High Doses Of Nitrogen Research Articles

Morphogenesis, Structure, and Tillering Dynamics of Tanzania Grass under Nitrogen Fertilization in the Amazon Region

Nitrogen fertilization is one of the main management strategies for continuous pasture management with high productivity. We examined the effects of nitrogen fertilization on the morphogenic, structural, and tillering dynamic characteristics of Tanzania grass in the Amazon region in the state of Pará, Brazil. The study was conducted using a randomized block design with six treatments (0, 100, 200, 300, 400, and 500 kg N ha−1 year−1) and five replicates. The treatments were performed during the rainy season in 2016 and 2017 using urea as the nitrogen source. The leaf elongation rate was increased by 68.5% compared with that of the control treatment (p < 0.01). The leaf appearance rate and number of alive leaves increased with higher doses of nitrogen (p < 0.01, each). The regrowth period was reduced by approximately 13 days under 500 kg N ha−1 (p < 0.01), thus providing more production cycles. Nitrogen fertilization was also associated with a higher tillering rate (p < 0.01); however, the rate of this increase decreased with increasing nitrogen dose. Higher nitrogen doses thus improved the development of Tanzania grass; however, this became less pronounced at doses < 300 kg N ha−1.

Optimal Nitrogen Fertilizer Rates for Soybean Cultivation

The soybean (Glycine max. L. Merr) can satisfy a large portion of its requirement for nitrogen (N) by living in symbiosis with symbiotic bacteria. However, this source of N may be inadequate in varieties with high yield potential. To fully exploit this potential, soybeans should additionally utilize mineral forms of nitrogen present in the soil. The aim of this study was to determine the effect of varied nitrogen fertilizer application rates on the dry weight of the separated parts of soybean plants and the whole plant, including the number and weight of root nodules, the potential to reduce atmospheric nitrogen (N2), and the content and uptake of nitrogen. Four levels of pre-sowing nitrogen fertilizer supply were tested: 0, 60, 120, and 180 kg N·ha−1. Measurements of the tested parameters were taken during the flowering stage and the fully ripe stage. During the flowering stage, a reduction in the number of root nodules was observed following the application of 120 and 180 kg N·ha−1. In the fully ripe stage, each increase in nitrogen application caused a systematic decrease in the number of nodules on the roots. Increasing the level of nitrogen application therefore reduced the N2 fixation potential of soybeans, regardless of the developmental stage. The use of high doses of nitrogen in soybean cultivation did not increase seed yield or the weight of the entire plant. With high doses of nitrogen, the content and accumulation of nitrogen in soybean seeds and total mass did not increase. Therefore, the content and yield of crude protein did not increase. The main organ of nitrogen accumulation in the soybean flowering stage was the leaves (58.6–64.8% of total N uptake), however, in the fully ripe stage, it was the seeds (66.8–74.2% of total N uptake).

Effect of weed management options and nitrogen scheduling on weed dynamics and yield of wheat (Triticum aestivum) under Central Plain Zone of Uttar Pradesh

A field experiment was conducted during the winter (rabi) seasons of 2014–2015 and 2015–16 at Kanpur, Uttar Pradesh, to study the effect of weed-management options and nitrogen scheduling on weed dynamics and yield of wheat (Triticum aestivum L.). Common infesting weeds which appeared in wheat field were Phalaris minor Retz. and Cynodon dactylon (L.) Pers. among grasses, and Chenopodium album L., Anagallis arvensis L., Melilotus alba Medik. and Convolvulus arvensis L. as broad-leaf weeds. Moreover, among sedges, only 1 species, Cyperus rotundus L. was observed. Among the weed-management options, mesosulfuron-methyl + Iodosulfuron-methyl sodium (400 g/ha) with higher dose of nitrogen (150 kg N/ha) applied in 3 spilt applications [50% as basal + 25% at crown-root initation (CRI) + 25% at flowering] proved significantly superior in minimizing the density (33%) and biomass of weeds (34%) at 60 days after sowing (DAS). The former treatment increased the leaf-area index (LAI) and SPAD values that elevated the production of wheat grain yield. Among time of nitrogen application, 3 splits (50% as basal + 25% at CRI + 25% at flowering) enhanced the nutrient-uptake efficiency (27.4%) and total nutri ent uptake (40.2%) by crop than 3 equal splits at sowing (basal), CRI and flowering. Higher dose of nitrogen (150 kg N/ha) resulted in higher yield (15.7%) and nutrient uptake (13.4%) than its lower dose. Thus, application of ready-mixed post-emergence herbicides, i.e. mesosulfuron + iodosulfuron (400 g/ha) with higher dose of nitrogen (150 kg N/ha) applied 50% as basal and 25% top-dressed at CRI and 25% at flowering was most effective with re spect to weed-suppression, yield and economics of wheat.

