Constant Nutrient Research Articles

Determination of the Influence of a Constant Nutrient Supply on Wet Yield, Dry Yield and Average Weight ofMusca domesticaLarvae Maintained at Different Densities

A study was done to compare the production efficiency, in terms of total wet and dry larval yield and average weight of larvae of Musca domestica, reared at a constant temperature and nutrient supply but with increased larval density per unit of feed supplied. Wet weight yield increased with increased stocking density at a rate of 16.74 g/0.1 g eggs added while dry weight yields increased at a rate of 2.75 g/0.1 g eggs added. At the maximum rate tested, (6.318 eggs/g wet feed) no decrease in rate was observed and it is therefore concluded that the maximum wet and dry yields will be obtained at rates even higher than 6.318 eggs/g wet feed. Average larval weight was significantly influenced by density with the maximum observed at 3.159 eggs/g wet feed with a constant decrease up to 5.002 eggs/g wet feed and no significant differences observed at higher densities. It was thus concluded that, for the purpose of mass rearing larvae of M. domestica for biomass conversion, larval density as expressed per unit of nutrient supplied could be increased to levels of above 6.318 eggs/g wet feed but, for the production of breeding stock densities, should be maintained at levels of 5.002 eggs/g wet feed or lower.

Invited Review: The preterm pig as a model in pediatric gastroenterology

At birth, the newborn mammal undergoes a transition from a sterile uterine environment with a constant nutrient supply, to a microbe-rich environment with intermittent oral intake of complex milk nutrients via the gastrointestinal tract (GIT). These functional challenges partly explain the relatively high morbidity and mortality of neonates. Preterm birth interrupts prenatal organ maturation, including that of the GIT, and increases disease risk. Exemplary is necrotizing enterocolitis (NEC), which is associated closely with GIT immaturity, enteral feeding, and bacterial colonization. Infants with NEC may require resection of the necrotic parts of the intestine, leading to short bowel syndrome (SBS), characterized by reduced digestive capacity, fluid loss, and dependency on parenteral nutrition. This review presents the preterm pig as a translational model in pediatric gastroenterology that has provided new insights into important pediatric diseases such as NEC and SBS. We describe protocols for delivery, care, and handling of preterm pigs, and show how the immature GIT responds to delivery method and different nutritional and therapeutic interventions. The preterm pig may also provide a sensitive model for postnatal adaptation of weak term piglets showing high mortality. Attributes of the preterm pig model include close similarities with preterm infants in body size, organ development, and many clinical features, thereby providing a translational advantage relative to rodent models of GIT immaturity. On the other hand, the need for a sow surgical facility, a piglet intensive care unit, and clinically trained personnel may limit widespread use of preterm pigs. Studies on organ adaptation in preterm pigs help to identify the physiological basis of neonatal survival for hypersensitive newborns and aid in defining the optimal diet and rearing conditions during the critical neonatal period.

Effects of experimental eutrophization on zooplankton community

AIMS: The present study evaluated the role that increased nutrient concentrations play on zooplankton community, by employing an experimental laboratory approach. METHODS: Experiments were conducted in the laboratory, where three trophic state conditions were simulated, namely, mesotrophic, eutrophic and hypereutrophic. Each treatment was replicated three times and individuals of Brachionus urceolaris (10 individuals), Hexarthra mira (5) (Rotifera), Latonopsis sp. (10), Moina minuta (10) (Cladocera) and Thermocyclops sp. (5) (Copepoda) were introduced to each replicate. On the first experiment day, and at 7-day intervals for a 14-day period (totaling three evaluations), all water content was collected from each container and filtered to determine the densities of each zooplankton species. Two-way MANOVA and one-way ANOVA designs were used to determine zooplankton density fluctuations among treatments and throughout the study period. Further, Generalized Linear Models (GLMs) were employed to assess how environmental factors affected zooplankton numbers. Phytoplankton composition was also determined in the beginning and in the end of the experiment. RESULTS: B. urceolaris and copepod nauplii, which are typical of eutrophic environments, showed higher densities on the eutrophic and hypereutrophic treatments. Furthermore, cyanobacteria such as Aphanothece sp. and Merismopedia sp. were recorded on the eutrophic and hypereutrophic treatments, respectively. CONCLUSIONS: Similarly to what is frequently observed in the wild, the eutrophic treatment showed higher densities of particular zooplankton species which are known to temporarily benefit from an increase in trophic concentrations. Positive or negative responses from zooplankton dynamics (but also phytoplankton species), provide an important bioindicator framework. Furthermore, results of the present study outline the need for implementing recovery measures on aquatic environments subject to constant nutrient inputs.

