Fate of Fertilizer15N applied as urea and ammonium sulphate in opium poppy (Papaver somniferum L.) grown under greenhouse conditions

Laboratory incubation and greenhouse experiments were conducted to investigate the comparative effectiveness of urea and ammonium sulphate in opium poppy (Papaver somniferum L.) using¹⁵N dilution techniques. Fertilizer treatments were control (no N), 600 mg N pot^–1 and 1200 mg N pot^–1 (12 kg oven dry soil) applied as aqueous solution of urea or ammonium sulphate. Fertilizer rates, under laboratory incubation study were similar to that under greenhouse conditions. A fertilizer¹⁵N balance sheet reveals that N recovery by plants was 28–39% with urea and 35–45% with ammonium sulphate. Total recovery of¹⁵N in soil-plant system was 77–82% in urea. The corresponding estimates for ammonium sulphate were 89–91%. Consequently the unaccounted fertilizer N was higher under urea (18–23%) as compared to that in ammonium sulphate (9–11%). The soil pH increased from 8.2 to 9.4 with urea whereas in ammonium sulphate treated soil pH decreased to 7.3 during 30 days after fertilizer application. The rate of NH₃ volatilization, measured under laboratory conditions, was higher with urea as compared to the same level of ammonium sulphate. The changes in pH of soil followed the identical trend both under laboratory and greenhouse conditions.     

Nitrogen losses from labelled ammonium sulphate and Urea applied to a flooded rice soil

A field study was carried out to estimate volatilization and denitrification losses of¹⁵N applied as urea of ammonium sulphate to a wet land rice soil. Nitrapyrin (a nitrification inhibitor) was also applied to some treatments along with the two N sources.The N level in floodwater increased rapidly, soon after applying fertilizer N, but decreased to lower values within a few days. At 1 week after applying urea and ammonium sulphate, N losses were 37.6% and 60.6% respectively. The corresponding figures after 4 weeks were 55.7% and 61.9% while with nitrapyrin added the corresponding values were 37.2% and 57.2% after 1 week and 52.7 and 65.0% after 4 weeks respectively indicating that losses due to dentrification are negligible.     

Nitrogen use efficiency,floodwater properties,and nitrogen-15 balance in transplanted lowland rice as affected by liquid urea band placement

Alternative N fertilizer management practices are needed to increase productivity and N use efficiency in lowland rice (Oryza sativa L.). In 1986 dry season, a field study using¹⁵N-labeled urea evaluated the effect of time and method of fertilizer N application on grain yield and N use efficiency. Conventional fertilizer application was compared with band placement of liquid urea and point placement of urea supergranules (USG). Grain yields were significantly higher with either band or point placement than with broadcast and incorporation or surface application. Partial pressure of NH₃ (NH₃) was significantly reduced when N was deep-placed.¹⁵N balance data show that fertilizer N applied basally and incorporated gave a total¹⁵N recovery of 52% and crop (grain + straw) recovery of 30%. Band placement of liquid urea N resulted in 82–90% total and 57–65% crop¹⁵N recovery. USG point placement gave 94% total and 70% crop¹⁵N recovery. Deep placement of second N application gave only slightly higher (98%)¹⁵N recovery compared with broadcast application (89%).     

Nitrification and nitrate movement from ammonium sulphate and urea in sandy soils as affected by their previous applications

Two successive applications of urea and ammonium sulphate (AS) at varying intervals were given in two soils, one of which was salt affected. The nitrification and nitrate leaching after both the applications of fertilizers was studied. The nitrification of first application of AS was faster than urea on both soils. However, the nitrification rate of both fertilizers was slow in salt effected soil. The same trend of results was observed with second application of fertilizers. However, the nitrification of second application given within 6 weeks of the first application proceeded at a much faster rate than that of the first application. The amount of NO ₃ ^- that moved down with periodic water application was related with nitrification rate and the amount of fertilizer nitrified at the time of water application.     

