Americn-Eursin J. Agric. & Environ. Sci., 9 (3): 3-38, ISSN 88-6769 IDOSI Pulictions, Quntittive nd Qulittive Yield of Potto Tuer y Used of Nitrogen Fertilizer nd Plnt Density Roghyyeh Zihi-e-Mhmoodd, Shhzd Jmti-e-Somrin, Mjid Khytnezhd nd Roz Gholmin Young Reserchers Clu, Islmic Azd University, Ardil Brnch, Ardil, Irn Astrct: In order to investigte of quntittive nd qulittive yield of potto tuer cultivr Agri, y pplying nitrogen fertilizer levels nd plnt density fctoril experiment sed on rndomized complete lock design ws conducted with three replictions, Ardil, Irn. Fctors were nitrogen levels (, 8, 6 nd kg h net nitrogen) nd plnt densities (5.5, 7.5 nd plnt m ). Results showed tht the most nitrogen uptke y plnt eril prts nd the most nitrte concentrtion in dry nd fresh tuer weight were oserved t kg h nitrogen, plnt m nd kg h nitrogen, 5.5 plnt m, respectively. At 6 kg h nitrogen (s equl to 8 kg h nitrogen) nd plnt m, the most tuer nd yield were gined. With incresing nitrogen ppliction up to 6 kg h, nitrogen uptke y tuer, numer of tuer nd men tuer weight ws incresed. The highest nitrogen percent of tuer nd men tuer weight ws chieved using 8 kg h long with 5.5 plnt m. The highest phosphorus nd copper uptke y tuer ws oserved t 8 kg h nitrogen nd density of 7.5 plnt m. With incresing nitrogen ppliction up to kg h nd densities of 7.5 nd plnt m, the highest uptke of clcium nd potssium ws done, respectively. So, tretment of 8 kg h - nitrogen nd plnt m in order to gin tuers hving high edile qulity nd high yield long with the lowest nitrte ccumultion is recommended. Key words: Nitrte NPK Plnt density Nitrogen uptke nd Potto INTRODUCTION Potto (Solnom tuerosum L.) is clssified s tuer crops which hs importnt impct on humn feeding nd in terms of high yield per unit re, energy content nd produced protein, is superior to whet nd rice []. The fte of nitrogen fertilizers used in potto production is n importnt environmentl concern []. Nitrogen is n essentil element for plnt growth nd is min prt of proteins. When plnt grows up in unfvorle environmentl conditions, protein production is reduced nd nitrogen ccumultes s non-protein compounds. Belnger et l. [3] reported tht estimtion of optimum fertilizer rtes is of interest ecuse of growing economic nd environmentl concerns. Usully, there is close reltionship etween light intensity nd nitrte reduction in green leves. Also, nutrient elements deficit hs importnt effect on nitrte ccumultion. With incresing nitrogen ppliction nd plnt density, potto yield increses [4]. Plnt density in potto ffects some of importnt plnt trits such s totl yield, tuer size distriution nd tuer qulity [5]. Hse et l. [6] found tht tuer N uptke nd nitrte concentrtion were significntly influenced y mounts of nitrogen fertilizer. Also, nitrogen uptke increses numer of tuer, tuer weight, qulittive nd quntittive spects of tuer. But, over-usge of nitrogen delys tuer growth nd reduces its qulittive nd quntities spects. The role of nutrient elements in plnts involves: cell osmotic potentil controlling, cell constructive component, PH djustment, cell memrne penetrility djustment nd ctlytic imiitions ctivity [7]. Over-ppliction of nitrogen, results in decrese in ph, se sturtion nd lck of clcium, mgnesium nd potssium. Also, this cn led to increse in potssium to clcium rtio [8]. As we know, potto, like other plnts, needs ll the elements to growth nturlly ut in soils without trce elements deficit, potto tuer yield, ssocites with the presence of elements N-P-K nd its requirement to the two lter elements is much more thn nitrogen nd there re vrious evidences indicting impct of potssium nd phosphorous on physiologicl spects of potto [8], ut on ccount of ccumultion of ville clcium nd phosphorous in the mjority of soils, fields receiving Corresponding Author: Shhzd Jmti-e-Somrin. Young Reserchers Clu, Islmic Azd University, Ardil Brnch, Ardil, Irn, Tel: +989459449, E-mil: jmti_36@yhoo.com. 3
