Urea Application Research Articles

Digestate induces significantly higher N2O emission compared to urea under different soil properties and moisture

Digestate is considered as an option for recycling resources and a part of the substitution for chemical fertilizers to reduce environmental impacts. However, its application may lead to significant nitrous oxide (N2O) emissions because of its high concentration of ammonium and degradable carbon. The research objectives are to evaluate how N2O emissions respond to digestate as compared to urea application and whether this depends on soil properties and moisture. Either digestate or urea (100 mg N kg−1) was applied with and without a nitrification inhibitor of 3,4-dimethylpyrazole phosphate (DMPP) to three soil types (fluvo-aquic soil, black soil, and latosol) under three different soil moisture conditions (45, 65, and 85% water-filled pore space (WFPS)) through microcosm incubations. Results showed that digestate- and urea-induced N2O emissions increased exponentially with soil moisture in the three studied soils, and the magnitude of the increase was much greater in the alkaline fluvo-aquic soil, coinciding with high net nitrification rate and transient nitrite accumulation. Compared with urea-amended soils, digestate led to significantly higher peaks in N2O and carbon dioxide (CO2) emissions, which might be due to stimulated rapid oxygen consumption and mineralized N supply. Digestate-induced N2O emissions were all more than one time higher than those induced by urea at the three moisture levels in the three studied soils, except at 85% WFPS in the fluvo-aquic soil. DMPP was more effective at mitigating N2O emissions (inhibitory efficacy: 73%–99%) in wetter digestate-fertilized soils. Overall, our study shows the contrasting effect of digestate to urea on N2O emissions under different soil properties and moisture levels. This is of particular value for determining the optimum of applying digestate under varying soil moisture conditions to minimize stimulated N2O emissions in specific soil properties.

Mineral Nitrogen Release Patterns in Various Soil and Texture Types and the Impact of Urea and Coated Urea Potassium Humate on Barley Biomass

Controlled-release urea fertilization is an innovative approach and effective means to reduce the loss of nitrogen and enhance fertilizer use efficiency to optimize crop yield while minimizing the environmental impact. The objective of this study was to investigate the dynamic process of mineral nitrogen (Nmin) release in Luvisols, Cambisols, Retisols, and Arenosols to understand the interaction between soil characteristics and mineral nitrogen release and evaluate the impact of conventional urea compared to coated urea potassium humate on barley biomass production. A pot experiment was conducted under glasshouse conditions (20 ± 2 °C and 60% Humidity). Five treatments including no fertilization as a control (C), 100 kg·N·ha−1 of urea (U100), 200 kg·N·ha−1 of urea (U200), 100 kg·N·ha−1 of coated urea potassium humate (UPH100), and 200 kg·N·ha−1 of coated urea potassium humate (UPH200) were applied to four soil and texture types. Our findings indicate that there are different patterns of mineral nitrogen release across the different soil and texture types. Ammonium levels reached their peak point in all soils within 2–7 days after application. On the other hand, the concentration of nitrate NO3−–N showed a linear increase over 45 days during the experiment. The Retisol, which had a sandy clay texture, obtained the highest concentration of mineral nitrogen in both forms (NH4 and NO3), while the sandy texture of Arenosol showed the lowest accumulation of mineral nitrogen and its forms. The application of potassium humate caused a delay of 1–4 days in the peak of soil ammonium, which at peak accounted for approximately 25–44% of the mineral nitrogen in the soil. Furthermore, the application of urea and coated urea potassium humate exhibited significant effects on barley biomass with an increase of approximately 14–91% compared to the unfertilized treatment (control). This research contributes to our understanding of nutrient dynamics in diverse soil environments and provides insights into optimizing sustainable fertilization strategies such as controlled-release fertilizer application. The implications of these findings highlight the significance of tailored nutrient management practices based on soil texture type, which can lead to improved agricultural productivity and environmental impact.