Innovative Fertiliser Based on Urea and Ammonium Nitrate Solution with Potassium Thiosulphate as a Crucial Factor in Shaping Plant Yield and Its Parameters

In the cultivation of crops in recent times, in addition to taking care of the balanced supply of nutrients to plants and the protection of soil resources, it is also important to take into account the non-productive factor by implementing production systems based on balanced fertilisation. The aim of this study was to demonstrate the effect of soil kind and the application of a new fertiliser based on a urea and ammonium nitrate solution with potassium thiosulphate (UAN-KTS) on the yielding and biometric characteristics of spring wheat, spring rape, and maize to determine the optimal N:K:S ratio. An increase in the soil kind increased the weight of 1000 spring rape seeds, the yield of maize fresh matter, a reduction in the height of spring wheat and maize plants, a reduction in the yield of spring wheat grains and straw, and the yield of the fresh and dry matter of spring rape straw. A higher nitrogen dose promoted the growth of spring rape at the later growing stage and maize and had a positive effect on the yield of spring wheat grains and straw, spring rape seeds and straw, and the above-ground parts of maize. The application of potassium fertilisers caused a significant increase in the spring rape plant height, an increase in the yield of spring wheat grains and straw and spring rape seeds and straw, the above-ground parts of maize, a reduction in the plant height at the beginning of the spring wheat growing period, and a reduction in the weight of 1000 spring rape seeds (only on the soil with rich quality). The fertiliser with the N:K2:S2 ratio had a particularly favourable effect on the yielding of spring wheat. In the cultivation of maize, the same effect was most often obtained under the influence of fertiliser in the ratio of N:K1:S1 on the weaker soil fertilised at the same time as a higher dose of nitrogen (N 1) and N:K2:S2 (in other cases). In the case of spring rape, generally, fertiliser with N:K1:S1 was the strongest, although, in some objects, a higher yield was achieved under the influence of N:K2:S2. The existence of statistically confirmed correlations (expressed as the percentage of the variability observed) between the soil kind and the fertilisers applied and the yielding and biometric characteristics of the plants were observed.

Impact of Nitrogen and Silicon Amendments on Hopper Population in Rice

Present study showed that total dry weight values of rice plants were significantly higher in the plant with high nitrogen (N) application (100kg/ ha) as compared to low nitrogen (30 kg/ ha) treatment whereas the silicon (Si) amendment had very little effect on biomass accumulation but both the elements are associated with hopper pest population densities in rice. Here the correlation coefficient values were high- r= 0.759 to 0.999 and r= 0.726 to 0.996 for brown planthopper Nilaparvata lugens (Stål) and green leafhopper Nephotettix virescens (Dist.) respectively when the calculation was made between insect population and plant biomass after application of nitrogen 0 to 100 kg/ ha. However, when calcium silicate was added 140 kg/ ha or above with high doses of nitrogen the N. lugens and N. virescens incidence reduced in comparison to others. Consequently, the interaction between nitrogen and silicon play a significant role in resistance to these hopper pests.

