Resin-coated Urea Research Articles

Severe nitrogen leaching and marked decline of nitrogen cycle-related genes during the cultivation of apple orchard on barren mountain

Limited available lands have led to the widespread practice of establishing orchards on barren mountains to expand apple cultivation in China. However, improper nitrogen (N) management strategies in intensive orchards escalate costs and also contribute to environmental contamination. A long-term field experiment was conducted in a representative apple-producing area in Shandong Province, China, to assess the environmental risks associated with newly established orchards. This research utilized lysimeters and soil metagenomic sequencing to investigate N leaching loss and the functional microbial profiles associated with the N cycle during apple cultivation on barren mountains. Five treatments were implemented: no inorganic N fertilizer, traditional farmer's fertilization, drip irrigation with a water-soluble fertilizer, resin-coated urea, and grass interplanting. Among treatments involving inorganic N, the total N leaching rate ranged from 16.5% to 30.7% of the total N fertilizer input. Notably, in treatments with equivalent N fertilizer applications, the water-soluble fertilizer treatment exhibited the highest N leaching loss rate -(20.2–29.0%), while the grass interplanting and resin-coated urea treatments showed significantly lower rates of N leaching loss (17.0–24.9% and 15.2–24.5%, respectively). The abundance of N cycle-related genes experienced a marked decline (17.1–18.8%) during the cultivation of orchards on barren mountains. The water-soluble fertilizer treatment displayed the highest potential for nitrification, contributing to elevated N leaching. Both resin-coated urea and traditional farmer's fertilization treatments exhibited the highest abundance of genes associated with N2O emission risk to the atmosphere. However, the grass interplanting treatment, while effectively reducing N leaching, also triggered the most pronounced soil acidification. Spearman correlation analysis revealed that the decline in pH, coupled with an increase in soil NO3--N concentration and electrical conductivity (EC), were the primary factors contributing to the reduction in the abundance of key N cycle functions. In summary, excessive use of inorganic N fertilizer in orchard environments led to increased N leaching, altered soil physicochemical properties, and significant impacts on N cycle-related genes. The elevated ionic strength in soils might be responsible for both the high N leaching loss and the decrease in N cycle function abundance. In intensive orchard cultivation, each N fertilization strategy mentioned above comes with its environmental drawbacks. Further investigation is warranted to achieve a balance between productivity and environmental protection.

The Effects of Long-Term Application of Stabilized and Coated Urea on Soil Chemical Properties, Microbial Community Structure, and Functional Genes in Paddy Fields

The addition of fertilizers is indispensable in agricultural production, and currently, there is a wide variety of new types of fertilizers available. For example, commonly used are stabilized fertilizers with inhibitors and coated slow-release fertilizers, among others. However, the long-term effects of these fertilizers, when applied continuously are still uncertain. This study will provide scientific and theoretical support for the development and promotion of these fertilizers. A 16-year paddy field with brown soil treated with different urease and nitrification inhibitors, sulfur-coated urea (SCU), and resin-coated urea (PCU) was studied. The study showed that long-term use of conventional urea nitrogen fertilizer resulted in a significant reduction in soil total phosphorus (TP). Long-term application of NBPT and conventional urea significantly increased soil organic matter (SOM). Moreover, except for HQ and NBPT+DMPP, the prolonged application of new urea fertilizers also significantly enhanced soil total potassium (TK). Application of SCU fertilizer in brown soil type paddy fields resulted in a significant decrease in soil pH over time. However, changes in pH had no effect on the abundance of ammonia-oxidizing bacteria (AOB), as AOB was mainly affected by soil-available N. DMPP, HQ+DCD, NBPT+DMPP, SCU, and PCU significantly reduced the 16S rRNA gene copy number of soil bacteria, with the greatest effect of coated urea fertilizer (SCU and PCU). Long-term application of stable urea fertilizer with HQ significantly reduced the bacterial community in paddy soil. Conversely, HQ+DCD-stabilizede urea fertilizer significantly increased the population structure and abundance of Basidiomycota fungi while decreasing the population structure and abundance of Rozellomycota fungi. DMPP-stabilized urea fertilizer notably increased the population structure and abundance of Ascomycota fungi while decreasing the population structure and abundance of Rozellomycota and Chytridiomycota fungi. Furthermore, HQ-stabilized urea fertilizer significantly reduced the population structure and abundance of Chytridiomycota fungi.

