Higher Nutrient Release Research Articles

Fortification of Organic Manures with Iron on Nutrient Release Characteristics

Aims: The objective of current study was to examine the nutrient release pattern by enriching different organic manures with iron fertilizer at different ratios in regular sampling intervals.
 Study Design: The design used in this current study was Factorial completely randomized block design with six treatments replicated thrice.
 Place and Duration of Study: An incubation experiment was carried out in the Department of Soil Science and Agricultural Chemistry, Tamil Nadu Agricultural University, India during December - March 2022.
 Methodology: An incubation experiment was carried out by enriching inorganic iron fertilizer with three different organics such as FYM, vermicompost and biocompost in two ratios viz., 1:5 and 1:10 at four different sampling intervals 7, 14, 21 and 28 days after incubation and analyzed for various physical and chemical properties to study the iron release pattern.
 Results: The results revealed that the iron content ranged from 5324 to 8823 mg kg-1. Among all the combinations, the highest nutrient release was found in FeSo4 enriched with vermicompost 1:10 ratio at 21 DAI which is followed by FeSo4 enriched with FYM 1:10 ratio.
 Conclusion: The present study revealed that the integrated application of organic and inorganic fertilizer significantly improved the iron use efficiency. Only a few work were reported on integrated application of micronutrient at different organic fertilizer rates, however need further studies to validate the reliability.

The dual mechanisms of composite biochar and biofilm towards sustainable nutrient release control of phosphate fertilizer: Effect on phosphorus utilization and crop growth

The low utilization rate of phosphorus fertilizers is a common concern and is caused by high leaching loss rates and rapid nutrient release. While the precipitation with soil components also brings a series of problems. To address these problems, we propose a composite biochar and a hydrophobic biofilm to act as a synergistic mechanism for nutrient release control and to provide the required nutrients for crop growth. We optimized the preparation of composite biochar materials (1:1.2, 1.5 h, 450 °C) and explored the nutrient loading mechanism by different adsorption kinetic model fitting. The fitting curve showed that PO43− best fit with the Redlich-Peterson model with a high correlation coefficient (R2 = 0.9933). The water contact angle of a cotton stalk hydrophobic membrane material was 109°. Leaching experiments showed phosphate leaching losses increased with an increase in the amount in hydrophobic biofilm (2%, 4%, 6%), which showed a decreasing trend of 24%, 16% and 10%, respectively. After 31 d of nutrient release, the cumulative release rate of HCP2 was 65%, which matched the growth demand of corn maize crops and had a significant effect on early maize growth. All agronomic data showed optimized root length (32.5 cm), plant height (58.7 cm), dry weight (0.527 g) and fresh weight (4.907 g). This showed that the phosphate fertilizer carrier and co-release system constructed by the combination of biochar and biofilm has great advantages in promoting crop growth and a sustainable agricultural economy.

Effect of alley plants species and plantain cultivars on yield of ita 331 upland rice in Umudike southern Nigeria

Alley cropping or hedgerow intercropping is one of the many sub-systems of agroforestry technology. A 5 x 3 factorial experiment in a Randomized Complete Block Design (RCBD) with three replications was used to determine the effect of four alley woody species and three plantain cultivars on the yield of ITA 331 upland rice grain in the 2017 and 2018 farming seasons. The Alley species, plantain cultivars and Alley species x plantain cultivars treatment interactions showed no significant effects (p>0.05) on ITA 331 upland rice grain yield. Student t-test on the two farming seasons showed significant increase in yield of ITA 331 upland rice grain in 2018 than in 2017. The non-significantly different rice grain yield in the alley species treatment plots could be due to the generally high nutrient release of the decomposed legume-based alley species. Agroforestry combination of alley plants species and plantain cultivars is suitable for ITA 331 upland rice production.
 Key words: alley cropping, yield, ITA 331 upland rice grain, alley woody species, plantain cultivars

