IMPROVING WHEAT PRODUCTIVITY THROUGH SOURCE AND TIMING OF NITROGEN FERTILIZATION

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1 Pk. J. Bot., 43(2): , IMPROVING WHEAT PRODUCTIVITY THROUGH SOURCE AND TIMING OF NITROGEN FERTILIZATION MOHAMMAD TARIQ JAN 1, MOHAMMAD JAMAL KHAN 2, AHMAD KHAN 1, MUHAMMAD ARIF 1, FARHATULLAH 3, DAWOOD JAN 4, MUHAMMAD SAEED 5 AND MOHAMMAD ZAHIR AFRIDI 1 1 Deprtment of Agronomy, 2 Deprtment of Soil nd Environmentl Sciences, 3 Deprtment of Plnt Breeding & Genetics, 4 Agriculturl Economic, 5 Deprtment of Weed Science, KPK Agriculturl University Peshwr, Pkistn Astrct Efficient nitrogen (N) fertilizer mngement is criticl for the improved production of whet (Triticum estivum L.) nd cn e chieved through source nd timing of N ppliction. Thus, n experiment ws crried out t the Reserch Frm of KPK Agriculturl University Peshwr during to test the effects of sources nd timing of N ppliction on yield nd yield components of whet. Nitrogen sources were mmonium (NH 4 ) nd nitrte (NO 3 ) pplied t the rte of 100 kg h -1 t three different stges i.e., t sowing (S1), tillering (S2) nd oot stge (S3). Ammonium N incresed yield component ut did not ffect the finl grin yield. Split N ppliction t sowing, tillering nd oot stges hd incresed productive tillers m -2, nd thousnd grins weight, wheres grin yield ws higher when N ws pplied t tillering nd oot stges. Nitrogen fertiliztion incresed 20% grin yield compred to control regrdless of N ppliction time. It ws concluded from the experiment tht split ppliction of NH 4 -N performed etter thn full dose ppliction nd/or NO 3 -N for improved whet productivity nd thus, is recommended for generl prctice in gro-climtic conditions of Peshwr. Introduction The chemicl fertilizers re significnt source of redily ville nitrogen (N) to the crops. Due to the greter vilility (Ahmd et l., 1996) nd crucil input for improving crop productivity (Geleto et l., 1995), N is n integrl prt of modern technology for crop production. To increse or mintin productivity without dmging the soil nd the environment, n efficient use of fertilizer through timing, nd sources is required. Nitrogen is often the most limiting nutrient for plnt growth, development nd chievement of yield potentil (Heichel & Brnes, 1984). However, effective mngement of N lso presents greter chllenge to the frmers thn other fertilizer nutrients (Olson & Kurtz, 1982). Nitrogen vilility cn e optimized y its timing, nd efficient strtegies to ensure incresed productivity. N fertiliztion hs een shown to enhnce soil totl N (203%) nd C/N rtio (Htegeril et l., 2007) give n increse of 18% to 34% in residul soil N (Yng et l., 2007), increse soil NO 3 -N (Mlhi et l., 2006), nd increse orgnic N minerliztion y 4.0 to 9.4% (Li et l., 2003) etc. Nitrogen is closely linked to control the vegettive growth of plnt nd hence determine the fte of reproductive cycle. Incresed in nitrogen, numer of spike, grin weight (Rghe et l., 1993; Geleto et l., 1995) nd grin yield (Rghe et l., 1993; Khn et l., 2009) incresed. The sources of chemicl fertilizer hve significnt role in nutrients vilility nd crop productivity. Hewitt (1970) concluded tht nitrte-n (NO 3 - N) is usully superior to mmonium-n (NH 4 -N) for growth ut the two sources my vry

