Optimizing nitrogen supply promotes biomass,physiological characteristics and yield components of soybean (Glycine max L. Merr.)

Avoidable or inappropriate nitrogen (N) fertilizer rates harmfully affect the yield production and ecological value. Therefore, the aims of this study were to optimize the rate and timings of N fertilizer to maximize yield components and photosynthetic parameter of soybean. This field experiment consists of five fertilizer N rates: 0, 75, 150, 225 and 300 kg N ha⁻¹ arranged in main plots and four N fertilization timings: V₅ (trifoliate leaf), R₂ (full flowering stage) and R₄ (full poding stage), and R₆ (full seeding stage) growth stages organized as subplots. Results revealed that 225 kg N ha⁻¹ significantly enhanced grain yield components, total chlorophyll (Chl), photosynthetic rate (P_N), and total dry biomass and N accumulation by 20%, 16%, 28%, 7% and 12% at R₄ stage of soybean. However, stomatal conductance (g_s), leaf area index (LAI), intercellular CO₂ concentration (Ci) and transpiration rate (E) were increased by 12%, 88%, 10%, 18% at R₆ stage under 225 kg N ha⁻¹. Grain yield was significantly associated with photosynthetic characteristics of soybean. In conclusion, the amount of nitrogen 225 kg ha⁻¹ at R₄ and R₆ stages effectively promoted the yield components and photosynthetic characteristics of soybean.     

Biochar in Combination with Nitrogen Fertilizer is a Technique: To Enhance Physiological and Morphological Traits of Rice (Oryza sativa L.) by Improving Soil Physio-biochemical Properties

The over use of synthetic nitrogen (N) fertilizers is the major anthropogenic cause of low N-use efficiency and environmental damage in wetland rice production. Biochar (B) addition to soil is suggested as a climate change mitigation tool that supports carbon sequestration and reduces N losses and greenhouse gas emissions from the soil. Therefore, this study assessed the effect of four levels of B (0, 10, 20 and 30 t ha^?1) combined with two levels of N (135 and 180 kg ha^?1) on soil health, roots dynamics, physiological attributes, and yield components of rice. The addition of B at 30 t ha^?1 combined with 135 N kg ha^?1 increased chlorophyll content, net photosynthetic rate, biomass, and grain yield by 104%, 64%, 12%, and 30%, respectively, over control. Further, root traits such as total root length (TRL), total root volume (TRV), total root surface area (TRSA), and total average root diameter (TARD) were improved under 30 t ha^?1 combined with 135 N kg ha^?1 by 20%, 13%, 13%, and 25%, respectively, than non-biochar treatment under lower N application. Improvements in these traits resulted from higher N uptake due to improved soil physiochemical properties and soil microbial biomass combined with biochar. Interestingly, enhanced N metabolizing enzyme activities, including nitrate reductase (NR), glutamine synthetase (GS), and glutamine oxoglutarate aminotransferase (GOGAT) in biochar-treated plots, further supported the increases in these traits. Our results revealed that the integration of 30 t B ha^?1 with 135 kg N ha^?1 is a favorable option for enhancing soil health and rice grain yield.

     

Household energy and recycling of nutrients and carbon to the soil in integrated crop‐livestock farming systems: a case study in Kumbursa village,Central Highlands of Ethiopia