An assessment of granular urea/ammonium sulphate and urea/potassium nitrate fertilizers on nitrogen recovery by ryegrass

The comparative effects of ammonium sulphate (AS), potassium nitrate (KNO₃), urea (U) or combined 1:1 (w/w) U/KNO₃, U/AS granular products were investigated on dry matter (DM) yield and¹⁵N utilisation by perennial ryegrass grown under controlled environmental conditions.The DM yield and apparent N recovery with the single N sources was in the order KNO₃ > AS > U. The¹⁵N budget in shoots, roots and soil indicated that only 55% of the urea N was recovered at the end of the experiment compared with 87% and 86% for AS and KNO₃ respectively. The DM yield and apparent N recovery from the combined U/AS source was significantly higher than would be expected (P < 0.01) based on the proportions of each N source in the mixture. Differentially labelling the U and AS with¹⁵N indicated that AS enhanced the shoot % utilisation of urea by 38% (P < 0.001) whereas urea reduced the shoot % utilisation of AS by 14% (P < 0.01). These results indicate that an interaction occurred between U and AS when combined in a 1:1 (w/w) ratio in the same pellet.     

Ammonia losses from surface-applied urea as related to urea application rates,plant residue and calcium chloride addition

Volatile losses of NH₃ from surface-applied urea are known to decrease in the presence of soluble Ca-salts or with a decrease in easily decomposable organic matter content (EDOM), both of which influence urease activity. How these factors interact to affect NH₃ losses is not fully understood. Studies were conducted to determine the effect CaCl₂ in sand with varying rates of EDOM on NH₃ losses from surface applied urea. The same effects were examined on agricultural soils containing partially decomposed native organic matter (NOM). Determinations were made in the laboratory on field soils, sand free of organic matter and sand with known amounts of grass clippings (GC, EDOM). Low levels of GC in sand with low amounts of added urea resulted in little NH₃ loss. Ammonia loss increased as more N was applied at the low levels of GC. The loss was independent of urea application rates at high levels of GC. Ammonia losses were reduced more effectively at low EDOM and NOM in the presence of Ca. Incubation of sand with GC at low rates prior to urea addition increased NH₃ losses relative to high levels of non-incubated GC. For the above situation incubation for as high as 24 days resulted in equivalent NH₃ losses. The amount and state of decomposition of existing organic matter affected the degree of NH₃ loss from surface placed urea and its control by added Ca-salts. Microbial decomposition of EDOM, such as might occur in the spring prior to urea addition, led to greater NH₃ losses. Greater loss of NH₃ from urea might be an indication of a larger ureolytic microbial population leading to increased urease production.     

Evaluation of compacted urea fertilizers prepared with acid and non-acid producing chemical additives in three soils varying in pH and cation exchange capacity; II. Yield and N use efficiency by rice

With a view to evaluate the effect of different chemical additives on the efficacy of urea, a green house study was conducted with wet season rice (Oryza sativa L.) as test crop. The results showed that compaction of phosphogypsum (PG), diammonium phosphate (DAP), ZnSO₄, NH₄Cl or KCl with urea increased the rice yield and N use efficiency as compared to that obtained with straight urea. A significant positive correlation between potential N loss (measured by soluble N in floodwater) and NH₃ volatilization (measured by forced air draft system) was observed. The results clearly indicate that N use efficiency can be increased through suitable modification of urea by compacting it with acid and non-acid producing fertilizers such as NH₄Cl, KCl, ZnSO₄ and DAP or industrial byproduct like phosphogypsum.     

Methane production from anaerobic soil amended with rice straw and nitrogen fertilizers

