Surface application of urea often results in high ammonia volatilization loss. Information on ammonia volatilization

in tropical acid soils is limited. This study was carried out to determine ammonia volatilization loss from surface applied urea in Malaysian soils and to study the ejects of soil properties on the rate of loss. Measurement of urease

activity and ammonia volatilization loss in the laboratory was carried out on topsoil (0-15 cm) of 22 soils commonly

found in Malaysia using a force-draft technique. Ammonia volatilization loss was recorded daily for seven days.

Ammonia volatilization loss from the 22 soils studied ranged from 0.5 to 53% of N applied with most soils having

values around 35 %. The ammonia loss in acid sulfate soil was low. Most of the loss occurred during the first 34

days after urea application. The urease acitivity of soils ranged from 12.20 to 150.50 uglg Nih and was not

affected by soil texture and C content. Urease acitivity had a significant e1Ject on ammonia volatilization los

Yusop, Mohd Khanif

Universiti Putra Malaysia Institutional Repository

Pertanika 15(2),115-120 (1992)Ammonia Volatilization from Malaysian SoilsFollowing Application of UreaYM. KHANIFDepartment of Soil Science, Universiti Pertanian Malaysia43400 UPM, Serdang, Selangor Darul Ehsan, MalaysiaKeywords: N loss, urea transformation, N efficiency.ABSTRAKPenambahan baja urea dipermukaan tanah selalunya menyebabkan kehilangan N melalui pengruapan ammonia.Kajian keatas pengruapan ammonia di tanah tropika adalah kurang. Kajian ini dijalankan untuk menentukankehilangan N melalui pengruapan ammonia bagi tanah di Malaysia dan mengkaji kesan beberapa sifat tanahterhadap kadar kehilangan ini. Penentuan aktiviti urease dan kehilangan pengruapan ammonia ditentukan dimakmal keatas 22 tanah permukaan (0-15 sm) yang biasa terdapat di Malaysia. Penentuan pengruapan ammoniaditentukan dengan menggunakan teknik ''jorce draft". Pengruapan ammonia ditentukan pada tiap-tiap hari selamatujuh hari. Kehilangan pengruapan ammonia daripada 22 tanah yang dikaji adalah pada jul(lt 0.5 hingga 53 %daripada N yang ditambah kebanyakan tanah mempunyai nilai dilingkungan 35 %. Kehilangan pengruapanammonia pada tanah asid sulfat adalah rendah. Sebahagian besar daripada kehilangan berlaku dalam 3-4 hariselepas baja urea ditambah. Aktiviti urease adalah pada julat 12.20 hingga 150.50 uglg Nih dan nilainya tidakdipengaruhi oleh tekstur tanah dan kandungan C. Aktiviti urease memberi kesan yang bermakna terhadapkehilangan pengruapan ammonia.ABSTRACTSurface application of urea often results in high ammonia volatilization loss. Information on ammonia volatilizationin tropical acid soils is limited. This study was carried out to determine ammonia volatilization loss from surface-applied urea in Malaysian soils and to study the ejJects of soil properties on the rate of loss. Measurement of ureaseactivity and ammonia volatilization loss in the laboratory was carried out on topsoil (0-15 cm) of22 soils commonlyfound in Malaysia using a force-draft technique. Ammonia volatilization loss was recorded daily for seven days.Ammonia volatilization loss from the 22 soils studied ranged from 0.5 to 53% ofN applied with most soils havingvalues around 35 %. The ammonia loss in acid sulfate soil was low. Most of the loss occurred during the first 3-4 days after urea application. The urease acitivity of soils ranged from 12.20 to 150.50 uglg Nih and was notaffected by soil texture and C content. Urease acitivity had a significant e1Ject on ammonia volatilization loss.INTRODUCTIONSurface application of urea often results in highammonia