Nitrogen Uptake Research Articles

Rice straw incorporation and Azolla application improves agronomic nitrogen-use-efficiency and rice grain yields in paddy fields

In paddy soils, excessive application of N fertilizer often results in substantial N losses due to low N utilization efficiency. However, this condition can be mitigated by enhancing soil organic carbon content. Two-year field experiment was carried out at Mkula Irrigation Scheme in Kilombero Valley, Tanzania with the aim of investigating the impact of Azolla, rice straw incorporation and reduced levels of nitrogen input from NPKS-containing fertilizers on N use efficiency, soil chemical properties and rice grain yield. Assuming that this technology will introduce a novel perspective to the research, shedding light on alternative and potentially more sustainable methods for nitrogen management in paddy soils, it will be particularly relevant in sub-Saharan Africa, where the annual cost of chemical fertilizers is expected to continue rising. The treatments involved absolute control, half dose N (50 kg N ha-1), full dose N (100 kg N ha-1), and combination of these N doses with PKS, dry Azolla (3.4 t ha-1) and rice straw (6.9 t ha-1) through omission approach. The soil of the experimental area was sandy clay loam in texture, very strongly acid (pH 4.8), normal electrical conductivity (0.06 dS m-1), low amounts of recorded organic carbon (1.35%), total nitrogen (0.33%), 0.68 mg kg−1 available P, exchangeable potassium (0.15 cmol(+) kg−1), calcium (0.19 mg kg−1) and sodium percentage (3.75%), with very low cation exchange capacity (1.6 cmol(+) kg−1). The results showed that combination of Azolla, rice straw +100 kg N ha-1 + 30 kg P ha-1 + 30 kg K ha-1 + 20 kg S ha-1 resulted in higher rice grain yield, nitrogen uptake and agronomic efficiency of N. Azolla, being an effective biofertilizer, significantly contributes to nitrogen fixation and soil enrichment. Interestingly, this study demonstrates that co-application of Azolla, rice straw, and 50% reduced N is effective for achieving high rice yields, minimizing over-dependence on chemical N fertilizer, sustainable agricultural development, and environmental conservation.

Impacts of wildfires on boreal forest ecosystem carbon dynamics from 1986 to 2020

Wildfires significantly change boreal forest ecosystem carbon balance through both direct combustion and post-fire carbon dynamics. Affected vegetation influences soil thermal regime and carbon cycling by impacting the surface energy balance of boreal forests. This study uses a process-based biogeochemistry model to quantify carbon budget of North American boreal forests during 1986–2020 based on satellite-derived burn severity data. During the study period, burn severity generally increases. Fires remove ecosystem carbon of 2.4 Pg C and reduce net ecosystem production (NEP) from 32.6 to 0.8 Tg C yr−1, making the forest ecosystems lose 3.5 Pg C, shifting a carbon sink to a source. The canopy’s cooling effect leads to lower soil temperature and lower net primary production due to lower nitrogen mineralization and uptake. Post-fire NEP decreases from 1.6 to 0.8 Tg C yr−1. This reduction accounts for 50% of the simulated NEP when the effects of fire-affected canopy are not considered. Our study highlights the importance of wildfires and their induced-canopy changes in soil thermal and ecosystem carbon dynamics of boreal forests.

Toxic element characterization against a typical high geology background: Pollution enrichment, source tracking, spatial distribution, and ecological risk assessment