2 906 MOHAMMAD TARIQ JAN ET AL., with species, environmentl conditions nd soil conditions. The NH 4 -N promoted more lef nd stem growth thn NO 3 -N in whet ut did not ffect the yield of grin (Sprtt & Gsser, 1970). The generl conclusion mong reserches hs een tht N should e pplied nerest to the time it is needed y the crop fter emergence (Fox et l., 1986). Generlly, erly fertiliztion incresed whet grin yield, nd lte fertiliztions increse grin protein concentrtion (Fowler & Brydon, 1989). Nevertheless, yield mostly depends on N ccumulted in whet t nthesis nd on N trnsloction efficiency to grin (Srndon et l., 1997). Melj et l., (2003) oserved greter yield components when N ws pplied t tillering compred to sowing. Ayou et l., (1994) stted tht split N hd little effect on yield, ut decresed lodging nd spikes popultion, while grin weight incresed. Ammonium N pplied erly nd NO 3 -N lter would e eneficil culturl prctice for whet production (Sprtt, 1974). However, Lopez-Bellido (2006) did not drw cler conclusion out the grin yield in response to the timing of N ppliction. Severl reserchers hd worked out on the timing of fertiliztion; however, informtion regrding sources of N nd its comintion with time of ppliction is limited in this re. The ojectives of this work were to study the effect of N fertilizer sources nd timing of ppliction on whet productivity. Mteril nd Methods An experiment to determine the effect of different nitrogen sources nd timing of ppliction on yield nd yield components of whet ws crried out t KPK Agriculturl University Peshwr in 2005/2006. The soil used in the experiment ws silty cly lom, well drined nd strongly clcreous, with ph of 8.2. It ws deficient in nitrogen nd phosphorous ut hs dequte potssium. Orgnic mtter ws less thn 1%. The experimentl tretments were consisted of two types of N-fertilizer (NH 4 -N & NO 3 -N) nd three-ppliction time i.e. t sowing, tillering nd oot stge. Ure ws used s minerl-n source for NH 4 -N nd clcium nitrte (CNO 3 ) for NO 3 -N t rte of 100 kg h -1. Comintions of the tretments, including no fertilizer (control) were replicted four times in Rndomized Complete Block (RCB) design. Detils of the experimentl tretments re given in Tle 1. Sowing ws done in Octoer 2005 in plot size of 5 x 3 m hving 30 cm prt 10 rows using trctor-mounted plnter equipped with row clener wheels djusted for 120 kg h -1 seed rte. Phosphorus ws pplied s sl dose t the rte of 60 kg h -1 s single super phosphte (SSP). Uniform gronomic prctices for rising successful crop were followed for ll the tretment. The field ws irrigted fter 21 dys when the germintion ws completed in ll plots. The field ws then irrigted s nd when needed. The dt were recorded on productive tiller m -2, grins per spike, thousnd grin weight nd grin yield. The totl numer of tillers ering spike in rndomly selected three rows of onemeter length in ech plots were counted nd ws converted into productive tillers m -2. Ten rndomly selected spikes were tken from ech experimentl unit nd were threshed. The totl grins fter threshing were counted nd verged ws worked out to record the dt on grins per spike. Thousnd grins were counted from the grin yield of ech experimentl unit nd were weighed to record 1000 grin weight. Centrl four rows were hrvest in ech plot, dried nd threshed seprtely. The grin yield ws recorded nd ws converted into kg h -1 ccordingly.

3 IMPROVING WHEAT PRODUCTIVITY THROUGH NITROGEN FERTILIZATION 907 Tle 1. Detils of the experimentl tretments nd their levels. Type of fertilizer-n Appliction time of fertilizer-n (S1) (S2) (S3) (S1) (S2) (S3) (% of N dose) $ T T2 NH T3 NO T4 0 NH T5 0 NO T6 0 0 NH T7 0 0 NO T8 NH 4 NH T9 NH 4 0 NH T10 0 NH 4 NH T11 NO 3 NO T12 NO 3 0 NO T13 0 NO 3 NO T14 NH 4 NH 4 NH T15 NO 3 NO 3 NO $ = 100 kg N h -1, S1 = t sowing, S2 = t tillering, S3 = t oot stge Dt collected were nlyzed sttisticlly ccording to the procedure relevnt to RCB design. Upon significnt F-test, lest significnce difference (LSD) test ws used for men comprison to identify the significnt components of tretment mens. In ddition to LSD, plnned men comprisons were lso employed for specific ojectives (Jn et l., 2009). Results Productive tiller m -2 : Productive tiller m -2 ws not ffected y sources of nitrogen, however ws incresed with incresing split pplictions of N irrespective of N sources (Tle 2). Within comined mens over N sources, the greter productive tillers m -2 (266) were oserved when N ws pplied in three splits i.e. t sowing, tillering nd oot compred to either full dose t ny stge or in splits t either two stges. Plnned men comprison (Fig. 1) reveled tht N fertiliztion hd incresed the productive tiller compred to control plots. Incorportion of N s full dose during erly period did not vry for productive tiller thn lte ppliction s full dose. However, the split ppliction of N hd incresed productive tillers m -2 compred to full dose. Three split of N hd incresed tiller production potentil thn two splits. Grins per spike: Ammoni N hd more grins per spike compred to those tretments where nitrte N ws pplied (Tle 3). Similrly, mmoni N chieved higher grins per spike when full dose ws pplied t sowing stge compred to oot stge, wheres nitrte N hd higher grin per spike with full dose t oot stge thn erlier ppliction. The split ppliction of N i.e. ½ N t sowing nd other ½ t oot stge hd higher grin per spike (48) thn ll other N ppliction strtegies. Plnned men comprison (Fig. 2) reveled tht fertilized plots hve more grins per spike thn control. Full N ppliction t erly stge produced higher grins per spike thn lte ppliction. Appliction of N whether split or full hd not ffected grins per spike when the dt ws pooled. However, N spilt ppliction t two stges incresed grins per spike compred to three split pplictions.

4 908 MOHAMMAD TARIQ JAN ET AL., Tle 2. Productive tillers m -2 of whet s ffected y sources nd timing of nitrogen fertiliztion. Appliction time/ Fertilizer sources (100 kg N h -1 ) NH 4 -N NO 3 -N Men Full S Full S Full S /2 S1 + 1/2 S /2 S1 + 1/2 S /2 S2 + 1/2 S /3 S1 + 1/3 S2 + 1/3 S Men LSD(0.05) for N sources NS LSD(0.05) for N timing 14 Interction (sources x timing) ** S1= t sowing, S2= t tillering, S3= t oot stge, NS= not significnt, ** = Significnt t 1% level of proility Tle 3. Grins per spike of whet s ffected y sources nd timing of nitrogen fertiliztion. Appliction time/ Fertilizer sources (100 kg N h -1 ) NH 4 -N NO 3 -N Men Full S Full S Full S /2 S1 + 1/2 S /2 S1 + 1/2 S /2 S2 + 1/2 S /3 S1 + 1/3 S2 + 1/3 S Men LSD(0.05) for N sources * LSD(0.05) for N timing 2.2 Interction (sources x timing) ** S1= t sowing, S2= t tillering, S3= t oot stge, *, **= Significnt t 5 nd 1% level of proility, respectively Thousnd grin weight: Appliction of nitrte N hd hevier grins thn NH 4 -N. Grins were hevier when NH 4 -N ws pplied in split compred to full doses (Tle 4). However, full dose of NO 3 -N incresed the grins weight compred to split ppliction. Regrdless of N sources, hevier grins (41.33g) were recoded in plots received three equl split ppliction of N i.e. t sowing, tillering nd oot stges. Plnned men comprisons (Fig. 3) reveled tht control hd lesser thousnd-grin weight thn fertilized plots. Full dose pplied t erlier or lter stge hd not ffected grin weight. Appliction of N s full or split hd no effects on grin weight. However, three-split ppliction hd produced hevier grins to two split ppliction of N.

5 IMPROVING WHEAT PRODUCTIVITY THROUGH NITROGEN FERTILIZATION 909 Productive tillers m Contol Rest Full erly ppliction Full lte ppliction N Full dose N split dose Two split dose Three split dose C1 C2 C3 C4 Plnned men comprisons (C) Fig. 1. Plnned men comprisons for productive tillers m -2 s ffected y sources nd timing of nitrogen. Brs hving similr letter within ech comprison re not significnt. Grins per spike Contol Rest Full erly ppliction Full lte ppliction N Full dose N split dose Two split dose C1 C2 C3 C4 Plnned men comprisons (C) Three split dose Fig. 2. Plnned men comprisons for grins per spike s ffected y sources nd timing of nitrogen. Brs hving similr letter within ech comprison re not significnt. Grin yield: Grin yield ws not significntly ffected y sources of Nitrogen. Across the verge over sources (Tle 5), the mximum grin yield (2965 kg h -1 ) ws recorded in plots received 50 kg N h -1 t tillering stge nd other hlf t oot stge compred to full dose of N ppliction. Plnned men comprison (Fig. 4) reveled tht fertiliztion hd incresed grin yield y 20% compred to control plots. Incorporting full dose of N either erly or lte hd no effects on grin yield. Generlly, the split ppliction of N hd incresed the grin yield compred to full dose of N ppliction. More specificlly, the ppliction of N in two split doses hd incresed the grin yield compred to three split doses.

6 910 MOHAMMAD TARIQ JAN ET AL., Tle 4. Thousnd grins weight (g) of whet s ffected y sources nd timing of nitrogen fertiliztion. Appliction time/ Fertilizer sources (100 kg N h -1 ) NH 4 -N NO 3 -N Men Full S Full S Full S /2 S1 + 1/2 S /2 S1 + 1/2 S /2 S2 + 1/2 S /3 S1 + 1/3 S2 + 1/3 S Men LSD(0.05) for N sources * LSD(0.05) for N timing 2.42 Interction (sources x timing) ** S1= t sowing, S2= t tillering, S3= t oot stge, *, **=Significnt t 5 nd 1% level of proility, respectively Tle 5. Grins yield (kg h -1 ) of whet s ffected y sources nd timing of nitrogen fertiliztion. Appliction time/ Fertilizer sources (100 kg N h -1 ) NH 4 -N NO 3 -N Men Full S Full S Full S /2 S1 + 1/2 S /2 S1 + 1/2 S /2 S2 + 1/2 S /3 S1 + 1/3 S2 + 1/3 S Men LSD(0.05) for N sources NS LSD(0.05) for N timing 168 Interction (sources x timing) NS S1= t sowing, S2= t tillering, S3= t oot stge, NS= not significnt Discussion In the present study, the greter numer of tillers production in fertilized plots cn e ttriuted to the dequte N vilility (Mlhi et l., 2006) which resulted in incresed photosynthetic ctivities (Htegeril et l., 2007), vigorous plnt growth (Kie et l., 2006) nd thus ultimtely incresed the productive tillers. Our results re in line with finding of Wh & Hussin (1997) who reported tht higher tillers production in fertilized plots thn unfertilized nd were confirmed y Jn & Khn (2000). Nitrogen ppliction t vegettive stge improved the plnt growth (Jn & Khn, 2000) nd therey incresed productive tillers. The split ppliction might hve fulfilled the plnt N requirement due to greter vilility of N for prolonged time (Singh & Bhn, 1998) nd thus might hve incresed the productive tillers.

7 IMPROVING WHEAT PRODUCTIVITY THROUGH NITROGEN FERTILIZATION 911 Thousnd grin weight (g) Contol Rest Full erly ppliction Full lte ppliction C1 C2 C3 C4 Plnned men comprisons (C) Fig. 3. Plnned men comprisons for thousnd grin weight (g) s ffected y sources nd timing of nitrogen. Brs hving similr letter within ech comprison re not significnt N Full dose N split dose Two split dose Three split dose Grin yield (kg h -1 ) Contol Rest Full erly ppliction Full lte ppliction 1000 C1 C2 C3 C4 Plnned men comprisons (C) Fig. 4. Plnned men comprisons for grin yield (kg h -1 ) s ffected y sources nd timing of nitrogen. Brs hving similr letter within ech comprison re not significnt. The higher grin per spike due mmoni N might e ttriuted the greter vilility of N due to NH 4 -N compred to NO 3 -N in cerels. Our results re in greement with finding of Kelley & Sweeney (2005). Incresed grin per spike due fertiliztion cn e ttriuted to improved crop performnce in fertilized plots (Ayou et l., 1994), nd tillering potentil (Geleto et l., 1995) or higher nutrient vilility (Gurdip et l., 2001) s compred to control. Improved grins per spike due to erly ppliction of NH 4 -N might e ssocited with greter nd prolonged N vilility (Yng et l., 2007), which might hve synchronized the plnt supply nd demnd nd thus incresed grin per spike. Split ppliction of N hd incresed the ville N (Lopez-Bellido, 2006; Hung et l., 2007) prticulrly t sowing tht enhnced the plnt vegettive stge, or t oot stge tht is ccountle for improving the reproductive stge nd thus incresed the grin per spike. N Full dose N split dose Two split dose Three split dose

8 912 MOHAMMAD TARIQ JAN ET AL., The hevier grins in plots received NO 3 -N might e ssocited with greter positive efficiency of whet to NO 3 -N t ltter stge compred to NH 4 -N (Sprtt, 1974). Improved grin weight in fertilized plots might e ssocited with individul plnt performnce (Herrer et l., 2007), improved plnt photosynthetic cpility (Benziger et l., 1994) or improved lef re (Kie et l., 2006). Our results re in greement with the finding of Song et l., (1998) who reported tht incresed nitrogen ppliction incresed grin weight of whet. The split ppliction of N hd improved the N uptke efficiency (Lopez-Bellido, 2006) or recovery efficiency (Dvies et l., 1979) nd thus incresed the grin weight. In the present study, sources of N hd not ffected the grin yield, the possile reson might e tht oth NH 4 -N nd NO 3 -N fulfilled the crop requirements in similr fshion nd thus might hve resulted in non-significnt differences for grin yield. Our results re in line with Sprtt nd Gsser, 1970 nd were further confirmed y Westermn et l., (1994). Improved whet grin yield over control might e ssocited with higher vilility of N (Kemmitt et l., 2006), enhnced phenology (Khn et l., 2008), improved individul crop performnce (Cmr et l., 2003; Mlhi et l., 2006) or vigorous plnt growth (Kie et l., 2006) in fertilized plots nd thus might hve incresed the grin yield. Our results re in line with the finding of Shfiq et l., (1994) who reported tht fertilizer ppliction incresed grin yield of whet over control nd were confirmed y Dng et l., Split ppliction N etter mtched the crop N needs during growing period (Mercedes et l., 1993) nd thus hs incresed the crop yield. The other possile reson for improved crop yield due to split N ppliction might e the enhnced uptke of N (Limon-Orteg et l., 2000) nd therey incresed crop performnce (Houles et l., (2007) nd ultimtely grin yield. Conclusions nd Recommendtions Appliction of N hd improved the yield nd yield component of whet compred to control. In generl, NH 4 -N performed etter thn NO 3 -N. Split ppliction of N hd performed etter thn sole N ppliction. Keeping in view the ove fcts productivity of whet cn e incresed y using NH 4 -N in either three or two splits pplictions. Acknowledgments Finncil support to conduct this reserch ws provided y Pkistn Agriculturl Reserch Council under ALP project. References Ahmd, N., M. Rshid nd A.G. Ves Fertilizers efficiency. p.166. In: (Eds.): N. Ahmd, M. Rshid nd A.G. Ves. Fertilizers nd their use in Pkistn. NFDC Pul. 4/96, Islmd. Ayou, M., S. Quertin, S. Lussier nd D.L. Smith timing nd levels of nitrogen fertility effects on whet yield in Estern Cnd. Crop Sci., 34: Bnziger, M., B. Feil nd P. Stmp Competition etween nitrogen ccumultion nd grin growth for crohydrtes during grin filling of whet. Crop Sci., 34: Dng, T.H., G.X. Ci, S.L. Guo, M.D. Ho nd L.K. Heng Effect of nitrogen mngement on yield nd wter use efficiency of rinfed whet nd mize in Northwest Chin. Pedospher. 16: Dvies, D.B., L.V. Vidynthn, J.S. Rule nd R.H. Jrvis Effect of sowing dte nd timing nd level of nitrogen ppliction to direct drilled winter whet. Expt. Hus., 35:

9 IMPROVING WHEAT PRODUCTIVITY THROUGH NITROGEN FERTILIZATION 913 Fowler, D.B nd J. Brydon No-till winter whet production on the Cndin prctices: timing of nitrogen fertiliztion. Agron. J., 81: Fox, R.H., J.M. Kern nd W.P. Pickielek Nitrogen fertilizer source nd method nd time of ppliction effects on no-till corn yields nd nitrogen uptke. Agron. J., 78: Geleto, T., D.G. Tnner, T. Mmo nd G. Geeyehu Response of rinfed red nd Durum whet to source, level nd timing of nitrogen fertilizer on two Ethiopin vertisols. 1. yield nd yield components. Commun. Soil Sci. nd Pl. Anl., 26(11-12): Gurdip, K., D.S. Kler, S. Srjeet, G. Kur nd S. Singh Effect of plnting techniques t higher nitrogen nutrition on tiller count PAR interception, soil temperture, grin yield nd yield ttriuting chrcters of whet. Environ. nd Ecol., 19(2): Htegeril, K., B.R. Singh nd M. Hile Impct of tillge nd nitrogen fertiliztion on yield, nitrogen use efficiency of tef (Ergrostis tef (Zucc.) Trotter) nd soil properties. Soil nd Tillge Res., 94: Heichel, G.H. nd D.K. Brnes Opportunities for meeting crop nitrogen needs from symiotic nitrogen fixtion. p In: (Ed.): D.F. Bezdicek et l., Orgnic frming: Current technology nd its role in sustinle griculture. Specil Puliction No. 46. ASA, Mdison, WI. Herrer, J.M., P. Stmp nd M. Liedgens Inter-nnul vriility in root growth of spring whet t low nd high nitrogen supply. Eur. J. of Agron., 26: Houles, V., M. Guerif nd B. Mry Elortion of nitrogen nutrition indictor for winter whet sed on lef re index nd chlorophyll content for mking nitrogen recommendtions. Eur. J. of Agron., 27: Hung, B., W. Sun, Y. Zho, J. Zhu, R. Yng, Z. Zou, F. Ding nd J. Su Temporl nd sptil vriility of soil orgnic mtter nd totl nitrogen in n griculturl ecosystem s ffected y frming prctices. Geoderm, 139: Jn, M.T. nd S. Khn Response of whet yield components to type of N fertilizer, their levels nd ppliction time. Pk. J. Biol. Sci., 3(8): Jn, M.T., P. Shh, P.A. Hollington, M.J. Khn nd Q. Sohil Agriculture Reserch: Design nd Anlysis. Dept. of Agronomy, KPK Agric. Uni. Peshwr, Pkistn Kelley, K.W. nd D.W. Sweeney Tillge nd ure mmonium nitrte fertilizer rte nd plcement ffects winter whet following grin sorghum nd soyen. Agron. J., 97: Kemmitt, S.J., D. Wright, K.W.T. Goulding nd D.L. Jones ph regultion of cron nd nitrogen dynmics in two griculturl soils. Soil Biol. nd Biochem., 38: Khn, A., M.T. Jn, K.B. Mrwt nd M. Arif Orgnic nd inorgnic nitrogen tretments effects of plnt nd yield ttriutes of mize in different tillge system. Pk. J. of Bot., 41: Khn, A., M.T. Jn, M. Arif, K.B. Mrwt nd A. Jn Phenology nd crop stnd of whet s ffect y nitrogen sources sujected to different tillge prctices. Pk. J. of Bot., 40: Kie, A.M., S. Singh nd N. Klr Wter nitrogen reltionships for whet growth nd productivity in lte sown conditions. Agric. Wter Mnge., 84: Li, H., Y. Hn nd Z. Ci Nitrogen minerliztion in pddy soils of the Tihu Region of Chin under neroic conditions: dynmics nd model fitting. Geoderm, 115: Limon-Orteg, A., K.D. Syre nd C.A. Frncis Whet nitrogen use efficiency in ed plnting system in northwest mexico. Agron. J., 92: Lopez-Bellido, L., R.J. Lopez-Bellido nd F.J. Lopez-Bellido Fertilizer nitrogen efficiency in durum whet under rinfed Mediterrnen conditions: Effect of split ppliction. Agron. J., 98: Mlhi, S.S., R. Lemke, Z.H. Wng nd B.S. Chhr Tillge, nitrogen nd crop residue effects on crop yield, nutrient uptke, soil qulity nd greenhouse gs emissions. Soil nd Tillge Res., 90: Melj, M.A., H.E. Echeverri, S.C. Lopez, G. Studdert, F. Andrde nd N.O. Brro Timing of nitrogen fertiliztion in whet under conventionl nd no-tillge system. Agron. J., 95:

10 914 MOHAMMAD TARIQ JAN ET AL., Olson, R.V. nd L.T. Kurtz Crop nitrogen requirement, utiliztion nd fertiliztion. p In: (Ed.): F.J. Stevenson Nitrogen in griculturl soils. ASA, Mdison, WI. Rghe, H.M., R.A. Dwood nd K.A. Kheirll Nitrogen uptke nd utiliztion y whet cultivrs grown under sline stress. Aust. J. Agric. Sci., 24: Srndon, S.J. nd D.O. Cldiz Effects of vrying nitrogen supply t different growth stges on nitrogen uptke nd nitrogen prtitioning efficiency in two whet cultivrs'. Fertilizer Res., 22(1): Shfiq, M., A. Hssn, N. Ahmd nd A. Rshid Crop yields nd nutrient uptke y rinfed whet nd mungen s ffected y tillge, fertiliztion nd weeding. J. Pl. Nutr., 17(4): Singh, S nd V.M. Bhn Response of whet (Triticum estivum L.) nd ssocited weeds to irrigtion regime, nitrogen nd 2,4-D. Ind. J. Agron., 43(4): Song, Y., F.M. Yun, Z.H. Yo nd Y.L. Song A fixed loction study on the effect of different comintions of fertilizers on iologicl chrcters nd yield of winter whet. Soils nd Fert. Beijing., 1: Sprtt, E.D The effect of mmonium nd ure phosphte with nd without nitrifiction inhiitor on growth nd nutrient uptke of whet. Soil Sci. Soc. Amer. Proc., 37: Sprtt, E.D. nd J.K.R. Gsser Effect of mmonium nd nitrte forms of nitrogen nd restricted wter supply on growth nd nitrogen uptke of whet. Cn. J. Soil Sci., 50: Wh, A nd I. Hussin Effect of nitrogen on growth, qulity nd yield of irrigted whet. Srhd J. Agric., 1(2): Westermn Roert L., Rndl K. Bomn, Willim R. Run nd Gordon V. Johnson Ammonium nd Nitrte Nitrogen in Soil Profiles of Long-Term Winter Whet Fertiliztion Experiments. Agron. J., 86(1): Yng, J.Y., E.C. Huffmn, R.D. Jong, V. Kirkwood, K.B. McDonld nd C.F. Drury Residul soil nitrogen in soil lndscpes of Cnd s ffected y lnd use prctices nd Agriculturl policy scenrios. Lnd Use Policy, 24: (Received for puliction 15 My 2009)