• Korean Journal of Soil Science and Fertilizer
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• v.30 no.2
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• pp.114-121
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• 1997

Latex Coated Urea(LCU) was compared with ordinary urea under different methods of application in terms of N use efficiency and yield of rice, 1995 and 1996. The study was carried out on Jeonbug silty clay loam, in Honam Agricultural Experiment Station. The fertilizer treatments involved (1) conventional application of urea (44kg N/ha at transplanting, 33kg N/ha at five leaves stage, 33kg N/ha. (4) 55kg N/ha at transplanting and 33kg N/ha as urea at panicle initiation stage, and (5) without N. It was found that by combining LCU(as basal application) and urea(as topdressing at panicle initiation stage), at the rate of 80% of conventional rate with ordinary urea is most effective for the saving of N and increasing the use efficiency of N by rice. It was, however, observed that the efficacy of LCU was affected by the temperature during the growth of rice.

• Korean Journal of Soil Science and Fertilizer
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• v.34 no.6
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• pp.407-412
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• 2001

This study was conducted to find out the effect of slow-release nitrogen fertilizer, such as latex coated urea(LCU) and Meister10(MS10) on direct seeded rice in dry soil(DS). Junghwabyeo, and early maturity rice cultivar was grown on the plots which were treated with None-nitrogen. urea. LCU and MS10 plot. Growth characteristic, yield and yield components were investigated. Nitrogen uptake-efficiency and physico-chemical properties of soil before-after experiment were analyzed. Plant height and number of tillers $m^{-2}$ in LCU and MS10 plot at early grow stages were higher than those in urea plot. Plant height and number of tillers $m^{-2}$ grown on the plot of Ms10 plot were higher than those of LCU plot. The number of seedling $m^{-2}$ were no significant differences among None-N, urea, and MS10 plot in DS. Heading date and leaf color were higher with Urea than LCU and MS10 plot. Culm length in LCU and MS10 plot were longer compared with urea plot, but panicle length was similar among with Urea, LCU and MS10 plot. Number of panicles $m^{-2}$ was greater in order of MS10 > LCU > Urea plot. Yield were greater in order of MS10 > LCU > Urea plot. Nitrogen uptake and nitrogen efficiency were greater in order of MS10 > LCU > urea plot. After the experiment, total content of nitrogen in soil was not changed at all treatments, but pH, P and Si of soil were lower than those of before experiment at all treatments.

• Korean Journal of Soil Science and Fertilizer
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• v.34 no.6
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• pp.401-406
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• 2001

This study was conducted to find out the effect of slow-release nitrogen fertilizer, such as latex coated urea(LCU) and Meister10(MS10) on direct seeded rice in flooded soil(FS). Junghwabyeo, and early maturity rice cultivar grown on the plots which were treated with None-nitrogen, urea, LCU and MS10 plot. Growth characteristic, yield and yield components were investigated. Nitrogen uptake-efficiency and physico-chemical properties of soil before-after experiment were analyzed. Plant height and number of tillers $m^{-2}$ in LCU and MS10 plot at early grow stages were higher than those of Urea plot. MS10 and LCU plot showed similar tendency on the plant height but MS10 plot was higher than LCU plot on the number of tillers $m^{-2}$. The number of seedling $m^{-2}$ were no significant differences among None-N, urea, and MS10 plot. Heading date and leaf color were no significant differences among None-N, urea, and MS10 plot. Culm length in LCU and Ms10 plot were longer compared with urea plot, but panicle length were similar among with Urea, LCU and MS10 plot. Number of panicles $m^{-2}$ was highest in MS10 plot and it was similar between LCU and Urea plot. Yield were greater in order of Ms10 > LCU > Urea plot. Nitrogen uptake and nitrogen efficiency were greater in order of MS10 > LCU > urea plot. After the experiment, total content of nitrogen in soil was not changed at all treatments, but pH, P and K of soil were lower than that of before experiment at all treatments.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.3
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• pp.212-219
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• 2000

