Granular Urea Research Articles

Effect of granular urea on the properties of self-consolidating concrete incorporating untreated rice husk ash: Flowability, compressive strength and temperature rise

This article presents the effect of granular urea on the flowability, compressive strength and temperature rise of self-consolidating concrete (SCC) that includes untreated rice husk ash (RHA) with granular urea (urea) in its composition. The slump flow test was used to assess the horizontal free flow of the concrete in the absence of obstructions. Powder materials were used in the amounts of 450, 550, and 650 kg/m3. Ordinary Portland cement (OPC) was replaced with RHA at a percentage replacement of 20%wt. The granular urea-powder materials (OPC + RHA + urea) ratios were augmented by 0, 5, 10, and 20%wt of the powder materials. Moreover, the water-powder materials ratio (w/p) was 30%. The unit weight, setting time, slump flow and loss, J-ring flow, V-funnel, temperature rise, and compressive strength of the samples were measured for up to 120 days. The results show that when urea is mixed with SCC, the temperature rises less, which has the effect of producing high flowability without segregation when the appropriate percentage of urea is also used. However, this composition also produces SCC with a longer setting time and lower compressive strength than those of conventional SCC. A longer setting time can be beneficial when it is necessary to delay this process in practice. It should be noted, too, that the effect of urea on the compressive strength depends on the concrete age—that is, for a concrete age of 91 days, the effect is very similar to that achieved when only water (as opposed to both water and urea) is included in the mixture. These findings suggest that adding granular urea and RHA to SCC can reduce the concrete temperature and improve the flowability, especially in mass concrete construction or in hot tropical areas.

Nitrogen fertilization of warm‐season turfgrasses irrigated from varying irrigation systems: 2. Carbohydrate and protein content

AbstractA 3‐year study was conducted at New Mexico State University in Las Cruces, NM, to investigate whether different fertilization treatments affect the carbohydrate and protein content in two warm‐season grasses grown using water conservation strategies such as non‐potable saline irrigation water and a subsurface irrigation system. “Princess 77” bermudagrass (Cynodon dactylon L.) and “Sea Spray” seashore paspalum (Paspalum vaginatum O. Swartz) were irrigated with either potable (electrical conductivity [EC] = 0.6 dS m−1) or saline (EC = 3.1 dS m−1) water from either an overhead or a subsurface drip irrigation system. Four different fertilizers were used in this study: liquid slow release, granular slow release, granular urea and urea liquid, at two rates: 10 and 20 g N m−2 yr−1 for “Sea Spray” and 20 and 30 g N m−2 yr−1 for “Princess 77.” Carbohydrate (sucrose, starch, total soluble carbohydrates and total non‐structural carbohydrates) and protein content of the grasses were measured, and their effect on spring green‐up was determined. The total carbohydrate content within the stolons and rhizomes was found to be closely associated with speed of spring green‐up, resulting in R2 values ranging from 0.36 to 0.76. The relationship between green‐up and carbohydrate content was similar for both grasses. Fertilizer treatment did not affect carbohydrate content in either grass under either irrigation system. Further analysis revealed that carbohydrate content in February was the best determinant for spring green‐up. Other sampling months also showed a significant correlation with spring green‐up, but with lower R2 values.

Nitrogen fertilization of warm‐season turfgrasses irrigated with saline water from varying irrigation systems. 1. Quality, spring green‐up and fall colour retention