Nutritional Value of Parsley Roots Depending on Nitrogen and Magnesium Fertilization

Parsley is an herb/vegetable rich in nutritional compounds such as carbohydrates, vitamins, protein, crude fiber, minerals (especially potassium), phosphorus, magnesium, calcium, iron, and essential oils. Limited information is available in the literature on the quality of parsley roots depending on the cultivation technology used in the form of macronutrients and micronutrients, preparations to stimulate plant growth and development, as well as plant-protection products. A three-year study was undertaken to determine the effect of applying mineral fertilization with nitrogen, including magnesium on the nutritional value of parsley roots in terms of the content of ascorbic acid, total and reducing sugars, and minerals: (total N, K, Mg, Ca). The research material was the root of Petroselinum crispum ssp. tuberosum from an experiment where nitrogen was applied in soil at (0, 40, 80, 120 kg N ha−1) and magnesium at (0, 30 kg MgO ha−1). Nitrogen fertilization increased the nutritional value in terms of total and reducing sugars, as well as total N and Ca content. Applied magnesium fertilization caused a significant increase in the content of all tested nutrients. The most total sugars (127.7 g kg−1 f. m.), reducing sugars (16.8 g kg−1 f. m.), and total N (12.13 g kg−1 d. m.) were accumulated by roots from the object where nitrogen was applied at a maximum rate of 120 kg N ha−1, including magnesium. On the other hand, for the content of K (19.09 g kg−1 d. m.) in the roots, a dose of 80 N ha−1 was sufficient. For ascorbic acid (263.2 g kg−1 f. m.) and Ca (0.461 g kg−1 d. m.), a dose of 40 kg N ha−1 with a constant fertilization of 30 kg MgO ha−1 was sufficient. When applying high doses of nitrogen, lower doses of magnesium are recommended. This is sufficient due to the high nutritional value of parsley roots. Due to the worsening magnesium deficiency in soils in recent years, the use of this nutrient in the cultivation of root vegetables is as justified and timely as possible. Quality-assessment studies of root vegetables should be continued with higher amounts of magnesium fertilization. Different ways of applying magnesium in parsley cultivation should also be tested.

Inoculation effects of growthpromoting bacteria on corn root architecture: influence of nitrogen levels, bacterial populations, and plant genotypes

ABSTRACT Inoculating corn with diazotrophic bacteria as growth promoters has been demonstrated to be an efficient agricultural practice in Brazil, mainly due to the root stimulation they provide to plants. This study investigates the corn (Zea mays L.) root architecture in a greenhouse assay where A. baldaniorum Sp245 and H. seropedicae ZAE94 strains were inoculated and evaluated for 22 days under two N levels: 0.6 and 6 mmol L -1 of N. Short-term bioassays were conducted to assess the plant’s response to the addition of indole-acetic acid, two bacterial populations, and two corn genotypes, utilizing image capture software WinRhizo Pro. The growth and distribution of tips, crossing, and length of fine roots were determined to be the most sensitive aspects to inoculation and indole-acetic acid induction. These responses were influenced by the genotype and the number of bacterial cells present. Biomass accumulation analyses quantified these modifications after a 22-day period. Additionally, the growth response was found to be more significant when applying the Hs-ZAE94 strain to plants fertilized with a higher dose of nitrogen (6.0 mmol L -1 ), and this response was positively correlated with bioassay data. Selected strains used as an inoculant can improve root architecture and, consequently, the N use efficiency.

Determination of Combined Effects of Organic and Mineral Fertilizer on Forage Yield and Quality of Annual Ryegrass

The widespread practice of using high doses of nitrogen to increase unit area yield in annual ryegrass introduces ecological and economic problems. This research was carried out over two years and aimed to determine the potential forage yield and quality of annual ryegrass by applying manure, humic acid, and low doses of nitrogen fertilizer, within the framework of sustainable forage crop cultivation. The study was carried out from 2020 to 2022 with three replications according to the randomized block split plots experimental design. According to the study results, the highest values were achieved with combinations that included manure application, and even higher values were observed when manure was applied along with low doses of humic acid and nitrogen. The M20 + H20 + N100 treatment yielded the highest fresh yield, dry matter, and crude protein. The treatments with manure, humic acid, and nitrogen fertilizer had varying effects on the ADF and NDF content of annual ryegrass, resulting in fluctuating values. In conclusion, 20 t manure, 20 L humic acid, and 100 kg ha−1 N application can be suggested for sustainable and higher dry matter production with good quality for annual ryegrass cultivation under semi-humid climatic conditions. The results obtained from this research hold promise for sustainable agricultural practices.

