Availability Of Mineral Nutrients Research Articles

Microbial Solubilization of Rock Phosphate to Use in Sustainable Agriculture

Microbial solubiliztion is more environmentally sound method of modifying rock phosphate to use in sustainable agriculture as an alternative to chemical acidulation. Therefore, the present study was carried out to find the strategies for microbial solubilization of Eppawala rock phosphate with using biochar and microbial inoculants and effect of these on maize (Zea mays L.) growth and yield. A pot experiment was carried out in the plant house at Faculty of Applied Sciences, Rajarata University of Sri Lanka, Mihintale, during July to December 2015. After searching the literature the following ratios of biochar and RP were selected assuming that the better comparison obtained in different treatments. Treatments were comprised of T1: soil only, T2: sterilized soil and 3% RP, T3: soil and 3% RP, T4: soil, 20% biochar and 3% RP, T5: soil, mycorrhizae and 3% RP, T6: soil, Pseudomonas fluorescens and 3% RP, T7: soil, 20% biochar, mycorrhizae and 3% RP, T8: soil, 20% biochar, P. fluorescens and 3% RP, T9: soil, mycorrhizae, P. fluorescens and 3% RP, and T10: soil, 20% biochar, mycorrhizae, P. fluorescens and 3% RP. The treatments were arranged in a Completely Randomized Block Design (CRBD) with eight replicates. Maize was grown as a test plant. Growth parameters were recorded in four weeks intervals and relative growth rate was estimated. After 120 days of seeding, chemical characteristics and yield parameters were also measured. Results indicated that there was a significant difference among treatments (p<0.05) in all measured parameters over control. The highest available soil phosphorus was observed in biochar, mycorrhizae and P. fluorescens addition with 3% RP (T10) and highest leaf phosphorus was observed in biochar and mycorrhizae with 3% RP (T7). Significantly high (p<0.05) relative growth rate, numbers of leaves, length of leaves, shoot and root dry weights were observed in sterilized soil with 3% RP (T2). This higher growth and yield parameters of T2 may due to soil heating which increases certain soluble mineral nutrients availability. However, growth rate and yield were shown lower in biochar added treatments (T4, T7, T8 and T10). Short term influence of high amount of (20% v/v) biochar alone in plant growth and yield is less. It can be concluded that biochar, mycorrhizae and P. fluorescens are effective in solubilizing the high grade Eppawala rock phosphate. Further, microbial inoculants such as mycorrhizae and P. fluorescens increased the soil P availability and increased P nutrition, growth and yield of maize plants. Keywords: Rock phosphate, biochar, mycorrhizae, Pseudomonas fluorescens, phosphorus availability

Shaping an Optimal Soil by Root-Soil Interaction.

Crop production depends on the availability of water and mineral nutrients, and increased yields might be facilitated by a greater focus on roots-soil interactions. Soil properties affecting plant growth include drought, compaction, nutrient deficiency, mineral toxicity, salinity, and submergence. Plant roots respond to the soil environment both spatially and temporally by avoiding stressful soil environments and proliferating in more favorable environments. We observe that crops can be bred for specific root architectural and biochemical traits that facilitate soil exploration and resource acquisition, enabling greater crop yields. These root traits affect soil physical and chemical properties and might be utilized to improve the soil for subsequent crops. We argue that optimizing root-soil interactions is a prerequisite for future food security.

Phenological and ecophysiological responses of Capsicum annuum var. glabriusculum to native arbuscular mycorrhizal fungi and phosphorus availability

