Polymer-coated Urea Research Articles

Effects of different types of slow- and controlled-release fertilizers on rice yield

This experiment explored the effects of single application of seven types of slow- and controlled-release fertilizers on rice yield and various population characteristics. Based on a study of the nitrogen (N) release characteristics of these fertilizers, pot experiments were conducted in 2018 and 2019 with split fertilization (CK, urea applied split equally at basal and panicle initiation stages, respectively) as control, which assessed the effects on SPAD value, yield and yield components, dynamic changes of rice tillers and dry matter accumulation. The results showed that the N release characteristics of different types of slow- and controlled-release fertilizers were significantly different. Polymer-coated urea (PCU) showed a controlled-release mode and provided sustained release throughout the whole growth stages. Sulfur-coated urea (SCU) exhibited a slow-release mode, providing insufficient release at the middle and late stages. Urease inhibitor urea (AHA) and urea-formaldehyde (UF) yielded a rapid-release mode, with an explosive N release at the early stage and no release at the middle and late stages. These results showed that PCU delayed the peak seedling stage. Compared with CK, dry matter accumulation and SPAD showed no significant differences, and due to the continuous release of N throughout the growth stages, rice yield, spikelets per panicle, seed setting rate, and 1 000-grain weight were all increased. Owing to the lack of N supply at the late stage and the low number of spikelets, SCU led to a reduction of rice yield, which is nevertheless not statistically significant. AHA and UF were susceptible to environmental factors and had varying effects on rice yield. The results of this experiment indicated that given a fixed amount of N applied in a pot, the stronger the N supply capacity and the longer the effective duration time of the fertilizer, the higher the dry matter accumulation at the late growth stage, and the higher the rice yield.

Effects of Enhanced-Efficiency Nitrogen Fertilizers on Soil Microbial Biomass and Respiration in Tropical Soil Under Upland Rice Cultivation

While over-use of N fertilizers can suppress microbial biomass, application of urease inhibitors is known to be a potential way to rebuilt microbial diversity and improve soil functions. However, the hypothesis of this study is that the application of N fertilizers regardless of the source would increase soil microbial biomass and reduce soil respiration. A two-year field experiment was conducted to assess the effects of enhanced-efficiency N sources on soil microbial biomass, and soil respiration. The experiment was set up in a randomized block design in a 3 × 4 + 1 factorial scheme, with four replicates. Treatments comprised three sources (conventional uncoated urea, NBPT (N-(n-butyl) thiophosphoric triamide)-treated urea, and polymer-coated urea) and four rates (30, 60, 90 and 120 kg ha-1) of N, in addition to a control treatment (no fertilizer application). Microbial biomass C (MBC) and microbial biomass N (MBN), and soil respiration (C-CO2 and qCO2) were determined in upland rice rhizosphere in each crop season. Responses of soil microbial properties to N fertilization were dependent on the N rates, but no significant effect of the N sources was observed. All measured parameters, except MBC in the first season and C-CO2 in the second season, were increased with increasing N rates. However, the application of N higher than 60 kg ha-1 suppressed soil microbial biomass, as well as soil respiration.  Therefore, the lack of response by added urease inhibitors to the N sources indicate that optimizing N rates for upland rice production is a far more effective option for improving soil microbial community than using enhanced-efficiency N sources.

Alternate wetting and drying irrigation combined with the proportion of polymer-coated urea and conventional urea rates increases grain yield, water and nitrogen use efficiencies in rice