Application of Gliricidia sepium Tree Leaves and Nitrogen Fertilizer to Improve Tomato Production and Soil Properties

Excess use of agrochemicals for intensive cultivation affects crop quality and destroys agro-ecosystems, and eventually creates health hazards. The study aims to investigate the effect of Gliricidia sepium (GS) tree leaf as suitable green manures for supplementing nutrient supply along with nitrogen (N) fertilizer to produce quality tomato and soil fertility improvement. A field experiment was conducted at the Bangabandhu Sheikh Mujibur Rahman Agricultural University, Bangladesh, from November 2016 to March 2017. The experiment was laid out in a randomized complete block design (two factors) with three replications. There were nine treatment combinations with three levels of GS tree leaves (5, 10 and 15 t ha−1) and three doses of N (0, 50 and 100% of the recommended dose of fertilizer). The highest tomato yield was recorded in GS15×N100 treatment combination, which was 41.68% higher compared to the control treatment. Decreasing C: N ratio in increasing dose of GS and N treated plot indicated the quality of tree leaves that ensures faster decomposition and high nutrient release pattern of this species. Increasing rate of soil pH and cation exchange capacity (CEC) in different treatments as compared to initial soil showed soil fertility improvement. Overall, the results indicated that quality tomato could be grown successfully by the application of G. sepium tree leaves along with an appropriate amount of N fertilizer.
 Ann. Bangladesh Agric. (2020) 24(1) : 77-87

Dynamics in tropical lowland soil nutrients as influenced by leafy biomass of some agroforestry trees

One of the major challenges of the developing countries is the production of sufficient food for the rapidly increasing population, and over cultivation of land resulting to soil infertility. Hence, transfer of nutrients through tree biomass contribute to micro variability in soil fertility and plant growth. A field research was conducted in the forest nursery of the Federal University of Agriculture, Abeokuta (FUNAAB), Nigeria to investigate the response of tropical lowland soil to the application of leafy biomass of some agroforestry tree species; Anogeissus leiocarpus, Enterolobium cyclocarpum, Gliricidia sepium, Leuceana leucocephala and Treculia africana at the rate of 5 tons per hectare (5t ha-1 or 5000 kg ha-1). The soil samples were collected at 2, 4, 6, 8 and 10 weeks after application (WAP). Split plot experimental design was used with the time of soil sampling as main plots, mulch type as sub-plots. Data were statistically analysed using Analysis of Variance (ANOVA) at p =0.05 on pH, organic carbon, total N, P, K, Ca, Mg and Na. L. leucocephala had highest nutrient release values on; total nitrogen (0.019±0.002), calcium (41.07±3.75), sodium (139.0±36.927). Control plots was high in organic carbon (3.12±0.067), as well as pH (6.45±0.029). However, E. cyclocarpus also had highest nutrient contents in potassium (90.0±4.79) and magnesium (152.50±24.575). It is concluded that L. leucocephala had fast decomposition rate and its rapid nutrient release is a good alternative to improving soil nutrients in lowland tropical soil and therefore recommended as a better choice soil improvement agroforestry tree leafy biomass among other species as investigated from the study.

Decomposition and release of nutrients from crop residues on soybean-maize cropping systems

Nutrients found in residues from agricultural cultures are important reserves for subsequent crops. The objective was to assess the decomposition and release of nutrients from different crop residues for subsequent soybean cultivation. The study was conducted in Mid-Northern Mato Grosso State, Brazil. The residual straw of cropping systems - maize, brachiaria and maize/brachiaria consortium - were sampled, weighted, disposed in litter bags and then distributed on the soil. The adopted experimental design followed the completely randomized arrangement with three repetitions. Treatments were determined based on harvest time, which was performed every 14 days within 140 days for maize, and within 154 days for brachiaria and for the consortium. The remaining dry matter and nutrients content, and half-time life were evaluated. Maize showed the highest straw dry matter yield (14,176 kg ha-1), and the consortium recorded the biggest nutrient accumulation per hectare (K=172.2; N= 141.7 and Ca=56.0 kg ha-1). Brachiaria straw presented the fastest decomposition rate (85%) and the highest nutrient release (K=99%; N=92%; Mg=98% and Ca=90% of total initial content). The total K released reached 150 kg ha-1, which can fit the needs of soybean crops.