Effects of Slow-Release Fertilizer on Lotus Rhizome Yield and Starch Quality under Different Fertilization Periods

Slow-release fertilizer is an environmentally friendly fertilizer that is widely used in crop cultivation instead of traditional nitrogen fertilizer. However, the optimal application time of slow-release fertilizer and its effect on starch accumulation and rhizome quality of lotus remains unclear. In this study, two slow-release fertilizer applications (sulfur-coated compound fertilizer, SCU, and resin-coated urea, RCU) were fertilized under three fertilization periods (the erect leaf stage, SCU1 and RCU1; the erect leaf completely covering the water stage, SCU2 and RCU2; and the swelling stage of lotus rhizomes, SCU3 and RCU3) to study the effects of different application periods. Compared with CK (0 kg∙ha-1 nitrogen fertilizer), leaf relative chlorophyll content (SPAD) and net photosynthetic rate (Pn) remained at higher levels under SCU1 and RCU1. Further studies showed that SCU1 and RCU1 increased yield, amylose content, amylopectin and total starch, and the number of starch particles in lotus, and also significantly reduced peak viscosity, final viscosity and setback viscosity of lotus rhizome starch. To account for these changes, we measured the activity of key enzymes in starch synthesis and the relative expression levels of related genes. Through analysis, we found that these parameters increased significantly under SCU and RCU treatment, especially under SCU1 and RCU1 treatment. The results of this study showed that the one-time application at the erect leaf stage (SCU1 and RCU1) could improve the physicochemical properties of starch by regulating the key enzymes and related genes of starch synthesis, thus improving the nutritional quality of lotus rhizome. These results provide a technical choice for the one-time application of slow-release fertilizer in lotus rhizome production and cultivation.

Coated, Stabilized Enhanced-Efficiency Nitrogen Fertilizers: Preparation and Effects on Maize Growth and Nitrogen Utilization.

Coated, slow/controlled release, or stabilized enhanced-efficiency nitrogen fertilizers (EENFs) are effective in improving nitrogen utilization efficiency (NUE) and crop yield. Better performance is expected from coated, stabilized EENFs where urease and nitrification inhibitors are treated in coated fertilizers. Firstly, five coated EENFs with different mass proportions of nature rubber (NR) in coating were prepared: CU0, CU1, CU2, CU3, CU4, and CU5 (0, 10, 20, 30, 40, and 50% of NR in coating). The controlled release performance of CU was tested by hydrostatic release test and the microstructure of controlled release urea, so as to screen the optimal addition ratio of NR (ER: NR = 7:3, CU3). Secondly, two coated, stabilized EENFs, CSU1 and CSU2, were prepared with natural rubber-modified epoxy resin (ER: NR = 7:3) as coating material. Seven treatments of different N fertilization were set up: CK (no N fertilization), urea, CU3, SU1, and SU2 (urease and nitrification inhibitors-treated urea fertilizers), CSU1 and CSU2 (urease and nitrification inhibitors-treated natural rubber-modified epoxy resin-coated urea fertilizers). Ammonia volatilization experiment and column leaching experiment showed that compared with conventional urea, NH3 volatilization loss was reduced by 20% and inorganic N leaching loss was reduced by 26% from CSU2, respectively. In the pot experiment, maize grain yield of 162.92 and 206.96 g/pot was achieved by CSU1 and CSU2, respectively, 41 and 79%, respectively, higher than that achieved by conventional urea. SUs treatments were more effective than conventional urea treatment in improving maize grain yield and NUE, but lower than in CSUs. The NUE, nitrogen fertilizer apparent utilization efficiency, partial factor productivity of applied N, and nitrogen utilization efficiency were 46, 30, 46, and 32%, respectively, higher in CSU1 and 58, 62, 58, and 29%, respectively, higher in CSU2 than in the conventional urea treatment. Compared with CSU1, CSU2 had better agronomic effectiveness with a higher NUE. It is recommended that urease and nitrification inhibitors be sandwiched between urea prill and the coating for preparation of novel, environmentally friendly coated, stabilized EENFs with high agronomic effectiveness, high NUE, and low N loss.