Soil amendment with organic wastes in the Highlands of Ethiopia has been greatly reduced by widespread use of dung cakes and crop residues as fuels. This study assessed the interaction between household energy and recycling of nutrients and carbon to the soil using household survey, focus group discussions, key informant interviews, direct observations and measurements between 2014 and 2015 in Kumbursa village (Central Highlands of Ethiopia). All surveyed households were entirely dependent on biomass fuel for cooking, with production and consumption rates directly related to wealth status, which significantly varied (P < 0.001) among three farm wealth groups (poor, medium and rich). Crop residues and dung cakes accounted for 80(±3)% by energy content and 85(±4)% by dry mass weight of total biomass fuel consumption. Mean losses were 59(±2) kg ha^?1 yr^?1 nitrogen (109(±8) kg yr^?1 per household), 13.9(±0.3) kg ha^?1 yr^?1 phosphorus (26(±2) kg yr^?1 per household), 79(±2) kg ha^?1 yr^?1 potassium (150(±11) kg yr^?1 per household) and 2100(±40) kg ha^?1 yr^?1 organic carbon (3000(±300) kg yr^?1 per household). Rich farmers lost significantly more carbon and nutrients in fuel than farmers in other wealth groups. However, these losses were spread over a larger area, so losses per land area were significantly higher for medium and poor than for rich farmers. This means that the land of poorer farmers is likely to become degraded more rapidly due to fuel limitations than that of rich farmers, so increasing the poverty gap. The estimated financial loss per household due to not using dung and crop residues as organic fertilizer was 162(±8) USSoil amendment with organic wastes in the Highlands of Ethiopia has been greatly reduced by widespread use of dung cakes and crop residues as fuels. This study assessed the interaction between household energy and recycling of nutrients and carbon to the soil using household survey, focus group discussions, key informant interviews, direct observations and measurements between 2014 and 2015 in Kumbursa village (Central Highlands of Ethiopia). All surveyed households were entirely dependent on biomass fuel for cooking, with production and consumption rates directly related to wealth status, which significantly varied (P < 0.001) among three farm wealth groups (poor, medium and rich). Crop residues and dung cakes accounted for 80(±3)% by energy content and 85(±4)% by dry mass weight of total biomass fuel consumption. Mean losses were 59(±2) kg ha^?1 yr^?1 nitrogen (109(±8) kg yr^?1 per household), 13.9(±0.3) kg ha^?1 yr^?1 phosphorus (26(±2) kg yr^?1 per household), 79(±2) kg ha^?1 yr^?1 potassium (150(±11) kg yr^?1 per household) and 2100(±40) kg ha^?1 yr^?1 organic carbon (3000(±300) kg yr^?1 per household). Rich farmers lost significantly more carbon and nutrients in fuel than farmers in other wealth groups. However, these losses were spread over a larger area, so losses per land area were significantly higher for medium and poor than for rich farmers. This means that the land of poorer farmers is likely to become degraded more rapidly due to fuel limitations than that of rich farmers, so increasing the poverty gap. The estimated financial loss per household due to not using dung and crop residues as organic fertilizer was 162(±8) US$ yr^?1. However, this is less than their value as fuels, which was 490(±20) US$ yr^?1. Therefore, farmers will only be persuaded to use these valuable assets as soil improvers if an alternative, cheaper fuel source can be found.     

Fluxes of greenhouse gases from Andosols under coffee in monoculture or shaded by <Emphasis Type="Italic">Inga densiflora</Emphasis> in Costa Rica

The objective of this study was to evaluate the effect of N fertilization and the presence of N₂ fixing leguminous trees on soil fluxes of greenhouse gases. For a one year period, we measured soil fluxes of nitrous oxide (N₂O), carbon dioxide (CO₂) and methane (CH₄), related soil parameters (temperature, water-filled pore space, mineral nitrogen content, N mineralization potential) and litterfall in two highly fertilized (250 kg N ha⁻¹ year⁻¹) coffee cultivation: a monoculture (CM) and a culture shaded by the N₂ fixing legume species Inga densiflora (CIn). Nitrogen fertilizer addition significantly influenced N₂O emissions with 84% of the annual N₂O emitted during the post fertilization periods, and temporarily increased soil respiration and decreased CH₄ uptakes. The higher annual N₂O emissions from the shaded plantation (5.8 ± 0.3 kg N ha⁻¹ year⁻¹) when compared to that from the monoculture (4.3 ± 0.1 kg N ha⁻¹ year⁻¹) was related to the higher N input through litterfall (246 ± 16 kg N ha⁻¹ year⁻¹) and higher potential soil N mineralization rate (3.7 ± 0.2 mg N kg⁻¹ d.w. d⁻¹) in the shaded cultivation when compared to the monoculture (153 ± 6.8 kg N ha⁻¹ year⁻¹ and 2.2 ± 0.2 mg N kg⁻¹ d.w. d⁻¹). This confirms that the presence of N₂ fixing shade trees can increase N₂O emissions. Annual CO₂ and CH₄ fluxes of both systems were similar (8.4 ± 2.6 and 7.5 ± 2.3 t C-CO₂ ha⁻¹ year⁻¹, −1.1 ± 1.5 and 3.3 ± 1.1 kg C-CH₄ ha⁻¹ year⁻¹, respectively in the CIn and CM plantations) but, unexpectedly increased during the dry season.     