Laboratory experiments were conducted on the effects of rice straw application and N fertilization on methane (CH₄) production from a flooded Louisiana, USA, rice soil incubated under anaerobic conditions. Rice straw application significantly increased CH₄ production; CH₄ production increased in proportion to the application rate. Urea fertilization also enhanced CH₄ production. The maximum production rate was 17% higher, and occurred 1 week earlier, than that of soil samples which did not receive urea, possibly due to the increase in soil pH following urea hydrolysis. The increase in soil pH following urea hydrolysis may have stimulated CH₄-generating bacteria by providing more optimal soil pH conditions or contributed to the drop in redox potential (Eh). The significant decrease in both the production rate and the total amount of CH₄ by application of NH₄NO₃ was associated with increases in soil Eh after addition of this oxidant. Addition of 300 mg. kg^–1 NO ₃ ^- -N increased soil Eh by 220 mV and almost completely inhibited CH₄ production. However, this inhibitory effect was short-termed. Soon after the applied NO ₃ ^- -N was reduced through denitrification, CH₄ production increased. When (NH₄)₂SO₄ was applied, the inhibition of CH₄ production was not associated with an increase in soil Eh which did not change significantly. A direct inhibitory effect of sulphate on methanogenesis might have been more important.     

Evaluation of compacted urea fertilizers prepared with acid and non-acid producing chemical additives in three soils varying in pH and cation exchange capacity; I. NH3 volatilization

Efficacy of different acid-producing chemical additives was evaluated in terms of pH, urea hydrolysis, NH₄-N dynamics and NH₃ volatilization in an Alfisol, a Vertisol and an Inceptisol. Compacting phosphogypsum (PG), diammonium phosphate (DAP), ZnSO₄ and KCl separately with urea slowed down urea hydrolysis and reduced NH₃ volatilization loss. Peak volatilization loss of NH₃ occurred between 2 to 4 days of fertilizer application in Vertisol and Alfisol, but between 4 to 6 days in Inceptisol. Cation exchange capacity (CEC) of soil influenced more in reducing NH₃ loss than native soil pH, as lower amount of NH₃ was lost from Vertisol (pH=8.0, CEC=43.92 cmol_c kg^-1) than from Alfisol (pH=5.8, CEC=13.82 cmol_c kg^-1). The loss from Inceptisol was in between the above two soils.     

Effect of magnesium sulphate addition to urea on nitrogen loss due to ammonia volatilization

Fertilizer was applied as urea alone or as a mixture of urea and magnesium sulphate (MgSO₄·1H₂O) to study the effect on ammonia volatilization under laboratory conditions in relation to soil texture, N:Mg ratio, air flow rate, fertilizer form (solid or liquid) and organic material. When the mixture of urea and magnesium sulphate (UMM) was applied at a ratio of 1:0.21, significantly lower NH₃-N losses than from urea were found in 2 of 6 soils, and 4 soils showed a similar tendency. Increasing the N:Mg ratio to 1:0.5 resulted in significantly lower NH₃-N loss. Lower air flow rates reduced ammonia loss from UMM more than from urea alone. The effectiveness of UMM over urea was not improved in the liquid form. Increase of organic material had no influence on NH₃-N loss from urea alone or UMM.     

Fate of nitrogen applied in different fertilizers to the surface of a calcareous soil in Syria

¹⁵N-labelled ammonium sulphate or¹⁵N-labelled urea were each applied in solutionat a rate of 30 kg N ha^-1 to the surface of 20soil cores (52 mm internal diameter × 100 mm deep)located on a field experiment at the ICARDA station,Tel Hadya, Syria. Recovery of ¹⁵N-label in theammonium, nitrate, organic and/or urea-N pools in thesoil was measured on days 0, 1, 2, 5 and 13 afterapplication. Total recovery of ¹⁵N was initially100%, but by day 13 after application it had declinedto 51% with urea and 73% with ammonium sulphate.Ammonium nitrate labelled either as ammonium or asnitrate was also applied to the soil surface of 8other cores at the same time. ¹⁵N recovery in thefour soil N pools was measured only on day 12 afterapplication. Total recovery of ¹⁵N-label was 75%with labelled ammonium and 57% with labelled nitrate.Volatilization of ammonia from this calcareous soil(pH 8.1) is one probable mechanism of N loss fromammonium and urea fertilizers: with nitrate bothleaching beyond the base of the core (i.e. 100 mm) and denitrification were responsible for Nlosses. These large losses of N immediately afterapplication have implications for fertilizermanagement practices.     

