Biomass Nutrient Research Articles

The response of soil microbial communities to variation in annual precipitation depends on soil nutritional status in an oligotrophic desert.

BackgroundSoil microbial communities (SMC) play a central role in the structure and function of desert ecosystems. However, the high variability of annual precipitation could results in the alteration of SMC and related biological processes depending on soil water potential. The nature of the physiological adjustments made by SMC in order to obtain energy and nutrients remains unclear under different soil resource availabilities in desert ecosystems. In order to examine this dynamic, the present study examined the effects of variation in annual precipitation on physiological adjustments by the SMC across two vegetation-soil systems of different soil organic matter input in an oligotrophic desert ecosystem.MethodsWe collected soil samples in the Cuatro Ciénegas Basin (Mexico) under two vegetation covers: rosetophylous scrub (RS) and grassland (G), that differ in terms of quantity and quality of organic matter. Collections were conducted during the years 2011, 2012, 2013 and 2014, over which a noticeable variation in the annual precipitation occurred. The ecoenzymatic activity involved in the decomposition of organic matter, and the concentration of dissolved, available and microbial biomass nutrients, were determined and compared between sites and years.ResultsIn 2011, we observed differences in bacterial taxonomic composition between the two vegetation covers. The lowest values of dissolved, available and microbial nutrients in both cover types were found in 2012. The G soil showed higher values of dissolved and available nutrients in the wet years. Significant positive correlations were detected between precipitation and the ratios Cmic:Nmic and Cmic:Pmic in the RS soil and Cmic:Pmic and Nmic:Pmic in the G soil. The slopes of the regression with Cmic and Nmic were higher in the G soil and lower in the RS soil. Moreover, the SMC under each vegetation cover were co-limited by different nutrients and responded to the sum of water stress and nutrient limitation.DiscussionSoil community within both sites (RS and G) may be vulnerable to drought. However, the community of the site with lower resources (RS) is well adapted to acquire P resources by ecoenzyme upregulation during years with adequate precipitation, suggesting that this community is resilient after drought occurs. Under the Global Climate Change scenarios for desert ecosystems that predict reduced annual precipitation and an increased intensity and frequency of torrential rains and drought events, the soil microbial communities of both sites could be vulnerable to drought through C and P co-limitation and reallocation of resources to physiological acclimatization strategies in order to survive.

Evaluation of critical nitrogen and phosphorus models for maize under full and limited irrigation conditions

Proper nitrogen (N) fertiliser application rates and timing of application, coupled with optimum irrigation management can improve the sustainability of maize production and reduce the risk of environmental contamination by nutrients. The impact of full and limited irrigation and rainfed conditions on in-season maize (Zea mays L.) shoot biomass nutrient concentration and critical N and phosphorus (P) indices were evaluated using a combination of measured nutrients and critical N and P models in south central Nebraska in 2009 and 2010. Four irrigation treatments [fully-irrigated treatment (FIT), 75% FIT, 60% FIT and 50% FIT) and rainfed] were imposed. Irrigation regimes impacted the shoot biomass N concentration. The shoot biomass N concentration was above the critical N (Ncrit) concentration throughout the growing season under FIT and 75% FIT and was below the Ncrit value for the most limited irrigation (60% FIT and 50% FIT) and rainfed treatments. Nitrogen nutrient index (NNI) varied from 0.68 to 2.0. Biomass N concentration was below Ncrit [i.e., NNI<1] from 105 days after planting (DAP) to harvest under rainfed and 50% FIT and from 114 DAP to harvest under 60% FIT. Overall, the FIT and the 75% FIT had NNI values greater than 1.0 throughout both growing seasons. Phosphorus concentration, which decreased with biomass accumulation and irrigation amounts, varied from 1.0 to 4.8 g kg–1, with FIT having the highest biomass P concentration. The critical N model combined with NNI can be used to evaluate N and P in maize for in-season nutrient diagnosis under the conditions presented in this research.