AbstractA 3‐year study was conducted at New Mexico State University in Las Cruces, NM, to investigate the effects of different fertilization treatments on turf performance when water conservation strategies are applied. These strategies include the use of non‐potable saline irrigation water and the use of efficient subsurface irrigation systems. Two low water use warm‐season grasses, “Princess 77” bermudagrass (Cynodon dactylon L.) and “Sea Spray” seashore paspalum (Paspalum vaginatum O. Swartz), were irrigated with either potable [Electrical Conductivity (EC) = 0.6 dS/m] or saline (EC = 3.1 dS/m) water from either an overhead or a subsurface drip irrigation (SDI) system. Four different fertilizers, liquid slow release, granular slow release, granular urea and liquid urea, were applied at two rates: 10 and 20 g N m−2 year−1 for “Sea Spray” and 20 and 30 g N m−2 year−1 for “Princess 77.” Spring green‐up, summer quality and fall colour retention were determined using digital image analysis, visual quality ratings and normalized difference vegetation index. Generally, subsurface drip‐irrigated grasses were slower to green‐up than overhead irrigated ones. “Sea Spray” irrigated from the SDI system took 18, 28 and 15 days longer to reach 80% green cover in 2010, 2011 and 2012, respectively, than their sprinkler‐irrigated counterparts. The combination of “Princess 77” and overhead irrigation reached 80% green cover 35 (in 2010), 34 (in 2011) and 12 (in 2012) days faster than SDI‐irrigated “Princess 77.” Fertilization rate and type had no effect on summer turfgrass quality of “Princess 77” irrigated from a sprinkler system throughout the research period reaching ratings of greater than 7 during all 3 years. Similar results were observed for “Princess 77” irrigated from a SDI system during 2010 and 2011. Summer quality of sprinkler‐irrigated “Sea Spray” was negatively affected by liquid fertilization. During two of three summers, visual quality of plots fertilized with either liquid slow release or liquid urea was lower than “Sea Spray” fertilized with granular fertilizer. Further research is needed to investigate the effect of fertilization on bermudagrass and seashore paspalum over a wider nitrogen range including both granular and foliar products.

Optimize nitrogen fertilization location in root-growing zone to increase grain yield and nitrogen use efficiency of transplanted rice in subtropical China

The optimized nitrogen fertilization location differs in different rice-growing regions. We optimized nitrogen deep-point application in root-growing zone (NARZ) for transplanted rice in subtropical China. Field plot experiments were conducted over two years (2014–2015) in a double-rice cropping system to evaluate the effects of nitrogen (N) fertilizer location on grain yield and N use efficiency (NUE). Four different nitrogen deep-point application methods (DN) were compared with traditional broadcast application (BN) using granular urea. The results showed that grain yield, recovery efficiency of N (REN), agronomic efficiency of N (AEN), and partial factor productivity of N (PFPN) significantly increased 10.3–63.4, 13.7–56.7, 24.7–201.9 and 10.2–63.4%, respectively, in DN treatment compared to BN, respectively. We also find that DN treatments increased grain yield as well as grain N content, and thus grain quality, in comparison with conventional BN treatment. Correlation analysis indicated that significant improvement in grain yield and NUE mainly resulted from increases in productive panicle number and grain N content. In our proposed NARZ method, granular urea should be placed 0 to 5 cm around the rice seeding at a 12-cm depth druing rice transplanting. In NARZ, balanced application of N, P and K further improved grain yield and NUE over treatments with a single N deep-point application. High N uptake by the rice plant did not cause significant soil fertility depletion, demonstrating that this method could guarantee sustainable rice production.

Ammonia and carbon dioxide emissions by stabilized conventional nitrogen fertilizers and controlled release in corn crop

ABSTRACT The market of stabilized, slow and controlled release nitrogen (N) fertilizers represents 1% of the world fertilizer consumption. On the other hand, the increase in availability, innovation and application of these technologies could lead to the improvement of N use efficiency in agroecossystems and to the reduction of environmental impacts. The objective of this study was to quantify agronomic efficiency relative index, ammonia volatilization, and CO2 emissions from conventional, stabilized and controlled release N fertilizers in corn summer crop. The experiment was carried out in a corn crop area located in Lavras, state of Minas Gerais, Brazil, without irrigation. All treatments were applied in topdressing at rate of 150 kg ha-1 N. N-NH3 losses from N fertilizers were: Granular urea (39% of the applied N ) = prilled urea (38%) > urea coated with 16% S0 (32%) = blend of urea + 7.9% S0 + polymers + conventional urea (32%) > prilled urea incorporated at 0.02 m depth (24%) > urea + 530 mg kg-1 of NBPT (8%) = Hydrolyzed leather (9%) > urea + thermoplastic resin (3%) = ammonium sulfate (1%) = ammonium nitrate (0.7%). Thermoplastic resin coated urea, ammonium nitrate and ammonium sulfate presented low values of cumulative CO2 emissions in corn crop. On the other hand, hydrolyzed leather promoted greater C-CO2 emission, when compared with other nitrogen fertilizers.