Stabilized urea for maize grown on an Amazonian Cerrado soil

AbstractUrea splitting and the use of stabilized ureas in corn (Zea mays L.) crops are management strategies that increase urea efficiency and reduce nitrogen (N) losses by volatilization and leaching. This study aimed to evaluate the effects of urea stabilized with urease inhibitor (UI) and nitrification inhibitor (NI) compared to conventional urea applied at three different schedules, on corn grain yield and the dynamics of inorganic nitrogen on an Amazonian Cerrado soil, Brazil. Two experiments were carried out, one in 2019 and the other one in 2021, in a randomized block design with four replications. Treatments were arranged in a factorial scheme (3 × 3), with three types of urea (urea, U; UI; and NI) and three application schedules (100% at planting, 30% at planting and 70% as topdressing, and 30% at planting and two topdressings with 35% N). In 2019, compared to U and UI, NI increased corn yield when 100% of urea was applied at planting. Regardless of the splitting management, NI ensured the same yields. In 2021, urea splitting was required to improve corn yields, and UI promoted higher yield in all urea application schedule. In 2019 and 2021, both NI and UI, respectively, ensured higher inorganic N levels in the soil, especially after the first topdressing. These N contents are reflected in yield gains. Urea with nitrification or urease inhibitor may be a relevant option for managing nitrogen fertilization in corn crops in the Amazonian Cerrado.

Consequences of excess urea application on photosynthetic characteristics and nitrogen metabolism of Robinia pseudoacacia seedlings

Urea is the most frequently used nitrogen (N) fertilizer worldwide. However, the mechanisms in plants to cope with excess urea are largely unknown, especially for woody legumes that can meet their N demand by their own N2-fixation capacity. Here, we studied the immediate consequences of different amounts of urea application and exposure duration on photosynthesis, N metabolism, and the activity of antioxidative enzymes of Robinia pseudoacacia seedlings. For this purpose, seedlings were grown for 3 months under normal N availability with rhizobia inoculation and, subsequently, 50 mg N kg−1 was applied to the soil twice with urea as additional N source. Our results show that excess urea application significantly promoted photosynthesis, which increased by 80.3% and 84.7% compared with CK after the 1st and 2nd urea applications, respectively. The increase in photosynthesis translated into an increase in root and nodule biomass of 88.7% and 82.0%, respectively, while leaf biomass decreased by 4.8% after the first application of urea. The N content in leaves was 92.6% higher than in roots, but excess urea application increased the N content of protein and free amino acids in roots by 25.0%, and 43.3%, respectively. Apparently, enhanced root growth and N storage in the roots constitute mechanisms to prevent the negative consequences of excess N in the shoot upon urea application. Nitrate reductase (NR) activity of leaves and roots increased by 74.4% and 26.3%, respectively. Glutathione reductase (GR) activity in leaves and roots was enhanced by 337% and 34.0%, respectively, but then decreased rapidly to the initial level before fertilization. This result shows that not only N metabolism, but also antioxidative capacity was transiently promoted by excess urea application. Apparently, excess urea application initially poses oxidative stress to the plants that is immediately counteracted by enhanced scavenging of reactive oxygen species via enhanced GR activity.

Effects of corn stalks returning on soil microbial carbon use efficiency and corn yield in semi-arid cropland

Soil microbial carbon use efficiency (CUE) is a key parameter controlling the short-term carbon (C) cycle in terrestrial ecosystems. The effect of urea application (156 kg N ha-1) and corn stalks returning (9.0 tons ha-1) on soil microbial CUE and corn yield in semi-arid cropland was studied using the 18O-labeled water approach during a one-year experiment. In semi-arid cropland, applying urea reduced soil microbial CUE by 44%, while the soil microbial CUE was increased significantly by 34% after returning corn stalks to the field. The application of urea increased the total nitrogen content of soil by 23%, and corn stalks returning further increased nitrate nitrogen (NO3–-N) by 45%, dissolved organic carbon (DOC) by 53%, and dissolved organic nitrogen (DON) by 122%. Compared with no fertilization, urea application increased the corn height by 4% and the corn yield by 21%. Corn stalks returning combined with urea reduced the corn stalks by 37% compared with no fertilizer. There was no significant difference in corn yield between corn stalks returning combined with urea and single urea application. Therefore, corn stalks returning combined with urea may be an effective agronomic measure to increase soil carbon sequestration, improve soil fertility, maintain corn yield, restore soil fertility, and improve production capacity.

Combined zinc and urea application enhances productivity and profitability of lentil (Lens culinaris Medik.)

