Kenosha, Wisconsin, USA c Institute of Soil and Fertilizer, Shandong Academy of Agricultural

Transcription

1 This rtile ws downloded by: [Universiteit Leiden / LUMC] On: 28 April 2014, At: 01:42 Publisher: Tylor & Frnis Inform Ltd Registered in Englnd nd Wles Registered Number: Registered offie: Mortimer House, Mortimer Street, London W1T 3JH, UK Journl of Plnt Nutrition Publition detils, inluding instrutions for uthors nd subsription informtion: ZEOLITE AS SLOW RELEASE FERTILIZER ON SPINACH YIELDS AND QUALITY IN A GREENHOUSE TEST Zhohui Li b, Yingpeng Zhng d & Yn Li d Fulty of Erth Sienes, Chin University of Geosienes, Wuhn, Chin b Geosienes Deprtment, University of Wisonsin Prkside, Kenosh, Wisonsin, USA Institute of Soil nd Fertilizer, Shndong Ademy of Agriulturl Sienes, Jinn, Chin d Shndong Provinil Key Lbortory of Agriulturl Non-Point Soure Pollution Control, Jinn, Chin Aepted uthor version posted online: 09 Apr 2013.Published online: 25 Jun To ite this rtile: Zhohui Li, Yingpeng Zhng & Yn Li (2013) ZEOLITE AS SLOW RELEASE FERTILIZER ON SPINACH YIELDS AND QUALITY IN A GREENHOUSE TEST, Journl of Plnt Nutrition, 36:10, , DOI: / To link to this rtile: PLEASE SCROLL DOWN FOR ARTICLE Tylor & Frnis mkes every effort to ensure the ury of ll the informtion (the Content ) ontined in the publitions on our pltform. However, Tylor & Frnis, our gents, nd our liensors mke no representtions or wrrnties whtsoever s to the ury, ompleteness, or suitbility for ny purpose of the Content. Any opinions nd views expressed in this publition re the opinions nd views of the uthors, nd re not the views of or endorsed by Tylor & Frnis. The ury of the Content should not be relied upon nd should be independently verified with primry soures of informtion. Tylor nd Frnis shll not be lible for ny losses, tions, lims, proeedings, demnds, osts, expenses, dmges, nd other libilities whtsoever or howsoever used rising diretly or indiretly in onnetion with, in reltion to or rising out of the use of the Content. This rtile my be used for reserh, tehing, nd privte study purposes. Any substntil or systemti reprodution, redistribution, reselling, lon, sub-liensing, systemti supply, or distribution in ny form to nyone is expressly forbidden. Terms &

2 Downloded by [Universiteit Leiden / LUMC] t 01:42 28 April 2014 Conditions of ess nd use n be found t

3 Journl of Plnt Nutrition, 36: , 2013 Copyright C Tylor & Frnis Group, LLC ISSN: print / online DOI: / ZEOLITE AS SLOW RELEASE FERTILIZER ON SPINACH YIELDS AND QUALITY IN A GREENHOUSE TEST Downloded by [Universiteit Leiden / LUMC] t 01:42 28 April 2014 Zhohui Li, 1,2 Yingpeng Zhng, 3,4 nd Yn Li 3,4 1 Fulty of Erth Sienes, Chin University of Geosienes, Wuhn, Chin 2 Geosienes Deprtment, University of Wisonsin -Prkside, Kenosh, Wisonsin, USA 3 Institute of Soil nd Fertilizer, Shndong Ademy of Agriulturl Sienes, Jinn, Chin 4 Shndong Provinil Key Lbortory of Agriulturl Non-Point Soure Pollution Control, Jinn, Chin There hs been gret need to redue the non-point soure pollution due to pestiide nd fertilizer pplitions. With high surfe re nd lrge tion exhnge pity, zeolite ws proposed to use s rriers to ontrol mmonium nd potssium relese. A greenhouse test ws onduted to evlute spinh growth nd spinh qulity fter pplition of zeolite pre-lod with mmonium (NH + 4 ) nd potssium (Eo-zeolite). An inrese in spinh yield with omprble vitmin C ontent ws hieved using the Eo-zeolite. However, elevted oxlte ontent ws unexpeted, possible due to the presene of NH + 4 s the exhngeble tions fter modifition. Keywords: INTRODUCTION fertilizer, oxlte, spinh, yield, zeolite Improved nutrient use effiieny in prodution griulture is reserh priority for both gronomi nd environmentl resons. To minimize groundwter ontmintion used by nitrte nd phosphte during irrigtion fter pplition of fertilizers nd mximize the effiieny of input fertilizers, slow relese fertilizers (SRFs) hve drwn gret ttention reently. Current dditives to SRFs inlude nturl ourring minerls tht hve high tion exhnge pity s well s syntheti tion nd nion exhnge resins. Zeolites re fmily of rystlline luminosilites, while linoptilolite is nturlly ourring zeolite, formed by devitrifition of volni sh in Reeived 7 Jnury 2011; epted 13 September Address orrespondene to Zhohui Li, Fulty of Erth Sienes, Chin University of Geosienes, Wuhn, Hubei , Chin. E-mil: li@uwp.edu 1496