Am-Eurs. J. Agric. & Environ. Sci., 9 (3): 3-38, dvised mounts of the mentioned elements, generlly, do MATERIALS AND METHODS not response to the excessive vlues of clcium nd phosphorous so, nitrogen is most limiting element for In order to investigte of quntittive nd qulittive potto plnt [7]. The rte of pplied nitrogen fertilizers is yield of potto tuer, Agri cultivr, fctoril experiment key fctor in soil fertility mngement, s its over-usge sed on rndomized complete lock design with three cn dely plnt mturity nd directs dry mtter storge replictions ws conducted t the reserch field of into eril prts rther thn tuers [9]. Belnger et l. [3] University of Mohghegh Ardili, Ardil, Irn, with found tht ppliction of pproprite mounts of nitrogen longitude of 48 5' nd ltitude of 38 5' in 8. Ardil (8 kg h ) resulted in more fvorle effects thn higher region hs very cold winters, riny spring, dry nd wrm rtes. Wddell et l. [] nd Seidi et l. [, ] reported summers nd with men precipittion of 4 mm yerly. tht ppliction of nitrogen, led to increse in tuer yield First fctor ws nitrogen levels (, 8, 6 nd kg h ) thn control. This rte hs een otined 34.3% y nd second ws plnt densities (5.5, 7.5 nd plnt m ). Mrguerite et l. [3]. Mher [4] reported tht with Nitrogen ws given s ure t stges nmely, plnting incresing plnt density, men tuer weight decresed dte nd dte of erthing up. According to soil nlysis nd in low densities, numer of hrvested tuers, ws results, totl nitrogen content ws.56% nd soil texture decresed. Incresing plnt density led to men tuer ws sndy-lom. Bsed on soil test from depth of -3 cm, weight decrese nd numer of tuer nd yield per unit totl sturted electricl conductivity (TSEC) ws 3.68 re, increse [5]. Increment of plnt density decreses mmhos cm, soil PH ws 8.9, totl nitrogen ws.56% men tuer size proly ecuse of plnt nutrient nd soil texture ws lomy snd. Rows were spced 6 cm elements reduction, increment of interspecies competition to ech other nd plots contined 6 rows ech 3 meters. nd lrge numer of tuers produced y high numers of In order to prevent nitrogen effects in djcent plots stems [6]. Mrguerite et l. [3] showed tht the men (order effects),.5 meter order ws mde. Tuers of 6- mximum increse in totl tuer yield, generted y N 7 grms were sown on 3 My 8. Sowing depth ws fertiliztion ginst the zero-n tretment, ws 34.3% nd -3 cm. The lst hrvest ws ssigned to yield. To rnged from.5% to 54.7% nd in regrd to potto, the promote storge cpility, ten dys prior to hrvest, improvement of N efficiency should e lso chieved y eril prts were removed []. Smpling ws done from splitting N fertilizer pplictions nd y monitoring the m plot re, then, tuers were trnsferred to the crop N needs to mtch crop N requirements nd minerl N lortory. Before mesurements were done, tuers were supply throughout the growing seson. Joern nd Vitosh wshed long with roots nd stolons. Different plnt [7] indicted tht incresing nitrogen vlues resulted in tissues were dried seprtely for 48 hours t 75 C nd