiração de referência (Eto), determinada em função de tanque classe A. A produção de palmito por planta foi avaliada dos 30 aos 34 meses após o plantio. Houve efeito significativo dos tratamentos (irrigação e adubação) para todas as variáveis relacionadas à produção. Os tratamentos com menores lâminas e doses de nitrogênio apresentaram as menores produções. Levando-se em conta o crescimento da planta e a produção de palmito, os resultados indicam que irrigação com 100% da ETo e fertirrigação com 200 kg ha-1 ano-1 de N são as recomendadas para a pupunheira cultivada em condições de solo, clima e manejo cultural semelhantes às deste estudo.

Magnetically soft, high moment grain-refined Fe films: Application to magnetic tunnel junctions

The effect of N-doping on the microstructure and magnetic properties of thin Fe layers has been employed to construct all Fe-electrode magnetic tunnel junctions that displayed the tunneling magnetoresistance (TMR) effect. Using low nitrogen doses, a reduction in coercivity was achieved due to grain refinement, without a concurrent decrease in the saturation magnetization of the Fe films caused by the formation of crystalline iron nitride phases. It was demonstrated that this N-induced grain refinement can be applied beneficially to control the switching field of the “free” layer in magnetic trilayer structures. In general the ability to control magnetic softness without reducing saturation magnetization will prove important for incorporating high spin-polarized materials into spin valves and TMR devices.

Comparison of the energy performance of fibre sorghum, sweet sorghum and wheat monocultures in northern Italy

Four monocultures (fibre sorghum, sweet sorghum and wheat at high and low nitrogen doses) were compared at a field-scale over 3 years (1997–1999) in terms of net energy, net energy ratio and energy use efficiency. Two nitrogen fertilisation levels were assessed for wheat (80 and 120 kg ha −1 of N) to evaluate the energy use efficiency of the applications. For all the crops, fuels, lubricants and farm inputs together formed around 92% of the total input, mainly due to nitrogen fertilisation. A year×crop significant interaction was found for all considered parameters. In fact the monoculture did not lower the biomass yield of both sorghum types, while it involved a drop in wheat yield starting from the second year (third considering that wheat was also cultivated in the same field in 1996). The average (1997–1999) net energy supplied by the monoculture of sweet sorghum was 17, 40 and 50% higher than those of fibre sorghum and wheat at high and low nitrogen doses respectively. The energy use efficiency (EUE, i.e. the energy (MJ) requirement to produce a kg of dry matter) ranged from 0.78 to 0.96 for fibre sorghum, from 0.69 to 0.85 for sweet sorghum and from 1.00 to 1.23 and 0.91 to 1.33 for wheat at low and high nitrogen levels respectively. With ethanol as the end-product of the 3-year monoculture of sweet sorghum, the production process would be a bit less favourable in term of energy balance: the net energy yield would be 90% of that obtained by dry matter gasification (with an efficiency of 50%). If straw was not processed, ethanol from wheat was generally unfavourable. On average of the two nitrogen doses, net energy ratios were 0.99, 1.05 and 0.97 in the first second and third year respectively. If bagasse was not considered also sweet sorghum had a very low net energy ratio, but always higher than wheat (1.14, 1.12 and 1.24 over the 3 years).

Effect of Nitrogen Implants on Boron Transient Enhanced Diffusion

AbstractThe effect of nitrogen implants on boron transient enhanced diffusion was studied for nitrogen-only, boron-only, and boron plus nitrogen implants. A boron buried layer was used as a detector for interstitial supersaturation in the samples. Boron dose ranged from 1×1014 to 1×1015 cm−2 and N2+ dose from 5×1013 and 5×1014 cm−2. The energies were chosen such that the location of the nitrogen and boron peaks matched. After the implants, RTA and low temperature furnace anneals were carried out. The diffusivity enhancements were extracted from the buried layer profiles by simulation. Nitrogen-only implants were found to cause significant enhanced diffusion on the buried boron layer. For lower doses, the enhancement of the nitrogen implant is about half as that of boron whereas the enhancements are equal at higher doses. Nitrogen coimplant with boron increases the transient enhanced diffusion of boron at low boron doses, which implies that nitrogen does not act as a strong sink for excess interstitials unlike carbon. At high boron doses, nitrogen co-implant does not significantly change boron diffusion. Sheet resistance measurements indicate that low nitrogen doses do not affect the activation of boron whereas high nitrogen doses either reduce the activation of boron or the mobility of the holes.

Transformation of amorphous a-(Fe–B) phase during nitrogen implantation

Thin iron films (120 or 240 nm thick) were amorphized by boron implantation up to doses 2 × 10 17 and 1 × 10 17 ions/cm 2 at energies 60 and 24 keV, respectively. Amorphized iron films were then implanted with nitrogen ions in dose range 5 × 10 16–4 × 10 17 ions/cm 2 at energies 32 and 75 keV. Thicker films were annealed at 200°C, 350°C and 500°C after the implantation process. Implanted films were investigated by CEMS, AES and XPS methods. It was found that multi-energy implantation results in almost flat nitrogen and boron distribution. Investigations show that for low nitrogen doses an amorphous a-(Fe–B,N) m phase dominates in CEMS spectra. When the nitrogen concentration exceeds the boron one paramagnetic (Fe–B,N) p and Fe 2N phases at the expense of the crystalline α-Fe were formed. Annealing at 500°C leads to crystallization of a-(Fe–B,N) m through Fe 2B and γ ′-Fe 4N formation. The formation of chemical bond of B–N type was observed by AES and XPS in iron films with equal boron and nitrogen concentrations.

The impact of nitrogen fertilization of tomato on feeding site selection and oviposition by Trialeurodes vaporariorum

AbstractTomato plants, Lycopersicon esculentum Miller cv ‘Tres Cantos’, were supplied with high (308 ppm), medium (140 ppm) and low (84 ppm) nitrogen doses in order to determine the influence of nitrogen fertilization on feeding and oviposition site selection by greenhouse whitefly adults, T. vaporariorum (Westwood). The nitrogen and water content was higher in plants supplied with 308 N ppm than in plants with medium or low nitrogen doses and no differences were found in soluble sugar content. The leaves of the upper plant stratum (leaves 1–5) had the greatest nitrogen and water content, independent of the nitrogen dose applied. The plants were exposed to T. vaporariorum adults into a greenhouse under two current (late autumn‐winter and spring‐early summer) situations of the tomato crop in the Mediterranean area. The distribution of whitefly adults on the plants was affected by the nitrogen dose in both experimental conditions, the number of adults was higher on the plants supplied with high nitrogen dose. Within plants, adult distribution was affected by leaf position, the upper plant stratum being preferred for feeding. Whitefly females selected for oviposition and laid more eggs on plants and leaves of plants with higher nitrogen and water contents. We conclude that whitefly host selection for feeding and ovipositing are related to differences in nitrogen and water content of the host plant.