Impact of controlled-release urea on rice yield, nitrogen use efficiency and soil fertility in a single rice cropping system

Overuse of nitrogen (N) fertilizer has led to low N use efficiency (NUE) and high N loss in single rice cropping systems in southeast China. Application of controlled-release urea (CRU) is considered as an effective N fertilizer practice for improving crop yields and NUE. Here, field experiments were conducted during 2015–2017 to assess the effects of two CRUs (resin-coated urea (RCU) and polyurethane-coated urea (PCU)) on rice yields, NUE and soil fertility at two sites (Lincheng town (LC) and Xintang town (XT)). Four treatments were established at each site: (1) control with no N application (CK), (2) split application of conventional urea (U, 270 kg N ha−1), (3) single basal application of RCU (RCU, 216 kg N ha−1), and (4) single basal application of PCU (PCU, 216 kg N ha−1). The N application rate in the CRU treatment compared to the U treatment was reduced by 20%. However, the results showed that, compared to split application of urea, single basal application of CRU led to similar rice grain yields and aboveground biomass at both sites. No significant difference in the N uptake by rice plant was observed between the U and CRU treatments at either site. There were no significant differences in the N apparent recovery efficiency (NARE) among the U, RCU and PCU treatments, with the exception of that in XT in 2015. Compared to application of U, application of CRU increased the N agronomic efficiency (NAE) and N partial factor productivity (NPFP) by 17.4–52.6% and 23.4–29.8% at the LC site, and 15.0–84.1% and 23.2–33.4% at the XT site, respectively, during 2015–2017. Yield component analysis revealed that greater rice grain yield in response to N fertilizer was attributed mainly to the number of panicles per m2, which increased in the fertilized treatments compared to the CK treatment. The application of CRU did not affect the soil fertility after rice harvest in 2016. Overall, these results suggest that single basal application of CRU constitutes a promising alternative N management practice for reducing N application rates, time- and labor-consuming in rice production in southeast China.

Control Effect of Side Deep Fertilization with Slow-release Fertilizer on Ammonia Volatilization from Paddy Fields

In order to reduce the ammonia volatilization in paddy fields, seven treatments were evaluated. These included three slow-release nitrogen fertilizers[sulfur-coated urea (SCU); resin-coated urea (RCU); release bulk blending fertilizer (RBB)], two fertilization modes[single base fertilization (B) and combined with panicle fertilizer (BF)], and conventional split fertilization (CN). The effects of side deep fertilization for slow-release nitrogen fertilizers on ammonia volatilization and surface water nitrogen dynamics were examined using a rice transplanter with a fertilizer sowing mechanism in the Taihu Lake region. The results showed that total nitrogen and ammonium nitrogen concentration in the surface water of the SCU treatment in the base period were higher, and those for RCU and RBB were lower than in the CN treatment. The cumulative ammonia volatilization during the whole rice season varied among different types of slow-release nitrogen fertilizers from 3.84% to 28.17% of the total N applied. The nitrogen loss from ammonia volatilization using the three slow-release nitrogen fertilizers was decreased when compared with conventional split fertilization. The ammonia volatilization loss exhibited the following relationship for the treatments:CN, B-SCU > BF-SCU, BF-RBB, BF-RCU, B-RBB, and B-RCU. When the slow-release nitrogen fertilizers were applied in single base fertilization, the total ammonia volatilization for the SCU was significantly higher than those for the RCU and RBB, while no significant differences were detected when these three slow-release fertilizers were combined with panicle fertilizer. Moreover, although the ammonia volatilization of BF-SCU was lower than that of B-SCU, those of BF-RCU and BF-RBB were higher than those with the B-RCU and B-RBB treatments, respectively. There are no significant differences for nitrogen volatilization when any of these three different fertilizers are applied as B or BF. The results for the emissions during ammonia volatilization during different stages indicated that the ammonia volatilization of SCU at the basal-tillering fertilization stage (7.54%) and the tillering-panicle fertilization stage (16.04%) were higher than those of the panicle fertilization-mature stage. The N loss from ammonia volatilization for RBB in the base-tillering fertilization stage (2.91%) increased more than in the tillering-panicle fertilization stage and panicle fertilization-mature stage. For RCU treatment, the highest rate for ammonia volatilization was detected at the panicle fertilization-mature stage (2.75%). Compared with the single base fertilization mode, ammonia volatilization during the panicle fertilization-mature stage was increased when combined with panicle fertilizer (BF) for the slow-release fertilizer. There was no obvious correlation between the N loss with ammonia volatilization for the three slow-release nitrogen fertilizers and the concentration of ammonium nitrogen in surface water during the panicle fertilization-mature stage.