volatilization loss which is not only aneconomic loss but is also a serious environmentalproblem. Urea is widely used in the tropics becauseit is a cheap source of N and is easily available.Urea, whel~ added to soils, is rapidly hydro-lysed to (NH4)2COg and subsequently to H40Hand CO., (Bremner and Mulvaney 1978). Thehydrolysfs results in a high pH increase at theurea microsite, which favours liberation of NHg(Ferguson et al. 1984). The magnitude of pH in-crease depends on the soil buffering capacity(Ferguson et at. 1984) while the rate of urea hy-drolysis is influenced by the urease activity(Bremner and Mulvaney 1978). Thus in tropicalsoils although the soil pH is generally low, ammo-nia volatilization can occur in soils with high pHincrease at the urea microsite during urea hy-drolysis.Urease activity and soil buffering capacity arevery important soil properties affecting ammoniavolatilization (Bremner and Mulvaney 1978;Ferguson et at. 1984). Other soil properties suchas cation exchange capacity, soil texture and or-ganic matter content also affect ammoniavolatilization.This study was carried out to determine am-monia volatilization loss derived from surface-YM. KHANIFapplied urea in Malaysian soils and to study theeffect of soil properties on the rate of loss.MATERIALS AND METHODSMeasurement of ammonia volatilization loss wascarried out on topsoils (0-15 ern) of 22 soil series(Table 1). Loss was determined using the force-draft technique described by Fenn and Kissel(1973). Urea at the rate of 400 ug/g was appliedon the soil surface. Soil moisture was maintainedat 30% (w/w). The ammonia evolved was trappedin boric acid containing mixed indicators(bromocresol green and methyl red). The ammo-nia loss was determined daily by titration withstandard HCI for a period of one week. Eachdetermination was replicated three times.Urease activity was determined on all the soilsusing the method described by Tabatabai (1982).In this method the urea remaining 5 h afterapplication at the rate of 1 mg/l0 g soil was usedfor urease activity determination.Soils were analysed for particle size distribu-tion (Day 1973), organic carbon (Nelson andSommers 1982). and pH (Peech 1965).RESULTS AND DISCUSSIONA mmonia LossLoss of ammonia from different soils during thefirst weeks after urea application is presented inTable 2. The loss varied between 0.5 to 52.8%.However, in most soils the loss was around 35%.High ammonia loss was also observed even in soilswith high clay content. Ammonia volatilizationwas generally low in Carey (Sulfic Tropaquept)and Sedu (Typic Sulfaquept) series which areacid sulfate soils. These soils have low pH andhigh buffering capacity, which do not favour ex-cessive ammonia volatilization loss.The volatilization loss obtained in this studymight overestimate losses under field conditionsbecause of the high wind speed used in the force-draft measurement technique (Hargrove et al,1987). These results, however, indicated that thereis a potential for high ammonia volatilization lossin tropical acid soils and this will lead to low ureaN utilization efficiency.Cumulative urea loss by volatilization of am-monia in one week from soils is presented in Fig.116TABLE 1Some properties of the soils usedSoils Sand Clay Organic C pH%Bungor (Typic Paleudult) 66 18 2.21 4.83Munchong (Tropeptic Haplorthox) 54 35 1.39 4.80Serdang (Typic Paleudult) 60 41 1.74 4.70Holyrood (Oxic Dystropept) 72 21 0.80 5.20Prang (Tropeptic Haplorthox) 8 82 1.69 4.61Sedu (Typic Sulfaquept) 17 47 4.58 2.86Carey (Sulfic Tropaquept) 60 19 1.27 3.50Segamat (Haplic Acrorthox) 4 83 2.75 5.14Baging (Typic Quartzipsamment) 98 0 0.43 5.20Kuantan (Haplic Acrorthox) 8 70 1.51 5.50Lanchang (Typic Paleudult) 42 51 2.10 4.70Beserah (Tropeptic Haplorthox) 88 10 2.05 4.97K.Berang (Typic Tropudult) 33 20 1.90 4.25Renggam (Typic Paleudult) 43 21 3.40 4.61Durian (Typic Paleudult) 6 45 1.89 5.39B. Anam (Aquoxic Tropudult) 14 22 1.32 4.40Jerangau (Haplic Acrorthox) 44 48 0.85 4.50Chat (Typic Paleudult) 57 57 1.80 4.70Kuah (Oxic Dystropept) 31 24 1.12 4.50Jitra (Tropeptic Haplorthox) 20 61 3.03 4.94Gajah Mati (Tropeptic Haplorthox) 15 75 3.06 4.50Tai Tak (Typic Paleudult) . 