Controlled-release Nitrogen Fertilizer Research Articles

Effects of urea topdressing time on yield, nitrogen utilization, and quality of mechanical direct-seeding hybrid indica rice under slow-mixed fertilizer base application.

The use of controlled-release nitrogen (N) fertilizers has been shown to improve yield and N-use efficiency (NUE) in mechanical transplanted rice. However, the fertilizer requirements for mechanical direct-seeding rice differ from those for mechanical transplanted rice. The effects of controlled-release fertilizers on yield, NUE, and quality in mechanical direct-seeding rice are still unknown. Hybrid indica rice varieties Yixiangyou 2115 and Fyou 498 were used as test materials, and slow-mixed N fertilizer (120kg hm-2) as a base (N1), N1+urea-N (30kg hm-2) once as a base (N2), N1+urea-N (30kg hm-2) topdressing at the tillering stage (N3), N1+urea-N (30kg hm-2) topdressing at the booting stage (N4) four N fertilizer management to study their impact on the yield, NUE and quality of mechanical direct-seeding rice. Compared with Yixiangyou 2115, Fyou 498 significantly increased photosynthetic potential, population growth rate, root vigor, and N transport rate by 3.34-23.88%. This increase further resulted in a significant improvement in the yield and NUE of urea-N topdressing by 1.73-5.95 kg kg-1. However, Fyou 498 showed a significant decrease in the head rice rate and taste value by 3.34-7.67%. All varieties were treated with N4 that significantly increase photosynthetic potential and population growth rate by 15.41-62.72%, reduce the decay rate of root vigor by 5.01-21.39%, promote the N transport amount in stem-sheaths (leaves) by 13.54-59.96%, and then significantly increase the yields by 4.45-20.98% and NUE of urea-N topdressing by 5.20-45.56 kg kg-1. Moreover, the rice processing and taste values were optimized using this model. Correlation analysis revealed to achieve synergistic enhancement of high-yield, high-quality, and high-NUE in rice, it is crucial to focus on increasing photosynthetic potential, population growth rate, and promoting leaf N transport. Specifically, increasing the contribution rate of N transport in stem-sheaths is the most important. These findings offer an effective N management strategy for 4R nutrient stewardship (right source, right method, right rate and right timing) of mechanical direct-seeding hybrid indica rice.

Blended controlled-release nitrogen fertilizer increases rice post-anthesis nitrogen accumulation, translocation and nitrogen-use efficiency.

One-time application of blended controlled-release nitrogen fertilizer (CRN) has the potential to solve the difficulty of top-dressing fertilizer in the cultivation of rice and reduce the cost of CRN fertilizer application. However, its effects on rice dry matter and nitrogen (N) accumulation and translocation, yield and N-use efficiency (NUE) remain uncertain. Field experiments were carried out at three sites (Mingguang, Chaohu, and Guichi) in the Yangtze River Delta in China to compare the effects of the conventional split applications of urea and the blended CRN and on post-anthesis dry matter and N accumulation and translocation, yield, and NUE in rice at 0, 60, 120, 180, and 240kg N ha-1. The results showed that at the equal N application rates, compared under the conventional N fertilizer treatment, the blended CRN application significantly increased the rice yield by an average of 0.9-6.9%, mainly due to increase the number of spikelets per panicle. The highest yield achieved with blended CRN treatment occurred at 200kg N ha-1, with an NUE of 45.9%. Moreover, in comparison to the conventional N fertilizer, the blended CRN treatment increased pre-anthesis N translocation (Pre-NT) by 1.0-19.8%, and the contribution of pre-NT to grain N by 0.2-8.7%, and NUE by 3.2-28.4%. Meanwhile, the blended CRN treatment reduced labor costs by 1800 Yuan ha-1 and enhanced the economic gains by 21.5-68.8%. Therefore, one-time application of blended CRN ≤ 200kg N ha-1 application rate improved rice yield, NUE, and economic profit compared to equivalent rates of split applied conventional N fertilizers.

Split application of polymer-coated urea combined with common urea improved nitrogen efficiency without sacrificing wheat yield and benefits while saving 20% nitrogen input.

