Nitrogen Fertilizer Recovery Research Articles

Comparison of natural abundance and enriched 15N methods to quantify nitrogen fertilizer recovery in maize under field conditions

Comparison of natural abundance and enriched 15N methods to quantify nitrogen fertilizer recovery in maize under field conditions

Incorporating straw‐derived biochars enhances soil nitrogen accumulation and mitigates nitrogen leaching to facilitates crop productivity of mulching farmland in semiarid regions

AbstractThe long‐term use of film mulching and conventional chemical fertilizers in semiarid regions has resulted in soil degradation and suboptimal fertilizer utilization, necessitating a reevaluation of agricultural practices to enhance resource utilization efficiency and ensure the sustainability of dryland crop production. We conducted a 5‐year study (2017–2021) field experiment in northwest of China, to assess the impact of straw or biochar incorporation on soil water accumulation, crop nitrogen transport, and maize yield under film mulching field. The experiment had six treatments (flat planting without mulching [NN], flat planting with straw incorporation [NS], flat planting with biochar incorporation [NB], film mulching [MN], film mulching with straw incorporation [MS], and film mulching with biochar incorporation [MB]). We undertook a comprehensive assessment over the two growing seasons in 2020–2021. The film mulching and straw/biochar treatments improved soil water storage. The MB treatment significantly decreased 60–200 cm soil NO3−‐N content by 28.37% compared with MN. Biochar incorporation significantly increased soil total and alkali‐hydrolyzable N contents, whereas MS decreased soil alkali‐hydrolyzable N content compared with MN. The maize plant N transportation and grain contribution rates were significantly higher under MS (17.46% and 29.84%) and MB (28.00% and 31.69%) than under MN, respectively. Straw and biochar incorporation significantly increased water use efficiency, nitrogen fertilizer recovery efficiency, and maize yield, on average, by 9.62%, 9.14%, and 14.6%, respectively. In conclusion, incorporating biochar, in particular, positively mitigated N losses, enhanced N utilization efficiency, and increased maize yield in long‐term film mulching farmland in semiarid region.

Fertilizer Application Method Provides an Environmental-Friendly Nitrogen Management Option for Sugarcane

PurposeNitrogen fertilizer management is an important agricultural tool that must be optimized to promote sustainable practices since the nitrogen-fertilizer recovery by plants (NRP) is low, leading to nitrogen losses to the environment. In sugarcane, N-fertilization has been investigated over the years but little attention has been given to N-fertilizer application methods. Sugarcane crop production and environmental impact regarding N-fertilizer application methods (i.e., applied onto the sugarcane straw layer and incorporated into the soil) were investigated in the present study aiming to achieve an environmental-friendly cropping system.MethodsSugarcane yield and NRP, N2O emissions, relevant components of the soil microbiological community and N-fertilizer retention in soil layers were quantified. The experiment was carried out in field conditions where N-fertilizer application methods using 15N-labelled ammonium nitrate (15NH415NO3) were compared to a control treatment with no N-fertilization.ResultsIncorporation of N-fertilizer into the soil increased the sugarcane yield by 17% (two-year average) compared to N-fertilizer applied onto the sugarcane straw layer, which was similar to control treatment. There was an increase in NRP-fertilizer of 79% due to the application of N-fertilizer incorporated into the soil. Furthermore, soil incorporation of N-fertilizer decreased N2O emission by 22% with the fertilizer N emission factor reduced four-fold. The N2O emissions were mostly associated with ammonium-oxidizing bacteria (AOB).ConclusionsOur results show that application of N-fertilizer incorporated into the soil is an environmental-friendly N-fertilization management which will improve agricultural sustainability and reduce environmental impacts.Graphical

Evaluation of Urease and Nitrification Inhibitors in Western Canada

AbstractThe recovery of fertilizer nitrogen by crops in the year of application is usually cited as being about 50%, despite considerable efforts to improve nitrogen efficiencies in agricultural systems. The use of fertilizer additives containing urease and/or nitrification inhibitors may improve fertilizer N efficiency. This was evaluated in four experiments conducted at multiple locations across the Canadian Prairies. Earn 0.5 CEUs in Nutrient Management by reading the article and taking the quiz at https://web.sciencesocieties.org/Learning‐Center/Courses.