Predicting Nitrogen Release from Parabolic-type Resin-coated Urea in Greenhouse Tomato and Cucumber Production

Increasing commercial use of controlled release fertilizer (CRF) has prompted the need to predict N release simply and viably in the greenhouse environment. Two CRFs were tested, i.e., P40d and P100d by incubating them for 40 or 100 days either in static water at 10, 15, 20, 25, and 35 °C or in the soil of vegetable plots in a greenhouse lacking temperature controls. Cumulative nitrogen release (CNR) from a CRF was represented by a parabola curve and significantly affected by the incubation temperature. A method to calculate Nm (the maximum N release percentage from CRF) was established using a first-order kinetic equation and the method of least squares. Nm was 90.9% to 99.9% for P40d and 72.1% to 87.1% for P100d at 10–35 °C, respectively. A relationship function between the N release rate and naturally fluctuating greenhouse soil temperatures was established using the activation energy of the N release reaction. Then a model was constructed with field temperature as the variable to predict N release throughout the entire greenhouse crop production season. The value of ψ representing a property of the coating material of a CRF is ≈1.0 for the release period of the CRF of 35–55 days and ≈1.2 of 80–120 days. We validated the model using two seasons of greenhouse tomato, Solanum lycopersicum L., and cucumber, Cucumis sativus L., production data, and found that the error was less than 12% points. This indicated that the constructed model was sufficiently simple, practical, and accurate for use by growers, and fertilizer industry and regulatory personnel.

被覆尿素の塩類飽和溶液中での溶出と水蒸気圧の関係 : 樹脂系被覆肥料の溶出機構と反応速度論的解析による溶出評価 (第4報)

被覆尿素の塩類飽和溶液中での溶出と水蒸気圧の関係 : 樹脂系被覆肥料の溶出機構と反応速度論的解析による溶出評価 (第4報)

Slow-release nitrogen fertilizers can improve yield and reduce Cd concentration in pakchoi (Brassica chinensis L.) grown in Cd-contaminated soil.

Cadmium (Cd) pollution in vegetable crops has become a serious problem in recent years. Owing to the limited availability of arable land resources, large areas of Cd-contaminated lands are inevitably being used for the production of vegetables, posing great risks to human health via the food chain. However, strategies to improve yield and reduce Cd concentration in crops grown in contaminated soils are being developed. In the present study, using pot experiments, we investigated the effects of two slow-release nitrogen fertilizers (SRNFs), resin-coated ammonium nitrate (Osmocote313s), and resin-coated urea (urea620), on the growth and Cd concentration of the Cd-contaminated pakchoi. The results showed that pakchoi grown in soil containing 5mgkg-1 of Cd-induced oxidative stress (indicated by malondialdehyde (MDA), H2O2, and O2·-) and photosynthesis inhibition, which in turn was restored with the application of SRNFs. However, pakchoi grown in Cd-contaminated soil supplied with Osmocote313s and urea620 showed 103 and 203% increase in fresh weight and 51-55% and 44-56% decrease in Cd concentration, respectively, as compared with their controls (pakchoi treated with instant soluble nitrogen fertilizers). On the basis of an increase in their tolerance index (47-238%) and a decrease in their translocation factor (7.5-21.6%), we inferred that the plants treated with SRNFs have a stronger tolerance to Cd and a lower efficiency of Cd translocation to edible parts than those treated with instant soluble nitrogen fertilizers. Therefore, in terms of both crop production and food safety, application of SRNFs could be an effective strategy for improving both biomass production and quality in pakchoi grown under Cd stress.