Impact of Nitrogen Levels on the Growth and Medicinal Properties of Periwinkle (Catharanthus roseus) in an Inceptisol of Varanasi, India

Aims: Periwinkle (Catharanthus roseus), is a perennial herbaceous, belongs to the Apocynaceae family. The medicinal poperties are more economically important than the yield of the plant. Nitrogen is the main nutrient affect the medicinal properties of the plant. The main aim of this study was the evaluation of the effects of nitrogen on growth of the Catharanthus roseus and the presence or absence of alkaloid vinblastine.
 Place and Duration of Study: The experiment involved a pot experiment conducted during Rabi season of 2021-2022 in the net house, at Agricultural Research Farm of the Institute of Agricultural Sciences, Banaras Hindu University, Varanasi.
 Methodology: The experiment was laid out in a completely randomized design (CRD) with five nitrogen levels i.e. Control (RDF), 2.5g urea/pot, 5.0g urea/pot, 7.5g urea/pot and 10.0g urea/pot in three replications. Plants fed with recommended dose of P: K (40:40) and nitrogen fertilizer according to treatment.
 Results: Higher dose of nitrogen i.e., 10.0 g/urea (T5) showed the greatest increase in plant height, number of branches, flowers per plant and SPAD value while number of leaves per plant was maximum at 2.5 g urea/pot (T2) whereas the lowest growth were exhibited in control treatment (T1). The presence or absence of vinblastine was tasted by Thin Layer Chromatography (TLC) and the result showed that at all the levels of nitrogen treatment, vinblastine was present except at control treatment (T1) till a month after transplanting.

Effect of mineral fertilizers on the taste qualities of apple varieties

This article presents the results of a 3-year research study into the effect of soil and foliar application of nitrogen and potassium fertilizers on the taste qualities of the Veniaminovskoe (Rvi6) and Sinap Orlovskii (3×) apple varieties bred at the Russian Research Institute of Fruit Crop Breeding (VNIISPK). The assumption that varietal features are the most important factor that determines taste was confirmed. In addition, the influence of weather conditions of the growing season on the chemical composition of fruits was observed. Thus, the year of 2019 was characterized by the most favorable weather conditions of the growing season. In August, during fruit ripening, the optimum temperature and humidity regime had a positive effect on the accumulation of soluble solids, sugars, and titratable acids in both varieties under study. However, the varieties responded differently to the same doses of mineral fertilizers. The application of fertilizers had no significant impact on the content of the studied components and the sugar-acid ratio in Veniaminovskoe fruits. Conversely, Sinap Orlovsky was found to be responsive to this agricultural practice. In 2019, the joint application of triple foliar and soil fertilizing using N30K40, N60K80, and N90K120 in various doses had a positive effect on the reduction of titratable acidity in fruits of this variety. As a result, the sugar-acid ratio increased by 1.3–1.9 times. Over the entire study period (2017–2019), a significant decrease in the content of sugars in Sinap Orlovsky fruits was observed in the variant with additional foliar fertilizing compared to the control. During the study period, the high doses of N90K120 nitrogen and potassium fertilizers along with foliar application contributed to a significant increase in the sugar-acid ratio in Sinap Orlovsky fruits, which significantly exceeded the control.

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.

Evaluation of the application of fertilizers and biostimulants in Zephyranthes lindleyana Herb (Amarylidaceae) under greenhouse conditions

