Liquid Urea Research Articles

Site‐Specific Irrigation and Nitrogen Management for Cotton Production in the Southern High Plains

Upland cotton (Gossypium hirsutum L.) production in the Southern High Plains is usually limited by water and N. The most prevalent means of irrigation in this region is center‐pivot, and injection and/or ground application of liquid urea ammonium nitrate is the most common N management. The declining Ogallala aquifer has led to interest in variable‐rate or variable‐speed irrigation using center pivots. Variability in yields, soil properties, and elevation within the typical 48‐ha center‐pivot fields suggests that N fertilizer use efficiency might be improved by variable‐rate N applications. We conducted a 3‐yr experiment on a 14‐ha area within a 48‐ha center pivot in a terminated‐rye (Secale cereale L.) conservation tillage cotton system. The objectives were to assess lint yield response to irrigation level for different landscape positions and to compare the effects of variable‐rate N, blanket‐rate N, and zero N on lint yields at varying irrigation levels and landscape positions. Lint yield response to irrigation was linear in 2002 and 2003. Increased rainfall in 2004 limited irrigation response. Contrary to our hypothesis, cotton lint yield response to irrigation was not less in the bottomslope than in the sideslopes. Nitrogen fertilizer resulted in greater lint yields in all 3 yr, but the magnitude of the response was less than that of irrigation in 2002 and 2003. Nitrogen response did not interact with landscape position or with irrigation rate. Variable‐rate N resulted in more consistent lint yield response than did blanket‐rate N in all years. However, when the costs of implementing variable‐rate management were considered, the dollar returns to N fertilizer were favorable for variable‐rate fertilization in only 1 of 3 yr.

Enzymatic biosensors for artificial kidney

We report here, for the first time, the tailoring of enzymatic membranes (enzyme origin, type of photocurable polymer, formulation of the membrane, conditions of deposition) in order to obtain EnFETs with specifications adapted to dialysis monitoring through direct detection of creatinine and urea in plasmatic liquid. The working characteristics of the EnFETs based on such an approach were studied in model buffer solutions. For urea, the use of a recombinant enzyme from E-coli allows to extend the dynamic range up to 80 mM. In the case of creatinine the biosensors are operational in concentrations ranging from 20 to 1000muM.

Physical Characteristics of Miscanthus Composts Compared to Peat and Wood Fiber Growth Substrates

The physical parameters of four different Elephant grass “Miscanthus ogiformis” ‘Giganteus’ composts and four of the most used types of peat products in Denmark, along with a wood fiber growing medium (Culti), were compared to determine possible physical differences, and to test whether compost could be used as an alternative substrate to peat. The Miscanthus straw was composted with three different N sources: ammonium sulfate, liquid pig manure and urea plus tap water (as a control). Compared to peats, the composts tested had low total bulk density, high air-filled porosity and a high diffusion coefficient of oxygen. None of the 9 products tested had the optimum levels of all the different physical parameters. Mixing the tested compost and peat will possibly increase the air-filled porosity of the substrates compared to pure peat, and brings the substrates physical parameters closer to the ideal recommended range. These compost media require further investigation before they can be used directly as an alternative to peat in greenhouse production.

Ionic liquid promoted novel and efficient one pot synthesis of 3,4-dihydropyrimidin-2-(1H)-ones at ambient temperature under ultrasound irradiation

3,4-Dihydropyrimidin-2-(1H)-ones have been synthesized in excellent yields in short reaction time at ambient temperature in the absence of any added catalyst by the reaction of aromatic or aliphatic aldehydes with ethyl acetoacetate (EAA) and urea (or thiourea) in room temperature ionic liquid (IL) under ultrasound irradiation. The evidence for the role of IL in promoting this multicomponent reaction has been given. Based on this evidence, a plausible mechanistic pathway has been postulated.

Nitrogen Selection and Growth Regulator Applications for Improving Shaded Turf Performance