Producing Slow Release Granular Urea by Coating with Starch/Poly Vinyl Alcohol in Fluid Bed Spraying

Producing Slow Release Granular Urea by Coating with Starch/Poly Vinyl Alcohol in Fluid Bed Spraying

Cattle fever tick, Rhipicephalus (Boophilus) microplus (Acari: Ixodidae): Potential control on pastures by the application of urea fertilizer

The southern cattle fever tick, Rhipicephalus (Boophilus) microplus, spends as much as 80–90% of its life cycle as a larva questing for a host. Standard control methods are limited to on-host applications, leaving a need for methods directed at the pasture infesting stages. Reports from Brazil indicate that pasture fertilization can reduce tick numbers. Granular urea was tested using standard pesticide efficacy methods in both the laboratory and field trials to determine if there was a significant impact on adult reproduction and larval survival. Under the conditions of this present study, there was no detectable effect on either female adults or larval stages. Ammonification in the soil may be a key factor limiting the impact of fertilizer treatments.

Greenhouse Gas Emissions from an Irrigated Dairy Forage Rotation as Influenced by Fertilizer and Manure Applications

Core Ideas Urea formulated with urease and nitrification inhibitors can reduce N2O emissions. Nitrous oxide‐N emission losses as a percentage of total N applied were ≤0.21%. Timing of manure application did not affect N2O, CO2, and CH4 fluxes. Soil was a CH4 sink and emissions were not influenced by N source. Information is needed regarding the effect of N source on greenhouse gas (GHG) emissions from irrigated semiarid agricultural soils. We report N2O, CO2, and CH4 emissions from a silage corn (Zea mays L.) (2013)–barley (Hordeum vulgare L.) (2014)–alfalfa (Medicago sativa L.) (2015) rotation under conventional tillage and sprinkler irrigation. We evaluated the effectiveness of an enhanced‐efficiency fertilizer (SuperU, a stabilized granular urea with urease and nitrification inhibitors) to reduce N2O emissions compared with granular urea and to determine GHG emissions from fall‐applied dairy manure or composted dairy manure and spring‐applied dairy manure. Nitrogen was applied during the first 2 yr of the study. SuperU plots emitted 53% less N2O than urea with corn, whereas no emission reductions occurred in 2014 with barley. The N2O‐N emission losses as a percentage of total N applied were 0.21 and 0.04% for urea and SuperU in 2013, respectively, with losses of 0.05% from both urea fertilizers in 2014. On average, N2O fluxes from fall and spring manure were statistically similar and greater than the other N treatments in 2014 and a lasting manure treatment effect on emissions occurred under alfalfa. Carbon dioxide fluxes were greatest from fall‐ and spring‐applied manure during the first 2 yr. Methane fluxes were negative, indicating microbial oxidation, and no differences occurred among the treatments. Corn, barley, and alfalfa yields were similar among all N treatments. This work demonstrates that SuperU can reduce N2O emissions from irrigated cropping systems in the semiarid western United States without affecting yields.

Ammonia Volatilization from Urea Treated with NBPT and Two Nitrification Inhibitors