The present study investigated the effect of sole as well as combined foliar application of zinc (Zn) and urea at flowering and pod formation stages and soil application of Zn on symbiotic parameters, growth, yield, and economics of lentil. Field experiments were conducted at two locations (Ludhiana and Faridkot, northern India) during the winter season of 2018–19 and 2019–20 in randomized complete block design. The experiment comprised of 11 treatments [control (no soil/foliar application of ZnSO4 and no urea foliar application), soil Zn (25 kg ZnSO4 ha−1), foliar application of sole Zn (0.5% ZnSO4) or urea (2%) and combined Zn + urea at flowering, pod formation, or flowering + pod formation stages] and three replications. Zn and urea fertilization significantly improved the grain yield and related traits and economics in both the years of study at both the locations. The treatment of combined foliar application of Zn + urea at flowering + pod formation stages recorded the highest symbiotic parameters, chlorophyll content, growth and yield attributes, grain yield (29.5% higher than control), gross returns (29.5% higher), net economic returns (56.2% higher), and benefit cost ratio. The combined foliar application of Zn + urea can be done to improve growth, productivity, and economics of lentil and, therefore, it can help in upliftment of economic status of farmers.

The use of urea hydrogen peroxide as an alternative N-fertilizer to reduce accumulation of arsenic in rice grains

A greenhouse experiment was conducted to examine the effects of urea hydrogen peroxide (UHP) on reducing the accumulation of As in rice grains. The results show that UHP effectively triggered Fenton-like reaction by reacting with Fe2+ in the paddy soils. This significantly inhibited the activities of As(V)-reducing microbes, causing impediment of As(V)–As(III) conversion following inundation of dryland crop soils for paddy rice cultivation. As-methylating microbes were also inhibited, adversely affecting As methylation in the soils. These processes led to the reduction in phyto-availability of As in the soil solutions for uptake by rice plant roots, and consequently reduced the accumulation of As in the rice grains. In this study, an UHP application rate of 0.0625% on three occasions (tillering, heading and filling) during the rice growth period was sufficient to lower the rice grain-borne As concentration to below 0.2 mg/kg, meeting the quality standard set by the Chinese government. No additive effect on reducing grain-borne As was observed for the joint application of UHP and biochar or biochar composite. The use of UHP for soil fertilization had no adverse impact on rice yield in comparison with the application of urea at an equal amount of nitrogen.

Combination of seed priming and nutrient foliar application improved physiological attributes, grain yield, and biofortification of rainfed wheat.

Seed priming and foliar application are two crop management practices that can increase grain yield and quality. The research aimed to assess the influence of seed priming and foliar application on rainfed wheat. Two field experiments with two seed priming rates (control and priming) and five foliar applications [control, urea (4%), silicon (4 mM), FeSO4.7H2O (0.6%), and ZnSO4.7H2O (0.4%)] at the anthesis/Z61 stage were conducted. Seeds were primed for 12h at 25 ± 2°C, by soaking in an aerating solution [urea (20g L-1) + FeSO4.7H2O (50 ppm) + ZnSO4.7H2O (50 ppm) + silicon (20 mg L-1)]. Seed weight-to-solution volume ratio was 1:5 (kg L-1). A pot experiment was also conducted to examine the effect of priming on root growth. Overall, combined seed priming and foliar application induced a positive impact on physiological traits and attributes. Maximum chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid concentrations (1.58, 0.669, 2.24, and 0.61 mg g-1 FW), membrane stability index (77.31%), superoxide dismutase and peroxidase activity (0.174 and 0.375 Unit mg-1 protein), 1,000-grain weight (35.30g), biological yield, grain yield (8,061 and 2,456 kg ha-1), and minimum malondialdehyde concentration (3.91 µg g-1 FW) were observed in seed priming combination with ZnSO4 foliar application. The highest glycine betaine concentration (6.90 mg g-1 DW) and proline (972.8 µg g-1 FW) were recorded with the co-application of seed priming and foliar urea spraying. Foliar application of ZnSO4, FeSO4, and urea drastically enhanced grain Zn (29.17%), Fe (19.51%), and protein content (increased from 11.14% in control to 12.46% in urea foliar application), respectively. Compared to control, seed priming increased root length, root volume, and dry mass root by 8.95%, 4.31%, and 9.64%, respectively. It is concluded that adequate Zn, Fe, silicon, and N supply through seed priming and foliar applications of these compounds at the terminal stage of rainfed wheat alleviates drought stress and improves GY and biofortification.