Controlled-release nitrogen fertilizer (CRNF) has been expected to save labor input, reduce environmental pollution, and increase yield in crop production. However, the economic feasibility is still controversial due to its high cost. To clarify the suitable application strategy of CRNF in promoting the yield, nitrogen use efficiency and income on wheat grown in paddy soil, four equal N patterns were designed in 2017-2021 with polymer-coated urea (PCU) and common urea as material, including PCU applied once pre-sowing (M1), PCU applied 60% at pre-sowing and 40% at re-greening (M2), 30% PCU and 30% urea applied at pre-sowing, 20% PCU and 20% urea applied at re-greening (M3), and urea applied at four stage (CK, Basal:tillering:jointing:booting=50%:10%:20%:20%). In addition, M4-M6, which reduced N by 10%, 20% and 30% respectively based on M3, were designed in 2019-2021 to explore their potential for N-saving and efficiency-improving. The results showed that, compared with CK, M1 did not significantly reduce yield, but decreased the average N recovery efficiency (NRE) and benefits by 1.63% and 357.71 CNY ha-1 in the four years, respectively. M2 and M3 promoted tiller-earing, delayed the decrease of leaf area index (LAI) at milk-ripening stage, and increased dry matter accumulation post-anthesis, thereby jointly increasing spike number and grain weight of wheat, which significantly increased yield and NRE compared with CK in 2017-2021. Due to the savings in N fertilizer costs, M3 achieved the highest economic benefits. With the 20% N reduction, M5 increased NRE by 16.95% on average while decreasing yield and net benefit by only 6.39% and 7.40% respectively, compared with M3. Although NRE could continue to increase, but the yield and benefits rapidly decreased after N reduction exceeds 20%. These results demonstrate that twice-split application of PCU combined with urea is conducive to achieving a joint increase in yield, NRE, and benefits. More importantly, it can also significantly improve the NRE without losing yield and benefits while saving 20% N input.

Unveiling the potential of cellulose nanofibre based nitrogen fertilizer and its transformative effect on Vigna radiata (Mung Bean): nanofibre for sustainable agriculture.

Fertilizer management is crucial to maintaining a balance between environmental health, plant health, and total crop yield. Farmers are overutilizing fertilizers with a mind set to enhance the productive capacity of the field, which adversely impacts soil fertility and causes serious environmental hazards. To mitigate the issues of over-utilization of fertilizers, controlled-release fertilizers were developed using nitrogen fertilizer (ammonium chloride) loaded on cellulose nanofibres (named CNF*N). In this study, the effects of CNF*N were compared with commercial nitrogen fertilizer (ammonium chloride) on Vigna radiata (Mung) under greenhouse conditions. The pot experiment was conducted using six treatments: first treatment was control, where the plant was cultivated (T1); second treatment was T2, where the plant was cultivated with CNF to determine the impact of CNF on the plant; third was T3 where commercial ammonium chloride (24 mg/ 2 kg soil) was added to the plant; fourth was T4, where the plant was loaded with CNF, viz. CNF*N contains 4.8 mg of nitrogen; fifth was T5 CNF*N pellet contains 12 mg of nitrogen, and the last sixth treatment (T6) where CNF*N pellet containing 24 mg of nitrogen. It indicated that the growth parameters were best achieved in T6 treatment. Plant height was at its maximum in the T6 treatment (44.4 ±0.1cm) after the second harvest, whereas the minimum plant height was observed in T1, which was 39.1 ±0.1 cm. Root-to-shoot weight ratio was also maximum in T6 (0.183± 0.02) and minimum in T1 (0.07± 0.01) after second harvesting. The significant difference among the treatments was determined with Tukey's honestly significant difference (HSD). The nitrogen content (available and total) was significantly higher in the T4, T5, and T6 treatments (0.22, 0.25, and 0.28%) as compared to the control treatments (T1 (0.12%), T2 (0.13%), and T3 (0.14%) during the second harvesting stage (90 days), as nitrogen plays a crucial role in the development of vegetative growth in Vigna radiata. The rate of controlled-release nitrogen-fertilizer was found to be optimal in terms of plant growth and soil nutrients; hence, it could potentially play a crucial role in improving soil health and the yield of the crop.