Maintaining yields and reducing nitrogen loss in rice–wheat rotation system in Taihu Lake region with proper fertilizer management

In the Tailake region of China, heavy nitrogen (N) loss of rice–wheat rotation systems, due to high fertilizer-N input with low N use efficiency (NUE), was widely reported. To alleviate the detrimental impacts caused by N loss, it is necessary to improve the fertilizer management practices. Therefore, a 3 yr field experiments with different N managements including organic combined chemical N treatment (OCN, 390 kg N ha−1 yr−1, 20% organic fertilizer), control–released urea treatment (CRU, 390 kg N ha−1 yr−1, 70% resin-coated urea), reduced chemical N treatment (RCN, 390 kg N ha−1 yr−1, all common chemical fertilizer), and site-specific N management (SSNM, 333 kg N ha−1 yr−1, all common chemical fertilizer) were conducted in the Taihu Lake region with the ‘farmer’s N’ treatment (FN, 510 kg N ha−1 yr−1, all common chemical fertilizer) as a control. Grain yield, plant N uptake (PNU), NUE, and N losses via runoff, leaching, and ammonia volatilization were assessed. In the rice season, the FN treatment had the highest N loss and lowest NUE, which can be attributed to an excessive rate of N application. Treatments of OCN and RCN with a 22% reduced N rate from FN had no significant effect on PNU nor the yield of rice in the 3 yr; however, the NUE was improved and N loss was reduced 20–32%. OCN treatment achieved the highest yield, while SSNM has the lowest N loss and highest NUE due to the lowest N rate. In wheat season, N loss decreased about 28–48% with the continuous reduction of N input, but the yield also declined, with the exception of OCN treatment. N loss through runoff, leaching and ammonia volatilization was positively correlated with the N input rate. When compared with the pure chemical fertilizer treatment of RCN under the same N input, OCN treatment has better NUE, better yield, and lower N loss. 70% of the urea replaced with resin-coated urea had no significant effect on yield and NUE improvement, but decreased the ammonia volatilization loss. Soil total N and organic matter content showed a decrease after three continuous cropping years with inorganic fertilizer application alone, but there was an increase with the OCN treatment. N balance analysis showed a N surplus for FN treatment and a balanced N budget for OCN treatment. To reduce the environmental impact and maintain a high crop production, proper N reduction together with organic amendments could be sustainable in the rice–wheat rotation system in the Taihu Lake region for a long run.

Effects of Urea and Controlled Release Urea Fertilizers on Methane Emission from Paddy Fields: A Multi-Year Field Study

A four-year (2008–2011) field study was implemented in a major rice-growing region of China to better understand the effect of urea and controlled release fertilier (CRF, thermoplastic resin-coated urea in this study) on CH4 emission from paddy fields. Over the four years, the average CH4 emission during the rice growing seasons was 76.9, 65.8 and 64.9 kg CH4 ha−1 in treatments CK (zero N), U (urea) and C (CRF), respectively. Urea and CRF significantly reduced CH4 emission by 14.4% and 15.6%, and increased average rice grain yield by 25.8% and 19.7% (P < 0.05), respectively, compared with treatment CK. Flooding duration would affect CRF's effect on CH4 emission from paddy fields. Under normal aeration conditions, CH4 emission tended to be 3.9%–15.2% lower in treatment C than in treatment U from 2009 to 2011, while it tended to be 4.2% higher under delayed aeration conditions in 2008. The findings suggest that mid-season aeration (MSA) starting on D30 (30 days after rice transplanting), just like the local practice, would optimize the CRF's effect on CH4 emission from rice fields in China. Over the four years, average rice yield did not differ between treatments U and C, and tended to be 5% lower in treatment C than in treatment U.

Effects of Coated Urea Amended with Biological Inhibitors on Physiological Characteristics, Yield, and Quality of Peanut