Decomposition Dynamics and Nutrient Release Pattern from Leaf Litters of Five Commonly Occurring Homegarden Tree Species in Mizoram, India

Leaf litter decomposition and nutrient release patterns from five common multipurpose tree species—viz., Artocarpus heterophyllus, Mangifera indica, Areca catechu, Citrus sp., and Tamarindus indica, found in homegardens of Mizoram—were evaluated using a litter bag technique. The result of the study indicates a varying pattern of decomposition and nutrient release (N&P) among the species. Citrus sp. and T. indica were found to be the most labile species with comparatively much higher decay constant and faster nutrient release. Initial nitrogen concentration, lignin content, and lignin/N ratio of foliage litter showed significantly higher (p < .01) correlation with the decay coefficient and were found to be the important determinants in the decay process. The initial slow release and immobilization of N in A. heterophyllus and M. indica leaf litter reflect their potential as a source of nitrogen storage and effective mulching material. While litter from T. indica and Citrus sp. can provide the short-term nutrient need, foliage for the other three species may supply the long-term nutrient requirement for the understory crops in such agroforestry systems.

Sensitivity analysis of a pulse nutrient addition technique for estimating nutrient uptake in large streams

The constant nutrient addition technique has been used extensively to measure nutrient uptake in streams. However, this technique is impractical for large streams, and the pulse nutrient addition (PNA) has been suggested as an alternative. We developed a computer model to simulate Monod kinetics nutrient uptake in large rivers and used this model to evaluate the sensitivity of the PNA technique. We parameterize our model using the average hydrogeomorphological estimates from a pulse release study of ammonium in the Snake River, WY, and used this study to demonstrate how data from a field experiment can be effectively analyzed using a simulation model. To evaluate the sensitivity of the PNA technique, we manipulated the hydrogeomorphology and uptake kinetics of our stream model, simulated a pulse ammonium addition, and measured the downstream response in our model as if it were a field experiment, while ammonium areal uptake at ambient concentration was kept unchanged in the model. Ammonium uptake estimates by the PNA technique were different from the uptake in our model and these differences were nonrandom. The difference was greatest when velocity was high and there was little solute spread, either in the water column or from exchange with transient storage. The difference was also high when the half saturation coefficient for uptake was low. Our estimates of ammonium uptake under the assumption of Monod kinetics were higher than those under the assumption of first‐order kinetics based on direct calculation from the experimental data.

On the “strict homeostasis” assumption in ecological stoichiometry

Multiple elements including carbon (C), nitrogen (N) and phosphorus (P) are required for organismal growth, reproduction, and maintenance. Newly emerging mathematical models linking population dynamics with stoichiometric relationships among these key elements improve historic trophic interaction models and resolve some existing paradoxes. The degree to which organisms maintain a constant chemical composition in the face of variations in the chemical composition and availability of their environmental resources is referred to as “stoichiometric homeostasis”. Most of these models so far have assumed constant nutrient contents in heterotrophs, called “strict homeostasis”, and varied nutrient contents in autotrophs, called “non-homeostasis”, due to the fact that the stoichiometric variability of heterotrophs is often much less than that of autotrophs. Our study suggests that the “strict homeostasis” assumption is reasonable when the stoichiometric variability of herbivores is less than a threshold. This threshold is independent of algal stoichiometric variability, thus the above historic reasoning for strict homeostasis in heterotrophs is not convincing. We find that the “strict homeostasis” assumption seems valid for many herbivores except for herbivores with small mortality rates. The results are nearly same in both one-nutrient and two-nutrient models, and robust to perturbation of parameter values and environmental nutrient status. Finally, the two-nutrient model shows that herbivore's survival needs higher variation in the more potentially limiting of the two elements.

