Effects Of Different Nitrogen Research Articles

Effect of nitrogen and phosphorus on growth and yield of mungbean

Nutrient management and their balance application are crucial for the high productivity of the crops; nitrogen and phosphorus are the essential nutrients, which are often deficient in the soil and must be supplied to the crops through various sources. The excessive application of these nutrients can lead to increased emissions of greenhouse gases and contribute to eutrophication, water pollution, and many other issues. To determine the optimal application rate of these nutrients, a field experiment was conducted in ANASTU research farm, Kandahar, in 2023 to evaluate the effects of different nitrogen and phosphorus levels on the growth and yield of mungbean (Vigna radiata L.). Treatments comprised three levels of nitrogen (0, 20, and 40 kg ha-1) and four levels of phosphorous (0, 40, 60 and 80 kg P2O5 ha-1). The study was carried out using an RCBD design with three replications. The results showed that 20 kg N ha-1 and 40 kg P2O5 ha-1, together and separately, enhanced growth parameters (Plant height, leaf area, dry matter, branches plant-1), yield attributes (Pods plant-1, grains pod-1, 100-grain weight and pod length) and grain, stover and total yield, significantly. Overall, this study indicates that the mungbean should be fertilized with 20 kg N ha–1 and 40 kg P2O5 ha–1 in Dand district of Kandahar province.

Effects of different nitrogen applications and straw return depth on straw microbial and carbon and nitrogen cycles in paddy fields in the cool zone

Straw is an important source of organic fertilizer for soil enrichment, however, the effects of different nitrogen(N) application rates and depths on straw decomposition microorganisms and carbon and nitrogen cycling under full straw return conditions in cool regions of Northeast China are not clear at this stage. In this paper, we applied macro-genome sequencing technology to investigate the effects of different N application rates (110 kg hm−2, 120 kg hm−2, 130 kg hm−2, 140 kg hm−2, 150 kg hm−2) and depths (0–15 cm, 15–30 cm) on straw decomposing microorganisms and N cycling in paddy fields in the cool zone of Northeast China. The results showed that (1) about 150 functional genes are involved in the carbon cycle process of degradation during the degradation of returned straw, of which the largest number of functional genes are involved in the methane production pathway, about 42, the highest abundance of functional genes involved in the citric acid cycle pathway. There are 22 kinds of functional genes involved in the nitrogen cycle degradation process, among which there are more kinds involved in nitrogen fixation, with 4 kinds. (2) High nitrogen application (150 kg hm−2) inhibited the carbon and nitrogen conversion processes, and the abundance of straw-degrading microorganisms and nitrogen-cycling functional genes was relatively high at a nitrogen application rate of 130 kg hm−2. (3) Depth-dependent heterogeneity of the microbial community was reduced throughout the vertical space. At 71 days of straw return, the nitrogen cycling function decreased and some carbon functional genes showed an increasing trend with the increase of straw return depth. The nitrogen cycle function decreased with the increase of straw returning depth. The microbial community structure was best and the abundance of functional genes involved in the nitrogen cycling process was higher under the conditions of 0–15 cm of returning depth and 130 kg hm−2 of nitrogen application.

Plasticity in nitrogen form uptake and preference in response to long-term nitrogen addition of the main tree species in a temperate old growth forest

ABSTRACT We conducted a short-term field hydroponic 15N labeling experiment to study the effects of different nitrogen (N) addition treatment on the N uptake preference and rate of plant fine roots in a temperate old growth forest in 2018. The results indicated that the N preference of dominant tree species for different N chemical forms was not influenced by the N addition, with the N acquisition pattern being ammonium > nitrate > glycine. However, N addition altered the plant's N uptake rates. Under low N treatment, the uptake rates of glycine for three target tree species significantly increased. Both low and medium N additions significantly enhanced the NH4–N uptake rate, but had little impact on the NO3–N uptake rate. Conversely, high N addition exerted negative effects on NO3–N and NH4–N uptake rate. Different tree species may flexibly adapt to new environmental conditions by adapting to their root morphology and the relationship between plant growth and N uptake. N addition has pronounced effects on N uptake rate and root morphology traits of dominant tree species. Overall, this study contributes to a deeper understanding of the response of N uptake patterns in temperate forests to long-term N addition.

