Research Article

E ffect of Biochar, Farmyard M anure and Poultry Manure on Z n Adsorption in Calcareous Alkaline Soil

Ab i da Sal e e m*, Saj i da Parvee n and Muhammad Jamal Khan

Department of Soil a nd E n vironme n tal S cie n ces, T he Univer sity of Ag ricult ure, P e s hawa r, Khyber Pakhtunkhwa, Pakistan.

Abstract | T h e e f f e ct of Farm Yard Manure (F Y M), Press Mud (P M), a n d Biochar (B C) a pplied t o a f r e s h s oil was e v a l u a t e d on Z n a d s o r p t ion po t e n t ial in c a lc a r eo u s alk a li n e s oils [Piedmont alluvium, silty clay loam, Ustochrept]. T h e Z n a d s o r p t ion c a pa c i t y w a s de t e r mi n ed by a ddi n g 50 ml of 0, 5, 10, 20, 40, 60, 120, 240 a n d 360 mg Z n L-1 (i n i t ially Z n a pplied, I Z n A) t o 5 g s oil wi t h ab s e n c e (n o n-tr e a t ed) or t o s oil p r e tr e a t e d wi t h FY M, P M or B C a t r a t e of 10 g k g-1. T h e sus p e ns ion was s h ak e n on h o r i z o n t al s h ak e r for 20 h co n t i n u o u s ly t o a ss e s s t h e eq u ilib r i u m Z n c o n c e n t r a t ion (E Z nC). T h e di f f e r e n ce be t we e n t h e I Z n A a n d EZ n C w as a ssu m e d t o be ad s o r b e d. R e su l t s sh ow e d t h at FY M, P M or B C y ield e d lower EZ n C a n d h i g h e r Z n ad s o r p t ion (x/m) a t h i gh er I Z n A b u t at lower I Z n A< 20 mg Z n L-1 th e r e v e r s e w a s ob s e rv ed. T h e da t a in n o n-tr e a t e d s oils we r e fit t o bo t h L a ng m u ir a n d F r e u n dlich b u t in tr e a t e d s oils t h ey w e r e f it o n ly w h e n a d s o r p t ion v a l u e s for i n i t i a l I Z n A w e r e di s r e g a r ded. T h e ad s o r p t ion, a s i n di c ate d by b a n d K v al u es w a s h i g h e r for B C f ollowed by F Y M b u t M C B a n d 1/n v a l u e t h at r e f le c t s t h e b u f f e r i n g c a pa c i t y w a s h i g h e r for F Y M t h an B C or P M. T h e lower a d s o r p t ion of Z n a t low e r I Z n A b e low 20 mg Z n L-1 a n d h i gh er f or h i g h e r I Z n A f or am e n d e d s oil o v e r n o n-tr e a t e d s oil su g g e st i n g i t s co n t r a st i n g e f f e c t a t di f f e r e n t I Z n A le v el s.

Received | May 24, 2016; Accepted | August 03, 2016; Published | November 03, 2016

Correspondence | Ab i da Sal e e m, Department of Soil a nd E n vironme n tal S cie n ces, T he Univer sity of Ag ricult ure, P e s hawa r, Khyber Pakhtunkhwa, Pakistan; Em ail: abda_s aleem@yahoo.com

Citation | Ab i da Sal e e m, A., S. Parvee n and M.J. Khan. 2016. Effect of biochar, farmyard manure and poultry manure on Zn adsorption in calcareous alkaline soil. Sarhad Journal of Agriculture, 32(4): 354-363.

DOI | http://dx.doi.org/10.17582/journal.sja/2016.32.4.354.363

Keywords | Z i n c, Z n ad s o r p t io n, Bio c h a r, I s o t h e r m mod e l, C a lc a r eo u s s oil

In t r o d u c t i o n

Zinc content in soil ranges from 10 to 300 mg kg-1 with an average value of 50 mg kg-1 (Kiekens, 1995); however, as compared to its total amount available Zn concentration in soil solution is very low. Values greater than 0.9 mg kg-1 AB-DTPA ext. Zn are regarded as optimum levels for agronomical crops (Soltanpour, 1985). The soil zinc exists in different forms i.e. in soil solution, in exchangeable form, bound with soil organic matter, Fe, Al and Mn oxide in primary or secondary minerals (Viets, 1962; Catlett et al., 2002). The immediate source for plant uptake is soil solution Zn2+ which is determined by different reactions like complexation, adsorption and precipitation of metals in soils. Adsorption process is very important in determining zinc (Zn) availability and fate in soil. Several adsorption isotherms have been employed to relate the Zn concentration in solution to that retained by the solid phase (Xie and Mackenzie, 1991).