The geological environment determines the initial content of various elements in soil, while the late input of toxic elements produced through weathering and leaching is a persistent threat to food security and human health. In this study, we selected the Lou Shao Basin, a black rock system background, and combined geostatistical analysis and multivariate statistics to quantify the specific contribution of weathering of the black rock system, and to analyze the source traces, spatial distributions, and ecological risks of the soil toxicity of elements. The results show that the soils in the study area are acidic, which is related to the weathering of sulfides in the black rock system. The concentrations of most elements in the soil were determined to exceed the soil background values, and the Cd, Se and N contents, exceeded more than five times, especially Se, Mo nearly as high as 13 times. Strong positive correlation between Se, Cu, V and P, low correlation between N and Se, Cu, V, P, Ni and Cd.72.52%, 43%, 77.79%, 82%, 77%, and 44.1% of Cd, Se, Ni, Cu, B, and Mo came from the black rock system, respectively, which were greatly affected by geogenic weathering; V, Zn, Pb, and As are mainly from biomass burning sources; N and P are mainly from agricultural surface sources. Comparison found that the Cd and Se elements in the rocks in the study area were 16.78 times and 1.36 times higher than the world shale average, respectively, and need to pay attention to the weathering process of the two, and the spatial distribution of the 12 elements in soils showed a striped and centralized block distribution pattern, specifically around the distribution of carbonate and metamorphic rocks and other high-geology blocks. The ecological risk results showed that Cd was the main element causing high ecological risk, followed by Se and N, which were at moderate to high ecological risk levels, and Se and N showed similar ecological risk patterns, which may be related to the fact that selenium can promote the uptake and transformation of nitrogen. The present results add to the endogenous sources of toxic elements, quantify the source contributions of toxic elements in soils with high geologic backgrounds, fill this knowledge gap, and provide new insights for pollution control and ecological protection in areas with high geochemical backgrounds.

Transcription factor ZmEREB97 regulates nitrate uptake in maize (Zea mays) roots.

Maize (Zea mays L.) has very strong requirements for nitrogen. However, the molecular mechanisms underlying the regulations of nitrogen uptake and translocation in this species are not fully understood. Here, we report that an APETALA2/ETHYLENE RESPONSE FACTOR (AP2/ERF) transcription factor ZmEREB97 functions as an important regulator in the N signaling network in maize. Predominantly expressed and accumulated in main root and lateral root primordia, ZmEREB97 rapidly responded to nitrate treatment. By overlapping the analyses of differentially expressed genes and conducting a DAP-seq assay, we identified 1,446 potential target genes of ZmEREB97. Among these, 764 genes were coregulated in 2 lines of zmereb97 mutants. Loss of function of ZmEREB97 substantially weakened plant growth under both hydroponic and soil conditions. Physiological characterization of zmereb97 mutant plants demonstrated that reduced biomass and grain yield were both associated with reduced nitrate influx, decreased nitrate content, and less N accumulation. We further demonstrated that ZmEREB97 directly targets and regulates the expression of 6 ZmNRT genes by binding to the GCC-box-related sequences in gene promoters. Collectively, these data suggest that ZmEREB97 is a major positive regulator of the nitrate response and that it plays an important role in optimizing nitrate uptake, offering a target for improvement of nitrogen use efficiency in crops.

Quantifying Nitrogen Uptake Rates of Maize Roots Using Stable Isotopes.

Nitrogen is an essential element for plant growth and development; however, application of nitrogen (N)-based fertilizers comes with a high environmental cost. This includes the energy required for production, volatilization from fields, and runoff or leaching to waterways triggering algal blooms. As such, a key goal in plant breeding programs is to develop varieties that maintain yield while requiring less fertilization. Central to this goal is understanding how roots take up nitrogen and finding traits that represent improvements in the net uptake. Maize, one of the most widely produced crops in the world, has seminal, crown, and brace root types, each under independent developmental control. Recent evidence suggests that these independent developmental patterns may result in different nutrient uptake characteristics. As such, understanding the uptake dynamics of each root type under different environmental conditions is an essential aspect for the selection of new maize varieties. A key method for tracking nitrogen uptake is the use of the 15N stable isotope, which is naturally less abundant than the main 14N isotope. This method involves replacing the 14N in nutrient solutions with 15N, exogenously providing it to the plant tissues (roots in this case), and then measuring the 15N content of the tissues after a fixed amount of time. Here, we provide a brief overview of nitrogen uptake and remobilization in maize, and discuss current techniques for measuring nutrient uptake, with a focus on methods using stable isotopes of nitrogen.