Effects of irrigation and nitrogen application on soil water and nitrogen distribution and water-nitrogen utilization of wolfberry in the Yellow River Irrigation Region of Gansu Province, China.

To address the problems of extensive field management, low productivity, and inefficient water and fertilizer utilization in wolfberry (Lycium barbarum L.) production, an appropriate water and nitrogen regulation model was explored to promote the healthy and sustainable development of the wolfberry industry. Based on a field experiment conducted from 2021 to 2022, this study compared and analyzed the effects of four irrigation levels [75%-85% θf (W0, full irrigation), 65%-75% θf (W1, slight water deficit), 55%-65% θf (W2, moderate water deficit), and 45%-55% θf (W3, severe water deficit)] and four nitrogen application levels [0 kg·ha-1 (N0, no nitrogen application), 150 kg·ha-1 (N1, low nitrogen application), 300 kg·ha-1 (N2, medium nitrogen application), and 450 kg·ha-1 (N3, high nitrogen application)] on soil water distribution, soil nitrate nitrogen (NO3 --N) migration, yield, and water-nitrogen use efficiency of wolfberry. The soil moisture content of the 40-80 cm soil layer was higher than those of 0-40cm and 80-120cm soil layer. The average soil moisture content followed the order of W0 > W1 > W2 > W3 and N3 > N2 > N1 > N0. The NO3 --N content in the 0-80 cm soil layer was more sensitive to water and nitrogen regulation, and the cumulative amount of NO3 --N in the soil followed the order of W0 > W1> W2 > W3 and N3 > N2 > N1 > N0 during the vegetative growth period. There was no evidently change in soil NO3 --N accumulation between different treatments during the autumn fruit. The yield of wolfberry under the W1N2 treatment was the highest (2623.09 kg·ha-1), which was 18.04% higher than that under the W0N3 treatment. The average water consumption during each growth period of wolfberry was the highest during the full flowering period, followed by the vegetative growth and full fruit periods, and the lowest during the autumn fruit period. The water use efficiency reached a peak value of 6.83 kg·ha-1·mm-1 under the W1N2 treatment. The nitrogen uptake of fruit and nitrogen fertilizer recovery efficiency of fruit first increased and then decreased with increasing irrigation and nitrogen application. The treatment of W1N2 obtained the highest nitrogen uptake of fruit and nitrogen recovery efficiency of fruit, which were 63.56 kg·ha-1 and 8.17%, respectively. Regression analysis showed that the yield and water-nitrogen use efficiency of wolfberry improved when the irrigation amount ranged from 315.4 to 374.3mm, combined with nitrogen application amounts of 300.0 to 308.3 kg·ha-1. Additionally, the soil NO3 --N residue was reduced, making it an optimal water and nitrogen management model for wolfberry planting. The present findings contribute novel insights into the production of wolfberry with saving water and reducing nitrogen, which helps to improve the level of wolfberry productivity in the Yellow River irrigation region of Gansu Province and other areas with similar climate.

Long term co-application of lime and phosphogypsum increases 15 N recovery and reduces 15 N losses by modulating soil nutrient availability, crop growth and N cycle genes