Core Ideas A comparison of ammonia volatilization from granular urea treated with two commercially available nitrification inhibitors and the interaction with the urease inhibitor, NBPT. Nitrification inhibitors increased ammonia volatilization from surface‐applied granular urea compared to untreated urea. When treating urea with nitrification inhibitors, a urease inhibitor should be applied to reduce ammonia volatilization losses. Soil type specific recommendations may be needed when applying nitrification/urease inhibitors to urea in order to maximize N use efficiency. Nitrification inhibitors reduce the rate of transformation of ammonium to nitrate, which may increase ammonia volatilization from urea‐based N fertilizers. The objective of this study was to quantify ammonia volatilization from surface‐applied granular urea treated with combinations of NBPT and the nitrification inhibitors, DCD and nitrapyrin, under controlled laboratory conditions for three soils. Nine laboratory trials evaluated select combinations of application rates for NBPT, DCD, and nitrapyrin‐treated urea. Trials were conducted on three soils selected for differences in pH, organic matter, and cation exchange capacity (CEC). Cumulative N loss as ammonia from untreated granular urea was 40.1, 44.5, and 38.2% of applied N for the Raub, Wheeling, and Pella soils, respectively. When the urease inhibitor, NBPT was applied alone at 900 mg NBPT kg−1 urea, N loss through volatilization was reduced 48.5, 43.3, and 77.9% for the Raub, Wheeling and Pella soil types, respectively. Of the soil tested, cation exchange, texture, and organic matter had the greatest impact on the rate and cumulative ammonia loss from surface‐applied untreated urea and urea treated with the urease/nitrification inhibitors. Nitrification inhibitors prevented the conversion of ammonium to nitrate by DCD and nitrapyrin, increasing ammonia losses of N in five out of six trials compared to untreated urea. When using nitrification inhibitors with surface‐applied urea, ammonia losses were decreased with the application of NBPT as well.

Growth performance and nitrogen uptake of Hibiscus cannabinus as influenced by controlled-release urea fertilizers on BRIS (Beach Ridges Interspersed with Swales) soil

A field trial was conducted to oversee the effects of controlled release urea (CRU) fertilizers on kenaf grown on the BRIS soil. Three types of formulated CRU were tested: (1) Meister-20, (2) CRU Duration Type V and (3) Uber-10 along with typical granular urea which acts as control set. Two rates of fertilizer at 300 and 600 kg N/ha were applied accordingly. Results demonstrated that the 300 kg N/ha fertilization was sufficient to ensure sufficient growth for sustainable kenaf production. The best CRU fertilizers, which were able to support the growth and nitrogen uptake of tested crop on the BRIS soil were: Meister-20> Duration Type V> Uber-10, respectively.

Utilization of waste lignin to prepare controlled-slow release urea

The present work reports an economically attractive improvement in the area of producing particulate slow release nitrogen fertilizer using lignin as a waste effluent of pulp and paper manufacturing process. An improved coating of modified lignin was applied on the surfaces of the individual urea particles. The Kraft and Sulfite black liquors obtained from two different paper pulping units and were used as sources of sulfate and sulfite lignin, respectively. Chemical modification of extracted lignin was performed through acetylation reaction by acetic acid/sodium metabisulfite to increase its hydrophobicity character. In a separate experiment, a thin layer of synthesized acetylated lignin was coated on granular urea by fluidized-bed technique. The nitrogen release of synthesized fertilizer in the water and soil was examined by the Kjeldahl method. The analysis of FTIR spectra indicated the changes in the functional groups of acetylated lignin. Petrographic photography and scanning electron microscopy (SEM) analyses demonstrated a uniform and homogeneous covering of the urea surface. The 7 day nitrogen release rate of urea coated by acetylated lignin in soil was obtained 36.3 and 45.3 % for Kraft and Sulfite lignin, respectively, whereas this value was 59 % for sulfur coated urea. Using industrial wastewater as source of lignin gives satisfactory results for industrial applications and yields a quality green fertilizer product with reduced operation difficulties while considerably preserving the environment.

Effect of post-sowing nitrogen management on co-limitation of nitrogen and water in canola and mustard