Soil properties like pH (Zahedifar et al., 2010; Pérez-Novo et al., 2011), clay type, (Dahiya et al., 2005), clay content (Dahiya et al., 2005), organic matter (Perez-Novo et al., 2008), total carbonate and active carbonate content (Al-Kaysi, 2000; Al-Tamimi, 2006), amount of zinc applied and zinc carrier (Obrador et al., 2003) and sulfur contents (Alloway, 2009) have strong influence on adsorption-desorption process and regulating the Zn solubility and fractionation in soils. Low redox potential (Johnson-Beebout et al. 2009), soil solution composition (Wang and Harrell, 2005; Zhao et al., 2010), ionic strength (Shuman, 1986) and complex formation with inorganic ligands in soil solution (Mattigod and Sposito, 1977) are the other factors which affect Zn solubility. Zinc solubility is also controlled by phosphate-Fe oxides interactions (Wang and Harrell, 2005). The deficiency is more common in calcareous and salt affected soils (Khoshgoftarmanesh et al., 2006) where elevated lime and pH levels are reportedly responsible for high Zn adsorption (Karimian and Moafpouryan, 1999).

The organic fraction of soil could influence these reactions through chelation and associated soil physico-chemical characteristics that lead to either decrease or increase in availability of Zn to plants. Organic matter content increased the Zn sorption (Vega et al., 2007) resulting in Zn deficiency due to formation of insoluble Zn- organic complexes (Andriano, 2001). It is a common practice to add organic matter amendments, such as compost, fertilizers and wastes for immobilization of heavy metals and amelioration of contaminated soils (Clemente et al. 2005). The effect of organic matter amendments on heavy metal bioavailability depends on the nature of the organic matter, their microbial degradability, salt content and effects on soil pH and redox potential, as well as on the particular soil type and metals concerned (Walker et al. 2003). But on the other hand, this organic matter especially the soluble C fraction acting as chelating agent which decreases the Zn adsorption and increases formation of soluble organic-Zn complexes and thus increases the availability to plants (Shuman, 1999). The increase in crop yields could be attributed to improvement in soil ph y sical, c h emical and biological activities promoting soil-pla nt s y st em. The incr ease in n u trition especially of mic ron u t rie n ts is us ually believed as res ult of decomposition of initially applied amendmen ts. In s uch sit uation t he improv ement in t he specific n u trient would depe nd on its conce n tration in t he s ubst r a te and its r a te of decomposition. Howe v e r, t he c h emical c h a rac t e ristics of t he adding ma t e rial a nd c h a n ges brought about in t he soil properties are site specific.

In low conce n tration of micron u trien ts or ganic amendmen ts a re argued to enhance t he n u trient a v ailability to pla nt but on t he ot her hand t hese ame ndme n ts are advised for ph y to-s tabiliz a tion of con taminated soils (K h an et al., 2012). At low con cen t r a tion, t he amendmen ts a re believed to reduce t he bonding ener gy and t h us t he adsorption of Zn could be decr eas ed but t hey also in c rea se t he C EC of soil (B o h n et al., 2001) t h at can incr ease t he adsorption of Zn at higher levels. T h e se c h a n ges in soil can c h a n ge with t he org a nic amendmen ts, a nd as su ch t his s t udy was initiated to evaluate t he effect of B C, FYM and PM on Zn adsorption capacity of calca reous soil to a ssess t h eir role in Zn n u t rition of calca reous soil.

Mate r ials a nd Meth o ds

T he effect of or ganic amendmen ts including FYM, PM and BC on Zn adsorption poten tial of s tron gly calca reous (16.6 % CaCO 3) alkaline (pH 8.36) soils of P e s hawar series [Piedmont alluvium, silty clay loam, Ustochrept] was e v alu a t ed in t he labor a tory of Soil a nd E n vironme n tal S cie n ces, T he Univer sity of Ag ricult ure P e s hawar du ring 2016. The soil under study was silty clay loam (clay 11 %) and low in organic matter (0.68 %) and AB-DTPA extractable Zn (0.8 mg kg-1). Fresh soil s ample was collec t ed from Res ear ch Fa rm of t he u niver sity and was air dried and sieved t h rough 2 mm sieve. T he soil was fir st added with FY M, PM a nd BC each at 20 t h a-1 (10 g kg-1 soil) before addition of Zn solu tion. T he stock solu tion of Zn was pr epar ed from dissolving eleme n tal Zn in HCl solu tion at t he rate of 1000 mg L-1 wher eas t he working solu tions of 0, 5, 10, 20, 40, 60, 120, 240 and 360 mg Zn L-1 we re pr epar ed in 0.01 M C a C l 2 solu tion.

