Low Phosphorus Content Research Articles

Phosphate recovery from urban sewage by the biofilm sequencing batch reactor process: Key factors in biofilm formation and related mechanisms

The biofilm sequencing batch reactor (BSBR) technique has been deployed in the laboratory to enrich phosphorus from simulated wastewater, but it is still not clear what its performance will be when real world sewage is used. In this work, the effluent from the multi-stage anoxic-oxic (AO) activated sludge process at a sewage plant was used as the feed water for a BSBR pilot system, which had three reactors operating at different levels of dissolved oxygen (DO). The phosphorus adsorption and release, the biofilm growth, and the extracellular polymeric substances (EPS) components and contents were examined. The microbial communities and the signaling molecules N-acyl-l-homoserine lactones (AHLs) were also analyzed. Gratifyingly, the BSBR process successfully processed the treated sewage, and the biofilm developed phosphorus accumulation capability within 40 days. After entering stable operation, the system concentrated phosphate from 2.59 ± 0.77 mg/L in the influent to as much as 81.64 mg/L in the recovery liquid. Sludge discharge had profound impacts on all aspects of BSBR, and it was carried out successfully when the phosphorus absorption capacity of the biofilm alone was comparable to that of the reactor containing the activated sludge. Shortly after the sludge discharge, the phosphate concentration of the recovery liquid surged from 50 to 140 mg/L, the biofilm thickness grew from 20.56 to 67.32 μm, and the diversity of the microbial population plunged. Sludge discharge stimulated Candidatus competibacter to produce a large amount of AHLs, which was key in culturing the biofilm. Among the AHLs, both C10-HSL and 3OC12-HSL were significantly positively correlated with EPS and the abundance of Candidatus competibacter. The current results demonstrated BSBR as a viable option to enrich phosphorus from real world sewage with low phosphorus content and fluctuating chemistry. The mechanistic explorations also provided theoretical guidance for cultivating phosphorus-accumulating biofilms.

The influence of poultry manure on the yield and crop structure of spring rapeseed

The research was carried out to identify the optimal dose of bedding bulk poultry manure on the influence of the crop structure and the yield of spring rape seeds of Lunedi variety. The work was carried out in 2022-2023 in the forest-steppe zone of the Nizhny Novgorod region. Poultry manure loose (GOST 31461-2012) was applied in doses of 4, 6 and 8 t/ha (control - without fertilizers). The experiment was conducted on light gray forest loamy soil with low humus content, neutral reaction and mobile forms of phosphorus and potassium. Statistically proven changes in the structure of rape yield were noticed on the manured variants: the increase in length of the fruit (pod) was 0.40–0.67 cm, in pod weight – 0.04–0.12 g, the number of pods per plant increased by 1.4–2.1 times, the number of seeds in a pod increased by 2.5–4.6 seeds, seed productivity of a single plant increased by 1.9–3.0 times, the weight of 1000 seeds exceeded by 0.66–0.94 g. The application of poultry manure on all variants revealed a reliable increase in the yield of above-ground phytomass and seeds, the increase in rape biomass was 6.03–8.70 t/ha (LSD05 = 1.30), seeds – 0.94–1.26 t/ha (LSD05 = 0.46). The maximum increase in the biomass of rapeseed and seeds (6.03 and 0.94 t/ha) was established in the variant with a manure dose of 4 t/ha, since with an increase in the manure dose (6 and 8 t/ha) in excess of the minimum increase by 1.42–2.67 t/ha of plant biomass and 0.22–0.32 t/ha of seeds. The obtained results suggest that the optimum dose of poultry manure application to spring rapeseed on light grey forest soil (Alfisol) is 4 t/ha.