In rainfed Mediterranean environments crop yields are limited by nitrogen (N) and water. The concept of water and N co-limitation has been used to describe how these competing resources are allocated during growth, it has been proposed that growth is optimum when water and N are equally limiting. All the published work so far on water and N co-limitation has been done in cereals using single applications of fixed amounts of N. However, delayed and split applications of N at key phenological growth stages can improve N use efficiency and alter the severity of N and water stress during the growth of the crop. The aim of the work reported here was to assess water and N co-limitation in the indeterminate crops canola (Brassica napus) and mustard (B. juncea) under different post-sowing N treatments. Four field experiments were conducted over three years with different cultivars of canola and mustard, under different water regimes, and grown with three N rates (0, 100 and 200kgNha−1 as granular urea) applied at different phenological growth stages. The results suggested that yield gaps (Yg; the difference between actual and attainable yield) increased as total stress from water and N (TWN) and the maximum of the two stresses (MWN) increased and declined as the degree of water-N co-limitation increased, whether based on total stress (CTWN) or maximum stress (CMWN). However, seasonal and genotypic variation in the Yg reduction and improvement in water use efficiency (WUE) with the degree of co-limitation were observed for CTWN. Application of N improved the CTWN without having the effect of split N application timing. No relationship was found between N use efficiency for seed yield (NUESY) of canola and mustard and co-limitation indices, which may be due to low N uptake efficiency during the pre-flowering period and low physiological efficiency during the post – flowering period. This study provides the first empirical evidence that yield of canola and mustard is co-limited by water and N under post-sowing N application with seasonal and genotypic variation in response to CTWN. Future studies need to focus on the interaction of pre and post-flowering water and N stresses and their effect on CTWN in devising crop management tools for this environment.

Field performance of BARI urea super granule applicator

Field performance of BARI Urea Super Granule (USG) applicator was evaluated on BARI research stations (Gazipur, Pabna, and Barisal) and farmer’s field (Pabna, Barisal, Magura,Narshingdi,Jhenadah, Sirajgang, Rajbari and Jhalkathi) during the boro season of 2012-13. The applicator was tested with four treatments- application of USG by hand (165 kg/ha), application of USG by BARI USG applicator (165 kg/ha), application of prilled urea at USG rate (165 kg/ha) and application of prilled urea at farmers practice. In the farmer’s field, USG applicators were evaluated with the traditional broadcasting of granular urea. Similar yield of rice was obtained from machine and hand application of USG in all locations. Higher yield of rice was obtained from USG than granular urea. During field test, average field capacity and efficiency of the applicator were 0.138 ha/h and 81%, respectively. Considering custom hiring, the net income per year was Tk. 71750 and the payback period was 3 days. The price of the applicator is Tk. 3500.Bangladesh J. Agril. Res. 41(1): 103-113, March 2016

Bacterial communities of an agricultural soil amended with solid pig and dairy manures, and urea fertilizer

Agricultural management practices impact the bacterial diversity of soil but it is unclear how bacterial communities respond to different nutrient sources. This study examined the impacts of manure and granular urea N additions on the diversity and composition of soil bacterial communities. Bacterial communities in an annual cropping system were examined in the short-term (within season) and medium-term (after three successive annual additions) following manure and urea N applications. Soil samples were collected from an experimental field site in fall 2007 prior to imposition of treatments, and post-planting, mid-season, and post-harvest in 2010 following three successive annual applications. Treatments included: solid pig manure (SPM), solid dairy manure (SDM), granular urea N-fertilizer, and unamended control. Pyrosequencing was used to characterize bacterial communities in soil and the manure added. Psychrobacter was the most abundant genus in both SPM and SDM, however it was not detected in soil. Solid pig manure treatments had greater diversity than urea and control treatments and diversity was greatest at post-harvest in fall than post-planting in spring. In 2010, the relative abundances of many bacterial taxa were affected by treatment and sample season but not their interaction. Where Actinobacteria, Firmicutes, Gemmatimonadetes and Bacteroidetes were significantly different for the urea and manure treatments, Proteobacteria declined in relative abundance over the growing season. Communities of manure and urea treated soils converged with progression of growing season. Redundancy analysis showed SO4−2, NO3− and NH4+ concentrations were significant, explaining 44% of the variation observed in bacterial communities across treatments and sample seasons. In conclusion, bacterial diversity increased with manure treatment and with progression of the growing season, the former being not as a result of introduction of taxa from the manure but likely from nutritional resources provided in the organic amendments.