Response of Onion (Allium cepa L.) to Foliar Application of Nano Urea and Urea

A field study was conducted during Rabi season 2022at the Horticultural Research Farm, Mangalayatan University, Jabalpur to study the effect of foliar application of nano urea and urea on growth and yield of onion. The experiment was laid out in RBD with three replications and consisted of 9 treatments viz., T1-100% RDF (100:50:50 kg NPK ha1), T2-75:50:50 kg NPK ha-1 + foliar spray of 0.4% nano urea on 30 and 60 DAT, T350:50:50 kg NPK ha-1 + foliar spray of 0.4% nano urea on 30 and 60 DAT, T4-75:50:50 kg NPK ha-1 + foliar spray of 0.4% nano urea on 30 DAT, T5-50:50:50 kg NPK ha-1 + foliar spray of 0.4% nano urea on 30 DAT, T6-75:50:50 kg NPK ha-1 + foliar spray of 0.5% urea on 30 and 60 DAT, T7-50:50:50 kg NPK ha-1 + foliar spray of 0.5% urea on 30 and 60 DAT, T8-75:50:50 kg NPK ha-1 + foliar spray of 1% urea on 30 and 60 DAT, and T9-50:50:50 kg NPK ha-1 + foliar spray of 1% urea on 30 and 60 DAT. Each treatment showed their significant effects on the recorded growth and yield parameters. Among all the treatments, treatment T2 with 25% reduced nitrogen application plus foliar spray of 0.4% nano urea on 30 and 60 DAT recorded maximum plant height on 90 DAT (57.82 cm),number of leaves (9.13), equatorial diameter (5.51 cm), polar diameter (5.17), average bulb weight (69.56 g), bulb yield (336.40 kg) than other treatments.

Enhanced-efficiency nitrogen fertilizer provides a reliable option for mitigating global warming potential in agroecosystems worldwide

Enhanced-efficiency nitrogen fertilizer (EENF), developed to improve synchronization between crop nitrogen demand and nitrogen supply, can guarantee global food security and mitigate nitrogen fertilizer-induced environmental consequences. However, comprehensive assessments of how EENF affects CH4 and CO2 emissions from paddies and drylands and the associated benefits are lacking. Here, we present the results of a global meta-analysis conducted to assess the above issues. Our results showed that, on average, applying nitrification inhibitors and coated controlled-release urea to paddy fields significantly decreased CH4 emissions by 24.0 % and 25.3 %, respectively, likely due to the weakened inhibition of NH4+ on CH4 oxidation. A similar effect on CO2 emission was observed when farmers used nitrification inhibitors and coated controlled-release urea in the drylands. The meta-analysis results revealed that all EENF products could help mitigate the global warming potential of paddies and drylands. After incorporating the benefit of global warming potential mitigation into the cost-benefit analysis, coated controlled-release urea application in paddies and drylands produced the largest environmental gains of $ 76.34 ha−1 and $ 79.35 ha−1, respectively. However, the relatively lower purchasing cost and larger yield increase of urease inhibitors resulted in the largest net profits for farmers. Moreover, a greater economic return was generally achieved by applying EENF to paddy fields than by applying EENF to drylands. These findings highlight the role of EENF in mitigating the global warming potential of global paddy and dryland fields, which has facilitated the comprehensive recognition of EENF-induced impacts.