Methods for Measuring Nutrient Uptake in Maize Using Nitrogen Stable Isotopes.

Nitrogen is a key nutrient for plant growth and development, and understanding nutrient uptake is central to improving nitrogen use efficiency in crops, including maize. Reducing the need for fertilizer without reducing yield is extremely important, as nitrogen fertilizers come with a high environmental cost, in terms of both emissions from manufacturing and losses to waterways or volatilization off fields. Maize develops multiple different root types, including primary, seminal, crown, and brace roots. Part of improving efficiency in maize involves understanding the differences in nutrient uptake via each distinct root type, but these differences have been largely ignored to date. Here, we describe a protocol that uses stable isotopes for determining nitrogen uptake rates by maize root types. We describe the steps both for intact roots, for which we use rhizoboxes with openable front windows that allow access to the roots without disturbing the rest of the plant, and for field-grown plants, for which intact analysis is not feasible and requires excising the roots. The methods described here can also be modified to measure uptake kinetics and for monitoring nutrient translocation between roots and shoots. Advancing our understanding of root physiology and nutrient dynamics will improve breeding opportunities for efficient nutrient uptake varieties, reducing the need for fertilizer additions.

The tetraploid wheat (Triticum dicoccum (Schrank) Schuebl.) improves nitrogen uptake and assimilation adaptation to nitrogen-deficit stress.

The genetic diversity in tetraploid wheat provides a genetic pool for improving wheat productivity and environmental resilience. The tetraploid wheat had strong N uptake, translocation, and assimilation capacity under N deficit stress, thus alleviating growth inhibition and plant N loss to maintain healthy development and adapt to environments with low N inputs. Tetraploid wheat with a rich genetic variability provides an indispensable genetic pool for improving wheat yield. Mining the physiological mechanisms of tetraploid wheat in response to nitrogen (N) deficit stress is important for low-N-tolerant wheat breeding. In this study, we selected emmer wheat (Kronos, tetraploid), Yangmai 25 (YM25, hexaploid), and Chinese spring (CS, hexaploid) as materials. We investigated the differences in the response of root morphology, leaf and root N accumulation, N uptake, translocation, and assimilation-related enzymes and gene expression in wheat seedlings of different ploidy under N deficit stress through hydroponic experiments. The tetraploid wheat (Kronos) had stronger adaptability to N deficit stress than the hexaploid wheats (YM25, CS). Kronos had better root growth under low N stress, expanding the N uptake area and enhancing N uptake to maintain higher NO3- and soluble protein contents. Kronos exhibited high TaNRT1.1, TaNRT2.1, and TaNRT2.2 expression in roots, which promoted NO3- uptake, and high TaNRT1.5 and TaNRT1.8 expression in roots and leaves enhanced NO3- translocation to the aboveground. NR and GS activity in roots and leaves of Kronos was higher by increasing the expression of TANIA2, TAGS1, and TAGS2, which enhanced the reduction and assimilation of NO3- as well as the re-assimilation of photorespiratory-released NH4+. Overall, Kronos had strong N uptake, translocation, and assimilation capacity under N deficit stress, alleviating growth inhibition and plant N loss and thus maintaining a healthy development. This study reveals the physiological mechanisms of tetraploid wheat that improve nitrogen uptake and assimilation adaptation under low N stress, which will provide indispensable germplasm resources for elite low-N-tolerant wheat improvement and breeding.

Spacing, Fertilizer and PGPR on Yield and Nutrient Uptake in Industrial Hemp (Cannabis sativa ssp. sativa) and Chemical Properties of Soil