Utilization of Urea Super Granule in Raised Bed Versus Prilled Urea in Conventional Flat Method for Transplanted Aman Rice (Oryza Sativa)

Bed planting with urea super granule (USG) application of rice production systems is very new and research on it is still at an introductory phase. Impact of granular urea application on growth and yield of transplanted aman rice as well as evaluation of water and fertilizer use efficiency of rice-fallow-rice cropping system was investigated under raised bed cultivation method. Result showed that the USG in bed planting method increased grain yield of transplanted aman rice up to 12.32% over prilled urea (PU) broadcasting in conventional method. The USG application in bed planting method increased the number of panicle m-2, number of grains panicle-1 and 1000-grains weight of rice than the PU in conventional method. Sterility percentage and weed infestation were lower at USG application in bed planting method than the PU in conventional method. Forty percent irrigation water and time for application could be saved through the USG in bed planting than the PU broadcasting in conventional method. Water use efficiency for grain and biomass production was higher by the USG application in bed planting than the PU broadcasting in conventional method. Likewise, agronomic efficiency of the USG in bed planting was higher than the PU broadcasting in conventional method. This study concluded that the USG in bed planting method is a new approach to get better fertilizer and water use efficiency as well as higher yield compared to the existing agronomic practice in the world.

Effect of Coating Thickness on Release Characteristics of Controlled Release Urea Produced in Fluidized Bed Using Waterborne Starch Biopolymer as Coating Material

Loss of granular urea through leaching, ammonia volatilization and denitrification can be overcome by the application of controlled release urea. Sulfur and organic polymers have been used as controlled-release coating materials but they have limitations of high cost, process complexity and environmental issues. Waterborne starch biopolymer modified with polyvinyl alcohol is a cheap, biodegradable and environmentally friendly coating material and is used for the production of controlled release urea in a fluidized bed. The effect of coating thickness is investigated on release time and diffusion coefficient of urea release in distilled water. Release time increases with increase in coating thickness. The diffusion coefficient of nutrient release decreases with increase in coating thickness. However, coating imperfections and porous coating in some cases produced the opposite results both for release time and diffusion coefficient. It is concluded that a significant coating thickness in addition to good uniformity of thickness and film integrity can produce promising controlled release characteristics.

Impacts of Enhanced-Efficiency Nitrogen Fertilizers on Greenhouse Gas Emissions in a Coastal Plain Soil under Cotton.

Enhanced-efficiency N fertilizers (EENFs) have the potential to increase crop yield while decreasing soil N loss. However, the effect of EENFs on greenhouse gas (GHG) emissions from different agricultural systems is not well understood. Thus, studies from a variety of locations and cropping systems are needed to evaluate their impact. An experiment was initiated on a Coastal Plain soil under cotton ( L.) production for comparing EENFs to traditional sources. Nitrogen sources included urea, ammonia sulfate (AS), urea-ammonia sulfate (UAS), controlled-release, polymer-coated urea (Environmental Smart Nitrogen [ESN]), stabilized granular urea (SuperU), poultry litter (PL), poultry litter plus AgrotainPlus (PLA), and an unfertilized control. Carbon dioxide (CO), nitrous oxide (NO), and methane (CH) fluxes were monitored regularly after fertilization through harvest from 2009 to 2011 using a closed-chamber method. Poultry litter and PLA had higher CO flux than other N treatments, while ESN and SU were generally lowest following fertilization. Nitrous oxide fluxes were highly variable and rarely affected by N treatments; PL and PLA were higher but only during the few samplings in 2010 and 2011. Methane fluxes were higher in 2009 (wet year) than 2010 or 2011, and N treatments had minimal impact. Global warming potential (GWP), calculated from cumulative GHG fluxes, was highest with PL and PLA and lowest for control, UAS, ESN, and SU. Results suggest that PL application to cotton increases GHG flux, but GHG flux reductions from EENFs were infrequently different from standard inorganic fertilizers, suggesting their higher cost may render them presently impractical.