• Irrigation regimes interact with proportions of PCU and CU rates on the grain yield, WUE and NUE in rice. • A moderate soil drying regime combined with the 70 % PCU + 30 % CU produces a better synergistic interaction. • Improved root and shoot growth and higher nitrate-N content in the soil account for the synergistic interaction. Interaction between water and nitrogen (N) plays important roles in regulating crop yields and resource use efficiencies. Little is known, however, if and how irrigation regimes could synergistically interact with proportions of polymer-coated urea (PCU) and conventional urea (CU) rates to increase grain yield, water use efficiency (WUE) and N use efficiency (NUE) in rice. This study investigated the question. Field experiments were conducted with three N treatments, 100 % CU (N1), 100 % PCU (N2), and 70 % PCU + 30 % CU (N3), and two irrigation regimes, continuously flooded (CF) and alternate wetting and moderate drying irrigation (AWMD). The results showed that grain yield, internal N use efficiency, N partial factor productivity, and WUE exhibited small differences among the three N treatments in the CF regime, whereas they were the highest under N3, and the lowest under N1 in the AWMD regime. The above parameters were the highest under the N3 + AWMD among the all treatment combinations. Enhanced root and shoot growth, especially increases in root oxidation activity, leaf area duration, crop growth rate, and photosynthetic NUE, and increased N uptake, pre-stored carbon remobilization from stems during grain filling, and harvest index at maturity, and higher nitrate-N content in the soil accounted for a better synergistic interaction under the N3 + AWMD treatment. Collectively, adoption of an AWMD regime with an appropriate proportion of PCU and CU rates (70 % PCU + 30 % CU) can synergistically increase grain yield and resource use efficiency by improving biological process in rice.

Twice-split application of controlled-release nitrogen fertilizer met the nitrogen demand of winter wheat

As a new long-acting fertilizer, controlled-release nitrogen fertilizer (CRNF) has been shown to increase crop yield and improve nitrogen use efficiency (NUE) of fertilizer in many production systems. However, due to the limitation of nutrient release longevity of CRNF and the nitrogen demand characteristics of winter wheat (Triticum aestivum L.), further study is needed on the appropriate application technology of CRNF. In the present study, using polymer-coated urea (PCU) and sulfur-coated urea (SCU) as materials, the characteristics of nitrogen release from one-time or twice-split application of CRNF and its effect on the nitrogen uptake and growth of wheat were investigated in a two-year field experiment. The results indicated that nitrogen release from the twice-split application of PCU and SCU was synchronized with the nitrogen demand of wheat at different stages. Compared with urea multiple-split application (CK) and CRNF one-time application (PCU1 and SCU1), CRNF applied twice, at pre-sowing and re-greening (PCU2 and SCU2), maintained a high level of soil inorganic nitrogen after jointing, which met the second peak demand for nitrogen and improved the nitrogen uptake of wheat. Both PCU2 and SCU2 were found to be beneficial in delaying the senescence of leaves and the decline of photosynthetic performance after anthesis, which significantly increased the accumulation of post-anthesis dry matter and significantly affected the grain yield, with an increase of 9.96–15.11 % compared with multiple-split application of urea. PCU2 and SCU2 also improved NUE by 6.71–10.33 %. The results of this study demonstrate that CRNF applied twice was a good fertilization method for synchronizing nitrogen release from fertilizer and the nitrogen demand of wheat, thus improving wheat yield and NUE and decreasing the labor required for fertilizer application.

Agronomic Assessment of a Controlled-Release Polymer-Coated Urea-Based Fertilizer in Maize.

Increasing nutrient use efficiency of fertilizers is one of the major challenges to improve crop yields and minimize environmental impacts. This work compared the efficacy of a new ecological polymer-coated urea fertilizer and a slow release urea-based traditional fertilizer. Reductions in the N doses of the polymer-coated fertilizer were tested. A comparative study was first carried out by measuring the different physiological and yield parameters at the micro-scale level, and later-on field experiments were performed. Grain yield in the field was significantly higher (20%) when applying the new controlled-release fertilizer than when using the traditional one at the same dose. A 20% reduction in N content in the new fertilizer gave similar physiological and yield responses compared to the traditional fertilizer. We conclude that this new fertilizer can be used in extensive cropping of maize, guaranteeing at least the same yields than traditional fertilizers, with a reduction on the impact on soil properties and nitrogen losses.