A field experiment was conducted to assess the influence of spacing, fertilizer levels and PGPR on yield and primary nutrients accumulation in different parts of industrial hemp and on chemical properties of soil. The experiment was laid out in Factorial Randomized Complete Block Design, spacing and fertilizers levels with or without PGPR were the factors. The results revealed, plants spaced at 15cm × 10cm registered significant yield of leaves, stems and roots (7.84, 9.80 and 4.20 t ha-1 respectively). The uptake of nitrogen and potassium (450.32 and 159.13 kg ha-1 respectively) was highest in this spacing, while, the phosphorous uptake (75.74 kg ha-1) was maximum in 10cm × 5cm spacing. Among nutrition, 125 percent RDF plus PGPR recorded a significant yield of stem and seed, also, this treatment resulted in maximum uptake of nitrogen and phosphorus (440.33 and 72.58 kg ha-1 respectively) by the plants. It can be inferred that spacing of 15cm × 10cm and application of 10 tonnes FYM with 250:125:250 kg N, P2O5, K2O ha-1 (125% RDF) plus PGPR consortia (Azospirillum brasilense, Pseudomonas fluorescens and Bacillus megaterium @ 5kg each) was found to be optimum to produce higher yields.

Exploring grazing intensity effects: nitrogen uptake in grassland species and soil carbon allocation

Exploring grazing intensity effects: nitrogen uptake in grassland species and soil carbon allocation

Nitrogen uptake rates and phytoplankton composition across contrasting North Atlantic Ocean coastal regimes north and south of Cape Hatteras.

Understanding nitrogen (N) uptake rates respect to nutrient availability and the biogeography of phytoplankton communities is crucial for untangling the complexities of marine ecosystems and the physical, biological, and chemical forces shaping them. In the summer of 2016, we conducted measurements of bulk microbial uptake rates for six 15N-labeled substrates: nitrate, nitrite, ammonium, urea, cyanate, and dissolve free amino acids across distinct marine provinces, including the continental shelf of the Mid-and South Atlantic Bights (MAB and SAB), the Slope Sea, and the Gulf Stream, marking the first instance of simultaneously measuring six different N uptake rates in this dynamic region. Total measured N uptake rates were lowest in the Gulf Stream followed by the SAB. Notably, the MAB exhibited significantly higher N uptake rates compared to the SAB, likely due to the excess levels of pre-existing phosphorus present in the MAB. Together, urea and nitrate uptake contributed approximately 50% of the total N uptake across the study region. Although cyanate uptake rates were consistently low, they accounted for up to 11% of the total measured N uptake at some Gulf Stream stations. Phytoplankton groups were identified based on specific pigment markers, revealing a dominance of diatoms in the shelf community, while Synechococcus, Prochlorococcus, and pico-eukaryotes dominated in oligotrophic Gulf Stream waters. The reported uptake rates in this study were mostly in agreement with previous studies conducted in coastal waters of the North Atlantic Ocean. This study suggests there are distinct regional patterns of N uptake in this physically dynamic region, correlating with nutrient availability and phytoplankton community composition. These findings contribute valuable insights into the intricate interplay of biological and chemical factors shaping N dynamics in disparate marine ecosystems.

Rejuvenating potato growth and yield in challenging semiarid and saline sandy Cholistan: harnessing PGPB-coated N and P application strategies

BackgroundPotato serves as a major non-cereal food crop and income source for small-scale growers in Punjab, Pakistan. Unfortunately, improper fertilization practices have led to low crop yields, worsened by challenging environmental conditions and poor groundwater quality in the Cholistan region. To address this, we conducted an experiment to assess the impact of two fertilizer application approaches on potato cv. Barna using plant growth-promoting bacteria (PGPB) coated biofertilizers. The first approach, termed conventional fertilizer application (CFA), involved four split applications of PGPB-coated fertilizers at a rate of 100:75 kg acre–1 (N and P). The second, modified fertilizer application (MFA), employed nine split applications at a rate of 80:40 kg acre–1.ResultsThe MFA approach significantly improved various plant attributes compared to the CFA. This included increased plant height (28%), stem number (45%), leaf count (46%), leaf area index (36%), leaf thickness (three-folds), chlorophyll content (53%), quantum yield of photosystem II (45%), photosynthetically active radiations (56%), electrochromic shift (5.6%), proton flux (24.6%), proton conductivity (71%), linear electron flow (72%), photosynthetic rate (35%), water use efficiency (76%), and substomatal CO2 (two-folds), and lowered non-photochemical quenching (56%), non-regulatory energy dissipation (33%), transpiration rate (59%), and stomatal conductance (70%). Additionally, the MFA approach resulted in higher tuber production per plant (21%), average tuber weight (21.9%), tuber diameter (24.5%), total tuber yield (29.1%), marketable yield (22.7%), seed-grade yield (9%), specific gravity (9.6%), and soluble solids (7.1%). It also reduced undesirable factors like goli and downgrade yields by 57.6% and 98.8%, respectively. Furthermore, plants under the MFA approach exhibited enhanced nitrogen (27.8%) and phosphorus uptake (40.6%), with improved N (26.1%) and P uptake efficiency (43.7%) compared to the CFA approach.ConclusionThe use of PGPB-coated N and P fertilizers with a higher number of splits at a lower rate significantly boosts potato production in the alkaline sandy soils of Cholistan.