Ammonium bicarbonate alleviates apple replant disease: Inhibiting Fusarium and improving soil environment

Providing nitrogen is the core of increasing production in modern agricultural systems, as well as in the production of fruit trees. The rational application of nitrogen is an important measure to increase production and sustainably utilize agricultural ecosystems. Greenhouse, pot and field experiments were conducted to study the effects of different nitrogen forms on the antifungal effect in vitro, apple growth status and the soil environment under replant condition, aims to provide a basis for scientific fertilization and alleviates apple replant disease during orchard construction. We investigated the growth of apple in replant soil treated with different forms of nitrogen, including ammonium nitrogen (NH4N), nitrate nitrogen (NO3N) and amide nitrogen (CO(NH2)2). The results showed that ammonium bicarbonate can inhibit the mycelial growth, spore germination and toxins synthesis of soil-borne pathogens in vitro. The addition of ammonium bicarbonate significantly promoted the replanted apple growth. The activities of soil sucrase, urease, phosphatase and catalase were higher following treatment with ammonium bicarbonate than in the control soil. The qPCR analysis showed that the bacterial, fungal biomass differed distinctly between the different nitrogen forms and the control. These results suggest that ammonium bicarbonate can inhibit the mycelial growth, spore germination and toxins synthesis of soil-borne pathogens, improve the activities of soil enzymes and change soil microbial biomass. These changes can promote growth ofreplanted apple, thereby, ammonium bicarbonate can be used to alleviate apple replant disease as a new control measure.

Effect of different NPK fertilization timing sequences management on soil-petiole system nutrient uptake and fertilizer utilization efficiency of drip irrigation cotton

In order to elucidate the effects of different nitrogen (N), phosphorus (P), and potassium (K) fertilization timing sequences management on nutrient absorption and utilization in drip irrigation cotton, field experiments were conducted from 2020 to 2021. There are six timing sequences management methods for NPK fertilization (S1–S6: 1/3Time N–1/3Time PK–1/3Time W, 1/3Time PK–1/3Time N–1/3Time W, 1/2Time NPK–1/2Time W, 1/4Time W–1/4Time N–1/4Time PK–1/4Time W, 1/3Time W–1/3Time NPK–1/3Time W), among which S6 is the current management method for field fertilization timing sequences, and S7 is the non N. The results showed that during the main growth stage, S5 accumulated more nitrate nitrogen (NO3–-N) and ammonium nitrogen (NH4+-N) content in soil between 20 and 40 cm, and accumulated more available phosphorus content in soil between 5–15 cm and 15–25 cm, S5 reducing N leaching and increasing P mobility. It is recommended to change the timing sequences management method of NPK fertilization for drip irrigation cotton to 1/4Time W–1/4Time PK–1/4Time N–1/4Time W, which is beneficial for plant nutrient absorption and utilization while reducing environmental pollution.

Simultaneous degradation efficiency of C-MFCs for three pollutants in aquaculture wastewater

<p>Chlorella microbial fuel cells may be an alternative technology for wastewater treatment. Using microalgae and activated sludge as raw materials, a C-MFCs was established, and the effects of different nitrogen and phosphorus ratios in the influent on the electrochemical performance of C-MFCs and the removal effect of NH3-N, COD and TP were investigated. The results show that when N:P=3:1 and the external resistance is 1000 Ω, the removal rates of NH3-N, COD and TP are 72.48±1.94%, 81.26±4.4% and 65.62%±2.14%, respectively, and the highest chlorophyll a content is 108.82 mg/L. The maximum voltage and maximum power 92.94 mV and 234.01 mW/m2. The microbial community structure in the anode chamber was analyzed and the results are as follows: At N:P=3:1, the dominant bacteria at the genus level in the anode chamber were Klebsiella (32.12%) and Prevotella (14.45%). The number of OTUs in the anode chamber changes under different N:P conditions. It can be concluded that N:P affects the power generation capacity of C-MFCs and the removal of NH3-N, COD and TP. Overall,when N:P=3:1, the C-MFCs had the best power production capacity and the removal of NH3-N, COD and TP. Regulation of N:P in aquaculture wastewater is an effective way to improve performance of C-MFCs.</p>