Objective: To evaluate the effect of different doses of N, P, K fertilizers and two biostimulants, on growth parameters and vegetative development in plants of the species Z. lindleyana Herb. Design/methodology/approach: An experiment was established under greenhouse conditions under a CRD; ten treatments with five repetitions were tested, with different doses of N, P and K and two biostimulants. The experimental unit was one plant per pot. Data were analyzed with descriptive statistics, non-parametric Kruskal-Wallis tests (α=0.05). Budding, flowering, leaf height, number of leaves and seed production were measured. Results: Vegetative development was distinguished in all plants. Only six treatments showed flowering. The percentage of floral and vegetative sprouting did not show delay or advance in the physiology of the plant. In leaf height and number of leaves, different behaviors were detected in the treatments, not detected in the Kruskal-Wallis tests. The plants treated with high doses of NPK fertilization and combined with biostimulants showed inflorescences and seed production. Limitations on study/implications: Being a native plant with ornamental potential, the collection of this species is a challenge due to the lack of studies on the potential distribution of the species. Findings/conclusions: This species can be cultivated under a greenhouse and pot planting system. Floral budding, height and number of leaves is stimulated by high doses of nitrogen. The combination of NPK and biostimulants favors development/growth and seed production.

Azospirillum brasilense Reduces the Effects of Water Stress and Increases Maize Yield in Irrigated Areas with High Soil Nitrogen Doses

Azospirillum brasilense Reduces the Effects of Water Stress and Increases Maize Yield in Irrigated Areas with High Soil Nitrogen Doses

Effect of Tillage and Nitrogen Fertilization on Soil Properties and Yield of Five Durum Wheat Germoplasms in a Dry Area of Morocco

In Morocco, cereal production is below the expected potential. The adoption of best agricultural practices that reduce vulnerability to climate is a major requirement. No-tillage (NT) agriculture is a system that could improve cereal production by enhancing soil fertility. Some factors, in combination with no-tillage, can further improve cereal yields, especially the choice of variety the adequate fertilization. The objective of our study is to investigate the effect of no-tillage agriculture and nitrogen fertilization on soil fertility and the yield of five durum wheat varieties developed in Morocco in a long-term (18 years) NT trial at the INRA Merchouch experimental station, Morocco. The results show that tillage type had a significant effect on soil organic carbon and CEC (measured before the start of the experiment), as well as on ammonium and nitrates (measured at the end of the experiment), whereas nitrogen dose had a significant effect on total nitrogen and nitrates (measured at the end of the experiment). Regarding wheat yield, as measured at the end of the experiment during the 2020–2021 cropping season, the results show that, under NT, the varieties Nachit, Faraj, and Louiza had grain yields of 4.5, 4.3, and 3.4 t ha−1 and straw yields of 9.8, 7.8, and 6.8 t ha−1, respectively, whereas the I.C and M.G germoplasms had grain yields of 4.05 and 3.72 t ha−1 and straw yields of 8.25 and 8.39 t ha−1, respectively. These values are low for a favorable area and correspond to a semi-arid area. In addition, no effects of nitrogen dose were observed due to water stress, which reduced nitrogen use efficiency. Nachit is the most adapted variety under NT, with the highest yield (5.1 t ha−1) under a low dose of nitrogen (20 kg N ha−1), followed by Faraj (4.7 t ha−1), still under NT but with a higher nitrogen dose (40 kg N ha−1) and Nachit (4.5 t ha−1) with the minimum nitrogen dose but under both NT and CT. In conclusion, Nachit and Faraj wheat varieties performed the best under no-tillage conditions with the minimal nitrogen dose. However, grain yield values were reduced, owing to water stress, which reduced nitrogen use efficiency.

Adaptation Strategies for Optimum Sowing of Wheat Varieties and Validation Through Ceres-Wheat Model In Changing Climatic Conditions Under Shivalik Range of N-W Himalayas

Experiments were conducted at Research Farm of Agromet Research Centre, SKUAST-Jammu, during rabi 2015-16 and 2016-17, and comprised of 3 varieties, 3 sowing environments and 3 N-levels laid out in split-split plot design. The growth and development of wheat crop was also validated through CERES-Wheat model. Earlier sown wheat took more days for physiological maturity as compared to normal and late sown crop. WH-1105 variety took maximum days for physiological maturity and followed by HD-2967 and RSP- 561. Higher dose of nitrogen took more calendar days for physiological maturity as compared to lower doses of nitrogen. WH 1105 variety recorded significantly superior grain and biological yield as compared to HD 2967 and RSP 561. The coefficient of determination (R2) between validation of observed and simulated days to anthesis and maturity was 0.79 and 0.76, respectively. The values obtained for R2 during validation of CERES-wheat model for grain yield of wheat was 0.78. Maximum temperature during reproductive stage showed distinct effect on grain yield of crop. Bangladesh J. Bot. 51(4): 759-765, 2022 (December)

