Slow-release Nitrogen Fertilizer Research Articles

Preparation and Application of Degradable Lignin/Poly (Vinyl Alcohol) Polymers as Urea Slow-Release Coating Materials.

The massive amount of water-soluble urea used leads to nutrient loss and environmental pollution in both water and soil. The aim of this study was to develop a novel lignin-based slow-release envelope material that has essential nitrogen and sulfur elements for plants. After the amination reaction with a hydrolysate of yak hair keratin, the coating formulation was obtained by adding different loadings (2, 5, 8, 14 wt%) of aminated lignin (AL) to 5% polyvinyl alcohol (PVA) solution. These formulations were cast into films and characterized for their structure, thermal stability, and mechanical and physicochemical properties. The results showed that the PVA-AL (8%) formulation had good physical and chemical properties in terms of water absorption and mechanical properties, and it showed good degradation in soil with 51% weight loss after 45 days. It is suitable for use as a coating material for fertilizers. Through high-pressure spraying technology, enveloped urea particles with a PVA-AL (8%) solution were obtained, which showed good morphology and slow-release performance. Compared with urea, the highest urea release was only 96.4% after 30 days, conforming to Higuchi model, Ritger-Peppas model, and second-order dynamic model. The continuous nitrogen supply of PVA-AL coated urea to Brassica napus was verified by potting experiments. Therefore, the lignin-based composite can be used as a coating material to produce a new slow-release nitrogen fertilizer for sustainable crop production.

Field and Economic Evaluation of Barley Productivity as Affected by Seed Rates and Slow-release Nitrogen Fertilizer Levels under Rainfed Conditions

A field experiment was conducted at the north western coast of Egypt under rainfed conditions to study the effects of seed rates (70, 95 and 120 kg ha-1) and nitrogen fertilizer treatments (0, 35, 70 and 105 kg N ha-1) of Ensiabeen-40% N as slow-release fertilizer compared with 105 kg N ha-1 as Ammonium nitrate (33.5%N) on productivity of barley cultivar Giza134. This investigation was conducted during 2019/2020 and 2020/2021 winter growing seasons. The treatments were laid out in a split plot design, with three replications. Plant height, spike length, number of grins spike-1, number of spikes per m2, 1000 grain weight, biological and grain yield were recorded. In addition, total income and net return (LE)/hactare were calculated. The results indicated that mean squares due to seasons, seed rates, nitrogen levels and their interactions were significant for most studied traits. Mean performance of the studied traits as affected by seasons, seed rates and nitrogen levels showed that, the most desirable values were obtained by SR1 for spike length (6.13cm), number of grains spike-1 (48.78 grain) and 1000 grain weight (42.15g), from SR2 for Biological yield (6.02 ton ha-1) and grain yield (1.85 ton ha-1) and from SR3 for plant height (78.28cm) and number of spikes m-2 (180.11 spike). For nitrogen level effects, N4 recorded the most favorable values for all studied traits; plant height (81.48cm), spike length (6.33cm), number of grains spike-1 (49.99 grain), number of spikes m-2 (187.60 spike), Biological yield (6.88 ton ha-1), grain yield (2.12 ton ha-1) and 1000 grain weight (42.89g). Grain yield exhibited highly significant and positive correlation with each of plant height (r= 0.833**), spike length(r=0.621**), number of grains spike-1 (r=0.768**), number of spikes m-2(r=0.880**) and weight of 1000 grains (r= 0.661**). The most contributing variable in the total variation of grain yield were number of spikes m-2, number of grains spike-1 and spike length. These variables contributed by 92.9% in the grain yield variation. The results also indicated that, the highest values in the total income were 19149 and 24990 pound.hec-1 respectively, and net return were 9492 and 15498 pound.hec-1 obtained from the interaction between seed rate of 5kg ha-1 (SR2) and 105 unit of slow release fertilizer (N4) during the two growing seasons. It could recommend this treatment to maximize the total income for the farmers in such location.