Influence of Four Veterinary Antibiotics on Constructed Treatment Wetland Nitrogen Transformation.

The use of wetlands as a treatment approach for nitrogen in runoff is a common practice in agroecosystems. However, nitrate is not the sole constituent present in agricultural runoff and other biologically active contaminants have the potential to affect nitrate removal efficiency. In this study, the impacts of the combined effects of four common veterinary antibiotics (chlortetracycline, sulfamethazine, lincomycin, monensin) on nitrate-N treatment efficiency in saturated sediments and wetlands were evaluated in a coupled microcosm/mesocosm scale experiment. Veterinary antibiotics were hypothesized to significantly impact nitrogen speciation (e.g., nitrate and ammonium) and nitrogen uptake and transformation processes (e.g., plant uptake and denitrification) within the wetland ecosystems. To test this hypothesis, the coupled study had three objectives: 1. assess veterinary antibiotic impact on nitrogen cycle processes in wetland sediments using microcosm incubations, 2. measure nitrate-N reduction in water of floating treatment wetland systems over time following the introduction of veterinary antibiotic residues, and 3. identify the fate of veterinary antibiotics in floating treatment wetlands using mesocosms. Microcosms containing added mixtures of the veterinary antibiotics had little to no effect at lower concentrations but stimulated denitrification potential rates at higher concentrations. Based on observed changes in the nitrogen loss in the microcosm experiments, floating treatment wetland mesocosms were enriched with 1000 μg L-1 of the antibiotic mixture. Rates of nitrate-N loss observed in mesocosms with the veterinary antibiotic enrichment were consistent with the microcosm experiments in that denitrification was not inhibited, even at the high dosage. In the mesocosm experiments, average nitrate-N removal rates were not found to be impacted by the veterinary antibiotics. Further, veterinary antibiotics were primarily found in the roots of the floating treatment wetland biomass, accumulating approximately 190 mg m-2 of the antibiotic mixture. These findings provide new insight into the impact that veterinary antibiotic mixtures may have on nutrient management strategies for large-scale agricultural operations and the potential for veterinary antibiotic removal in these wetlands.

Response patterns of moss to atmospheric nitrogen deposition and nitrogen saturation in an urban–agro–forest transition

Abstract. Increasing trends of atmospheric nitrogen (N) deposition resulting from a large number of anthropogenic emissions of reactive N are dramatically altering the global biogeochemical cycle of N. Nitrogen uptake by mosses occurs mainly from the atmosphere, making it a competent bio-indicator of N deposition. However, high uncertainties exist when using mosses to indicate N deposition, especially in choosing sampling periods and sampling frequencies. In this study, atmospheric N deposition and moss N content in the urban–agro–forest transition, a region with a high N deposition level of 27.46–43.70 kg N hm−2 yr−1, were monitored, and the method for monitoring atmospheric N deposition by mosses was optimized. We found that the optimal sampling frequency is within 6 months per time, and the optimal sampling times are winter (January and February), autumn (October and November), and summer (July and August), which provides us with a more accurate estimation of atmospheric N deposition than other scenarios. In addition, the moss N content serves as a more reliable N species. This study eventually allowed mosses to be used more effectively and sensibly as an indicator of atmospheric N deposition and helped to improve the accuracy of the model for quantifying N deposition.