This study was conducted to investigate methane emission among nitrogen fertilizers in paddy soil(Jeonbug series, occurring on fluvio-alluvial plain). The application rates of rice straw was $5,000kg\;ha^{-1}$ with $110kg\;N\;ha^{-1}$ as chemical fertilizer. It was found that the methane flux tended to be lower in ammonium sulfate than in urea and latex coated urea(LCU). The seasonal variations of the methane emission flux was high during the heading stage of the rice plant. Methane concentration in the soil solution was the highest at 5cm depth, but decreased with upper and lower depth. Methane emission under rice straw application was $0.265g\;m^{-2}\;day^{-1}$ by urea application. $0.207g\;m^{-2}\;day^{-1}$ by ammonium sulfate application, $0.318g\;m^{-2}\;day^{-1}$ by latex coated urea(LCU) application while methane emission under non rice straw application was $0.192g\;m^{-2}\;day^{-1}$ by urea application, $0.165g\;m^{-2}\;day^{-1}$ by ammonium sulfate application, $0.179g\;m^{-2}\;day^{-1}$ by latex coated urea(LCU) application.

• Korean Journal of Soil Science and Fertilizer
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• v.32 no.2
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• pp.140-146
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• 1999

This research was conducted to investigate the changes of $NH_4-N$ in soil, nitrogen uptake by rice plant, nitrogen-use efficiency and rice yield by the application of latex coated urea(LCU) on 10-day old seedling transplanted with machine on paddy field, Jeonbuk series at the Honam area, from 1997 to 1998. Almost all nitrogen in LCU application as basal dressing in whole layer was dissolved until maximum tiller stage, the maximum dissolution time was productive tiller stage and $NH_4-N$ content of conventional plot with surface application of fertilizer were lowered at full periods. Nitrogen deficiency symptom were appeared at heading stage of 31.6% SPAD value and nitrogen concentration was 1.29% shoot. From heading stage to ripening stage, the necessity of nitrogen-fertilizer was $2.9kg\;ha^{-1}$ for the conventional split application plot and $11.9kg\;ha^{-1}$ for the whole layer application plot of LCU basal dressing. Nitrogen-use efficiency was higher at the LCU application plot than the conventional application plot and was increased for 12.7% by fertilization at panicle forming stage. The additional fertilization at panicle forming stage to basal dressing of LCU causes 13% yield increase.

• Korean Journal of Soil Science and Fertilizer
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• v.31 no.4
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• pp.324-329
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• 1998

To investigate the changes of $NH_4-N$ in soil, nitrogen uptake by rice plant, nitrogen use efficiency and rice yield by the application of Latex Coated Urea(LCU) on direct seeding rice, rice was planted on paddy field, Jeonbuk series at the Honam area, from 1996 to 1997. Nitrogen in LCU applied as basal dressing in whole layer was dissolved almost untill non-productive stage. Thus, nitrogen deficiency symptom appeared and N in shoot was 1.75% showing 28.1 of SPAD value at heading stage. However percentage recovery of fertilizer N was higher in LCU than with urea application. Top dressing of urea at panicle initiation stage in addition to basal dressing of LCU, increased rice yield by 9%. Conventional split application of urea on the surface decreased the percentage recovery of fertilizer N to 56.9% of whole layer application plot.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.52 no.3
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• pp.311-319
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• 2007

This study was conducted to estimate effects of application of controlled release complex fertilizer with latex coated urea (LCU-complex) on growth and grain quality of rice under direct seeded on dry paddy (DS) and transplanted on flooding paddy (TP). Three types of latex coated urea different nitrogen (N) releasing were LCU40, LCU80 and LCU100. The time of N releasing of LCU formulations in water at both 20 and $30^{\circ}C$ was faster in the order of LCU40, LCU80, LCU blend (LCU40, LCU80 and LCU100 was mixed in ratio of 2:2:1), and LCU100. The number of tillers and dry matter weight were great in order of LCU-complex 100% > LCU-complex80% > urea and plant height was not significant. Grain yields at LCU-complex80% in both DS and TP plot were similar to those of urea application. N recovery of LCU-complex80% and 100% was improved 8 and 6% compared to that of conventional urea split application in DS plot and 9 and 4% in TP. Content of protein of grain at applied LCU-complex was less 0.8% and $0.1{\sim}0.7%$ than that of urea in DS and TP, respectively. Content of amylose and Mg/K ratio in rice grain was not significant. Consequently application of LCU-complex blended types of coated urea different N releasing can be reduced 20% of N without yield reduction and improved grain quality compared with urea application.