Study on the effectiveness and mechanism of a sustainable dual slow-release model to improve N utilization efficiency and reduce N pollution in black soil

Long-term intensive cultivation has led to serious N loss and low N fertilizer utilization efficiency (NUE) in black soil areas. The lost N is not only a waste of resources but also a serious pollution threat to the environment, leading to the decline in water quality and food safety and the greenhouse effect. In the present study, a stable dual slow-release model, CPCS-Urea, was prepared by in situ polymerization using nitrapyrin, urea and melamine-formaldehyde resin as raw materials. The effect of the dual slow-release model was systematically evaluated using two consecutive years of field experiments. Five treatments were established in the field experiment: no N fertilizer (N0), urea (N180), 1 % CPEC-Urea, 0.5 % CPCS-Urea, and 1 % CPCS-Urea. The results showed that the new dual slow-release CPCS-Urea model outperformed both the use of urea and the traditional slow-release CPEC-Urea model in reducing N losses and improving NUE. The application of CPCS-Urea reduced nitrate (NO3−) leaching by 28.2 %–47.2 % and N2O emissions by 36.5 %–42.4 % and increased NUE by 20.7 %–28.5 % compared to urea application. The CPCS-Urea model modulated the activity of ammonia-oxidizing bacteria (AOB) and dissimilatory nitrate reduction to ammonium (DNRA) bacteria in soil, showing a significant decrease in AOB activity and an increase in DNRA activity. This results in a lower soil NO3−-N yield and a 53.1 %–72.0 % increase in NH4+-N content, providing sufficient N for the entire growth and development cycle of maize. In short, the dual slow-release CPCS-Urea model has great application prospects for promoting agricultural development in black soil areas.

Mixed application of controlled-release urea and normal urea can improve crop productivity and reduce the carbon footprint under straw return in winter wheat-summer maize cropping system

An important goal of sustainable agriculture is reducing the environmental risk while also ensuring food security. The mixed application of controlled-release urea and normal urea (CRUNU) is a potential nitrogen (N) management strategy for achieving this goal. However, few studies have focused on whether optimizing the N application rate of CRUNU can balance crop yield and greenhouse gas emissions, especially when straw is returned. Thus, we conducted a five-year field experiment in a winter wheat–summer maize planting system in Northwest China to determine the effects of different N fertilizer types (NU: normal urea; CRUNU) and N application levels (low N, 135 kg ha–1; medium N, 180 kg ha–1; high N, 225 kg ha–1) with straw return on the crop yield and stability, N fertilizer partial factor productivity (NFPF), and soil organic carbon (SOC). Life cycle assessment was also conducted to quantify the GHG emissions from farmland and carbon footprint (CF). Compared with NU, CRUNU improved the winter wheat and summer maize grain yield, biomass, and NFPF at all three N application levels. The crop grain yields increased significantly as the N application level increased under NU, but the crop grain yields did not differ significantly between the medium and high N application levels under CRUNU (P > 0.05). The SOC contents increased as the duration of straw return increased. Compared with NU, CRUNU significantly increased the SOC content, and correlation analysis showed that this increase was related to the increased amount of returned straw. Compared with NU, CRUNU increased the GHG emissions in the production process but reduced the GHG emissions in the application process, as well as increasing soil CO2 fixation to ultimately reduce the total GHG emissions. CRUNU increased the crop grain yield while also reducing the total GHG emissions, and thus the CF decreased significantly by 14.53–23.03% compared with NU, especially at the medium N application level. Therefore, this comprehensive analysis of the crop productivity and GHG emissions indicates that CRUNU combined with an appropriate N application level can be used as a nitrogen fertilizer management strategy for sustainable winter wheat–summer maize cropping in Northwest China.

Effect of Incorporation Techniques and Soil Properties on NH3 and N2O Emissions after Urea Application

Ammonia (NH3) emissions affect the environment, the climate, and human health and originate mainly from agricultural sources like urea fertilizers. Such losses from urea fertilizer can be avoided by different application techniques like incorporation. However, the knowledge of the effect of these techniques on NH3 emissions is very limited and ambiguous since incorporation can also promote nitrous oxide (N2O) emissions. Three different principles of fertilizer incorporation methods were compared in three different soils (sandy, loamy, and clayey) at two moisture levels of 70% and 30% water-holding capacity (WHC), shallow mixing at 2 cm, injection with the slit technique at 5 cm, and deep complete incorporation at 5 cm simulating plow incorporation. The laboratory study was conducted with open dynamic incubation chambers where NH3 emissions were monitored with washing bottles while N2O emissions were studied with gas chromatographic (GC) measurements. The highest cumulative NH3 emissions occurred at low soil moisture levels in sandy soil (34% of the N applied). A maximum reduction in emissions by 87% was achieved with slit injection and 82% with deep injection compared to standard surface application. The reduction effect was positively related to increasing clay content. N2O emissions were delayed and highest from sandy soil. Overall, all urea incorporation techniques showed great potential for mitigating NH3 emissions on the clayey soil; for sandy and drier soils, only deeper or closed slot injection were consistently effective. However, connected to the surface incorporation at the higher moisture level, a relevant increase in N2O emissions compared to surface application was observed. Therefore, an increase in N2O emissions by urea incorporation may rule out specific incorporation techniques for NH3 emissions reduction from field-applied urea. In agricultural practice, a lower reduction in NH3 by fertilizer incorporation can be assumed in sandy soils or under dry soil conditions, as well as a more challenging technical implementation.