Uptake and apparent utilization of urea and ammonium nitrate in wheat seedlings

Intact wheat (Triticum aestivum cv. Quern) seedlings that were grown in presence or absence of NH₄NO₃ were exposed to solutions containing CO(NH₂)₂, NH₄NO₃, CO(NH₂)₂ + NH₄NO₃, CO(NH₂)₂ + KNO₃ and CO(NH₂)₂ + (NH₄)₂SO₄ for consecutive periods of 3, 3, 6, 12 and 24h and N uptake determined by solution depletion measurements. Differences in ethanol-soluble N and ethanol-insoluble N content of roots and shoots of control (zero time) seedlings and seedlings exposed to CO(NH₂)₂, NH₄NO₃ and CO(NH₂)₂ + NH₄NO₃ for 48 h were used to characterize N utilization during/following uptake.Regardless of initial N status, uptake of N from CO(NH₂)₂ was less than one-third of that from NH₄NO₃. Relative absorption of the CO(NH₂)₂ and NH₄NO₃ was not substantially altered by acidity control of the uptake solutions. There was a reciprocal antagonism between uptake of CO(NH₂)₂ and uptake of NH₄NO₃. Whereas CO(NH₂)₂ inhibited NH₄ absorption in each set of seedlings, it decreased NO₃ uptake only in seedlings that had been pretreated with N. Simultaneous presence of KNO₃ enhanced CO(NH₂)₂ uptake but presence of (NH₄)₂SO₄ decreased it to the same extent as NH₄NO₃. All absorption processes involving CO(NH₂)₂ and NH₄ were substantially restricted by pretreatment of the seedlings with NH₄NO₃. The results suggest that apparent utilization of ambient N was dependent on initial N status of the seedlings and on the nature of the N species to which they were exposed.     

Efficiency of urea and ammonium sulfate for wetland rice grown on an acid sulfate soil as affected by rate and time of application

A pot experiment was conducted in a greenhouse to assess the effect of rate and time of N application on yield and N uptake of wetland rice grown on a Rangsit acid sulfate soil (Sulfic Tropaquepts). Response of rice at N rates of 800, 1600 and 2400 mg N/pot (5 kg of soil) was compared between urea and ammonium sulfate when applied at two times: (i) full-rate basal at transplanting and (ii) one half at transplanting and one half at the PI stage. In addition, labelled¹⁵N sources were applied either at transplanting or at the PI stage to determine the nitrogen balance sheet in the soil/plant system.No significant difference in grain and straw yields between urea and ammonium sulfate at low rate was observed. At the higher N rates, urea produced higher yields than did ammonium sulfate regardless of timing. The highest yields were obtained when urea at the high N rate was applied either in a single dose or a split dose while lowest yields were observed particularly when ammonium sulfate at the same rate was applied. Split application of N fertilizer was shown to be no better than a single basal application. The occurrence of nutritional disorder, a symptom likely reflected by high concentration of Fe (II) in combination with soluble Al, was induced with high rate of ammonium sulfate.In terms of fertilizer N recovery by using¹⁵N-labelling, ammonium sulfate was more efficient than urea when both were applied at transplanting. In contrast, application at the PI stage resulted in higher utilization of urea than of ammonium sulfate. The recovery of labelled N in the soil was higher with urea than with ammonium sulfate when the two sources were applied at transplanting, while the opposite result was obtained when the same fertilizers were applied at the PI stage. The losses from urea and ammonium sulfate were not different when these fertilizers were applied at transplanting but loss from urea was higher than that from ammonium sulfate when both were applied at the PI stage.     