Fate of nutrients and heavy metals during two-stage digestion and aerobic post-treatment of municipal organic waste

The biogas technology is a promising approach for the recovery of energy and fertilizer from municipal organic waste (MOW). However, only scarce information on the development of initial nutrient and heavy metal loads during processing is available. Therefore, this study investigates properties of source-separated MOW during treatment in a semi-industrial scale two-stage biogas plant and subsequent digestate composting including impurities removal. Data from 15 batch experiments was investigated by material and substance flow analysis. Results of this study have shown that about 40% of nutrients contained in the MOW inflow are mineralized during anaerobic and subsequent aerobic treatment. A higher nutrient release was observed during the anaerobic treatment step. Additionally, impurities removal causes a significant reduction of final nutrient content. Heavy metal analysis confirmed a high heterogeneity of contamination levels. However, digestion and composting do not seem to significantly impact on total heavy metal loads in the substrate flow.

Assessment of Potential Nutrient Release from Phosphate Rock and Dolostone for Application in Acid Soils

Finding alternative local sources of plant nutrients is a practical, low-cost, and long-term strategy. In this study, laboratory column experiments were conducted in a completely randomized design to evaluate the feasibility of using phosphate rock and dolostone as fertilizers or acid-neutralizing agents for application in tropical acid soils. The dissolution rates of different particle-size fractions (0.063–0.25, 0.25–0.5, and 0.5–2 mm) of both rocks were studied by citric acid solution at pH 4 and 2 and water, with extraction times of 1, 3, 5, 7, 12, 24, 72, 144, 240, and 360 h. The results showed that the dissolution of both rocks depended on the particle size, leaching solution, and extraction time. The dissolution rate of rock-forming minerals increased as the specific surface area increased, corresponding to a decrease in particle size. In all cases, the release kinetics was characterized by two phases: 1) a first stage of rapid release that lasted 24 h and would ensure short-term nutrient release, and 2) a second stage of slow release after 24 h, representing the long-term nutrient release efficiency. Both rocks were suitable as slow-release fertilizers in strongly acid soils and would ensure the replenishment of P, Ca, and Mg. A combination of fine and medium particle-size fractions should be used to ensure high nutrient-release efficiency. Much work could remain to determine the overall impact of considerable amounts of fresh rocks in soils.

Decomposition and nutrient release in leaves of Atlantic Rainforest tree species used in agroforestry systems

Aiming to support the use of native species from the Atlantic Rainforest in local agroforestry systems, we analysed chemical and biochemical components related to leaf decomposition of Inga subnuda, Senna macranthera, Erythrina verna, Luehea grandiflora, Zeyheria tuberculosa, Aegiphila sellowiana, and Persea americana. These tree species are native (except for P. americana) and commonly used in agroforestry systems in the Atlantic Rainforest. For the three first species (Fabaceae), we also analysed the remaining dry matter and released nutrients from leaves, using litter bags, and biological nitrogen fixation, using Bidens pilosa and Brachiariaplantaginea as references of non-N2-fixing plants. Leaves from I. subnuda, L. grandiflora, and P. americana had a lower decomposition rate than the other species, exhibiting negative correlations with lignin/N and (lignin+polyphenol)/N ratios. The percentages of remaining dry matter after 1 year were 69 % (I. subnuda), 26 % (S. macranthera) and 16 % (E. verna). Higher nutrient release was found in decreasing order from residues of E. verna, S. macranthera, and I. subnuda. The percentages of nitrogen fixation were 22.6 % (E. verna), 20.6 % (I. subnuda) and 16.6 % (S. macranthera). Diversification of tree species in agroforestry systems allows for input of diversified organic material and can contribute to maintaining and improving soil functions resulting in improvements of soil quality.