Organic Fertilization and Its Effect on Development of Sweet Pepper Transplants

Organically grown greenhouse sweet pepper crops, as is the case with most year-around greenhouse crops, rely on pre-grown transplants. Production of adequately balanced (source and sink strength potential) healthy organic sweet pepper transplants is a challenge and is often related to early and total harvested yields. Liquid and/or solid organic fertilizers for greenhouse sweet pepper transplants were compared with a conventional liquid fertilizer. Transplants were grown under greenhouse conditions and inoculated, or not, with a beneficial microbial agent, Trichoderma harzianum Rifai, strain KRL-AG2 (Rootshield®). Medium respiration (CO2 efflux) and fluorescein diacetate (FDA) hydrolysis analysis showed a higher microbial activity in the liquid organic fertilizer treatment. Higher microbial activity was observed after 10 weeks than at 5 weeks after transplanting. Transplant development was greater in the liquid conventional fertilizer treatment compared with the two organic treatments. Transplants that received liquid organic fertilizer had greater development compared with transplants that only received water in addition to the initial solid fertilizer. Organic amendment mineralization did not completely fulfill transplant nutrient requirement compared with conventional transplants. Solid fertilization in the growing medium affected plant growth during the first 5 weeks but not after 10 weeks after transplanting. Solid and liquid organic fertilizers at a higher concentration should be provided to reach a similar transplant development because conventional seedlings or other slow-release sources of solid amendments should be added to the growing medium to keep an adequate and constant nutrient release. Providing a beneficial agent to the organic growing medium increased its biological activity but had no effect on seedling growth during this study. Solid organic fertilization (1600 mL·m−3 of shrimp meal with 50 mL·m−3 of kelp meal) combined with an organic liquid fertilization should be used in combination with inoculation with T. harzianum to obtain high-quality organic sweet pepper transplants.

The use of liposomes to differentiate between the effects of nickel accumulation and altered food quality in Daphnia magna exposed to dietary nickel

A potential drawback of traditional dietary metal toxicity studies is that it is difficult to distinguish between the direct toxicity of the metal and indirect effects caused by altered concentrations of essential nutrients in the metal-contaminated diet. In previous studies it has become clear that this can hamper the study of the real impact of dietary metal exposure and also complicates the analysis of the mechanisms of dietary metal toxicity in filter-feeding freshwater invertebrates like Daphnia magna. This problem has been partly circumvented by the production of liposomes, since these vectors are invulnerable to metal-induced food quality shifts and as such can be applied to study the mechanisms of dietary metal toxicity without the confounding effect of nutritional quality shifts. The aim of current study was to evaluate if there is relevance for dietary Ni toxicity under natural exposures, i.e., when D. magna is exposed to dietary Ni via living algae, and secondly, to quantify how nutritional quality shifts contribute to the toxic effects that are observed when algae are used as contaminated food vectors. For this aim, liposomes were prepared by the hydration of phosphatidylcholine in media containing 0 (control), 10, 50, 100 and 500mgNi/L. The liposome particles were then mixed with uncontaminated green algae in a 1/10 ratio (on a dry wt basis) to make up diets with constant nutrient quality and varying Ni contents (i.e., 1.2μgNi/gdry wt in the control and 18.7, 140.3, 165.0 and 501.6μgNi/gdry wt in the Ni-contaminated diet, respectively). A second food type was prepared on the basis of a 1/10 mixture (on a dry weight basis) of control liposomes and Ni-contaminated algae, representing a diet that differed in Ni content (i.e., 1.2, 26.8, 84.7, 262.3 and 742.7μgNi/gdry wt) and concentrations of essential nutrients (in terms of P and omega 3 poly-unsaturated fatty acids like eicosapentaenoic acid and α-linolenic acid). Both diets were then simultaneously fed to D. magna during a 21-day chronic bioassay, using reproduction, growth, survival, ingestion rate and Ni bioaccumulation as endpoints. Ni delivered by liposomes caused a significant inhibition of reproduction and growth when the metal accumulated to minimum levels of 11.9 and 20.0μgNi/gdry wt after 7 and 14 days, respectively. Using algae as Ni vector, similar effects of dietary Ni exposure occurred when algae had been pre-exposed to concentrations of at least 133μg/L of bioavailable Ni (i.e., Ni2+), which is similar to the reproductive EC50 of waterborne Ni exposure for D. magna (115μgNi2+/L). While this may have some consequences for predicting chronic Ni toxicity in this range of Ni concentrations with the biotic ligand model – which could be further improved by including the dietary toxicity pathway in this model, the occurrence of such high concentrations in the field is very rare. Hence, there seems to be very little environmental relevance for dietary Ni toxicity to D. magna. Finally, besides the direct effects of Ni there was no evidence that nutritional quality shifts could have affected daphnids’ growth, but it is very likely that the impairment of reproduction at toxic exposure levels of Ni was also partly the result of reduced fatty acid levels.