Nitrogen Recovery from Enhanced Efficiency Fertilizers and Urea in Intensively Managed Black Walnut (Juglans nigra) Plantations

Intensively managed forest plantations often require fertilization to maintain site fertility and to improve growth and yield over successive rotations. We applied urea-based “enhanced-efficiency fertilizers” (EEF) containing 0.5 atom% 15N at a rate of 224 kg N ha−1 to soils under mid-rotation black walnut (Juglans nigra L.) plantations to track the fate of applied 15N within aboveground ecosystem components during the 12-month period after application. Treatments included Agrotain Ultra (urea coated with a urease inhibitor), Arborite EC (urea coated with water-soluble boron and phosphate), Agrium ESN (polymer-coated urea), uncoated urea, and an unfertilized control. Agrotain Ultra and Arborite EC increased N concentrations of competing vegetation within one month after fertilization, while neither Agrium ESN nor uncoated urea had any effect on competing vegetation N concentrations during the experiment. Agrotain Ultra and Arborite EC increased δ15N values in leaves of crop trees above those of controls at one and two months after fertilization, respectively. By contrast, Agrium ESN and uncoated urea had no effect on δ15N values in leaves of crop trees until three months after fertilization. Fertilizer N recovery (FNR) varied among ecosystem components, with competing vegetation acting as a sink for applied nutrients. There were no significant differences in FNR for all the urea-based EEF products compared to uncoated urea. Agrium ESN was the only EEF that exhibited controlled-release activity in this study, with other fertilizers behaving similarly to uncoated urea.

Performance of Urea-Based Fertilizers Associated With Elemental Sulfur or Polymers on Ammonia Volatilization

High N-NH3 losses are expected when conventional urea is applied to the soil surface. In order to reduce it, urea granules could be coated with different materials to decrease fertilizer dissolution rate or to stabilize N-NH4+ by acidification. In this study, we investigated the effect of a polymer-coated urea and powdered S0 added to urea, in the presence or absence of a S-oxidizing bacterium (Acidithiobacillus thiooxidans), on soil pH, SO42- availability, NH4+, and NH3 volatilization. Applying S0 before urea and the inoculation with bacteria have promoted the highest S0 oxidation rates. The greater decrease in soil pH occurred when S0 was applied before urea at a higher dose, which also decreased NH3 volatilization by 83% up to 4 days after urea application. However, the decrease in soil pH did not increase the concentration of NH4+, nor did it decrease the accumulated amount of volatilized NH3 over time. The inoculation of A. thiooxidans accelerates S0 oxidation process, but it was insufficient to counteract the H+ consumption by urea hydrolysis. Therefore, the S0 application with urea did not offer chemical protection against NH3 loss, but a physical barrier in the controlled-release urea had less dissolved urea in soil and reduced NH3 losses.

Modelling of N2O emissions from a maize crop after the application of enhanced-efficiency nitrogen fertilisers

ABSTRACT Emission of nitrous oxide (N2O) can be reduced using enhanced efficiency nitrogen fertilizers (EEFs), such as urease inhibitors and coating technologies. In this study, we evaluated the potential of EEFs to reduce N2O emissions in maize in a clayey Inceptisol subjected to no-till management under summer subtropical conditions, in southern Brazil. The EEF sources used included urea containing N-(n-butyl) thiophosphoric triamide (UR-NBPT), polymer-coated urea (UR-pol), in addition common urea (UR), nitrate (CN) and control treatment without the application of nitrogen fertilizer. N2O emissions were assessed using the static chamber method during one maize season and analyzed through non-linear regression, using a logistic model. The accumulated emission was 0.817, 0.613, 0.457 and 0.393 kg N2O ha−1, for CN, UR, UR-pol and UR-NBPT, respectively. The maximum daily emission of N2O did not vary between amidic forms, however for CN it occurred on the 4th day after application (DAA), while for urea forms it occurred on average at 5.3 DAA. The average N2O emission factor (FE-N2O) was 0.51%, approximately half the standard factor proposed by the Intergovernmental Panel on Climate Change (IPCC), which is 1%. The application of nitrogen increased the maize yield in relation to the control, but the sources of nitrogen did not differ, with an average yield of 10,455 kg ha−1. Based on our findings, the use of UR-NBPT and UR-pol in subtropical agroecosystems provides environmental benefits, by reducing N2O emissions in comparison with conventional nitrogen fertilizers (CN and UR), however, the EEFs did not offer agronomic advantages in maize yield.