Studies on Nutrient uptake, Nutrient use Efficiency and Water Productivity of Drip Irrigated Ratoon Sugarcane as Influenced by Water Soluble Fertilizers

A field experiment was conducted at Zonal Agricultural Research Station, V.C. Farm, Mandya during 2020-21 to study the Nutrient content and Uptake of Drip irrigated Ratoon Sugarcane as influenced by water soluble fertilizers. The experimental site was red sandy loam soil with neutral pH, normal electrical conductivity, medium organic carbon, low available nitrogen, medium phosphorus and potassium content. The experiment was laid out in Randomized Complete Block Design with three replications comprising seven treatments with VCF-0517 sugarcane variety. The results revealed that application of 150 per cent RDF through WSF (325.9 kg ha-1 N, 46.5 kg ha-1 P2O5, 338.4 K2O kg ha-1) recorded significantly higher nitrogen, phosphorus and potassium uptake compared to 100 per cent RDF through WSF (287.3 kg ha-1 N, 37.5 kg ha-1 P2O5, 282.6 kg ha-1 K2O) and 75 per cent RDF through WSF (269.9 kg ha-1 N, 33.4 kg ha-1 P2O5, 253.6 kg ha-1 K2O). Application of WSF at 75 per cent RDF resulted in greater NUE in case of nitrogen, phosphorus and potassium (348.3 kg kg-1, 870.7 kg kg-1 and 696.5 kg kg-1 respectively) when compared with other fertigation levels and conventional fertilizer application.

Kelps may compensate for low nitrate availability by using regenerated forms of nitrogen, including urea and ammonium.

Nitrate, the form of nitrogen often associated with kelp growth, is typically low in summer during periods of high macroalgal growth. More ephemeral, regenerated forms of nitrogen, such as ammonium and urea, are much less studied as sources of nitrogen for kelps, despite the relatively high concentrations of regenerated nitrogen found in the Southern California Bight, where kelps are common. To assess how nitrogen uptake by kelps varies by species and nitrogen form in southern California, USA, we measured uptake rates of nitrate, ammonium, and urea by Macrocystis pyrifera and Eisenia arborea individuals from four regions characterized by differences in nitrogen availability-Orange County, San Pedro, eastern Santa Catalina Island, and western Santa Catalina Island-during the summers of 2021 and 2022. Seawater samples collected at each location showed that overall nitrogen availability was low, but ammonium and urea were often more abundant than nitrate. We also quantified the internal %nitrogen of each kelp blade collected, which was positively associated with ambient environmental nitrogen concentrations at the time of collection. We observed that both kelp species readily took up nitrate, ammonium, and urea, with M. pyrifera taking up nitrate and ammonium more efficiently than E. arborea. Urea uptake efficiency for both species increased as internal percent nitrogen decreased. Our results indicate that lesser-studied, more ephemeral forms of nitrogen can readily be taken up by these kelps, with possible upregulation of urea uptake as nitrogen availability declines.

Dissecting the negative influence mechanisms of microplastics on plant and microbial mediated nitrogen removal in constructed wetlands