Strip-Till Farming: Combining Controlled-Release Blended Fertilizer to Enhance Rainfed Maize Yield While Reducing Greenhouse Gas Emissions

The two major concerns of sustainable agriculture are safeguarding food security and reducing greenhouse gas emissions. Studies on the performance of strip-till with controlled-release blended fertilizer on rainfed maize grain yield, greenhouse gas emissions, and net ecosystem economic budget are scarce in the hilly region of northeast China. In this study, the differences between strip-till (RST) and conventional ridge cropping (CP), straw off-field no-tillage (NT), and no-tillage with straw mulching (RNT) were comparatively investigated in the conventional fertilizer (Sd) mode. And meanwhile, four fertilization modes were also set up under strip-till (RST): conventional fertilization (Sd), controlled-release nitrogen fertilizer blended with normal urea 3:7 (30%Cr), controlled-release nitrogen fertilizer blended with normal urea 5:5 (50%Cr), and no-nitrogen fertilization. We analyzed maize yield, greenhouse gas emissions (GHG), greenhouse gas intensity (GHGI), net income and net ecosystem economic budget (NEEB) for different treatments. The results showed that, under conventional fertilizer (Sd) mode, the maize yield of RST increased by 4.2%, 6.0% and 7.2% compared with NT, CP and RNT and the net income increased by 7.0%, 9.7% and 10.0%, respectively. Compared with CP and NT, although RST increased CO2 and N2O emissions, the GHGI of RST was not significantly different from CP and NT, and was 8.0% lower than that of RNT. The NEEB of RST increased by 6.8%, 9.7% and 11.0%, respectively, compared with NT, CP and RNT. Under strip-till, compared with 30%Cr and Sd, the yield of 50%Cr increased by 4.0% and 9.2% and the net income increased by 3.5% and 6.9%, respectively. There was no significant difference in GHGI between 50%Cr and 30%Cr, and 50%Cr decreased by 10.4% compared with Sd. The NEEB of 50%Cr increased by 3.8% and 7.4% compared to 30%Cr and Sd. Strip-till combines controlled-release nitrogen fertilizer blended with normal urea 5:5 (50%Cr) and can be applied as a sustainable strategy to improve the economic efficiency of maize and reduce environmental costs in the hilly region of northeast China.

Biochar-compost-based controlled-release nitrogen fertilizer intended for an active microbial community

Biochar-compost-based controlled-release nitrogen fertilizer intended for an active microbial community

The Long-Term Application of Controlled-Release Nitrogen Fertilizer Maintains a More Stable Bacterial Community and Nitrogen Cycling Functions Than Common Urea in Fluvo-Aquic Soil

Controlled-release nitrogen fertilizer (CRNF) has been proven to surpass common urea by mitigating nutrient losses, enhancing soil quality, and improving crop productivity. However, the long-term effects of CRNF on soil biological properties are not well understood. Here, a 12-year field experiment was conducted with five treatments: no N fertilizer (PK); the split application of urea at the farmer’s practice rate (FP) and the optimal rate (OPT); the one-time application of CRNF at the same rate as the OPT (CRNF); and a 20% reduced rate of the OPT (0.8CRNF). Soil samples were collected during the maize tasseling and filling stages; high-throughput sequencing and the PICRUSt2 method were employed to determine the bacterial community and its functional potential. The results showed that CRNF significantly increased alkaline hydrolysis N by 14.10% and 9.45% compared to OPT during the tasseling and filling stages, respectively. This increase in soil available N resulted in a significant increase in bacterial diversity of 2.09% and 2.35% compared with the FP and OPT, respectively. The bacterial community in the FP and OPT changed markedly between the tasseling and filling stages, with many bacterial species at the ASV and genus levels showing variations in relative abundance. In contrast, CRNF and 0.8CRNF exhibited stable N-cycling functions, as indicated by the lower variations in nitrate reductase and predicted N-cycling functional genes between the tasseling and filling stages. The obtained results suggest that CRNF application can enhance soil N supply, promote the formation of stable bacterial communities, and maintain stable N-cycling functions.

Substituting readily available nitrogen fertilizer with controlled-release nitrogen fertilizer improves crop yield and nitrogen uptake while mitigating environmental risks: A global meta-analysis