Nitrogen Release from Polymer‐Coated Urea: Effect of Seasons and Growing Degree‐Days

Controlled‐release nitrogen (CRN) fertilizers are designed to gradually release N at rates that closely match the N demand by plants while potentially reducing N losses to the environment. Polymer‐coated urea (PCU) is the most widely used CRN. Actual N release patterns in the field are expected to be influenced by differences in weather conditions during different times of the year. Six field trials were carried out to estimate and model N release from PCUs during different times of the year (seasons) and to investigate a possible relationship that may exist between N release from PCU fertilizers and growing degree‐days and whether such a relationship could be used as a reliable predictor of N release under field conditions. Earn 1 CEU in Nutrient Management by reading this article and taking the quiz at www.certifiedcropadviser.org/education/classroom/classes/943.

Nitrous oxide emissions with enhanced efficiency and conventional urea fertilizers in winter wheat

Optimizing nitrogen fertilizer management can reduce nitrous oxide (N2O) emissions. This study tested if split applying enhanced efficiency fertilizers (EEFs) resulted in lower N2O emissions than applying equivalent rates of urea at planting. In semiarid southern Alberta, field trials were conducted during three years (planting to harvest) in rainfed winter wheat crops. Annual fertilizer rates ranged from 146 to 176 kg N ha−1. Fertilizer types were urea, and three EEFs (polymer-coated urea, urea with urease and nitrification inhibitors, and urea with a nitrification inhibitor). Each fertilizer type was applied three ways: 100% banded at planting, split applied 30% banded at planting and 70% broadcast in late fall, and split applied 30% banded at planting and 70% broadcast at Feekes growth stage 4 (GS4, post-tiller formation, wheat entering the greening up phase in the early spring). Nitrous oxide was measured using static chambers between sub-weekly and monthly from planting to harvest. Over three years, cumulative N2O emissions ranged from 0.16 to 1.32 kg N ha−1. This was equivalent to emissions factors between 0.009 and 0.688%. Cumulative N2O emissions and emissions factors did not differ between fertilizer types, but they were lower when fertilizer was split applied at GS4 compared to in late fall (P ≤ 0.10). Our study suggests that EEFs do not reduce N2O emissions from rainfed winter wheat crops, but a well-timed split application with a majority of fertilizer applied after winter can minimize N2O emissions.

Assessing the Potential of Polymer Coated Urea and Sulphur Fertilization on Growth, Physiology, Yield, Oil Contents and Nitrogen Use Efficiency of Sunflower Crop under Arid Environment

Nitrogen and sulphur are fundamental macronutrients for the production of sunflower crop. Nitrogen is required consistently in larger amounts for sunflower production while common urea has more losses due to high solubility. On the other hand, sulphur application increases oil contents and availability of other essential nutrients (N, P, and K). Therefore, combined application of polymer coated urea with sulphur fertilization might be a promising option which can increase achene yield, oil contents, and nitrogen use efficiency (NUE). However, no particular studies have been conducted to explore the main and interactive effects of polymer coated urea and sulphur fertilization on growth, physiology, yield, oil contents, and NUE under arid field conditions. Hence, the current field experiment consisted of two nitrogen fertilizers [polymer coated urea (PCU) and common urea (CU)] and three sulphur fertilizer rates [S0 (0), S1 (30) and S2 (60) kg ha−1)] in a split-plot arrangement under randomized complete block design (RCBD) during spring season of 2019 and 2020. Experimental results revealed that growth, physiology, yield, oil contents, and NUE of sunflower crop were significantly improved with the application of nitrogen fertilizers, sulphur fertilizer rates, and their interaction. Meanwhile, NUE, achene yield and oil contents were increased by 16.0–17.2%, 16.5–17.0%, and 2.96–3.19% respectively with the application of PCU compared with CU. Furthermore, NUE, achene yield and oil contents were also increased by 12.8–13.3%, 13.1–13.7%, and 10.7–10.9%, respectively, due to sulphur fertilization of 60 kg ha−1compared with no sulphur application. Similarly, NUE, achene yield, and oil contents were increased by 32.9–39.5%, 31.7–32.6%, and 13.1–13.2% respectively with the application of PCU in combination with sulphur fertilization of 60 kg ha−1compared with CU × S0, which also evidenced a clear and positive interaction between nitrogen and sulphur. Conclusively, PCU (130 kg ha−1) in combination with sulphur fertilization of 60 kg ha−1 is promising option for obtaining higher achene yield, oil contents, and NUE for sunflower crop under arid environment, and hence, it might be a good agronomic adaptation strategy for sustainable production of sunflower.