Effects of slow-release nitrogen and urea combined application on soil physicochemical properties and fungal community under total straw returning condition

Under the system of full straw returning, the relationship between soil fungal community diversity and soil physiochemical properties, and the combined application of slow-release nitrogen and urea is unclear. To evaluate its effect and provide an effective strategy for sustainable agricultural production, a 2-year field positioning trial was conducted using maize as the research object. The experiment was designed with two factors: straw treatment(S) and nitrogen fertilizer treatment(N),Six experimental treatments were set up,S1N0,S1N1,S1N2,S1N3,S1N4,S0N2,respectively.Analysis of 54 soil samples revealed 15 fungal phyla and 49 fungal classes. The composition of fungal communities in each treatment was basically the same, but there were significant differences in species abundance. Under total straw returning conditions, the combined application of slow-release nitrogen fertilizer and normal nitrogen fertilizer significantly increased the relative abundance of Ascomycota. During the jointing stage, tasseling stage and maturity stage, S1N4, S1N3 and S1N2 increased by 25.76%, 22.97%, 20.74%; 25.11%, 30.02%, 23.64% and 22.47%, 28.14%, 22.71% respectively compared with S0N2.The relative abundance of Basidiomycota was significantly reduced. Alpha diversity analysis showed that the straw returning mode significantly increased the Shannon index and decreased the Simpson index, which was obvious in the jointing stage and tasseling stage. The principal coordinate analysis analysis results showed that the fungal communities formed different clusters in the horizontal and vertical directions at the three growth stages of corn jointing, tasseling and maturity. At the jointing stage and tasseling stage, the communities of the straw return treatment and the straw removal treatment were separated, and the community distribution of each treatment was not significantly different in the mature stage. Total straw returning combined with slow-release fertilizer significantly (P＜0.05) increased the soil organic carbon, nitrate nitrogen and ammonia nitrogen content in each growth period, and increased the soil total nitrogen and hydrolyzable nitrogen content (P＞0.05).After the straw was returned to the field, the combined application of slow-release nitrogen fertilizer and common urea had a significant impact on soil urease, catalase, and sucrase activities. Among them, the three enzyme activities were the highest in the S1N3 treatment at the jointing stage and maturity stage, and the S1N4 treatment at the tasseling stage had the highest enzyme activity. Fungal community composition is closely related to environmental factors. Soil organic carbon, urease and catalase are positively correlated with Ascomycota and negatively correlated with Basidiomycota.

Management Strategy of Slow-Release Nitrogen Fertilizers for Direct-Sown Cotton after Wheat Harvest

The direct-sown cotton after wheat harvest (DSCWH) cropping system has attracted wide attention due to reduced labor inputs compared to transplanting. However, the management strategy of slow-release nitrogen is unclear in such a system. This study aims to investigate the impact of different timings and dosages of slow-release nitrogen fertilizer on the yield, biomass accumulation and distribution, and nitrogen absorption and nitrogen utilization in the DSCWH cropping system. This study was investigated at the experimental farm of Yangzhou University, China in 2020 and 2021, with the short-season cotton variety “Zhongmian 50” used as experimental material. Three dosages of the slow-release nitrogen fertilizer (45 kg·ha−1, 90 kg·ha−1, and 135 kg·ha−1) were applied at two stages of growth (two-leaf and four-leaf). The results showed that applying a 90 kg·ha−1 dosage at the two-leaf stage achieved the highest yield, which was increased by 12.6% compared to the no-fertilization control. Applying 90 kg·ha−1 of the slow-release nitrogen at the two-leaf stage promoted biomass accumulation, especially in reproductive organs, and this increase in biomass of reproductive organs was attributed to optimum nitrogen accumulation in reproductive organs (80~140 kg·ha−1). In addition, when 90 kg·ha−1 was applied at the two-leaf stage, there was a significant enhancement in nitrogen recovery efficiency (NRE), nitrogen agronomic use efficiency (NAE), and nitrogen physiological efficiency (NPE), with increases of 7.2% to 13.0%, 5.7% to 5.8%, and 5.6% to 6.5%, respectively. These results revealed that applying slow-release nitrogen fertilizer with the optimal dosage at the seedling stage could significantly enhance nitrogen use efficiency, nitrogen accumulation and partitioning, and biomass accumulation and distribution, which ultimately resulted in a higher lint yield in DSCWH. Therefore, to optimize yield and NUE, 90 kg·ha−1 slow-release nitrogen applied at the two-leaf stage would be recommended in the direct-sown cotton after wheat harvest cropping system.