increse of tuer nitrte concentrtion. Georgkis et l. weighed. In order to clculte totl nitrogen percent of [8] concluded tht y incresing plnt density, the tuer tuer, Kjeldhl method ws used. After tht, tuers were yield ws incresed. Krfyllidis et l. [9] reported tht dried nd turned into sh t 5 C, different elements were plnt density strongly ffected yield, oth y numer nd mesured. Clcium vi titrtion, phosphorous using y weight nd more tuers nd yield per squre meter spectrophotometer, potssium using flme photometer were expected in higher plnt densities. Wds et l. [] nd copper using tomic sorption devices (PerkinElmer, reported tht, with incresing the level of nitrogen model: 64) were clculted. fertiliztion, the nitrte content of tuer ws incresed nd Before mesurements, tuers were wshed long with higher pplictions of nitrogen, cused higher nitrte roots nd stolons. Different plnt tissues were dried content in tuers, too. seprtely for 48 hours in 75 C nd weighed. Tuer nitrte Since, over-ppliction of nitrogen in potto ccumultion ws clculted y sulfoslicylic cid method cultivtion results in decrese in tuer qulity, exposure using spectrophotometer device (Cecile, Frnce). of humn helth to the risk s well s environmentl Clcultion of nitrogen uptke rte ws mde ccording to ccumultion s, the ojective of this work ws to Study of the Hshemidezfooli et l. [9]: NEU= DM EC where: nutritionl qulity nd yield of potto tuer cultivr Agri, NEU = nutrient element uptke, DM = dry mtter nd y pplying nitrogen fertilizer levels nd plnt density nd EC= element concentrtion. Results were nlyzed y determine the est nitrogen rtes to get the highest yield SAS softwre, men comprisons were done vi Duncn's nd qulity of potto tuer long with the lowest multiple rnge test nd grphs were drwn y Excel environmentl ccumultion. softwre. 3
Am-Eurs. J. Agric. & Environ. Sci., 9 (3): 3-38, RESULTS AND DISCUSSION Nitrogen nd Clcium Percent of Tuer: Nitrogen (P<.5) nd clcium (P<.) percent were Nitrogen Uptke: Results showed tht simple effects of significntly ffected y plnt density nitrogen plnt density nd nitrogen level on nitrogen uptke y level interction effect. While 6 kg h nitrogen long eril prts nd tuers (P<.) nd interction effects of with the 5.5 plnt m tretments ws employed, the plnt density nitrogen level (P<.5) only for nitrogen highest nitrogen percent of tuer ws otined. In uptke y eril prts, were significnt. Since, incresing contrst, tretments of nd kg h nitrogen s well nitrogen ppliction led to over growth of eril prts nd s 5.5 plnt m, led to the lowest one (Fig 5). Since, t consequently, increses of leves nd stems dry weight, kg h nitrogen ppliction, the highest mounts of so, it incresed nitrogen uptke. The most nitrogen ws this element hve een spent to increse the growth of uptken t kg h nitrogen nd the less t control leves nd stems rther thn tuers so, yield hs level, for ll eril prts. But in tuer, it ws incresed up decresed. But in tretment of 6 kg h nitrogen, the to 6 kg h nd then, decresed. Increment of density highest yield hs een gined. This shows tht incresed dry mtter of eril prts per unit re. This led tuers hve more used nitrogen nd hence, nitrogen to more nitrogen uptke in eril prts nd tuers so, the percent of tuer hs een more thn other tretments. most nd the fewer uptkes were oserved in nd 5.5 Increse in pplied nitrogen hs led to increse in plnt m. With incresing plnt density nd constnt rte clcium percent of tuer so tht, t kg h nitrogen of