Diversity of Macrophytes and Macroinvertebrates in Different Types of Standing Waters in the Drava Field

The diversity of macrophytes and macroinvertebrates in small standing waters of different origins and characteristics was investigated. This survey covered 19 ponds in the Drava field in northeastern Slovenia. The influence of the macrophytes on the macroinvertebrates was investigated and the main environmental factors that had the most significant influence on the composition of the two communities were identified. Sixty-seven taxa of macrophytes and seventy-three families of macroinvertebrates were identified. We found that a diverse macrophyte community has a positive effect on the macroinvertebrate community. In contrast, the dominance of a single macrophyte species has a strong negative influence on the richness of the macroinvertebrate community. The taxonomic richness and abundance of the macroinvertebrate community in the natural ponds was statistically significantly higher than that in artificial ponds. The significant differences in the environmental characteristics between the natural and artificial ponds, such as the macrophyte cover, conductivity, and riparian zone width, may account for these differences. Our study suggests that a greater diversity of macrophyte and macroinvertebrate communities in natural ponds is enabled by abundant but diverse macrophyte cover, low phosphorus content, and wide riparian zones, which require appropriate management of ponds and their catchments.

Nutritional risks and consequences of meat-only diets for dogs and cats

Suitable nutrition is one of the most significant issues that always needs to be considered in the health mainte-nance of living beings. One of the misconcep-tions of many societies is the exclusive feeding of meat to cats and dogs. Dogs and cats are carnivorous animals; more specifically, cats are strict or true carni-vores, while dogs are omnivores. Although cats are true carni-vores, an exclusive diet of meat will not cover their needs. Wholly meat-based diets might be rich in many nutri-ents and minerals, but they are poor in digesti-ble carbohydrates and fiber. Lack of carbohy-drates can cause gas-trointestinal problems and diarrhea. Also, due to hypovitaminosis A and D caused by such diets, skeletal diseases can be one of the seri-ous consequences. High dietary phosphate > 11.8 g in dry matter (DM) reduces renal phosphate reabsorption and increases vulnera-bility to chronic kidney disease. As phosphate excretion and reduction of calcium reabsorption continue, bone decom-position, symptoms of osteoporosis, and sec-ondary hyperparathy-roidism occur. In wholly meat-based canine di-ets, a lack of carbohy-drates compels the an-imal to use protein in the gluconeogenesis process to produce glu-cose. As a result, the body goes through pro-tein deficiency and its side effects. To main-tain digestive system health and prevent diar-rhea, the diet must in-clude soluble fiber. Al-so, the presence of car-bohydrates and fats is essential. Preserving the correct calcium-to-phosphorus ratio (Ca:P) can be solved by adding carbohydrates or using meats with a lower phosphorus content.

Genetic Variability Analysis for Yield and Its Attributing Traits in Rice (Oryza Sativa L.) under Phosphorus-sufficient and Deficient Field Conditions

Aim: The present study aims to identify phosphorus deficiency tolerant rice genotypes under both phosphorus-sufficient and deficient conditions. Materials and Methods: Two kinds of fields (high and low phosphorus content) were selected based on their soil phosphorus availability. Hundred diverse rice germplasm was collected and planted in an augmented design along with four local checks namely, Swarna sub-1, MTU 1153, MTU 7029 and Uttar Sona. The data was recorded for 14 traits and subjected to different types of variability analysis. Place and Season of Study: The experiment took place at instructional Farm of Uttar Banga Krishi Vishwavidyalaya, Cooch Behar, West Bengal, India during the Kharif season of 2021. Results: The variability analysis revealed that phosphorus uptake showed a high genotypic coefficient of variation (GCV) under phosphorus-deficient condition and high phenotypic coefficient of variation (PCV) under both conditions. Grain yield showed high GCV and PCV under both the phosphorus conditions. Heritability was moderate whereas high Genetic advance as percentage of mean was observed under both the conditions for both phosphorus uptake and grain yield. Strong positive correlations were observed between days to flowering and various yield-related traits under both the conditions. Positive correlation was observed between phosphorus uptake and grain yield under phosphorus-sufficient condition, but a weaker correlation under phosphorus-deficient condition.