Performance of BARI developed USG applicator in boro rice field

A trial was conducted at the FSRD site, Elenga and MLT site, Ghatail, Tangail during 2011-12 and 2012-13 to test the performance of the BARI developed USG applicator in boro rice and to find out the economic performance of the USG applicator in the farmers’ field. The BARI developed USG applicator was tested against the USG application by hand and the conventional method of granular urea application. The average higher grain yield (7.05 t ha-1 and 7.07 t ha-1) of two years were obtained from the plot of USG application with BARI applicator in the both locations, respectively The highest gross return (120410 Tk. ha-1 & 20290 Tk. ha-1) and gross margin (64346 Tk. ha-1 and 62164 Tk. ha-1) during 1011-12 and 2012-13 were obtained from the plots treated with USG by BARI applicator at the FSRD site Elenga and MLT site Ghatail, respectively. Field efficiency of BARI USG applicator and hand application was 0.12 hah-1 and 0.027 hah-1, respectively. BARI USG applicator saved time 77.65% compared to that of hand application of USG in boro rice field. It also saved labor cost against the USG application by hand and reduces 33% urea over the granular urea application in conventional method.Bangladesh Agron. J. 2014, 17(2): 77-81

Influence of Slow Release Urea Fertilizer on Growth, Yield and N Uptake on Maize under Calcareous Soil Conditions

Heavy N losses are always associated with urea fertilizer application therefore, improving its efficiency is crucial to reduce economic and environmental losses related with its application. The viable approach to reduce the N losses from the surface applied urea is to coat it with sulfur, urease inhibitor and other biodegradable materials. Field experiment were conducted to investigate the impact of super and urease coated urea on growth, yield, yield components and N uptake in maize under calcareous soil conditions of Khyber Pakhtunkhwa (KPK) during 2011-12. The experiment was conducted in a randomized complete block design (RCBD) with 4 replications each. Urea coated with urease (agrotain) and nitrification inhibitors (super urea) were applied at 90 kg and 120 kg N ha -1 in 2 or 3 splits. The fertilizer treatments were applied at sowing, after 30 and 60 days of sowing (DAS), respectively. The results showed that inhibitors treated urea significantly improved the growth, yield and yield components of maize crop over granular urea and control treatment. Super urea shows its superiority over agrotain in terms of increased yield. Inhibitors application at 90 kg N ha -1 has pronounced effect than 120 kg N ha -1 . Three splits of coated urea performed better than 2 splits. The highest improvement of 38.06% in grain yield and 45.13% in total N uptake was obtained in treatment receiving super urea at 90 kg N ha -1 compared with granular urea at 90 kg N ha -1 . Agrotain treated urea at 90 kg N ha -1 gave the next highest improvement of 30.55% in grain yield and 38.87% in total N uptake than granular urea and control plots at 90 kg N ha -1 . These results suggest that the combined use of urease + nitrification inhibitors

A comparison under grazing of pasture production, pasture N content and soil mineral N levels between granular urea and ONEsystem® on two contrasting dairy farms in New Zealand

Field trials under grazing on two contrasting dairy farms in mid-Canterbury (Site C) on a stony silt loam under irrigation, and in rain-fed central Waikato (Site W) on a volcanic ash-derived soil, compared standard granular urea (4-5 mm diameter granules) with ONEsystem®. This uses prilled urea (0.8-2.8 mm diameter prills), passed through a fine water spray (50 litres/ha) that contains the urease inhibitor nbpt (2 gm nbpt/kg N) during application. A nil N control and three rates of each fertiliser were applied to 12 × 25 m plots on four occasions after rotational grazing during spring/early summer 2014. ONEsystem® resulted in extra dry matter (EDM) to N applied compared with granular urea at Site C. At Site W, the initial advantage to ONEsystem® in Period 1 (early spring) was not maintained. To produce EDM of 1250 (±750) kg/ha required 120 and 126 kg N/ha as granular urea at Sites C and W, respectively (giving EDM factors of 10.4 and 9.9 (± 2) kgDM/ kgN applied respectively). This compares with 50 and 74 kg N/ha required with ONEsystem® for higher EDM factors of 24 and 17 (± 5) kg DM/ kg N. Pasture N concentrations were higher at Site C following ONEsystem® application, and total N uptake was increased 3-fold compared to granular urea. At Site W, increases in EDM with ONEsystem® only occurred in the first period. The results of this study have implications for both the economic and environmental efficiency of fertiliser urea use on grazed pastures. Keywords: ONEsystem®, prilled urea, nbpt, granular urea, N efficiency, pasture, N uptake