Reduce Ammonia Volatilization Research Articles

Stover mulching in no-tillage farming reduces ammonia volatilization in the Mollisol of Northeast China: Insights from gross N transformation dynamics

Ammonia (NH3) volatilization, a critical pathway of nitrogen (N) loss in agroecosystems, is closely regulated by ammonium (NH4+-N) availability and associated NH4+-N transformation dynamics in soil. To determine the effect of no-tillage and crop stover retention on soil internal gross N transformation and further NH3 volatilization in the long-term conservation tillage (CT) agroecosystem, a combination of 15N-tracing field monitoring and paired 15N-labeled incubation experiments was simultaneously conducted on a 9-year maize cropping system in the Mollisol of Northeast China. Three treatments were set up: traditional ridge tillage (RT), no-tillage with maize stover removal (NT0), and no-tillage with full harvest (ca. 7500 kg ha−1 yr−1) maize stover mulching (NTS). It was found that NH3 volatilization in the experimental Mollisol primarily occurred within 7 days after fertilization. Given that the paired gross NH4+-N transformation dynamics were considered in terms of the mutual production-consumption processes, the low fertilizer-derived NH3 volatilization was mainly attributed to a high gross N transformation rate combined with a low net N transformation rate for all treated plots, indicating that there was a rapid internal NH4+-N turnover in the studied Mollisols. Additionally, no-tillage with maize stover mulching considerably reduced NH3 emissions by 17% compared with RT treatment, and the inhibitory effect was primarily owing to the synchronized stimulation of biotic mineralization-immobilization and abiotic adsorption-release turnover in the CT agroecosystem. These findings suggest that long-term no-tillage with maize stover mulching could be a sustainable management strategy for improving soil NH4+-N retention and mitigating NH3 losses in the Mollisol of Northeast China.

Long term response and adaptation of farmland water, carbon and nitrogen balances to climate change in arid to semi-arid regions

Climate change poses a challenge for resource utilization and environmental pollution issues caused by agricultural production, especially in arid to semi-arid regions. Farmland water, carbon and nitrogen balances are closely related to these resource and environmental issues. Thus, the Agro-Hydrological & chemical and Crop systems simulator was used to assess the response of water, carbon and nitrogen balances to climate change in a spring wheat farmland of arid to semi-arid Northwest China and to propose adaptation strategies. Five Global Climate Models from the Coupled Model Intercomparison Project 6 and two Shared Socioeconomic Pathways (SSP1–2.6 and SSP5–8.5) were used to establish scenarios with the Agro-Hydrological & chemical and Crop systems simulator to simulate farmland water, carbon and nitrogen balances for the 2025–2100 period. Various irrigation amounts and nitrogen fertilization rates were tested as compensation strategies. Results indicated that climate change could negatively affect farmland water, carbon and nitrogen balances, especially under the SSP5–8.5 scenario. Precipitation showed an increasing trend, thus percolation increased and soil water consumption decreased from 2025 to 2100. However, for the carbon budget, although the soil carbon dioxide emissions tend to decrease, the net primary production was also significantly reduced, which resulted in declining the net ecosystem carbon budget under future climatic conditions. In addition, higher temperature and increased precipitation enhanced soil inorganic nitrogen leaching and nitrous oxide emissions but reduced ammonia volatilization from 2025 to 2100. Overall, the soil total nitrogen loss was increased over time, whereas crop nitrogen uptake was significantly reduced. In relation to the SSP1–2.6 scenario, the SSP5–8.5 scenario accelerated the increase rates of soil water percolation and total nitrogen loss over time, as well as the decrease rates of crop nitrogen uptake and net primary production over time. The negative effects caused by climate change can be mitigated by reducing irrigation and increasing nitrogen fertilization. For the SSP1–2.6 scenario, 30% irrigation reduction and 30% nitrogen fertilization increase can effectively decrease soil water percolation and the related nitrogen losses while crop nitrogen uptake, net primary production and net ecosystem carbon budget increase in relation to the current management (irrigation = 240 mm and nitrogen fertilization = 200 kg ha–1). For SSP5–8.5 the strategy with 45% irrigation reduction and 45% nitrogen fertilization increase can also decrease nitrogen losses and increase crop nitrogen uptake, net primary production and net ecosystem carbon budget.