Decomposer community complexity affects plant competition in a model early successional grassland community

The effects of a simple decomposer community, consisting of collembola, enchytraeids and earthworms on the performance of plants in a model Mediterranean early successional grassland community were investigated. Interactions of plant functional groups and species within the soil decomposer community resulted in significant shifts of plant competitive strength and therefore are likely to affect the rate of the successional development of plant communities. Depending on the functional role of the decomposer taxa involved, either legumes, or non-leguminous forbs were more negatively affected. Therefore, increasing species numbers with in the decomposer community gradually reduced the relative contribution of forbs (legumes and non-leguminous forbs), although fundamentally different mechanisms were responsible for these effects. Surprisingly, not the biomass-dominant annelid taxa, but collembola had the strongest effects on plant performance. The grass-to-forb ratio, an indicator of successional change, shifted from 3 to 4 in presence of collembola, suggesting that indirect effects on microbial symbionts of plants were more important than classic decomposer effects via increased and more constant nutrient availability to plants. Total plant productivity, however, was not affected, since grasses gained competitive advantage and compensated with increased growth for the negative animal effects on forb performance. Our results highlight the importance of specific functional groups among decomposers for structuring grassland plant communities. However, great plasticity in the plant community through negative covariance between forbs and grasses, partly compensated for decomposer effects at the plant canopy level.

EFFECT OF DILUTION RATE ON THE PREDICTABILITY OF A REALISTIC ECOSYSTEM MODEL WITH INSTANTANEOUS NUTRIENT RECYCLING

An analysis is made on a three dimensional mathematical model for the interaction of nutrient, phytoplankton and their predator zooplankton population in an open marine system. For a realistic representation of the open marine plankton ecosystem, we have incorporated various natural phenomena such as dissolved limiting nutrient with general nutrient uptake function, nutrient recycling, interspecies competition and grazing at a higher level. For the model with constant nutrient input and different constant washout rates, conditions for boundedness of the solutions, existence and stability of non negative equilibria, as well as persistence are given. The model system is studied analytically and the threshold values for the existence and stability of various steady states are worked out. It is observed that if the dilution rate of nutrient crosses certain critical value, the system enters into Hopf-bifurcation. Finally, it is observed that planktonic bloom can be controlled and stability around the equilibrium of coexistence can be obtained if the dilution rate of phytoplankton population is increased. Computer simulations have been carried out to illustrate different analytical results.

EFFECTS OF BAG-CONTROLLED RELEASE FERTILIZER ON NITROGEN UTILIZATION RATE, GROWTH AND FRUITING OF THE ‘FUJI’ APPLE

Bag-controlled release fertilizer is a new type of controlled-release fertilizer designed to meet the needs of the large individual volume characteristic of fruit trees. The effect of bag-controlled release fertilizer on nitrogen (N) utilization, growth-rate, and fruiting was investigated using ‘Fuji’ apple trees (M. domestica Borkh. cv. ‘Fuji’/M.hupehensis Rhed.). The results showed that the available concentration of nutrients in the soil following bag-controlled release fertilizer treatment (BCRT) was more consistent than when application treatments were broadcasted. The BCRT significantly increased N use efficiency, where this was 2.7 or 1.6 times greater than one or four broadcasted treatments, respectively. Trees treated via BCRT were healthier and had more quality spurs due to more constant nutrient concentration in the soil. With the same application amount, the chlorophyll level and Pn content of BCR-treated trees were steadier and higher than those of broadcasted controls; thus, BCRT significantly increased both yield and fruit quality.

Nitrogen to phosphorus ratio of plant biomass versus soil solution in a tropical pioneer tree, Ficus insipida.

It is commonly assumed that the nitrogen to phosphorus (N:P) ratio of a terrestrial plant reflects the relative availability of N and P in the soil in which the plant grows. Here, this was assessed for a tropical pioneer tree, Ficus insipida. Seedlings were grown in sand and irrigated with nutrient solutions containing N:P ratios ranging from <1 to >100. The experimental design further allowed investigation of physiological responses to N and P availability. Homeostatic control over N:P ratios was stronger in leaves than in stems or roots, suggesting that N:P ratios of stems and roots are more sensitive indicators of the relative availability of N and P at a site than N:P ratios of leaves. The leaf N:P ratio at which the largest plant dry mass and highest photosynthetic rates were achieved was ∼11, whereas the corresponding whole-plant N:P ratio was ∼6. Plant P concentration varied as a function of transpiration rate at constant nutrient solution P concentration, possibly due to transpiration-induced variation in the mass flow of P to root surfaces. The transpiration rate varied in response to nutrient solution N concentration, but not to nutrient solution P concentration, demonstrating nutritional control over transpiration by N but not P. Water-use efficiency varied as a function of N availability, but not as a function of P availability.