• Korean Journal of Soil Science and Fertilizer
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• v.31 no.3
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• pp.259-265
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• 1998

A field experiment was conducted to investigate changes of $NH_4-N$, N uptake, N use efficiency and rice yield by the Latex coated urea(LCU) application on wet-seeding rice from 1994 to 1997. Nitrogen deficiency symptom appeared when LCU was applied as basal dressing continuously until the ripening stage during normal temperature year, but was completed at heading stage during year at high temperature. Percentage recovery of fertilizer N was higher in LCU than in urea but decreased in high temperature. Turn over of N applied as LCU to grain increased more during years high temperature than the normal year. Rice yield with LCU treatment compared to conventional treatment was similar during the normal year but decreased by 6% during year of high temperature. Top dressing of urea at panicle initiation stage in addition to basal dressing of LCU increased rice yield to 12%.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.52 no.3
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• pp.296-302
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• 2007

This study was conducted to evaluate the effect of slow release fertilizers (SRF), crotonylidene diurea (CDU) and latex coated urea (LCU), on nitrogen (N) use efficiency (NUE) and nitrate-N leaching in a silty clay loam soil under polyethylene film mulching (PFM) for sesame cultivation. In PFM plot, concentrations of $NO_3-N$ and $NH_4-N$ in SRF applied soils were less than that in the urea plot during the whole growing period. However, $NO_3-N$ and $NH_4-N$ in all the non-mulched plots (NM) were not significantly different. Urea-N in soil treated with SRF was higher than urea plot until 50 days after application and was comparable in all the treatments after 50 days. $NO_3-N$ concentrations in leached solution in 21 days after urea fertilization in PFM and NM were 26 mg $L^{-1}$ and 83 mg $L^{-1}$, respectively. However, $NO_3-N$ in leached solution at applied CDU and LCU was less than that of urea similar to nitrate concentration in soil. $NO_3-N$ in leached solution in applied CDU and LCU in 44 days after application was about 25% lower than that urea plot and PFM, while the $NO_3-N$ concentration of CDU and LCU treatment in NM did not changed. Application of SRF increased the yield of sesame and N recovery compared to urea and there was a little difference between SRF and N levels. In conclusion, application of 80% N level with SRF increased N recovery and reduced nitrate leaching without reduction of yields compared with urea application.

• Korean Journal of Soil Science and Fertilizer
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• v.38 no.6
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• pp.321-327
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• 2005

Ammonia ($NH_3$) volatilization was measured from latex coated urea (LCU) and normal urea treated rice paddy under transplanting rice culture in Milyang in 2002 and 2003. The $NH_3$ volatilization from incubation experiment was significantly related with ammonium-N ($NH_4-N$) concentration and pH in the surface water. The correlation coefficients of $NH_3$ volatilization compared to the $NH_4-N$ and pH in surface water were significantly higher in urea than LCU. The $NH_3$ volatilization from both urea and LCU treatments was not increased in surface water of pH less than 8.0, while $NH_3$ volatilization increased significantly in the surface water of pH over 8.0. The results in the field experiment indicated that $NH_3$ volatilization after top-dressing of urea increased rapidly with increasing $NH_4-N$ concentration in soil and floodwater, and highest from 7 to 10 days after top-dressing. The amount of $NH_3$ volatilized from urea treatment was in the range of $4.9-8.4kg\;N\;ha^{-1}$. The variations of $NH_3$ volatilization in 2002 and 2003 were caused by changed N dynamics due to the different weather conditions such as rainfall and temperature. The amount of $NH_3$ volatilized from LCU treatment was significantly reduced compared to that of urea. The reason for the reduced $NH_3$ volatilization in LCU treatment would be due to the lower concentration of $NH_4-N$ in floodwater. The amount of $NH_3$ volatilized from LCU treated rice paddy was in the range of $1.2-1.8kg\;N\;ha^{-1}$, and the loss of N by ammonia volatilization was 2.0-2.3%. Loss of N by $NH_3$ volatilization with LCU treatment was reduced by 75-79% comparing to urea treatment.