Biochar with nitrapyrin reduces ammonia volatilization and increases nitrogen use efficiency of cabbage: A 15N tracer study

Biochar with nitrapyrin reduces ammonia volatilization and increases nitrogen use efficiency of cabbage: A 15N tracer study

Long-term application of controlled-release urea reduced ammonia volatilization, raising the risk of N2O emissions and improved summer maize yield

ContextWith the extensive promotion of controlled-release urea (CRU), its N-release pattern has been shown to match the crop’s N-demand period and improve crop yield by reducing N losses. Nevertheless, the impacts of CRU on summer maize yield, especially on greenhouse gas emissions, have rarely been reported during its long-term use. ObjectiveIt is necessary through long-term positioning field experiment with CRU application to investigate the regulatory mechanisms of maize yield formation, nitrogen use efficiency (NUE), ammonia volatilization and greenhouse gas emissions. MethodsThe long-term fertilizer positioning experiment for ten years, four treatments were performed: polymeric-coated controlled-release urea (CRF, 42% N, 3-months controlled-release period), sulfur-coated controlled-release urea (SCF, 35% N, 3-months controlled-release period), common urea (CCF, 46% N) and no nitrogen fertilizer (CK). ResultsResults showed that the two coated controlled-release fertilizers significantly increased NUE and dry matter accumulation in summer maize, and ultimately improved grain yield. Compared to CCF, CRF and SCF treatments increased post-silking dry matter accumulation by 16.3% and 13.3%; NUE by 42.3% and 28.9%. The 2-year mean grain yield of CRF and SCF treatment increased 9.0% and 12.4% compared to CCF treatment. CRF treatment significantly increased the NO3--N content in 0–60 cm soil layer; while CRF and SCF treatments showed a significantly higher NH4+-N concentration in the 0–20 cm soil layer than CCF treatment. Compared to CCF treatment, the CRF and SCF treatments significantly reduced peak ammonia volatilization, and the average cumulative emissions of ammonia volatilization of two years were reduced by 80.8% and 53.2%, respectively. CRF treatment had lower peak of N2O emissions but longer N2O emission duration than other N application treatments. The two-year average cumulative N2O emissions from CRF treatment increased by 49.6%, and SCF treatment increased by 61.1% compared to CCF treatment. Compared to CK treatment, total cumulative CH4 uptake was 36.1% lower in CRF treatment, 60.9% in SCF and 78.9% in CCF treatment. The higher cumulative N2O emissions from CRF and SCF treatment resulted in a significantly higher global warming potential (GWP) than CCF treatment. The two-year mean increase in greenhouse gas intensity (GHGI) was 36.2% for CRF treatment and 44.7% for SCF treatment compared to CCF treatment. ConclusionsLong-term application of coated controlled-release fertilizers could achieve high yields and nitrogen use efficiency. However, there is a risk of increased N2O emissions, causing elevated GHGI. SignificanceIn the future, it is necessary to strengthen the research on the comprehensive effects of long-term reduced application of CRU on crop yield and greenhouse gas emissions, in order to promote the wide application of environmentally friendly CRU in the field.

Different crystalline manganese dioxide and biochar co-conditioning aerobic composting: Reduced ammonia volatilization and improved organic fertilizer quality

Aerobic composting is a sustainable and effective waste disposal method. However, it can generate massive amounts of ammonia (NH3) via volatilization. Effectively reducing NH3 volatilization is vital for advancing aerobic composting and protecting the ecological environment. Herein, two crystal types of MnO2 (α-MnO2 and δ-MnO2) are combined with biochar (hydrochar (WHC) and pyrochar (WPC), respectively) and used as conditioners for the aerobic composting of chicken manure. Results reveal that α-MnO2 (34.6%) can more effectively reduce NH3 accumulation than δ-MnO2 (27.1%). Moreover, the combination of WHC and MnO2 better reduces NH3 volatilization (48.5–58.9%) than the combination of WPC and MnO2 (15.8–40.1%). The highest NH3 volatilization reduction effect (58.9%) is achieved using the combination of WHC and δ-MnO2. Because the added WHC and δ-MnO2 promote the humification of the compost, the humic acid to fulvic acid ratio (HA/FA ratio) dramatically increases. The combination of WHC and δ-MnO2 doubled the HA/FA ratio and resulted in a net economic benefit of 130.0 RMB/t. Therefore, WHC and δ-MnO2 co-conditioning can promote compost decomposition, improving the quality of organic fertilizers and substantially reducing NH3 volatilization.

