Initial Nutrient Concentrations Research Articles

Climate and soil properties regulate the initial concentrations of potassium, calcium and magnesium in plant litter on a global scale

Abstract The initial concentration of litter nutrient not only affects the following decomposition process but also determines the quantities of nutrients returned to the soil. The aim of this study is to assess the global patterns and driving factors of three macronutrients, namely potassium (K), calcium (Ca) and magnesium (Mg), in freshly fallen litter. By synthesizing 5861 data points extracted from 584 publications, we quantitatively evaluated the concentrations of litter K, Ca and Mg in different litter types, life forms, taxonomic divisions and mycorrhizal associations. Also, using the machine learning method, we predicted their global patterns in forests, grasslands and shrublands. We found that (1) mean K, Ca and Mg concentrations ranged from 2.63 to 6.23, 1.05 to 11.50 and 0.20 to 2.74 g/kg, respectively, across different litter types; (2) the initial nutrients of the litter were significantly affected by plant functional types (e.g. life form, taxonomic division and mycorrhizal association), climate (e.g. isothermality, mean diurnal range, annual evapotranspiration and precipitation seasonality) and soil properties (e.g. pH, exchangeable Ca concentration and water content), with a higher litter K concentration of herbaceous plants, higher K, Ca and Mg concentrations from angiosperms and higher K and Mg concentrations from plants associated with arbuscular mycorrhiza (AM) fungi; and (3) the predicted leaf litter K, Ca and Mg concentrations were lower in high‐latitude regions compared with those in low‐ and/or mid‐latitude regions. Our study provides a globally comprehensive analysis on the patterns and driving factors of three important macronutrients in freshly fallen litter, contributing to a better understanding of their role in the decomposition process of litter, as well as the associated biogeochemical cycles under the future climate change scenario. Read the free Plain Language Summary for this article on the Journal blog.

Biochar as a potential tool to mitigate nutrient exports from managed boreal forest: A laboratory and field experiment

AbstractForest management in drained forested peatlands can negatively affect water quality due to the increase in exports of organic matter and nutrients. Therefore, new methods to alleviate this impact are needed. In laboratory conditions, biochar has been shown to be a strong sorbent of organic and inorganic nutrients due to its high surface area and ion‐exchange capacity. However, evidence of the adsorption capacity in field conditions is lacking. Here, we studied the water purification performance of two different biochar feedstocks (wood‐ and garden residue‐based) in a 10‐day laboratory experiment where we incubated biochar with runoff water collected from drainage ditches in clear‐cut peatland forests. We measured changes in pH and concentrations of inorganic phosphorus (PO4), total dissolved nitrogen (TDN), and dissolved organic carbon (DOC). The biochar with the best adsorbent capacity in the laboratory experiment was then tested in field conditions in a replicated catchment‐scale experiment, where both clear‐cutting and ditch cleaning were performed. We determined the nutrient concentration of water at the inlet and outlet of biochar filters placed in outflow ditches of four catchments. We found that under laboratory conditions wood‐based biochar efficiently adsorbed TDN and DOC, however, it released PO4. Furthermore, we found that the biochar filters reduced TDN and DOC concentration in field conditions. However, the percentage decrease in concentration was dependent on the initial concentrations of nutrients in the water and could be considered low. Moreover, we found that the biochar in the filters increased in TN content over the course of the experiment. This suggests that a wood‐based biochar filter has the potential to be a water protection tool for reducing the export of nutrients from catchments with high nutrient concentration. And that the biochar from the ditches could be applied back to the regenerating forest catchment as a potential soil amendment, closing the nutrient cycle.