Managing turf for shaded golf course tee boxes is difficult due to few species to choose from and a lack of defined management practices. Supina bluegrass (Poa supina Schrad.) is a novel cool‐season turfgrass with good shade tolerance at mowing heights above 2 cm. This study compared the suitability of supina bluegrass, Kentucky bluegrass (Poa pratensis L.), and creeping bentgrass (Agrostis stolonifera L.) for golf course tees under 80% shade. Treatments included three application timings of trinexapac‐ethyl [4‐(cyclopropyl‐α‐hydroxy‐methylene)‐3,5‐dioxo‐cyclohexane‐carboxylic acid ethyl ester] (TE) and two N types, liquid and granular. Supina bluegrass provided the best overall turf quality among the three species tested. Liquid urea (foliar uptake) improved turf quality of creeping bentgrass while Kentucky bluegrass responded better to granular urea (root uptake). Supina bluegrass response to fertilizer type was seasonally dependent. Both monthly and bimonthly applications of TE (0.05 kg ha−1) significantly improved turf quality, density, and chlorophyll levels of all species, though visual effects of bimonthly applications dissipated before subsequent applications. Creeping bentgrass divot recovery was faster than for either Kentucky bluegrass or supina bluegrass. Divot recovery was not influenced by TE or N source. Supina bluegrass had significantly greater growth rates during late autumn through spring than either Kentucky or creeping bentgrass. The best turf quality was achieved using supina bluegrass, treated monthly with TE, and fertilized with granular N in the spring and liquid N in the summer and autumn.

Effects of Urea and Nitric Acid on Water and Medium Quality and on Response of Anthurium

Excessive bicarbonate concentrations and high irrigation water pH affect the growth and appearance of nursery plants in southern Florida. A greenhouse experiment consisting of five nitrogen (N) rates of urea or nitric acid was conducted to evaluate the influence of N sources and rates in irrigation water on bicarbonate concentrations, medium pH, and growth and appearance of anthurium (Anthurium andraeanum Lind.) plants. Pot medium pH, dry weight, plant appearance and N uptake by plants were significantly affected by N rates in irrigation water amended with either liquid urea or nitric acid, but the differences between the two N sources were not significant. The optimum growth and the best appearance of anthurium were achieved when N was added to irrigation well water as either urea or nitric acid at a rate of 20 mg·L-1 (ppm) and an electrical conductivity in a range of 0.36 to 0.42 dS·m-1 Nitrogen rates at 80 and 120 mg·L-1 induced adverse plant growth because of the greater salinity of the solutions and the lower pH of the medium.

Urea Nitrogen Uptake by Citrus Leaves

Foliar-applied urea nitrogen (N) has potential to become an important component in fertilizer programs for citrus in Florida and other citrus growing areas as it can reduce nitrate leaching into ground water. We evaluated seasonal absorption characteristics of three urea formulations, Triazone-urea, liquid urea, and spray grade urea by citrus leaves that were from 2 weeks to 6 months old. The effect of leaf age on 15N absorption by N-deficient and N-sufficient leaves, together with urea absorption over an eight-week period were studied using greenhouse-grown and field-grown plants. All foliar N applications were based on a recommended rate of 34 kg N/ha in 469 L of water. In the field studies, leaf N was increased similarly by the three urea formulations one week after three weekly applications. Young leaves (0.25 month and 1 month old) absorbed a greater percentage of N than the older leaves (3 month and 6 month old). Epicuticular wax concentration increased and 15N absorption declined with leaf age. Nitrogen deficient leaves (1.80% N) had greater wax concentration and lower N absorption than N sufficient leaves (2.60% N). Four to 8 weeks after urea applications, Triazone-urea sprayed leaves had significantly greater leaf N concentration than leaves sprayed with liquid urea or nonsprayed control leaves. The greenhouse studies revealed that the 15N absorption was greater through abaxial leaf surfaces than through adaxial surfaces regardless of leaf N level and application time. Applying foliar 15N-urea during night (2000 hr to 2200 hr) resulted in greater absorption of 15N than in the morning (0800 hr to 1000 hr) or afternoon (1200 hr to 1400 hr). It is clear that maximum N absorption from foliar urea sprays occurred at night through the abaxial surfaces of young leaves with sufficient N. Triazone-urea acted as a slow-release N source that could be exploited in supplying N over an extended period of time.

Laboratory examination of probe type injectors for ammonia (urea) treatment of baled wheat straw

A portable hand-held device to inject liquid urea solution was designed, built and tested on conventional wheat straw bales. The effects of types of injector, injection pressures and modes of injection on wetted area i.e. liquid distribution pattern and liquid retaining efficiency of baled straw were studied. The liquid was injected at different injection pressures of 1.0, 2.5, 4.0 and 5.5 kg/cm in central horizontal (M ) and eccentric horizontal (M ) modes of injection at predetermined five number Of injecting stations using single orifice flat fan (N ), two-transverse orifice (N ) and triple orifice (N3) injectors. The injector N was1found best in terms of maximum values of wetted area (55.90%) and liquid retaining efficiency (66.60%) at4 kg/cm2 injection pressure in M mode of injection followed by Nand N injectors. Doubling the number of injecting2stations to ten had appreciably irtereased the liquid retaining efficiency and moisture content of ammonia (urea) treated baled straw.