Effects of biochar combined with MgO desulfurization waste residue on nitrogen conversion and odor emission in chicken manure composting

ABSTRACT Aim: Chicken manure is known to produce strong odors during aerobic composting, which not only pollutes the surrounding environment but also leads to the loss of valuable nutrients like nitrogen and sulfur, thus reducing the quality of the fertilizer. Methods: In this study, we explored the use of biochar combined with MgO desulfurization waste residue (MDWR) as a novel composting additive. Our approach involved conducting composting tests, characterizing the compost samples, conducting pot experiments, and examining the impact of the additives on nitrogen retention, deodorization, and compost quality. Results: Our findings revealed that the addition of biochar and MDWR significantly reduced ammonia volatilization in chicken manure compost, demonstrating a reduction rate of up to 60.12%. Additionally, the emission of volatile organic compounds (VOCs) from chicken manure compost treated with biochar and MDWR decreased by 44.63% compared to the control group. Conclusions: The composting product treated with both biochar and MDWR (CMB) exhibited a 67.7% increase in total nitrogen (TN) compared to the blank control group, surpassing the other treatment groups and showcasing the synergistic effect of these two additives on nitrogen retention. Moreover, the CMB treatment facilitated the formation of struvite crystals. Furthermore, our pot experiment results demonstrated that the CMB treatment enhanced vegetable yield and quality while reducing nitrate content. These findings highlight the significant impact of MDWR on nitrogen retention, deodorization, and compost quality enhancement, thereby indicating its promising application prospects.

Reduction of NH3 Emissions from Urea by Long-Term No-Tillage and Stover Mulching with Inhibitors: An Isotopic Field Study in Northeast China

Large nitrogen (N) losses during fertilization in agricultural production may result in energy wastage, soil and water contamination, and potentially influence crop development. Thus, with the help of a 15N-labeled tracer, we carried out a field monitoring analysis of NH3 emissions in a long-term (9-year) conservation tillage agroecosystem of Mollisols in northeast China, in order to determine whether a no-tillage regime and four levels of stover mulching (0%, 33%, 67%, and 100%), combined with urease and nitrification inhibitors, could improve fertilizer utilization efficiency in agricultural systems by reducing ammonia volatilization. Our results showed that in comparison with ridge tillage, no-tillage with stover mulching levels of 33%, 67%, and 100% significantly reduced NH3 emission rates and cumulative volatilization from 159.67 to 130.42 g N ha−1 and 15N-NH3 cumulative volatilization emission by 26% (on average). Furthermore, the application of urease and nitrification inhibitors significantly reduced 15N-NH3 volatilization levels from 1.19 to 0.98 g N ha−1. Our research results demonstrate that a long-term no-tillage regime and straw mulching can significantly reduce NH3 volatilization in fertilizers. Furthermore, when combined with the use of urease and nitrification inhibitors, these practices further enhance the reduction in NH3 volatilization. Although the volatilization of 15N-NH3 is minimally studied in Mollisols, these findings provide a solid foundation for improving fertilizer utilization efficiency, reducing crop production costs and mitigating subsequent environmental pollution.

Temperature response of ammonia emission from sandy loam soil amended with manure compost and urea

Ammonia (NH3) emission is an atmospheric pollutant that harms the environment and public health. Although the use of nitrogen (N) - based fertilizer to increase crop output is a significant source of NH3 emissions, it is unclear what factors speed up this process. A laboratory incubation study using the dynamic chamber method was performed to evaluate the impact of manure compost and N rates on NH3 emission at different temperatures (15, 25, and 35 °C). The ammonia emission from sandy loam soil treated with compost at 110 kg N ha−1 (CU0) and urea at 100, 200, and 400 kg N ha−1: CU1, CU2, and CU3, respectively, were monitored for 28 days. The result showed that cumulative NH3 emission increased with temperature and N application rates. At the three temperature regimes, N loss via NH3 emission ranged between 7.2 and 8.3, 8.04 and 12.78, and 13.79 and 44.78 percent of N applied to CU1, CU2, and CU3, respectively. The activation energy was highest in CU3 treatments in all the temperature regimes resulting in 36%–60% higher compared to others. The temperature quotient (Q10) of NH3 emission ranged between 0.28 and 8.06 and 0.18 and 14.91 at 15–25 °C and 25–35 °C, respectively. This study demonstrated that the application of compost (110 kg N ha−1) and urea (100 or 200 kg N ha−1) at low temperatures (< 25 °C) is a good strategy to reduce ammonia volatilization, improve N use efficiency and soil properties.

Tofu by-product soy whey substitutes urea: Reduced ammonia volatilization, enhanced soil fertility and improved fruit quality in cherry tomato production

Soy whey is an abundant, nutrient-rich and safe wastewater produced in tofu processing, so it is necessary to valorize it instead of discarding it as sewage. Whether soy whey can be used as a fertilizer substitute for agricultural production is unclear. In this study, the effects of soy whey serving as a nitrogen source to substitute urea on soil NH3 volatilization, dissolved organic matter (DOM) components and cherry tomato qualities were investigated by soil column experiment. Results showed that the soil NH4+-N concentrations and pH values of the 50% soy whey fertilizer combined with 50% urea (50%-SW) and 100% soy whey fertilizer (100%-SW) treatments were lower than those of 100% urea treatment (CKU). Compared with CKU, 50%-SW and 100%-SW treatments increased the abundance of ammonia oxidizing bacteria (AOB) by 6.52–100.89%, protease activity by 66.22–83.78%, the contents of total organic carbon (TOC) by 16.97–35.64%, humification index (HIX) of soil DOM by 13.57–17.99%, and average weight per fruit of cherry tomato by 13.46–18.56%, respectively. Moreover, soy whey as liquid organic fertilizer reduced the soil NH3 volatilization by 18.65–25.27% and the fertilization cost by 25.94–51.87% compared with CKU. This study provides a promising option with economic and environmental benefits for soy whey utilization and cherry tomato production, which contributes to the win-win effectiveness of sustainable production for both the soy products industry and agriculture.

Trace metal uptake in forage systems receiving long‐term applications of alum‐treated or untreated poultry litter

AbstractTreating poultry litter with alum (Al2[SO4]3·14H2O) is a commonly used best management strategy for reducing ammonia (NH3) volatilization and phosphorus (P) runoff and leaching. However, little is known about how this amendment affects trace metal availability and uptake by forages, as well as potential issues with phytotoxicity, toxicity to grazing animals, and overall yield. The objective of this study was to determine longitudinal effects of alum‐treated poultry litter, untreated litter, ammonium nitrate, and an unfertilized control on trace metal (As, Cu, Se, and Zn) and S concentrations and uptake by tall fescue (Festuca arundinacea Schreb.), yield, as well as availability in soil over 20 years. Greater (p &lt; 0.05) Mehlich‐3 extractable soil As and subsequent forage As uptake occurred with alum beyond the 6.72 Mg ha−1 rate; however, forage As concentrations were not affected by alum. Forage yields were greater with alum‐treated and untreated litters than with ammonium nitrate applied at the same N rate. Treating litter with alum generally did not improve tall fescue yields, except at the lowest litter rate (2.24 Mg ha−1). Alum treatment of poultry litter has been shown to be a cost‐effective best management practice that reduces ammonia volatilization, which improves air quality and poultry production, while reducing P and heavy metal runoff and ultimately improving water quality. Given that trace metal and S concentrations in forages were all in the normal ranges, treating poultry litter with alum does not pose issues with respect to metal phytotoxicity and/or toxicity to grazing animals.

Value-Added Fertilizers Enhanced Growth, Yield and Nutrient Use Efficiency through Reduced Ammonia Volatilization Losses under Maize–Rice Cropping Cultivation

Plant nutrition is an essential element for crop production and enormous amounts of fertilizers are used in agricultural systems. However, these sources emit toxic gasses and compounds in the environment that not only deteriorate soil quality but also cause a reduction in the use efficiency of applied nutrients. Therefore, the value addition of these fertilizer sources by coating micronutrients, microbes, polymers or other organic and inorganic compounds have been advocated recently. The present study aimed to evaluate the effectiveness of value-added fertilizer sources for growth and yield improvement of Zea mays (Pioneer-30T60) and Oryza sativa (Super Basmati-515) with a reduction in ammonia volatilization and an improvement in nutrient recovery by crop grains. Different phosphorus (P), potassium (K) and nitrogen (N) fertilizer sources (Di-ammonium phosphate (DAP), polymer coated DAP, zarkhez plus NPK, urea, polymer-coated urea and zabardast urea) were used in different combinations keeping one control for N. The results revealed that maximum growth, yield and nutrient recovery was shown by polymer-coated urea and DAP followed by zarkhez plus NPK and zabardast urea. Moreover, a minimum ammonia emission was recorded by polymer-coated fertilizers, but other value-added fertilizers were found inefficient in reducing ammonia emission, though these sources improved all growth and yield attributes. Nutrient recovery efficiency was patterned as; polymer coated fertilizers &gt; zarkhez plus NPK + zabardast urea &gt; zarkhez plus NPK + urea &gt; DAP + zabardast urea &gt; DAP + urea &gt; DAP. Thus, the use of polymer-coated fertilizers was beneficial for both the reduction in ammonia volatilization and for improving nutrient use efficiency with maximum crop benefits.

Effect of Deep Fertilization with Slow/Controlled Release Fertilizer on N Fate in Clayey Soil Wheat Field

Clayey soil seriously affects water-holding capacity and nutrient movement. Adopting appropriate agronomic measures to optimize the distribution of soil inorganic nitrogen (SIN) and reduce the nitrogen (N) loss in this soil is the key to agricultural sustainable development. To clarify the effect of deep fertilization of slow/controlled release fertilizer with sowing on N loss in a clayey soil wheat field, two types of fertilizers, conventional fertilizer (CN) and slow/controlled release fertilizer (RCU), were selected in this study. Here, we evaluated the effects of these two fertilizer types on wheat yield, seasonal N runoff loss, ammonia volatilization, and N2O emissions in wheat fields in two typical fertilization modes (manual surface sowing and spreading (B) and belowground fertilization of slow/controlled release urea with mechanized strip sowing (D)). The temporal and spatial distribution characteristics of SIN in topsoil were also analyzed. The results showed that under the same fertilizer type, the wheat yield of D treatment was significantly higher than that of B treatment, whereas the yield of RCU was notably higher than that of CN under the same fertilization mode. D-RCU achieved the highest yield of 6.97 t·hm-2. The seasonal N losses from runoff and ammonia volatilization were higher than that from N2O emissions, and the responses of different N loss pathways to fertilizer types and fertilization methods were diverse. Fertilizer type and runoff occurrence time were the main influencing factors of N runoff loss, and N runoff loss of the RCU treatment was higher in the non-fertilization period. Unfortunately, affected by annual rainfall pattern, the seasonal N runoff loss of the RCU treatment (20.35 kg·hm-2) was significantly higher than that of the CN treatment (10.49 kg·hm-2). The late growth period was the main phase of ammonia volatilization, and the later period was jointly affected by fertilization modes and fertilizer types. The B-CN treatment induced the highest seasonal ammonia volatilization (18.15 kg·hm-2), which was significantly higher than that of the other treatments (7.31-8.38 kg·hm-2). Additionally, the D-RCU treatment (2.41 kg·hm-2) tended to reduce the N2O emissions in comparison to that in the B-CN treatment (4.02 kg·hm-2). The results also indicated that the horizontal movement of SIN was higher than the vertical movement. Deep fertilization of RCU was conducive to optimizing the spatial and temporal distribution of SIN, which was the main reason for the increase in wheat yield and the control of N loss from wheat fields. These results suggest that RCU is a suitable alternative fertilizer for increasing yield and reducing N loss in clayey soil wheat fields; D-RCU can increase the wheat yield and reduce ammonia volatilization and N2O emissions in wheat fields by optimizing the spatial and temporal distribution of SIN, and its increasing effect on N runoff loss in the non-fertilization period deserves attention.