ville nitrogen, competition for nitrogen, incresed. long with the 7.5 plnt m, the highest rte ws In kg h nitrogen nd plnt m tretments, the oserved ut, in tretment of 8 kg h nitrogen s well most uptkes nd in 8 kg h nitrogen nd 5.5 plnt m, s 5.5 plnt m, the lowest vlue ws otined (Fig 6). the fewer uptkes were oserved (Figs nd ). Hse Koochki nd Srmdni [8] hve reported the sme et l. [6] reported tht with incresing N ppliction, results, s well. nitrogen uptke in tuer ws incresed nd it is in ccordnce with our work. Also, they reveled more Phosphorous nd Potssium Percent of Tuer: nitrogen uptke y tuer in cse of incresed nitrogen. Phosphorous content of tuer ws ffected (P<.5) Since, nitrogen uptke in tuer per unit re incresed s y nitrogen nd interction effect of plnt density result of plnt density nd nitrogen level increment, so nitrogen level (P<.). With incresing nitrogen rtes this increse, hs ffected positively tuer yield nd yield (over the 8 kg h ), phosphorous content of tuer ws components nd proly, the est reson to yield decresed. As shown in results, the highest phosphorous increment. content ws chieved in 8 kg h nitrogen tretment nd the lowest rte ws otined t levels of 6 nd Nitrte Accumultion: Simple effect of plnt density nd kg h nitrogen. Also, it ws oserved tht y nitrogen nd their interction effect on tuer nitrte ppliction of 8 kg h nitrogen in density of 7.5 plnt ccumultion sed on dry weight (P<.) nd fresh m, the highest vlue of phosphorous ws resulted. In weight (P<.5) ws significnt. With incresing nitrogen contrst, the lowest ones were chieved y ppliction level, nitrte content in tuer dry nd fresh weight of, 6 nd kg h nitrogen t 7.5 plnt m level significntly incresed. More nitrte content in tuer, s (Fig 7). Clerly it ws oserved tht with incresing result of increse nitrogen ppliction, hs een nitrogen usge, phosphorous content ws decresed reported y Wds et l. []. Increse of density, so tht, t the first level of nitrogen, the highest rte reduced tuer nitrte ccumultion, s well. Perhps, this of phosphorous ws tken up. Increse in nitrogen is ecuse of low fertilizer distriution etween the lrge ppliction hd more significnt impct on potssium numer of plnts nd consequently, the tuers. In kg percent of tuer thn control. At the control level, the - h nitrogen nd 5.5 plnt m, the most nitrte lowest rte of this trit ws otined ut t the other three ccumultion in fresh nd dry weight, ws oserved levels, the highest vlues were resulted. In terms of (Figs 3 nd 4). In ll nitrogen levels, Agri cu. hs plnt density, it cn e sid tht densities of 7.5 nd ccumulted the less nitrte rte in oth fresh nd dry plnt m resulted in the highest mount of potssium tuer weight. Also, it could e found tht nitrogen usge content ut density of 5.5 plnt m led to lowest one. over the fvorite rnge either cused to yield reduction or, According to the interction effects (Fig 8), sme to incresed nitrte ccumultion in tuer. the simple effects, tretment done s kg h 3
Am-Eurs. J. Agric. & Environ. Sci., 9 (3): 3-38, 3 5 5 c c d 5 8 6 5.5 7.5 Nitrogen fertilizer levels (kg h-) Plnt density ( Fig. : Effect of nitrogen nd plnt density on nitrogen uptke y tuer. 5.5 7.5 3 5 5 5 8 6 Nitrogen fertilizer levels (kg h-) Fig. : Interction effects of plnt density nitrogen on nitrogen uptke y shoot. 5.5 7.5 4 35 3 5 5 5 8 6 Nitrogen fertilizer levels (kg h-) Fig. 3: Interction effects of plnt density nitrogen on nitrte ccumultion in dry weight. 5.5 7.5 8 7 6 5 4 3 8 6 Nitrogen fertilizer levels (kg h-) Fig. 4: Interction effects of plnt density nitrogen on nitrte ccumultion in fresh weight. 33