In no-tillage rotation systems, the recovery of nitrogen (N) fertilizer in the soil–plant system is affected by soil fertility and biological changes caused by the surface application of lime (L) and phosphogypsum (PG). Here we assessed the effect of surface-applied L and/or PG on the fate of 15N-labeled fertilizer, soil chemical properties, microbial gene copy number (16 S rRNA of prokaryotes and genes of N cycle) and grain yield of maize (Zea mays L. intercropped with ruzigrass) in rotation with soybean [Glycine max (L.) Merrill] during two growing seasons. We found that applying L improved soil fertility, particularly when combined with PG (LPG treatment), resulting in higher grain yield. Moreover, compared with the control, the recovery of 15N-labeled ammonium sulfate [(15NH4)2SO4] increased in maize and ruzigrass dry matter but decreased in soybean grown on the residue of the first growing season in two treatments (L and LPG). The losses of 15N-labeled fertilizer were highest in the control and PG treatments. A large amount of 15N-labeled fertilizer was found in the deep layers of PG-amended soil, indicating leaching of fertilizer-derived 15N. Conversely, the analysis of soil microbial N cycle genes revealed that the abundances of denitrifiers were highest in the control (no correctives applied), suggesting that the N fertilizer remaining in the soil increased denitrification rates. Surface application of a combination of L and PG is clearly a feasible strategy for increasing soil fertility, 15N recovery from fertilizer, and grain yield while reducing environmental pollution associated with nitrification and denitrification.

Effect of Natural Liquid Hydroabsorbents on Ammonia Emission from Liquid Nitrogen Fertilizers and Plant Growth of Maize (Zea Mays L.) under Drought Conditions.

The use of mineral nitrogen (N) fertilizers is associated with significant nitrogen loss through the volatilization. Ammonia (NH3) emissions are common from fertilizers with amide (NH2) and ammonium (NH4) nitrogen forms applied to the soil surface without incorporation. The objective of the laboratory and greenhouse pot experiments was to verify the hypothesis that liquid mineral fertilizers and fertilizer solutions containing N-NH2 and N-NH4 applied to the soil surface in combination with natural hydroabsorbents (NHAs) will reduce the volatilization of nitrogen. The effect of NHAs addition to urea ammonium nitrate (UAN) fertilizer and urea, ammonium nitrate (AN) and ammonium sulphate (AS) solutions was evaluated in a laboratory experiment. The effect of the two types of NHAs (acidic and neutral) was compared with the control (UAN) and its mixture with the commercially used urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT). The proportion of volatilized NH3 of the total N from the examined fertilizers applied to the soil surface was determined by the titration method. Subsequently, the effect of fertilization with UAN and its mixture with NHAs and NBPT on the growth of maize under the drought conditions was verified in a greenhouse pot experiment. While the addition of NBPT resulted in a reduction of NH3 emission for the fertilizers containing NH2 (UAN, urea solution), a decrease in volatilization after the addition of both acidic and neutral NHA was observed especially for UAN. A reduction in ammonia emission was also observed for AS after the addition of acidic NHA. The addition of both NHAs and NBPT to UAN increased the utilization of nitrogen from the applied fertilizer, which was reflected by an increase in chlorophyll content and increased CO2 assimilation by maize plants grown under the drought stress. UAN fertilizer combined with acidic NHA and NBPT significantly increased aboveground biomass production and root system capacity of maize. Significant increases in UAN nitrogen recovery were observed for all examined additives (UI and both types of NHAs). In addition to the known effects of hydroabsorbents, especially their influence on soil physical and biological properties and soil water retention, the effect of NHAs application in combination with UAN and AS solutions on the reduction of gaseous N loss, maize plant growth and fertilizer nitrogen recovery was found.

Rethinking discrepancies between difference and 15 N methods for estimating fertilizer nitrogen recovery

Rethinking discrepancies between difference and 15 N methods for estimating fertilizer nitrogen recovery

Impact of Organic and Chemical Nitrogen Fertilizers on the Crop Yield and Fertilizer Use Efficiency of Soybean–Maize Intercropping Systems