Effect of algicides on urea fertilizer efficiency in transplanted rice

The effects of the algicides terbutryn and copper sulfate on the potential for reducing the gaseous loss of NH₃ from urea applied to rice were examined in experiments with 2 methods of N fertilizer management, 2 or 3 N rates, and 3 algicide treatments. The experiments were conducted during the 1986 dry and wet seasons in an experimental field at Pila, Laguna, Philippines.Copper sulfate had little effect as an algicide at the rate used, but terbutryn immediately reduced algal growth. The populations of species resistant to terbutryn probably increased, but terbutryn had no long-term effect on the total number of colony-forming units of algae. There was some evidence that terbutryn reduced photodependent N₂ fixation as estimated by acetylene reduction assay.Terbutryn, when applied with urea 10 days after transplanting, reduced the maximum floodwater pH by 0.9 units or more for 7 d in the DS and by about 0.5 units for 8 d in the WS. Terbutryn increased the ammoniacal-N (AN) concentration in the floodwater 100% or more in the DS and 60% in the WS. The combined effect of terbutryn on the floodwater pH and AN concentration was reduced photodependent NH₃ partial pressure (NH₃), about 25% in the DS and 38% in the WS. deceased     

Nitrogen utilization by lowland rice as affected by fertilization with urea and green manure

Field studies were conducted during two consecutive wet seasons in flooded rice (Oryza sativa L.) to determine the effect of green manure on urea utilization in a rice-fallow-rice cropping sequence. Replicated plots were fertilized with 60 to 120 kg of urea N ha^–1 in three split applications (50, 25 and 25%) with or without incorporation of dhaincha (Sesbania aculeata L.) (100 kg N ha^–1). During the first crop only 31 to 44% of the urea added was used by the rice. Incorporatingin situ grown dhaincha (GM) into the soil at transplanting had little effect on urea utilization. Forty-four to 54% of the N added was not recovered in the soil, rice crop, or as nitrate leachate during the first cropping season. Incorporation of GM had no effect on fertilizer N recovery. Only about 2% of the urea N added to the first rice crop was taken up by the second rice crop and, as in the first crop, the GM had little effect on residual N, either in amount or utilization.     

Effect of lime nitrogen on the efficiency of urea and other ammonium nitrogen fertilizers

Five pot experiments were conducted with wheat and rice in a net house to study the effect of lime nitrogen (LN, contains about 55% calcium cyanamide) amendment rates on the efficiency of urea, the recovery urea-¹⁵N, the efficiency of the three nitrogen fertilizers(NF), on the efficiency of urea in the three soils, and on NO ₃ ^- -N leaching from a flooded soil. A rate of LN-N of 5–8% of applied fertilizer N increased the recovery of labeled urea-N by 9.42%. The effect of LN on the efficiency of NF was urea > ammonium sulfate > ammonium chloride. Under flooded conditions, LN decreased NO ₃ ^- formation and leaching.Responses of several crops to LN amended fertilizers were also studied in field experiments. At equal NPK applications, the efficiency of basal applications to rice, wheat, corn, potatoes, soybean, peanut, grapes, peaches, melon and watermelon were bette r with LN than without. Efficiency with a basal fertilizer for rice or wheat with LN were the same as with the same fertilizer without LN applied in split applications.     

Coated and modified urea materials for increasing nitrogen use efficiency of lowland rice in heavy clay soils

Conventional as well as modified nitrogen sources and application methods were evaluated under rainfed lowland conditions in heavy clay soils of Bihar, India for 4 years. Modified nitrogen sources, viz. sulfur-coated urea (SCU) and urea super-granules (USG) were tested against prilled urea (PU) under four levels of N (0, 29, 58 and 87 kg N/ha) in the wet season. A high yielding nonphotoperiod sensitive, long duration variety Pankaj was grown in all the four years.Point placement of USG and basal incorporation of SCU resulted in significantly higher panicle numbers per square meter, 100 grain weight and grain yield at all the levels of N tested. The unfilled grain percentage was lower in USG and SCU treatments.Regression analysis using a multifertilizer response model (MRM) showed that rice responded significantly to PU in three years out of four years, to SCU in four years and USG in three years.Economic analysis viz. input and output analysis based on the price of fertilizer (1 kg N as PU at $0.5; USG and SCU costing 10% more than PU), rough rice (ranging from 18.0 to 20.0 $ per ton) and labour wages at 1.0 $ per man day unit, also showed that USG and SCU are more input efficient than PU.     