49 38 1.73 4.40PERTANIKA VOL. IS NO.2, ]992AMMO IA VOLATILIZATIO FROM MALAYSIAN SOILS FOLLOW! G APPLICATIO OF UREATABLE 2Total ammonia volatilization and urease acitivity in soilsSoils Ammonia loss* Urease acitivity*':'abxintercept (%)slope (%/day)time (day)1. In most soils maximum loss occurred in thefirst 3-4 days affter urea application and it de-creased subsequently with time. This is becauseurea hydrolysis accompanied by pH increase oc-curred during this period. The soil pH at ureamicrosites increased to a maximum pH of 8 to 9(Khanif and Pancras 1988). At this pH excessiveammonia volatilization will take place. Thus, al-though the pH of the soils studied was low (pH <5), urea hydrolysis could increase soil pH at ureamicrosites sufficiently for ammonia volatilizationto be significant.The total ammonia volatilization loss frommost of the soils could be described by the fol-lowing equation (Table 3):Loss as a percentage of the maximum possibleug Urea-N hydrolysed per g per houra + b Inxammonia volatilization loss(%)BungorMunchongSerdangHolyroodPrangSeduCareySegamatBagingKuantanLanchangBeserahKuala BerangRengamDurianBatuAnamJerangauChatKuahJitraGajah MatiTai Tak**whereyy%14.413.233.049.233.20.516.440.042.433.752.819.328.644.541.640.413.942.330.530.737.445.8ug N/g/h12.1844.3749.61126.90132.6093.6193.61105.20144.2188.13150.5084.9566.7610.0753.1982.6159.1392.4446.0756.1387.8376.11The rate of ammonia loss was initially highbut it decreased with time. The slopes of the linesranged between 6.6 and 23.9% day and variedwith the soil type. The regressions were highlysignificant for most of the soils.Urease ActivityThe enzyme urease is responsible for urea hy-drolysis, a prerequisite for ammonia volatilizationloss. The urease activities of the soils studied arepresented in Table 2, and range from 12.20 to150.50 ug/g Nih. The urease activity was notrelated to sand, clay and carbon content. Thevalues obtained were generally high, thus rapidurea hydrolysis and ammonia volatilization can beexpected in most of the soils studied.TABLE 3Regression equations of ammonialoss as a function of timeSoils Equation R FBungor Y= 0.64 + 7.27 lnx 0.99 27.6 ':'*Munchong Y = 0.03 + 6.67 lnx 0.99 88.9 *':'Serdang y= 8.32 + 15.40 lnx 0.93 24.8 **Holyrood Y= 8.86 + 23.90 lnx 0.91 67.5 **Prang Y= -2.39 + 18.30 lnx 0.97 224.0 **Carey Y = -4.96 + 12.20 lnx 0.78 12.1 ':":'Segamat Y= 8.08 + 20.90 lnx 0.95 97.5 **Baging Y= 2.48 + 16.50 lnx 0.93 80.3 **Kuantan Y= 4.32 + 15.10 Inx 0.97 136.0 *':'Lanchang Y= 18.90 + 19.70 lnx 0.87 34.6 **Beserah Y= 12.20 + 8.36 lnx 0.54 5.3 **KBerang Y= -3.77 + 17.50 lnx 0.92 79.1 **Soil Properties Affecting Ammonia LossSoil properties most likely to affect ammonia losswere included in a stepwise regression to deter-mine their importance in influencing ammoniavolatilization loss. The factors considered wereurease activity, sand, clay and organic carboncontent. The statistical analysis indicated that onlyurease activity had a significant effect on the rateof ammonia volatilization while the other factorswere not significan t (Table 4). Although the sandand clay contents were expected to influenceammonia loss, the effect could not be clearlyPERTANlKA VOL. 15 NO.2, 1992 117YM. KHANIF:-VO::L:.:A::.T:.:'L:.:'Z:..:ATe-'O:.:N'-L:.:O:..:S=S...:.