Potting substrate and nursery fertilization regime influence mycorrhization and field performance of Betula pubescens seedlings

The importance of nursery practices for seedling mycorrhization and field performance was investigated under nursery and field conditions on nutrient-deficient land in a reclamation area in Iceland. Containerized downy birch (Betula pubescens Ehrh.) seedlings were grown with or without ectomycorrhizal inoculum in two potting substrates (commercial Sphagnum peat moss and local sedge peat). Seedlings were, furthermore, subjected to two fertilizer regimes: constant nutrient strength and initially dilute but escalating nutrient strength. In the nursery, seedlings in Sphagnum peat moss fed with constant nutrient strength grew better than plants in other treatments. Sedge peat, escalating nutrient strength and inoculum was the only treatment combination that provided conditions for prolific mycorrhization in the nursery. In the field, seedlings subjected to mycorrhizal inoculation and/or escalating nutrient strength survived better and had less shoot dieback than seedlings of contrasting treatments. Furthermore, seedlings raised in sedge peat substrate grew better in the field than seedlings raised in Sphagnum peat moss. Seedling mycorrhization at planting correlated positively with seedling field survival and growth and negatively with shoot dieback. The results illustrate that biological and chemical substrate conditions in the nursery can be decisive for the mycorrhizal development and field performance of tree seedlings.

Comparative studies on storage cells in tardigrades during starvation and anhydrobiosis

Abstract The impact of starvation and anhydrobiosis on the number and size of the storage cells in the tardigrade species Milnesium tardigradum, Paramacrobiotus tonollii and Macrobiotus sapiens was investigated to gain more insight on the energetic side of anhydrobiosis. Storage cells are free floating cells within the body cavity of tardigrades and are presumed to store and release energy in form of glycogen, protein and fat to maintain a constant nutrient regime for the other tissues. The body size of the animals was not correlated with the size of the storage cells, however, M. tardigradum the largest species analysed also had the largest storage cells. A reduction in the size of the storage cells is apparent in all three species after seven days of starvation. A seven-day period of anhydrobiosis leads to a decrease in cell size in M. tardigradum but not in P. tonollii and M. sapiens. Although M. sapiens was raised on green algae, and M. tardigradum and P. tonollii were fed with rotifers and nematodes this difference in nourishment was not reflected in the response of the storage cells to anhydrobiosis.

A Correlation to Estimate the Bioventing Degradation Rate Constant

ABSTRACT Estimating the biodegradation rate is essential when designing a bioremediation strategy for petroleum-contaminated sites, and when evaluating assessment guidelines. However, estimating the biodegradation rate is difficult as the rate constant varies from site to site due to changing site conditions, which include soil type, biological activity, and type of contaminant. Accordingly, bench-scale biodegradation studies were completed using respirometers to measure first-order biodegradation rate constants for gasoline in several soils over 30 days of incubation. A total of seven soils were tested at various gasoline concentrations with constant nutrient ratios and water content. No microbial inhibition was observed for the range of gasoline concentrations studied. Analysis showed that the statistically significant parameters were the initial population of petroleum-degrading microorganisms and the organic matter content. The developed empirical correlation is a simple tool that practioners can use to estimate the biodegradation rate without conducting lengthy and expensive experiments.

Breaking the Barriers: Microbial Effector Molecules Subvert Plant Immunity

Adaptation to specialized environments allows microorganisms to inhabit an enormous variety of ecological niches. Growth inside plant tissues is a niche offering a constant nutrient supply, but to access this niche, plant defense mechanisms ranging from passive barriers to induced defense reactions have to be overcome. Pathogens have to break several, if not all, of these barriers. For this purpose, they secrete effector molecules into plant cells to interfere with individual defense responses. Plant defense is organized in multiple layers, and therefore the action of effectors likely follows this same order, leading to a hierarchy in effector orchestration. In this review we summarize the latest findings regarding the level at which effectors manipulate plant immunity. Particular attention is given to those effectors whose mechanism of action is known. Additionally, we compare methods to identify and characterize effector molecules.