The escalating prevalence of microplastics (MPs) in constructed wetlands (CWs) raises concerns about their potential effects on nitrogen (N) removal within these ecosystems. Despite this, systematic investigations into the influence of MPs on N-transformation in CWs, encompassing both phytological and microbial dimensions, are notably lacking. Thus, polyethylene (PE) and polyamide (PA), commonly found in wastewater plants, were studied as typical MPs in CWs over 240 days. Extended accumulation time increased nitrogen inhibition in CWs with PE and PA MPs, notably in PA, reducing TN removal by 7.0 % and 10.5 %. For nitrification process, MPs inhibited the relative abundances (RAs) of genes involved in nitrification and carbon fixation metabolisms in nitrifiers through metagenomic analysis, with PA more significantly inhibiting nitrifying enzyme activities. Regarding denitrification, MPs, especially PA, inhibited the RAs of genes involved in electron production, transport, consumption, ATP production and central carbon metabolism in denitrifiers, and activities of denitrifying enzymes. MPs, particularly PA, were found to elevated ROS level and lactate dehydrogenase release, thus hindering nitrogen transformation. Moreover, MPs caused a reduction in c-di-GMP levels and inhibited genes relevant to biofilm regulation (c-di-GMP signaling and quorum sensing), thereby disturbing extracellular polymeric substance metabolism. Regarding plant systems, MPs, particularly PA, were observed to decrease nitrogen uptake, crucial for N-removal. Additionally, inhibited root activity, reduced photosynthesis, and a compromised antioxidant system also contributed to the diminished N-removal in CWs. Overall, our study systematically reveals how MPs, especially PA, impede nitrogen removal in CWs, contributing to further realize the simultaneous removal of MPs and nitrogen in CWs.

Assessing the efficacy of utilizing biochar derived from oil palm biomass as a planting medium for promoting the growth and development of oil palm seedlings

The recent adoption of biochar in Malaysia's oil palm industry offers numerous benefits, including soil enhancement, resource efficiency improvement, pollution remediation, and greenhouse gas mitigation. With approximately 66.15% of agricultural land dedicated to oil palm cultivation, a substantial amount of biomass, mainly from empty fruit bunch (EFB) and mesocarp fibre (MF), is generated. This study focused on carbonizing MF and EFB at temperatures ranging from 580 to 695 °C to produce biochar. The assessment of biochar's effectiveness as a planting medium in nurseries revealed significantly accelerated growth rates in seedlings cultivated in a composite of biochar and soil. At 8 months-after-treatment (MAT), the BMF-75 treatment showed remarkable growth enhancements, with the highest increase in height (64.9%), number of leaflets (60.5%), and girth size (55.3%) compared to the initial values at 3 MAT, indicating its effectiveness in promoting growth in oil palm seedlings. Additionally, compared to the control group, the biochar-mixed media resulted in favourable outcomes regarding the assimilation of both macro- and micro-nutrients. For instance, nitrogen uptake increased by 2.7% with BMF-50, magnesium by 25.2%, phosphorus by 24.1% with BEFB-75, calcium by 36.8% with BMF-75, chlorine by 10.5% with BMF-50, iron by 25.5% with BEFB-25, copper by 20.1% with BMF-25, and zinc by 6.3% with BMF-25. Additionally, biochar-treated soil exhibited higher organic carbon content, improved cation exchange capacity (CEC), enhanced nitrogen retention with greater biochar proportions, and likely improved soil fertility due to biochar's porous structure. Further potential research can be explored to investigate its long-term effects on oil palm plantation.

Biogeochemical Fluxes of Nickel in the Global Oceans Inferred From a Diagnostic Model

AbstractNickel (Ni) is a micronutrient that plays a role in nitrogen uptake and fixation in the modern ocean and may have affected rates of methanogenesis on geological timescales. Here, we present the results of a diagnostic model of global ocean Ni fluxes which addresses key questions about marine Ni cycling. Sparsely available observations of Ni concentration are first extrapolated into a global gridded climatology using tracers with better observational coverage such as macronutrients, and testing three different machine learning techniques. The physical transport of Ni is then estimated using the ocean circulation inverse model (OCIM2), revealing regions of net convergence or divergence. These diagnostics are not based on any assumption about Ni biogeochemical cycling, but their spatial patterns can be used to infer where biogeochemical processes such as biological Ni uptake and regeneration take place. Although Ni and silicate (Si) have similar concentration patterns in the ocean, we find that the spatial pattern of Ni uptake in the surface ocean is similar to phosphate (P) uptake but not to silicate (Si) uptake. This suggests that their similar distributions arise from different biogeochemical mechanisms, consistent with other evidence showing that Ni is not incorporated into diatom frustules. We find that Ni:P ratios at uptake do not decrease as Ni concentrations approach 2 nM, which challenges the hypothesis of a ∼2 nM pool of non‐bioavailable Ni in the surface ocean. Finally, we find that the net regeneration of Ni occurs deeper in the ocean than for P, though not as deeply as for Si.