The comparative effect of a mixed urea,ammonium nitrate,ammonium sulphate granular formulation on the efficiency of N recovery by perennial ryegrass

The¹⁵N isotope was used to study the mode of action of individual nitrogen sources in a 30% urea:30% ammonium nitrate: 10% ammonium sulphate:30% filler (w/w) granular fertilizer for perennial ryegrass in a greenhouse pot experiment. The fertilizer consisted of two types of granules, one containing 80% urea and 20% filler and the second containing 48% ammonium nitrate (AN), 16% ammonium sulphate (AS) and 36% filler. In addition the effect of dolomite compared with silica as the filler was investigated on nitrogen recovery from the 30:30:10:30 formulation.Dolomite adversely affected the recovery of nitrate N from the system and evidence suggested that MgCO₃ was the active component. Granules containing dolomite resulted in a lower dry-matter yield than those containing silica, however the difference was not significant as nitrate contributed only 20% of the N in the formulation. AN gave the greatest DM yield and urea the lowest with AS being intermediate. The¹⁵N budget in shoots, roots and soil indicated that only 65% of the N from urea was recovered at the end of the experiment compared with 86% for AN and 91% for AS. The dry-matter yield of the 30:30:10:30 formulation using silica as the filler was intermediate between urea and AN; however, the apparent N recovery was significantly higher than expected from the sum of the individual components. The use of¹⁵N labelling indicated that using separate granules for ammonium N and urea the recovery of urea was improved by 11% in the triple N mixture when both AN and AS were present in the second granule compared to the recovery on its own. The enhanced recovery of urea appeared to be a function of AN and AS acting together as neither source in double combination with urea had any effect on urea N recovery.Urea enhanced the recovery of nitrate N by 10% but decreased the recovery of AS by 6% (in the 30:30:10:30 formulation) in comparison with the single sources on their own. The results indicate that interactions can occur between N sources even when they are physically separated by being in different granules.     

Inhibition of algal photosynthesis to control pH and reduce ammonia volatilization from rice floodwater

When urea or ammoniacal-N fertilizers are applied to the floodwater of a rice crop, fertilizer use efficiency is often reduced because there are substantial losses of NH₃ by volatilization. As pH rises the potential loss increases exponentially due to the increasing dominance of volatile NH₃ gas in equilibrium with NH ₄ ⁺ . We postulate that the daytime pH rise is caused mainly by photosynthesis of algae and Cyanobacteria, and that addition of a suitable photosynthetic inhibitor, concurrently with fertilizer, should suppress the pH rise, thus conserving N in the form of the non-volatile NH ₄ ⁺ . We selected terbutryne (2-(tert-butylamino)-4-(ethylamino)-6-(methylthio)-s-triazine) as the most promising inhibitor. In rice floodwater fertilized with urea the addition of terbutryne dampened the diurnal fluctuation in pH for 6 days and significantly increased the ammoniacal-N (AN) concentration measured in the floodwater. The concentration of ammonia gas in the air in equilibrium with the water, ₀, which is proportional to the gaseous flux of NH₃ at a given wind speed, was substantially reduced by terbutryne addition. Maximum values were reduced by over 50%. Terbutryne reduced the calculated cumulative NH₃ emission by 43%, relative to the fertilizer (N + P) control. Terbutryne also suppressed photosynthetic oxygen production. Therefore, it may reduce N fertilizer losses by inhibiting nitrification, an aerobic process, so retarding subsequent denitrification losses of gaseous nitrogen and nitrogen oxides.Part of the supporting documentation for Fertilization of Crops. International Patent Application PCT/AU86/00093 filed 11 April 1986.     

硫酸铵与氯化钾生产硫酸钾的研究

研究了氨法脱硫副产的硫酸铵溶液直接与氯化钾进行复分解反应生成K2SO4结晶的工艺参数.离心分离K2SO4结晶,经干燥后制得合格的农用化肥硫酸钾产品.试验表明：反应时间3h、反应温度30℃、L/G为1.2,KCl与（NH4） S04质量比1.10条件下,采用硫酸铵与KCl定量配比投料能生产出硫酸钾合格品.