Effects of Different Nitrogen Forms on Blackberry Fruit Quality.

To study the optimal form of nitrogen (N) application and to determine the best harvest date for blackberries, different N fertilizers were applied during the critical growth period of blackberry plants. The results showed that NH4+-N significantly improved the appearance of blackberry fruits, including their size, firmness, and color, and promoted the accumulation of soluble solids, sugars, anthocyanin, ellagic acid, and vitamin C (VC), while fruit treated with NO3--N accumulated more flavonoids and organic acids and had improved antioxidant capacity. In addition, the fruit size, firmness, and color brightness decreased with the harvest period. While the contents of sugars, anthocyanin, ellagic acid, flavonoids, and VC were higher in the early harvests and then decreased as the season progressed, the total antioxidant capacity and DPPH radical scavenging capacity increased. In all, application of NH4+-N is recommended, as it is more beneficial to fruit appearance, taste, and nutritional quality. Harvests in the early stage help to obtain a good fruit appearance, while harvests in the middle and later stages are more beneficial to fruit taste and quality. This study may help growers to determine the best fertilization scheme for blackberries and choose the appropriate harvest time according to their needs.

Effects of eutrophic water with ammonium chloride, urea, potassium dihydrogen phosphate and sodium-β-glycerophosphate on Myriophyllum verticillatum and epiphytic bacteria

With the rapid development of industry and agriculture, excessive nitrogen and phosphorus released into natural surface water have caused eutrophication. Applying submerged plants to manage eutrophic water has attracted widespread attention. However, there are limited studies on the effects of different nitrogen and phosphorus in the water environment on submerged plants and their epiphytic biofilm. Therefore, this paper investigated the effects of eutrophic water with ammonium chloride (IN), urea (ON), potassium dihydrogen phosphate (IP), and sodium-β-glycerophosphate (OP) on Myriophyllum verticillatum and epiphytic biofilms. The results showed that Myriophyllum verticillatum exhibited a good purification effect on the eutrophic water with inorganic phosphorus, the removal rates of IP were 68.0%, and the plants grew best in this condition. The fresh weight of the IN group and ON group increased by 12.24% and 7.12%, and the shoot length of the IN group and the ON group increased by 17.71% and 8.33%; the fresh weight of the IP group and OP group increased by 19.19% and 10.83%, the shoot length of the IP group and the OP group increased by 21.09% and 18.23%. In addition, the enzyme activities of superoxide dismutase, catalase, nitrate reductase, and acid phosphatase in plant leaves were significantly changed in eutrophic water with different forms of nitrogen and phosphorus. Finally, the analysis of the epiphytic bacteria showed that different forms of nitrogen and phosphorus nutrients could significantly alter the abundance and structure of microorganisms and microbial metabolism also had significant changes. This study provides a new theoretical basis for evaluating the removal of different forms of nitrogen and phosphorus by Myriophyllum verticillatum, and it also provides new insights for the subsequent engineering of epiphytic microorganisms to improve the capability of submerged plants to treat eutrophic water.