Short-Term Toxicity of ZnO Nanoparticles on Microalgae at Different Initial Nutrient Concentrations

The aim of this work was to investigate the combined short-term toxic effect of zinc oxide (ZnO) nanoparticles (NPs) and nitrate concentration of the medium on freshwater microalgae. For this purpose, freshwater microalgae Chlorococcum sp. was cultivated in modified Blue-Green medium (BG-11) containing nitrate concentrations ranging from 0 to 300 mg/L, and exposed to ZnO NPs in different concentrations (0.081 to 810 mg/L) for a period up to 96 h. The experimental results revealed that algal growth was affected by the exposure time, NPs concentrations, and mainly the initial nitrate concentration. Differences in microalgae growth rates were observed. The toxic effect of ZnO NPs was higher on microalgae cultured in modified BG-11 with low and high nitrate concentrations. During the 4-day exposure, the highest growth rates were observed at 24 h at an initial nitrate concentration of 50 mg/L; 1.94 d−1 and 0.22 d−1 for 0 and 810 mg/L ZnO NPs, respectively. Nitrate uptake by algal biomass reached up to 40.1% after 96 h of operation in the control culture with an initial nitrate concentration of 50 mg/L. Finally, the results of this study showed the need for the investigation of ZnO NPs toxicity on microalgae under optimum and stressful nutrient conditions for microalgae growth.

Agronomic potential of excreta-based biofertilizers made from treated human feces and urine for crop production

The use of human excreta in agriculture is driven by water scarcity, degradation of water resources, and increased demand for food. This work investigated the agronomic potential of biofertilizers made from treated human feces and urine for crop production. In this regard, field research with 18 lysimeters (six treatments and three blocks) was conducted by applying four biofertilizers in the soil to grow Lactuca sativa var. Valentina. Treatments employed were negative control (T1), chemical fertilizer (T2), urea-treated feces (T3), composted feces with organic waste (T4), stored urine (T5), and struvite (T6). Plant development was assessed weekly by measuring the plant height and diameter. As main results, the use of the biofertilizers presented a higher growth than the negative control (T1) and lower than chemical fertilizer (T2), except for the stored urine treatment, which did not exhibit a significant difference from T1. Struvite treatment stood out, showing a height 98% higher than the negative control and final leaf numbers with no significant statistical difference from the chemical fertilizer. Therefore, treated human excreta presented a potential to fertilize the soil and plant uptake. Even though the initial nutrient concentration in the soil was very low, according to the fertilizing guide from southern Brazil, the plants could still grow and present a better development than the soil with no fertilizer. As nutrient availability in organic fertilization is slower than in chemical fertilization, sequential cultivation cycles should improve plant development.

Microbial phosphorus removal and recovery by struvite biomineralisation in comparison to chemical struvite precipitation in municipal wastewater

Microbial biomineralisation is attracting significant interest as an innovative process to recover nutrients from wastes. Nevertheless, little is understood about the requirements to form struvite using biological pathways in wastewater and how does this compare with conventional chemical processes. To address this gap, Halobacterium salinarum, Bacillus pumilus, Brevibacterium antiquum, Myxococcus xanthus and Idiomarina loihiensis were grown in wastewater to explore the relationships between cell growth, nutrients levels and properties of the recovered precipitates. The microorganisms were capable of removing ortho-phosphate (PO4-P) from municipal wastewater at concentrations ranging from 5.4 to 62.4 mg PO4-P/L. Visible crystals of biological struvite (bio-struvite) (identified by morphology XRD and elemental analysis), were observed at PO4-P ≥ 19.7 mg/L, compared to chemical struvite precipitation at 62.4 mg/L PO4-P (with pH adjustment). The initial nutrient concentrations presented a strong positive correlation with bio-struvite production yields and crystal size distribution. B. antiquum distinguished itself by relatively stable PO4-P removal (68–97%) independent of the initial nutrient concentration, with effluents containing as low as 1 mg PO4-P/L. The recovered bio-struvite presented high purity with low heavy metal contents, meeting regulations for inorganic fertiliser. The microbial processes for phosphorus (P) recovery as bio-struvite presented several key advantages: bio-struvite crystals were released to the wastewater and recoverable by filtration at PO4-P ≥ 19.7 mg/L, no need to adjust pH, bio-struvite crystals had purity equivalent to 11.8–12.3% P and low heavy metal content, which was similar or better than that of chemical struvite (12.6% P). This study validates bio-struvite’s relevance for low nutrient concentrations.