Am-Eurs. J. Agric. & Environ. Sci., 9 (3): 3-38, 5.5 7.5.6.4..8.6.4. 8 6 Nitrogen fertilizer levels (kg h-) Fig. 5: Interction effects of plnt density nitrogen on nitrogen percent of tuer. 5.5 7.5.5.5.5 8 6 Nitrogen fertilizer levels (kg h-) Fig. 6: Interction effects of plnt density nitrogen on clcium percent of tuer. 5.5 7.5 Tuer P (%).5.45.4.35.3.5..5..5 8 6 Nitrogen fertilizer levels (kg h-) Fig. 7: Interction effects of plnt density nitrogen on phosphorous percent of tuer. 5.5 7.5 3.5.5.5 8 6 Nitrogen fertilizer levels (kg h-) Fig. 8: Interction effects of plnt density nitrogen on potssium percent of tuer. 34
Am-Eurs. J. Agric. & Environ. Sci., 9 (3): 3-38, 5.5 7.5 5 5 5 8 6 Nitrogen fertilizer levels (kg h-) Fig. 9: Interction effects of plnt density nitrogen on copper percent of tuer. 4 35 3 5 5 5 8 6 5.5 7.5 Nitrogen fertilizer levels (kg h-) Plnt density (pl Fig. : Effect of nitrogen nd plnt density on men tuer weight. 8 6 4 8 6 5.5 7.5 Nitrogen fertilizer levels (kg h-) Plnt density (pl Fig. : Effect of nitrogen nd plnt density on numer of tuer. Tuer yield (g m- 35 3 5 5 5 8 6 5.5 7.5 Nitrogen fertilizer levels (kg h-) Plnt density (pl Fig. : Effect of nitrogen nd plnt density on tuer yield. 35
Am-Eurs. J. Agric. & Environ. Sci., 9 (3): 3-38, nitrogen plnt m density cused the highest rte of resulted in increse in numer of tuer so tht; densities this trit ut other tretment, kg h nitrogen 5.5 plnt of 7.5 nd plnt m jointly were t highest vlue nd m, resulted in the lowest rte. Mhmoodi nd Hkimin 5.5 plnt m plced fterwrds (Fig ). Increse in [] found tht increse in nitrogen ppliction, leds to numer of tuer occurred s result of increse in numer increse in potssium content of tuer. This finding is in of stolon nd increse in density, Incresing stolons, ccordnce with our results on this element. eventully incresed tuer yield. It is ovious tht with incresing plnt numer, numer of stems grown from the Copper Percent of Tuer: Amount of this element ws plnted tuers nd consequently, numer of produced ffected y effects of nitrogen fertilizer, plnt density nd tuers per stem, is incresed. Thus, increse in plnt interction effect of nitrogen level plnt density density leds to increse in produced tuers []. (P<.). Over ppliction of this element (over the 8 kg h ) led to decrese in copper content of tuer nd its Tuer Yield: Effect of plnt density nd nitrogen level highest nd lowest rtes ws oserved t 8 kg h nd ws significnt (P<.) on tuer yield. Results showed kg h (equl to control) nitrogen, respectively. Also, tht increse in nitrogen rtes up to fvorite point led to increse in plnt density, led to increse in this element so increse in tuer yield per unit re. This result hs een tht, the highest vlues were chieved in densities of reported y Oski et l [5] nd Georgkis et l.[8]. The nd 7.5 plnt m ut the lowest one ws otined in highest vlues of this trit ffected y nitrogen were density of 5.5 plnt m. In terms of interction effect, the otined t 8 nd 6 kg h nitrogen nd the lowest highest copper percent of tuer ws resulted in tretment one ws elonged to control. With incresing nitrogen of 8 kg h - nitrogen 7.5 plnt m density while, the ppliction, numer of stolons, numer of tuers nd lowest vlue ws oserved in 6 kg h nitrogen 5.5 consequently, yield were incresed. This my ttriutle plnt m density (Fig 9). to the fct tht