T he Zn adsorption isot h e rms were determined by t he procedu re of Fox a n d K a mp r a t h (1970) which h as been u sed by s e v e ral r e sea rchers including S olis a n d T o rr e n t (1989), H u ss ain et al. (2007) a nd M a nz oor (2013) for P adsorption. In t his st udy, 50 ml solu tion con taining 0, 10, 20, 40, 60, 120, 240 a nd 360 mg Zn L-1 (initially applied Z n, I Z nA) was applied to 5 g soil in 250 mL open mou t h ed conical fla sks. The soil plus respective Zn solu tions taken in duplicate we re s haken on horizon t al sh aker for 20 h con tin uously. T he suspe nsions were filtration t h rough Wh a t tman No. 42. T he Zn in t he supe r n a t a n ts was determined using atomic absorption spectrophotometry af t er dilu ting t he s ample to g et machine readin gs in t he range of 0.1 to 2 mg L-1. T his con cen t r a tion was r epres e n ted as equilibrium Zn con cen t r a tion (EZ nC). T he differ e n ce be tween t he I Z nA and EZ nC was ass umed to be t he adsorbed Zn mg kg-1 de noted by x/m.

T able 1: Effect of org a nic ame ndme n ts on Zn adsorption c h a rac t e ristics in s tron gly calca reous alkaline soil of P e sh awar s e ries

I n i t i a l Zn ap p l i e d (I Z n C) | E Z n C | Zn a d s o r b e d | X ad | K d | E ZnC/X/m
m g/L | m g/k g | m g/L | m g/L | m g/k g | % |  |
--------------------------------------------- Zn a l o n e ---------------------------------------------
5 | 5 0 | 0.5 6 | 4.4 4 | 4 4.3 8 | 8 8.7 5 | 7 8.8 9 | 0.0 1 3
1 0 | 1 0 0 | 1.2 3 | 8.7 8 | 8 7.7 5 | 8 7.7 5 | 7 1.6 3 | 0.0 1 4
2 0 | 2 0 0 | 2.9 5 | 1 7.0 5 | 1 7 0.5 0 | 8 5.2 5 | 5 7.8 0 | 0.0 1 7
4 0 | 4 0 0 | 8.3 5 | 3 1.6 5 | 3 1 6.5 0 | 7 9.1 3 | 3 7.9 0 | 0.0 2 6
8 0 | 8 0 0 | 3 0.5 8 | 4 9.4 3 | 4 9 4.2 5 | 6 1.7 8 | 1 6.1 7 | 0.0 6 2
1 2 0 | 1 2 0 0 | 6 1.4 0 | 5 8.6 0 | 5 8 6.0 0 | 4 8.8 3 | 9.5 4 | 0.1 0 5
2 4 0 | 2 4 0 0 | 1 4 9.2 3 | 9 0.7 8 | 9 0 7.7 5 | 3 7.8 2 | 6.0 8 | 0.1 6 4
3 6 0 | 3 6 0 0 | 2 4 5.5 0 | 1 1 4.5 0 | 1 1 4 5.0 0 | 3 1.8 1 | 4.6 6 | 0.2 1 4
----------------------------------------------- Z n + P M -----------------------------------------------
5 | 5 0 | 1.8 0 | 3.2 0 | 3 2.0 3 | 6 4.0 5 | 1 7.8 2 | 0.0 5 6
1 0 | 1 0 0 | 3.1 3 | 6.8 8 | 6 8.7 5 | 6 8.7 5 | 2 2.0 0 | 0.0 4 5
2 0 | 2 0 0 | 3.7 0 | 1 6.3 0 | 1 6 3.0 0 | 8 1.5 0 | 4 4.0 5 | 0.0 2 3
4 0 | 4 0 0 | 7.5 8 | 3 2.4 3 | 3 2 4.2 5 | 8 1.0 6 | 4 2.8 1 | 0.0 2 3
8 0 | 8 0 0 | 2 6.6 0 | 5 3.4 0 | 5 3 4.0 0 | 6 6.7 5 | 2 0.0 8 | 0.0 5 0
1 2 0 | 1 2 0 0 | 5 0.6 1 | 6 9.3 9 | 6 9 3.9 0 | 5 7.8 3 | 1 3.7 1 | 0.0 7 3
2 4 0 | 2 4 0 0 | 1 3 2.4 3 | 1 0 7.5 7 | 1 0 7 5.6 8 | 4 4.8 2 | 8.1 2 | 0.1 2 3
3 6 0 | 3 6 0 0 | 2 3 4.3 0 | 1 2 5.7 0 | 1 2 5 7.0 0 | 3 4.9 2 | 5.3 6 | 0.1 8 6
----------------------------------------------- Z n + F YM -----------------------------------------------
5 | 5 0 | 1.6 8 | 3.3 3 | 3 3.2 5 | 6 6.5 0 | 1 9.8 5 | 0.0 5 0
1 0 | 1 0 0 | 2.4 8 | 7.5 3 | 7 5.2 5 | 7 5.2 5 | 3 0.4 0 | 0.0 3 3
2 0 | 2 0 0 | 2.6 5 | 1 7.3 5 | 1 7 3.5 0 | 8 6.7 5 | 6 5.4 7 | 0.0 1 5
4 0 | 4 0 0 | 4.3 5 | 3 5.6 5 | 3 5 6.5 0 | 8 9.1 3 | 8 1.9 5 | 0.0 1 2
8 0 | 8 0 0 | 2 3.8 3 | 5 6.1 8 | 5 6 1.7 5 | 7 0.2 2 | 2 3.5 8 | 0.0 4 2
1 2 0 | 1 2 0 0 | 4 8.7 5 | 7 1.2 5 | 7 1 2.5 0 | 5 9.3 8 | 1 4.6 2 | 0.0 6 8
2 4 0 | 2 4 0 0 | 1 2 3.7 3 | 1 1 6.2 8 | 1 1 6 2.7 5 | 4 8.4 5 | 9.4 0 | 0.1 0 6
3 6 0 | 3 6 0 0 | 2 1 9.6 8 | 1 4 0.3 3 | 1 4 0 3.2 5 | 3 8.9 8 | 6.3 9 | 0.1 5 7
----------------------------------------------- Z n + BC-----------------------------------------------
5 | 5 0 | 2.5 3 | 2.4 8 | 2 4.7 5 | 4 9.5 0 | 9.8 0 | 0.1 0 2
1 0 | 1 0 0 | 3.2 6 | 6.7 4 | 6 7.3 8 | 6 7.3 8 | 2 0.6 5 | 0.0 4 8
2 0 | 2 0 0 | 3.4 0 | 1 6.6 0 | 1 6 6.0 0 | 8 3.0 0 | 4 8.8 2 | 0.0 2 0
4 0 | 4 0 0 | 4.9 6 | 3 5.0 4 | 3 5 0.4 3 | 8 7.6 1 | 7 0.6 9 | 0.0 1 4
8 0 | 8 0 0 | 2 0.1 8 | 5 9.8 3 | 5 9 8.2 5 | 7 4.7 8 | 2 9.6 5 | 0.0 3 4
1 2 0 | 1 2 0 0 | 4 9.8 0 | 7 0.2 0 | 7 0 2.0 0 | 5 8.5 0 | 1 4.1 0 | 0.0 7 1
2 4 0 | 2 4 0 0 | 1 1 6.6 9 | 1 2 3.3 1 | 1 2 3 3.1 0 | 5 1.3 8 | 1 0.5 7 | 0.0 9 5
3 6 0 | 3 6 0 0 | 2 0 2.7 3 | 1 5 7.2 8 | 1 5 7 2.7 5 | 4 3.6 9 | 7.7 6 | 0.1 2 9