The effect of the mixture (1:1) of chemical and organic nitrogen (N) fertilizer on crop yield quality and N fertilizer use efficiency remains elusive. A nitrogen field experiment was conducted in the growing seasons of 2020 and 2021 to investigate the effects of the mixture of chemical and organic N fertilizer on the crop yield, crop quality and nitrogen fertilizer use efficiency in a maize–soybean intercropping system in China. Four treatments applied at 150 kg N ha−1 were used: no nitrogen fertilizer (CK), chemical N fertilizer (ChemF), mixture (1:1) of chemical and organic N fertilizer (ChemF + OrgF) and organic N fertilizer (OrgF). The results showed that the yield and aboveground N accumulation of both soybean and maize increased with the application of fertilizer. The ChemF + OrgF treatment had lower maize and soybean seed yields than for ChemF treatment, but higher than the other two treatments in both years, and the maize yield of the (ChemF + OrgF) treatment was significantly higher (14.9%) in 2021 than 2020. Yields were significantly positively correlated with aboveground N accumulation and fertilizer use efficiency, measured using the nitrogen partial productivity (NPP), nitrogen agronomic efficiency (NAE) and nitrogen fertilizer recovery rate (NFRR). The protein content tended to increase and the oil content tended to decrease under (ChemF + OrgF) applications in soybeans. The (ChemF + OrgF) treatment had the lowest starch content in maize. There was no significant difference in the nitrogen harvest index among treatments, while the NPP, NAE and NFRR were the highest for the application of chemical N fertilizer and significantly decreased with the addition of organic N fertilizer. We conclude that the mixture (1:1) of chemical and organic N fertilizer increased the seed yield and quality of maize, but only the seed yield of soybean.

Response of the Fate of In-Season Fertilizer Nitrogen to Plastic Mulching in Rainfed Maize Croplands of the Loess Plateau.

As plastic mulching is widely used for maize production on Loess Plateau, study of the fate of fertilizer nitrogen (N) in rain-fed croplands is of great significance. Field experiments were conducted during 2015–2016 at a typical dry-land farm on the Loess Plateau, China. The stable isotope tracer technique was applied to analyze the effects of plastic mulching on the maize crop yield, N content in the grain, and mechanism of N uptake and utilization in maize plants with plastic mulch (PM) and without plastic mulch (CK) on the Loess Plateau. Maize yield, aboveground dry matter, grain N concentration, and N uptake in aboveground biomass for PM significantly increased, in addition to fertilizer nitrogen recovery and nitrogen production efficiency. Compared to CK, PM improved the total N uptake from the soil in the aboveground biomass by 16.39 and 27.75 kg ha−1 and fertilizer nitrogen recovery by 10.89 and 22.02 kg ha−1, respectively. Furthermore, PM increased in-season fertilizer N retention in the soil by 11.9–24.8 kg ha−1, and the uncountable fertilizer N decreased by approximately 33.8 kg ha−1 on average. In conclusion, PM simultaneously improved the maize yield and N utilization, which provides a scientific basis for nitrogen management in maize croplands.

Effects of biological nitrification inhibitor in regulating NH3 volatilization and fertilizer nitrogen recovery efficiency in soils under rice cropping.

Biological nitrification inhibitors are exudates from plant roots that can inhibit nitrification, and have advantages over traditional synthetic nitrification inhibitors. However, our understanding of the effects of biological nitrification inhibitors on nitrogen (N) loss and fertilizer N recovery efficiency in staple food crops is limited. In this study, acidic and calcareous soils were selected, and rice growth pot experiments were conducted to investigate the effects of the biological nitrification inhibitor, methyl 3-(4-hydroxyphenyl) propionate (MHPP) and/or a urease inhibitor (N-[n-butyl], thiophosphoric triamide [NBPT]) on NH3 volatilization, N leaching, fertilizer N recovery efficiency under a 20% reduction of the conventional N application rate. Our results show that rice yield and fertilizer N recovery efficiency were more sensitive to reduced N application in the calcareous soil than in the acidic soil. MHPP stimulated NH3 volatilization by 13.2% in acidic soil and 9.06% in calcareous soil but these results were not significant. In the calcareous soil, fertilizer N recovery efficiency significantly increased by 19.3% and 44.4% in the MHPP and NBPT+MHPP groups, respectively, relative to the reduced N treatment, and the rice yield increased by 16.7% in the NBPT+MHPP treatment (P < 0.05). However, such effects were not significant in the acidic soil. MHPP exerted a significant effect on soil ammonia oxidizers, and the response of abundance and community structure of ammonia-oxidizing archaea, ammonia-oxidizing bacteria, and total bacteria to MHPP depended on the soil type. MHPP+NBPT reduced NH3 volatilization, N leaching, and maintaining rice yield for a 20% reduction in conventional N fertilizer application rate. This could represent a viable strategy for more sustainable rice production, despite the inevitable increase in cost for famers.