Slow-release nitrogen fertilizer reduces input without yield loss in a rice-crayfish integrated system

Slow-release nitrogen fertilizer reduces input without yield loss in a rice-crayfish integrated system

Novel coating of slow-release nitrogen fertilizers: Characterization and assessment

Developing novel fertilizers that reduce nitrogen release rate receives worldwide interest as a potential means for improving nitrogen utilization efficiency. Making these fertilizers sustainable, this work introduces various attempts to prepare slow-release nitrogen using different materials comprised of agro-industrial wastes such as sugarcane (SC) and beet filter cakes (mud) besides, sulfur, gypsum, and zeolite to cover two nitrogen sources. The prepared coated nitrogen fertilizers were characterized using SEM-EDX. Afterward, an incubation trial was conducted to appraise the produced slow-release fertilizers via mixing with three soils (from Egypt and Sudan) at various incubation periods. The tested coating process enhanced the surface morphology of the fertilizer grains, in which the surface became smoother and all the cracks and cavities were filled with the coating material, which is critical for the physical barrier property and preventing moisture penetration into the core. ANOVA analysis indicated that the released values of N were significantly varied according to the soil type, source of N, and the coating material. Zeolite was effective as a coating material for all nitrogen fertilizers. The coated granules by SC material provided a steady, adequate nitrogen supply throughout the incubation. Beet mud treatments showed the lowest N release among all coating materials, but the liberation of N gradually increased with time elapsed. The beet and sugarcane mud can be considered promising covering materials for developing environmentally friendly and cost-effective slow-release fertilizers. The results showed continuous release of N in the soils from all prepared coated fertilizers til the end of the incubation, enhancing the feasibility for agricultural application.

Attempts to Improvement the Growth and Fruiting of Flame Seedless Grapevines Growing in Sandy Soil Using Slow-Release Nitrogen Fertilizers

Attempts to Improvement the Growth and Fruiting of Flame Seedless Grapevines Growing in Sandy Soil Using Slow-Release Nitrogen Fertilizers

Irrigation Water and Nitrogen Fertilizer Management in Potato (Solanum tuberosum L.): A Review

Intensive irrigation and nutrient management practices in agriculture have given rise to serious issues in aquifer water depletion and groundwater quality. This review discusses the effects of irrigation and nitrogen management practices on potato growth, yield, and quality, and their impacts on water and nitrogen use efficiencies. This review also highlights the economics and consequences of applying deficit irrigation strategies in potato production. Many researchers have demonstrated that excessive irrigation and nitrogen application rates negatively impact potato tuber yield and quality while also increasing nitrate leaching, energy consumption, and the overall costs of production. An application of light-to-moderate deficit irrigation (10–30% of full irrigation) together with reduced nitrogen rates (60–170 kg/ha) has a great potential to improve water and nitrogen use efficiencies while obtaining optimum yield and quality in potato production, depending on the climate, variety, soil type, and water availability. There is an opportunity to reduce N application rates in potato production through deficit irrigation practices by minimizing nitrate leaching beyond the crop root zone. The best irrigation and nitrogen management techniques for potato production, as discussed in this review, include using sprinkle and drip irrigation techniques, irrigation scheduling based on local crop coefficients, soil moisture content, and crop modeling techniques, applying slow-release nitrogenous fertilizers, split nitrogen application, and applying water and nitrogenous fertilizers in accordance with crop growth stage requirements.

Coupling effect analysis of drip irrigation and mixed slow-release nitrogen fertilizer on yield and physiological characteristics of winter wheat in Guanzhong area