Four kinds of new developed urea, some of which were amended with biological inhibitors and coated and some of which were only coated with inorganic materials, were prepared by coating conventional granular urea (nitrogen 46.0%). Using a coated urea [resin-coated urea, 90 day, (RCU)] made in China and a conventional granular urea as check, their effects on physiological characteristics, yield, and quality of peanut were examined in a field experiment. The results indicated that four kinds of urea kept greater ammonium nitrogen (NH4 + -N) and nitrate nitrogen (NO3−N) contents at flowering stage (FS) and podding stage (PS) compared to conventional urea, and coated urea + dicyandiamide + hydroquinone treatment (CU + DCD + HQ) had the greatest contents, being similar to RCU treatment. At FS and PS, the chlorophyll content, photosynthetic rate, transpiration rate, and chlorophyll fluorescence parameters were significantly increased upon CU + DCD, CU + HQ, and CU + HQ + DCD treatments. In addition, CU + HQ + DCD treatment produced 27.3% more pod yield, 6.7% more total yield, and 9.17% more protein content and decreased NO3−-N content by 46.56% as compared to conventional urea treatment. This product has excellent slow-release capacity, is inexpensive and environmentally friendly, and could be especially useful in agricultural application.

Effectiveness of Urea-Coated Fertilizer on Young Immature Oil Palm Growth

Urea-coated fertilizers were invented to reduce ammonia volatilization and act as slow-release fertilizers in the oil palm field. This study was designed to examine the effectiveness of three types of urea-coated fertilizers namely Urease Inhibitor-coated urea 25% N (UICU), resin-coated urea 43% N (RCU), Sulphur-coated urea 32% N (SCU), uncoated urea 46% N (UU) and uncoated AS, (SOA) 21%N on oil palm early growth. The trial commenced from planting of the new oil palms until 36 months after planting (MAP). The fertilizer rates were applied with equivalent nutrient content of conventional compound fertilizer, NPKMg (9/9/12/4+0.5%B-AS based) as Control (Co) treatment. From the analysis, RCU showed significantly bigger girth size over UU and UAS by 13%, respectively starting at 18 MAP and 24 MAP while SCU recorded significant performance over UU by 8% at 36 MAP. The result also showed that SCU produced significantly longer fronds over Co, UU and UAS by 9%, 13% and 10%, respectively at 30 MAP. The similar performance was shown by SCU which produced bigger petiole cross section (PCS) and higher leaf dry weight over UU and Co at 30 to 36 MAP respectively. Foliar analysis found that higher leaf- N was recorded at the SCU plot and exceeded the UU by 18% and over the critical level by 7% at 24 MAP. From the results, it indicated that SCU had consistent performance over UU on girth size, frond length, PCS, leaf dry matter and leaf-N content. Even though there was no significant difference between the other types of urea coated fertilizers, SCU was able to produce more vigorous vegetative growth. Therefore, SCU fertilizer can be used as an alternative source of urea to improve immature oil palm growth especially in dry regions where high volatilization rate occurs. 

Effects of Phosphorous and Phosphoric Acids on Growth and Phosphorus Concentrations in Container-grown Tropical Ornamental Plants

Chinese hibiscus (Hibiscus rosa-chinensis), shooting star (Pseuderanthemum laxiflorum), downy jasmine (Jasminum multiflorum), areca palm (Dypsis lutescens), and `Jetty' spathiphyllum (Spathiphyllum) were grown in containers using Osmocote Plus 15-9-12 (15N-3.9P-10K), which provided phosphorus (two experiments), or resin-coated urea plus sulfur-coated potassium sulfate, which provided no phosphorus (one experiment). Plants were treated with water drenches (controls), drenches with metalaxyl fungicide only, drenches with phosphoric acid (PO4-P), drenches with metalaxyl plus phosphorus from phosphoric acid, drenches with PhytoFos 4-28-10 [4N-12.2P-8.3K, a fertilizer containing phosphorous acid (PO3-P), a known fungicidal compound], or a foliar spray with PhytoFos 4-28-10. Plants receiving soil drenches with equivalent amounts of P from PhytoFos 4-28-10, PO4-P, or PO4-P+metalaxyl generally had the greatest shoot and root dry weights and foliar PO4-P concentrations. There were no differences between the control and metalaxyl-treated plants, indicating that root rot diseases were not a factor. Therefore, responses from PhytoFos 4-28-10 were believed to be due to its nutrient content, rather than its fungicidal properties. Foliar-applied PhytoFos 4-29-10 produced plants that were generally similar in size to control plants or those receiving metalaxyl only drenches. Fertilizers containing PO3-P appear to be about as effective as PO4-P sources when applied to the soil, but are relatively ineffective as a P source when applied as a foliar spray. A distinct positive synergistic response for shoot and root dry weights and foliar PO4-P concentrations was observed for the PO4-P+metalaxyl treatment when no P was applied except as a treatment.