ContextControlled-release nitrogen fertilizer (CRN) is considered as an efficient tool for improving crop total uptake of N (TUN) and crop yield by providing better synchronization of crop N demand, but its effects on crop productivity, greenhouse gases (GHG) emissions and N loss are variable across agroecosystems. Objective and methodsHere, we conducted a meta-analysis by synthesizing 8874 observations from 240 published studies to address the effects of substituting CRN for readily available N fertilizer on crop yield, TUN, profit, GHG emissions, and N loss in rice, maize, wheat, soybean, and rape, with focus on cereals. ResultsOverall, CRN could increase crop productivity (crop yield, 5.1 %; profit, 8.2 %; TUN, 7.1 %) and reduce environmental pollution (GHG emissions, −3.6 % to − 18.6 %; N loss, −32.6 % to −49.1 %). These efficacies varied among crops but showed similar trends in general. The effect of CRN on crop yield was modulated by the N rate and the ratio of CRN. The optimal N rate and CRN ratio to obtain higher crop yields and profits also varied with crops. The CRN efficacies for decreasing GHG emissions and N loss depended on the mean growing season temperature, mean growing season precipitation, background soil total organic carbon content and pH values, the regions, and the CRN ratio and coating materials. A synergy of CRN with other crop management practices, such as mulching and efficient irrigation, was an effective strategy for increasing both crop productivity and environmental benefits. ConclusionsSubstituting readily available nitrogen fertilizer with CRN could produce more food and obtain higher profits with less environmental risk in crops, especially in cereals. ImplicationsThis study provides new insights into the effect of plant-soil-climate-management systems on crop productivity and environmental benefits for Sustainable Development Goals.

PH-responsive chitosan nanoparticles for controlled-release nitrogen fertilizer: Template-tampering free radical graft copolymerization under energetic radiation study

Macromolecular template-tampering free radical graft copolymerization under energetic radiation is studied as a controlled process for fabricating and nanosizing chitosan-graft-polyacrylic acid interpolymer complex (CS-PAA IPC) nanoparticles. The CS-PAA IPC nanoparticles is proposed as a pH-responsive vehicle for water absorption and controlled release of nitrogen (N) fertilizer. Roles of chitosan macromolecular template and absorbed energy for controlling free radical graft copolymerization in an aqueous solution were studied. Controlling graft copolymerization, nanostructure, nanosize, and size distribution of the CS-PAA IPC nanoparticles were followed by varying different parameters, i.e., CS template chain length, AA concentrations (0.03–0.15 M), and absorbed energies (10–30 kJ/kg, kGy). The CS-PAA IPC nanoparticles have well-defined in spherical shape with the size in the range of 30–200 nm. The pre-irradiated CS template provides a crucial role for narrowing size distribution of the CS-PAA IPC nanoparticles. Kinetic swelling behavior, water absorption/diffusion mechanism, nitrogen (N) fertilizer (ammonium nitrate, NH4NO3) entrapment/controlled release based on pH-responsive characteristic were investigated in acidic to basic ranges (pH 5, 7 and 9). The diffusion mechanism of the CS-PAA IPC nanoparticles exhibited a non-Fickian diffusion. The N content was 23 g per 100 g of CS-PAA IPC nanoparticles fertilizer. Pot-testing was carried out through the baby corn growth in different soil conditions, i.e., sandy soil (SS), SS/ NH4NO3, SS/NH4NO3-entrapped CS-PAA, and cultivation soil/NH4NO3. The CS-PAA IPC nanoparticles is a promising water absorption and pH-responsive platform for N fertilizer entrapment and controlled-release for soil amending, enhancing fertilizer utilization efficiency, and reducing environmental impact due to N loss.

Controlled-Release Nitrogen Mixed with Common Nitrogen Fertilizer Can Maintain High Yield of Rapeseed and Improve Nitrogen Utilization Efficiency.

Field experiments were conducted to study the effects of different proportions of controlled-release nitrogen fertilizer mixed with quick-acting nitrogen fertilizer on the yield and nitrogen utilization efficiency of direct-seeding rapeseed. Using a conventional nitrogen application rate of 180 kg ha-1 as a control, a total of 5 types of available nitrogen fertilizers and different proportions of controlled-release nitrogen fertilizers were mixed for fertilizer treatment. The proportion of available nitrogen fertilizer used was 135 kg ha-1, and the addition ratios of the five types of controlled-release nitrogen fertilizers were 0%, 30%, 50%, 70%, and 100%, respectively (i.e., the proportion of controlled-release nitrogen to the total nitrogen application amount). These ratios were represented as N135R0, N135R1, N135R2, N135R3, and N135R4, respectively. The results showed that there was no significant difference in the number of pods per plant, the number of seeds per pod, or the grain yield under the treatment of controlled-release nitrogen fertilizer mixed with quick-acting nitrogen fertilizer for proportions of 30-50% (N135R1~R3) when compared with the control, and a stable yield was achieved. Mixing controlled-release nitrogen fertilizer under reduced nitrogen application can significantly improve the apparent utilization rate of rapeseed nitrogen fertilizer, but it first increases and then decreases with the increase of the controlled-release nitrogen mixing ratio, reaching its highest under the N135R2 treatment. The agronomic utilization efficiency and partial productivity of nitrogen fertilizer first increased and then decreased with the increased proportion of controlled-release nitrogen, and both reached their highest utilization with the N135R2 treatment. The mixed treatment of controlled-release nitrogen did not affect soil urease activity, but significantly increased soil sucrase activity. The mixed treatment of controlled-release nitrogen also increased soil microbial biomass nitrogen and carbon content. Especially in the flowering stage, the soil microbial biomass nitrogen and carbon content was significantly higher under a controlled-release nitrogen mixing ratio of 30-50%. At the same time, it had a similar effect on soil inorganic nitrogen content. Therefore, a controlled-release nitrogen mixing treatment provided sufficient nitrogen for the key growth period of rapeseed. Under the condition of reducing the amount of nitrogen fertilizer by 25% based on the amount of nitrogen fertilizer applied to conventional rapeseed, the application of controlled-release urea mixed with common nitrogen fertilizer mixed at a ratio of 30-50% can be an effective way to maintain grain yield levels and improve nitrogen utilization efficiency.