Due to climate change, the assessment of environmental variations associated to phenology and ecophysiology of iconic Sonoran Desert plants such as Capsicum annuum var. glabriusculum (Cag), during their interaction with the native arbuscular mycorrhizal fungi (AMF) and soil nutrients availability, is the keystone to understand its biological significance in the extreme conditions of semiarid environments. Seasonal patterns of high solar radiation regimes and extreme daily air temperatures thresholds were reflected in a high accumulation of heat from physiological maturity (2699°D) until the end of reproduction season (4002°D). In treatments without chemical fertilization, low and intermediate P availability, the native AMFCag inoculum significantly increased Cag’s relative growth rates and changed the biomass allometric allocation patterns causing a lower partition to the roots and a higher partition to the growth of shoots and photosynthetic assimilation surface. Depending on the phenological stage, the levels of P availability and the levels of native AMF propagules in the soil, significantly modified the content of C, H, S, P, N, Ca, Fe, Mn or Ni in the shoots. The native AMFCag inoculum significantly increased the functional colonization (Arum-Paris type) of roots except with higher P availability. However, when AMF propagules in the soil are low, P increase and presence of other mineral nutrients is detrimental to symbiotic establishment. Conversely, when AMF propagules in the soil are high, symbiotic traits indicate that the native AMF taxa tested, have different tolerance capabilities to colonize functionally the roots to obtain the carbon for their development even under a high P and other mineral nutrients availability in the soil. In extreme conditions of sunlight and air temperatures, Cag’s phenological and ecophysiological traits were enhanced by the native AMFCag inoculum in different P availability levels, however, the mycorrhizal growth response decreased significantly as the availability of P increases, and the highest level of native AMF propagules in soil was the factor that promoted the increase of reproductive yield of Cag plants, not the increase of nutrients availability. This study provides novel information on AMF-Cag symbiotic interactions during plant development and phenological stages, as well as proposes different insights and hypothesis of research about Cag-AMF ecophysiology.

Grassland management impacts on soil carbon stocks: a new synthesis.

Grassland ecosystems cover a large portion of Earths' surface and contain substantial amounts of soil organic carbon. Previous work has established that these soil carbon stocks are sensitive to management and land use changes: grazing, species composition, and mineral nutrient availability can lead to losses or gains of soil carbon. Because of the large annual carbon fluxes into and out of grassland systems, there has been growing interest in how changes in management might shift the net balance of these flows, stemming losses from degrading grasslands or managing systems to increase soil carbon stocks (i.e., carbon sequestration). A synthesis published in 2001 assembled data from hundreds of studies to document soil carbon responses to changes in management. Here we present a new synthesis that has integrated data from the hundreds of studies published after our previous work. These new data largely confirm our earlier conclusions: improved grazing management, fertilization, sowing legumes and improved grass species, irrigation, and conversion from cultivation all tend to lead to increased soil C, at rates ranging from 0.105 to more than 1Mg C·ha-1 ·yr-1 . The new data include assessment of three new management practices: fire, silvopastoralism, and reclamation, although these studies are limited in number. The main area in which the new data are contrary to our previous synthesis is in conversion from native vegetation to grassland, where we find that across the studies the average rate of soil carbon stock change is low and not significant. The data in this synthesis confirm that improving grassland management practices and conversion from cropland to grassland improve soil carbon stocks.

Arsenic uptake, accumulation and toxicity in rice plants: Possible remedies for its detoxification: A review.

Arsenic (As) is a toxic metalloid. Serious concerns have been raised in literature owing to its potential toxicity towards living beings. The metalloid causes various water- and food-borne diseases. Among food crops, rice contains the highest concentrations of As. Consuming As-contaminated rice results in serious health issues. Arsenic concentration in rice is governed by various factors in the rhizosphere such as availability and concentration of various mineral nutrients (iron, phosphate, sulfur and silicon) in soil solution, soil oxidation/reduction status, inter-conversion between organic and inorganic As compounds. Agronomic and civil engineering methods can be adopted to decrease As accumulation in rice. Agronomic methods such as improving soil porosity/aeration by irrigation management or creating the conditions favorable for As-precipitate formation, and decreasing As uptake and translocation by adding a inorganic nutrients that compete with As are easy and cost effective techniques at field scale. This review focuses on the factors regulating and competing As in soil-plant system and As accumulation in rice grains. Therefore, it is suggested that judicious use of water, management of soil, antagonistic effects of various inorganic plant-nutrients to As should be considered in rice cultivated areas to mitigate the building up of As in human food chain and with minimum negative impact to the environment.