Fertigation under different irrigation and nitrogen levels modulates the growth, physiology, nitrogen and fruit productivity of greenhouse tomato

AbstractExperiments were conducted to evaluate the interactive effects of different nitrogen and irrigation levels in 2017 and 2018 (April–July) on greenhouse‐grown tomato considering irrigation water, growth, physiology and productivity parameters. A randomized block design with three replications and two factors, water (W1, 100% of the requirement; W2, 90%; W3, 70%) and nitrogen fertilizer (F1 225 kg/ha, F2 180 kg/ha), was established. The highest values of crop consumptive use (ET) were observed under the W1F1 treatment during both seasons (266 and 226 mm during 2017 and 2018, respectively). The highest values of stem and root biomass were also observed under W1F1 during both experimental seasons, followed by W1F2 and W2F1, without significant differences. Compared with W1F1, W1F2 and W2F1 had no significant difference, but other treatments decreased the photosynthesis rate and stomatal conductance significantly during both seasons. The highest irrigation level, W1, increased fruit yield under both nitrogen levels (W1F1 yielded 91 and 102 t ha−1, followed by W1F2, with 90 and 99 t ha−1 during 2017 and 2018, respectively). W2 increased fruit yield under higher nitrogen levels (F1) but decreased fruit yield under lower nitrogen levels (F2). W3 decreased yield drastically under both nitrogen levels. W3 significantly decreased water use efficiency and irrigation water use efficiency. The highest partial factor productivity values of 23% and 22% were obtained under W1F2 in 2017 and 2018, respectively, when compared with the control treatment. It was concluded that W1F2 could be the best strategy for improving greenhouse‐grown tomato productivity.

Effects of Nitrogen Form on Root Activity and Nitrogen Uptake Kinetics in Camellia oleifera Seedlings

This study investigated the effects of nitrogen form on root activity and nitrogen uptake kinetics of Camellia oleifera Abel. seedlings, providing a scientific basis for improving nitrogen use efficiency and scientific fertilization in C. oleifera production. Taking one-year-old C. oleifera cultivar ‘Xianglin 27’ seedlings as subjects, 8 mmol·L−1 of nitrogen in varied forms (NO3−:NH4+ = 0:0, 10:0, 7:3, 5:5, 3:7, 0:10) was applied in this study as the treatment conditions to investigate the effects of different nitrogen forms on root activity and nitrogen uptake kinetics in C. oleifera seedlings. Comparing the performance of nutrient solutions with different NO3−:NH4+ ratios, the results showed that a mixed nitrogen source improved the root activity of C. oleifera seedlings based on total absorption area, active absorption area, active absorption area ratio, specific surface area, and active specific surface area. When NO3−:NH4+ = 5:5, the total absorption area and active absorption area of the seedling roots reached the maximum. The results of uptake kinetic parameters showed that Vmax NH4+ > Vmax NO3− and Km NO3− > Km NH4+, indicating that the uptake potential of ammonium–nitrogen by C. oleifera seedlings is greater than that of nitrate–nitrogen. The conclusion was that compared to either ammonium– or nitrate–nitrogen, the mixed nitrogen source was better for promoting the root activity of C. oleifera seedlings, and the best nitrate/ammonium ratio was 5:5.

Effects of different nitrogen forms on photosynthesis characteristics and growth of poplar

Effects of different nitrogen forms on photosynthesis characteristics and growth of poplar

Effects of Different Nitrogen and Phosphorus Synergistic Fertilizer on Enzymes and Genes Related to Nitrogen Metabolism in Wheat

Effects of Different Nitrogen and Phosphorus Synergistic Fertilizer on Enzymes and Genes Related to Nitrogen Metabolism in Wheat

Tatlı Sorgum (Sorghum bicolor (L.) Moench var. saccharatum)’da Farklı Azot ve Potasyum Seviyelerinin Etanol Verimi ve Bazı Verim Özelliklerine Etkisi