Produção e ciclagem de nutrientes por plantas de cobertura nas culturas de arroz de terras altas e de soja

As plantas de cobertura em sistema de plantio direto pode contribuir na formação de palhada e ciclagem de nutrientes para as culturas em sucessão. O objetivo deste trabalho foi avaliar a produção de matéria seca e ciclagem de nutrientes por plantas de cobertura semeadas em safrinha no desempenho do arroz de terras altas e da soja semeados em rotação, em sistemas plantio direto e preparo convencional, em Latossolo Vermelho do município de Rio Verde, Goiás. O estudo foi realizado no período de abril de 2008 a abril de 2010. Utilizou-se o delineamento em faixas com fatorial 2 x 5 com quatro repetições. Nas faixas horizontais foram testados os dois sistemas de manejo do solo (plantio direto e convencional) e nas faixas verticais, as plantas de cobertura. As avaliações de matéria seca, taxa de cobertura do solo e ciclagem de nutrientes foram realizadas apenas nos tratamentos plantio direto, em que as parcelas foram subdivididas em seis épocas de coletas de matéria seca após a dessecação das plantas de cobertura, o que ocorreu aos 0, 15, 30, 60, 90 e 120 dias a partir da dessecação de manejo das plantas de cobertura, perfazendo um fatorial 5 x 6. As plantas de cobertura, semeadas em safrinha, foram as seguintes: Brachiaria brizantha, B. ruziziensis, Pennisetum glaucum e B. ruziziensis + Cajanus cajan e o pousio. Avaliaram-se a produção de matéria seca, a taxa de cobertura do solo, o acúmulo e liberação de nutrientes pelas plantas de cobertura e a produtividade do arroz na safra 2008/09 e da soja na safra 2009/10, semeados em rotação. As espécies B. ruziziensis e B. ruziziensis + C. cajan destacaram-se na produção de matéria seca, taxa de cobertura do solo e acúmulo de nutrientes no final do período de entressafra. Os nutrientes com mais acúmulos nas matérias secas foram N e K, e as maiores taxas de liberação no solo foram observadas nos elementos K e P. As maiores produtividades de arroz sob plantio direto foram obtidas sobre palhadas de P. glaucum e B. ruziziensis, enquanto a cultura da soja não apresentou diferenças em sua produtividade nos tratamentos estudados.

Waste activated sludge fermentation: Effect of solids retention time and biomass concentration

Laboratory scale, room temperature, semi-continuous reactors were set-up to investigate the effect of solids retention time (SRT, equal to HRT hydraulic retention time) and biomass concentration on generation of volatile fatty acids (VFA) from the non-methanogenic fermentation of waste activated sludge (WAS) originating from an enhanced biological phosphorus removal process. It was found that VFA yields increased with SRT. At the longest SRT (10 d), improved biomass degradation resulted in the highest soluble to total COD ratio and the highest VFA yield from the influent COD (0.14 g VFA-COD/g TCOD). It was also observed that under the same SRT, VFA yields increased when the biomass concentration decreased. At a 10 d SRT the VFA yield increased by 46%, when the biomass concentration decreased from 13 g/L to 4.8 g/L. Relatively high nutrient release was observed during fermentation. The average phosphorus release was 17.3 mg PO 4-P/g TCOD and nitrogen release was 25.8 mg NH 4-N/g TCOD.