Chemical Properties of Biochar Materials Manufactured from Agricultural Products Common to the Southeast United States

The use of biochar as a soil amendment has fostered much attention in recent years due to its potential of improving the chemical, physical, and biological properties of agricultural soils and/or soilless substrates. The objective of this study was to evaluate the chemical properties of feedstocks, common in the southeast United States, and their resulting biochar products (after being torrefied) and determine if the chemical properties were within suitable ranges for growers to use the biochar products as root substrate components. Poultry litter biochar produced at 400 °C for 2 hours had a higher total phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), chloride (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), sodium (Na), and zinc (Zn) concentration than biochar made using the same process with mixed hard wood species, miscanthus (Miscanthus capensis), cotton (Gossypium hirsutum) gin trash, switchgrass (Panicum virgatum), rice (Oryza sativa) hull, and pine (Pinus sp.) shavings feedstocks. The pH of the biochar products ranged from 4.6 for pine shaving biochar to 9.3 for miscanthus biochar. The electrical conductivity (EC) ranged from 0.1 dS·m−1 for mixed hardwood biochar to 30.3 dS·m−1 for poultry litter biochar. The cation exchange capacity (CEC) of the biochar products ranged from a low of 0.09 meq/g for mixed hardwood biochar to a high of 19.0 meq/g for poultry litter biochar. The water-extractable nitrate, P, K, Ca, Mg, sulfate, boron, Cl, Cu, Fe, Mo, Na, and Zn were higher in poultry litter biochar than in all of the other types of biochar. The high EC and mineral element concentration of the poultry litter biochar would prevent its use in root substrates except in very small amounts. In addition, the high degree of variability in chemical properties among all of the biochar products would require users to know the specific properties of any biochar product they used in a soil or soilless substrate. Modifications to traditional limestone additions and fertility programs may also need to be tested and monitored to compensate for the biochar pH and mineral nutrient availability. Users should be aware that biochar products made from different feedstocks can have very different chemical properties even if the same process was used to manufacture them.

Response of the Coral Associated Nitrogen Fixing Bacteria Toward Elevated Water Temperature

Coral reefs are among the most biologically diverse and economically important ecosystem on the planet. Despite the importance, reef habitat is being under threat from human exploitation, and its most serious stressor is increasing seawater temperature, an aftermath of global warming phenomenon. The increasing seawater temperature causes bleaching, diseases and insufficiency of nutrients of corals. Despite being surrounded by ocean waters were nutrient are in short supply, the reef ecosystem is a significant source of new nitrogen. Biological nitrogen fixation is a significant internal source of marine organism. The growth of all organism lies on the availability of mineral nutrients particularly of nitrogen (N 2 ). Approximately 80% of atmosphere is made of nitrogen, however, N 2 can only be available for use by organism unless it undergoes a process of nitrogen fixation. In this aspect, related literature on biological nitrogen fixation seems sparse especially on the effects of increasing seawater temperature, a well-known contributing factor of coral bleaching. In this study, an investigation was conducted on nitrogen fixing bacterial communities associated in the coral Acropora digitifera , exploring its responses towards elevated water temperature. The study shows that exposure to high temperature causes a drastic change in the community of nitrogen fixing bacteria which are abundant in coral mucus. These changes, is correlated with the shift in the metabolic function in coral holobiont, thus, affecting both health and resiliency of corals. Overall, the finding highlights the impact of elevated seawater temperature on the nitrogen fixing bacterial composition and its diversity as well as its effects of this on host metabolism.