Effectiveness of a 10-year continuous reduction of controlled-release nitrogen fertilizer on production, nitrogen loss and utilization of double-cropping rice

Considerable literature has demonstrated the advantage of controlled-release nitrogen (CRN) fertilizer in improving crop productivity. However, few researches have explored the long-term impacts of using CRN fertilizers as alternative to common urea on production and N utilization in double-cropping paddy. To address this gap, our study utilized a database derived from a 10-year field experiment from 2013 to 2022. During early and late rice seasons, compared to common urea (early rice, 150 kg hm−2; late rice, 180 kg hm−2), CRN fertilizer (150 kg hm−2; 180 kg hm−2) input significantly increased yield by 7.4 %, and 11.7 %, as well as N use efficiency (NUE) from 23.0 % and 24.6 % to 33.0 % and 37.5 %, respectively. CRN application significantly reduced N losses, evidenced by decrease in runoff (23.1 % and 19.4 %), leaching (12.7 % and 12.1 %), ammonia volatilization (28.9 % and 30.2 %), and N2O emissions (10.4 % and 16.1 %). A reduction of 10 % in CRN fertilizer input maintained yield. Compared with normal amount, reducing 10, 20, and 30 % CRN input increased NUE by 7.0–7.6 %, 7.3–7.4 %, and 11.6–12.6 %; reduced runoff loss by 16.1–17.9 %, 27.9–30.7 %, and 35.0–37.2 %; decreased leaching loss by 7.6–12.8 %, 18.1–22.6 %, and 26.5–31.4 %; decreased ammonia volatilization by 9.9–12.3 %, 16.3–22.7 %, and 23.2–29.3 %, and decreased N2O loss by 7.8–13.3 %, 12.8–32.8 %, and 20.3–36.9 %, respectively. Soils with CRN input showed higher total and inorganic N contents than the soils with common urea, and the content increased in parallel with CRN fertilizer input. Soil N content and N runoff loss were significantly related to yield and N uptake, and N runoff and leaching losses were significantly related to NUE. These results support the sustainable use of CRN fertilizers as a viable alternative to common urea, indicating that application rate of 135 and 162 kg N hm−2 of early and late rice, respectively, maintain yield and enhance N utilization in double-season paddy of southern China.

Soil Bacteriome Resilience and Reduced Nitrogen Toxicity in Tomato by Controlled Release Nitrogen Fertilizer Compared to Urea

Controlled release fertilizers (CRFs) mitigate negative effects of high nitrogen (N) fertilization rates, such as N toxicity and soil N loss. However, it is unknown if potentially toxic rates of CRF and quick release fertilizer differentially affect soil bacterial communities. To examine potential N toxicity effects on soil microbial communities, we grew tomato (Solanum lycopersicum “Rutgers”) for eight weeks in soils that were fertilized with high levels of quick release or controlled release urea and in soils with either low or high initial microbial N competitor populations. In both soils, we observed N toxicity in urea-fertilized tomatoes, but toxicity was ameliorated with CRF application. Controlled release fertilization increased soil N retention, thereby reducing soil N loss. While N toxicity symptoms manifested in the plant, the soil microbiome was only minorly affected. There were subtle differences in soil bacterial populations, in which nitrifying bacteria accumulated in soils fertilized at high N rates, regardless of the type of N fertilizer used. Ultimately, CRF reduced plant N toxicity symptoms but did not change the soil microbiome compared to quick release urea. These results show that while there are clear benefits of CRF regarding N toxicity tolerance on crops, the soil microbiome is resilient to this abiotic stressor.