Optimal Blends of Controlled-Release Urea and Conventional Urea Improved Nitrogen Use Efficiency in Wheat and Maize with Reduced Nitrogen Application

Blending controlled-release urea (CRU) with conventional urea has the potential to be an effective option for improving nitrogen (N) use efficiency (NUE), although determination of optimal blends in combination with a reduced N application rate has not been well studied. A field experiment was conducted to compare the effects of CRU (a mixture of polymer-coated urea and urea with N ratios of 100:00, 75:25, and 50:50 at 144 kg N ha−1, hereafter denoted as CRU1, CRU2, and CRU3, respectively), urea at 180 (U1) and 144 kg N ha−1 (U2) and a control (no N fertilizer applied, CK) on grain yield, NUE, and economic benefits in a wheat–maize rotation system. The CRU treatments were one-time applied, while for the U treatments, fertilizer N was applied in a split application. The results suggest that a one-time application of CRU prior to sowing of both crops fulfilled the demand of crop plants for N across the entire growth period. Relative to U1, the CRU treatments achieved approximately the same grain yield and 4.7–26.6% greater NUE at 20% reduced N application. Moreover, under CRU2, the yield, NUE, and economic benefits were increased by 12.2%, 9.7%, and 19.1%, respectively, for wheat, and under CRU3, they were increased by 10.9%, 20.6%, and 17.3%, respectively, for maize, compared with the U2 treatment. These results demonstrate that a mixture of CRU and urea at a ratio of 75:25 for wheat and 50:50 for maize with a 20% reduction in N application rate can maintain productivity, while enhancing NUE in the North China Plain.

Effect of urea and polymer-coated urea on N content of soil and leaves of maize cultivated in Brazilian Cerrado

The development of technologies that provide rational and sustainable use of nitrogen fertilizers is among the priorities of agronomic research in 21st century. Therefore, the objective of this study was to evaluate the effects of conventional urea or polymer-coated urea (PCU) on soil mineral nitrogen (N) content, plant dry mass and leaf N content in maize (Zea mays L.), cultivated in two seasons (first and second-crop) and in two regions of the Brazilian Cerrado (Chapadão do Sul - MS and Selvíria - MS). The treatments consisted of the combination of two sources of N (conventional urea or polymer-coated urea) and five doses of N (0, 45, 90, 135 or 180 kg ha−1), in a randomized complete block design, with a 2 × 5 factorial scheme with four replications. The following parameters were evaluated: soil mineral N content (NH4+, NO3- and total mineral N), plant dry mass and leaf N content. Although the PCU did not change the NH4+, NO3- and total mineral N content in the soil, nor the dry mass of the plants, it provided, on average, higher N content in the leaves, when compared to CU. The increasing rates of N linearly increased the levels of NH4+, NO3- and total mineral N content in the soil, as well as the dry mass of the plants and the N content in the leaves, regardless of N source or study location.

Co-application of controlled-release urea and a superabsorbent polymer to improve nitrogen and water use in maize

ABSTRACT A field experiment consisted of two types of N fertilizer, controlled release urea (CRU) and normal urea (U), in combination with three SAP application rates (0, 45 and 90 kg ha−1) in a split-plot design was conducted in 2018 and 2019. The successive release of N from polymer-coated urea corresponded well to the N requirements of maize growth. The NO3 −-N and NH4 +-N contents in the 0–20 cm soil layer were enhanced at the jointing and 12 leaf collar stages, and the leaching of soil NO3 −-N was reduced by using CRU. The application of superabsorbent polymer (SAP) increased soil water stock, decreased evapotranspiration, and enhanced water use efficiency (WUE) and nitrogen use efficiency (NUE). The combined application of CRU and 90 kg ha−1 SAP achieved maximal maize yield, WUE, NUE, and net income values that were 0.8–32.9%, 0.2–37.4%, 4.1–13.1%, and 2.8–42.1%, respectively, higher than those of other treatments. These results demonstrate that the co-application of CRU and 90 kg ha−1 SAP is an effective practice that enhances the water and N utilization of maize and could potentially have wide application on the North China Plain.