Dynamics of ammonia volatilization from NBPT-treated urea in tropical acid soils

The urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) reduces NH3 losses from urea (UR) surface-applied to soils, but its efficacy may be lower in acidic soils. The period when urease inhibition occurs efficaciously may change with soil pH. This needs to be clarified in tropical soils which are commonly acidic. This study evaluated the effectiveness of NBPT-treated urea to delay and reduce ammonia volatilization in two soils at three pH levels. Two experiments were conducted under laboratory conditions in soils with different textures (sandy-clay and clay). The treatments consisted of three soil pH levels and two N sources (UR and UR + NBPT), with five replicates. The soil pH values were adjusted and reached values of 4.5, 5.6, and 6.4 in the sandy-clay, and 4.5, 5.4, and 6.1 in the clay soil. Ammonia volatilization was measured using glass chambers (1.5 L). In the sandy-clay soil, NH3 losses were 40-47 % of the UR-N. In the clay soil, losses were 26-32 %. The addition of NBPT to UR reduced the NH3 volatilization by 18-53 %; the inhibitor decreased the N losses under all soil pH conditions but was significantly less efficient in acidic soils (pH 4.5). The lower efficiency of the inhibitor under acidic conditions was more evident in the first few days: 50 % of the total NH3 losses occurred in less than four days in soils with pH 4.5, but in 8-11 days in soils with pH above 5.4. The rapid loss in efficiency in more acidic soils is a drawback. Using NBPT in severely acidic soils showed a relatively small advantage over untreated UR as the inhibitor did not provide extra time for fertilizer incorporation and further reduction of NH3 losses.

Opportunities beyond CO2 for climate mitigation

Opportunities beyond CO2 for climate mitigation

Rotation of planting strips and reduction in nitrogen fertilizer application can reduce nitrogen loss and optimize its balance in maize–peanut intercropping

In dryland farming, maize (Zea mays L.) and peanut (Arachis hypogaea L.) intercropping has been widely practiced to achieve sustainable agriculture goals. However, only a few studies have investigated the effect of reducing nitrogen (N) application on the performance of maize and peanut crops in intercropping system based on rotation of the planting strip. Therefore, a field study was conducted from 2018 to 2020 in Yangling, China, where the treatments comprised peanut monoculture, maize monoculture, maize–peanut intercropping, maize–peanut rotational intercropping, and maize N reduction based on the rotational intercropping system. The N accumulation and yield in maize increased after intercropping, while the N accumulation, yield and N fixation capacity of peanut decreased than other treatments. In addition, soil residual N, ammonia volatilization, N leaching, and N2O emissions of maize–peanut intercropping significantly decreased than maize monoculture. The rotation of planting strips in maize–peanut intercropping had increased the land equivalent ratio by 3.06 % and 9.39 % and N recovery efficiency by 15.45 % and 27.37 % in the second and third years of planting, as well as alleviated the continuous cropping barrier for peanuts. N reduction does not affect N fixation capacity and yield of peanut and reduces ammonia volatilization and N leaching from farmland, although it does influence maize yield. The optimal cropping system was a 20 % N reduction in maize planting strip under rotational intercropping because N accumulation and the farmland productivity were not affected significantly, while the N losses to the environment also decreased by an average of 44.17 % and 14.87 % compared with traditional intercropping and monoculture in the second and third years of planting. These results are useful for optimizing cropping systems to promote sustainable development in dryland regions and mitigate N pollution.

Combing mechanical side-deep fertilization and controlled-release nitrogen fertilizer to increase nitrogen use efficiency by reducing ammonia volatilization in a double rice cropping system

Ammonia (NH3) volatilization losses result in low nitrogen use efficiency (NUE) and various environmental impacts in agroecosystems. Machine-transplanted rice with side-deep fertilization (MRSF) has been recommended as an effective alternative to traditional transplantation with manual broadcasting of fertilizer. Controlled-release nitrogen fertilizer (CRF) can enhance rice yield and NUE in paddy fields. However, there is scarce information about combined effects of MRSF and CRF on NH3 volatilization loss and rice grain yield, NUE, net economic benefit (NEB) in a double rice cropping system. In this study, a field experiment was conducted to evaluate the impact of MRSF with CRF on grain yields, NUE and economic returns of early rice and late rice from 2019 to 2021, as well as NH3 emissions in two rice seasons (2019 and 2021). Six treatments were designed as no N fertilizer (N0), compound fertilizer broadcasting (CFB), compound fertilizer side-deep placement (CFD), CRF broadcasting (CRFB), CRF side-deep placement (CRFD1), and single side-deep placement of CRF (CRFD2). The results showed that the CFD and CRFB treatments decreased NH3 volatilization while enhancing or maintaining rice yield and NUE compared to the CFB treatment. MRSF with CRF (CRFD1 and CRFD2) significantly reduced NH3 emissions of early and late rice by 57.6–67.9% and 62.2–80.9% by decreasing the NH4+–N concentrations in the surface water compared to the CFB treatment, respectively. Rice grain yields in the MRSF with CRF treatments increased by 3.9–17.3% in early rice and 5.4–21.6% in late rice relative to the CFB treatment. In addition, MRSF with CRF treatments improved NUE for early and late rice from 32.1 to 36.2% and 21.3–28.4% in the CFB treatment to 48.4–61.2% and 39.7–62.3%, respectively. The yield-scale NH3 volatilization losses were reduced under the MRSF with CRF treatments by 61.2–71.5% in early rice and 67.4–84.3% in late rice. Furthermore, MRSF with single basal application of CRF reduced time-consuming and labor-intensive while increasing rice yields and net economic benefits. Overall, co-application of MRSF and CRF can reduce NH3 emissions, and improve rice yield, NUE and profitability in double rice cropping systems.

Metal doped nitrogenous hydroxyapatite nanohybrids slowly release nitrogen to crops and mitigate ammonia volatilization: An impact assessment

To supply adequate food, the ongoing and unrestrained administration of nitrogen fertilizer to agricultural fields is polluting the climate and living organisms. On the other hand, the agriculture sector urgently needs a technological upgrade to effectively confront hunger and poverty. Here, we report a rapid synthesis of zinc and magnesium-doped hydroxyapatite-urea nanohybrids for slow release and delivery of nitrogen to wheat and rice crops. Nanohybrids slowly release nitrogen for up to six weeks compared to the burst release of nitrogen from urea, and their use substantially reduces, by at least 3.8 times, ammonia emissions into the environment compared with that of urea fertilizer. A half‑nitrogen dose applied as multi-nutrient complexed nanohybrids maintained crop growth, yield, and nutritional compositions in wheat and subsequent rice crops. Nanohybrids enhanced the wheat crop yield and nitrogen uptake by 22.13% and 58.30%, respectively. The synthesized nitrogen nanohybrids remained in the soil for two continuous crop cycles, reduced ammonia volatilization, and achieved nitrogen delivery to the crops. Additionally, soil dehydrogenase activity (534.55% above control) and urease activities (81.82% above control) suggest that nanohybrids exhibited no adverse impact on soil microorganisms. Our comprehensive study demonstrates the advantages of ‘doping’ as a method for tailoring hydroxyapatite nanoparticles properties for extended agricultural and environmental applications. The use of nanohybrids substantially reduced greenhouse gas emissions and enabled the reduction, by half, of nitrogen inputs into the agricultural fields. This study, therefore, reports a novel nano-enabled platform of engineered hydroxyapatite-urea nanohybrids as a nitrogen fertilizer for efficient nitrogen delivery that results in improved crop growth while minimizing environmental pollution.

Effect of Deep Placement of Large Granular Fertilizer on Ammonia Volatilization, Soil Nitrogen Distribution and Rice Growth

Excessive fertilization is often applied to produce rice. To reduce nitrogen loss and improve nitrogen use efficiency (NUE), we studied the effects of application depth (surface application, 5 and 10 cm) and shape of nitrogen fertilizers (row application and deep application of large granular fertilizer) on rice growth, soil N distribution and ammonia volatilization. The results showed that grain yield, shoot biomass and total dry biomass of the treatment with N in large granular fertilizer applied at 10 cm depth were significantly higher than those of all other treatments. Moreover, compared with the surface application, the N recovery efficiency and the N agronomic efficiency of deep application treatments were enhanced by 18.1–52.3% and 35.6–95.6%, respectively. Deep application significantly increased NH4+-N concentration at their fertilization points. During the growth season, N in large granular fertilizer treatments (mixed with clay to form an unusually large pellet of 1.0–1.5 cm in diameter) distributed closer to the roots, while N in other treatments, including row application treatments, was more widely distributed. Compared with the surface application, deep application significantly reduced NH3 volatilization and NH4+-N concentration in surface water by 58.7–64.8% and 26.0–72.5%, respectively. Furthermore, the NH3 volatilization from large granular treatment was 7.6–11.0% lower than that in the row application. In conclusion, applying N in large granular fertilizer at 10 cm depth reduces ammonia volatilization, and improves rice growth and grain yield, indicating improved NUE and lowered environmental risks.

Negligible ammonia volatilization loss with one-time root-zone targeted application of common nitrogen, phosphorus, and potassium fertilizers in transplanted rice cultivation

The minimization of nitrogen (N) loss and enhancement of efficient N use are of great importance in agricultural crop production. Here we propose a method of one-time root-zone targeted fertilization (ORZTF), to reduce ammonia volatilization (AV) loss and increase N use efficiency. ORZTF is updated from one-time root-zone fertilization (ORZF), in which common N fertilizer is one-time applied in crop root-zone, and phosphate (P) and potassium (K) are surface broadcasted. In ORZTF, common N, P and K are together placed at certain sites in the root-zone. Three rice field trials with the methods of conventional surface broadcasting (CSB), ORZF, and ORZTF, and a soil incubation experiment with CSB and ORZTF, were conducted. In 2018, the treatments comprised CSB with no N (N0), with the local N rate (CSB, 195 kg N hm−2 and 150 kg N hm−2 for two sites, respectively), with higher N (HCSB, 225 kg N hm−2 and 195 kg N hm−2, respectively), ORZF (195 kg N hm−2 and 150 kg N hm−2, respectively), and ORZTF (195 kg N hm−2 and 150 kg N hm−2, respectively). In 2019, the treatments were: N0, CSB, ORZF, ORZTF with urea (ORZTF-U), with ammonium chloride (ORZTF-Cl), and with ammonium sulfate (ORZTF-S) at 180 kg N hm−2. In the incubation experiment, there’re three treatments: N0, CSB, and ORZTF. The rates of P and K were the same in all experiments. Compared with CSB, ORZTF and ORZF significantly increased the yield, N uptake, N recovery efficiency, and N partial factor productivity of rice with the same N input. After 4.5 months of incubation, 78.5–92.7% of fertilizer N was reserved in the soils with ORZTF, about two-fold that with CSB. In all field and incubation experiments, AV loss was negligible when N was one-time root-zone applied alone or together with PK, close to that in N0 treatment. Compared with ORZF, ORZTF seemed to be a more promising method in rice fertilization, having the similar effect on N uptake increase and N loss reduction, but more convenience. Although the benefits of targeting fertilization were not significantly observed in the current work, with the idea of ‘fertilizing the roots but not the soil’, the method of ORZTF with common N, P and K fertilizers should be beneficial for cleaner and more efficient agricultural crop production in China.

Coupling side-deep fertilization with Azolla to reduce ammonia volatilization while achieving a higher net economic benefits in rice cropping system

Ammonia (NH3) volatilization reduces nitrogen (N) use efficiency (NUE) and damages the environment, resulting in economic costs and human health threats. Side-deep fertilization decreases NH3 volatilization and the fertilizer application amount but sometimes risks reducing rice yield because of an unstable N supply. Azolla incorporation can improve NUE and rice yield by biological N fixation in paddy fields. However, the effects of coupling side-deep fertilization with Azolla on NH3 volatilization, NUE, and net economic benefits in rice cropping systems are unclear. Therefore, a two-year field trial was performed in the Taihu Lake region of China with five treatments: (i) a control with no N input (CK), (ii) conventional fertilization using the local practice with three-split broadcasting with 300 kg N ha−1 (CN), (iii) reduced N fertilization with three-split broadcasting with 255 kg N ha−1 (RN), (iv) reduced N fertilization with 60% of urea side-deep placement and with 40% broadcasting (RNS), and (v) combined RNS with Azolla (RNSA). In the two-year field observations, compared with CN, RN decreased NH3 volatilization but tended to reduce rice yield and NUE, and RNS and RNSA significantly decreased NH3 volatilization by 32.42%− 50.65% and 48.65%− 59.72% by decreasing floodwater NH4+-N and pH. In addition, RNSA significantly increased NUE by 23.73% (26.92–30.89%) by enhancing rice root growth and N uptake compared to CN. Moreover, the economic cost of NH3 volatilization in RNSA (548.07–590.67 CNY ha−1) was notably lower than that of CN (1149.99–1302.51 CNY ha−1). The RNSA achieved the maximum net economic benefits (24.72–25.75 * 103 CNY ha−1) with the minimum economic costs of NH3 volatilization. The results provide theoretical support for guiding field production and government decision making.