Glauconitic Siltstone: additive for ammonia retention and reduction of nitrogen volatilization loss

Glauconitic siltstone is sedimentary rock used as raw material to produce a multinutrient fertilizer that can combine with urea to increase their agronomic efficiency. The purpose of this study was to evaluate glauconitic siltstone as additive to reduce nitrogen losses by ammonia volatilization in nitrogen fertilizers. The experiment used randomized block, in a portion subdivided over time, following a 6 x 8 factorial with four replications and treatments comprising glauconitic siltstone mixture at a dose of 100 kg N ha-1 (control, without the application of nitrogen; conventional urea – 45% N; commercial fertilizer registered with the trade name of Super N®; urea with addition of glauconitic siltstone: 9% N; 20 and 31% N) and the remaining portion divided in the collection time at 3, 6, 9, 12, 15, 18, 24 and 30 days after fertilizer application. The collection of the volatilized ammonia was made in a semi-opened free static chamber. The use of glauconitic siltstone associated with urea provided a reduction in loss by volatilization from 10 to 27% in relation to conventional urea. The treatments with application of urea with the urease inhibitor showed the lowest volatilization rate and delay in the volatilization peak, which occurred 17 days after fertilizer application. In addition to providing nutrients to the plants, glauconitic siltstone reduces ammonia losses.

Combined application of Pseudomonas fluorescens and urea can mitigate rapid acidification of cropland Ultisol

Rhizobacteria maintain a healthy soil required for crop growth. This has led to increased interest in the use of bacteria-based biofertilizers in agriculture as they improve soil nutrient content and protect plants against pathogens. However, the effect of bacteria inoculum on N transformation and soil physicochemical properties during urea fertilization remains unexploited. Thus, this study investigated the effect of Pseudomonas fluorescens on urea N transformation in an acidic Ultisol within a 70-d incubation period. The results revealed that (1) soil pH peaked on d 5 (pH 5.58) and 20 (pH 6.23) and rapidly decreased till d 62 (pH 4.10) and 50 (pH 4.93) for urea and urea + bacteria treatments, respectively, and remained constant thereafter. After 70 d, the pH of the bacteria-treated Ultisol remained higher (0.78 pH units) than that of urea-treated Ultisol; (2) the change in soil pH was in agreement with the mineralization trend of N, as the concentration of NH4+-N peaked on d 5 (134.2 mg N kg−1) and 20 (423 mg N kg−1) before decreasing to 62.1 and 276.1 mg N kg−1 on d 70 in urea-treated and bacteria-treated Ultisol, respectively; and (3) P. fluorescens consumed protons produced during nitrification to retard rapid decrease in soil pH, decreased soil exchangeable acidity (33.3 %), increased soil effective cation exchange capacity (32.8 %), and increased the solubility of soil exchangeable base cations (68.4 %, Ca2+ + Mg2+ + K+ + Na+). Thus, bacterial inoculum could promote N mineralization, enhance nutrient solubility, and retard soil acidification during N transformation in soils.