in such conditions, vegettive growth of the eril prts cn increse nd hence, inhiit trnsferring Men Tuer Weight: Effect of nitrogen (P<.) nd plnt photosyntheticlly mtters into the storge prts (tuers). density (P<.) ws significnt on men tuer weight. Mrguerite et l. [3] nd Alm et l. [] reveled tht With incresing nitrogen up to definite point, this trit tuer yield per unit re ws incresed with incresing ws incresed so tht, the highest vlue ws otined y nitrogen fertilizer up to suitle level. Also, increse in ppliction of 6 kg h nitrogen. Menwhile, control density led to significnt increse in tuer yield so tht, nd kg h rtes hd significnt effect on men tuer the most nd the lest tuer yield ws chieved t plnt weight. Also, it ws seen tht the lowest men tuer m nd t 5.5 nd 7.5 plnt m, respectively (Fig ). weight ws chieved t 7.5 nd plnt m nd the According to the Arsenult et l. [4], in high densities, highest one ws chieved t 5.5 plnt m (Fig ). numer of tuer nd yield of potto is incresed. As we Increse in density proly cuses the increse in know, this crop needs to erth up to produce remrkle competition etween nd within plnts nd hence, leds tuer yields so, in higher densities, lower distnces re to decrese in vilility of nutrients to ech plnt nd provided for tuers nd hence, smller tuers cn e consequently, results in decline of men tuer weight [9]. produced. But generlly, tuer yield per unit re ws It seems tht except for the competition, potto plnt incresed s result of more produced tuers. ssigns more stored mters into the stems nd leves rther thn tuers under high vegettive sttus. Applied CONCLUSION nitrogen less ffects numer of tuer ut more ffects tuer size nd increses it nd directly increses men Generlly, it cn e sid tht since mjority of trits tuer weight ut in cse of excessive rtes of nitrogen, such s phosphorus, potssium nd cupper content of men tuer weight is decresed [8]. tuer hd the highest vlues t the level of 8 kg h nitrogen nd levels of 8 nd 6 kg h nitrogen were in Numer of Tuer: Numer of tuer per unit re for the sme group in terms of producing yield, numer of nitrogen level nd plnt density ws significnt (P<.5). tuer nd men tuer weight nd lso, increse in plnt Nitrogen level up to definite point hd the incrementl density cused the highest mounts of potssium, cupper effect on this trit nd then, led to decrese in it. nd tuer yield. The most mount of nitrte in dry nd Khjehpour [] pproved increse in numer of tuer with fresh weight of tuer ws oserved in kg h incresing nitrogen fertilizer. Increse in plnt density nitrogen, 5.5 plnt m tretments. Nitrte ccumultion t 36
Am-Eurs. J. Agric. & Environ. Sci., 9 (3): 3-38, 8 nd 6 kg h net nitrogen ws 7.5 nd 4.47 mg 8. Koochki, A. nd G.H. Srmdni,. Physiology - kg tuer dry weight nd 38.88 nd 5.8 mg kg tuer of crop plnts (trnsltion). Jehd Dneshghi fresh weight, respectively. At these nitrogen levels especilly 8 kg h, nitrte ccumulted ws lower thn criticl rnge so, ppliction of 8 kg h nitrogen to gin most tuer yield with less nitrte ccumultion in tuer, is recommended for Agri cu. in Ardil region. Noticing men tuer yield in Ardil region of 8.7 t h nd its comprison with yield of 8 nd 6 kg h nitrogen tretment (9.44 nd 3.74 t h, respectively), it seems tht cn e recommended for this region. so, ppliction of 8 kg h nitrogen long with the density of plnt m in order to gin the highest tuer yield hving the most suitle edile qulity per unit re in ddition to decrese in environmentl ccumultion s nd costs, is recommended for this cultivr. REFERENCES. Khjehpour, M., 6. Production of industril plnts. Jehd-e-Dneshghi Isfhn press. Isfhn. Irn. 58: ISBN 96-6-63-9.. Meyer, K.M.,. Impct of nitrogen mngement strtegies on yield, N-use efficiency nd rhizoctoni diseses of Irish potto. M.S thesis. Fculty of North Crolin Stte University. A thesis sumitted to the Grdute Fculty of North Crolin Stte University in prtil fulfillment of the requirements for the Degree of Mster of Science. 3. Belnger, G., J.R. Wlsh, J.E. Richrds, P.H. Milurn nd N. Zidi,. Comprison of Three Sttisticl Models Descriing Potto Yield Response to nitrogen Fertilizer. Agron. J., 9: 9-98. 4. Arsenult, W.J., D.A. Lelnc, G.C.C. Ti nd P. Boswll,. Effect of nitrogen ppliction nd seed piece spcing on yield nd tuer size distriution in eight potto cultivrs. The Potto Assocition of Americ. Generl Astrcts Not th Presented t the 85 Annul Meeting, 78: 3-39. 5. Smuel, Y.C., D. Essh, G. Holm nd J.A. Delgdo, 4. Yield nd qulity of two U.S. Red Pottoes: Influence of nitrogen rte nd plnt density. th Proceedings of the 4 Interntionl Crop. Sci.Congress Brisne, Austrli, 6 Sep- Oct 4. 6. Hse, T., C. Schuler nd J. He, 7. The effect of different N nd K sources on tuer nutrient uptke, totl nd grded yield of pottoes (Solnum tuerosum L.) for processing. Euro. J. Agron., 6: 87-97. 7. Fgeri, N.K., V.C. Bligr nd C.A. Jones, 99. Growth nd Minerl Nutrition of Field Crops. New York: Mrcel Dekker press. pp: 4. Mshhd press. Mshhd. Irn. pp: 63. 9. Hshemidezfooli, A., A. Koochki nd M. Bnynvvl, 998. Crop plnt improvement (trnsltion). Jehd Dneshghi Mshhd press. Mshhd. Irn, pp: 35.. Wddell, J.T., S.C. Gupt, J.F. Moncrief, C.J. Rosen nd D.D. Steele, 999. Irrigtion nd Nitrogen Mngement Effects on Potto Yield, Tuer Qulity nd Nitrogen Uptke. Agron J., 9: 99-997.. Seidi M., A. Toeh, Y. Rei, A. Roohi, Sh. Jmti-e- Somrin nd M. Hssnzdeh, 9. Evlution of tuer size nd nitrogen fertilizer on nitrogen uptke nd nitrte ccumultion in potto tuer. Res. J. Environ. Sci., 3(3): 78-84.. Seidi, M., A. Toeh, Y. Rei, M. Hssnzdeh Sh. Jmti-e-Somrin nd A. Rohi, 9. Investigtion of tuer size nd nitrogen fertilizer on nitrogen use efficiency nd yield of potto tuer, cultivr Agric. Res. J. Environ. Sci., 3(): 88-95. 3. Mrguerite, O., G. Jen-Pierre nd L. Jen-Frncois, 6. Threshold Vlue for Chlorophyll Meter s Decision Tool for Nitrogen Mngement of Potto. Agron. J., 98: 496-56. 4. Mher, M.J., 998. The effect of plnting density on the production of potto minituer under protection. Proceedings of the Agriculturl Reserch Forum, UCD. 497 (): -8. Kinsely Reserch Centre, Mlhide Rod, Dulin 7. Tegsc. ISBN -9--38-8-8. 5. Oski, M., H. Ued, T. Shinno, H. Mtsui nd T. Tdno, 995. Accumultion of cron nd nitrogen compounds in sweet potto plnts grown under deficiency of N, P, or K nutrients. Soil Sci. nd Plnt Nutrition, 4(3): 557-566. 6. Berg, L. nd K. Ceser, 99. Reltionships etween numer of min stems nd yield components of potto (Solnum tueresom L. CV. Erntestolz) s influenced y different dy length. Am. J. Potto Res., 33: 57-67. 7. Joern, B.C. nd M.L. Vitosh, 995. Influence of pplied nitrogen on potto. Prt I: Yield, qulity nd nitrogen uptke. Am. Potto. J., 7: 5-63. 8. Georgkis, D.N., D.I. Krfyllidis, N.I. Stvropoulos, E.X. Niniou nd I.A. Vezyroglou, 997. Effect of plnting density nd size of potto seed-minituers on the size of the produced potto seed tuers. Act. Hort. (ISHS), 46: 935-94. 37
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