4 Zeolite As Slow Relese Fertilizer On Spinh 1497 Downloded by [Universiteit Leiden / LUMC] t 01:42 28 April 2014 lke nd mrine wters. Mny tests were onduted to evlute linoptilolite s dditives to SRFs to ontrol the relese of mmonium (NH 4 + )nd potssium (K + ). In greenhouse study, less thn 5% of the dded nitrogen (N) lehed out from the sndy soil when mmonium-loded linoptilolite ws used in ontrst to 10 to 73% of N lehing when mmonium sulfte ws pplied depending on the N lehing rte (Perrin et l., 1998). More N ws ssimilted when mmonium-loded linoptilolite ws used ompred to mmonium sulfte. Both tion exhnge nd olusion methods were ommonly used for preprtion of zeolite-bsed SRFs. A two-fold inrese in N loding pity ws hieved using n olusion method, while the slow relese of N ws not ffeted (Prk nd Komrneni, 1998). Seprtely, series of studies were undertken using zeolite mixed with phosphte roks to ontrol phosphte relese (Brbrik et l., 1990; Allen et l., 1995). In suh system the slightly soluble phosphte rok served s the soure for the slow relese of P while the mmonium tion-exhnged zeolite s the soure for the slow relese of N (Allen et l., 1995). Zeolite ould lso be modified by surftnt s SRF rriers to ontrol nitrte (Li, 2003), phosphte (Bnsiwl et l., 2006) nd sulfte (Li nd Zhng, 2010) relese. A 20-fold redution in nitrte onentrtion in the effluent ws hieved when nitrte-loded surftnt-modified zeolite ws used in omprison to wter soluble nitrte of the sme loding (Li, 2003). Phosphorus supplies from phosphte-loded surftnt-modified zeolite were vilble even fter 1080 h of ontinuous peroltion in ontrst to 264 h from monopotssium phosphte (KH 2 PO 4 ) (Bnsiwl et l., 2006). The bove-mentioned studies were foused on SFR preprtion nd its improvement on wter qulity nd redution in fertilizer usge. Tests on the influene of using zeolite on plnt qulity nd yield were lso onduted. Diret ddition of zeolites to soils s soil onditioners resulted in inresed germinbility of spinh seed reltive to ontrols (Burriesi et l., 1984). Use of zeolite led to inresed plnt growth, higher N nd K ontents in plnt tissues nd redued K lehing in trils for the growth of Ltu stiv vr. pitt, nd the ultivrs Bombol nd Brogn in utumn nd spring sesons (Gül et l., 2005). For tomto growth, the ddition of zeolite resulted in n verge inrese in tomto yield by more thn 50% in omprison with the ontrol (Vlente et l., 1982). SRFs resulted in greter root mss development for the growth of Chrysnthemums in omprison to liquid fertilizer with more effiient uptke of fertilizer nd 64 to 68% of pplied N reovery in plnt tissues ompred to 41 to 46% from liquid fertilizer tretment (Ctnzro et l., 1998). For the growth of Lolium multifloru, yield inresed onsiderbly nd nitrogen uptke effiieny ws enhned when linoptilolite-nh 4 + ws used, possibly due to its bility to retin nd slowly liberte NH 4 + ions (Millán et l., 2008).