Sweet sorghum, which is one of the bioethanol sources, has been increasing in importance in recent years. It is used in the production of bioethanol due to the high content of sugar in it. This study were carried out at Ege University, Faculty of Agriculture, Department of Field Crops, Izmir/Turkey on the experimental fields, two-factor coincidence plots were carried out in the form of a three-repeated potting experiment according to the trial pattern during the summer growth seasons of 2013 and 2014. Effects of different nitrogen (0, 50, 100, 150, 200 N/ha) and potassium (0, 50, 100, 150 kg K2O/ha) levels of on ethanol yield of sweet sorghum were investigated, in the experiment. N was applied in two equal doses in the experiment. K2O was mixed with soil and supplied as a single application. Some parameters were tested in the experiments such as stalk and juice yield, sugar content and theoretical ethanol yield. Results indicated that the effects of N and K treatments on all characteristics tested were significant. Application of the higher rates of N and K increased the ethanol yields compared to the control treatment. Based on these results the combination of N150-K100 were proved to be the best fertilizer level for ethanol yields of sweet sorghum grown under Mediterranean ecological conditions of Izmir.

Azot ve Potasyum Yönetimi ile Tatlı Sorgum (Sorghum bicolor (L.) Moench var. saccharatum)’da Verimlilik ve Kalitenin İyileştirilmesi

Sweet sorghum, which is one of the bioethanol sources, has been increasing in importance in recent years. It is used in the production of bioethanol due to the high content of sugar in it. This study were carried out at Ege University, Faculty of Agriculture, Department of Field Crops, Izmir/Turkey on the experimental fields, two-factor coincidence plots were carried out in the form of a three-repeated potting experiment according to the trial pattern during the summer growth seasons of 2013 and 2014. Effects of different nitrogen (0, 50, 100, 150, 200 N ha-1) and potassium (0, 50, 100, 150 kg K2O ha-1) levels of on ethanol yield of sweet sorghum were investigated, in the experiment. In the study, some traits were investigated such as plant height, dry matter yield, silage pH, crude protein content. The results of the experiment revealed significant effect of different N and K levels on growth, yield and some silage quality parameters. Increasing N and K levels increased plant height, dry matter yield, crude protein content and silage pH compared to the control (N0-K0) treatment. It is concluded that sweet sorghum crop performed better in N150-K100 level and hence recommended for further studies to authenticate higher forage yield and quality in the agroclimatic conditions of Izmir.

Accumulation of Wheat Phenolic Acids under Different Nitrogen Rates and Growing Environments.

The health benefits of whole wheat grains are partially attributed to their phenolic acid composition, especially that of trans-ferulic acid (TFA), which is a powerful natural antioxidant. Breeders and producers are becoming interested in wheat with enhanced health-promoting effects. This study investigated the effects of different nitrogen (N) application rates (0, 42, 84, 126, and 168 N kg ha−1) on the phenolic acid composition of three wheat varieties in four locations for two years. The results indicate that the different N rates did not affect the TFA concentration but that they significantly affected the concentrations of para-coumaric acid, sinapic acid, and cis-ferulic acid in the wheat grains. A statistical analysis suggested that the wheat phenolic acid composition was predominantly determined by wheat variety, though there existed some interaction effect between the wheat variety and environments. The TFA concentration of the variety Jimai 22 was generally higher (with a mean value of 726.04 µg/g) but was easily affected by the environment, while the TFA concentration of the variety Zhongmai 578 (with a mean value of 618.01 µg/g) was more stable across the different environments. The results also suggest that it is possible to develop new wheat varieties with high yield potential, good end-use properties, and enhanced nutraceutical values.

Deficit Irrigation at Pre-Anthesis Can Balance Wheat Yield and Water Use Efficiency under Future Climate Change in North China Plain.