Bioanalytical flow-injection system for control of hemodialysis adequacy

Potentiometric urea biosensor based on ammonium-ion selective electrode has been used in simple flow-injection bioanalytical system for the determination of removed urea in effluent liquid during hemodialysis treatment. The interferences from other components of the spent dialysate (mainly potassium ions) were eliminated using reference cell detector with non-sensitized ammonium-ion electrode. The methods of signal correction were discussed. The presented flow injection analysis (FIA) system allowing monitoring of urea content in the range of concentrations correspond well with the amount of the analyte in real samples (1–20mmol/l). Around 25 samples per hour can be analyzed. Due to long operational life-time of the applied biosensor the FIA system can be useful over 3 weeks. The presented biosensor/FIA system has been successfully applied for the biomedical control of real clinical processes. The results of analysis are useful for the evaluation of the clinical parameters of urea kinetic modeling: parameters KT/V, urea reduction ratio (URR), percentage removal of urea (PRU) and total urea removal (TUR) for intradialytic intervals and urea generation rate (G) and protein catabolic rate (PCRn) for interdialytic intervals. These biomedical parameters are used for describing the adequacy of hemodialysis therapy.

Comparison of the difference and delta 15Nitrogen approaches for evaluating liquid urea ammonium nitrate utilization by maize

Isotopic nitrogen (N) research techniques may be required in watershed studies to determine the impact of landscape position on fertilizer efficiency and the soil supplying power. However, traditional approaches using I5N labeled fertilizer may not be suitable when farmer equipment is used. The δ15N natural abundance isotopic approach has been used to evaluate N cycling in watersheds. The objectives of this study were to measure the precision of the δ15N measurement by the Europa 20–20 ratio mass spectrometer (Europa Scientific Ltd, UK), and to compare the difference and δ15N approaches for measuring fertilizer use by maize (Zea mays). A replicated field study containing two different N rates (0 and 15.7 g N m‐2) were used for the study. Maize samples were collected at the 8th‐leaf, silking, and plant maturity in 1992 and 1993. Samples were dried (80°C), ground (<1‐mm), weighed (stover 12 mg and grain 3 mg), and analyzed fortotal N and δ15N. Fertilizer utilization at the three growth stages was determined using the natural abundance δ15N and nonisotopic difference (fertilizer‐control) techniques. During the study, the Europa 20–20 ratio mass spectrometer (Europa Scientific Ltd, UK) analyzed over a 100 samples a day and had consumable costs of less than $2.00 per sample. The standard deviations of the mean were less than 0.11 and 0.21 %o in 51 and 77% of the stover samples, respectively. In 1992, grain yields were not influenced by N fertilizer additions, while in 1993 grain yields were increased by N fertilizer. The difference method estimated that in 1992, 16% of the N fertilizer was utilized by the crop, while the natural abundance δ15N approach estimated that 36% of the fertilizer N was used by the crop. Differences between calculated values by the two techniques resulted from the difference method calculating net fertilizer use, while the δ15N approach calculated fertilizer contained in the plant. Because the δ15N approach estimates fertilizer use, this approach can be used to calculate soil N contained in the plant. In watershed studies, this information may provide the tools needed to evaluate N use in responsive and nonresponsive sites within a field. This research shows that the δ15N method compliments the difference method, can be used to measure actual fertilizer use when farmer equipment is used, and that the Europa 20–20 ratio mass spectro‐meter (Europa Scientific Ltd, UK) has acceptable precision for the δ15N natural abundance approach.

Fate of Nitrogen Applied to Turfgrass-Covered Soil Columns

Current public concern for the environment has focused on the environmental effects of chemical applications to turfgrass areas. There is little research on the environmental effects of nitrogen (N) applied to turfgrasses. Our objectives were to investigate the hydrology of 50 cm of undisturbed soil columns with a Kentucky bluegrass turf and intact macropores under a heavy (four 2.54 cm applications) and a light irrigation regime (sixteen 0.64 cm applications), and to measure the fate of N, using 15 N as a tracer, when applied to an undisturbed soil column. Mean leachate values for columns under the heavy irrigation regime totaled about six times the amount collected from columns under the light irrigation regime. We found that the heavy irrigation increased N, which leached through the 50 cm of undisturbed soil columns by 30 times and decreased the volatilization of liquid urea compared with columns under the light irrigation.