5 1498 Z. Li et l. The fous of this study ws to evlute the use of zeolite s SFRs for spinh growth s well s its influene on spinh qulity. MATERIALS AND METHODS Preprtion of Eo-Zeolite Downloded by [Universiteit Leiden / LUMC] t 01:42 28 April 2014 Zeolite used ws from Weifng distrit, Shndong, Chin, with tion exhnge pity (CEC) of 0.35 mol kg 1. The N fertilizers used for zeolite modifition were mmonium hloride nd monommonium orthophosphte (NH 4 H 2 PO 4 ) while the K fertilizer ws potssium sulfte. The onentrtions of N fertilizer solution nd K fertilizer solution were both 1 mol L 1. Zeolite ws dded to the N nd K fertilizer solution with liquid to zeolite rtio of 2:1, respetively. The mixture ws stirred 5 min for every 1 to 2 hours for totl of 5 6 times. Then the mixture ws llowed to settle overnight. After the superntnt removed, the nutrient-lden zeolite ws dried nturlly nd used s Eo-zeolite. The N nd K ontents in the superntnt were mesured nd the differene between the initil nd equilibrium onentrtions ws used to lulte the N nd K loding on the zeolite. The mounts of Eo-zeolite used were bsed on the loding of N or K. Growth Conditions The experiments were onduted in the greenhouse of the Institute of Soil nd Fertilizer, Shndong Ademy of Agriulturl Sienes. The soil used ws brown soil obtined from Weihi, Shndong, Chin. Its physil nd hemil properties re listed in Tble 1. Spinh (lolly ultivted Duoneng) ws used in the experiments. To eh 2-gllon lysimeter 10 spinhes were plnted. There were totl of 7 trils: () no nutrients (CK); (b) without N nd C nutrient (N1C1); () optimum tretment (N2C2); (d) onventionl fertilizer (N3C2); (e) onventionl fertilizer + zeolite (N3C2+Z); (f) Eo-zeolite loded with NH 4 + nd K + to 100% CEC nd the mount of N nd K pplied ws the sme s tretment (d) (Z+N+K); (g) Eo-zeolite loded with proper NH 4 + /K + for spinh, i.e., hlf of the mounts of N nd K used for tretment (d) (Z+1/2N+1/2K). In the bove nottions, N1, N2, nd N3 refer 0.0, 0.2 nd 0.4 g kg 1 (N), respetively. N nutrient ws ure in onventionl fertilizer nd mmonium hloride in SRFs. C1 nd C2 refer TABLE 1 Nutrient ondition of the soil used OM Totl N Totl P Totl K Alkli-hydro N Olsen P Avil. K ph (g kg 1 ) (g kg 1 ) (g kg 1 ) (g kg 1 ) N (mg kg 1 ) (mg kg 1 ) (mg kg 1 )