Comparative studies on storage cells in tardigrades during starvation and anhydrobiosis

The impact of starvation and anhydrobiosis on the number and size of the storage cells in the tardigrade species Mil- nesium tardigradum, Paramacrobiotus tonollii and Macrobiotus sapiens was investigated to gain more insight on the energetic side of anhydrobiosis. Storage cells are free floating cells within the body cavity of tardigrades and are presumed to store and re- lease energy in form of glycogen, protein and fat to maintain a constant nutrient regime for the other tissues. The body size of the animals was not correlated with the size of the storage cells, however, M. tardigradum the largest species analysed also had the largest storage cells. A reduction in the size of the storage cells is apparent in all three species after seven days of starvation. A seven-day period of anhydrobiosis leads to a decrease in cell size in M. tardigradum but not in P. tonollii and M. sapiens. Al- though M. sapiens was raised on green algae, and M. tardigradum and P. tonollii were fed with rotifers and nematodes this dif- ference in nourishment was not reflected in the response of the storage cells to anhydrobiosis (Current Zoology 56 (2): 259-263,

Influence of periparturient nutritional demand on resistance to parasites in livestock

Periparturient relaxation of immunity (PPRI) to gastrointestinal nematode parasites may have a nutritional basis, as the increasing nutrient demand at times of nutrient scarcity during late pregnancy and subsequent lactation may result in a penalty on expression of acquired immunity to parasites. This nutritional basis implies that lowering nutritional demand, at constant nutrient supply, should reduce the degree of PPRI. Evidence to support the latter is reviewed through exploration of the effects of reproductive effort on periparturient resistance to parasites. A large body of evidence shows that a lower nutritional demand arising from rearing single rather than multiple lambs and/or kids consistently reduces the degree of PPRI in small ruminants, as manifested by reduced worm burdens and/or nematode egg excretions. Such variation in reproductive effort may also account, at least to some extent, for the often observed between-breed differences in PPRI, which may arise from differences in production potential, and thus nutritional demand. A reduction in nutrient demand can reduce the degree of PPRI in a matter of days. However, host immune responses associated with this nutritional sensitivity of host resistance remain to be elucidated, which may be achieved through a recently established periparturient rodent model.

Dynamics of Nutrient-Phytoplankton Interaction in the Presence of Viral Infection and Periodic Nutrient Input

Chattopadhyay et al. [Biosystems (2003), 68, pp. 5-17] proposed and analyzed an N – P model in the presence of viral infection on phytoplankton population. They studied the dynamics under the constant nutrient input. The present paper deals with the problem with seasonal variability on nutrient input. We use a general periodic function for nutrient input. We observe the dynamics of the system by considering (i) the infected phytoplankton consumes nutrient and (ii) the infected phytoplankton is not in a state to consume nutrient. Conditions for the persistence and extinction of populations are worked out. Our numerical experiments show that if the infected phytoplankton does not take nutrient then susceptible phytoplankton coexists with the infected ones. But if the infected phytoplankton consumes nutrient then there is a chance for extinction of susceptible phytoplankton for high rate of infection. We also observe that periodic nutrient input enforces the system to enter into chaotic region.

Modelling Na and Cl concentrations in the recycling nutrient solution of a closed-cycle pepper cultivation

A mass balance model relating the concentrations of Na or Cl in the recycled nutrient solution to the cumulative uptake of water by the plants was calibrated and validated in greenhouse sweet pepper crops grown in closed-cycle cultivation systems. The results indicated that the model allows for simulation of the courses of Na and Cl accumulation in closed-cycle cultivations of pepper, provided that the fluctuations in the volume of drainage solution and the moisture status of the substrate during the cropping period are small. Furthermore, the model predicts a delay in the process of salt accumulation in closed-cycle hydroponic systems when the drainage percentage is relatively high due to enhanced irrigation frequency, in compassion with standard irrigation frequency. The proposed model may be incorporated into intelligent automation systems to automatically adjust the target total salt concentration in the outgoing irrigation solution to levels allowing for a constant nutrient supply, despite the Na and Cl accumulation in the recycled leachate. As a result, the entire amount of drainage solution can be recycled without risking depletion of essential nutrients in the root zone.