Greenhouse Evaluation of Biochar-Based Controlled-Release Nitrogen Fertilizer in Corn Production

Greenhouse Evaluation of Biochar-Based Controlled-Release Nitrogen Fertilizer in Corn Production

Chitosan microspheres-based controlled-release nitrogen fertilizers improve the biological characteristics of Brassica rapa ssp. pekinensis and the soil

Present study investigates the impact of chitosan microspheres-based controlled-release nitrogen fertilizer (Cm-CRNFs) on biological characteristics of Brassica rapa ssp. pekinensis (Chinese cabbage) and soil. The study was carried out under various four treatments, urea (0.8033 g), blank chitosan microspheres (without urea), Cm-CRNFs (0.8033 g), and a control group (CK). The results indicated that Cm-CRNFs significantly prolonged the nitrogen release and enhanced the plant shoot length, shoot diameter, number of branches, pods, total amino acids, and vitamin C of Brassica rapa ssp. pekinensis as well as increased the soil nutrient availability. Chao index of bacterial diversity analysis showed a significant reduction of 15.89 % in Cm-CRNFs, but the Shannon index value in Cm-CRNFs was increased by 23.55 % compared to CK. Furthermore, Cm-CRNFs treatment significantly influenced genus richness level of Arthrobacter, Archangium, Bacillus, and Flavihumibacter. Moreover, relative abundance of bacteria significantly enhanced Cm-CRNFs, including Acidobacteriota, Acitinobacteriota, Cloroflexi, Cyanobacteria, and Patescibacteria. Soil enzyme activity such as: urease, acid phosphatase, and catalase enzymes in Cm-CRNFs and urea treatment significantly increased. Besides, other enzymes such as: cellulase and β-glucosidase activity decreased in the Cm-CRNFs treatment. It was concluded that Cm-CRNFs potentially prolonged discharge of micro/macronutrients and improved soil bacterial diversity, which ultimately enhanced the soil fertility and improved the soil enzyme activity.

Improving the yield and nitrogen use efficiency of hybrid rice through rational use of controlled-release nitrogen fertilizer and urea topdressing.

Controlled-release fertilizers effectively improve crop yield and nitrogen use efficiency (NUE). However, their use increases the cost of crop production. Optimal management modes involving urea replacement with controlled-release N fertilizers to increase rice yield through enhanced NUE are not widely explored. Field experiments were conducted from 2017 to 2018 to determine the effects of different controlled-release N fertilizers combined with urea [urea-N (180kg ha-1, N1)]. We used controlled-release N (150kg ha-1, N2) as the base, and four controlled-release N and urea-N ratio treatments [(80%:0% (N3), 60%:20% (N4), 40%:40% (N5), or 20%:60% (N6) as the base with 20% urea-N as topdressing at the panicle initiation stage under 150kg ha-1] to study their impact on the grain yield and NUE of machine-transplanted rice. Grain yield and NUE were positively correlated with increases in photosynthetic production, flag leaf net photosynthetic rate (Pn), root activity, N transport, and grain-filling characteristics. The photosynthetic potential and population growth rate from the jointing to the full-heading stage, highly effective leaf area index (LAI) rate and Pn at the full-heading stage, root activity at 15d after the full-heading stage, and N transport in the leaves from the full-heading to mature stage were significantly increased by the N4 treatment, thereby increasing both grain yield and NUE. Furthermore, compared with the other N treatments, the N4 treatment promoted the mean filling rate of inferior grains, which is closely related to increased filled grains per spikelet and filled grains rate. These effects ultimately improved the grain yield (5.03-25.75%), N agronomic efficiency (NAE, 3.96-17.58%), and N partial factor productivity (NPP, 3.98-27.13%) under the N4 treatment. Thus, the N4 treatment with controlled-release N (60%) and urea-N (20%) as a base and urea-N (20%) as topdressing at the panicle-initiation stage proved effective in improving the grain yield and NUE of machine-transplanted hybrid indica rice. These findings offer a theoretical and practical basis for enhancing rice grain yield, NUE, and saving the cost of fertilizer.