Understanding soil water effects on nitrogen release from controlled‐release fertilizers

AbstractControlled‐release fertilizers (CRFs) have the potential to deliver crop production and environmental benefits through better control of applied nitrogen (N) in cropping systems. Whereas N release from CRFs can be impacted by several factors, there has been a widely held view that soil water has little effect on N release from polymer‐coated CRFs. Past research has often studied the soil water effect as a function of soil water content. This limits the transferability of results. In this study we measured N release from a polymer‐coated urea (PCU) and a polymer‐sulfur–coated urea (PSCU) using undisturbed soil cores at set matric potentials. Soil matric potential had a significant effect on N release from PCU. Release at −1,000 kPa was delayed by up to 30 d compared with −10 kPa. Optical stereo microscopy clarified that this was linked to differences in the rate of water absorption. Theoretical considerations demonstrate that these relatively large differences could not be explained by the effect of soil matric potential on vapor flow. It is possible that soil matric potential interacted with the properties of the coating to change its permeability or the involvement of liquid flow. The effect of soil water on N release from PSCU was less clear. The magnitude of the soil water effect is, therefore, product‐specific and dependent on coating properties. The soil matric potential provided a consistent description of release patterns between soils with contrasting soil water retention characteristics. Soil water effects should hence be studied as a function of soil matric potential.

Yield Response of Upland Rice as Influenced by Enhanced-Efficiency Nitrogen Fertilizers in the Brazilian Cerrado

Nitrogen (N) fertilizers have their use efficiency adversely affected by the rate and source of N. A two-year field experiment was conducted to examine the yield response of upland rice by using NBPT (urease inhibitor), PCU (polymer-coated urea) and uncoated urea under different N application rates. It was hypothesized that either NPBT or PCU may result in increased yield components of upland rice when compared to conventional urea. The experiment was set up in a randomized block design in a 3 × 4 + 1 factorial scheme, with four replicates. Treatments comprised three sources (conventional uncoated urea, NBPT-treated urea, and polymer-coated urea) and four rates (30, 60, 90 and 120 kg ha-1) of N, in addition to a control treatment (no fertilizer application). Nitrogen fertilizers were applied in two split doses: 50% at the seedling stage, and 50% at the tillering stage (~80 days after planting). The results revealed that the use of enhanced-efficiency N sources increased the productivity and plant height of upland rice crop when compared to conventional urea. As compared to when it is untreated or polymner-coated, treating urea with NBPT resulted in increased 100-grain weight.

Three-dimensional dynamics of nitrogen from banded enhanced efficiency fertilizers

A range of enhanced efficiency fertilizers (EEFs) have been developed in response to widespread recognition of poor nitrogen (N) use efficiency (NUE) in agriculture; however, their effective utilization is not properly understood when applied in sub-surface bands. This study quantified soil chemical changes and the distribution of N species that arose from sub-surface banding of urea, a controlled release polymer-coated urea (PCU) and urea coated with either nitrification inhibitors (NIs) or a urease inhibitor (UI), over 71 days in a field trial. Banding NIs extended the duration of nitrification inhibition for up to 50 days longer than banded urea, although the duration of NI-conferred inhibition was dependant on the rate of NI-urea application. The UI preserved urea-N at a concentration which was 16-fold higher cf. standard urea over 7 days, but no urea-N was detected after 21 days. This suggests that the NUE benefits of UIs are transient when applied in sub-surface bands. Slow release of urea-N from banded PCU resulted in lower concentrations of N in the soil solution. This reduced N dispersal by ca. 50 mm cf. urea, resulting in a N-enriched zone which was considerably smaller. Relatively benign chemical conditions around PCU bands enabled rates of nitrification (NH4–N:NO3–N ratio of 46%) which were similar to urea. Collectively, these results demonstrate the relative efficacy and risks of the different EEF technologies, when applied in fertilizer bands. This knowledge supports the effective utilization of band-applied EEFs for improved NUE in agricultural systems.