X a d: Ra t io of a d s o r p t ion in p e r c e n t wi t h appli e d Z n le v el; K d: r a t io of ad s o r b e d Zn wi t h e q u ilib r i u m [Z n]

Res u lts and D i scussi on

Zn Ad sor p tion as I n f l ue nced by Organ ic Am e n d m e n ts

T he Zn adsorption (x/m) a nd equilibrium Zn (EZ n C) i n c r e a s ed wi t h i n c r e a s e in a pplied Z n l e v e ls (I Z n A) in bo t h tr e a t e d a n d u n t r e a t ed s oils b u t wi t h di f f e r e n t p a t t e rn. T r e a t i n g t h e s oil wi t h o r g a n ic a me n dme n t s t h e Z n ad s o r p t ion w a s comp a r a t i v e ly h i g h e r o v e r r e s p e c t i v e n o n-tr e a t ed s oils a t a ll corresponding applied Zn levels (I Z nA) and as well as equilibrium Zn (EZ nC) when I Z nA was hig h er t han 20 mg Zn L-1 (T able 1). Among t he amendmen ts, BC was more effec tive in promoting adsorption of Zn followed by FYM and t hen PM (F i gure 1). With application of B C, the Zn adsorption rang ed from 2.48 to 157.28 mg L-1 (equiv alent to 24.75 to 1572 mg kg-1 at I Z nA le v els f rom 0-360 mg L-1, w hich was significan tly higher t h an t he range of 4.44 to 114.50 mg L-1 r ecorded in case of non-tr eated soil or FYM and P M.

T his higher adsorption of Zn in ame nded soils res ult ed in sig nifica n tly lower EZ nC (mg L-1) at each I Z nC level t h an t hose received alone Zn in case wh en t he I Z nA le v els were hig h er t han 20 mg L-1. F i gure 1 and 2 both revealed t h at Zn adsorption at any I Z nA or EZ nC levels we re higher for t r eated soils t h an non-tr eated a nd t he BC s upe r seded following FYM and t hen P M. T he hig h er adsorption a nd lower EZ nC r e v ealed t hat ame ndme nt application incr eas ed t he Zn adsorption ov er alone Zn applica tion.