Assessment of the crucial factors influencing the responses of ammonia and nitrous oxide emissions to controlled release nitrogen fertilizer: A meta-analysis

Reducing ammonia (NH3) and nitrous oxide (N2O) emissions have great effects on mitigating nitrogen (N) nutrient loss and greenhouse gas emissions. Controlled release urea (CRU) can control the N release rate, which reduces reactive N loss and increases nitrogen use efficiency relative to conventional urea (CU). However, the crucial factors influencing the responses of NH3 and N2O emissions to CRU relative to CU are still unclear. In this study, we evaluated the responses of NH3 and N2O emissions to CRU based on collected field data with a meta-analysis. CRU reduced the NH3 and N2O emissions by 32.7 and 25.0% compared with CU, respectively. According to subgroup analysis, CRU presented better mitigation of NH3 and N2O emissions in soils with pH 6.5–7.5 (–47.9 and –23.7%) relative to either pH<6.5 (–28.5 and –21.4%) or pH>7.5 (–29.3 and –17.3%), and in the rice season (–34.8 and –29.1%) relative to the wheat season (–19.8 and –22.8%). The responses of NH3 and N2O emissions to CRU increased from rainfed (–30.5 and –17.0%) to irrigated (–32.5 and –22.9%), and then to paddy (–34.8 and –29.1%) systems. In addition, the response of N2O emission mitigation increased with increases in soil total nitrogen (TN); however, soil TN did not significantly affect the response of NH3 volatilization. The reduction in NH3 emission was greater in sandy-textured soil (–57.7%) relative to loam-textured (–32.9%) and clay-textured (–32.3%) soils, whereas soil texture did not affect N2O emission. Overall, CRU was a good option for reducing the NH3 and N2O emissions relative to CU in agricultural production. This analysis improves our understanding of the crucial environmental and management factors influencing the mitigation of NH3 and N2O emissions under CRU application, and these site-specific factors should be considered when applying CRU to reduce reactive N loss and increase NUE.

Straw returning combined with controlled-release nitrogen fertilizer affected organic carbon storage and crop yield by changing humic acid composition and aggregate distribution

Soil organic carbon (SOC) sequestration effectively reduces global CO2 emissions while ensuring crop production and sustainable agricultural development. Evaluating the effects of straw returning combined with controlled-release nitrogen (N) fertilizer on soil organic carbon (SOC) sequestration is necessary. We conducted a long-term (2013–2018) insitu field trial with six treatments: straw combined with no N and two N fertilizer types [no N fertilizer (CKS), conventional N fertilizer (BBFS) and controlled-release N fertilizer (CRFS)] and their corresponding no N and two N fertilizer treatments (CK, BBF, and CRF), each in three replicates. Overall, straw returning combined with N fertilizer (BBFS and CRFS) improves carbon storage and crop yield by changing aggregate distribution, with the effect of CRFS being more substantial. We further found CRFS treatment significantly increased SOC storage in small macro-aggregates (0.25–2 mm) by 9.2% and 28.4%, respectively, compared to BBFS and CKS treatments, which is mainly due to CRFS treatment increasing the proportion of small macro-aggregates (0.25–2 mm) by 8.1% and 20.1%, respectively, in contrast with BBFS and CKS treatments. Compared to BBFS and CKS treatments, CRFS treatment increased the fluorescence intensity of hydrophobic compounds in humic acid (HA) by 45.0% and 107.6%, respectively. Similarly, in small macro-aggregates (0.2–2.5 mm), CRFS treatment significantly increased the fluorescence intensity of hydrophobic compounds in HA. Lastly, structural equation modeling showed that straw returning treatments promote aggregate formation and carbon sequestration by increasing the fluorescence intensity of hydrophobic compounds in HA, ultimately increasing crop yield. Therefore, CRFS treatment is theoretically an effective method to promote SOC storage and increase crop yield and is a viable practice for sustainable agriculture.

The optimum economic nitrogen rate of blended controlled-release nitrogen fertilizer for rice in the Chanoyu watershed in the Yangtze River Delta, China.