(%:.:)_----:::::::a====~601VOLATILIZATION LOSS ('Jlo)60,----------'----'---------,40VOLATILIZATION LOSS ('lI.j VOLATILlZATTQN LOSS ('Jo)150 40 r-c==---'----'-"-'-=---'---------,I~ Slg.mal -B-1<. Bran; -+ ~ll.h I403030zo~S.rd.nll IDAYS DAYS60 ;.:VO::L:.:A::.T1:.:L:.:'Z::.ATe-'O:.:N...:.L::O::S:::S-'-(%:.:) , ;..:VO~L=A=T'=L'=ZA=T='O=N=L:::O=SS=(%=)====:;--I601 I~ B. Allam -a- J,rall;au -+ Ctllt I4030203DAYS DAYS406014VOLATILIZATION lOSS (%) ;-VO~L=A=T'=L'=ZA=T=rO=N=L:::O=S=S=(%=)===:::;_--116 50 II -e- Bunllor -+ S'du I I -8- Durie" -a- CarlY +- Bailing I40,210 302010o~~,,====~==:=foo,r>"--=="'----~-~-~-~-----'oDAYS DAYSFig 1: A mmonia volatilization from 22 soils after application ofurealIS PERTANlKA VOL. 15 NO.2, 1992AMMONIA VOLATILIZATION FROM MALAYSIAN SOILS FOLLOWlNG APPLICATION OF UREAdemonstrated, most probably due to the presenceof iron coated clay or "pseudo sand" which be-haved like sand. "Pseudo sand" is abundant in allsoils studied but was especially high in the Oxisol.Thus even for soil with a high clay content, highloss of ammonia following urea application oc-curred (Table 2).TABLE 4Summary of regression analysis of ammoniavolatilization loss with urease activity, sand, clay andorganic carbonVariable Partial R Model R FUrease activity 0.2642 0.2642 6.4624*Organic carbon 0.0824 0.3466 2.1435Clay 0.0286 0.3751 0.7317Sand 0.0279 0.4031 0.7021CONCLUSIONSignificant ammonia volatilization loss occurredfrom tropical soils following urea application. Theammonia loss, however, was low in acid sulfatesoils with low pH values. Soil urease activity wassignificantly related to the rate at which ammoniawas volatilized from soil.ACKNO~DGEMENTSThe author thanks Petronas for funding the re-search project.REFERENCESBREMNER, J.M. and R.L. MULVANEY. 1978. Urease Ac-tivity in Soils. In Soil. ed. L. Burns. London:Academic Press. pp. 149-196.DAY, P.P. 1973. Particle Fractionation and ParticleSize Analysis. In Methods of Soil Analysis Part 1.ed. C.A. Black et al. Am. Soc. Agron. (USA) pp.545-567.FENN, L.B. and D.E. KISSEL. 1978. AmmoniaVolatilisation from Surface Application ofAmmonum Compounds in Calcaerous Soils :General Theory. Soil Sci. Soc. Am. Proc. 37:855-859.FERGUSON, R.B., D.E. KiSSEL, J.K. KOELLIKER and W.BASEL. 1984. Ammonia Volatilisation from Sur-face Applied Urea : Effects of Hydrogen IonBuffering Capacity. Soil Science Soc. Am. J. 48:578-582.HARGROVE, W.L., B.R. BOCK, R.A. RAVINlKAR and WJ.URBAN. 1987. Comparison of a Force Draft Tech-nique to 15N Recovery of Measuring AmmoniaVolatilisation under Field Conditions. Soil Sci-ence Soc. Am. J. 51: 124-128.KHANIF, Y.M. and H. PANCRAS. 1988. Urea Transfor-mation in Malaysian Soils. Proc. Int. Symp. onUrea Technology and Utilization. pp. 259-266.NELSON, W.D. and L.E. SOMMERS. 1982. Total Carbon,Organic Carbon and Organic Matter: In Methodsof Soils Analysis. Part 2. ed. A.L. Page et al. 2nded. Am. Soc. Agron (USA) pp. 539-580.PEECH, H.M. 1965. Hydrogen-Ion Activity. In Methodsof Soil Analysis Part 2. ed. CA Black et al. Am.Soc. Agron. (USA) pp. 914-926.TABATARAJ. 1982. Soil Enzymes. In Methods of SoilAnalysis Part 2. 2nd ed. A.L. Page. AmericanSoc. of Agronomy, Wisconsin, pp. 903-948.(Received 20 December 1991)PERTANIKA VOL. 15 NO.2, 1992 119

Ammonia Volatilization from Malaysian Soils

Following Application of Urea

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Ammonia Volatilization from Malaysian Soils Following Application of Urea

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