Simple SummaryAdopting deficit irrigation (DI) to improve crop production and safeguard groundwater resources is of great importance in water scarce regions, e.g., the North China Plain (NCP). Under the background of global warming, it is worth investigating whether DI continues to play such a key role under future climate change scenarios. Thus, we studied the effect of DI on wheat yield and water use efficiency under future climate change scenarios. We found that moderate deficit irrigation (DI3, ≤0.4 PAWC at sowing to flowering stage) under the N3 (150 kg N ha−1) condition was identified as the optimum irrigation schedule for the study site under future climate change scenarios. However, the compensation effect of DI3 on yield and water use efficiency (WUE) became weak in the future. To conclude, in water scarce regions of NCP, DI remains an effective strategy to maintain higher yield and enhance water use under future climate scenarios.Background. Deficit irrigation (DI) is a feasible strategy to enhance crop WUE and also has significant compensation effects on yield. Previous studies have found that DI has great potential to maintain crop production as full irrigation (FI) does. Therefore, adopting DI to improve crop production and safeguard groundwater resources is of great importance in water scarce regions, e.g., the North China Plain (NCP). Under the background of global warming, it is worth investigating whether DI continues to play such a key role under future climate scenarios. Methods. We studied the response of winter wheat yield and WUE to different DI levels at pre-anthesis under two Shared Socioeconomic Pathways (SSPs) scenarios (SSP245 and SSP585) using the Agricultural Production Systems Simulator (APSIM) model driven by 21 general circulation models (GCMs) from the Coupled Model Inter-Comparison Project phase 6 (CMIP6). Additionally, we explored the effects of different nitrogen (N) fertilizer application rates on DI. Results. We found that simulated wheat yield would increase by 3.5–45.0%, with WUE increasing by 8.8–46.4% across all treatments under future climate change. Moderate deficit irrigation (DI3, ≤0.4 PAWC at the sowing to flowering stage) under the N3 (150 kg N ha−1) condition was identified as the optimum irrigation schedule for the study site under future climate change. However, compensation effects of DI3 on yield and WUE became weak in the future, which was mainly due to increased growing season rainfall projected by GCMs. In addition, we found that N fertilizer application could mitigate the effect of DI3. Conclusions. We highlight that in water scarce regions of NCP, DI remains an effective strategy to maintain higher yield and enhance water use under future climate scenarios. Results strongly suggest that moderate deficit irrigation under a 150 kg N ha−1 condition could mitigate the contradiction between production and water consumption and ensure food safety in the NCP.

Effect of nitrogen and carbon sources and salt stress on the bioactive components concentration in Scenedesmus obliquus

In Scenedesmus obliquus culture, the effects of different nitrogen and carbon sources and saline stress on total carotenoids, total proteins and total phenols contents were investigated. Microalgae in Allen & Arnon culture medium were cultivated, until reaching the stationary phase. Then, sodium nitrate or urea as nitrogen source and sodium acetate or glucose as carbon source, were incorporated. Additionally, sodium chloride was added for cause saline stress. Fourteen treatments were carried out, during 40 days. Differences in bioactive components concentration were observed for the different nitrogen and carbon sources from day 26. When 0.24 g/L of urea were used, 3 times more of total carotenoids were obtained than when sodium nitrate was used; while, with 3.68 g/L of glucose, 1.5 times more of total carotenoids were reached than with sodium acetate was used. Total proteins concentration was 1.9 times higher when 0.24 g/L of urea and 5.02 g/L of sodium acetate were utilized as nitrogen and carbon sources, respectively. With 31.00 g/L of urea 4 times more of total phenols were obtained than with sodium nitrate; while, 12 times more of total phenols were achieved with 3.68 g/L of glucose than with sodium acetate. Saline stress caused a reduction in the bioactive components of interest. The highest concentrations obtained were: 513.20±13.21mg β-carotene/gdwc, 7.25±0.34 mg BSA/gdwc, and 16.78±0.54 mg GAE/gdwc. Therefore, this study confirmed that Scenedesmus obliquus microalgae developed strategies to adapt to the new conditions caused by the nitrogen and carbon sources incorporation, causing changes in the concentration of bioactive components.

Effects of Different Nitrogen Forms and Competitive Treatments on the Growth and Antioxidant System of Wedelia trilobata and Wedelia chinensis Under High Nitrogen Concentrations.