Influence of harvest managements of festulolium and tall fescue on biomass nutrient concentrations and export from a nutrient-rich peatland

This study was designed to show the effects of harvest time and frequency on biomass nutrient concentrations (total ash, N, P, K, Ca, Mg, Fe, Mn, Cu and Zn) as well as total nutrient removal potential by festulolium and tall fescue cultivated on a nutrient-rich fen peatland. The harvest managements included a three-cut (3C) and three two-cut (2C) systems which differed by two-week delays of first cut as: 2C-early, 2C-mid and 2C-late, representing phenological stages of pre-heading, inflorescence emergence, and flowering, respectively. In the study year, the grasses received 80-16–60kg N-P-K ha−1 in spring and 80-0–100kg N-P-K ha−1 after each harvest (except final). Nutrient concentrations and total ash content in the biomass dropped sharply during spring-summer growth. Concentrations of Ca, Mg and Mn were significantly higher in tall fescue biomass during spring-summer growth, but for other nutrients, there were no consistent differences between the two grasses. Total ash in the biomass from 3C managements (1.1Mg ha−1) was ∼28% higher than in the biomass removed by 2C managements (0.8 Mg ha−1). Similarly, mean annual N removal by 3C (315kgNha−1) was 31% higher than by 2C (240kgNha−1) managements, but net removals (removed minus applied N) from both managements were similar (75–80kgha−1). Net P-removal by 3C (37kgP ha−1) was higher than by 2C (26kg P ha−1) managements, whereas total K removals in all managements were close to the applied K amount (i.e., net removals were close to zero). Whereas all crop/management combinations extracted more N and P than applied, the 2C-late approach is recommended since the biomass yield was higher than for the other 2C approaches, and it required less fertilizer and management inputs than the 3C approach.

Utilization of Spent Microbial Biomass as an Alternative Crop Nitrogen Source

Core Ideas Nutrient‐rich spent microbial biomass has potential for reuse in agriculture. Tall fescue data from three harvests showed release of spent microbial biomass nutrients over time. Highest spent microbial biomass rate yielded greater tall fescue biomass than fertilizer in July. All five spent microbial biomass rates produced corn yields consistent with the fertilizer control. The renewable disposal of spent microbial biomass in agriculture may be expanded to other industries. Spent microbial biomass (SMB), a nutrient‐rich co‐product of industrial white biotechnology processes, is produced in substantial quantities alongside high‐value products and most often disposed of in landfills or incinerated. Alternatively, SMB could be reused as a land‐applied N source in agricultural crop production, reducing the environmental and economic footprint of synthetic fertilizers. This research compares SMB applied at different rates to current farmer practice (FP) fertilizer use in tall fescue (Festuca arundinacea Schreb.) and corn (Zea mays L.) production on a Dewey silty clay in Lenoir City, TN. The effect of SMB on tall fescue was measured over three harvests through plant biomass production, crop N status using the normalized difference vegetation index (NDVI), and forage quality by near‐infrared reflectance spectroscopy (NIRS). Corn productivity was measured by crop height, leaf chlorophyll content using a handheld meter, and grain yield. Tall fescue data showed the mineralization and release of SMB N over time compared with the rapidly available fertilizer N, and the highest SMB application rate in tall fescue was not statistically different from the FP in plant biomass, leaf NDVI, or any measured forage quality parameters. Despite differences in corn leaf chlorophyll contents between SMB and fertilizer treatments during the growing season, no differences in final grain yields were found. This research substantiates the potential of SMB as a soil N amendment from a nutrient source and yield perspective. Additional studies are needed to understand SMB mineralization rates and to confirm the material's nutrient contribution to crop production.

An economic assessment of local farm multi-purpose surface water retention systems in a Canadian Prairie setting

There is a need to explore more sustainable approaches to water management on the Canadian Prairies. Retention pond installation schemes designed to capture surface water may be a viable option that would reduce water stress during drought periods by providing water for irrigation. The retention systems would serve to capture excess spring runoff and extreme rainfall events, reducing flood potential downstream. Additionally, retention ponds may be used for biomass production and nutrient retention. The purpose of this research was to investigate the economic viability of adopting local farm surface water retention systems as a strategic water management strategy. A retention pond was analyzed using a dynamic simulation model to predict its storage capacity, installation and upkeep cost, and economic advantage to farmers when used for irrigation. While irrigation application increased crop revenue, the cost of irrigation and reservoir infrastructure and installation costs were too high for the farmer to experience a positive net revenue. Farmers who harvest cattails from retention systems for biomass and available carbon offset credits can gain $642.70/hectare of harvestable cattail/year. Cattail harvest also removes phosphorus and nitrogen, providing a monetized impact of $7014/hectare of harvestable cattail/year. The removal of phosphorus, nitrogen, carbon, and avoided flooding damages of the retention basin itself provide an additional $17,730–$18,470/hectare of retention system/year. The recommended use of retention systems is for avoided flood damages, nutrient retention, and biomass production. The revenue gained from these functions can support farmers wanting to invest in irrigation while providing economic and environmental benefits to the region.