6 Zeolite As Slow Relese Fertilizer On Spinh 1499 TABLE 2 Nutrient pplition rte for different tretments Applition rte (g kg 1 ) Nme Abbrevition N C s CCO 3 KsK 2 O P s P 2 O 5 Control no nutrients provided CK Without N nd C N1C Optimum N2C Conventionl N3C Conventionl +Z N3C2+Z Eo-zeolite +N+K Z+N+K Eo-zeolite + 1/2N+1/2K Z+1/2N+1/2K Downloded by [Universiteit Leiden / LUMC] t 01:42 28 April 2014 to 0.0 nd 0.3 g kg 1 of lium rbonte (CCO 3). P nd K nutrients were supplied with 0.15 nd 0.2 g kg 1. P ws used s KH 2 PO 4 nd K ws supplied with KH 2 PO 4 nd potssium sulfte (K 2 SO 4 ). See Tble 2 for detil bout the nutrient pplition rte. Nitrogen, P, nd K fertilizers of tretments b,, nd d were mixed in topsoil of pot soils s the bse fertilizer. N, P, K fertilizers nd zeolite of tretment e were mixed in topsoil of pot soils s bse fertilizer. P fertilizer, Eo-zeolite with N nd K of tretments f nd g were mixed in topsoil of pot soils s bse fertilizer. The spinhes were hrvested fter two nd hlf months nd yield mesured. The nitrte, soluble oxlte nd totl oxlte, nd vitmin C ontents were determined s the spinh qulity prmeters. Eh tril ws tested in three replites, i.e., 30 spinh plnts per tretment. Due to low wter evportion rte, the lehte ws not olleted. Mesurements The totl oxlte ws determined using method from Bker (1952) with some modifitions (Zhng et l., 2005). Two g of plnt smple were grinded in mortr with 2 ml 6 M hydrohlori id (HCl). The homogente ws then trnsferred to 50 ml entrifugl tube with 30 ml distilled wter. Two drops of pryl lohol were dded nd the mixture boiled for 15 minutes in wter-bth, before being ooled down overnight. The mixture ws entrifuged for 10 minutes t 5000 rpm nd 20 ml of the superntnt trnsferred to new entrifugl tube. Five ml of phosphori-tungstte regent ws dded. The mixture ws llowed to set side for more thn 5 hours before it ws entrifuged gin for 10 minutes t 5000 rpm. The superntnt ws trnsferred to new entrifugl tube, nd mmonium hydroxide ws dded dropwise from burette until ph ws between 4.5 nd 5.0 monitored by ph meter. A 5 ml of eti id buffer solution of ph4.5 (inluding lium hloride regent) ws then dded. After being stirred with fine glss rod, the tube ws left overnight in refrigertor t 4 7 C. The mixture ws entrifuged for 10 minutes t 5000 rpm, nd the superntnt ws

7 1500 Z. Li et l. Downloded by [Universiteit Leiden / LUMC] t 01:42 28 April 2014 removed refully. The preipitte ws wshed with 20 ml of wshing solution, stirred vigorously with fine rod until the preipitte ws broken up nd the impurities were dissolved. The mixture ws entrifuged for 10 minutes, the superntnt refully removed, nd the preipitte dissolved with 10 ml of 10% sulfuri id nd trnsferred to n Erlenmeyer flsk. The Erlenmeyer flsk ws pled in wter-bth t 100 C for two minutes nd the oxli id ws titrted with 0.02 mm potssium permngnte till the pink olor styed for more thn 30 seonds. The oxli id onentrtion of spinh ws lulted ording to the volume of potssium permngnte onsumption. The bove proedure ws followed for the extrtion of wter soluble oxlte exept tht 2 ml of distilled wter ws used insted of 2 ml 6 M HCl. Nitrte ontent ws mesured by sliyli id olorimetri method, while vitmin C ontent ws determined by titrtion method using 2, 6- Dihlorophenolindophenol sodium slt hydrte (Li, 2000). The dt obtined from this study were sttistilly nlyzed using DPS 2000 (Dt proessing system) (version 6.05) (Tng nd Feng, 2007). RESULTS AND DISCUSSION Effets of Different Types of Fertilizers on Spinh Biomss Different fertilizers hd obvious effets on spinh yields (Figure 1). The ontrol hd the lowest yield, only 1.24 g plnt 1, due to bsene of fertilizer pplition, followed by N1C1, in whih only K nd P fertilizers were pplied. Among the other five tretments, the N2C2 tretment produed Spinh biomss (g/plnt) e d b b b 0 Tretments FIGURE 1 Effets of different fertilizers on spinh biomss. Different letters bove eh br indite signifint differene t P = 0.05 level.