Highly stable removal of low concentration phosphorus by mechanically activated FeCO3: In situ synergistic mechanisms

Excess phosphorus (P) in surface water poses a serious threat to ecological safety. However, current methods for effectively removing low concentrations of phosphorus are complicated and expensive. Herein, we used one-step mechanical activation to enhance the release of alkalinity from carbonates and to stimulate ferrous activity in situ, thus achieving efficient and stable removal of phosphorus at low concentrations. The resultant activated FeCO3 was demonstrated to be a high-performance material, which can remove more than 92 % of the actual low concentration of phosphorus pollution within 30 min, and the concentration of the effluent steadily met the requirements of Chinese Class I environmental quality standards for surface water (0.02 mg/L). In addition, mechanistic investigation showed that mechanical activation significantly enhanced the reactivity and phosphorus removal performance of MgCO3. Moreover, one-step mechanical activation simultaneously stimulates the release of alkaline and ferrous ionic groups from iron-rich FeCO3, which can produce highly active trivalent iron oxides in situ, leading to efficient and stable phosphorus removal at low concentrations. The present work provides a new insight and direction for developing high-performance materials to remediate low concentration phosphorus polluted waters.

Purification process and mechanism analysis of low-concentration phosphorus wastewater with novel electrodeposition - biochar filter bed

Phosphate‑phosphorus (PO43−-P) is a non-renewable resource. Rapid agricultural activities and inefficient use of phosphate fertilizers contribute to the contamination of natural water resources due to PO43−-P accumulation. PO43−-P recovery in natural water with a low PO43−-P concentration, is conducive to the sustainable utilization of phosphate. Electrodeposition using Ca2+ to recover PO43−-P in natural water has great potential. However, the limitations of low-concentration PO43−-P recovery need to be addressed. This study designed a novel electrodeposition-biochar filter bed (E-BFB) to investigate the removal and recovery ability of PO43−-P at low concentrations. Efficient removal and recovery of PO43−-P was achieved through electrodeposition, biochar adsorption, and accumulation by microorganisms. Effects of different parameters on the performance of E-BFB for PO43−-P removal were studied, including influent PO43−-P concentration, voltage, and electrode spacing. Results showed that 69.4 % PO43−-P was removed when the influent PO43−-P concentration was 0.8 mg/L by E-BFB, as the average removal rate in the biochar filter bed (BFB) was only 11 %. The PO43−-P recovery rate of cathodic electrodeposition was as high as 37.22 %, accounting for 57 % of the total PO43−-P removal amount. The PO43−-P electrodeposition precipitate mainly was amorphous calcium phosphate (ACP) through analysis. 16S rRNA results demonstrated that electrodeposition altered the microbial communities. At the genus level, such as Acinetobacter (26.6 %), Acidocella (11.7 %), and Pelomonas (7.2 %) were promoted in the biochar substrate of E-BFB. Overall, this novel E-BFB can remove PO43−-P at low concentrations effectively. It has great application prospects in the treatment of surface water by biofilters or constructed wetlands.

Comparative study of flame retardancy in polyimine vitrimers and composites: Evaluating additive and reactive flame retardants acting via gas-, solid-, and combined-phase mechanisms

We developed flame retarded polyimine type vitrimers and carbon fibre reinforced composites using two additive and a reactive flame retardant containing phosphorus: ammonium polyphosphate (APP), resorcinol bis(diphenyl phosphate) (RDP); and N,N',N’’-tris(2-aminoethyl)-phosphoric acid triamide (TEDAP). We characterised the vitrimer matrix materials by differential scanning calorimetry (DSC), thermal analysis (TGA), limiting oxygen index (LOI), UL-94 test and mass loss calorimetry (MLC), while the vitrimer composites by LOI, UL-94 test, MLC and dynamic mechanical analysis (DMA). We compared the performance of the vitrimer systems to a benchmark pentaerythritol-based aliphatic epoxy resin system (PER). The vitrimer reference had higher thermal stability but lower fire performance than the PER aliphatic reference epoxy. At lower phosphorus content, the vitrimer systems exhibited a melting above their vitrimer transition temperature, which negatively affected their LOI and UL-94 results. From 2% phosphorus content, rapid charring and extinguishing of vitrimers prevented the softening and deforming. The superior performance of these same flame retardants in vitrimer systems could be attributed to the high nitrogen content of imine-based vitrimers in combination with phosphorus flame retardants, exploiting nitrogen-phosphorus synergism. In both matrices, flame retardants with solid phase action lead to better fire performance, while in composites, the lowest peak heat release rates (152 kW/m2 in vitrimer composite) were achieved with RDP acting predominantly in the gas phase, as carbon fibres hindered the intumescent phenomenon.