On-line monitoring of urea in effluent liquid during haemodialysis

An analytical system specially built for on-line urea monitoring is reported. Measurements are carried out in the effluent of a haemodialysis machine. The measuring system employs the dialyser inflow stream as a carrier solution channel in a continuous fashion. The analyser periodically samples the outflow stream of the dialyser by means of an automatic injection valve. The analyser features a bioreactor consisting of immobilized urease and a gas-diffusion module. It is through this module that the urea is converted to ammonia gas which is transferred to another carrier channel, this transports the ammonium ion to a tubular, all-solid-state, ion-sensitive electrode. A timer controls the transport, injection, the measuring and the recording subsystems. The analyser has been used during actual haemodialysis sessions. Urea clearances were also measured in batch, using conventional spectrophotometric clinical equipment. The correlation between both methodologies was sufficient to confirm the usefulness of the developed on-line analyser to monitor the optimal length of haemodialysis sessions.

Spring Wheat Response to Seed Spreader Patterns and Deep Band Fertilizer Placement with an Air Seeder

The air seeder unit has developed rapidly as a method of applying fertilizer and seed in a one-pass operation. Research was conducted with an air seeder unit over 2-yr to determine the influence of four seed spreader patterns and deep band fertilizer placement of five fertilizer forms on hard red spring wheat (HRSW) (Triticum aestivum L.) growth and nutrient uptake. Seed spreader patterns included single row, 3-in. wide paired spread, 5-in. wide spread, and 12-in. wide spread. Fertilizer materials from various sources were combined to form liquid urea ammonium nitrate plus ammonium polyphosphate (UANAPP), liquid ammonium nitrate phosphate (UANP), dry granular urea plus diammonium phosphate (UDAP), dry granular urea nitric phosphate (UNP), and dry granular urea phosphate (UUP) [...]

Yield response of wetland rice to band placement of urea solution in various soils in the tropics

Alternative N-fertilizer management practices are needed to increase productivity and the N-use efficiency of flooded rice (Oryza sativa L.). Seven field experiments were conducted at various sites in Bangladesh and Indonesia to evaluate the effect of time and method of fertilizer-N application on grain yield in transplanted rice. Conventional fertilizer application was compared with band placement of liquid urea using a mechanical push-type injector and point placement of urea supergranules. With band placement, grain yields were up to 38 and 55% higher than with researchers' and farmers' practices, respectively, and similar to those with point placement of urea supergranules.

Volatilization of ammonia from solid and liquid urea surface-applied to perennial ryegrass

SUMMARYA field experiment compared the effects of urea, surface-applied either as a solid or liquid, at a rate of 100 kg N/ha, on ammonia volatilization from an established perennial ryegrass sward on three separate occasions during 1990 at the Agricultural Research Institute, Hillsborough, Northern Ireland. Total NH3 loss over 10 days from prilled urea for each of the three study periods was equivalent to 3.4, 9.1 and 4.4% of N applied. On two occasions, applying urea as a liquid significantly increased NH3 loss compared to prills, whereas on the third occasion there was no significant effect. Increasing the spray volume from 80 to 640 ml/m2 had no significant effect on NH3 volatilization.Surface application of urea as a liquid compared to the prilled form did not lower NH3 volatilization and therefore is not a strategy that would improve the efficiency of urea as a nitrogen source for temperate grassland.

Leaf scorch onPennisetum clandestinumdryland pastures induced by liquid urea ammonium nitrate fertilizer

Transmission electron (TEM) and scanning electron microscopy (SEM) demonstrated that the application of liquid urea ammonium nitrate (UAN 32) fertilizer, in concentrated form, to dryland pastures resulted in leaf scorch and subsequent necrosis, irrespective of the level and concentration of the UAN solution applied. One week after UAN application, most treatments, except those which involved high application rates and high concentrations of UAN, snowed full cuticular and cellular recovery. Furthermore, chloroplasts and granal stacks recovered after such treatment. The addition of a urease inhibitor, ammonium thiosulphate (ATS 12), to the liquid fertilizer did not lower leaf cell damage, but may have aided the recovery process. The higher the application rate and the higher the concentration of the UAN, the greater the extent of damage to the outer waxy cuticle, guard cells and epidermal cells, and to the internal chloroplasts, grana and mesophyll cells. Guard and epidermal cells became flaccid and necrotic, while the cuticle readily peeled away from the leaf surface. Leaf browning was ascribed to the damage caused to the grana within the chloroplasts. Of the combinations tested, the least damaging to the leaf was the application of 69 kg N ha−1 at a concentration of 8% N, combined with a 5% volume/volume (v/v) ATS.