Effect of traditional and slow-release N fertilizers on growth of olive nursery plants and N losses by leaching

‘Picual’ olive trees ( Olea europaea L.) growing in 3 l plastic pots were fertilized with traditional or slow-release N fertilizers to study their growth and to determine N leaching losses. The traditional N fertilizers used were urea, ammonium sulfate, ammonium nitrate, and calcium nitrate; the slow-release N fertilizers selected were a sulfur-coated urea (Greenmaster), a nitrification inhibitor (Basammon), a low solubility material (Floranid), and a resin-coated urea (Multicote). Each plant received 2 g N from one of the aforementioned N fertilizers at the beginning of a first experiment, and 0.75 g N in a second experiment. Fertilized plants showed significantly increased vegetative growth compared to controls, but plants fertilized with 0.75 g N exhibited a greater shoot growth than those that received 2 g N. No significant differences were found among fertilizers when 0.75 g N was applied, but greater growth was obtained with Floranid and Multicote when 2 g N was applied to each plant. Regardless of N formulation, N was accumulated mainly in leaves of the olive plants. Most of the N recovered in the leachates was in the nitrate form. Total N losses were higher when ammonium nitrate and calcium nitrate were applied, and lower with the slow-release fertilizers, except for Basammon.

Analysis of Chlorosis Caused by Resin-Coated Urea Used in Nursery Bed for Padd-Rice

Analysis of Chlorosis Caused by Resin-Coated Urea Used in Nursery Bed for Padd-Rice

Nitrogen uptake and growth of two citrus rootstock seedlings in a sandy soil receiving different controlled-release fertilizer sources

Understanding the fate of different forms of nitrogen (N) fertilizers applied to soils is an important step in enhancing N use efficiency and minimizing N losses. The growth and N uptake of two citrus rootstocks, Swingle citrumelo (SC), and Cleopatra mandarin (CM), seedlings were evaluated in a pot experiment using a Candler fine sand (hyperthermic, uncoated, Typic Quartzipsamments) without N application or with 400 mg N kg–1 applied as urea or controlled-release fertilizers (CRF; either as Meister, Osmocote, or Poly-S). Meister and Osmocote are polyolefin resin-coated urea with longevity of N release for 270 days (at 25°C). Poly-S is a polymer and sulfur-coated urea with release duration considerably shorter than that of either Meister or Osmocote. The concentrations of 2 M KCl extractable nitrate nitrogen (NO3 –-N) and ammonium nitrogen (NH4 +-N) in the soil sampled 180 days and 300 days after planting were greater in the soil with SC than with CM rootstock seedlings. In most cases, the extractable NH4 + and NO3 – concentrations were greater for the Osmocote treatment compared to the other N sources. For the SC rootstock seedlings, dry weight was greater with Meister or Poly-S compared with either Osmocote or urea. At the end of the experiment, ranking of the various N sources, with respect to total N uptake by the seedlings, was: Meister = Osmocote > Poly-S > Urea > no N for CM rootstock, and Meister = Poly-S = Osmocote > Urea > no N for SC rootstock. The study demonstrated that for a given rate of N application the total N uptake by seedlings was greater for the CRF compared to urea treatment. This suggests that various N losses were lower from the CRF source as compared to those from soluble fertilizers.

Yield response of bell pepper and tomato to controlled‐release fertilizers on sand1