Effect of controlled-release fertilizers on leaf characteristics, grain yield, and nitrogen use efficiency of machine-transplanted rice in southwest China

ABSTRACT Controlled-release fertilizers (CRFs) are known to improve grain yield and N-use efficiency (NUE) without intensive labor input in crop production. Here, we report field experiments conducted to investigate the effects of different CRFs [polymer coated complex fertilizer (PCCF), polymer-coated urea (PCU), and sulfur-coated urea (SCU)] on leaf characteristics, biomass, N uptake, grain yield, and NUE of machine-transplanted rice in Sichuan, China, from 2016 to 2017. Grain yield, N recovery efficiency (NRE), N agronomic efficiency (NAE), and N partial factor productivity (PFP) were positively correlated with improved leaf characteristics, dry matter accumulation, and N uptake. Total leaf area, leaf area, chlorophyll content, and net photosynthetic rate of the top three leaves, maximum accumulation rate of dry matter, and N accumulation, as well as panicles per m2 and spikelets per panicle were increased by CRFs, thereby increasing both grain yield and NUE. Furthermore, compared to PCCF and SCU, PCU promoted relatively higher leaf photosynthetic potential of the top three leaves, which is closely related to increased biomass and N uptake. These effects ultimately improved grain yield, NRE, NAE, and PFP under the PCU treatment. Thus, PCU is effective in enhancing grain yield and NUE in machine-transplanted rice.

Growing season nitrate leaching as affected by nitrogen management in irrigated potato production

AbstractNitrate leaching from potato (Solanum tuberosum L.) production is of great concern because of its potential effects on water resources. Suction lysimeters were used in combination with a one‐dimensional flow model to quantify NO3–N leaching under irrigated potato produced on sandy soils near Québec City, QC, Canada. The 3‐yr (2010−2012) study compared a single application of polymer‐coated urea (PCU) and split‐applied soluble N fertilizers (ammonium nitrate, AN; ammonium sulfate, AS) at three N rates (120, 200, and 280 kg N ha−1) in addition to an unfertilized control. Fertilizer N application increased total seasonal NO3–N leaching. A single application of PCU increased total seasonal NO3–N leaching in 2011 compared with AN and AS, which was attributed to a greater soil NO3–N concentration under the PCU treatment in combination with increased rainfall during the tuber bulking phase (60−90 d after planting). Total seasonal NO3–N leaching in 2012 was reduced with PCU and AS compared with AN, which was attributed to reduced soil NO3–N concentrations between planting and hilling when rainfall was high. Regardless of the fertilizer N source, NO3–N leaching was primarily driven by precipitation, as leaching occurred when elevated soil NO3–N concentrations coincided with excess water in the soil. The results suggest that a single application of PCU is an effective strategy for reducing NO3–N leaching in years when there is significant rainfall during the period between planting and hilling.

Sources and management of nitrogen before or after irrigation on the winter wheat and bean production

Studies that demonstrate the effects of sources of nitrogen (N) applied before or after irrigation on the yield of winter crops are limited in literature. In this sense, the objective of this study was to compare the effect of sources of N applied immediately before or after 13 mm irrigation of wheat and bean winter crops. It was used a randomized complete block design, with 4 replicates, in a 5 × 2 + 1 factorial scheme, and 11 treatments consisted of five N sources: urea, polymer-coated urea, urea + ammonium sulfate, ammonium sulfate, and ammonium nitrate and a control treatment (without N fertilization). For wheat, although ammonium nitrate provided great N content in the leaves, the grain yield was lower due to the lodging of the plants; since the application of N either before or after irrigation did not influence the grain yield. Regarding the bean, N fertilization increased productivity, but there were no differences among N sources and, despite the greater N content in the leaves observed with the N supply before irrigation the greatest grain yield was observed when N was applied after the irrigation.