Dampened copepod‐mediated trophic cascades in a microzooplankton‐dominated microbial food web: A mesocosm study

AbstractInteractions of bottom‐up factors such as the availability of mineral and organic nutrients, and top‐down factors like predation and viral infection affect microbial communities of the pelagic food web. Hypothesis derived from previous experimental and modeling work suggest some general mechanisms on how these factors may be linked and call for an experiment to test interactions between (1) nitrogen source and diatom cell size, (2) bacterial growth rate limitation by mineral nutrients versus organic carbon, and (3) enhanced versus decreased predation pressure by copepods (Calanus finmarchicus). We performed a mesocosm experiment using a replicated three factor––two level full factorial design ( / , +/− glucose, and +/− copepods). Diatoms, pico‐ and nano‐sized autotrophs, prokaryotes, heterotrophic nanoflagellates, micro‐ and mesozooplankton abundances were monitored for 19 days. The main finding was a system that responded remarkably little to these manipulations with no effects of nitrogen source and only moderate effects of carbon treatments. Zooplankton manipulations had the strongest impact on microbial communities, but, opposite to our hypothesis based on previous studies, microzooplankton and diatoms increased during the first 7–10 days when mesozooplankton abundances were experimentally enhanced. We suggest that high abundances of dinoflagellates and ciliates and occurrence of rotifers, which dominated microzooplankton community in the first half of the experiment complicated trophic linkages between copepods, microzooplankton and diatoms. Apart from this dampened copepod mediated trophic cascade, we found tight couplings between communities of the microbial food web, with maxima of predator communities coinciding with low abundances of prey communities.

Nutrient uptake and use efficiency in co‐occurring plants along a disturbance and nutrient availability gradient in the boreal forests of the southwest Yukon, Canada

AbstractAimIn boreal forest ecosystems plant productivity is typically constrained by mineral nutrient availability. In some boreal regions changes in nutrient availability have led to limited changes in productivity but large changes in plant composition. To determine the impact that a change in nutrient availability has on the plant communities it is important to understand how species use nutrients. Here we explore how plant species and functional types in a cold‐dry boreal forest community use available nutrients by quantifying their respective nutrient utilization and response efficiency.LocationBoreal forests in the southwest corner of the Yukon Territory, Canada.MethodsWe collected soil samples and total plant biomass from 29 plots from nine locations subjected to fire, harvesting or bark beetle disturbances. Nutrient analysis of all vegetation and soil samples were conducted to determine the concentration of macro‐ and micronutrients from both plant biomass and soils collected. Nutrient pools between stands with different disturbance histories are compared. Nutrient uptake, use and response efficiencies were then calculated and nutrient response profiles were developed for each species/functional type.ResultsWe found few differences between nutrient pools in plots with different disturbance histories. A clear separation of species and functional groups in elemental hyperspace suggesting divergent nutrient use in co‐occurring species was identified. The use efficiency analysis highlighted that the species with the highest uptake efficiency have lowest use efficiency and vice versa. Species showed either a monotonic or constant relationship between nutrient response efficiency and N, P, K, reflecting a lack of relationship between plant productivity and resource availability or a linear increase in productivity with increasing nutrient availability, respectively.ConclusionsOur findings indicate that species are maximizing nutrient use along different parts of the resource gradient, which has implications for understanding how species respond to changes in nutrient availability. Our findings also show that nutrient use by some species may be governed more by uptake efficiency than use efficiency, allowing them to respond to increases in resource availability by increasing uptake rather than use.

Sustainable orchard management in semi-arid areas to improve water use efficiency and soil fertility

Due to the impact of climate changes (mainly increased temperature and precipitation changes) as combined with poor orchard management (e.g., continuous tillage, use of mineral fertilisers) on soil fertility, orchard management should be revised. Improvement of orchard management practices aimed at increasing soil fertility traits (e.g., soil organic carbon, microbial community, soil porosity) will be beneficial for soil conservation and also for improvement of water use efficiency at farm scale through improved soil water holding capacity. This paper mainly focuses on some effects on orchards grown under semi-arid environment of changed soil management practices from conventional (soil tillage, mineral fertilisers, burning of pruning residues) to sustainable (no-tillage, pruning residues and cover crop retention, compost application) on soil microbial biomass, organic carbon (SOC), mineral nutrients availability and water use efficiency. Results show that a 7/10-year period of changed practices significantly increased SOC concentration and soil microbial biomass at Mediterranean fruit tree orchards and that yield was improved by 30-50% as compared with that recorded in conventional managed orchards. The positive effect of carbon addition on reserves of soil nutrients (N, P, K, Ca, Mg) is also reported. Seasonal volumes of irrigation water are reduced by ∼30% in orchards under sustainable management practices, contributing to improve water use efficiency.

Mg deficiency affects leaf Mg remobilization and the proteome in Brassica napus

In order to cope with variable mineral nutrient availability, higher plants have developed numerous strategies including the remobilization of nutrients from source to sink tissues. However, such processes remain relatively unknown for magnesium (Mg), which is the third most important cation in plant tissues. Using Mg depletion of Brassica napus, we have demonstrated that Mg is remobilized from old leaves to young shoot tissues. Moreover, this study showed that Mg depletion induces modification of nutrient uptake, especially Zn and Mn. Finally, comparative proteomic analysis of old leaves (source of Mg) revealed amongst other results that some proteins requiring Mg for their functionality (isocitrate dehydrogenase for example) were up-regulated. Moreover, down-regulation of proteases suggested that mobilization of Mg from old leaves was not associated with senescence.

Poplar growth and wood production on a grassland irrigated for decades with potato starch wastewater

Irrigation of grasslands with potato starch wastewater causes changes in soil quality parameters, often resulting in decreased crop yields and sometimes causing animal diseases. Reduced agricultural income leads to designation of such grasslands for afforestation aimed at production of bioenergy crops and improvement of soil quality. In this study, Populus alba L. and seven different poplar clones were planted in 2009 on the grassland irrigated in 1973–2008 with potato starch wastewater and in non-irrigated, experimental forest. The survival, growth and wood production potential of planted poplars after 2–3 growing seasons were analyzed. Morphophysiological parameters of leaves, nutrients in leaves and fine roots, sugars in fine roots, leaf rust resistance, frost hardiness and their effects on growth were also determined. Stem diameter and stem volume index of poplars growing on the grassland were higher than in the experimental forest. Only Populus deltoides Bartr. × P. maximowiczii Henry clone ‘Eridano’ (in short ERI) had a survival rate of 100 % and the highest values of stem diameter (77 mm) and stem volume index (0.034 m3) in comparison with other poplars in both sites after 3 growing seasons. Clone ERI was also characterized by a high leaf rust resistance and frost hardiness. The results suggest that clone ERI is suitable as a bioenergy crop on grasslands irrigated with potato starch wastewater. Afforestation of the grassland improved the fertility of the soil by increasing concentrations of soil organic matter and availability of mineral nutrients (N, P, K, S and Fe).

Impairment of Respiratory Chain under Nutrient Deficiency in Plants: Does it Play a Role in the Regulation of Iron and Sulfur Responsive Genes?

Plant production and plant product quality strongly depend on the availability of mineral nutrients. Among them, sulfur (S) and iron (Fe) play a central role, as they are needed for many proteins of the respiratory chain. Plant mitochondria play essential bioenergetic and biosynthetic functions as well as they have an important role in signaling processes into the cell. Here, by comparing several transcriptomic data sets from plants impaired in their respiratory function with the genes regulated under Fe or S deficiencies obtained from other data sets, nutrient-responsive genes potentially regulated by hypothetical mitochondrial retrograde signaling pathway are evidenced. It leads us to hypothesize that plant mitochondria could be, therefore, required for regulating the expression of key genes involved both in Fe and S metabolisms.

H+-pyrophosphatase from Salicornia europaea enhances tolerance to low phosphate under salinity in Arabidopsis

ABSTRACTIncreasing soil salinity threatens crop productivity worldwide. High soil salinity is usually accompanied by the low availability of many mineral nutrients. Here, we investigated the potential role that the H+- PPase could play in optimizing P use efficiency under salinity in plants. Transgenic Arabidopsis plants overexpressing either SeVP1 or SeVP2 from Salicornia europaea outperformed the wild-types under low phosphate (Pi) as well as low Pi plus salt conditions. Our results suggested that H+-PPase could increase external Pi acquisition through promoting root development and upregulating phosphate transporters, thus to protect plants from Pi limiting stress. This study provides a potential strategy for improving crop yields challenged by the co-occurrence of abiotic stresses.

Povecanje nutritivnog kvaliteta soje pomocu nestandardnih folijarnih dubriva

Deficiencies of mineral elements in human nutrition could be surpassed by crop fortification. One of the prevalent measures of fortification is foliar fertilization. The aim of this study was to determine the content and availability of the mineral nutrients Mg, Fe and Zn, together with phytate, as an anti-nutritive factor, and β-carotene as a promoter of mineral nutrient availability in grain of two soybean cultivars (Nena and Laura) treated with different non-standard foliar fertilizers (mainly based on plant extracts). Generally, a negative correlation between Fe and phytate indicated that factors which decrease phytate and increase β-carotene could be primarily responsible for Fe utilization by humans and animals. Zlatno inje (based on manure) had the highest impact on increasing the grain yield and decreasing the ratios between phytate and mineral elements in Nena grain, while for Laura, it was generally Zircon (based on an extract of Echinacea purpurea L), increasing also availability of mineral elements.

Mistletoe (Viscum album) reduces the growth of the Scots pine by accumulating essential nutrient elements in its structure as a trap

We found mistletoe accumulates nutrient elements in its structure as a trap and causes a severe drought stress in the Scots pine in dry summer seasons. The mistletoe [Viscum album ssp. austriacum (Wiesbaur) Vollm.] is a hemiparasitic plant, and its infestation is known to play an important role on the mortality of Scots pines (Pinus sylvestris L.), but there is little knowledge about its action mechanism. This study, therefore, tried to gain a better understanding of the destructive effect of the mistletoe on the growth and water uptake mechanism of the Scots pine. Identical needles from neighboring plants (healthy and infested) were harvested in the middle of each month (from April to October 2013) and used as research material. Infestation success of the mistletoe was investigated by evaluating the contents of the endogenous nutrient elements such as potassium, phosphorus, calcium, sulfur, magnesium, iron, copper, zinc, manganese, boron, nickel, and sodium in both mistletoe leaves and the needles of healthy and infested Scots pine. Its effects were also evaluated by determining the content of water, chlorophyll, and dry matter, and the length of the newly formed needles of the healthy and infested trees. Mistletoe infestation led to a decrease in the availability of water and mineral nutrients, and caused a powerful inhibition on the growth parameters such as chlorophyll, dry matter, and the length of needles by accumulating the essential nutrient minerals in its structure. The findings of this study indicate that the mistletoe accumulates the nutrient elements in its structure as a trap and causes a severe drought stress in the Scots pine in dry summer seasons, thereby playing a potent role in the increasing mortality rate in the Scots pine.

Relative Roles of Soil Moisture, Nutrient Supply, Depth, and Mechanical Impedance in Determining Composition and Structure of Wisconsin Prairies.

Ecologists have long classified Midwestern prairies based on compositional variation assumed to reflect local gradients in moisture availability. The best known classification is based on Curtis’ continuum index (CI), calculated using the presence of indicator species thought centered on different portions of an underlying moisture gradient. Direct evidence of the extent to which CI reflects differences in moisture availability has been lacking, however. Many factors that increase moisture availability (e.g., soil depth, silt content) also increase nutrient supply and decrease soil mechanical impedance; the ecological effects of the last have rarely been considered in any ecosystem. Decreased soil mechanical impedance should increase the availability of soil moisture and nutrients by reducing the root costs of retrieving both. Here we assess the relative importance of soil moisture, nutrient supply, and mechanical impedance in determining prairie composition and structure. We used leaf δ13C of C3 plants as a measure of growing-season moisture availability, cation exchange capacity (CEC) x soil depth as a measure of mineral nutrient availability, and penetrometer data as a measure of soil mechanical impedance. Community composition and structure were assessed in 17 remnant prairies in Wisconsin which vary little in annual precipitation. Ordination and regression analyses showed that δ13C increased with CI toward “drier” sites, and decreased with soil depth and % silt content. Variation in δ13C among remnants was 2.0‰, comparable to that along continental gradients from ca. 500–1500 mm annual rainfall. As predicted, LAI and average leaf height increased significantly toward “wetter” sites. CI accounted for 54% of compositional variance but δ13C accounted for only 6.2%, despite the strong relationships of δ13C to CI and CI to composition. Compositional variation reflects soil fertility and mechanical impedance more than moisture availability. This study is the first to quantify the effects of soil mechanical impedance on community ecology.

Vermicompost from municipal sewage sludge affects growth and mineral nutrition of winter rye (Secale cereale) plants

ABSTRACTThe aim of the study was to investigate sewage sludge vermicompost application effects on growth and mineral nutrition of winter rye (Secale cereale L.) plants as compared to two initial levels of mineral nutrient availability, pure sand and sand enriched with inorganic nutrients at the optimal level. Addition of sewage sludge vermicompost significantly inhibited rye seed germination at 20 to 50% sand substitution independently on mineral nutrient supplement. Growth inhibition was evident at early stages of plant development. However, at the later stages, sewage sludge vermicompost acted both as mineral fertilizer and plant growth-promoting agent. Significant stimulation of mineral uptake was seen only at high rates of vermicompost substitution (40 and 50%) already causing decrease in shoot dry matter accumulation. Vermicompost substitution resulted in a significant increase of leaf chlorophyll content. Beneficial effect of sewage sludge vermicompost in conditions of optimal mineral supply can result mainly from plant growth-promoting activity.

Interspecific competition in phytoplankton drives the availability of essential mineral and biochemical nutrients.

The underlying mechanisms and consequences of competition and diversity are central themes in ecology. A higher diversity of primary, producers often results in higher resource use efficiency in aquatic and terrestrial ecosystems. This may result in more food for consumers on one hand, while, on the other hand, it can also result in a decreased food quality for consumers; higher biomass combined with the same availability of the limiting compound directly reduces the dietary proportion of the limiting compound. Here we tested whether and how interspecific competition in phytoplankton communities leads to changes in resource use efficiency and cellular concentrations of nutrients and fatty acids. The measured particulate carbon: phosphorus ratios (C:P) and fatty acid concentrations in the communities were compared to the theoretically expected ratios and concentrations of measurements on simultaneously running monocultures. With interspecific competition, phytoplankton communities had higher concentrations of the monounsaturated fatty acid oleic acid and also much higher concentrations of the ecologically and physiologically relevant long-chain polyunsaturated fatty acid eicosapentaenoic acid than expected concentrations based on monocultures. Such higher availability of essential fatty acids may contribute to the positive relationship between phytoplankton diversity and zooplankton growth, and may compensate limitations by mineral nutrients in higher trophic levels.

English

Earthworms are regarded as the bio-indicators of soil quality. Also, due to several beneficial ecosystem services provided by earthworms, focus has been given to earthworms in agriculture management. So, there is need of knowing the distribution of earthworms, factors affecting their distribution and modification of soil environment due to them. With the aim of characterizing earthworm distribution in Panchase area, earthworms were sampled in different aspects, land use types, depth and altitude in June and October. Soil sample was also taken to characterize the habitat preference of the earthworms. The highest earthworm population density was found in forest followed by agriculture land and grassland in both months. Also, majority of earthworms were found in top 15 cm of soil. Moisture and organic matter content were found to be major determinants of earthworm population in Panchase area. Positive and significant correlation between earthworm population and available mineral nutrients (P and K) suggests that earthworms help in mineral nutrient availability to the plants. &nbsp; Key words: Ash free dry mass, biomass, earthworm population density, Panchase area.