Growth and yield of shallot (<em>Allium ascalonicum</em> L.) as influenced by soil application of liquid urea and cow urine

This experiment was carried to evaluate the effect of liquid urea and cow urine with cow dung on the economic yield of shallot (Allium ascalonicum L.) in the Eastern Province of Sri Lanka. The experiment was arranged in a Completely Randomized Design (CRD) with eight replicates and six treatments namely, T1: 20 g cow dung, T2: 20 g cow dung + 3% urea, T3: 20 g cow dung + 3% cow urine, T4: 30 g cow dung, T5: 30 g cow dung + 3% urea, and T6: 30 g cow dung + 3% cow urine. The soil applications of liquid urea and cow urine were done as top dressing at two weeks interval from 3rd week after planting (WAP). Data were collected at 3rd, 5th, 7th, and 9th WAP and at harvesting stage. The results revealed that there were significant (P<0.001) variations in plant height, number of bulbs, bulb diameter, fresh weight of single bulb, number of roots, root length, dry weight of leaves, dry weight of bulbs per plant and bulb yield per unit land among the treatments. Relatively higher yield (37.5 t/ha) was obtained from the plants treated with 30 g cow dung and 3% urea (T5) than other treatments whereas 20 g cow dung alone (T1) produced the lowest yield (8.4 t/ha). T6 (30 g cow dung and 3% cow urine) gave 32.6 t/ha bulb yield. It was also noted that there was no remarkable (P>0.05) difference in the bulb yields between T2 and T3. However, significant variation was observed between T5 and T6. The combined effect of cow dung and liquid urea fertilizer increased the onion yield. From this study, it could be stated that 30 g cow dung with 3% urea or 3% cow urine could give high bulb yield in the shallot cultivation at rural areas in Sri Lanka where farmers could easily collect the locally available materials for crop production in ecofriendly manner.

Optimization of controlled-release urea application based on the winter wheat yield

Wheat is of great significance to ensuring national food security in China. The one-time fertilization for saving labor was common in winter wheat production in the North China Plain, which caused the excessive application of nitrogen (N) fertilizer generally. Controlled-release urea (CRU) has a good application effect in crops with short growth periods such as rice and maize. However, the applications of CRU on winter wheat with a longer growth period are fewer. To investigate the appropriate dosage and blending proportion of CRU and urea in wheat production, the field experiment with 52 treatments was conducted in 2019–2021. This relationship among N application rates, CRU release longevity, CRU proportions and winter wheat yield was systematically studied, and the binary quadratic effect models between yield and CRU factors were established. N application rates, CRU proportion and the interacted effect of CRU proportion and release longevity had the greatest effect on winter wheat yield by the main effects test and correlation analysis. The winter wheat yield could be accurately predicted by CRU proportions and CRU release longevity. The prediction errors of yield models were −9.8%∼4.9% based on the 2018 and 2022 two years winter wheat yield with CRUs application. Reducing N application rates by 20∼30% and mixing with appropriate CRU proportion would increase the yield and NUEs (nitrogen use efficiencies) of winter wheat. In the case of low CRU proportion, the wheat yield could be increased by applying the CRU with long-release longevity; when the CRU proportion was high, the yield increase effect of the CRU with short-release longevity was better. Comprehensive field production survey and Response surface methodology (RSM) partial derivative analysis, CRUs with controlled release longevity of 57d∼150d and CRU proportion of 24∼64% were the best choices for increasing wheat yield and reducing N application rates. It will facilitate the optimization of wheat CRU manufacture and application and promote the ‘Reduction and Efficiency of Chemical Fertilizers’ policies and environmental protection.

Comparative Efficacy of Foliar Plus Soil Application of Urea versus Conventional Application Methods for Enhanced Growth, Yield, Agronomic Efficiency, and Economic Benefits in Rice.

The experiment was conducted at the research field, Department of Agronomy, Hajee Mohammad Danesh Science and Technology University, Dinajpur from December 2017 to May 2018 to find out the best treatment of foliar application of urea on the growth and yield of boro rice cv. BRRI dhan28. The experiment consisted of 10 treatments, laid out in a randomized complete block design in triplicate. The recommended doses (RD) of urea, TSP, MOP, gypsum, ZnSO4, and borax were applied during land preparation except for urea at 250, 75, 100, 75, 7, and 5 kg ha-1, respectively, where urea was applied as per treatment specification. The results revealed that the application of N fertilizer as foliage along with soil significantly influenced the growth, plant characteristics, and yield of BRRI dhan28. There was no significant difference between T8 (70% in soil and 10% as foliage) and T9 (100% in soil) treatment regarding the maximum panicle length (21.43 and 20.71 cm), fertile grains (117.40 and 113.30), total grains (134.40 and 130.97), 1000-grain weight (24.56 and 23.56 g), grain yield (5.91 and 5.74 t ha-1), straw yield (7.83 and 7.92 t ha-1), biological yield (13.74 and 13.66 t ha-1), and harvest index (43.01 and 42.02%), respectively, in this study. These results indicated that N fertilization as direct soil application (70%) and as foliage application (10%), i.e., 80% N fertilization, produced the highest grain yield and major yield traits which we received by 100% N fertilization as soil that was practiced traditionally by the farmers. The effect of overfertilization (T10) was not positive, producing the highest number of noneffective tillers and sterile grains (nonfilled grains). Therefore, it is possible to achieve an equivalent or more yield by saving 20% urea by the combination of soil (70%) and foliage (10%) application as compared to the traditional method of fertilizer application (100% in soil).