Nitrogen and phosphorus flux from the production of Nile tilapia through the application of environmental indicators.

We aimed in this study utilize environmental indicators as a quantitative method to evaluate and discuss the nitrogen (TN) and phosphorus (TP) flux by a production stage grow-out (termination) of Nile tilapia (Oreochromis niloticus) in fishpond. The TN and TP load, the mass balance, the input of TN and TP via feed and the converted nutrients in fish biomass are the environmental indicators applied in this study. During the production cycle (128 days), the system exported 15,931 g TN and 4,189 g TP that were related to the amount of feed supplied (r Pearson = 0.8825 and r = 0.8523, respectively), corroborated by the feed conversion ratio (1.61:1). The indicators showed that 26% TN and 45% TP were reversed into fish biomass, 62% TN and 40% TP were retained in the fishpond, and 12% TN and 15% TP were exported via effluent. The largest contribution of nutrients generated by the system and exported via effluent was observed in phase III and IV. This result is supported by the feed conversion ratio 2.14 and 2.21:1 obtained at this phase, a fact explained by the amount of feed offered and the fish metabolism. Application of environmental indicators showed to be an efficient tool to quantify flux of TN and TP produced during the grow-out period of Nile tilapia and therefore, guide management practices more sustainable. Concerning the environmental sustainability of the activity the implementation of best management practices such as the better control of the feed amount offered would lead to a smaller loss of TN and TP to the water. Furthermore, the use of better quality feeds would allow greater nutrient assimilation efficiency.

CONTEÚDO DE NUTRIENTES NA BIOMASSA E EFICIÊNCIA NUTRICIONAL EM ESPÉCIES DA CAATINGA

Objetivou-se quantificar o conteúdo de nutrientes nos componentes da biomassa da parte aérea das espécies de maior valor de importância em duas áreas de Caatinga e avaliar a eficiência dessas plantas no uso desses nutrientes. A pesquisa foi realizada na fazenda Itapemirim, no município de Floresta - PE, onde foram estudadas duas áreas de vegetação de Caatinga em fases distintas de sucessão ecológica, apresentando características distintas, uma em estágio de regeneração e outra preservada. Na amostragem foi realizado um inventário inicial se lançando 40 parcelas de 400 m2 em cada área, tendo como nível de inclusão CAP ≥ 6,0 cm. Para análise da biomassa foram utilizadas as cinco espécies de maior valor de importância de cada área, a escolha dos indivíduos foi de forma aleatória e cada planta escolhida teve medida sua circunferência a altura do peito e na base. No processo de pesagem e amostragem dos componentes da parte aérea, as árvores escolhidas foram derrubadas e em seguida foram pesados todos seus componentes e retirada uma amostra para realização das análises químicas. Nesse estudo observou-se que o levantamento inicial nas duas áreas a Poincianella bracteosa foi a espécies que apresentou maior conteúdo de nutrientes na biomassa total acima do solo em ambas as áreas, e o componente galho foi o de maior contribuição no conteúdo de nutrientes na biomassa total, sendo N o nutriente mais acumulado no componente folha, e o Ca nos componentes lenhosos em ambas as áreas, já os nutrientes que apresentaram a maior eficiência de utilização nutricional nas espécies estudadas em ambas as áreas, foram o S e o P.

A demand-based nutrient utilization approach to urban biogas plant investment based on regional crop fertilization

This study aimed to develop a regional nutrient demand-based approach to assess the potential use of digestate nutrients from a planned biogas plant investment as a part of a regional circular economy concept. The assumed biogas plant is expected to treat urban wastes; biowastes (23,500 t/y) and sewage sludges (120,000 t/y) from the Tampere region, Finland (total population of 500,000). The calculation of the regional nutrient balance was based on the fertilizable crop areas, fertilization regimes and biomass nutrient amounts, with an assumption that livestock manures were primarily utilized in crop production. Subsequently, a Geographic Information System (GIS)-based methodology was applied to evaluate the transportation distances of nutrients from the biogas plant to the closest crop fields. As a result from the presented approach, livestock manure covered 41% and 12% of the phosphorus (P) and soluble nitrogen (N) need of the studied region. There was a residual potential for the regional utilization of biogas plant nutrients, which together with the livestock manure accounted for 50% of P and 15% of soluble-N need. Transportation of nutrients up to 40 km from the biogas plant is necessary if all nearby fields receive the waste-based nutrients, while the distance increased to 66 km if 30% of the local farmers are willing to use the nutrients. The approach presented in this study acts as a tool for planning nutrient cycles, which can be used to sustainably manage the regional nutrient flows when planning a new biogas plant investment.

Finding the harvesting frequency to maximize nutrient removal in a constructed wetland dominated by submerged aquatic plants

Water quality is still poor in many freshwater ecosystems around the world as a result of anthropogenic nutrient loading. Constructed wetlands can be used to remove excess nutrients. In these wetlands, helophytes or free floating aquatic plants are traditionally used to absorb the nutrients. The nutrients are subsequently exported upon harvesting of the plants. However, rooted submerged plants may be more effective to extract nutrients from moderately eutrophicated ecosystems than helophytes or floating species.Here, we tested how the frequency of harvesting affected submerged biomass production, biomass nutrient content and the resulting amount of nutrients removed, as well as the vegetation composition and structure. Two Myriophyllum spicatum dominated shallow ponds, with moderately low surface water nutrient loading (∼5.6mgN.m−2.d−1 and ∼1.32mg P.m−2.d−1) were used. Each pond was subjected to four harvesting treatments: mowing 1x, 2x, 3x or 5x between May and September 2015.Harvesting 2x or 3x removed most biomass and nutrients, while mowing either 5x or only once at the end of the growing season removed the lowest amount of nutrients from the system. Furthermore, the dominance of M. spicatum in the vegetation was best maintained in plots mown 2x, while its cover declined in plots mown more frequently, resulting in an increase of charophyte abundance.We conclude that harvesting at an intermediate frequency is best when aiming to remove the maximum amount of nutrients under a moderately low nutrient loading. Harvesting more frequently may be a suitable management method to reduce dominance of M. spicatum in situations where it causes nuisance problems due to massive growth.

Coupled microalgal cultivation with the treatment of domestic sewage and high-level CO2

ABSTRACTThe ability of Scenedesmus quadricauda SDEC-13 to accumulate biomass and remove nutrients in domestic sewage from campus when incorporated with 15% CO2 was explored. The maximum specific growth rate, biomass productivity, biomass concentration, and CO2 fixation rate were 0.14 d−1, 0.08 g/L/d, 0.69 g/L, and 0.076 g-CO2/L/d, respectively. The lipid content of SDEC-13 at different culture phases was also evaluated and it increased following nutrient limitation. The removal efficiencies of total nitrogen, total phosphorus, nitrate, and ammonium were all above 90%. A coupled system was designed with hydraulic retention time of 8.33 d and biomass harvest ratio of 12%, which could yield 0.54 g/L biomass and 25% lipid content with efficient domestic sewage treatment.

Different Responses of Terrestrial C, N, and P Pools and C/N/P Ratios to P, NP, and NPK Addition: a Meta-Analysis

Although phosphorus (P) enrichment alone or in combination with other nutrients such as nitrogen (N) and potassium (K) due to anthropogenic activities may modify the nutrient pools and nutrient elemental ratios of terrestrial ecosystems, few studies have revealed the global effects of P alone or in combination with N and K enrichment on terrestrial ecosystems. In this study, we conducted a meta-analysis of the impacts of P addition alone or in combination with N and K on the C, N, and P pools and C/N/P ratios of plants, soils, and microbial biomass in terrestrial ecosystems. The results suggest that the following changes occurred: (1) P addition resulted in a significantly larger plant C pool, which was further enhanced when extra N and K were added. (2) The soil and microbial biomass C pools and the plant, soil, and microbial biomass N pools were minimally affected by P addition at the global scale but were noticeably affected when N and K were simultaneously added. (3) The P pools of the plants, soil, and microbial biomass were significantly and consistently enhanced by the addition of P, NP, and NPK. (4) The plant C/N, N/P, and C/P ratios were significantly reduced when P was added, while the C/N/P ratios in the soil and microbial biomass were minimally affected. These results, which show the inconsistent responses of plant, soil, and microbial biomass nutrient pools and elemental ratios to P, NP, and NPK addition, improve our understanding of terrestrial ecosystem functions under global change scenarios.

Row and Forage Crop Rotation Effects on Maize Mineral Nutrition and Yield

Diverse crop rotations are an integral component of sustainable agriculture. The objectives were to investigate row and forage crop rotation effects on stover biomass, grain yield, and mineral nutrient concentrations of maize (Zea mays L.) grown under a maize–soybean [Glycine max (L.) Merr.] 2-yr rotation (C–S); maize–soybean–spring wheat (Triticum aestivum L.) 3-yr rotation (C–S–W); maize–soybean–oat/pea (Avena sativa L./Pisum sativum L.) hay 3-yr rotation (C–S–H); and maize–soybean–oat/pea hay underseeded with alfalfa (Medicago sativa L.) – alfalfa – alfalfa 5-yr rotation (C–S–H/A–A–A). Rotations were established in 1997 and maize plots were sampled in 2008–2011. Across the 4 yr of the study, grain yield was 10% greater (1.0 Mg ha−1) in C–S–H/A–A–A and C–S–W rotations compared with C–S with C–S–H intermediate. Under C–S–H/A–A–A, kernel N concentration was 7% greater, kernel P was 17% less, and kernel K was 7% less compared with C–S–W. Kernel Zn concentration was 16% lower in C–S–H than in C–S and C–S–H/...

Effects of strain, nutrients concentration and inoculum size on microalgae culture for bioenergy from post hydrothermal liquefaction wastewater

Cultivating microalgae in post hydrothermal liquefaction wastewater (PHWW) offers many benefits, including nutrients recovery and reuse, wastewater purification and biomass production. However, the high nutrients concentration and toxic substances in PHWW undermine the efficiency of biomass production and nutrient recovery. This study aimed to investigate the effects of the microalgae strains, initial nutrients concentrations and inoculum sizes on biomass production and nutrient recovery using PHWW as the cultivation medium. Results indicated that both biomass production and nutrients recovery were successfully improved by using the screened microalgae strain at the desirable initial nutrient concentration with the suggested algae inoculum size. Chlorella vulgaris 1067 probably demonstrated the strongest tolerance ability among the five microalgae strains screened, and performed well in the diluted PHWW, of which initial TN concentration was approximately 500 mg/L. The desirable inoculum size was determined to be 0.103-0.135 g/L. The biomass daily productivity was increased by 15.67-fold (reached 0.13 g/(L·d)). With the above optimal conditions, high biomass production and nutrient recovery from the PHWW to produce microalgae biomass for bioenergy production were achieved. Keywords: post hydrothermal liquefaction wastewater, microalgae strain screening, inoculum size, initial nutrient concentration, nutrient recovery, biomass production DOI: 10.3965/j.ijabe.20171002.2882 Citation: Zhang L, Lu H F, Y H Zhang, Ma S S, Li B M, Liu Z D, et al. Effects of strain, nutrients concentration and inoculum size on microalgae culture for bioenergy from post hydrothermal liquefaction wastewater. Int J Agric & Biol Eng, 2017; 10(2): 194–204.

Animal pee in the sea: consumer-mediated nutrient dynamics in the world's changing oceans.

Humans have drastically altered the abundance of animals in marine ecosystems via exploitation. Reduced abundance can destabilize food webs, leading to cascading indirect effects that dramatically reorganize community structure and shift ecosystem function. However, the additional implications of these top-down changes for biogeochemical cycles via consumer-mediated nutrient dynamics (CND) are often overlooked in marine systems, particularly in coastal areas. Here, we review research that underscores the importance of this bottom-up control at local, regional, and global scales in coastal marine ecosystems, and the potential implications of anthropogenic change to fundamentally alter these processes. We focus attention on the two primary ways consumers affect nutrient dynamics, with emphasis on implications for the nutrient capacity of ecosystems: (1) the storage and retention of nutrients in biomass, and (2) the supply of nutrients via excretion and egestion. Nutrient storage in consumer biomass may be especially important in many marine ecosystems because consumers, as opposed to producers, often dominate organismal biomass. As for nutrient supply, we emphasize how consumers enhance primary production through both press and pulse dynamics. Looking forward, we explore the importance of CDN for improving theory (e.g., ecological stoichiometry, metabolic theory, and biodiversity-ecosystem function relationships), all in the context of global environmental change. Increasing research focus on CND will likely transform our perspectives on how consumers affect the functioning of marine ecosystems.