No general soil carbon sequestration under Central European short rotation coppices

Wood from short rotation coppices (SRCs) is discussed as bioenergy feedstock with good climate mitigation potential inter alia because soil organic carbon (SOC) might be sequestered by a land-use change (LUC) from cropland to SRC. To test if SOC is generally enhanced by SRC over the long term, we selected the oldest Central European SRC plantations for this study. Following the paired plot approach soils of the 21 SRCs were sampled to 80 cm depth and SOC stocks, C/N ratios, pH and bulk densities were compared to those of adjacent croplands or grasslands. There was no general trend to SOC stock change by SRC establishment on cropland or grassland, but differences were very site specific. The depth distribution of SOC did change. Compared to cropland soils, the SOC density in 0–10 cm was significantly higher under SRC (17 ± 2 in cropland and 21 ± 2 kg C m⁻³ in SRC). Under SRC established on grassland SOC density in 0–10 cm was significantly lower than under grassland. The change rates of total SOC stocks by LUC from cropland to SRC ranged from −1.3 to 1.4 Mg C ha⁻¹ yr⁻¹ and −0.6 Mg C ha⁻¹ yr⁻¹ to +0.1 Mg C ha⁻¹ yr⁻¹ for LUC from grassland to SRC, respectively. The accumulation of organic carbon in the litter layer was low (0.14 ± 0.08 Mg C ha⁻¹ yr⁻¹). SOC stocks of both cropland and SRC soils were correlated with the clay content. No correlation could be detected between SOC stock change and soil texture or other abiotic factors. In summary, we found no evidence of any general SOC stock change when cropland is converted to SRC and the identification of the factors determining whether carbon may be sequestered under SRC remains a major challenge.     

Sedimentary Organic Carbon and Nitrogen Sequestration Across a Vertical Gradient on a Temperate Wetland Seascape Including Salt Marshes,Seagrass Meadows and Rhizophytic Macroalgae Beds

Coastal wetlands are key in regulating coastal carbon and nitrogen dynamics and contribute significantly to climate change mitigation and anthropogenic nutrient reduction. We investigated organic carbon (OC) and total nitrogen (TN) stocks and burial rates at four adjacent vegetated coastal habitats across the seascape elevation gradient of Cádiz Bay (South Spain), including one species of salt marsh, two of seagrasses, and a macroalgae. OC and TN stocks in the upper 1 m sediment layer were higher at the subtidal seagrass Cymodocea nodosa (72.3 Mg OC ha⁻¹, 8.6 Mg TN ha⁻¹) followed by the upper intertidal salt marsh Sporobolus maritimus (66.5 Mg OC ha⁻¹, 5.9 Mg TN ha⁻¹), the subtidal rhizophytic macroalgae Caulerpa prolifera (62.2 Mg OC ha⁻¹, 7.2 Mg TN ha⁻¹), and the lower intertidal seagrass Zostera noltei (52.8 Mg OC ha⁻¹, 5.2 Mg TN ha⁻¹). The sedimentation rates increased from lower to higher elevation, from the intertidal salt marsh (0.24 g cm⁻² y⁻¹) to the subtidal macroalgae (0.12 g cm⁻² y⁻¹). The organic carbon burial rate was highest at the intertidal salt marsh (91 ± 31 g OC m⁻² y⁻¹), followed by the intertidal seagrass, (44 ± 15 g OC m⁻² y⁻¹), the subtidal seagrass (39 ± 6 g OC m⁻² y⁻¹), and the subtidal macroalgae (28 ± 4 g OC m⁻² y⁻¹). Total nitrogen burial rates were similar among the three lower vegetation types, ranging from 5 ± 2 to 3 ± 1 g TN m⁻² y⁻¹, and peaked at S. maritimus salt marsh with 7 ± 1 g TN m⁻² y⁻¹. The contribution of allochthonous sources to the sedimentary organic matter decreased with elevation, from 72% in C. prolifera to 33% at S. maritimus. Our results highlight the need of using habitat-specific OC and TN stocks and burial rates to improve our ability to predict OC and TN sequestration capacity of vegetated coastal habitats at the seascape level. We also demonstrated that the stocks and burial rates in C. prolifera habitats were within the range of well-accepted blue carbon ecosystems such as seagrass meadows and salt marshes.

     

Increasing fish production from wetlands at Lake Victoria, Uganda using organically manured seasonal wetland fish ponds

The processes driving primary productivity and its impacts on fish production were investigated in field trials in eight seasonal earthen wetland ponds ‘Fingerponds’ (192 m²) in Uganda between 2003 and 2005. The ponds were stocked by the seasonal flood with predominantly Oreochromis spp. at densities ranging from 0.1 to 0.5 fish m⁻². Chicken manure (521, 833 or 1,563 kg ha⁻¹) was applied fortnightly. Results showed that primary productivity was enhanced with maximum average net primary productivity (±Standard Error) of 11.7 (±2.5) g O₂ m⁻² day⁻¹ at the Gaba site and 8.3 (±1.5) g O₂ m⁻² day⁻¹ at the Walukuba site. Net fish yields were higher in manured ponds with up to 2,670 kg ha⁻¹ yield for a 310 day growth period compared to less than 700 kg ha⁻¹ in unmanured ponds. Fish production was limited mainly by high recruitment, falling water levels, light limitation from high suspended solids and turbidity, and low zooplankton biomass. It was concluded that Fingerponds have a high potential for sustainable fish production and can contribute to the alleviation of protein shortages amongst the riparian communities around Lake Victoria. Production can be enhanced further with improved stock management.     