Combined effect of acute salt and nitrogen stress on the physiology of lichen symbiotic partners

Nitrogen pollution and excessive salinity are commonly regarded as one of the major environmental concerns in recent decades in many urban environments. Although in urban areas lichens are exposed to both salt and nitrogen stress, no studies have been conducted to date on the simultaneous impact and interaction of these factors on lichen physiology. The aim was to determine the effect of various combinations of NaCl and NH4NO3 doses on the physiology of epigeic lichen Cladonia rei. We also aimed to compare the response of lichens collected from polluted and unpolluted sites to verify whether lichens exposed to different levels of environmental stress in their native environment will react differently. The combined salt-nitrogen treatment caused significant disturbances in the integrity of cell membranes and chlorophyll fluorescence parameters. The most detrimental effect concerned the loss of cell membrane integrity, which suggests that this parameter can serve as a relevant indicator of acute salt-nitrogen stress incidents. Salt stress decreased the photosynthetic efficiency 1 h after exposure, but after 72 h, the FV/FM returned to the level characteristic of healthy lichens in experimental groups without and with small doses of ammonium nitrate. In contrast, recovery was not possible in combination with high nitrogen doses. This indicates that exposure to short-term salt stress in a nitrogen-poor environment only causes a temporary reduction in photosynthetic efficiency, but in urban eutrophic environments may have more serious consequences. The weakened physiological condition of the mycobiont manifested by an increased level of cell membrane damage and a persistent decrease in the photosynthetic efficiency of the photobiont in lichens growing along the roads may indicate an excess of nitrogen in the environment, enhanced by the effect of salt. Lichens collected from a heavy-metal-polluted habitat responded more strongly than those from an unpolluted habitat suggesting that in lichens previously affected by certain harmful factors, exposure to another stress factor may lead to greater disturbances. This is of particular importance for lichens inhabiting the vicinity of roads, since they are also under the influence of other pollutants emitted by road traffic.

Response of maize (Zea mays L.) to different nitrogen doses under the mild tropical plain agroclimatic zone of North-East India

Formulating optimum quantity of nitrogen fertilization is highly necessary to attain higher yields in maize. As per soil fertility, the right dosage has to be formulated for each region with consciousness on the soil and environmental health. A field experiment was conducted during 2018-19 under mild tropical plain agroclimatic conditions of Arunachal Pradesh, India to investigate the effect of different nitrogen doses on growth and yield of maize. The experiment was laid out under randomized block design with five replicated plots for each treatment. The nitrogen through urea was supplied with different doses of 0, 100, 120, 150 and 180 kg/ha. The crop was evaluated for plant height, number of leaves, leaf length, number of kernels per cob, number of rows per cob, and total grain yield. The results revealed that the variables such as plant height, number of leaves, leaf length, number of kernels per cob, number of rows per cob and total grain yield were significantly (P less than 0.05) affected by the different levels of nitrogen doses. Number of leaves, leaf length and crop yield were highest in 180 kg/ha (nitrogen dose), while lowest in control which significantly increased with higher nitrogen doses. This result showed that nitrogen with higher doses was more effective than low doses for maize crop. Nitrogen fertilization at 180 kg/ha exerted a significantly higher and positive effect on maize growth and can be recommended for the region.