T he Zn adsorbed (x/m) express ed in pe rce nt of I Z nA (Xad) a nd ratio of x/m to EZ nC de noted as dist ribu tion coefficient (K d) dec rea sed with incr eas ed in I Z nA. However, in non-trea t ed both Xad and K d decr eas ed with each in c reme nt of I Z nA from 5 to 360 mg Zn L-1 while in t r eated soil t h ey fir st in c rea sed with initial lower I Z nA and t hen dec rea sed. As s uch in all ame nded soils t he maximum Xad and K d we re obs e r v ed at I Z nA 40 mg L-1 w hich is tot ally differ e nt from non-ame ndme nt soil (Zn alone) where t he ma ximum Xad a nd K d were recorded at lower I ZA i.e. 5 mg Zn L-1 It is an es tablis hed c rit e ria t h at high Xad a nd K d v alu es indicate more efficient r emov al of adsorbate (here Z n) f rom t he soil solu tions by soils (H uss a in et al., 2007). The higher Xad and K d in alone Zn trea t ed soil at lower I Z nA <40 mg Zn L-1) indicated its compar a tively higher affinity and more adsorption of Zn t h an tr eated soils. B ut amended soils s howed higher higher Xad and K d t h an non-ame nded soil at hig h er I Z nA e specially be yond >40 mg Zn L-1. T his con t r a sting pa t tern of Xad and K d at low a nd higher I Z nA indicate t h at or ganic amendmen ts r edu ces t he adsorption of Zn at low I Z nA a nd incr eas es t he adsorption at higher I Z nA. In ot her words t he fr e sh applied or ganic amendmen ts can facilitate Zn a v ailability at low Zn le v els and can play role in ph y tost abilization (Adsorption) at higher Zn le v els (con taminated soil). Among amendmen ts, BC had compar a tively lower Xad a nd K d in initial lower I Z nA a nd higher at higher I Z nA su g g e sting its st rong er in flu e n ces in con t rolling t he Zn adsorption t han PM a nd FY M.

Addition of org a nic ame ndme n ts reduce t he adsorption pot e n tial of Zn (J a l a li a n d J a l a li, 2 0 1 1) a nd P (H uss a in et al., 2006; Y u s r a n, 2010). The s ame has been reported by ma ny r e sea rcher t h at applica tion of or ganic amendmen ts incr ease t he a v ailability of n u trien ts e specially at lowc o n c e n t r a t io n. B u t on t h e o t h e r h a n d, t h e s a me o r g a n ic a me n dme n t s a r e r e comm e n d e d for p h y t o s t abili z a t ion of h e a v y m e t a ls in t h e co n t a mi n a t e d s oil s. T h is r e f le c ts t h a t o r g a n ic a me n dme n t s pl a y a d u al r ol e, at low s oil Z n t h ey c an i n c r e a s e t h e Z n in s ol u t ion b u t at h i g h e r Z n t h ey can incr ease t he adsorption. The s ame obs e r v a tions were recorded in our s t udy.

Ad sor p t ion I sot he rm Equat ion

T he adsorption a nd equilibrium Zn conce n trations da ta received f rom all trea t ed soils were plot t ed in Langmuir and Fr e u ndlich I sot h e rm Models. As dis c uss ed below Langmuir model was be st fit to alone Zn at all I Z nA but became fit to ame nded soil wh en da ta for initial I ZA was dis r e g a rded. S imilarly, Freu ndlich model was fit to non-amended soil at all I Z nA but to or ganically ame nded soil only when v alu es at initial I Z nA were dis regarded.

Langm u ir Ad sor p tion I sot he rm E quation

T he adsorption isot h e rm models of L a n gmuir a nd Freu ndlich we re applied to in ves tig a te Zn adsorption in t he soil by compa ring t he bonding st r e n g t h, maximum Zn adsorption and buffering capacity of t he soil. The classical Langmuir adsorption equ a tion and its linear model, e xpr e ssed by t he following formulas were us ed:

W h erea s in the f o r mul a, x/m is the a mount of Z n a d s o r b e d (mg Z n k g-1), ’K L’ is bonding e n er g y c on s t a nt, ‘b’ is L a n g muir a d s o r ption m a x imum (mg Z n k g-1), E Z nC is the c on ce nt ra tion of Z n in s oil s olution a t e quilib r ium (mg L-1) ‘K L b’ is a l s o known a s m a x imum bu ffer ing c ap a ci t y of t h e s oil s y st e m. B y plo t t i n g t h e EZ n C/(x/m) a g a i ns t E Z n C g i v e s t h e L a ng m u ir Ad s o r p t ion M od e l that p r od u c ed c u rv ili n e ar li n e a r fo r m in bo t h o rg a n i c ally a me n ded a n d n o n-a m e n d e d s oil s.

Howe v e r, f or am e n d e d s oil t h e i n i t i a l v a l u e s of EZ n C/(x/m) w e r e di s r e g a r ded a s t h ey did n ot f it in t h e g r aph (Fi gure 3). S a n y a l et al. (1993), H u ss ain et al. (2006) and H u ss ain et al. (2007) al s o ob s e r v e d c ur v ili n e a r L a n g m u ir plo t s. M a n z oor (2013) al s o r e po r t e d t h e c u rv ili n e ar L a ng m u ir plot in t h e s a me s oil f or P a d s o r p t io n. T h e c u rv ili n e ar b e h a v ior s ug g e s t ed t h a t o r i g i n a lly t h e s oil h ad v a r y i n g bo n di n g e n e r g y for Z n a d s o r p t ion a n d t h e a d s o r p t ion c a pa c i t y of s oil de c r e a s ed wi t h e a c h a ddi t io n al i n c r e me n t of I Z n A. G u n a r y (1970) st a t e d t h at t h e c u rv ili n e ar r e la t io ns h ip me a n t h a t t h e s oil wo u ld a d s o r b a s m a ll amo u n t of a d s o r ba t e (h e r e t h e Z n) l e s s fi r mly a n d s o o n. Howe v e r, S y e r s et al. (1973) we r e of t h e opi n ion t h at t h at t wo or mo r e pop u la t ion of s i t e s in s oils h a v i n g dif f e r e n t a f fi n i t y f or ad s o r a b t e (h e r e t h e Z n) mi gh t be t h e r e a s on for c u rv a t u r e.

T h e a ss u mp t ion of c o ns t a n t e n e rg y of ad s o r p t io n, a d s o r p t ion on s p e ci f ic s i t es a n d mo n ola y e r a d s o r p t ion on w h ich t h e s imple L a n g m u ir a d s o r p t ion i s o t h e r m e q u a t ion r eli e s (B o h n et al., 1985) w e r e f u lly (100%) satisfied in all tr e a t e d s oil s. T h e r 2 v al u es w e r e c ompa r a t i v ely h i gh er e n o ug h t o be r e lied. For e x ample t h e a lo n e Z n, Z n + F Y M, Z n + P M, Z n + B C p r od u c e d t h e r 2 v al u es of 0.95, 0.96, 0.98, 0.95, r e s pe c t i v el y, h owe v e r, d u e t o c ur v ili n e a r n a t ur e, t h e modifi e d L a n g m u ir mod e l w a s us e d for a ll s oil (Fi gure 4).

T h e bo n di n g e n e rg y, m a x im u m ad s o r p t ion a n d b u f f e r i n g c ap a ci t y we r e c a lc u la t ed b a s ed on s imple L a n g m u ir a d s o r p t ion i s o t h e r m mod e l w h e r e t h e i n i t ial I Z n A v a l u e s we r e di s r e g a r ded. Z n b u f f e r i n g c ap a ci t y is t h e po t e n t i a l of s oil t o r e s i s t c h a ng e s in Z n s oil s ol u t ion c o n c e n t r a t io n, w h e n Z n a dded or r e mo v e d f r om t h e s oil (Oz a n n e, 1980; J al a li, 2007). T h e s oil wi t h h i g h b u f f e r i n g c a pa c i t y c an r el e a s e Z n t o t h e s oil s ol u t ion s lowly a n d r e v e r s ible r e t e n t ion of Z n by c olloids of s oil d ur i n g s oil r e a c t ion (Ba rr ow a n d S h aw, 1975). As c ompa r e d t o n o n-tr e a t ed s oil, t h e am e n d e d s oils p r od u c ed h i gh er a d s o r p t ion ma x im u m, b u f f e r i n g c ap a ci t y a n d bo n di n g e n e r g ie s. T h e h i g h e r ad s o r p t ion m a x im u m a n d K L v a l u e s clo s e ly de t e r mi n e t h e st r e n g t h of a t t a c h me n t wi t h w h ich Z n is bo n d e d t o s oil p a r t i c les (Ba h l et al., 1986). Amo n g t h e a me n dme n ts, t h e h i g h e r ab s o r p t ion m a x im u m of B C i n dic a t e d i t s h i gh er po t e n t i a l of Z n a d s o r p t ion o v e r t h e F Y M a n d P M. How e v e r, t h e b u f f e r i n g c ap a ci t y did n ot su ppo r t i t s s u p r em a cy o v er F Y M a n d P M. T h e dif f e r e n t K L al s o i n dic a t e d t h at s i t e s for Z n a d s o r p t ion for t h e g i v en a me n dme n t s w e r e di f f e r e n t (J a v id, 1999) b u t s ur ely h i gh er t h a n n o n-tr e a t ed s oil s.

T able 2: Compar a tive Equilibrium par ameters of t he Langmuir adsorption isot h e rm equation for t he giv en amendmen ts in calca reous soil

P a r a m ete r | Z n a l o n e | Z n+P M | Z n+F Y M | Z n + B C
I nt e r c ept | 0.0391 | 0.0291 | 0.0246 | 0.0312
S l ope | 0.0008 | 0.0007 | 0.0006 | 0.0005
S q u a r e r | 0.96 | 0.98 | 0.963 | 0.957
Ad s o r p t ion m a ximum (b) | 1250 mg k g-1 | 1428 | 1667 | 2000
B o n di n g E n e r g y (K L) | 0.020 L m g-1 | 0.0240 | 0.0244 | 0.016
B u f f e r i n g C a pa c i t y (M B C) | 25.58 mg P Kg-1 | 34.36 | 40.65 | 32.05

Be c a us e c ur v ili n e a r i t y in all tr e a t e d s oil s, t h e a d s o r p t ion s e e ms t o h a v e f o r med m u l t i s i t e a n d m u l t il a y er a d s o r p t ion as e x p r e ss ed by t h e followi n g modi f ied L a ng m u ir M odel w a s appli e d a s g i v en by B o h n et al. (1985).

Where t he s ubscripts 1 and 2 refer to t he r e gion (or mec h a nism) 1 a nd 2 r e spec tively.

T he gr aph yielded two cur ve lin es for each trea t ed soil; one at low equilibrium [Z n] (EZ nC) a nd t he ot her at higher EZ n C. T he r e gion I r epres e n ting t he fir st s traig ht por tion may be associated to adsorption while at high EZ nC precipit a tion may be respon sible for t he s econd st r aight line in r e gion II (L in et al., 1983).

In con trast to sorption, t he EZ nC/(x/m) was lower for or ganically ame nded soil t han non-trea t ed soils (alone Z n) indicating hig h er adsorption in ame ndme nt soils. Among t he trea tme n t, t he BC had t he lowest EZ nC/x/m t han FYM a nd PM t r eated soil r e v ealing higher adsorption pot e n tial of B C.

F r e u ndl ich Ad sor p t ion I sot h erm E q uat ion

T he Fr e u ndlich equation implies t hat t he e n e rgy of t he adsorption on a u niform s urface is indepe nde nt of t he su r face cov e rage a nd t h at it dec rea se logarit hmically as t he f rac tion of t he cov e red s urface in c rea ses. T he dec rea se in ener gy of adsorption with t he incr ease in s urface cov e rage is due to su r face heterogeneity (B o h n et al., 1985). It is u su ally us ed in t he condition where t he Langmuir equation fails (B o h n e t a l., 1985). The equ a tion is express ed by t he following formula for Z n:

Wh e re K a nd n a re empirical con st a n t s, x/m is t he adsorption and t he E ZnC is t he equilibrium of Zn.

T he linear model of t he equ a tion is:

T he data we re plot t ed according to t he above lin ear model in F i gure 5 which produ ced linear r elations hips with r 2 v alu es of 0.97 to 0.98 ov er all trea t ed and non-trea t ed soils su g g e sting t h at both Langmuir and Fr e u ndlich models we re equ ally best fit for Zn adsorption in t he pres e nt s cenario.

Valu es of K repr e sen ting t he adsorption coefficient of soil were 136.65 in case of alone Zn (non-tr eated soil) which in c rea sed to 143.25, 195.89 and 176.21 with application P M, FYM a nd BC indica ting incr ease in adsorption with amendment applica tion (T a ble 3).

T able 3: Compa rative equilibrium pa rame t e rs of t he Fr e udlic h adsorption isot herm equ a tion for t he giv en trea tme n ts of alone Zn a nd with amendments

P a r a me t e r s | Z n a lo n e | Z n + PM | Z n + F YM | Z n a lo n e
I nt e r c ept | 2.136 | 2.156 | 2.292 | 2.246
S l ope | 0.377 | 0.403 | 0.357 | 0.399
S q u a r e r | 0.98 | 0.99 | 0.97 | 0.97
Ad s o r p t ion m a x im u m (K) | 136.65 | 143.25 | 195.89 | 176.21
N v a l u e | 2.65 | 2.48 | 2.80 | 2.50

S imilarly, t he v alue of N r epres e n ting in ver se of t he slope of gr aph we re higher for ame nded soil su g g e sting slower incr ease in adsorption with I ZA t han non-trea t ed soil wh e re s harp incr ease in adsorption we re obs e r v ed. Among t r eatmen ts, FYM h ad hig h er K followed by BC a nd PM su g g e stion more adsorption by FYM in t he pr e sent s t udy. S i n ce, t he lower n or hig h er 1/n v alue indicates more heterogeneity (G r e g o r y et al. 2005) s ug ges ting t hat application of org a nic ame ndme n ts in c rea sed t he h e t e rog e n eity of soil. J a v id (1999) reported t h at K is t he adsorbed specie t hat would s u st ain its con cen t r a tion in equilibrium solu tion. C ole et al. (1953) a nd Hol f o r d a n d M a t t i ng ly (1976) s ug ges ted t h at at low con cen t r a tion adsorption is e xpected while at higher con cen t r a tion t he dominant mechanism is precipit a tion.