Nitrogen (N) is one of the essential nutrients for plant growth. Appropriate application of N can improve the N use efficiency (NUE) and significantly promote plants’ growth. However, under N toxic conditions, the relationship between the growth and antioxidant system of invasive plants under different N forms and competitive treatments is not fully understood. Therefore, in this study, the performance of invasive species Wedelia trilobata and its native species Wedelia chinensis was evaluated under two sets of N forms and ratios, namely, NH4+-N(AN)/NO3–-N(NN) = 2:1 and NH4+-N(AN)/NO3–-N(NN) = 1:2 along with two intraspecific and interspecific competitions under without N and high N level of 15 g N⋅m–2 year–1, respectively. Data regarding the growth indices, antioxidant enzyme activities, including peroxidase (POD) and catalase (CAT), malondialdehyde (MDA), and proline contents were determined. Results showed that for competitive treatments, growth status was better for interspecific competition than intraspecific competition. The plant biomass of W. trilobata was significantly higher than that of W. chinensis. N significantly promoted the plants’ growth in terms of leaf area and biomass yield, and the antioxidant enzyme activities were significantly increased under a high N treatment than that of the control. Among N forms/ratios, ammonium N (AN)/nitrate N (NN) = 2:1 significantly enhanced the enzyme activity, particularly in W. trilobata. Furthermore, for intraspecific competition, MDA contents of W. trilobata were significantly decreased compared to that of W. chinensis. In conclusion, our results showed that W. trilobata adapted well under competitive conditions through better growth and antioxidant defense system.

Growth of Harmful Dinoflagellate Margalefidinium polykrikoides in Different Nutrient Concentrations

Margalefidinium polykrikoides blooms resulted in massive fish mortality in many countries around the world. The prevalence of booms is believed to be associated with the eutrophication of the coastal area. Therefore, this study aims to determine the effects of different nitrogen (N) and phosphorus (P) concentrations on the growth of M. polykrikoides. Experiments were conducted on M. polykrikoides isolated from the affected area by exposing the cell to various N and P ratio: seawater without the addition of N and P (SW), equal N:P ratio (NP), trial ratio of N and P (TR), F/2 medium (+NP), deficient N (–N), and deficient P (–P). The experiments were carried out in triplicates for 20 d in similar environmental conditions with the determination of density, specific growth rate, and cell size during the study period. Furthermore, nutrient concentrations nitrite+nitrate (NO2 –+NO3 –), phosphate (PO4 3–), and ammonia (NH4 +) were measured initially in the medium and both nutrients and chlorophyll were determined at the end of the experiment. The results revealed that M. polykrikoides grew in all the experiments, but the growth patterns differed between the treatments. The highest specific growth rate (0.1901 ± 0.017 d–1) with the highest cell density (1709 ± 68.21 cells mL–1) with a long chain of cells was observed in TR during the exponential phase. However, cell size was significantly smaller in SW compared to other nutrient conditions during the exponential phase. This study shows that M. polykrikoides a flexible species in nutrient uptake, thus allowing the species to survive in different nutrient conditions. The understanding of this bloom mechanism is important in monitoring and management of this harmful species, particularly in Sabah coastal waters.

The Effects of Different Fertilization Practices in Combination with the Use of PGPR on the Sugar and Amino Acid Content of Asparagus officinalis

The present study examined the effects of different nitrogen (NH4NO3) and potassium (KNO3) fertilization levels in combination with a nitrogen-fixing, plant growth-promoting rhizobacteria (PGPR) inoculation on the carbohydrate (CHO), amino acid content, and nutrient concentrations (N, P, K) in the spears and the root system of asparagus plants. No significant differences were indicated between the different fertilization treatments regarding N, P, and K in the leaves and roots of asparagus. The inoculation of the asparagus fields with PGPR, no matter the type of the inorganic fertilizer, resulted in increased CHO and amino acid content of the foliage and roots of asparagus. The highest CHO content and amino acid content were recorded in the treatment that combined PGPR inoculation along with KNO3 fertilizer, indicating that higher K applications acted synergistically with the added PGPR.