Enhanced Isohydric Behavior Decoupled the Whole-Tree Sap Flux Response to Leaf Transpiration under Nitrogen Addition in a Subtropical Forest

Anthropogenic nitrogen deposition has the potential to change the leaf water-use strategy in the subtropical region of China. Nevertheless, the whole-tree level response crucial for the ecosystem functions has not been well addressed over the past decades. In this study, the stem sap flux density (JS) was monitored for the whole-tree water transport capacity in two dominant species (Schima superba and Castanopsis chinensis) in a subtropical forest. To simulate the increased nitrogen deposition, the NH4NO3 solutions were sprayed onto the forest canopy at 25 kg ha−1 year−1 (CAN25) and 50 kg ha−1 year−1 (CAN50), respectively, since April 2013. The JS and microclimate (monitored since January 2014) derived from the whole-tree level stomatal conductance (GS) were used to quantify the stomatal behavior (GS sensitive to vapor pressure deficit, GS-VPD) in response to the added nitrogen. The maximum shoot hydraulic conductance (Kshoot-max) was also measured for both species. After one-year of monitoring in January 2015, the mid-day (JS-mid) and daily mean (JS-mean) sap flux rates did not change under all the nitrogen addition treatments (p > 0.05). A consistent decline in the GS-VPD indicated an enhanced isohydric behavior for both species. In addition, the GS-VPD in the wet season was much lower than that in the dry season. S. superba had a lower GS-VPD and decreased JS-mid/JS-mean, implying a stronger stomatal control under the fertilization, which might be attributed to the low efficient diffuse-porous conduits and a higher JS. In addition, the GS for S. superba decreased and the GS-VPD increased more under CAN50 than that under CAN25, indicating that the high nitrogen dose restrains the extra nitrogen benefits. Our results indicated that the JS for both species was decoupled from the leaf transpiration for both species due to an enhanced isohydric behavior, and a xylem anatomy difference and fertilization dose would affect the extent of this decoupling relation.

Effect of Varying Nitrogen and Micronutrient Fertilization on Yield Quantity and Quality of Sunflower (Helianthus annuus L.) Achenes

Sunflower is a good alternative crop in rotation, even in light soils. This is due to the changing climate, economic factors and the need to reduce agriculture pressure on the environment. In this field experiment, the effect of soil nitrogen doses (60 and 90 kg ha−1) and additional foliar fertilization (B, Cu, Fe, Mn, Mo, Zn) on selected plant characteristics, yield and quality of sunflower achenes was assessed. The single-factor experiment was conducted in 2020 and 2021 on Luvisol soil. It was shown that a higher nitrogen dose had a positive effect on plant biometric features, protein content in achenes, as well as LAI (leaf area index) and SPAD (soil plant analysis development) indices. Additionally, the applied double foliar spraying resulted in an increase in yield components and quality of achenes. Sunflower yielding depended on the interaction of weather conditions with fertilization. In the first year of the research, high yields were obtained after applying 60 or 90 kg N ha−1 in combination with double foliar fertilization (3.68 and 3.65 t ha−1, respectively). A significantly lower yield was recorded after applying only the 60 kg N ha−1 dose. This was not statistically confirmed in the second year of the study, with a higher average yield of 3.79 t ha−1. Economic calculations showed that the optimal option was to use 60 kg N ha−1 together with single or double foliar fertilization. Fertilizing with 90 kg N ha−1 in combination with micronutrient spraying was the least profitable.

Manipulation of Senescence of Plants to Improve Biotic Stress Resistance

The physiological state, i.e., senescence or juvenility, of plants and plant organs can have strong effect on their reactions to pathogen attacks. This effect is mainly expressed as changes in the severity of disease symptoms. Generally, necrotrophic pathogens cause more severe symptoms on senescent than on juvenile plants, while biotrophs prefer juvenile tissues. Several factors of senescence have opposite effect on the two pathogen groups, such as decreased photosynthesis, decreased antioxidant capacity, remobilization of nutrients, changes in plant hormonal network, and in fluidity of cell membranes. Furthermore, senescent tissues are less tolerant to toxins and to cell-wall-degrading enzymes. On the other hand, pathogen infection itself has significant effect on the physiology of plants depending on the lifestyle of the pathogen and on the compatibility or incompatibility of the interaction with the plant. There are several possibilities to manipulate the physiological state of plants in order to improve their biotic and abiotic stress tolerance, such as removal of the terminal bud or high doses of nitrogen, external application of cytokinins or of inhibitors of ethylene action, as well as by spontaneous or directed mutation, in vitro selection, or manipulation by various transgenic approach. Even application of mycorrhiza can inhibit the senescence process of plants and improve their tolerance to stresses.