The application of controlled-release nitrogen fertilizer (CRN) has become an important production method to achieve high crop yield and ecological safety. However, the rate of urea-blended CRN for rice is usually determined by conventional urea, and the actual rate is still unclear. A five-year field experiment was carried out in the Chaohu watershed in the Yangtze River Delta to study rice yield, N fertilizer utilization efficiency (NUE), ammonia (NH3) volatilization and economic benefit under the four urea-blended CRN treatments with a 4:3:3 ratio applied at one time (60, 120, 180, 240 kg/hm2, CRN60, CRN120, CRN180, CRN240), four conventional N fertilizer treatments (N60, N120, N180, N240) and a control without N fertilizer (N0). The results showed that the N released from the blended CRNs could well satisfy the N demand of rice growth. Similar to the conventional N fertilizer treatments, a quadratic equation was used to model the relationship between rice yield and N rate under the blended CRN treatments. The blended CRN treatments increased rice yield by 0.9-8.2% and NUE by 6.9-14.8%, respectively, compared with the conventional N fertilizer treatments at the same N application rate. The increase in NUE in response to applied blended CRN was related to the reduction in NH3 volatilization. Based on the quadratic equation, the five-year average NUE under the blended CRN treatment was 42.0% when rice yield reached the maximum, which was 28.9% higher than that under the conventional N fertilizer treatment. Among all treatments, CRN180 had the highest yield and net benefit in 2019. Considering the yield output, environmental loss, labor and fertilizer costs, the optimum economic N rate under the blended CRN treatment in the Chaohu watershed was 180-214 kg/hm2, compared with 212-278 kg/hm2 under the conventional N fertilizer treatment. The findings suggest that blended CRN improved rice yield, NUE and economic income while decreasing NH3 volatilization and negative environmental outcomes.

Effects of slow- and controlled-release nitrogen fertilizers on bacterial and fungal community composition in a double-cropping rice system

Slow- and controlled-release (SCR) nitrogen (N) fertilizers improve crop production and N utilization efficiency. However, responses of biological soil characteristics to the long-term application of N fertilizer have received little attention. In this work, a five-year field experiment was performed to assess the influence of different N fertilizer treatments (no N fertilizer application [CK] and applications of polymer-sulfur coated urea [PSCU], conventional prilled urea [PU], and urea-formaldehyde [UF]) on soil microbial communities in yellow clayey paddy soils in southern China. The types of N fertilizers had a stronger impact on soil bacterial diversity and community structure than fungal diversity and community structure. The soil microbial communities of PU and UF treatments did not differ from those of CK regarding alpha diversity indices. However, the PSCU treatment significantly decreased the Shannon index by 2.16% for bacteria but had no significant effect on the Shannon index of fungi. This might be due to the application of PSCU significantly reducing the soil pH by 0.16 units compared to CK and leading to soil acidification. Co-occurrence network analysis determined the keystone species mainly belonging to Proteobacteria and Ascomycota. Notably, these keystone species played an important role in PSCU-treated soils. Soil Ca2+, Na+, and NH4+ were the main determinants of microbial network stability. These results contribute to our understanding of how SCR-N fertilizers impact soil microorganisms.

Controlled-release nitrogen fertilizer application mitigated N losses and modified microbial community while improving wheat yield and N use efficiency

The extensive application of traditional fertilizer has greatly contributed to wheat yield, accompanied by massive nitrogen (N) loss and environmental pollution. Controlled-release nitrogen fertilizer (CRNF) is expected to improve N use efficiency (NUE) in agricultural systems. Unfortunately, the mechanism by which CRNF reduces N loss and its response to soil microbial communities remains unclear. In this study, common urea, polymer-coated urea (PCU), sulfur-coated urea (SCU) and urea-formaldehyde (UF) were used as materials to analyze the effects of split application of different N sources on wheat yield, NUE, soil N balance, soil bacterial diversity and functional abundance. The results showed that PCU and SCU significantly improved yield relative to urea, with an average increase of 18.20% and 15.73%, respectively. N uptake by wheat in PCU, SCU and UF was increased by 18.76%, 14.26% and 7.75% compared to that in urea, respectively. CRNF increased the mineral N content of the topsoil (0−20 cm) but decreased the mineral content in the deeper soil (40−60 cm). CRNF was observed to significantly decrease cumulative N2O emissions, as well as apparent N loss compared with urea, which was reduced by 39.45%, 30.74% and 11.68% in PCU, SCU and UF, respectively. In addition, PCU decreased soil bacterial diversity but increased the abundance of microbes involved in N cycle, such as Firmicutes, Actinobacteriota and Bacteroidota, which could regulate soil nitrate concentrations. The results indicated that split application of PCU was conducive to promoting N uptake by wheat, increasing topsoil mineral N content, reducing N leaching into deeper soil and N2O emissions, thereby alleviating N loss while increasing NUE and wheat yield.