8 Zeolite As Slow Relese Fertilizer On Spinh 1501 Downloded by [Universiteit Leiden / LUMC] t 01:42 28 April 2014 the highest yield, followed by Z+1/2N+1/2K, Z+N+K, nd N3C2+Z. The onventionl fertilizer N3C2 hd lower yield ompred to those tretments pplied with Eo-zeolite. Compred to the onventionl fertilizer with the sme mount of nutrients pplied higher yields ould be hieved when Eo-zeolite ws used even though, the differene ws sttistilly not signifint. In ddition, the tretment with Z+1/2N+1/2K hd higher yield thn N 3 C 2 tretment even though only hlf of N nd K mounts were used. It ould be speulted due to improved nutrient utiliztion effiieny of spinh nd redued fertilizer loss in the presene of zeolite. Tests on growth of tomtoes showed no improvement of fruit size or mrketble yields when SRFs ws used in omprison to wter soluble mmonium nitrte (NH 4 NO 3 )- potssium nitrte (KNO 3 ) ontrol (Csizinszky, 1994). This study showed tht use of zeolite s SRFs to inrese spinh yield ws fesible. Effets of Different Tretments on Nutritive Qulity of Spinh Vitmin C (VC) is thought s one of the importnt nutritive qulities of vegetbles. In the test, different tretments hd mrkedly influene on VC ontent in spinh (Figure 2). The highest VC ontent ws hieved when N2C2 ws pplied, followed by N3C2. Sttistilly the lowest vitmin C levels ourred with the N1C1, N3C2+Z, nd the Z+N+K tretments. Menwhile, Z+1/2N+1/2K hd reltive higher VC ontent. Vitmin C ontent (mg/100g FW) N1C1 N2C2 N3C2 N3C2+Z Z+N+K Z+1/2N+1/2K b b Tretments FIGURE 2 Effets of different tretments on vitmin C ontent of spinh leves. Different letters bove eh br indite signifint differene t P = 0.05 level.

9 1502 Z. Li et l. Effets of Different Tretments on Sfe Qulity of Spinh Downloded by [Universiteit Leiden / LUMC] t 01:42 28 April 2014 Nitrte nd oxlte were two importnt ftors, whih n limit sfe qulity of vegetbles nd hinder humn helth (Zhng et l., 2008). The results from this study showed tht different tretments hd no obvious effets on nitrte ontent in spinh exept for the tretments of CK nd N1C1, in whih N supply ws not provided (Figure 3). This ould be ttributed to the improved nitrogen quntity, whih ould inrese the bsorption of nitrte, resulting in less nitrte umultion in spinh. Clium n lso ffet the nitrte ontent in plnts. C 2+ n inhibit the tivity of nitrte redutse to ertin degree (Lillo, 1993), whih would result in more nitrte bsorption thn redution nd less nitrte umultion in spinh. The ltter ould be the mjor use for the lower nitrte ontent in spinh with CK nd N1C1 pplition. Oxlte ws thought s toxin nd nti-nutrient. Oxlte n not only redue the bio-vilbility of lium (C), mgnesium (Mg), nd iron (Fe), but lso inrese the mount of oxli id exerted, thus inresing the probbility of stones in kidney nd bldder (Frneshi nd Nkt, 2005; Lewndowski nd Rodgers, 2004). Conentrtions of different oxlte in the edible prts of spinh hve been of onern beuse of their different humn helth effets. In the study, different tretments hd obvious effets on totl oxlte ontent in spinh (Figure 4). The tretments with Eo-zeolite hd higher totl oxlte ontents thn those without zeolite. Soluble oxlte inresed s N supply inresed from 0 to 0.4 g kg 1 soil ( Figure 5). When nitrogen Nitrte ontent (ug/g FW) b 0 Tretments FIGURE 3 Effets of different tretments on nitrte ontent in spinh. Different letters bove eh br indite signifint differene t P = 0.05 level.