Abstract In fall (September‐December) 1991, bell pepper (Capsicum annuum L. cv. Jupiter) and in spring (February‐June) 1992, tomato (Lycopersicon esculentum Mill cv. Sunny), were grown with controlled release (CR) nitrogen (N) and potassium (K) fertilizers on EauGallie fine sand (sandy siliceous hyperthermic Alfic Haplaquod). Production system was the full‐bed polyethylene mulch with seepage (modified furrow) irrigation. For bell peppers, the CR‐N and ‐K source was an 18N‐0P‐15K analysis resin‐coated (RC) fertilizer, applied at 0, 25, 50, and 75% of the total N and K. The remaining N and K was supplied from soluble (SF) NH4NO3 and KNO3. The 50% PC N and K treatment increased early marketable yields and fruit size of pepper compared with the 100% SF (P<0.05). From early to mid‐season, soil nitrogen (NO3)‐ and ammonium (NH4)‐N concentrations were higher with decreasing CR‐N rates. However, residual soil NO3 and NH4 concentrations and macronutrient concentrations in shoots and in fruits were similar with CR and SF. For tomatoes, N and K were applied at two rates, lx and 1.5x, where the lx rate was equivalent to 195 N/ha and 324 K/ha. Fifty percent of the N or K was replaced by polymer and sulfur‐coated urea (PSCU) or resin‐coated urea (RCU) and resin‐coated K (RCK). None of the CR‐N and ‐K treatments improved fruit size or marketable yields compared with the NH4NO3‐KNO3 control. Higher N and K rates increased seasonal yield of marketable fruits (P<0.05). Residual concentrations of soil NH4‐ and NO3‐N and K were similar with CR and SF.

Container Medium and Slow-release Nitrogen Fertilizer Influence Growth and Quality of Salvia farinacea

We examined responses of Salvia farinacea Benth. (mealy blue sage, a water- and nutrient-efficient native landscape plant for the southern United States) to slow-release (8- to 9-month), resin-coated urea (39N-0P4K) preplant-incorporated at 0.5, 1, 2, or 3 kg N/m3 in 2 perlite: 1 vermiculite (PV) or 2 pine bark: 1 fine sand (BS) (both by volume). This slow-release fertilization was compared to weekly fertigation at 100 mg N/liter from ammonium nitrate (34N-0P4K). After 21 weeks of greenhouse culture in 3.8-liter containers, shoot dry weight was higher in BS than PV when these media received fertigation or contained slow-release fertilizer at 21 kg N/m3. Shoot dry weight and shoot quality were not increased by exceeding 1 kg N/m3 in PV or 2 kg N/m3 in BS. Fertigation resulted in shoot dry weight and shoot quality equal to the highest values achieved with slow-release fertilizer. Cate-Nelson analysis showed that shoot N concentration should be ≥ 4.0% for this element not to limit plant growth.

The Effects of Establishment Methods and Fertilization Practices on Nitrate Leaching from Turfgrass

AbstractA lysimeter study was conducted at the Ohio State University Turfgrass Research Center, Columbus, to investigate NO3‐N leaching losses from fertilized turfgrass. Nitrogen fertilizer treatments were applied to ‘Baron’ Kentucky bluegrass (Poa pratensis L.) seeded and sodded turf established on a Miamian silt loam (fine, mixed, mesic Typic Hapludalf). Treatments included two N sources, urea and resin‐coated urea (RCU); and Two fertilization programs, one that emphasize spring and summer applications (SSF) and the second program that included a late season application (LSF). Both the SSF‐ and LSF‐fertilization programs received 218.2 kg N ha−1 yr−1. The NO3‐N leachate concentrations from seeded turfgrass exceeded those from sodded turf for the first 3 mon. As the turf matured, NO3‐N losses from sod exceeded NO3‐N from the seeded plots. Leachate concentrations were 1.1 and 3.5 mg NO3‐N L−1 for seed and sod turf, respectively, from April 1990 through March 1991. Less rooting in the sodded plots resulted in greater N loss. Annual NO3‐N losses were not affected by N source. During the winter of 1991, significantly (P = 0.05) higher percolate NO3‐N concentrations were recorded from urea‐treated plots (3.66 mg NO3‐N L−1) vs. RCU (2.10 mg NO3‐N L−1), however. Similarly, N programs did not result in annual differences in percolate concentration, but differed during the winter of 1991. Concentrations were 3.37 and 2.39 mg NO3‐N L−1 for LSF and SSF, respectively. The NO3‐N leaching losses from all treatments exceeded the maximum concentration limit (MCL) early in the study. These high concentrations were caused by soil disturbance during establishment. During the 2nd yr, NO3‐N leaching results were more representative of typical turfgrass situations with mean annual flow‐weighted NO3‐N concentrations well below the MCL. Different N sources and fertilizer programs did not result in greater NO3‐N percolate losses compared to unfertilized turfgrass plots.