Analysis of Effectiveness of Bottom Stirring after the Modernization on Basic Oxygen Furnace in HBIS Serbia Group

The significant modernization effort in the steel shop at HBIS Group Serbia is the introduction of a Basic Oxygen Furnace, which features bottom stirring with argon and nitrogen, along with the capability for slag splashing with nitrogen through the lance tip after steel tapping from the converter. Implementing this new technology presented a challenge, as it was our first encounter with such advancements. The primary objectives of this modernization were to achieve a lower dissolved oxygen content in steel while reaching the targeted carbon level at the end of the blowing process. This aims to optimize the steel's oxidation degree [%C] [%O], reduce the use of Al as a deoxidizer, increase yield, and achieve a low phosphorus content in steel at the end of blowing. Additionally, it aimed to increase the lining's lifetime through slag splashing and decrease the refractory mass consumption needed for lining repairs. This analysis covers a 7-month period since the start of the campaign with the new refractory lining, based on research conducted on 3,150 heats. Our examination of the process led us to conclude that while certain parameters met our expectations, some results did not reach the anticipated level.

Limited response to phosphorus fertilization in native South American grasslands across a productivity gradient despite low phosphorus concentrations in grassland herbage

Limited response to phosphorus fertilization in native South American grasslands across a productivity gradient despite low phosphorus concentrations in grassland herbage

Nutrient Variations and Their Use Efficiency of Pinus massoniana Seedling Tissues in Response to Low Phosphorus Conditions

Investigating the mechanisms by which plants adapt to low phosphorus content in ecosystems is crucial for nutrient dynamics division. Our study investigated the growth adaptation strategies of Pinus massoniana seedlings to low phosphorus conditions, including nutrient and non-structural carbohydrate (NSC) allocation, nutrient stoichiometry, and changes in nutrient resorption efficiency along a fact-based gradient. Our results showed that the total biomass and aboveground biomass proportion increased with substrate phosphorus content, reaching maximum biomass in the one-time phosphorus treatment. The nutrient concentration of components remained relatively stable, with the allocating preference to roots and needles under low phosphorus conditions. NSC was allocated as starch in fine roots and as soluble sugar in needles. Seedlings did not show signs of phosphorus limitation, even in the non-phosphorus group. The nitrogen resorption efficiency to phosphorus resorption efficiency ratio (NRE: PRE) of needles significantly varied between the high and low phosphorus treatments. In response to phosphorus deficiency, seedlings demonstrated homeostatic adjustments to maintain the relative stability of nutrient concentration. Fine roots and needles were prioritized to ensure nutrient uptake and photosynthetic product production. Additionally, it was necessary to differentiate the indicative function of nitrogen/phosphorus for various species and components, and NRE: PRE potentially provides a sensitive indicator of nutrient limitation status.

The interplay between historical land‐use and the distribution of Helichrysum shrubs in an African‐protected grassland

AbstractHuman land use can have lasting impacts on landscape characteristic, yet there remains a lack of information on how former land use affects plant communities in protected African grasslands. In this study, we investigated how land uses prior to the creation of Kitulo National Park, Tanzania, shaped the presence and abundance of the native shrub, Helichrysum species. We evaluated both plant species composition and soil properties across the park by dividing our sample into three different zones of historical land use based on participatory mapping. We divided the park into three former land uses: (1) livestock grazed and cultivated; (2) grazed only and (3) wild grazing with limited human impact. We observed that former grazed cultivated land use had five times higher Helichrysum abundance than former ‘wild’ land use. Soil pH, magnesium and phosphorus levels varied significantly across zones of historical land use but not between sites with and without Helichrysum species. Helichrysum splendidum was more abundant in soils with low soil phosphorus and magnesium concentrations. Our study demonstrates that historic grazing and cropping land uses through changes in soil nutrient properties can explain current Helichrysum species spread in protected areas. As such, conservation management plans would benefit from integrating mapping of former land uses to target interventions for problematic encroaching shrubs.

Effect of Egg-White Protein Alone or Combined With Niacin on Nutritional Status, and Phosphorus Control in Maintenance Hemodialysis Patients: A Randomized Controlled Trial

BackgroundNiacin is reported to decrease phosphorus concentration in Maintenance Hemodialysis (MHD) patients. Egg white is one of the main substitutable proteins in MHD patients due to its low phosphorus content. Therefore, we aimed to evaluate the effects of combined egg white and niacin supplementation on dialysis patients' serum phosphorus and nutritional biomarkers. MethodsIn this randomized controlled clinical trial, 98 patients on MHD were randomly allocated to four groups for eight weeks: 24 g egg white (n=25), 600 g niacin daily (n=24), egg white combined with niacin (n=24), and control (n=24). Calcium, phosphorus, fibroblast growth factor-23, and other nutritional markers were assessed. ResultsThere was a significant difference among the groups only in phosphorus at the end of the trial, which was significantly lower in the niacin group (4.38+0.812 mg/dl) than in both the egg white (5.07+0.49 mg/dl) and egg white with niacin supplementation (5.41+0.662 mg/dl) groups. In this regard, albumin increased in egg white and egg white with niacin supplementation, while albumin did not change significantly in the niacin group. Urea reduction ratio and Kt/V rose only in the egg-white group, while aspartate aminotransferase increased only in the niacin and control groups. ConclusionNiacin decreases serum phosphorus concentration more than egg-white protein or a combined intervention. Egg white protein supplementation has beneficial effects on some nutritional statuses other than phosphorus control without the side effects of niacin.

Phosphorus HotSpots in Crop Plants Production on the Farm—Mitigating Critical Factors

Phosphorus resources, both in phosphate rocks and in the soil, are limited. However, effective food production is not possible without the use of P fertilizers. Recognizing and eliminating or at least ameliorating factors (hot spots) that interfere with the uptake and use of phosphorus (P) by crop plants is of key importance for effective use of both P and nitrogen (N) on the farm. Plants have developed many adaptation mechanisms to their environment, i.e., soil low in available phosphorus. The most important ones include the secretion of organic compounds into the rhizosphere and the association of plant roots with microorganisms. A classic example is mycorrhiza. These mechanisms can be used by the farmer to sequentially select plants in the crop rotation. The uptake of inorganic P (Pi) by plants from the soil is reduced by environmental (temperature and water) and soil factors (low content of available phosphorus, soil acidity, soil compaction). These factors are responsible for the growth and size of the root system. Mitigating these negative effects improves the efficiency of phosphorus uptake from the soil. The second group of critical factors, limiting both root growth and availability of phosphorus, can be effectively controlled using simple measures (for example, lime). Knowing this, the farmer must first control the level of soil fertility in the plant’s effective rooting zone and not only in the topsoil. Secondly, the farmer must multiply the productivity of applied mineral fertilizers used through targeted recycling: crop rotation, crop residues, and manure.

Bacterial community changes in the presence of AMF in the context of maize with low phosphorus content

PurposeArbuscular mycorrhizal fungi (AMF) perform an ancestral and essential association with plant roots, where plants provide carbohydrates and lipids, and the fungi respond by translocating water and nutrients to the roots through the hyphae. There is a need to investigate the microbial community associated with the rhizosphere of mycorrhizal plants in response to the multiple benefits (e.g., improved nutrition and stress resistance) provided by the association. In this work, we analyzed the bacterial communities associated with the rhizosphere of plants and their response to mycorrhizae in low P conditions.MethodsFor this purpose, inoculated and non-inoculated B73 corn plants were grown with a consortium of mycorrhizal fungi under low phosphorus conditions. Mycorrhiza response in B73 and the interaction with rhizosphere microbiome were characterized by sequencing the bacterial 16S rRNA gene.ResultsInoculated plants showed increased greater growth in leaf and root parameters in low P conditions. Bacterial microbiome showed changes in beta diversity and some OUTs significantly regulated by AMF presence.ConclusionThese data confirm the importance of mycorrhizae in phosphorus stress and rhizosphere community changes as a possible mechanism to improve plant growth.

Study of the Sustainability of Ecological and Chemical Indicators of Soils in Organic Farming

Organic farming is often seen as a sustainable alternative to intensive agricultural systems. The studies conducted in this direction analyze various factors, as well as their assemblies, and show contradictory results. In order to assess the impact of the organic method of soil cultivation on the stable composition of the most important mineral and organic substances in the production process, the organic agriculture procedure was implemented with an agrochemical analysis for 12 years. The content of mobile phosphorus, exchangeable potassium, and humus in the soil was determined. An elemental analysis of soil samples was conducted for a more in-depth analysis of its composition. It was established that the soils of the farm contained a sufficient amount of exchangeable potassium and humus. The content of these components remained stable during the study period. It was discovered that the soils of the farm have a low content of mobile phosphorus, which also remained stable during the study period. In the studied farm, the applied farming technologies contribute to the stable content of the main nutrient components of the soil. But to correct the content of mobile forms of phosphorus, additional agrotechnical measures are required.

Long-term phosphorus fertilization reveals the phosphorus limitation shaping the soil micro-food web stability in the Loess Plateau.

The intricate decomposition pathways within soil micro-food webs are vital for cycling soil organic carbon and nutrients, influencing the quality, productivity, and sustainability of soil systems. However, the impact of diverse phosphorus addition on these organic decomposition pathways still needs to be explored. In an 8-year experiment, phosphorus (P) fertilizer was added at varying levels (0 kg ha-1, CK; 60 kg ha-1, P60; 120 kg ha-1, P120; and 180 kg ha-1, P180), to investigate the response of the soil micro-food web. The results revealed a significant effect of phosphorus addition on soil microorganisms and nematodes, with P60 exerting a greater influence than other treatments. At P60, the Shannon index of nematodes and fungi surpassed other treatments, indicating higher diversity, while the Shannon index of bacteria was lower. The Chao1 index of bacteria and fungi at P60 was higher, contrasting with the lower index for nematodes. Metabolic footprints of bacterivores and omnivores-predators (BFMF and OPMF) were higher at P60, while metabolic footprints of fungivores and plant parasites (FFMF and PPMF) were lower, signifying altered energy flow. Functional metabolic footprints and energy flow analysis unveiled a stable soil micro-food web structure at P60, with enhanced energy conversion efficiency. Network analysis illustrated positive correlations between fungi, fungivorous nematodes (FF), and omnivorous-predatory nematodes (OP) at P60, while P120 and P180 showed positive correlations among bacteria, bacterivorous nematodes (BF), and OP. Path analysis underscored the higher contribution rate of BF-C, FF-C, and OP-C to soil organic carbon at P60 compared with P120 and P180. These findings suggest that nutrient interactions between fungi and nematodes regulate soil micro-food web decomposition under low phosphorus concentrations. In contrast, interactions between bacteria and nematodes dominate at high phosphorus concentrations. The study indicates that adding phosphorus has nuanced bottom-up effects, intricately shaping the structure and activity of the pathways and underscoring the need for a comprehensive understanding of nutrient dynamics in soil ecosystems.

ВИРОЩУВАННЯ СОРГО ЗЕРНОВОГО НА КИСЛИХ ГРУНТАХ В УМОВАХ ЗАКАРПАТСЬКОЇ ОБЛАСТІ

The work aims to conduct production field research to determine the potential yield level of grain sorghum on acidic soils, as well as work out the generally accepted basic elements of cultivation technology with its subsequent cultivation in the Zakarpattia region. Materials and methods. In 2023, the production range for growing grain sorghum at Karpatiagroproduct LLC was located in the lowland zone of Uzhgorod district, Zakarpattia region. The article describes agrotechnical operations related to soil cultivation, application of fertilizers and plant protection products that were used in the farm, the main of which was the application of mineral fertilizer diammonium phosphate (NP 18:46) at the rate of 160 kg during sowing. The sowing rate was 165,000 seeds per hectare with a row width of 37 sm. Results. Sorghum is not picky about soils, so it can grow on both clay and sandy soils. The landfill where sorghum was grown is characterized by a low content of mobile phosphorus (6.33 mg/kg), a very low content of total nitrogen (N-NO3- + N-NH4+ – 8.92 mg/kg). According to the degree of acidity, the soil belongs to a very acidic soil (the hydrogen index of the saline extract of the soil is 4.08). In the economic conditions of 2023, the yield of sorghum grain hybrid Iceberg was 4.4 t/ha, which is 1.0 t/ha more than the average yield of sorghum in Ukraine over the past 10 years. Taking into account the genetic potential of this crop and the sufficient level of moisture supply of the territory, the level of the sorghum harvest should be twice as large. Because sorghum is not recommended to be grown on acidic, waterlogged soils with a close occurrence of groundwater, the underachieved level of the harvest to some extent may be related to this. In addition, the low content of mobile phosphorus and very low content of available nitrogen, which is characteristic of acidic clay soils, to some extent negatively affected the processes of crop yield formation. Conclusions. The obtained sorghum yield at Karpatiagroproduct LLC - 4.4 t/ha is lower than the average yield in Italy, by 2.6 t/ha, and in France - by 0.6 t/ha. However, it was in the territory of Ukraine that the record yield of sorghum in the world was obtained - 14.43 t/ha, which testifies to the high potential of grain sorghum and the unlimited potential of scientific and industrial research to reveal the genetic expression of this crop. Keywords: grain sorghum, yield, soil pH, «Iceberg» hybrid, agricultural technology.

Influence of intensive potato cultivation on the properties of red ferralitic soils in the “Amistad Cubano-Búlgara” CPA

The agricultural sector in Cuba plays an important role for the economy, with a contribution to GDP of around 20%. However, approximately 67% of agricultural land has some agroproductive limiting factors. This situation is aggravated by the implementation of inadequate farming systems and by the lack of knowledge of the measures to be adopted based on the limiting agro-productive factors of the agroecosystems. In the research, the study of the properties of Red Ferralitic soils (Order Oxisol) is carried out in the agroecosystems intensively dedicated to the cultivation of potatoes (Solanum tuberosum L.), in the CPA “Amistad Cubano-Búlgara”, one of the most important production entity in the Mayabeque province. As a result of the research, evident negative impacts are observed on the quality of the soil due to its intensive use and monoculture. This has caused soil degradation, highlighting the low content of organic matter, potassium and phosphorus, along with the reduced cation exchange capacity. Likewise, compaction and poor drainage problems were identified, which negatively affects the development of the crop. Sustainable management measures and the implementation of agroecological practices are proposed to improve the sustainability of food production in the region and counteract the negative effects of intensive agriculture.

Physiological and Biochemical State of Green Microalgae (Chlorophyta) under Different Nutrients' Content in the Cultural Medium

The physiological and biochemical state of green microalgae <i>Tetradesmus dimorphus</i> (Turpin) M.J. Wynne and <i>Desmodesmus brasiliensis</i> (Bohlin) E. Hegew at different growth phases depending on the nutrients' content in the cultural medium was investigated. Maximal cell numbers, specific growth rate and biomass increment in <i>T. dimorphus</i> were recorded at the exponential stage under high concentrations of nitrate nitrogen and phosphorus of phosphates, and in <i>D. brasiliensis</i> - under low. The increase of the cells' division frequency resulted in their lesser size and increase of length/width ratio. Maximal content of lipids and carbohydrates in the cells of <i>T. dimorphus </i>was recorded at the end of the exponential stage over cultivation in the medium with low initial concentrations of nitrate nitrogen and phosphorus of phosphates, and in <i>D. brasiliensis</i> -with high content. At this is no difference in the proteins' content in their cells was revealed.