10 Zeolite As Slow Relese Fertilizer On Spinh 1503 Downloded by [Universiteit Leiden / LUMC] t 01:42 28 April 2014 Totl oxlte ontent (mg/100g FW) N1C1 N2C2 N3C2 N3C2+Z Z+K+N Z+1/2N+1/2K Tretment FIGURE 4 Effets of different tretments on totl oxlte ontent of spinh. Different letters bove eh br indite signifint differene t P = 0.05 level. ws supplied t rte of 0.4 g kg 1,Z+K+N tretment resulted in the highest soluble oxlte ontent, followed by N3C2+Z tretment. The N nd C ontent ould ffet the oxlte ontents in spinh. Previous studies showed tht higher N ontent in the ulture solution would result in n umultion of nitrte nd oxlte ontents (Eli et l., 1998; Ahmed nd Johnson, 2000; Zhng et l., 2009). Fertilizers ontining N under forms not redily vilble to the rop, i.e., ure [CO(NH 2 ) 2 ]ndmmonium sulfte [(NH 4 ) 2 SO 4 ], inresed nitrte nd oxlte umultions Soluble oxlte ontent (mg/100g FW) d d N1C1 N2C2 N3C2 N3C2+Z Z+K+N Z+1/2N+1/2K Tretment b b FIGURE 5 Effets of different tretments on soluble oxlte ontent of spinh. Different letters bove eh br indite signifint differene t P = 0.05 level.

11 1504 Z. Li et l. Downloded by [Universiteit Leiden / LUMC] t 01:42 28 April 2014 less fst thn N-relese fertilizers (Stgnri et l., 2007). Therefore, inresing the rtio of N in mmonium form to N in nitrte form n effetively derese the nitrte nd oxlte ontents in vegetbles (Ahmed nd Johnson, 2000; Plniswmy et l., 2004). However, the N in Eo-zeolite ws in mmonium form. Thus, these results re unexpeted. An inrese in oxlte ontent ws found when N supply inresed nd C supply deresed. The relese of mmonium during irrigtion is through tion exhnge proesses. The substitution of C for mmonium will redue the vilbility of C for the plnt, whih my result in higher oxlte ontent. On the other hnd, it ws suggested tht the exhnge properties of the luminosilites did not ply n importnt role in tomto-growing nd the benefiil effet ws due to other ftors suh s the presene of iron (Fe) nd K (Vlente et l., 1982). Although this is not desired result, irrigtion with hrder wter with high C ontent my overome this drwbk. CONCLUSIONS In this study, zeolite used s SRFs n inrese spinh yields ompred to onventionl fertilizer with the sme fertilizer mounts used, lthough the sme yield ws hieved when both optimum nd Eo-zeolite were used. Zeolite with 1/2N+1/2K n redue the ost of fertilizer nd hieve the sme vitmin C ontent of spinh, so zeolite used s SRFs hs good mrket prospet. Although the results using Eo-zeolite showed no derese on nitrte nd oxlte ontent in spinh ompred to the onventionl fertilizers, the proess of produing SRFs using zeolite ould be modified nd the nutrients relesing mehnism would be further studied. ACKNOWLEDGMENT This work ws finnilly supported by the Nturl Siene Foundtion of Shndong Provine (Y2007D62) nd by the Wisonsin Fertilizer Reserh Progrm. REFERENCES Ahmed, A. K., nd K. A. Johnson The effet of the mmonium: Nitrte rtion, totl nitrogen, slinity (NCl) nd lium on the oxlte levels of Tetrgoni tetrgonioides Plls. Kunz. Journl of Hortiulturl Siene nd Biotehnology 75: Allen, E. R., D. W. Ming, L. R. Hossner, D. L. Henninger, nd C. Glindo Growth nd nutrient uptke of whet in linoptilolite-phosphte rok substrtes. Agronomy Journl 87: Bker, C. J. L Determintion of oxltes in fresh plnt mteril. Anlyst 77: Bnsiwl, A. K., S. S. Rylu, N. K. Lbhsetwr, A. A. Juwrkr, nd S. Devott Surftntmodified zeolite s slow relese fertilizer for phosphorus. Journl of Agriulture nd Food Chemistry 54:

12 Zeolite As Slow Relese Fertilizer On Spinh 1505 Downloded by [Universiteit Leiden / LUMC] t 01:42 28 April 2014 Brbrik, K. A., T. M. Li, nd D. D. Eberl Exhnge fertilizer (phosphte rok plus mmoniumzeolite) effets on sorghum-sudngrss. Soil Siene Soiety of Amerin Journl 54: Burriesi, N., S. Vlente, R. Ottnà, G. Cimino, nd C. Zipelli Utiliztion of zeolites in spinh growing. Zeolites 4: 5 8. Ctnzro, C. J., K. A. Willims, nd R. J. Suve Slow relese versus wter soluble fertiliztion ffets nutrient lehing nd growth of potted hrysnthemum. Journl of Plnt Nutrition 21: Csizinszky, A. A Yield response of bell pepper nd tomto to ontrolled-relese fertilizers on snd. Journl of Plnt Nutrition 17: Eli, A., P. Sntmri, nd F. Serio Nitrogen nutrition, yield nd qulity of spinh. Journl of the Siene of Food nd Agriulture 76: Frneshi, V. R., nd P. A. Nkt Clium oxlte in plnts: Formtion nd funtion. Annul Review of Plnt Biology 56: Gül, A., D. Eroğul, nd A. R. Ongun Comprison of the use of zeolite nd perlite s substrte for risp-hed lettue. Sienti Hortiulture 106: Lewndowski, S., nd A. L. Rodgers Idiopthi lium oxlte urolithisis: Risk ftors nd onservtive tretment. Clini Chimi At 345: Li, H. S Priniples nd Tehnology of Plnt Physiologil nd Biohemil Experiment. Beijing: Higher Edution Press (in Chinese). Li, Z Use of surftnt-modified zeolite s fertilizer rriers to ontrol nitrte relese. Miroporous Mesoporous Mterils 61: Li, Z., nd Y. Zhng Use of surftnt-modified zeolite to rry nd slowly relese sulfte. Deslintion nd Wter Tretment 21: Lillo, C Mgnesium nd lium inhibition of sqush lef NADH Nitrte redutse. Plnt Cell Physiology 34: Millán, G., F. Agosto, M. Vázquez, L. Botto, L. Lombrdi, nd L. Jun Use of linoptilolite s rrier for nitrogen fertilizers in soils of the Pmpen regions of Argentin. Cieni Investigión Agrri 35: Plniswmy, U. R., B. B. Bible, nd R. J. MAvoy Oxli id onentrtions in purslne (Portul oleree L.) is ltered by the stge of hrvest nd the nitrte to mmonium rtios in hydroponis. Sienti Hortiulture 102: Prk, M., nd S. Komrneni Ammonium nitrte olusion vs. nitrte ion exhnge in nturl zeolites. Soil Siene Soiety of Amerin Journl 62: Perrin, T. S., D. T. Drost, J. L. Boettinger, nd J. M. Norton Ammonium-loded linoptilolite: A slow-relese nitrogen fertilizer for sweet orn. Journl of Plnt Nutrition 21: Stgnri, F., V. D. Bitetto, nd M. Pisnte Effets of N fertilizers nd rtes on yield, sfety nd nutrients in proessing spinh genotypes. Sienti Hortiulture 114: Tng, Q. Y., nd M. G. Feng DPS Dt Proessing System. Beijing: Siene Press (in Chinese). Vlente, S., N. Burriesi, S. Cvllro, S. Glvgno, nd C. Zipelli Utiliztion of zeolites s soil onditioner in tomto-growing. Zeolites 2: Zhng, Y. P., Y. Li, J. L. Wei, M. Sun, nd Z. Li Effets of nitrogen nd lium nutrition on oxlte ontents, forms nd distribution in spinh (Spini olere L.). Journl of Plnt Nutrition 32: Zhng, Y. P., Y. Li, M. W. Zhng, M. Sun, X. J. Wng, X. X. Dong, nd B. M. Go Effets of nitrogen nd lium nutrition on sfety qulity nd nti-oxidtive enzyme tivities of spinh. Plnt Nutrition nd Fertilizer Siene 14: (in Chinese with English Abstrt) Zhng, Y. P., X. Y. Lin, Y. S. Zhng, S. J. Zheng, nd S. T. Du Effets of nitrogen levels nd nitrte/mmonium rtios on oxlte onentrtions of different forms in edible prts of spinh. Journl of Plnt Nutrition 28: