Plant Nutrient Availability Research Articles

Recycling lake sediment to agriculture: Effects on plant growth, nutrient availability, and leaching

Sediment removal from eutrophicated shallow lakes may not only be an effective method for lake restoration but also provides the potential for recycling nutrients from sediments to crop production. However, finding a suitable strategy for sustainably reusing the sediment remains a challenge. Therefore, current study focused on the best practices in applying the sediment from a shallow eutrophicated lake to the soil in terms of grass yield, nutrient uptake, and nutrient leaching. During a nine-month lysimeter experiment, 100-cm high columns were filled with six combinations of soil, sediment, and biochar, with or without meat bone meal organic fertilizer. Aboveground biomass, root mass distribution in soil, nutrient concentration, phosphorus (P) uptake of perennial ryegrass (Lolium perenne L.) along with easily soluble nutrients in the growing medium, and leached mineral nitrogen (N) and P levels were measured. Plant growth conditions were improved by sediment additions, as the yield and P uptake of ryegrass nearly doubled in treatments containing sediment compared to the control soil. While the sediment was richer in macro and micronutrients (e.g. P and N) compared to the soil, the leached N and P levels from both treatments were almost equivalent (N < 830 mg m−2 and P < 3 mg m−2). In addition, applying a 2-cm layer of biochar between the sediment and soil reduced P and N leaching by 50%. According to the results, applying a 75-cm thick layer of sediments on agricultural sandy loam soils surrounding the lake seems a promising practice for improving plant yield and soil nutrient status without increasing of P and N leaching from soil.

Sustaining the growth of Pinaceae trees under nutrient-limited edaphic conditions via plant-beneficial bacteria.

Lodgepole pine, a prominent Pinaceae tree species native to western North America, is well-known for its ability to thrive in highly disturbed and degraded areas. One such area is the Sub-Boreal Pine-Spruce xeric-cold (SBPSxc) region in British Columbia, Canada, which is characterized by weakly-developed, parched soils that lack an organic forest floor and essential plant-available nutrients. We hypothesized that plant growth-promoting bacteria could play a significant role in sustaining the growth of lodgepole pine trees in the SBPSxc region. Testing this hypothesis, we evaluated plant growth-promoting abilities of six endophytic bacterial strains previously isolated from lodgepole pine trees growing in this region. These bacterial strains significantly enhanced the length and biomass of their natural host (lodgepole pine) as well as a foreign host (hybrid white spruce) in a 540-day long greenhouse trial. This growth stimulation could be linked to the diverse plant growth-promoting (PGP) abilities detected in these strains using in vitro assays for inorganic/organic phosphate-solubilization, siderophore production IAA production, ACC deaminase activity, lytic enzymes (chitinase, β-1,3-glucanase, protease, and cellulase) activity, ammonia production and catalase activity. ACC deaminase activity was also detected in vivo for all strains using ethylene-sensitive plants–canola and tomato. Notably, strains belonging to the Burkholderiaceae family (HP-S1r, LP-R1r and LP-R2r) showed the greatest potential in all PGP assays and enhanced pine and spruce seedling length and biomass by up to 1.5-fold and 4-fold, respectively. Therefore, such bacterial strains with multifarious PGP abilities could be crucial for survival and growth of lodgepole pine trees in the SBPSxc region and could potentially be utilized as bioinoculant for Pinaceae trees in highly disturbed and nutrient-poor ecosystems.

Animal body size distribution influences the ratios of nutrients supplied to plants

Nutrients released through herbivore feces have the potential to influence plant-available nutrients and affect primary productivity. However, herbivore species use nutrients in set stoichiometric ratios that vary with body size. Such differences in the ratios at which nutrients are used leads to differences in the ratios at which nutrients are deposited through feces. Thus, local environmental factors that affect the average body size of an herbivore community (such as predation risk and food availability) influence the ratios at which fecal nutrients are supplied to plants. Here, we assess the relationship between herbivore body size and the nitrogen-to-phosphorus ratios of herbivore feces. We examine how shifts in the average body size of an herbivore community alter the ratios at which nitrogen and phosphorus are supplied to plants and test whether such differences in the stoichiometry of nutrient supply propagate through plants. We show that dung from larger-bodied herbivores contain lower quantities of phosphorus per unit mass and were higher in N:P ratio. We demonstrate that spatial heterogeneity in visibility (a proxy for predation risk and/or food availability) and rainfall (a proxy for food availability), did not affect the overall amount of feces deposited but led to changes in the average body size of the defecating community. Feces deposited in areas of higher rainfall and reduced visibility originated from larger herbivores and were higher in N:P ratios. This indicates that processes that change the size distribution of herbivore communities, such as predation or size-biased extinction, have the potential to alter the nutrient landscape for plants.

Quality of Enriched Liquid Organic Fertilizer from Dairy Cattle Wastes on Closed Agriculture System

Liquid organic fertilizer (LOF) supplementation for solid organic fertilizer can accelerate the availability of plant nutrients. However, the nutrient content of LOF is highly dependent on its sources. The objective of the experiment was to examine the nutrient content of enriched liquid organic fertilizer from dairy cattle wastes. The experiment was conducted at Closed Agriculture Production System Research Station located in Air Duku Village, Bengkulu, Indonesia, at 1054 m above sea level. The experiment was laid out in a Completely Randomized Design with ten treatments and three replications. The treatments consisted of LOF from dairy cattle wastes enriched with Tithonia diversifolia, Ageratum conyzoides, Leucaena leucocephala, and Gliricidia sepium, their combination with phosphate rock, the combination of Tithonia diversifolia, and Ageratum conyzoides, and control. The LOF solution was anaerobically incubated for six weeks. The experiment indicated that during the incubation, solution pH declined for the first two weeks, gradually increased up to week 6. At the end of incubation, control exhibited the highest pH as compared to those with enrichment, indicating that decomposition of green biomass released a considerable amount of hydrogen. Enrichment of LOF considerably increased the contents of C, N, P, K, Ca, and Mg. The addition of phosphate rock to biomasses did not contribute a prominent increase in phosphorus content, possibly due to its low solubility at high pH. LOF enrichment with Tithonia diversifolia and Ageratum conyzoides had the highest N, P, and Mg contents. Therefore, the enrichment is the most potential for LOF production in closed agriculture system.

Soil Fertility Assessment of Semiarid Soils from Nigeria Cropped to Sorghum

The aim of this study is to characterize the fertility status of the Dingyadi soils from semiarid Northern Nigeria, by using different methods of extraction to assess the potential for soil available macro and micronutrients to the sorghum crop. The study also compared concentrations of extractable nutrients between extractants for ascertaining the possibility of using one method to quantify a variety of plant-available nutrients in soils. Surface (0-15 cm) and sub-surface (15-30 cm) soil samples were collected along a topo-sequence at Dingyadi Sokoto-Nigeria, where sorghum had been grown, to characterize the soil chemical and physical properties that can influence soil fertility for sorghum production. The topo-sequence consisted of valley floor (TLL1), middle (TUP2), and crest (TUP3) positions of the slope. At each position 60 concentrations of each plant nutrient were used for the comparisons.Soil extraction for nutrients was carried out at the Environmental Soil Physics laboratory, Soil and Water Sciences Department, University of Florida, while analysis of aliquots for the elements was carried out at the Southwest Florida Research and Education Center, Immokalee, Florida. The study was carried out over a period of eight months, in 2016-2017. Soil samples were extracted using different extraction methods (Mehlich-3, Bray-1, Ammonium acetate, and DI-Water). A soil to solution ratio of 1:1 was used across all extraction methods to facilitate comparison between methods. However, a test was carried out to examine the effect of soil to solution ratio of (1:10) on extractable macro nutrients using Mehlich3 for randomly selected soil samples across the topo-sequence. Soil samples were also analyzed for texture, pH, organic matter, and cation exchange capacity (CEC). All soil soils were sandy, low in organic matter content, and CEC.With respect to sorghum production, the soils had adequate nutrients (Mg, Ca, K, and P) and soil pH. All soil samples contained no exchangeable K. Mehlich3 extracted higher available P than Bray1 in TLL1, but equal amounts in TUP2 and TUP3. Good correlations exist between extracting methods for macro nutrients (Mg, Ca, K, and P). Bray1 method used for available P is not suitable for soils that have pH greater than 7 determined in water. Mehlich3 is more suitable for the semiarid soils of Northern Nigeria that are acidic or alkaline. The Mehlich3 method should be calibrated with yield response of crops to substitute for Bray1 available phosphorus. Also, Mehlich3 method could be used for the multi-nutrient test with a good correlation with other methods like ammonium acetate for exchangeable bases.

The Effect of Leaching Fraction-Based Irrigation on Fertilizer Longevity and Leachate Nutrient Content in a Greenhouse Environment

An experiment was conducted to evaluate the effects of leaching fraction (LF) on the longevity of controlled-release fertilizer (CRF) and leachate nutrient content in a pine bark substrate. The effect of LF-based irrigation was evaluated under six target LFs of 0.05, 0.15, 0.25, 0.35, 0.45, and 0.55. The 2.72 L nursery pots were filled with 100% pine bark substrate amended with dolomitic lime at a rate of 2.97 kg/m3 and Harrell’s 16-6-13 POLYON® applied at a rate of 6 g per container. Fertilizer was encased in vinyl-coated fiberglass mesh bags and subdressed 2.5 cm under the substrate surface for recovery at the end of 10 weeks. The total amount of nutrients leached from the container was greater at higher LFs, with twice as much inorganic nitrogen leached at a LF of 0.55 than a 0.15 LF. The amount of dissolved nutrients left in the substrate decreased as the LF treatments increased. There were 29.6% more inorganic nitrogen and 37.7% more phosphorus left in the substrate irrigated with a 0.15 LF as compared to a 0.55 LF. This suggests that at lower LFs, more dissolved nutrients may be available for plant uptake. No differences were seen in the amount of nutrients lost from the CRF or remaining in the prills. Results indicate that reducing the LF did not influence the longevity of POLYON® CRF in a pine bark substrate, but that a lower LF may be useful in reducing nutrient runoff into the environment. Targeting a lower LF also resulted in a larger pool of plant-available nutrients, allowing nursery producers to potentially reduce fertilizer rates.

Effects of Low pH of Hydroponic Nutrient Solution on Plant Growth, Nutrient Uptake, and Root Rot Disease Incidence of Basil (Ocimum basilicum L.)

Rootzone pH affects nutrient availability for plants. Hydroponic leafy greens are grown in nutrient solutions with pH 5.5 to 6.5. Lower pH may inhibit plant growth, whereas pathogenic oomycete growth and reproduction may be mitigated. General understanding of pH effects on nutrient availability suggests likely toxicity and deficiency of specific micronutrients. We hypothesized that if adjustments are made to the micronutrient concentrations in solution, plants will grow in lower-than-conventional pH without nutrient disorders, while oomycete disease incidence and severity may be reduced. To develop a new nutrient solution management strategy, we examined pH of 4.0, 4.5, 5.0, and 5.5 with or without micronutrient adjustments for growing two cultivars of basil plants Dolce Fresca and Nufar in a greenhouse hydroponic deep-water culture (DWC) system. Micronutrient adjustments included reduced concentrations of copper, zinc, manganese, and boron by one-half and doubled molybdenum concentration. Plants harvested 20 to 28 days after transplanting did not show significant effects of pH or the micronutrient adjustment. Phosphorus, calcium, magnesium, sulfur, boron, manganese, and zinc concentrations in leaves significantly declined, while potassium and aluminum concentrations increased with decreasing pH. However, these changes and therefore micronutrient adjustments did not affect basil plant growth significantly. ‘Nufar’ basil plants were then grown in a growth chamber DWC system at pH 4.0 or a conventional 5.5 with and without inoculation of Pythium aphanidermatum zoospores. Fourteen days after inoculation, P. aphanidermatum oospore production was confirmed only for the inoculated plants in pH 5.5 solution, where a significant reduction of plant growth was observed. The results of the present study indicate that maintaining nutrient solution pH at 4.0 can effectively suppress the severity of root rot caused by P. aphanidermatum initiated by zoospore inoculation without influencing basil growth.

Understanding stoichiometric mechanisms of nutrient retention in wetland macrophytes: stoichiometric homeostasis along a nutrient gradient in a subtropical wetland

Nutrient homeostasis relates ambient stoichiometric conditions in an environment to the stoichiometry of living entities of that ecosystem. Plant nutrient sequestration in wetland ecosystems is a key process for downstream water quality. However, few studies have examined stoichiometric homeostasis of aquatic vegetation despite the importance of stoichiometry to plant nutrient uptake efficiency. This study investigated stoichiometric homeostasis of dominant emergent and submerged aquatic vegetation (EAV and SAV, respectively) within two treatment flow-ways of Everglades Stormwater Treatment Area 2 (STA-2). These flow-ways encompass a large gradient in plant nutrient availability. This study hypothesizes that wetland vegetation is homeostatic relative to ambient nutrients and consequently nutrient resorption does not vary along the nutrient gradient. We developed a framework to investigate how vegetation uptake and resorption of nutrients contribute separately to homeostasis. Overall, we determined that the wetland vegetation in this study was non-homeostatic with respect to differential uptake of nitrogen (N) versus phosphorus (P). In EAV, P resorption was relatively high and N resorption was moderate, and resorption efficiency did not vary significantly along the gradient. In separating the proportional contribution of resorption and uptake to the degree of homeostasis, resorption did not affect overall homeostatic status in EAV.

Nutrient removal potential and biomass production by Phragmites australis and Typha latifolia on European rewetted peat and mineral soils

Paludiculture, sustainable and climate-smart land use of formerly drained, rewetted organic soils, can produce significant biomass in peatlands whilst potentially restoring several additional wetland services. However, the site conditions that allow maximum biomass production and nutrient removal by paludiculture crops have rarely been studied.We studied the relationship between soil characteristics, including plant-available nutrients, peak biomass, stand age, harvest period, and nutrient removal potential for two important paludiculture species, Typha latifolia and Phragmites australis, on rewetted peat and mineral soils in a large-scale European survey.T. latifolia and P. australis were able to produce an aboveground peak biomass of 10–30 t dry matter ha−1 y−1 and absorbed significant amounts of carbon, nitrogen, phosphorus, and potassium in stands older than 3 years. They were able to grow in a wide range of abiotic soil conditions. Low N:P ratios (5–9) and low N content (< 2%) in T. latifolia tissue suggest N limitation, but P uptake was still surprisingly high. P. australis had higher N:P ratios (8–25) and was less responsive to nutrients, suggesting a higher nutrient use efficiency. However, both species could still produce significant biomass at lower nutrient loads and in winter, when water content was low and nutrient removal still reasonable.Based on this European wetland survey, paludiculture holds a great potential to combine peat preservation, water purification, nutrient removal, and a high biomass production. Paludicrops take up substantial amounts of nutrients, and both summer and winter harvests provide an effective way to sequester carbon in a range of high-valued biomass products and to control nutrient effluxes from rewetted sites at the landscape scale.

Domestication-driven changes in plant traits associated with changes in the assembly of the rhizosphere microbiota in tetraploid wheat

Despite the large morphological and physiological changes that plants have undergone through domestication, little is known about their impact on their microbiome. Here we characterized rhizospheric bacterial and fungal communities as well as the abundance of N-cycling microbial guilds across thirty-nine accessions of tetraploid wheat, Triticum turgidum, from four domestication groups ranging from the wild subspecies to the semi dwarf elite cultivars. We identified several microbial phylotypes displaying significant variation in their relative abundance depending on the wheat domestication group with a stronger impact of domestication on fungi. The relative abundance of potential fungal plant pathogens belonging to the Sordariomycetes class decreased in domesticated compared to wild emmer while the opposite was found for members of the Glomeromycetes, which are obligate plant symbionts. The depletion of nitrifiers and of arbuscular mycorrhizal fungi in elite wheat cultivars compared to primitive domesticated forms suggests that the Green Revolution has decreased the coupling between plant and rhizosphere microbes that are potentially important for plant nutrient availability. Both plant diameter and fine root percentage exhibited the highest number of associations with microbial taxa, highlighting their putative role in shaping the rhizosphere microbiota during domestication. Aside from domestication, significant variation of bacterial and fungal community composition was found among accessions within each domestication group. In particular, the relative abundances of Ophiostomataceae and of Rhizobiales were strongly dependent on the host accession, with heritability estimates of ~ 27% and ~ 25%, indicating that there might be room for genetic improvement via introgression of ancestral plant rhizosphere-beneficial microbe associations.

Comparative effect of boiler ash-urea mixture on soil properties, growth, and yield of Cocoyam (Colocasia esculenta)

One major constraint in utilizing boiler ash in agriculture as fertilizer is its low nitrogen content. A field trial was conducted to evaluate comparatively the effect of integrating boiler ash with urea and two rates of NPK fertilizer on soil, growth, and yield of cocoyam Colocasia esculenta (Taro) in Iwollo, Southeastern Nigeria. The experiment was laid out in a randomized complete block design (RCBD) with three replications and five treatments which comprised of a control (no fertilizer), two levels of NPK 15:15:15 (100, 200kgha-1) combinations of two levels of broiler ash (5, 10 t ha-1) with 70 kg ha-1 urea. The plots were planted with cocoyam cormels. Data on soil properties after harvest, growth, and yield characteristics were collected and subjected to one-way analysis of variance, and significant treatments mean separated by Fisher's least significant difference at 5% level of probability. Results obtained showed that the treatments did not exert significant influence on the soil physical properties evaluated, but differed significantly (p&lt;0.05) in pH, phosphorus, and percent base saturation. Comparatively, integrating the low level of BA (10tha-1) with 70 Kg ha-1 urea reduced soil acidity, increased soil available P, and percent base saturation but did not significantly influence growth and tuber yield of cocoyam. Application NP. K fertilizer at the rate of 200 Kg ha-1 was a higher number of cormels plant-1 (32.6), cormel yield (47.8 Mg ha-1), and corm yield (4.53 Mg ha-1). The fertilization effects of broiler ash – urea mixture at the rate applied in the study were masked by innate soil ability to supply plant-available nutrients, but significant reduction in pH and enrichment in available P suggest that the broiler ash – urea mixture may have a positive effect under more acidic and P deficient conditions.

Response of soil fertility to 25 years of experimental acidification in a temperate hardwood forest.

The effects of enhanced acid deposition from the atmosphere, and associated elevated inputs of N, are widely evident, especially for forests where excess N has led to a variety of deleterious effects. These include declines in biodiversity, a response that will likely require considerable time for recovery. The purpose of this study was to determine responses of plant nutrient availability in surface mineral soil to 25 yr of experimental acidification and N addition in a central Appalachian hardwood forest ecosystem. We hypothesized that chronic additions of (NH4 )2 SO4 will increase mineral N, decrease soil pH, P, and base cations, increase micronutrients (Mn2+ and Fe2+ ), and increase levels of Al3+ . Results supported these predictions, although Mn2+ did not vary significantly. Earlier work on these plots found no response of any of the extractable nutrients to 3 yr of treatment, yet after 25 yr, our results suggest that impacts are apparent in the top 5cm of the A horizon. We surmise that impacts in these soils may have lagged behind the onset of acidification treatments or that several years of treatment were required to overcome preexisting differences in soil ions. Generally, current findings confirm that (NH4 )2 SO4 treatments have lowered the pH, enhanced levels of exchangeable Al3+ , and increased stream-water exports of NO3 - and base cations-a process that further acidifies soil. The combination of these changes in surface soils, with their high proportion of fine roots, may contribute to the reduced growth and competitiveness of some hardwood species at the acidified site.

Silicon addition improves plant productivity and soil nutrient availability without changing the grass:legume ratio response to N fertilization

Silicon (Si) plays an important role in plant nutrient capture and absorption, and also promotes plant mechanical strength and light interception in alpine meadows. In this study, we conducted a field experiment to examine the effect of nitrogen (N) application, with (N + Si) and without Si (N-only), on the potential for soil nutrient and the growth of grass and legume plant functional types (PFTs) in an alpine meadow. It was found that N + Si resulted in higher soil nutrient contents, leaf N and P concentrations, abundance and biomass of legume and grass PFTs than N-only. The aboveground biomass of grass (598 g m−2) and legume (12.68 g m−2) PFTs under 600 kg ha−1 ammonium nitrate (NH4NO3) per year addition with Si was significantly higher than that under the same level of N addition without Si (515 and 8.68 g m−2, respectively). The grass:legume biomass ratio did not differ significantly between the N + Si and N-only. This demonstrates that Si enhances N fertilization with apparently little effect on grass:legume ratio and increases plant-available nutrients, indicating that Si is essential for the plant community in alpine meadows.

Beneficial effects of Trichoderma secondary metabolites on crops.

Selected microbial strains used as active ingredients of biopesticides for agricultural management practices (e.g., IPM, Integrated Pest Management) are known for their ability to control phytopathogens, promote plant growth, and/or induce disease resistance. Microbes belonging to the Trichoderma genus are considered as an appropriate example of beneficial microbes and are model organisms to study plant-microbe interactions. Several Trichoderma strains are marketed as biocontrol agents and are known to increase plant growth, stress tolerance, and nutrient availability. These effects have sometimes been related to the production of effector metabolites that beneficial microbes produce during the interaction with plant and other microbes. Secondary metabolites (SMs) comprise different classes of natural compounds with low molecular weight and having numerous biological roles, especially in the interactions among organisms. Metabolomic analysis of the interactions between plants, phytopathogens, and beneficial fungi aided in the identification of several bioactive fungal SMs that positively affect plant metabolism. Some of these compounds showed direct activity against phytopathogens, but also increased disease resistance by triggering the plant defence system, and/or enhanced vegetative growth. A new generation of bioformulations based on microbial metabolites and living consortia responsible for the desired beneficial effects on crops may overcome the difficulties associated with the use of a single living microbial strain.

Physiological and biochemical role of proline, trehalose, and compost on enhancing salinity tolerance of quinoa plant

Background and objectiveResearches on compost introduced the evidence of its benefits to plant productivity and soil fertility. These advantages are noticed in forms of improving soil water holding capacity and nutrient availability for plants. These changes can also improve plants’ capability to overcome salinity stress conditions. The application of osmo-protectant materials (proline and trehalose) and/or compost addition enhances plant antioxidative defense system against stress conditions. This experiment conducted to study the effect of spraying quinoa plants with proline and trehalose with and without soil compost addition under salinity stress on some morphological and physiological aspects.Materials and methodsQuinoa plant was grown with or without compost in the soil and foliar sprayed with proline or trehalose under salt irrigation. Plant samples were taken after 60 days from sowing and at the end of the experiment for growth, yield, and biochemical measurements.ResultsGrowth and yield measurements were decreased with salinity stress. High levels of both proline and trehalose recorded the highest values of total soluble sugars, proline, and free amino acids in both unstressed or salinity stressed plants with or without compost addition. The use of compost in soil for cultivating quinoa plants with either proline or trehalose treatments increased growth parameters, photosynthetic pigments, and yield attributes. In addition, these treatments improved the accumulation of some organic solutes in leaves and promoted antioxidant enzyme activities.ConclusionCompost addition to soil with spraying proline or trehalose improved quinoa growth and yield and produced seed nutritional value.

Glacial Rock Flour as Soil Amendment in Subarctic Farming in South Greenland

Agriculture in subarctic regions is limited by a short and cold growing season. With warming in the region, the number of growing days and, consequently, the potential for agricultural intensification and expansion may increase. However, subarctic soils are typically acidic, low in plant-available nutrients, and coarsely textured, so they require soil amendment prior to intensification. This is the case in South Greenland, where we tested the use of glacial rock flour (GRF) produced by glaciers as a soil amendment. An experiment was made on a farm in South Greenland during the 2019 summer to quantify the short-term effect of applying GRF to a field dominated by perennial timothy grass. Three treatments were compared to control sites (n = 5): 20 t GRF ha−1 without conventional NPK-fertilizer, as well as 20 and 40 t GRF ha−1 in combination with 25% NPK-fertilizer. The experiment showed no significant response in biomass production (aboveground and belowground) for the plots treated with GRF only. The low rate of GRF combined with 25% NKP showed a marked and significant increase in yield in contrast to a high GRF rate with NPK, which resulted in a significant reduction in yields. The chemical composition of the plants versus soil and GRF showed that the plant uptake of nutrients was significantly higher for NPK-fertilized plots, as expected, but no differences were found between GRF-treated plots and the control plots with respect to nutrient availability or pH in the soil. We conclude that adding water and fertilizer has the potential to increase yields in South Greenland, but applying glacial rock flour as a short-term agricultural supplement needs to be further investigated before it can be recommended.

Potential of Wetlands Plants as Organic Fertilizer

Some plants in swamps are a problem because the growth rate is relatively fast, such as water chestnut (Eleocharis dulcis), kalakai (Stenochlaena palustris), and water hyacint (Eichornia crassipe)s. Therefore, various technologies are always traced to increase the use value of these swamp plants. One of the uses is by making organic fertilizer to support the availability of nutrients for plants. The purpose of this study is to utilize swamp plants and compare the pH, C-organic, N-total and C / N ratio values ??of each swamp plant. The study was conducted at the Soil Laboratory of the Faculty of Agriculture, University of Lambung Mangkurat in October - November 2014. The study used a single, completely randomized design (CRD). The factors studied were swamp plant organic material consisting of 3 treatments, namely: B1 (rat purun); B2 (kalakai); and B3 (water hyacinth). Each treatment was repeated 6 times, so that 18 experimental units were obtained. The results showed that water water hyacint had the highest N-total and the lowest C / N ratio compared to kalakai and water chestnut.

Soil nitrous oxide emissions most sensitive to fertilization history during a laboratory incubation

A 12 wk laboratory incubation examined the effects of application of various nitrogen (N) and sulfur (S) fertilizers on soil plant-available nutrient levels and nitrous oxide (N2O) gas emissions with respect to soil fertilization history using soils sampled from the University of Alberta Breton Classical Plots. Fertilization history and added fertilizer treatments showed significant effects on N2O emissions and NO3−-N and SO4−-S recovered on ion-exchange resins over the 12 wk. Mean cumulative N2O emissions ranged from 0.43 to 1.18 kg N2O-N ha−1. The relationship between observed total resin-recovered NO3−-N and N2O emissions was not consistent for soils receiving long-term applications of various combinations of N, phosphorus, potassium, and S fertilizers. The N2O emission from two soils with a history of long-term N fertilizer applications but different S fertilization histories was significantly different even though resin-recovered NO3−-N levels were similar. When grouped according to added fertilizer treatments, mean cumulative N2O emissions showed a strong linear relationship with mean resin-adsorbed NO3−-N production. We hypothesize that the differences in the relationship between NO3−-N production and N2O-N emissions for soils with different long-term fertilization histories may be a result of the interaction of N and S oxidation processes. Further, soil fertilization history may significantly influence soil N2O emissions in response to N fertilizers added within the growing season of observation but isn’t often considered in short-term experiments, and this may be a significant source of uncertainty in the estimation of greenhouse gases inventories from agricultural soils.

Tensions in future development of organic production\u2014views of stakeholders on Organic 3.0

This study analysed Swedish stakeholders’ views on future developments of organic production and consumption based on Organic 3.0, a strategic initiative by the International Federation of Organic Agriculture Movements (IFOAM). Focus group discussions were carried out with actors representing different parts of the organic value chain in Sweden. These identified a number of tensions, four of which represented an unresolved dichotomy in the way forward for the organic movement and its relevance for organic production in most settings. The first tension was between the drive for increased efficiency to achieve higher yields and an agroecological approach with broader sustainability values. The second concerned availability of plant nutrients in organic agriculture including safe recirculating of nutrients from society. The third tension set new technology against the precautionary principle and the notion of naturalness. The fourth concerned the role of organic as an innovation system; whether organic should be a forerunner, i.e. performing well above average and fostering innovation, or whether organic should be a broader movement including more farmers but then requiring more regulations that may hinder innovation. These tensions will result in important choices on direction for the organic sector as it pursues the Organic 3.0 goal of sustainably feeding a growing population based on farming systems based on organic principles.

Availability of plant nutrients and pollutants in the young soils of Surtsey compared to the older Heimaey and Elliðaey volcanic islands

Surtsey and the older islands in the Vestmannaeyjar archipelago offer a unique possibility to study how sub-Arctic ecosystems develop from unvegetated mineral substrate that lacks soil cover to grasslands with thick Brown Andosol soils. The present study was carried out on Surtsey, Heimaey and Elliðaey in 2013 and involved an incubation of resin membranes in the 0-10 cm topsoil layer in different ecosystems, which were either inside or outside seabird colonies. We compared the effects of seabird presence on soil nutrient availability as well as the importance of time for soil development (at least ca.1600 years vs. 50 years). Further we looked for build-up of Cd and Pb within the seabird colonies. Seabird presence enhanced the availability of most nutrients (N, P, K, Mg, Ca, S, Fe, Mn and Zn) except B and Cu, irrespective of the age of the islands. Soil age was also a significant factor for nutrient availability for all macro- and micronutrients except B. Nutrient ratios indicated that N was the most limiting nutrient in all ecosystems, except in the thicker tephra soils on Surtsey where low P availability may lead to co-limitation. The role of P in ecosystem function on Surtesy warrants a futher study. No accumulation of Cd and Pb was found within the seabird colonies.