ContextOptimising the management of water and fertilizer, and fully exploiting the positive effects of the coupling of water and fertilizer, are important ways of achieving high crop yields and promoting the sustainable development of water-efficient agriculture. ObjectiveThe objective of this study was to investigate the coupling effects of different irrigation levels and different mixing ratios of slow-release nitrogen fertilizers on the physiological growth characteristics and yield of winter wheat in Guanzhong region under drip irrigation. MethodsIn this study, field experiments were conducted in two winter wheat growing seasons, 2018–2019 and 2019–2020. The study included three irrigation levels: W1 (60% ETc, where ETc is the evapotranspiration of the crop), W2 (80% ETc), and W3 (100% ETc); and four N fertilizer treatments: U (100% urea), UNS1 (urea: slow-release N fertilizer = 1:1), UNS2 (urea: slow-release N fertilizer = 1:3) and SRF (100% slow-release N fertilizer). ResultsCompared to W1 and W2, W3 prolonged the winter wheat leaf functional period, increased leaf area index and net photosynthetic rate (Pn), and promoted dry matter accumulation. The total N content of winter wheat decreased by 22.67% and 9.93% under W1 and W2 conditions, respectively. The nitrogen use efficiency (NUE) decreased by 5.87% and 1.97%, respectively, leading to a decrease in yield. Slow-release nitrogen fertilizer (SRF) and its mixture treatments (UNS1, UNS2) increased post-flowering nitrogen uptake in winter wheat compared to U. At the same irrigation level, water use efficiency (WUE) was increased by 34.03%, 13.35%, and 20.86% in the UNS2 treatment compared to U, UNS1, and SRF, respectively. W3UNS2 obtained the highest grain yield: 8026.32 kg hm−2 (2018–2019) and 8993.25 (2019–2020) kg hm−2, with a 9.85–68.24% yield increase compared to other treatments. Und4er the treatments of this study, yield, WUE, and NUE of winter wheat reached 90% of the maximum at irrigation levels of 82.04–91.83% ETc and 59.18–83.67% of slow-release N fertilizer in blended fertilizer. ConclusionsUnder water stress conditions, UNS1 and UNS2 can mitigate the effects of water deficit on plant growth and stabilize grain yield. ImplicationsThis study provides useful information for optimising water and nitrogen management decisions for winter wheat in semi-arid climatic regions, and contributes to the promotion of sustainable development of wheat production and water-efficient agriculture.

Evaluation of Nitrogen Release Characteristics and Enhanced Efficiency of a Novel Synthetic Slow-Release Nitrogen Fertilizer

Evaluation of Nitrogen Release Characteristics and Enhanced Efficiency of a Novel Synthetic Slow-Release Nitrogen Fertilizer

Preparation and characterization of biochar-based slow-release nitrogen fertilizer and its effect on maize growth

Biochar (BC) is often used to prepare carbon-based slow-release fertilizers, but the slow-release performance of traditional biochar-based fertilizers is still low and needs to be further improved. In addition, the slow-release mechanisms, such as physical encapsulation, adsorption, functional group action, etc., of specific biochar-based slow-release nitrogen fertilizers (BSRNFs) are unclear. In this study, six BSRNFs were synthesized and their nitrogen release patterns and mechanisms were investigated. Soil column leaching experiments demonstrated that BSRNFs significantly slowed down the release of nitrogen. The release performance of sodium alginate coated BSRNFs with carbon fertilizer ratio of 2: 1 (BUS2) was the optimal; and the cumulative nitrogen release of BUS2 was 65.91% within 74 days, which was 28.56% lower than that of urea. The maize pot experiment showed that the maize yield of BUS2 treatment group was 7.51% higher than that of ordinary sulfur coated urea treatment group. The samples of BUS2 before and after sustained release were characterized., it was confirmed that BUS2 captured nitrogen by physical encapsulation, physical adsorption, hydrogen bonding and functional group action, so as to play the role of slow release. Moreover, the production cost of BUS2 was 29.32% lower than that of urea fertilizer. In conclusion, the newly-developed BUS2 is proven to be easily-synthesized and low cost, while possessing excellent slow-release nitrogen performance and increasing crop yield. Mass production and application of BUS2 in field are promising to contribute to the green agricultural development.

Growth, Yield, and Agronomic Use Efficiency of Delayed Sown Wheat under Slow-Release Nitrogen Fertilizer and Seeding Rate

Delayed sowing of wheat is a common problem in Punjab that exacerbates serious yield loss. However, individual or combined applications of seed rate and slow-release nitrogen fertilizer significantly impacted their efficacy in improving crop growth and productivity. In this regard, the present study explored the potential of slow-release nitrogen fertilizers (control (CK), simple urea (SU), neem-coated urea (NCU), and sulfur-coated urea (SCU)) to improve the growth, yield, and physiological and biochemical attributes of delayed sown wheat with three seed rate [(100 kg ha−1 (S1), 125 kg ha−1 (S2), and 150 kg ha−1 (S3)]. The study was carried out at the Postgraduate Agricultural Research Station of the University of Agriculture Faisalabad in 2018–19 and 2019–20. The study findings revealed that the sulfur-coated urea performed better under S3 seed rate. Combining SCU with S3 significantly increased leaf area index by 0.99 cm2 and plant height by 8.24% compared to simple urea, maximum spikelets, and spike length by 3.9 and 3.8 cm, respectively. The SCU with S3 treatment also increased the biological yield by 43% and 41% and the grain yield by 46% in 2018–2019 and 2019–2020, respectively, compared to CK. Similarly, higher N contents in straw and grain were recorded in the interaction of SCU with S3 treatment. Likewise, the SCU with S3 treatment enhanced the physiological attributes, i.e., chlorophyll contents and transpiration rate, by 18% and 25%, respectively, and decreased internal CO2 by 25.5%, compared to CK. In conclusion, applying sulfur-coated urea with a seed rate of 150 kg ha−1 could be considered a potential strategy for improving the growth and productivity of delayed sown wheat.