Effect of Iron and Urea Application on Iron Biofortification of Lentil (Lens culinaris Medik.)

ABSTRACT Agronomic biofortification with iron (Fe) may be a viable approach to combat the widespread deficiency of Fe in humans. Thus, the present study was conducted to examine the effect of Fe and urea foliar application on Fe biofortification in lentil (Lens culinaris Medik.). The field experiments were conducted at two locations viz. Ludhiana and Faridkot, India. Different treatment combinations of foliar spray of sole Fe (0.5% of FeSO4.7 H2O), sole urea (2% urea), and combined application of Fe and urea at flowering, pod formation, and flowering + pod formation stages along with unsprayed control were applied to lentil. The results of the study revealed that the combined foliar application of Fe and urea at flowering + pod formation stages was the most effective in enhancing grain yield, Fe and zinc (Zn) concentration in plants (at flowering as well as pod formation stage), stover and grain (whole and split). The highest Fe concentration in whole (36% higher over control) as well as split (32.9% higher over control) grain and protein content (21% higher over control) was obtained with foliar application of Fe + urea at flowering + pod formation stages. Conclusively, the combined foliar application of 0.5% FeSO4.7 H2O and 2% urea at flowering + pod formation stages may prove to be a feasible option for increasing grain yield and enrichment of lentils with Fe and Zn to combat micronutrient malnutrition in human populations.

The effect of long-term controlled-release urea application on the relative abundances of plant growth-promoting microorganisms

Controlled-release urea (CRUs), including polymer-coated urea (PCU), sulfur-coated urea (SCU), and polymer/sulfur dual layer-coated urea (PSCU), have been demonstrated to increase crop yield and nitrogen use efficiency (NUE). However, the effects of long-term application of CRUs on soil microbial community and function remain unclear. In this study, a 12-year (2009–2021) 24-season wheat -maize rotation lysimeter experiment was studied to investigate the effects of PCU, SCU, and PSCU on soil microbial community composition and function. Wheat was grown, soil chemical properties were analyzed, and soil biological properties including enzyme activities and microbial community structure and function at the wheat filling stage were determined in 2021. The results showed that soil organic matter (SOM) contents were markedly increased by 3.1∼5.0% under the CRUs compared to conventional urea. Meanwhile, some carbon, nitrogen, and sulfur cycle enzyme activities, including cellulase (CE), urease and arylsulfatase (AS), were significantly enhanced by 23.4∼32.4%, 6.6∼32.1%, and 2.5∼3.7% under the CRUs compared to conventional urea, respectively. Redundancy analysis indicated that changes in bacterial and fungal communities were driven by SOM. Co-occurrence network analysis showed that wheat growth promotion by the CRUs was strongly linked to the high relative abundance (Z-score) of bacterial and fungal module 1, which included such plant growth-promoting microorganisms (PGPMs) as Arthrobacter, Bryobacter, Bradyrhizobium, Microscypha, and Marasmius. Compared with PCU, SCU and PSCU showed a better effect in increasing the relative abundances of PGPMs while inhibiting the growth of nitrobacteria, denitrifying bacteria, and plant pathogens, thereby better promoting wheat yields and reducing N loss and plant disease. Of the three CRUs, SCU and PSCU have significantly increased SOM, which provided sufficient substrate for the growth of PGPMs, thus increasing wheat yield. This study provides a support for long-term CRUs application and sustainable agriculture.