LIXIVIAÇÃO DE NUTRIENTES DA SERAPILHEIRA RECÉM-DEPOSITADA EM SUCESSÃO ECOLÓGICA NA FLORESTA ATLÂNTICA, LITORAL DO PARANÁ

O presente estudo foi realizado na Floresta Ombrófila Densa das Terras Baixas, no litoral paranaense, onde foram instaladas parcelas em três fases sucessionais, denominadas fases sucessionais inicial, intermediária e avançada. Os objetivos do estudo foram avaliar a contribuição imediata das folhas de algumas espécies selecionadas e demais frações da serapilheira na liberação de nutrientes para o solo por meio da lixiviação. Para a coleta, foram instalados 10 coletores tipo cesta em cada fase sucessional. Esse material foi coletado durante um ano e lixiviado por pulverização em casa de vegetação, sendo analisada a concentração de K, Ca, Mg e Na no lixiviado coletado. Os resultados mostraram diferenças na liberação de nutrientes da serapilheira coletada ao longo das estações, ou seja, as condições climáticas apresentaram efeito sobre a qualidade da serapilheira lixiviada. O comportamento das fases sucessionais foi distinto, sendo que a maior liberação de nutrientes das folhas das espécies selecionadas ocorreu na fase avançada. A ordem decrescente de liberação de nutrientes da serapilheira foi a seguinte: K > Mg > Na > Ca. De forma geral, observou-se que os elementos foram liberados das frações da serapilheira na seguinte ordem decrescente: fração miscelânea > fração ramos e frutos > fração folhas.

Solubilization of municipal anaerobic sludge using microwave-enhanced advanced oxidation process

The effect of microwave enhanced advanced oxidation process on the release of nutrients and solids disintegration from municipal anaerobic sludge was investigated. Three levels of temperature (160, 120, and 80°C) and two sets of pH, (7.8 and 4) were selected and tested at a microwave heating time of 5 minutes and hydrogen peroxide dosage of approximately 1 mL per 1% total solids. Total chemical oxygen demand concentrations in samples decreased after the treatments at pH 4, while they remained the same as the initial at pH 7.8. The soluble chemical oxygen demand concentrations increased in all sets, regardless of treatment conditions. There was an increase in orthophosphate concentration with an increase of temperature at pH 4, while a decrease of orthophosphate at pH 7.8 was observed. Ammonia concentration also increased with an increase of temperature at pH 4. A small amount of ammonia was converted to nitrates/nitrites in the absence of acid. Acid addition helped in the destruction of sludge solids. Low pH and high temperature gave the highest nutrient release and solids destruction.

Perennial crops and endogenous nutrient supplies

AbstractPerennial cropping systems may achieve significant improvement over annual systems in the synchrony between crop nutrient demands and nutrient supplies. Improvements in nutrient synchrony would result in the reduction of nutrient losses and their associated environmental impacts. A perennial system with high levels of synchrony would also require fewer nutrient inputs, such that it may be possible to develop an agriculture that functions mostly, if not entirely, on nutrient inputs from endogenous sources (i.e., weathering of primary and secondary minerals and biological nitrogen fixation). In this paper I describe three realms of research that will inform the development of relatively high-yielding grain production systems grown on endogenous nutrient supplies: (1) improvement of nutrient synchrony through the development of perennial crops; (2) identification of soils that are in a high nutrient release phase of pedogenesis, which could balance the export of rock-derived nutrients in crop harvests; and (3) optimization of legume density, harvest index and percent nitrogen derived from the atmosphere (%Ndfa) to achieve adequate nitrogen inputs through biological fixation.

Effects of Forest Fire on Leaf Litter Decomposition of Two Dominant Species (and Calophyllum pulcherrimum) in a Heath Forest of South Kalimantan

In order to determine the effects of frequent forest fire on the decomposition process, two dominant species of heath forests were studied: T. obovata and C. pulcherrimum. During a period of two years, it was observed that T. obovata decomposed more rapidly with higher nutrient release than C. pulcherrimum in intact and post-fire stands. The decomposition rates of the two species were higher in the intact stand than in the post-fire stand. C/N ratio dynamics and nitrogen release were determined showing that T. obovata rapidly released nutrients and C. pulcherrimum retained nutrients. The results suggest that forest fire did not change the nutrient release pattern of these two dominant species, but did slow the decomposition rate and, consequently, affected the rate of nitrogen release.

Remineralization ratios of carbon, nutrients, and oxygen in the North Atlantic Ocean: A field databased assessment

Remineralization ratios of carbon, nutrients, and oxygen have been assessed in the North Atlantic Ocean along the WOCE 1A/E section. The study is based on an extensive field data set comprising dissolved inorganic carbon (DIC), nitrate and nitrite (NO3/2), phosphate (PO4), and oxygen (O2) data as well as hydrographic data. A procedure has been introduced which normalizes DIC data to constant salinity and temperature and corrects for the contamination from anthropogenic CO2. The remaining variability on the normalized DIC values (DICbio) can be attributed to the remineralization of organic matter. DICbio can thus be seen as carbon‐analogy to the apparent oxygen utilization (AOU). The consecutive evaluation of the remineralization ratios obtains two different regimes separated at the density level ρ = 1027.7 kg m−3. In the shallower level the ratios (C/N = 4.5; C/P = 67, AOU/C = 2.0; N:P = 15; AOU:P = 134; AOU/N = 9.0) are shifted toward relatively higher nutrient release and higher oxygen consumption with respect to the Redfield ratios of particulate organic matter (POM). In contrast, in the deeper levels the ratios are shifted toward relatively higher carbon release and lower oxygen demand (C/N = 11; C/P = 152, AOU/C = 0.86; N:P = 13.9; AOU:P = 130; AOU/N = 9.4). The depth integrated inventories of the remineralization products (DIC, NO3/2, PO4, and AOU) provide water column averaged ratios for the investigation area (C/N = 8.8; C/P = 124, AOU/C = 1.1; N:P = 14.2; AOU:P = 131; AOU/N = 9.3) which imply a higher efficiency of the biological carbon pump in the North Atlantic Ocean than predicted with respect to the elemental composition of POM.

Response of Chromolaena odorata to timber tree densities in an agrisilvicultural system in Cameroon: aboveground biomass, residue decomposition and nutrient release

In low-input land-use systems combining timber trees with shade-tolerant understorey crops, it is essential to establish the effects of tree density upon weeds and the contribution of weeds to competition and nutrient cycling. Adjusting tree density may alter weed competition for light, water and nutrients, the storage of nutrients by weeds through growth and the release of nutrients via decomposition of slashed weed residues. The effects are reported of (1) two timber stand densities (TSDs) and, (2) retention versus burning of slashed vegetation at field preparation, upon Chromolaena odorata (kondengui), the dominant weed, in an agrisilvicultural system in southern Cameroon. The system comprised the timber species, Terminalia ivorensis, and plantain as an understorey crop. Total weed biomass was measured at the first weeding, 3 months after planting (MAP), and total weed biomass and aboveground biomass, partitioning and nutrient accumulation of C. odorata were measured at the second and third weedings, 7 and 12 MAP. Mass and nutrient loss were measured from stem and leaves placed separately in decomposition bags. Here, burning was not an appropriate weed management tool, as it resulted in greater weed biomass. A high TSD did reduce weed biomass. However, foliar nutrient concentrations were generally higher in high TSDs. Thus, retaining trees in the high TSD did not lead to any reduction in nutrient uptake by the C. odorata stand. Furthermore, in the high TSD, mass loss and nutrient release characteristics had higher coefficients, and a higher percentage of the total nutrients accumulated were released in the early stages of incubation, all increasing the risk of nutrients being lost from the topsoil. Thus, from a weed competition perspective, there were few benefits to retaining a high timber stand density.

Rain forest on Maracá Island, Roraima, Brazil: soil and litter process response to artificial gaps

Artificial canopy gaps were made by felling trees in rain forest on Maracá Island. There were three replicates of each gap size: small (c. 40 m 2), medium (c. 150 m 2), large (c. 350 m 2), very large (c. 2500 m 2), and unfelled forest controls (2500 m 2). Changes in microclimate, soil chemistry, and soil biological processes including decomposition were measured for up to 12 months. Higher maximum and lower minimum air temperatures occurred with increasing gap size but there was little consistent effect of gap size on soil chemistry. Microbial biomass, soil respiration, and nitrogen mineralization and nitrification were investigated in medium gaps. No differences were found between the gaps and the unfelled forest, and all had their lowest values in the dry season. Within the medium gaps higher values for these variables occurred in the `under crown' position (where the crowns of the felled trees had fallen under the surrounding canopy). Three litter-bag decomposition experiments were made over 217 d. No relationship was found between decomposition and nutrient release rates and size of gap or position within it and no clear trend was found with position along a central trunk within a gap, but a higher weight loss and nutrient release occurred under the crowns of fallen trees. It is concluded that decomposition and nutrient release rates are not influenced in a consistent way by gap size. It may be that small areas of high nutrient release can be caused by the local addition of large quantities of substrate, even though process rates remain unaltered. Because large additions of readily decomposable substrate are most likely to occur under a closed canopy, there is no support from the Maracá data that growth responses to gaps will involve an interaction between enhanced nutrient supply and increased light.

Annual variation in condition, respiration and remineralisation ofMytilus edulis L. in the Sound, Denmark

By means of monthly in situ incubations, variations in oxygen uptake, nutrient release and C/N-ratio were monitored during a period of 14 months of a mussel population (Mytilus edulis L.) located on an exposed beach. A condition index calculated as weight/length3 showed that the condition of the mussels was highest in the spring. Specific oxygen uptake and nutrient release had separate maxima, with high oxygen uptake in the spring coinciding with a period of growth, and high nutrient release during summer when the temperature was highest. Oxygen uptake was significantly correlated with both the condition of the mussels and the temperature, while ammonium release was significantly correlated only with the temperature. Except in spring, the oxygen uptake, condition index and O/N-ratio were low, indicating a poor condition of the mussels. The mussels suffered from suboptimal conditions caused by inadequate food supply and failed to accumulate glycogen reserves essential for the development of mature gametes.

Mussel beds: limiting or promoting phytoplankton?

Seasonal variation of phytoplankton over an intertidal mussel bed was measured in the Wadden Sea near the island of Sylt between February 1984 and April 1985. To quantify the uptake of phytoplankton by a mussel bed, an open flow-through system, the Sylt flume (20 × 2 × 2 m), canalized the tidal water over a bed of Mytilus edulis L. Changes in the content of phytoplankton in the water passing through the flume were used to calculate phytoplankton uptake over three tidal cycles in the summer of 1986. Phytoplankton plankton biomass was reduced by 37 ± 20% between the inflow and outflow of the flame. This figure includes active filtration of mussels and sedimentation. Phytoplankton biomass was reduced by the mussel bed over the whole size range from the smallest cells of 4 μm (or a new pg C·cell −1) up to the largest diatoms of several hundred μm (or a new thousand pg C·cell −1. The higher the phytoplankton concentration, the higher the uptake by the mussel bed. There was a significant positive correlation between both concentration and uptake of phytoplankton. Parallel with the uptake of phytoplankton by the mussel bed, a higher nutrient release by the mussel bed was measured. Potential primary production based on the N : C ration of 16 : 106 was estimated, assuming that the released ammonium would be taken up entirely by phytoplankton. Following this assumption, the potential primary production induced by the nutrient release of the mussel bed is higher than the uptake of phytoplankton by the mussel bed. It is also probable that mussels extract N from particulate organic material other than phytoplankton. While mussels strongly reduce phytoplankton biomass, mussel beds also have the potential to significantly promote primary production.