Preparation, characterization and nitrogen availability of nitrohumic acid as a slow-release nitrogen fertilizer

ABSTRACT Nitrohumic acids (NHAs) are considered as promising slow-release N fertilizers. In this study, NHA was produced from six organic feedstocks, including coal, leonardite, municipal waste compost, sewage sludge, and apple and beech biochars via nitration using nitric acid. The nitration process was conducted in two ways: (i) after humic acid (HA) extraction (NHAD), and (ii) before HA extraction (NHAID). The prepared NHAs were then characterized using FT-IR and CHNS analysis. Additionally, N mineralization of NHAs was investigated in a sandy loam soil sample. The FT-IR spectra showed that both methods of nitration loaded nitro (NO2) groups into the HA structure. However, the CHNS analysis indicated the highest rate of N increase for NHAD (106%) and NHAID (113%) extracted from leonardite. Moreover, on average, the total acidity and carboxylic groups of the HAs increased by 7.5% and 14.5% after the nitration processes, respectively. The highest extraction yields of NHAD (26.1%) and NHAID (42.1%) were also obtained from leonardite. Although the extraction yield of NHAID was on average two times higher than that of NHAD, NHAD indicated a higher soil N availability (1.4 times). We concluded that the NHAD extracted from leonardite could be considered as an alternative slow-release N fertilizer.

Polyvinyl alcohol composite hydrogels/epoxidized natural rubber composites (CMCS/PVA/CS-ENR) with core-shell structure as biomass coating material for slow-release nitrogen fertilizer

Using natural rubber (NR)/chitosan (CS)/polyvinyl alcohol (PVA) as raw materials, biodegradable semi-IPN (semi-interpenetrating polymer network) composites were prepared by thiol-epoxy click reaction under UV light, which was used as the shell of sustained release preparation. Using polyvinyl alcohol (PVA)/carboxymethyl chitosan (CMCS) as raw material and vanillin as the cross-linking agent, hydrogen-bonded hybrid network hydrogel loaded with urea was prepared by freeze-thaw cycle, which was used as the core of sustained-release preparation. Finally, a green-coated urea fertilizer with core-shell structure was prepared to ameliorate the environmental pollution of slow-release fertilizer (for example, synthetic polymer-coated fertilizers are difficult to biodegrade), as well as to achieve the water retention and the effective slow-release. The high CS/PVA contents and the combination of the hydrogel core and the rubber shell significantly improved the mechanical properties of the coating material (tensile strength above 5 MPa, elongation at break up to 1400 %), hydrophilicity (to promote the degradation rate of the rubber shell) and soil water retention of the coating material (close to pure hydrogel), showing enhanced reaction. In terms of slow-release effect, coated nitrogen fertilizer with 3 % CS content, 5 % PVA content and 10-min coating time (SRP3/10) achieved the best slow-release effect of nitrogen (N) in water (62.7 % at 10 days), which was related to the hydrophilicity, semi-IPN skeleton and the cross-linking structure of the network, and the release conformed to the Korsmeyer-Peppas model with a non-Fickian diffusion release mechanism, indicating that the behavior of N release was mediated by a combination of drug diffusion and skeleton dissolution.