Recovery of nitrogen fertilizer can be doubled by urea-briquette deep placement in rice paddies

Nitrogen (N) recoveries in rice paddies have barely exceeded 60%, despite the implementation of several management strategies, amounting to significant N being lost to the environment. We conducted field experiments for three consecutive rice growing seasons at two locations in Myanmar to investigate the performance of urea-briquette deep placement (UDP) against variable rates of surface broadcast urea for improving N recovery and yields in rice paddies. The experiment consisted of a control (N0), 77.6 kg N ha−1 as UDP, and surface broadcast urea at 77.6 kg N ha−1 (N78), 100 kg N ha−1 (N100) and 160 kg N ha−1 (N160). Surface broadcast urea was applied in two equal splits at 10 days after transplanting (10 DAT) and at panicle initiation (PI) stage. Urea briquettes (2.7 g) were deep placed (75 mm) in the middle of four rice hills between alternate rows as a single dose at 10 DAT. Microplots receiving 15N labeled urea were installed in each treatment plot (except N100) to trace the fate of the applied N. Nitrogen input almost always produced higher grain yields (p < 0.05) compared to the control. Rice grain yield in the UDP treatment was similar or higher than in the N78, N100 and N160 treatments. Crop dry biomass yield in the UDP treatment was mostly higher (p < 0.05) than in the N78 and always similar to the N160 treatment. Higher crop (47–61%) and soil (24–40%) recovery of 15N was observed in the UDP treatment than in the N78 and N160 treatments, leading to total recoveries of 77–95%. The N78 treatment had crop recoveries of 30–37% and total recoveries of 41–60% and the N160 treatment had crop recoveries of 29–39% and total recoveries of 40–54%. The rice plants in the UDP treatment relied less on native soil N, indicating that the UDP practice can minimize soil N depletion. Our results show that UDP has substantial advantages over surface broadcasting in terms of N fertilizer recovery and may provide environmental benefits.

Root nitrate uptake in sugarcane (Saccharum spp.) is modulated by transcriptional and presumably posttranscriptional regulation of the NRT2.1/NRT3.1 transport system.

Nitrate uptake in sugarcane roots is regulated at the transcriptional and posttranscriptional levels based on the physiological status of the plant and is likely a determinant mechanism for discrimination against nitrate. Sugarcane (Saccharum spp.) is one of the most suitable energy crops for biofuel feedstock, but the reduced recovery of nitrogen (N) fertilizer by sugarcane roots increases the crop carbon footprint. The low nitrogen use efficiency (NUE) of sugarcane has been associated with the significantly low nitrate uptake, which limits the utilization of the large amount of nitrate available in agricultural soils. To understand the regulation of nitrate uptake in sugarcane roots, we identified the major canonical nitrate transporter genes (NRTs-NITRATE TRANSPORTERS) and then determined their expression profiles in roots under contrasting N conditions. Correlation of gene expression with 15N-nitrate uptake revealed that under N deprivation or inorganic N (ammonium or nitrate) supply in N-sufficient roots, the regulation of ScNRT2.1 and ScNRT3.1 expression is the predominant mechanism for the modulation of the activity of the nitrate high-affinity transport system. Conversely, in N-deficient roots, the induction of ScNRT2.1 and ScNRT3.1 transcription is not correlated with the marked repression of nitrate uptake in response to nitrate resupply or high N provision, which suggested the existence of a posttranscriptional regulatory mechanism. Our findings suggested that high-affinity nitrate uptake is regulated at the transcriptional and presumably at the posttranscriptional levels based on the physiological N status and that the regulation of NRT2.1 and NRT3.1 activity is likely a determinant mechanism for the discrimination against nitrate uptake observed in sugarcane roots, which contributes to the low NUE in this crop species.