Vertical Redistribution of Soil Organic Carbon Pools After Twenty Years of Nitrogen Addition in Two Temperate Coniferous Forests

Nitrogen (N) inputs from atmospheric deposition can increase soil organic carbon (SOC) storage in temperate and boreal forests, thereby mitigating the adverse effects of anthropogenic CO₂ emissions on global climate. However, direct evidence of N-induced SOC sequestration from low-dose, long-term N addition experiments (that is, addition of < 50 kg N ha⁻¹ y⁻¹ for > 10 years) is scarce worldwide and virtually absent for European temperate forests. Here, we examine how tree growth, fine roots, physicochemical soil properties as well as pools of SOC and soil total N responded to 20 years of regular, low-dose N addition in two European coniferous forests in Switzerland and Denmark. At the Swiss site, the addition of 22 kg N ha⁻¹ y⁻¹ (or 1.3 times throughfall deposition) stimulated tree growth, but decreased soil pH and exchangeable calcium. At the Danish site, the addition of 35 kg N ha⁻¹ y⁻¹ (1.5 times throughfall deposition) impaired tree growth, increased fine root biomass and led to an accumulation of N in several belowground pools. At both sites, elevated N inputs increased SOC pools in the moderately decomposed organic horizons, but decreased them in the mineral topsoil. Hence, long-term N addition led to a vertical redistribution of SOC pools, whereas overall SOC storage within 30 cm depth was unaffected. Our results imply that an N-induced shift of SOC from older, mineral-associated pools to younger, unprotected pools might foster the vulnerability of SOC in temperate coniferous forest soils.

     

Nitrous Oxide Emission from Grazed Grassland Under Different Management Systems

Nitrous oxide (N₂O) emissions from grazed grasslands are estimated to be approximately 28% of global anthropogenic N₂O emissions. Estimating the N₂O flux from grassland soils is difficult because of its episodic nature. This study aimed to quantify the N₂O emissions, the annual N₂O flux and the emission factor (EF), and also to investigate the influence of environmental and soil variables controlling N₂O emissions from grazed grassland. Nitrous oxide emissions were measured using static chambers at eight different grasslands in the South of Ireland from September 2007 to August 2009. The instantaneous N₂O flux values ranged from -186 to 885.6 μg N₂O-N m⁻² h⁻¹ and the annual sum ranged from 2 ± 3.51 to 12.55 ± 2.83 kg N₂O-N ha⁻¹ y⁻¹ for managed sites. The emission factor ranged from 1.3 to 3.4%. The overall EF of 1.81% is about 69% higher than the Intergovernmental Panel on Climate Change (IPCC) default EF value of 1.25% which is currently used by the Irish Environmental Protection Agency (EPA) to estimate N₂O emission in Ireland. At an N applied of approximately 300 kg ha⁻¹ y⁻¹, the N₂O emissions are approximately 5.0 kg N₂O-N ha⁻¹ y⁻¹, whereas the N₂O emissions double to approximately 10 kg N ha⁻¹ for an N applied of 400 kg N ha⁻¹ y⁻¹. The sites with higher fluxes were associated with intensive N-input and frequent cattle grazing. The N₂O flux at 17°C was five times greater than that at 5°C. Similarly, the N₂O emissions increased with increasing water filled pore space (WFPS) with maximum N₂O emissions occurring at 60–80% WFPS. We conclude that N application below 300 kg ha⁻¹ y⁻¹ and restricted grazing on seasonally wet soils will reduce N₂O emissions.     

Effects of Mechanized,Deep Application of Slow-Release Fertilizer on Yield and Nitrogen,Phosphorus, and Potassium Utilization of Direct-Seeded Rice

Compared with the standard method of manual fertilizer broadcasting (MFB), mechanized hill-drilling direct-seeding with deep application of slow-release nitrogen fertilizer (MHDDF) is an efficient method to integrate both fertilization and seeding. However, there are few studies that combine the use of slow-release fertilizer with MHDDF. We sought to explore the combined effect of MHDDF with slow-release fertilizer on rice yield and nitrogen, phosphorus, and potassium utilization, compared to MFB. We compared three different MHDDF methods (D30: 450 kg ha^?1, D40: 600 kg ha^?1, D50: 750 kg ha^?1), with one MFB method (B50: 750 kg ha^?1), and one control (CK: 0 kg ha^?1). We found that the yield of all MHDDF method was higher than that of both the MFB method. Yield was the highest in the D50 treatment and was 14.14–46.03% higher than that in B50 treatment. Biomass accumulation, nutrient accumulation, and nutrient use efficiency were similarly higher in MHDDF method than both MFB and CK. Compared to B50, the D50 treatment increased nitrogen recovery efficiency by 170.53–231.50%, phosphorus recovery efficiency by 480.00–724.25%, and potassium recovery efficiency by 201.55–169.59%. Overall, we found that combining MHDDF with slow-release fertilizer was an effective method to increase rice yield and nutrient use efficiency compared with MFB.

     

Effects of acute cigarette smoke concentrate exposure on mitochondrial energy transfer in fast- and slow-twitch skeletal muscle

The mechanisms underlying cigarette smoke-induced mitochondrial dysfunction in skeletal muscle are still poorly understood. Accordingly, this study aimed to examine the effects of cigarette smoke on mitochondrial energy transfer in permeabilized muscle fibers from skeletal muscles with differing metabolic characteristics. The electron transport chain (ETC) capacity, ADP transport, and respiratory control by ADP were assessed in fast- and slow-twitch muscle fibers from C57BL/6 mice (n = 11) acutely exposed to cigarette smoke concentrate (CSC) using high-resolution respirometry. CSC decreased complex I-driven respiration in the white gastrocnemius (CONTROL:45.4 ± 11.2 pmolO₂.s⁻¹.mg⁻¹ and CSC:27.5 ± 12.0 pmolO₂.s⁻¹.mg⁻¹; p = 0.01) and soleus (CONTROL:63.0 ± 23.8 pmolO₂.s⁻¹.mg⁻¹ and CSC:44.6 ± 11.1 pmolO₂.s⁻¹.mg⁻¹; p = 0.04). In contrast, the effect of CSC on Complex II-linked respiration increased its relative contribution to muscle respiratory capacity in the white gastrocnemius muscle. The maximal respiratory activity of the ETC was significantly inhibited by CSC in both muscles. Furthermore, the respiration rate dependent on the ADP/ATP transport across the mitochondrial membrane was significantly impaired by CSC in the white gastrocnemius (CONTROL:-70 ± 18 %; CSC:-28 ± 10 %; p < 0.001), but not the soleus (CONTROL:47 ± 16 %; CSC:31 ± 7 %; p = 0.08). CSC also significantly impaired mitochondrial thermodynamic coupling in both muscles. Our findings underscore that acute CSC exposure directly inhibits oxidative phosphorylation in permeabilized muscle fibers. This effect was mediated by significant perturbations of the electron transfer in the respiratory complexes, especially at complex I, in both fast and slow twitch muscles. In contrast, CSC-induced inhibition of the exchange of ADP/ATP across the mitochondrial membrane was fiber-type specific, with a large effect on fast-twitch muscles.     

Potential of dendrochronology in assessing carbon sequestration rates of Vitellaria paradoxa in southern Mali,West Africa

This study aimed to investigate the applicability of dendrochronology for assessing the growth dynamics and response to climate variability and to estimate the aboveground carbon stock and carbon sequestration potential of Vitellaria paradoxa in southern Mali. Twenty stem disks were collected from three land-use types (parklands, fallows and protected areas) in Koutiala and Yanfolila districts. We combined a standard dendrochronological approach with biomass allometric equations to estimate the growth and carbon stocks. The results showed that V. paradoxa forms distinct growth ring boundaries but most of the disks from parklands did not successfully cross-date due to management operations like pruning. The tree-ring width showed a significant standardized coefficient of regression with rainfall (r² = 0.66, p < 0.001) but insignificant correlation with temperature. One-way analysis of variance showed no significant difference (p > 0.05) for C-sequestration as well as for carbon stocks in aboveground biomass for both land-use types and sites. Mean values of the amount of C-sequestered in Yanfolila were 0.112 ± 0.0.065 Mg C ha⁻¹ yr⁻¹ in parklands, 0.075 ± 0.018 Mg C ha⁻¹ yr⁻¹ in fallows and 0.064 ± 0.028 Mg C ha⁻¹ yr⁻¹ in protected areas. In Koutiala, the values were 0.068±0.020 Mg C ha⁻¹ yr⁻¹ in the parklands and 0.053 ± 0.017 Mg C ha⁻¹ yr⁻¹ in the fallows. These results clearly indicate that dendrochronology can be applied to assess growth and carbon sequestration potential of V. paradoxa. These results also suggest that climate change could affect the growth and carbon sequestration potential of V. paradoxa. Given the limited size of our sample, figures on the amount of carbon are indicative calling for applying the tested approaches to larger samples and also to other tree species in West Africa.     

Application of zeolite improves water and nitrogen use efficiency while increasing essential oil yield and quality of Salvia officinalis under water-deficit stress

Soil moisture and nitrogen (N) are two of the most important factors affecting the production of medicinal plants. So, the management strategy of these factors is critical and to be identified. In order to study the application of zeolite (Z) (0 and 10 ton ha^?1) in S. officinalis culture medium under different irrigation regimes (30 % depletion of available soil water (ASW)) and 60 % depletion of ASW) and N (0, 75 and 150 kg N ha^?1) a split-factorial experiment was carried out with three replicates in 2018. The highest fresh and dry weight were achieved at irrigation after 30 % depletion of ASW while using 150 kg N ha^?1 and 10 ton Z ha^?1. Maximum water use efficiency (WUE) (22.10 g.L^-1) was obtained after 60 % depletion of ASW and 150 kg N ha^?1 and 10 ton Z ha^?1. Besides, the maximum nitrogen use efficiency (NUE) was obtained after 60 % depletion of ASW and 75 kg N ha^?1 and 10 ton Z ha^?1 (14.25 kg.kg^-1N). Maximum essential oil (EO) content (1.06%) and cis-Thujone were obtained from plants subjected to 60 % depletion of ASW and, application of 75 kg N ha^?1 and 10 ton Z ha^?1. Applying Z with N, in different irrigation regimes did improve soil conditions for achieving higher, WUE and NUE, increased the EO content and yield while decreasing the negative effects from water-deficit stress and has provided a direction towards a stable system.     

Recovery of the ectomycorrhizal community after termination of long-term nitrogen fertilisation of a boreal Norway spruce forest

Ectomycorrhizal fungi (ECM) are a fundamental component of boreal forests promoting tree growth and participating in soil nutrient cycling. Increased nitrogen (N) input is known to largely influence ECM communities but their potential recovery is not well understood. Therefore, we studied the effects of long-term N-fertilisation on ECM communities, and their recovery after termination of N treatment. Fungal ITS sequencing data indicated that N-fertilisation (34 kg N ha⁻¹ y⁻¹) for 46 y decreased the relative abundance of ECM species in the fungal community and suppressed originally dominating medium-distance fringe exploration types adapted to N-limited conditions, while the ECM diversity remained unaffected. In other plots, 23 y after termination of fertilisation at 73 kg N ha⁻¹ y⁻¹ for 23 y, the relative abundance of ECM species shifted closer to, but did not reach, control levels. These observations indicate only slow recovery of ECM community, likely due to a high soil N retention capacity.     

No changes in soil organic carbon and nitrogen following long-term prescribed burning and livestock exclusion in the Sudan-savanna woodlands of Burkina Faso

Fire and overgrazing reduce aboveground biomass, leading to land degradation and potential impacts on soil organic carbon (SOC) and total nitrogen (TN) dynamics. However, empirical data are lacking on how prescribed burning and livestock exclusion impact SOC in the long-term. Here we analyse the effects of 19 years of prescribed annual burning and livestock exclusion on tree density, SOC and TN concentrations in the Sudanian savanna ecoregion at two sites (Tiogo and Laba) in Burkina Faso. Results revealed that neither livestock exclusion nor prescribed burning had significant impact on SOC and TN concentrations. The results at both sites indicate that 19 years of livestock and fire exclusion did not result in a significant increase in tree density compared to grazing and annual prescribed burning. The overall mean (± SEM) of SOC stocks in the 0–50 cm depth increment in the unburnt (53.5 ± 4.7 Mg C ha⁻¹) and annually burnt (56.4 ± 4.3 Mg C ha⁻¹) plots at Tiogo were not statistically different. Similarly, at Laba there was no significant difference between the corresponding figures in the unburnt (37.9 ± 2.6 Mg ha⁻¹) and in the annually burnt plots (38.6 ± 1.9 Mg ha⁻¹). Increases in belowground inputs from root turnover may have countered changes in aboveground biomass, resulting in no net change in SOC and TN. We conclude that, contrary to our expectation and current policy recommendations, restricting burning or grazing did not result in increase in SOC stocks in this dry savanna ecosystem.     

Identification and inoculation of fungal strains from Cedrus deodara rhizosphere involve in growth and alleviation of high nitrogen stress

Cedrus deodara is economically and ethnobotanically an important forest tree and is shown to be at decline in Northern areas of Pakistan in recent years mainly due to high concentration of Nitrogen in forests. Ectomycorrhizal (ECM) association forming fungi enables the forest trees to develop optimally by absorbing water from the rhizosphere through their absorptive hyphae and by making available the nutrients by mobilization of N and P from the organic substrates. This study was conducted to identify the ECM strains from C. deodara rhizosphere and to analyse the impact of high N load on the C. deodara seedlings to establish N critical load value for coniferous forests of Pakistan. Six new fungal strains were identified from the rhizosphere of C. deodara and were registered at GenBank (NCBI) as Emmia latemarginata strain ACE1, Aspergillus terreus strain ACE2, Purpureocillium lilacinum strain ACE3, Talaromyces pinophilus strain ACE4, A. fumigatus strain ACE5 and T. pinophilus strain ACE6 with accession numbers MH145426, MH145427, MH145428, MH145429, MH145430 and MH547115. Four out of six isolated strains were inoculated with seedlings of C. deodara singly and in consortium (CN) in combination with nitrogen load of 0 (C), 25 (T1), 50 (T2), 100 kg N ha⁻¹ yr⁻¹ (T3). Agronomic, physiological and gene expression studies for ExpansinA4 (EXPA4) and Cystatins (Cys) were made to analyse the impact of fungal strains in relation to high N stress. This study suggests a positive impact of T1 (25 kg N ha⁻¹ yr⁻¹) Nitrogen load and a negative impact of T3 (100 kg N ha⁻¹ yr⁻¹) on growth parameters and expression patterns of EXPA4 and Cys genes. Peroxidase (POX) activity decreased in the order ACE5 > ACE2 > C > ACE3 > ACE1 > CN. However, the results of Superoxide dismutase (SOD) showed decreasing trend in the order ACE5 > C > CN > ACE1 > ACE2 > ACE3. Strain ACE3 was shown to have a positive impact on the seedlings in terms of growth, physiology and expression of genes. Present study suggests that newly identified fungal strains showing positive impact on the growth and physiology of C. deodara could be used for the propagation of this economically important plant in Pakistan after pathogenicity test.     

Plant responses to nutrient addition and predictive ability of vegetation N:P ratio in an austral fen

1. Previous studies of the N:P ratio in wetland plants have been carried out in northern hemisphere wetlands where atmospheric nitrogen deposition is higher. There is little research on foliar N:P ratio as a potential indicator of nutrient limitation in vegetation communities in southern hemisphere wetlands. This study aimed to redress this knowledge gap and answer the following questions: how well does the plant tissue nitrogen to phosphorus (N:P) ratio predict wetland plant community nutrient limitation, as indicated by vegetation standing stocks and below-ground biomass, in southern hemisphere fens? Secondly, what are the impacts of realistic upper levels of farm nutrient run-off on natural montane fen vegetation?
2. Low (35 kg ha⁻¹ year⁻¹) and high (70 kg ha⁻¹ year⁻¹) levels of nitrate-N or ammonium-N with and without P (20 kg ha⁻¹ year⁻¹) were added to 81 vegetation plots over a period of 2.75 years. Species composition, plant nutrient status, and above-ground live vegetation standing stocks were assessed after 3 years, and below-ground biomass after 2 years.
3. Plant tissue analysis suggested the community was N limited or N and P co-limited; we found greater standing stocks of vegetation in plots treated with 70 kg ha⁻¹ year⁻¹ ammonium-N, indicating N limitation. No difference between other treatments was found in above-ground standing stocks or below-ground biomass. Plant species cover increased in both high N treatments, consistent with N limitation. These changes in plant species cover were accompanied by significant decreases in species richness in both high N treatments. Native species dominated the vegetation and this was unaffected by nutrient addition (90% cover).
4. This is one of the first studies to test and find support for the N:P ratio in southern hemisphere wetlands. Observed declines in species richness after N fertilisation in an N-limited fen suggests increased N may pose risks to austral wetlands. Responses by plant communities (changes in composition, biomass) to lower levels of nutrient addition may require longer periods of fertilisation to be apparent in slow growing ecosystems.

     

Formulations of Beauveria bassiana MABb1 and mesoporous materials for the biological control of Sphenarium purpurascens in maize crops from Puebla,Mexico

This investigation reports on the biological control of Sphenarium purpurascens by using different concentrations of conidia from a native strain of Beauveria bassiana (MABb1) isolated in Puebla, Mexico under laboratory and in situ conditions. Formulations containing this native strain combined with two mesoporous materials (diatomaceous earth “D” and zeolite “Z”) were assayed in order to determine their effect on the mortality of the grasshopper. Concentrations of 3.67 × 10⁸ to 10.30 × 10⁸ conidia mL⁻¹ caused a substantial mortality rate in the fourth-instar nymphs and adults of S. purpurascens. The observed mortality was directly proportional to the concentration of conidia. Under controlled conditions, the highest specific death rate K(d⁻¹) was 0.78 for the formulation containing Z + D + MABb1 at 72 h post-infection. The formulations of D + MABb1 and Z + D + MABb1 caused a noticeable decrease in the population of grasshoppers in the experimental plots with statistical significant differences (α < 0.05). Interestingly, an increase in the mortality of S purpurascens occurred in July, August and September 2017 when the highest incidence of the grasshopper was recorded. Remarkably, the treatment based on Z + D + MABb1, produced an improvement in the yields of experimental maize plots (7847.4 ± 0.70 Kg ha⁻¹) in comparison to control plots (4453.9 ± 0.50 Kg ha⁻¹). These favorable consequences are reported for the first time in corn crops from Mexico.     

Importance of mangrove plantations for climate change mitigation in Bangladesh

Mangroves have been identified as blue carbon ecosystems that are natural carbon sinks. In Bangladesh, the establishment of mangrove plantations for coastal protection has occurred since the 1960s, but the plantations may also be a sustainable pathway to enhance carbon sequestration, which can help Bangladesh meet its greenhouse gas (GHG) emission reduction targets, contributing to climate change mitigation. As a part of its Nationally Determined Contribution (NDC) under the Paris Agreement 2016, Bangladesh is committed to limiting the GHG emissions through the expansion of mangrove plantations, but the level of carbon removal that could be achieved through the establishment of plantations has not yet been estimated. The mean ecosystem carbon stock of 5–42 years aged (average age: 25.5 years) mangrove plantations was 190.1 (±30.3) Mg C ha⁻¹, with ecosystem carbon stocks varying regionally. The biomass carbon stock was 60.3 (±5.6) Mg C ha⁻¹ and the soil carbon stock was 129.8 (±24.8) Mg C ha⁻¹ in the top 1 m of which 43.9 Mg C ha⁻¹ was added to the soil after plantation establishment. Plantations at age 5 to 42 years achieved 52% of the mean ecosystem carbon stock calculated for the reference site (Sundarbans natural mangroves). Since 1966, the 28,000 ha of established plantations to the east of the Sundarbans have accumulated approximately 76,607 Mg C year⁻¹ sequestration in biomass and 37,542 Mg C year⁻¹ sequestration in soils, totaling 114,149 Mg C year⁻¹. Continuation of the current plantation success rate would sequester an additional 664,850 Mg C by 2030, which is 4.4% of Bangladesh's 2030 GHG reduction target from all sectors described in its NDC, however, plantations for climate change mitigation would be most effective 20 years after establishment. Higher levels of investment in mangrove plantations and higher plantation establishment success could contribute up to 2,098,093 Mg C to blue carbon sequestration and climate change mitigation in Bangladesh by 2030.     

Effect of rhizobia and rock biofertilizers with <Emphasis Type="Italic">Acidithiobacillus</Emphasis> on cowpea nodulation and nutrients uptake in a tableland soil

Chemical fertilizers have been used in the cultivation of plants due to their high solubility and effect on crops yield. Biofertilizers with phosphate rock (PR) and potash rock (KR) plus sulfur inoculated with Acidithiobacillus may improve plant growth and contribute to addition of available P and K in soil. The effectiveness of biofertilizers from phosphate and potash rocks mixed with sulfur and Acidithiobacillus was studied in a Typic Fragiuldult soil of the Brazilian Northeast Tableland. Cowpea (cv. “IPA 206”) was grown with and without rhizobia inoculation. Treatments were: (a) phosphate rock (1000 kg ha⁻¹); (b) Biofertilizers-B_P (250 and 500 kg ha⁻¹); (c) triple superphosphate-TSP (250 kg ha⁻¹); (d) potash rock (1000 kg ha⁻¹); (e) biofertilizer-B_K (250; 500 and 750 kg ha⁻¹); (f) potassium chloride-KCl (250 kg K₂0 ha⁻¹); (g) control without P or K fertilization (P₀K₀). The soil was maintained under water submersion covered with black plastic (solarization process) for a period of 30 days. Biofertilizers (B_p and B_K) and soluble fertilizers increased plant growth and NPK uptake. Biofertilizers reduced soil pH, especially when applied in highest rates. Biofertilizers and TSP+KCl showed the best values of available P and K in soil. Rhizobial inoculation was effective on cowpea, but no nodules were formed by bacteria native from the soil, probably due to the effect of the solarization process. From obtained PK biofertilizers could be used as alternative for cowpea fertilization in Tableland soils.