Cellulose-based slow-release nitrogen fertilizers: Synthesis, properties, and effects on pakchoi growth

The application of most slow-release fertilizers is limited by complex preparation processes and short slow-release periods. In this study, carbon spheres (CSs) were prepared by a hydrothermal method using cellulose as the raw material. Using CSs as the fertilizer carrier, three new carbon-based slow-release nitrogen fertilizers were prepared using direct mixing (SRF-M), water-soluble immersion adsorption (SRFS), and co-pyrolysis (SRFP) methods, respectively. Examination of the CSs revealed regular and ordered surface morphology, enrichment of functional groups on the surfaces, and good thermal stability. Elemental analysis showed that SRF-M was rich in nitrogen (total nitrogen content of 19.66 %). Soil-leaching tests showed that the total cumulative nitrogen release of SRF-M and SRF-S was 55.78 % and 62.98 %, respectively, which greatly slowed down the release of nitrogen. Pot experiment results revealed that SRF-M significantly promoted the growth of pakchoi and improved crop quality. Thus, SRF-M was more effective in practical applications than the other two slow-release fertilizers. Mechanistic studies showed that CN, -COOR, pyridine-N and pyrrolic-N participated in nitrogen release. This study thus provides a simple, effective, and economical method for the preparation of slow-release fertilizers, providing new directions for further research and the develop of new slow-release fertilizers.

Network interpenetrating slow-release nitrogen fertilizer based on carrageenan and urea: A new low-cost water and fertilizer regulation carrier

Modern agriculture presents new requirements of low cost, high water retention and degradability for superabsorbent and slow-release fertilizers. In this study, carrageenan (CG), acrylic acid (AA), N, N ‘-methylene diacrylamide (MBA), urea and ammonium persulfate (APS) were used as raw materials. A kind of high water absorption, water retention, nitrogen slow release and biodegradable carrageenan superabsorbent (CG-SA) was prepared by grafting copolymerization. The optimal CG-SA was obtained with a water absorption rate of 680.45 g/g by orthogonal L18(3)7 experiments and single-factor experiments. The water absorption behavior of CG-SA in deionized water and salt solution were studied. The CG-SA was characterized before and after degradation by FTIR, SEM. The nitrogen release behavior and kinetic characteristics of CG-SA were investigated. In addition, CG-SA degraded 58.33 % and 64.35 % in soil at 25 °C and 35 °C after 28 days. All the results indicated that the low-cost and degradable CG-SA can achieve simultaneous slow release of water and nutrients, which is expected to be widely used as a new water-fertilizer integration technology in arid and poor areas.

Valorization of nitrogen-rich melamine as a nitrogen source in the production of maize (Zea mays L.)

Maize is important for the biofuel and bio-based products. Building a clean maize production system could minimize the environment pollution from the N loss from the sloping land and achieve the industrial sustainable development. As a nitrogen-rich source, melamine could be used as a slow-release nitrogen (N) fertilizer, which provides a route for the recycling of melamine waste and the combatting of N loss from fertilizers. Model N release of melamine was compared with urea, sulfur(S)-coated urea via N loss in leaching column under intermittent leaching and under the ploughing fertilizer in the farmland soil. Only 7.12 % of the total nitrogen (TN) was lost from the 21 irrigation events, while the loss of TN from urea reached 77.28 %. TN from urea would be release totally in soil within 14 days in the ploughing fertilizer experiment, but 62 % of melamine was remained after 144 days. In order to evaluate the efficacy of melamine as an N fertilizer, plot experiments with an N rate of 180 kg ha-1 were carried out using pure melamine, urea and S-coated urea as well as mixed melamine/urea at 2:8, 1:1 and 7:3 by the N ratio. Melamine fertilization alone was unable to satisfy the N demand of maize, but the melamine/urea mixture (1:1) was comparable to the commercial S-coated urea in both years in terms of the grain yield (2217 kg ha-1 in 2019, 2368 kg ha-1 in 2020), total aboveground dry matter (5076 kg ha-1 in 2019, 4815 kg ha-1 in 2020), aboveground N uptake (36 kg ha-1 in 2019, 48 kg ha-1 in 2020), partial factor productivity of nitrogen (12.32 kg kg-1 in 2019 and 13.16 kg kg-1 in 2020) and net return (1474 USD in 2019, 1606 USD in 2020). Melamine accumulation in the maize grain measured from ELISA (enzyme-linked immunosorbent assay) ranged from 0.24 to 1.8 mg kg-1. The valorization of the melamine waste into N fertilizer by blending with urea was a possible way of reducing melamine pollution, alleviating N loss in hilly area and building a recyclable agriculture system.