Fertilization efficiency of wood ash pellets amended by gypsum and superphosphate in the ryegrass growth

Application of biomass ash to soil can save mineral nutrients due to its relatively high contents of Ca, K, and P. The study assessed the effect of powdered ash and pellets made from wood fly ash (WFA), combined moreover with additives rich in S (flue gas desulfurization gypsum – FGDG) and P (single superphosphate – SP) on the yield and uptake of nutrients (Ca, K, P, and S) by ryegrass (Lolium perenne L.), the accumulation of nutrients in plant biomass at individual four cuttings, and the available nutrients amount in the acidic loamy soil after the last harvest. Plants grown in pots enriched by wood ash showed significantly higher yield and nutrient uptake than in the unamended treatments. The uptake of nutrients by plants, content of nutrients in plants and in soil was substantially positively influenced by both components added to the wood ash, especially by FGD gypsum. The combination of wood ash with additives proved to be effective. The soil enrichment by WFA + SP + FGDG increased the availability of SP-contained P and available P content in soil even after harvest.

A mixed integer nonlinear programming model for biomass production

In this paper, a nonlinear model to maximize biomass production with specific nutritional quality is proposed. The model decides about kind of grasses and legumes to cultivate, quantities of each grasses and legumes chosen, the use of resources, and the proper time of harvest at which the biomass with specific nutritional quality is maximized. Model works with sufficient information about biomass yield, nutrient content, water requirements and fertilizer requirements of several crops, and it can explore all possible harvest times and choose the right time in which biomass production is maximized with desired nutritional quality. Furthermore, the solution gives to the producers additional information on weekly irrigation plan and weekly fertilizers plan for m2 of cultivated grass. The model was tested on six scenarios using GAMS and obtained solutions are the global solution in each scenario.

Long term carbon and nutrient dynamics within two small radiata pine catchments

The changes in distribution and turnover of organic matter and nutrients were measured over a 34year period in two small catchments planted to radiata pine in NSW. Catchment (eucalypt to pine) was cleared of native Eucalyptus regrowth, approximately 60years old, and planted to radiata pine and compared to a catchment retained to native forest (Catchment 5-retained eucalypt reported by Turner and Lambert, 2016). Plots were established prior to clearing, measured and sampled and then the same plots were re-established after replanting and analysed using the same methodologies. When the radiata pine was 34years old it had accumulated 206MgCha−1, compared to 53MgCha−1 in the biomass and litter of the mature eucalypt at time of clearing. The greater biomass was partly attributed to the greater soil rooting depth as a result of deep ripping. Except for nitrogen, for which there was a net increase in the radiata pine, no differences were found in the nutrient quantity of the radiata pine and eucalypt. Increases in the biomass nutrients were balanced by decreases in soil nutrients mainly deeper in the soil profile. Catchment 3 (mature pine to pine) had mature radiata pine plantation at the commencement of the study which was cleared and replanted to radiata pine. In the mature radiata pine catchment nutrient and carbon accumulations could be found in biomass. The conversion to a new rotation led to net decreases in carbon and nitrogen however nitrogen was found to be accumulating within the system. The other nutrients were found to be lower than the previous rotation and based on previous soil nutrient productivity studies it was concluded the removals would lead to a net decrease in productivity of about 8%. Water balance and NPP data were used to analyse stand level water use efficiency and it was concluded WUE was related to age and that there was no differences between species. Differences in runoff from catchment of different forest types/species were a result of interception or productivity differences.

Biomass and nutrient composition of temperate mangroves (Avicennia marina var. australasica) in New Zealand

ABSTRACTAccurate estimates of biomass pools and their nutrient content are key for assessing the potential of vegetation to mitigate anthropogenic carbon emissions. In this study, we used the harvest method to estimate above- and below-ground biomass (AGB and BGB) and nutrient content of the New Zealand mangrove Avicennia marina var. australasica at Mangawhai Harbour, northern New Zealand. AGB of A. marina was estimated at 5.7 ± 1.79 kg m−2 and BGB at 13.15 ± 1.55 kg m−2 (mean ± SE). The root-shoot ratio at this site was 1.73. Fine roots contributed most to the total biomass (37%) followed by woody biomass (32%), coarse roots (27%), leaves (3%), and pneumatophores and seedlings (1%). Allocation of total carbon (TC) followed similar proportions as total biomass with was 64% in the roots, 33% in wood, and 3% in the leaves (by dry mass). Roots contained 64% of total nitrogen (TN) and 53% of total phosphorus (TP) (by dry mass). In leaves, TN was 5% and TP was 6% with the remaining nutrients in woody biomass. The foliar N:P ratio was 8.2, suggesting nitrogen limitation at this site. Based on these results, we estimate that New Zealand mangroves store a total of 0.2–1.1 Mt carbon (C) above ground and 1.06–1.72 Mt C below ground.

Phosphorus Deficiency Alters Nutrient Accumulation Patterns and Grain Nutritional Quality in Rice

The accumulation of biomass and mineral nutrients during the post-anthesis period was investigated in field-grown rice plants cultivated in phosphorus (P)-sufficient vs. P-deficient soil. Phosphorus deficiency reduced biomass accumulation by around 30%, and reduced the accumulation of all nutrients in aboveground plant biomass except sulfur (S) and copper (Cu). Ultimately, grain zinc (Zn), Cu, and calcium (Ca) concentrations were significantly higher in P-deficient plants, while grain magnesium (Mg) concentrations were significantly lower. While P deficiency caused a 40% reduction in the concentration of the anti-nutrient phytate in the grain, this was offset by a 40% reduction in grain starch lysophospholipids, which have positive benefits for human health and grain quality.

Nutrient cycling over five years of mixed-species plantations of Eucalyptus and Acacia on a sandy tropical soil

Mixed-species plantations have the potential to enhance nutrient cycling and increase the overall biomass of the stand. In this study, we evaluate the dynamics of nutrient accumulation and exports in mixed-species plantations of Eucalyptus urograndis (Eucalyptus urophylla S. T. Blake×Eucalyptus grandis W. Hill ex Maiden) and Acacia mangium Willd. after five years of rotation. Monocultures of Eucalyptus urograndis, with or without nitrogen fertilization (120kgNha−1) (E100 and E100+N, respectively), and of Acacia mangium (A100) were established in a randomized block experimental design. Two arrangements with these species in mixed stands were also established: one with 50% of the stand density composed by each species (E50A50; 1,111 treesha−1), and one high-density system, containing double the population of each species (E100A100; 2,222treesha−1). Aboveground biomass and litter nutrient contents, nutrient retranslocation from leaves, and nutrient export through wood harvesting were measured over a full rotation. Eucalyptus in E50A50, despite having half of the population of trees (555treesha−1), accumulated the same amount of nutrients in total aboveground biomass in relation to E100, suggesting a lower nutrient limitation to the growth of Eucalyptus in this mixed stand. Conversely, Eucalyptus in E100A100 did not accumulate proportionally larger amounts of nutrients in relation to E50A50, possibly due to intra- and interspecific competition in this high-density arrangement. The deposition of N and K via litter was higher in mixed-species stands than in Eucalyptus monocultures. Also, P, Ca and Mg depositions were higher in mixed-species stands than Acacia monocultures. These results suggest higher nutrient cycling and availability in the mixtures, especially after 30months. The retranslocation of N in Eucalyptus and Acacia leaves decreased with age. At 60months, Eucalyptus trees in E100A100 retranslocated less N than the trees in E100, probably reflecting the higher availability of soil N in relation to E100. At this same age, the Eucalyptus trees planted in E50A50 exported less N, P, K and Mg in relation to E100. However, at stand level, mixtures exported more N due to the enrichment of this nutrient in the soil promoted by Acacia. This study shows the importance of introducing Acacia in Eucalyptus plantations to promote a positive balance of nutrients for subsequent rotations and additional ecological benefits to the ecosystem due to N2-fixation from Acacia trees.