Turf Response to Urease Inhibitors and Cationic Materials Applied in Combination with Urea

We evaluated the response of Kentucky bluegrass (Pea pratensis L.) turf to urea amended with the urease inhibitors PPD, NBPT, and ATS and with the cations K+ (KCl) and Mg+2 (MgCl2). Treatments for the 2-year field experiment included liquid urea applied monthly in June to Sept. 1985 and 1986 at 49 kg N/ha with PPD (1%, 2%, 3% by weight of applied N), NBPT (0.5%, 1%, 2%), ATS (5%, 15%, 25%), K+ (5%, 15%, 25%), and Mg+2 (5%, 15%, 25%). The NBPT was included only in the 1986 field study. The Mg+2 and K+ reduced foliar burn and increased turf quality during mid- and late Summer 1985 at the 5% rate, but clipping yield was not affected by any treatment. In 1986, under milder climatic conditions, PPD and NBPT increased clipping yield by 13.2% and 15.2%, respectively. At the 15% rate, ATS increased clipping yield by 15.1%, but, on average, PPD and NBPT were much more effective. Chemical names used: phenylphosphorodiamidate (PPD), N-(n -butyl) thiophosphoric triamide (NBPT), and ammonium thiosulfate (ATS).

Response of a weed community to nitrogen fertilization: a multivariate analysis

AbstractThe effect of nitrogen fertilizers on the composition of a weed community was investigated in a barley field. Two doses (70 and 140 kg N/ha) of three fertilizers (ammonium sulphate, calcium‐ammonium nitrate, and liquid urea) were used. The results were evaluated using the canonical correspondence analysis. Hybrid analyses and various combinations of environmental variables and co variables were used to separate the influence of the dose and the type of fertilizer and to separate the direct and indirect effects of fertilization. The results reveal that both the dose and type of fertilizer have a significant effect on the composition of the weed community. The results suggest that both the direct effect of fertilizer and an indirect effect, through increased competition of the crop, are important determinants of weed community composition.

Incorporation of urea in puddled rice soils as affected by tillage implements

Thorough incorporation of urea into the soil is known to reduce the high N losses associated with the traditional practice of broadcasting urea onto puddled lowland rice fields. Few studies have, however, examined the effectiveness of farm-level implements for incorporating broadcast urea during final land preparation in small rice fields. A field experiment was conducted at two sites in the Philippines to compare the effectiveness of several commonly available and experimental tillage implements for basal incorporation of urea. The relative effectiveness of N incorporation and relative susceptibility of N to ammonia volatilization losses were assessed from floodwater (urea + ammoniacal)-N and partial pressure of ammonia (pNH3) following urea application to puddled, unplanted soil. Conventional water buffalo- and single axle tractor-drawn comb harrows were equally, but only partially, effective in reducing floodwater (urea + ammoniacal)-N andpNH3 by 42 to 56% of the values for broadcast prilled urea (PU) without incorporation. Removal of the comb harrow from the single axle tractor did not reduce the effectiveness of PU incorporation, indicating that the cagewheel rather than the comb harrow was largely responsible for fertilizer incorporation. An experimental conical puddler was slightly more effective than the conventional comb harrow. The movement of transplanters through the field did not effectively incorporate PU. A power weeder, frequently used by researchers to incorporate fertilizer in small experimental plots, was less effective than traditional comb harrows, reducing floodwater (urea + ammoniacal)-N by only 35%. No tillage implement for incorporating urea reducedpNH3 as effectively as did the liquid urea band injector. Results suggest that sizeable losses of fertilizer N still occur following incorporation of PU with tillage implements commonly used by small rice farmers. Considerable scope remains for the improvement of fertilizer incorporation in puddled rice soils.

Nitrogen-15 balance in transplanted and direct-seeded flooded rice as affected by different methods of urea application

Alternative N-fertilizer management practices are needed to increase productivity and the N-use efficiency of flooded rice (Oryza sativa L.). In the 1987 dry season, a field study using 15N-labeled urea evaluated the effect of the time and method of fertilizer-N application on grain yield and N-use efficiency in transplanted and direct-seeded flooded rice. Conventional fertilizer application (broadcasting and incorporation) was compared with band placement of liquid urea and point placement of urea supergranules. With band or point placement, the grain yields were significantly greater, and the partial pressure of NH3 (pNH3) in the floodwater was significantly reduced. In the transplanted rice, conventional fertilizer-N application gave a 64% total 15N recovery and 38% crop (grain and straw) recovery. Band placement of liquid urea N resulted in 92% total and 73% crop recovery. In the direct-seeded flooded rice, a conventional N application gave 72% total and 42% crop recovery; band placement, 98% total and 73% crop recovery; and urea supergranule point placement, 97% total and 75% crop recovery.