Characteristics of Soil Carbon, Nitrogen, Phosphorus, and Ecological Stoichiometry in Vegetable Fields and Orchard in the Coastal Area of Fuzhou

The soil ecological stoichiometric characteristics of different agricultural land use types have a certain indicator function for characterizing the level of soil nutrient supply and are of great significance to the management of nutrient resources in farmland ecosystems. In order to reveal the soil carbon (C), nitrogen (N), and phosphorus (P) contents and their ecological stoichiometric characteristics in different vegetable fields and orchard agricultural land use types, this study took vegetable fields (taro field and jicama field) and orchards (citrus tree orchard, watermelon field, and pear tree orchard) as the research objects in the coastal area of Fuzhou City. The contents of soil C, N, and P and their ecological stoichiometric characteristics in different vegetable fields and orchard agricultural land uses were measured and analyzed. The soil C and N contents were in the order of orchard>vegetable field (P<0.05). The C content in the citrus tree orchard was the highest (4.44 g·kg-1), and the N content in the watermelon field was the highest (1.46 g·kg-1). The soil P content was vegetable field>orchard (P<0.05), and the jicama field had the highest P content (0.19 g·kg-1). The soil carbon and nitrogen ratio (C/N), carbon and phosphorus ratio (C/P), and nitrogen and phosphorus ratio (N/P) were orchard>vegetable field (P<0.05). Among them, the citrus tree orchard had the highest C/N (7.40) and C/P (61.43), and the watermelon field had the highest N/P (10.27). Soil N content was significantly and negatively correlated with bulk density and conductivity (r=-0.49, r=-0.28, P<0.05), and there was a significant and positive correlation with soil water content (r=0.61, P<0.05). C/P and C/N were significantly and positively correlated with SOM (r=0.71, r=0.64, P<0.01). In the process of crop planting and management in the coastal area of Fuzhou City, it is necessary to reasonably add nitrogen fertilizer to compensate for the N limitation, and slow-release nitrogen fertilizer is better for promoting the sustainable supply of nitrogen nutrients in the growth and development of crops.

Efficient Nitrogen Management Technologies for Sustainable Rice Production

The use of nitrogen (N) fertilizers in rice fields as a source of nutrition is the major source of emission of nitrous oxide (N2O). Two key factors which control the flux of N2O at the field level are the amount of N supplied and the efficiency at which it is absorbed by plants. To reduce the N2O emissions, optimum N fertilizer application (in terms of input rate and time of application) and ideal fertilizer selection are crucial. Optimizing N use efficiency (NUE) is crucial to sustain productivity and profitability. Depending on edaphic and climatic conditions, improved N management can dramatically cut greenhouse gases (GHGs) emissions. Producers must ensure that the kind, rate, and time of N application do not result in substantial losses owing to volatilization, leaching, or denitrification. Adoption of best nitrogen management practices like deep placement of urea, use of nitrification inhibitors, urease inhibitors, and slow-release nitrogen fertilizers will reduce the N loss and increase NUE. The goal of this review is to discuss in detail the various technologies that have been developed and refined to improve NUE and protect the environment.

Slow-Release Nitrogen Fertilizers with Biodegradable Poly(3-hydroxybutyrate) Coating: Their Effect on the Growth of Maize and the Dynamics of N Release in Soil.

Fertilizers play an essential role in agriculture due to the rising food demand. However, high input fertilizer concentration and the non-controlled leaching of nutrients cause an unwanted increase in reactive, unassimilated nitrogen and induce environmental pollution. This paper investigates the preparation and properties of slow-release fertilizer with fully biodegradable poly(3-hydroxybutyrate) coating that releases nitrogen gradually and is not a pollutant for soil. Nitrogen fertilizer (calcium ammonium nitrate) was pelletized with selected filler materials (poly(3-hydroxybutyrate), struvite, dried biomass). Pellets were coated with a solution of poly(3-hydroxybutyrate) in dioxolane that formed a high-quality and thin polymer coating. Coated pellets were tested in aqueous and soil environments. Some coated pellets showed excellent resistance even after 76 days in water, where only 20% of the ammonium nitrate was released. Pot experiments in Mitscherlich vegetation vessels monitored the effect of the application of coated fertilizers on the development and growth of maize and the dynamics of N release in the soil. We found that the use of our coated fertilizers in maize nutrition is a suitable way to supply nutrients to plants concerning their needs and that the poly(3-hydroxybutyrate) that was used for the coating does not adversely affect the growth of maize plants.