Simultaneous recovery of nutrients and power generation from source-separated urine based on bioelectrical coupling with the hydrophobic gas permeable tube system

Source-separated urine has been regarded as a precious treasure on account of its rich nitrogen content and is suitable for fertilizer production. In this study, a novel bioelectrical coupling with hydrophobic gas permeable tube system (BGTS) was developed to treat urine, for removing organic matter, and recover nitrogen as value-added products in the form of nitrogen fertilizer. In the presence of the electric field, the hydrolysis process of urea in the anode chamber was accelerated, and the NH4+ driven by electric field force and concentration difference reached the cathode through the cation exchange membrane. The cathode made use of oxygen and electrons to produce alkali in situ to promote the conversion of NH4+ to NH3, which was straightforwardly absorbed in hydrophobic gas permeable tube circulating sulfuric acid solution, so as to promote the rapid migration of nitrogen and build an efficient dynamic recovery of nitrogen. After a 48-h cycle, the BGTS achieved a 95.28 ± 0.60% COD removal ratio, 91.60 ± 0.29% nitrogen recovery efficiency, and 3.48 kg m−3 ammonium sulfate fertilizer. Economic analysis indicated a profit of 5.75 $ associated with the utilization of the BGTS system for nitrogen fertilizer recovery from source separation in urine. Consequently, this study manifested that the BGTS system can recover nitrogen from human urine in a high-recovery and cost-effective way, and is of great significance in the sustainable recovery of nitrogen resources.

Sulfur fertilization strategy affects grass yield, nitrogen uptake, and nitrate leaching: A field lysimeter study#

AbstractBackgroundGlobally and at the European Union level there are mounting concerns regarding nitrogen (N) losses from agricultural systems and pressure to reduce N losses to water and air. Suboptimal plant sulfur (S) availability can reduce plant N efficiency and thereby increase N loss potential. Climate change action demands lower sulfur dioxide emissions thus S deposition levels are at an all‐time low.AimsThe objectives of the current study were to (1) determine the potential for adequate S nutrition to increase grassland yield and N efficiency, (2) determine if alleviating S deficiency reduces nitrate leaching, and (3) evaluate a number of strategies for applying S including the use of cattle slurry.MethodsThis work was completed using a free‐draining sandy loam grassland lysimeter facility. There were six treatments using calcium ammonium nitrate (CAN), CAN + calcium sulfate (CAN+S), ammonium sulfate + CAN (AS+CAN), and slurry (Slurry+CAN and Slurry+CAN+S, respectively) to deliver S strategies. The yield, plant N and S uptake, and nitrate and sulfate leachate were measured to compare treatments.ResultsApplication of mineral S fertilizer increased yields significantly (up to 2,907 kg ha–1) and increased apparent fertilizer nitrogen recovery from 39% to 47–49%. Alleviating S deficiency also significantly decreased nitrate leaching to levels not differing significantly from the control. There was a reduction of 46% in nitrate leaching with the addition of mineral S (CAN+S and AS+CAN) compared to N only. The nitrate concentration standard for drinking water was not breached for treatments that included S (6.6–11 mg NO3–‐N L–1), whereas it was breached for those without S (23–40 mg NO3–‐N L–1). The S applied in the slurry treatment was not adequate (9 kg S ha–1) to meet plant requirements.ConclusionThis study provides evidence that optimization of S nutrition has the potential to deliver large agronomic and environmental benefits along with potential as a nitrate leaching migration strategy on S‐deficient soils.