Baking quality of wheat variety mixtures: Describing the mechanisms for mixture effects

The use of intra-crop diversity (e.g.: variety mixtures) in bread wheat cropping is getting popular in Europe, mostly for agronomic purposes. However, much less is known about the implications on baking quality.In this paper, we formalized and tested a framework based on two hypothetical mechanisms for mixture effects as a result of plant interactions within mixtures: (i) proportion shifts, relating to changes in grain weight proportion of the varieties at harvest and (ii) component alteration, relating to changes in the baking quality of the component varieties. To test this framework, we measured several baking quality indicators on twelve variety mixtures and their component varieties in pure stands. By recording varietal proportions at harvest, we could measure the relative importance of both mechanisms in explaining observed mixture effects.Our results showed that proportion shifts explained a large share of mixture effects on protein baking quality (Zélény sedimentation index and W baking strength) but failed to explain mixture effects on protein content in one year and Hagberg's falling number in both years. Our results also suggest component alteration on protein content resulting from altered nitrogen uptake in mixtures, and possibly on Hagberg's falling number resulting from lodging reduction in mixtures.

Regulation of photoassimilate transportation and nitrogen uptake to decrease greenhouse gas emissions in ratooning rice with higher economic return by optimized nitrogen supplies

Mechanized harvesting of the main crop rice, with low stubble height in rice ratooning is scaling up, especially in Southeast China with a higher population density and less cultivated land. Currently, the common nitrogen fertilization for ratoon rice is concentrated within 20 days before and after the harvest of the main crop. However, this fertilization pattern may not be suitable for low stubble regenerative rice due to its extended growth period, leading to diminished nitrogen utilization efficiency and heightened greenhouse gas emissions, particularly nitrous oxide (N2O) emissions. It is imperative to explore a nitrogen fertilizer management model for clean production of low stubble ratoon rice (RR). In this study, we examined the effects of nitrogen fertilizer application rates and methods (single or split application) on yield and greenhouse gas emissions during the regrowth season. We employed a multi-criteria assessment approach combined with field measurements, energy analysis, environmental assessment, and economic evaluation on ratoon rice under various nitrogen fertilizer treatments. The results showed that the ratoon rice produced the highest total energy output under 67.5 N+22.5 N (Fertilize with 67.5 kg nitrogen ha−1 and 22.5 kg nitrogen ha−1 3 days after main season rice harvesting and during the heading stage of ratoon rice) treatment compared to the 90 N+0 N (conventional fertilization, apply 90 kg nitrogen ha−1 fertilizer 3 days after harvesting at once) treatment. It was also found that reducing nitrogen application during the tillering stage reduced CH4 emissions, fertilization during the heading stage of the ratoon rice did not increase CH4 emissions, Since fertilization during the heading stage of ratoon rice did not lead to an increase in the partitioning of photoassimilates (photosynthetic product assimilates) to the rhizosphere soil, significant differences in sugar and acetic acid levels were not observed in the rhizosphere soil. As a result, no change was found in the expression of the methanogenic mcrA gene in the microbial community. The study also demonstrated that the 67.5 N+22.5 N treatment was able to promote the absorption of nitrogen nutrients, reduction in N2O emissions by 16.61%, subsequently increasing resource use efficiency, final yield and net ecosystem economic benefit by 5.96%, 7.19% and 5.57%, respectively, thereby decreasing carbon and nitrogen footprints by 6.64% and 3.50% compared with the 90 N+0 N treatment in the ratoon rice. These results suggest that a reasonable ratoon rice cultivation scheme is a promising farming system that can simultaneously improve resource use efficiency and economic profits, reduce greenhouse gas emissions and environmental footprint, while still maintaining the high productivity in ratoon rice.