Nutrient return through decomposing Coriaria nepalensis litter in degraded hills of Kumaun Himalaya, India

Coriaria nepalensis, a nitrogen-fixing actinorhizal shrub, is a prominent and successful colonizer of bare rocks and landslide affected degraded lands. Field experiments were conducted to determine the differences in biomass decomposition and nutrient release pattern of different plant parts ofC. nepalensisusing litter bag technique. Results showed that the leaves decomposed completely within 6 months while only 46.55% of the lateral roots were decomposed with slowest decomposition rate of 0.14% day–1. The decomposition rate was in the order: Leaves > Reproductive parts > Twigs (< 5 mm) > Twigs (> 5 mm) > Bark > Fine roots > Lateral roots. The decay rate coefficient was highest (0.003–0.014) for leaves and lowest (0.001–0.002) for lateral roots. During the decomposition cycle (364 days), overall increase was reported in nitrogen and phosphorus concentration, while potassium concentration decreased continuously in residual litters. The nutrient mobility was in the order: K > P > N. Climatic factors like temperature, relative humidity and rainfall significantly affected the decomposition process and among these factors, rainfall pattern emerged as a most effective environmental driver. Thus, taking into account initial nutrient content, nutrient release and decay rates, the leaves and reproductive parts ofC. nepalensisproved to be more important as nutrient source than other components.

Nutrient Cycling of Cover Crops in an Amazonian Ecosystem

Cover crops act to improve the chemical and physical quality of the soil and provide sustainability in agricultural systems. Studying the decomposition of these cover crops is key to understand the process of nutrient cycling in cultivation. The purpose of the study was to assess the decomposition and release of nutrients from cover crops in an Amazonian ecosystem. The experiment was conducted in a commercial guarana plantation area at farm Agropecuária Jayoro in Presidente Figueiredo-AM in two agricultural years (2018 and 2019), with a randomized block experimental design following a 4 × 4 factorial scheme, with four cover species (Arachis pintoi, Brachiaria ruziziensis, Canavalia ensiformis and Mucuna deeringiana) and four assessment periods (0, 60, 120, 180 days). The cover crops showed a high rate of decomposition of residues in the two years assessed. The legumes presented high initial nutrient contents. The release of N, P, Ca, and Mg was slower. K showed a rapid release from the decomposition of the residues of the assessed cover crops.

Sulfolane in contaminated sites: environmental toxicity and bioremediation technologies

Sulfolane is widely used around the world as an industrial solvent for purifying sour natural gas. However, because of accidental spillage and improper on-site storage/disposal procedures, reports of groundwater, aquifer, and soil contaminations have raised concerns about its potential impacts on humans and the ecosystem. As a contaminant of emerging concern, there is a lack of information on the human toxicity of sulfolane. Several bioremediation technologies have been conducted to assess the biodegradation potential of sulfolane in contaminated groundwater and soils. This review presents and discusses the available literature on the toxicity of sulfolane, which could be useful for developing proper sulfolane guidelines in different media. The oral LD50 of sulfolane varies from 0.6 to 3.5 g·(kg body mass)–1 for different mammalian species, including guinea pig, mouse, rabbit, and rat. In addition, we also review the various sulfolane bioremediation studies to date, highlighting the efficacy of aerobic versus anaerobic bioremediation of sulfolane at contaminated sites. The zero-order biodegradation rate of sulfolane varies from 0.033 to 190 mg·L–1·day–1 depending on the initial concentration of sulfolane, nutrients, oxygen levels, temperature, and other parameters. Effective aerobic treatment technologies can lead to the complete mineralization of sulfolane with sulfuric acid as its major end by-product. Furthermore, the application of aerobic granulation as a promising biotechnology for sulfolane biodegradation is also discussed. This review further discusses the significance of utilizing sulfolane-degrading bacteria to reduce treatment times and presents information for future researchers and scientists on the specific isolates recorded.

Chemotactic movement and zeta potential dominate Chlamydomonas microsphaera attachment and biocathode development

ABSTRACT Microalgal cell attaching and biofilm formation are critical in the application of microalgal biocathode, which severs as one of the hopeful candidates to an original cathode in bioelectrochemical systems. Many efforts have been put in biofilm formation and bioelectrochemical systems for years, but the predominant factors shaping microalgal biocathode formation are sketchy. We launched a pair of researches to investigate microalgal attachment and biofilm formation in the presence/absence of applied voltages using Chlamydomonas microsphaera as a model unicellular motile microalga. In this study, we presented how microalga attached and biofilm formed on a carbon felt surface without applied voltages and try to manifest the most important aspects in this process. Results showed that while nutrient sources did not directly regulate cell attachment onto the carbon felt, limited initial nutrient concentration nevertheless promoted cell attachment. Specifically, nutrient availability did not influence the early stage (20–60 min) of microalgal cell attachment but did significantly impact cell attachment during later stages (240–720 min). Further analysis revealed that nutrient availability-mediated chemotactic movements and zeta potential are crucial to facilitate the initial attachment and subsequent biofilm formation of C. microsphaera onto the surfaces, serving as an important factor controlling microalgal surface attachment. Our results demonstrate that nutrient availability is a dominant factor controlling microalgal surface attachment and subsequent biofilm formation processes. This study provides a mechanistic understanding of microalgal surface attachment and biofilm formation processes on carbon felts surfaces in the absence of applied voltages.

Nutrient Dynamics at the Sediment-Water Interface: Influence of Wastewater Effluents

Uptake and regeneration fluxes and concentrations of nutrients, i.e., nitrate (NO3−), ammonium (NH4+), phosphate (PO43−) and dissolved organic carbon (DOC), were evaluated upstream and downstream of a wastewater treatment plant (WWTP) in the River Wandle, UK, from July to October 2019. Using chamber techniques, water-specific nutrient concentrations were measured at two exposures (3 and 10 min) to calculate fluxes. The WWTP effluent contributed to elevated concentrations and modified flux rates, resulting in significant differences at the study sites. Compared with summer, the concentrations of NO3− and DOC increased while NH4+ and PO43− decreased in autumn. Nutrient fluxes varied both temporally and spatially in uptake (i.e., storage in sediments) or regeneration (i.e., release into river water). Under the actions of physical and biological processes, the fluxes of NO3− and NH4+ showed opposite flux directions. Dissolved oxygen (DO) and bioabsorption mainly affected PO43− and DOC fluxes, respectively. Specifically, across all sites, NO3− was −0.01 to +0.02 mg/(m2 s), NH4+ was −29 to +2 μg/(m2 s), PO43− was −2.0 to +0.5 μg/(m2 s), and DOC was −0.01 to +0.05 mg/(m2 s). Further, we did find that these variations were related to nutrient concentrations in the overlying water. Our results provide further evidence to show that reductions in river nutrients are paramount for improving river ecological conditions. Additionally, we suggest that more research is needed to evaluate chamber-based experimental approaches to make them more comparable to in-situ flux methods.Highlights• Sewage effluent resulted in elevated nutrient concentrations and modified fluxes.• Flux was affected by initial nutrient concentrations, DO and microbial activity.• Inexpensive approaches to study nutrient dynamics are needed for river restoration.

Compatibility and Biomineralization Oriented Optimization of Nutrient Content in Nitrate-Reducing-Biogranules-Based Microbial Self-Healing Concrete

Microbially induced calcium carbonate precipitation (MICP) can be mentioned among the popular approaches to develop a self-healing concrete. The production of dissolved inorganic carbon through microbial activity is the main precursor for MICP in concrete and it is limited by the bioavailability of the nutrients. When nutrients are added to the mortar as admixtures, their bioavailability becomes more significant for crack repair because nutrients disperse in the mortar and considerable fraction stays far from a single crack. Therefore, the determination of bioavailability of nutrients and its variation with the initial nutrient content and crack age is essential to optimize a recipe for bacteria-based self-healing concrete. This study presents the optimum nutrient content defined for nitrate-reduction-based self-healing bioconcrete. In the tests, calcium nitrate (CN) and calcium formate (CF) were combined with a CF:CN w/w ratio of 2.50. Mortar properties and bioavailability of nutrients were analysed at different nutrient doses. Moreover, the bioavailability of nutrients at different crack ages changing between 3 and 56 days was monitored. Finally, resuscitation, microbial activity and the MICP performance of nitrate reducing biogranules were tested at defined nutrient bioavailabilties. The optimum nutrient content was determined as 7.00% (CF 5.00% and CN 2.00%). The leaching rates of formate ions were twice the leaching rate of the nitrate ions at similar initial concentrations, which led to a bioavailable HCOO−/NO3-N ratio of 23 g/g in cracked mortar. Under optimum nutrient conditions, the CaCO3 precipitation yield of nitrate reducing biogranules was recorded as 1.5 g CaCO3/g HCOO− which corresponded to 68% C precipitation efficiency.

Phosphorus recovery from wastewater by struvite in response to initial nutrients concentration and nitrogen/phosphorus molar ratio

Nutrients recovery from wastewater using struvite crystallization has received significant attention because the recovered nutrients can be used as a fertilizer in agriculture. However, the wastewater with different composition of nutrients might exert distinct struvite characteristics. The objective of this study is to explore the influence of nitrogen/phosphorus (N/P) molar ratio and initial nutrient concentrations on the phosphorus (P) recovery from wastewater and the crystallographic properties of struvite through batch experiments. Both the higher nutrients concentrations and N/P molar ratio in the wastewater resulted in higher recovery of P. However, initial nutrients concentration in the wastewater posed a larger effect on the formation of struvite than that of initial N/P ratio. The ratio of N to P consumed during the process varied with varying the N/P ratio or the initial nutrients concentration, indicating the existence of different crystallization mechanisms under different elemental compositions in the wastewater. The decline in solution pH was negatively correlated with the N/P ratio, whereas it was positively correlated with the nutrient concentration. The crystals produced were mainly rough (dendritic) under the N/P ratio of 2, while the morphology evolved from a regular coffin-like to irregular columnar with the increase in N/P ratio from 4 to 10. Meanwhile, the shape of the irregular cylinder gradually changed from elongated needle shape to the thick rods appearance with the increase in the nutrients concentration. Higher N/P ratio increased the nucleation rate, resulting in finer particles and an uneven crystal size distribution, but purer struvite crystals. The purity of struvite was also positively correlated with the initial nutrients concentration. The Visual MINTEQ modelling analysis demonstrated that the supersaturation ratio of struvite gradually increased with the increase in the N/P ratio or nutrients concentration, which led to a positive effect on struvite crystallization.

Soil and Leaf Nutrients Drivers on the Chemical Composition of the Essential Oil of Siparuna muricata (Ruiz & Pav.) A. DC. from Ecuador.

Chemical compositions of plants are affected by the initial nutrient contents in the soil and climatic conditions; thus, we analyzed for the first time the effects of soil and leaf nutrients on the compositions of the essential oils (EOs) of Siparuna muricata in four different localities in Ecuador. EOs were obtained by hydrodistillation and analyzed by gas chromatography/mass spectrometry (GC/MS) and a gas chromatography/flame ionization detector (GC/FID). Enantiomeric distribution by GC/MS was determined, modifying the enantiomeric separation of β-pinene, limonene, δ-elemene, β-bourbonene, cis-cadina-1 (6), 4-diene and atractylone. A total of 44 compounds were identified. The most representative for L1 were guaiol, atractylone and 4-diene; for L2, cis-cadina-1(6),4-diene and myrcene; for L3, atractylone, myrcene and germacrene B; and finally, L4 germacrene B, myrcene and cis-cadina-1(6),4-diene. Correlations between soil- leaf chemical elements such as Al, Ca, Fe, Mg, Mn, N and Si in the different localities were significant with chemical composition of the essential oil of Siparuna muricata; however, correlations between soil and leaf K, P, and Na were not significant. Cluster and NMDS analysis showed high dissimilarity values of secondary metabolites between four localities related with changes in soil- leaf nutrients. Thus, the SIMPER routine revealed that not all secondary metabolites contribute equally to establishing the differences in the four localities, and the largest contributions are due to differences in guaiol, cis-cadina-1(6),4-diene, atractylone and germacrene. Our investigation showed for the first time the influences of altitude and soil- leaf chemical elements in the chemical composition of the EOs of S. muricata.

The Effect of the Polishing Process and Sorghum Type (Brown and White) on the Content of Crackers Nutrition

Yogyakarta - Indonesia has a variety of types of sorghum. Antioxidants and protein are among its nutritional advantages. Processing technology innovation is still needed to optimize its nutrition. Polishing is the main process in sorghum. This study aims to determine the effect of polishing and types of sorghum (brown and white) on the nutritional content of sorghum crackers. Nutrient content analyzed included water, ash, protein, fat, crude fiber, carbohydrate, energy, and beta carotene content. We found that the polishing process of the two types of sorghum resulted in different nutritional advantages of the sorghum crackers. The water, protein, fat, and crude fiber content of sorghum crackers decreased from the initial nutrient content of sorghum grain. Conversely, the content of ash, carbohydrates, and energy increase after becoming crackers. Polishing of white and brown sorghum grain causes higher content of ash, protein, energy, and beta carotene in sorghum crackers compared to unpolished ones. The crackers made from polished white sorghum grain had a higher protein content (7.74%) than those from polished brown sorghum grain (5.71%). The crackers made from polished brown sorghum grain had nutritional advantages in the content of ash (2.78%), energy (333.92 calori/100g) and beta carotene (2134.16mg/100g) compared to crackers made from polished white sorghum grain (2.66%; 317.23 calori/100g; 53.01mg/100g). Polishing of white sorghum grain produces high protein crackers, while polishing of brown sorghum grain produces crackers with high functional beta carotene content.

Collective colony growth is optimized by branching pattern formation in Pseudomonas aeruginosa.

Branching pattern formation is common in many microbes. Extensive studies have focused on addressing how such patterns emerge from local cell–cell and cell–environment interactions. However, little is known about whether and to what extent these patterns play a physiological role. Here, we consider the colonization of bacteria as an optimization problem to find the colony patterns that maximize colony growth efficiency under different environmental conditions. We demonstrate that Pseudomonas aeruginosa colonies develop branching patterns with characteristics comparable to the prediction of modeling; for example, colonies form thin branches in a nutrient‐poor environment. Hence, the formation of branching patterns represents an optimal strategy for the growth of Pseudomonas aeruginosa colonies. The quantitative relationship between colony patterns and growth conditions enables us to develop a coarse‐grained model to predict diverse colony patterns under more complex conditions, which we validated experimentally. Our results offer new insights into branching pattern formation as a problem‐solving social behavior in microbes and enable fast and accurate predictions of complex spatial patterns in branching colonies.

Predicting microbial growth dynamics in response to nutrient availability.

Developing mathematical models to accurately predict microbial growth dynamics remains a key challenge in ecology, evolution, biotechnology, and public health. To reproduce and grow, microbes need to take up essential nutrients from the environment, and mathematical models classically assume that the nutrient uptake rate is a saturating function of the nutrient concentration. In nature, microbes experience different levels of nutrient availability at all environmental scales, yet parameters shaping the nutrient uptake function are commonly estimated for a single initial nutrient concentration. This hampers the models from accurately capturing microbial dynamics when the environmental conditions change. To address this problem, we conduct growth experiments for a range of micro-organisms, including human fungal pathogens, baker’s yeast, and common coliform bacteria, and uncover the following patterns. We observed that the maximal nutrient uptake rate and biomass yield were both decreasing functions of initial nutrient concentration. While a functional form for the relationship between biomass yield and initial nutrient concentration has been previously derived from first metabolic principles, here we also derive the form of the relationship between maximal nutrient uptake rate and initial nutrient concentration. Incorporating these two functions into a model of microbial growth allows for variable growth parameters and enables us to substantially improve predictions for microbial dynamics in a range of initial nutrient concentrations, compared to keeping growth parameters fixed.

Dynamics of leaf litter decomposition in the timberline zone of western Himalaya

Litter decomposition plays a vital role in carbon and nutrient budget of forest ecosystems, but our understanding of this process for high altitude ecosystems, especially the timberline zone, is not very clear. We studied leaf litter decomposition of Betula utilis, which is the main timberline species of Western Himalaya. We placed 144 litterbags (each containing 10 g of oven dried litter) at three ‘spatially well separated sites’ in Oct 2014, to study the direction and magnitude of change in key variables associated with leaf litter decomposition and to test for generality of decomposition process across these spatially distant sites. The results revealed that initial nutrient concentration and lignin content of litter was significantly different for the sites. Further, magnitude of mass loss and decay rate was found to be greater for up to 34 weeks (19.03 ± 4.55% and 0.35 ± 0.06 yr−1 respectively), which reached 47.01 ± 1.98% and 0.17 ± 0.01 yr−1 respectively, after 4 years. N, P and K concentrations showed sharp decease for up to 34 weeks, after which N consistently increased with incubation time, whereas P and K concentrations were relatively stable. The lignin and cellulose contents decreased consistently with incubation time (from 12.29 ± 1.21% to 5.21 ± 0.50% and from 16.87 ± 1.01% to 8.25 ± 0.50% respectively). There were significant increases in C:N and lignin:N ratios for up to 34 weeks, followed by a continuous decrease thereafter. The change in various variables associated with litter decomposition was not consistent among the sites and the magnitude of change was greater during initial stages due to leaching of labile components. The increase in N and decreases in C:N and lignin:N ratios with incubation time might be due to microbial immobilization of N and are important for nutrient conservation in timberline ecosystems, as such changes are related to faster decomposition of recalcitrant fraction of litter, N mineralization and building of soil nutrient pool.

Leaf litter decomposition and nutrient release of three selected agroforestry tree species

Investigation was carried out on leaf litter decomposition and nutrient content of three agroforestry species—Annona muricata L., Senna siamea (Lam.) and Cola nitida (Vent.) using litterbag technique. Oven-dry leaf litters of each species were put in 432 litterbags of 23 g each. These were divided into two sets with one placed on the soil surface (SSP) and another, soil incorporated (SIP). Initial nutrient content (INC), decay constant, half- and full-lives (weeks) were determined. Decomposition rates, nutrient release patterns (NRP) and litter quality were measured fortnightly for 24 weeks after litter placement (WALP). Data collected were subjected to descriptive statistics and ANOVA at α0.05. The INC was significantly different among the species. N concentration decreased from C. nitida A. muricataS. siamea. P was significantly higher in S. siamea (0.38%) than C. nitida (0.22%) and A. muricata (0.32%). Decay constant was highest (0.005) in C. nitida under SIP. Highest half-life (49.5 weeks) and full-life (178.57 weeks) were recorded in S. siamea and C. nitida; and S. siamea and C. nitida under SSP. After 24 weeks, C. nitida had the highest decomposition rate, 5.97 ± 0.0 under SIP. NRP showed that A. muricata and S. siamea had the highest P (0.17%) and cellulose (28.2%) at 24 WALP under SIP. Lignin concentration at 24 WALP was highest in S. siamea (4.35%) and least in C. nitida (0.43%). Decomposition trend and nutrient release pattern from the leaf litters of selected agroforestry species indicated the potential of these leaf litters to offer nutrients on a sustainable basis in an agroforestry system.

Chitin in Strawberry Cultivation: Foliar Growth and Defense Response Promotion, but Reduced Fruit Yield and Disease Resistance by Nutrient Imbalances.

Strawberry cultivation is associated with high mineral fertilizer doses and extensive use of chemical plant protection products. Based on previous research, we expected that chitin application to peat substrate would increase the nutrient availability and activate the plant systemic defense response, resulting in higher strawberry yields and fewer disease symptoms. We set up two experiments in which the temporal variability and differences in initial nutrient concentrations of the growing media were taken into account. Chitin treatment resulted in the attraction of plant growth-promoting fungi toward the plant root, such as species from genera Mortierella and Umbelopsis. In addition, by the end of the experiments 87 mg of mineral nitrogen (N) per liter of substrate was mineralized, which can be related to the observed increase in plant shoot biomass. This, however, led to nutrient imbalances in plant shoots and fruit; N concentration in the leaves increased over 30%, exceeding the optimal range, while phosphorous (P) and potassium (K) deficiencies occurred, with concentrations lower than 50% of the optimal range. This may explain the decreased fruit yield and disease resistance of the fruit toward Botrytis cinerea. In contrast, chitin caused a clear defense priming effect in the strawberry leaves, with a strong induction of the jasmonic acid response, resulting in fewer foliar disease symptoms. Chitin causes positive effects on shoot growth and foliar disease resistance, but caution needs to be taken for nutrient imbalances leading to negative influences on root growth, fruit production, and disease susceptibility toward B. cinerea.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Changes in microbial utilization and fate of soil carbon following the addition of different fractions of anaerobic digestate to soils

AbstractApplying digestate, the residue from anaerobic digestion, to soil as a replacement for inorganic fertiliser is of growing interest in agriculture. However, the impacts of different fractions of digestate on the soil carbon (C) cycle remain unclear and provide the focus for the research reported here. We examined the effects of applying whole digestate (WD) and solid digestate (SD) on carbon dioxide (CO2C) efflux, the concentrations of dissolved organic carbon (DOC), microbial biomass C (Cmicro) and phospholipid fatty acids, alongside carbon use efficiency (CUE). A 21‐day laboratory microcosm incubation was used to investigate the impacts of digestate when applied to two grassland soils of high versus low initial nutrient content. Application rates for SD and WD were based on recommended nitrogen (N) inputs to grassland soils for these organic materials. Compared to control treatments, cumulative CO2C efflux and the concentration of DOC increased significantly after WD and SD application, although only within the low nutrient soil. Both Cmicro and the fungal‐to‐bacterial ratio increased significantly following SD application, regardless of the initial soil nutrient content. These observations are likely to reflect the larger input of C, alongside the dominance of more strongly lignified compounds, associated with SD compared to WD to achieve a constant N application rate. Our results also indicate that the two digestate fractions generated significantly different CUE. The application of SD led to increases in Cmicro and positive values of CUE, whereas decreases in Cmicro and negative values of CUE were observed following WD application. These findings emphasize the need to carefully plan the management of digestate in agricultural production systems, to minimize negative impacts on C storage within soils whilst maximizing the agronomic value derived from digestate.Highlights Past research has not fully elucidated the impacts of digestate fractions on the soil C cycle. Soil nutrient status + digestate fraction shown to impact microbial community and CO2C efflux. Solid digestate fraction has positive impacts on microbial biomass and carbon use efficiency.