Effects of free air temperature increase on nitrogen utilization of rice in northeastern China

<p id="C3">Northeastern China is one of the regions where are experiencing the most significant global warming trend. Revealing the effects of anticipated warming on nitrogen absorption and utilization of rice in northeastern China can provide reference for regional sustainable production of rice and optimal management of nitrogen fertilizer. In this study, the field and pot experiments were setup based on free air temperature increase (FATI) system in Harbin, Heilongjiang province during 2019 to 2020, combined with ¹⁵N isotope tracer technique, to investigate the effects of anticipated warming (+1.5℃) on rice yield, nitrogen utilization, and the fate of fertilizer nitrogen. The results showed that warming treatment (W) promoted rice above-ground dry-matter accumulation. The mean grain yields in field and pot experiments during 2019 and 2020 under warming treatment were higher by 10.4% and 10.8% than those under control (CK), respectively. Compared with CK, the mean total nitrogen uptake of two years under W treatment significantly increased by 21.3%, however, the nitrogen utilization efficiency of rice grains showed a decreased trend. Under W treatment, the nitrogen absorbed from fertilizer decreased significantly, while the nitrogen absorbed by rice from soil increased by 31.1%, resulting in the reduction of 12.5% in fertilizer nitrogen recovery rate and the increase of 14.2% in fertilizer nitrogen loss rate. Overall, warming tended to increase rice grain yield, but decreased the proportion of fertilizer nitrogen uptake by plant, which leading to the decrease in nitrogen use efficiency and the significant increase in nitrogen loss rate. Under the background of climate warming, it was suggested to reasonably increase the transplanting density of rice to make full use of the positive effect of global warming on rice yield, as well as appropriately reduce the amount of nitrogen fertilizer application and optimize the management of nitrogen fertilizer operation to improve the nitrogen use efficiency of rice.

Recovery of nitrogen and phosphorus fertilizer from pig farm biogas slurry and incinerated chicken manure fly ash

There is insufficient land to use the large amount of nitrogen-rich biogas slurry, a potential agricultural nonpoint source pollutant, produced by anaerobic digestion of pig manure on large-scale pig farms in South China, and biochemical treatments of this product are often insufficient for meeting discharge standards. In addition, a large amount of phosphorus-rich fly ash (FA), which has poor phosphorus bioavailability and cannot be directly used in agriculture, is produced by chicken manure incineration. Therefore, there is an urgent need to find a way to treat this solid waste. This study explores the possibility of synergistic management and comprehensive utilization of these two wastes. The results indicated that the leaching effect of sulfuric acid was better than that of hydrochloric acid, citric acid and oxalic acid in phosphorus extraction from FA. When the amount of sulfuric acid used was 0.75 mol/L, L/S was 10, and the leaching time was 120 min, 87.33% of the phosphorus in FA was extracted; when the wastewater pH was 9.5 and the molar ratio of Mg:N:P was 1:1:2, 95.43% of ammonia nitrogen was recovered from the pig farm biogas slurry. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses indicated that the main component of the resulting NP fertilizer was struvite, and pot experiments showed that this NP fertilizer was more effective than superphosphate (SP) for plant growth. The residual wastewater met discharge standards after SBR treatment. The present research shows that two different agricultural wastes from one farm, N-rich biogas slurry and P-rich FA, can be treated together to yield recycled NP fertilizers and that the residual wastewater meets the standards for discharge. This study provides an innovative method for the comprehensive treatment and resource utilization of waste in modern and large-scale farms.

Fertilizer nitrogen recovery of irrigated spring malt barley

AbstractWell‐defined nitrogen (N) management in irrigated two‐row malting barley (Hordeum vulgare L.) is critical for yield and quality and to minimize environmental impacts. Data on fertilizer N recovery efficiency (FNRE) and the fate of fertilizer‐N in the soil are lacking. The study objective was to determine uptake and partitioning of 15N‐labeled urea in the plant and soil. Urea was either surface applied or incorporated at a total N rate (inorganic‐N + applied N) of 214 kg N ha–1 at planting. Three malt cultivars were grown, and samples were collected four times during the growing season (Feekes growth stages 4/5, 10.0, 11.2, and 11.4). Barley plants at Feekes 11.2 and 11.4 were separated into vegetative tissue and spikes. Plant N accumulation was lowest at Feekes 4/5 and reached a maximum at Feekes 11.2, whereas FNRE was greatest at Feekes 10.0. Nitrogen was redistributed from vegetative tissue to the spike from Feekes 11.2 to 11.4. Plant FNRE averaged 43% at Feekes 11.4. Total plant–soil FNRE for the surface application was 66%, which was less than the incorporated FNRE of 77%. Results provide evidence of the increased plant–soil system FNRE of incorporated applications in high‐input barley production systems compared with surface applications despite no yield difference. Similar FNRE as compared to previous work with lower yields was measured, and modern cultivars out‐yielded an older cultivar with no reduction in FNRE. Results of the study indicate that a relatively high plant–soil system FNRE of irrigated malting barley was achieved under high‐input, irrigated conditions common in southern Idaho.

Nitrogen-fertilizer recovery from urban sewage via gas permeable membrane: Process analysis, modeling, and intensification

Feasibility of recovering nitrogen (N)-fertilizers from sewage has gained attention recently due to concerns about the sustainability of the Haber-Bosch process in producing N-fertilizers and of the nitrification–denitrification processes in removing N from wastewaters. This study proposes a non-pressurized gas permeable membrane reactor (GPMR) with the potential to recover high-purity N-fertilizer at lower energy demand than current technologies. Performance of the GPMR in recovering N-fertilizer from the following two waste streams of sewage-origin is demonstrated: 1) centrate generated by anaerobic digestion of primary and secondary sludge; and 2) aqueous phase generated by hydrothermal liquefaction of sewage-grown algal biomass. A process model developed for the GPMR was calibrated using test results on a synthetic feed, and validated using results from the tests on the above two waste streams. Temporal ammoniacal-N concentrations predicted by the model agreed well with the measured values (r2 = 0.82; n = 70). Tests conducted on the two wastes at 24–25 °C indicated that feed-side pH of 10 and mild mixing of the feed maximized N-fertilizer recovery. The GPMR was able to recover 80–100% of ammoniacal-nitrogen from both waste streams, yielding 2–86 g of ammonium sulfate from 1 L of the feed. Energy dispersive X-ray analysis and heavy metal analysis of ammonium sulfate recovered from both feeds confirmed compliance with the US Environmental Protection Agency limits for use as fertilizer. Confocal microscopic images of virgin and used membrane surfaces were examined to assess membrane fouling. A process intensification analysis was performed to relate the physical parameters to the performance of the GPMR and to identify areas for further studies.

Sewage sludge biochar increases nitrogen fertilizer recovery: Evidence from a 15N tracer field study

AbstractSewage sludge‐derived biochar (SSBC) could improve nitrogen (N) use efficiency (NUE) and reduce the use of mineral N fertilizers in agriculture. However, information on the residual effect (after stopping amendment) of SSBC on NUE is scarce, but necessary, to evaluate how often biochar should be applied to agricultural crops. In this study, the residual effect of SSBC produced at different temperatures on NUE of corn, by using the 15N isotope tracer, was investigated. The following treatments were assessed in a tropical field study carried out for four years: (a) MF—mineral fertilizer application with nitrogen, phosphorus and potassium (NPK); (b) MF + SSBC produced at 300°C (B3 + MF); and (c) MF + SSBC produced at 500°C (B5 + MF). The contents of soil total N (TN), N in corn derived from the soil (NDS) and from mineral fertilizer (NDMF) were determined. In addition, the N‐fertilizer recovery efficiency (NFRE) in the corn grains and straw was evaluated. Application of SSBC increased N uptake by corn from both the fertilizer (NDMF) and the soil (NDS). All treatments presented similar grain yields. On average, the plants took up N predominantly from soil (88.5 kg ha‒1 in straw; 68.7 kg ha‒1 in grains) compared with mineral fertilizer (51.9 kg ha‒1 in straw; 62.3 kg ha‒1 in grains). Results of the current study indicate that SSBC is able to improve the N use efficiency, even two years after amendment, and consequently, it may reduce the use of mineral fertilizers in agriculture.