Table 4: NPK and Zn concentrations of organic amendments

Nutrients | Unit | FYM | PM | Biochar
N | % | 2.13 | 1.83 | 0.63
P | % | 1.23 | 1.54 | 0.35
K | % | 2.86 | 1.69 | 2.37
DTPA Zn | mg kg-1 | 72.4 | 154 | 21.36
DTPA Cu | mg kg-1 | 26.0 | 49 | 15.0
DTPA Fe | mg kg-1 | 296 | 557 | 218

Yo ng ku et al. (2010) r epor t ed t hat dissolv ed org a nic mat t er (DOM) obtained f rom h umus soil (DOM H), rice st r aw (DOMR), and pig ma n ure (DO M P) r edu ced ma ximum Hg (me rcur y) adsorption capacity up to 40% over con trol in order of DOM H (250.00 mg kg-1) < D OMR (303.03 mg kg-1) < DO MP (322.58 mg kg-1) < con trol (416.67 mg kg-1) a nd incr eas ed its de sorption from t he soil. T a n i et al. (2010) reported t h at Andisols us ually fix la rge amou n ts of phosph a te on s urface-r eac tive sites but with addition of wa t e r-soluble or ganic ma t ter (WS O M) r edu ced t he binding s trength of phosphate a nd possibly indu ced s ubsequent phosph a te desorption a nd r ecomme nded t he combine use of ma n ure a nd inorg a nic phosphate fertilizer. T he same t r e nd was observed in our s t udy at low I Z nC e specially below < 20 mg Zn L-1 but at higher con cen t r a tion t he adsorption of Zn incr eas ed with org a nic ame ndme nt application. T his incr ease over con trol may be associated to in c rea se in t he c h a rg es sit es res ulting in hig h er ion e x c h a n ge capacit y. The incr ease in C EC with org a nic mat t er is an es tablis hed fact (B o h n et al., 2001). The higher C EC would have r e sulted in hig h er adsorption of Zn in our st udy.

Ack n o wle d gement

T he financial support of HEC as I ndigenous P h.D s t udy is highly acknowledg ed. The help of Dr. Dost Muhammad, Assistant Professor, Department of SES, the University of Agriculture, Peshawar in planning and data analysis of this paper is highly acknowledged.

Conflict of Interest

There is no conflict of interest.

Authors’ Contribution

Abida Saleem was student of PhD and worked on research study. Dr. Sajida Perveen was major supervisor of the research work who guided and supervised at all stages during research. Prof. Dr. Jamal Khan Khatak helped and guided in different aspects during work .

References

Adriano, D.C. 2001. Trace Element in Terrestrial Enviornments; Biogeohemistry, Bioavailability and Risk of metals. 2nd Edn, Spinger-Verlag, NewYork, pp. 626-668. http://dx.doi.org/10.1007/978-0-387-21510-5

Al-Kaysi, S.C. 2000. Effects of physical and chemical properties of carbonate minerals in some Iraqi soils in zinc fixation: Properties of carbonate minerals. Iraqi J. Agric. Sci. 30:53-72. (in Arabic).

Alloway, B.J. 2009. Soil factors associated with zinc deficiency in crops and humans. Environ. Geochem. Health. 31:537–548. http://dx.doi.org/10.1007/s10653-009-9255-4

Al-Tamimi, R.A. 2006. Zinc sorption by some Torrifluvents of sub-Saharian region south of Libya. Emirates J. Agric. Sci. 18:1-10

Bahl, G.S., N.T. Singh and A.C. Vig. 1986. Phosphate uptake by maize and wheat in relation to P adsorption characteristic of soil. J. Indian. Soc. Soil. Sci. 34:791-798.

Barrow, N.J. and T.C. Shaw. 1975. The slow reaction between soil and anions: 2. Effect of time and temperature on the decrease in phosphate concentration in the soil solution. J. Soil Sci. 119:167- 177. http://dx.doi.org/10.1097/00010694-197502000-00010

Bohn, H.L., B.L. McNeal and G.A. O’Gonnor. 1985. Soil chemistry. Wiley Interscience, New York.

Bohn, H.L., B.L. McNeal and G.A. O’Gonnor. 2001. Soil Chemistry. 3rd Ed. John Wiley and Sons, Inc. New York.

Catlett, K.M., D.M. Heil, W.L. Lindsay and M.H. Ebinger. 2002. Soil chemical properties controlling zinc activity in 18 Colorado soils. Soil Sci. Soc. Am. J. 66:1182-1189. http://dx.doi.org/10.2136/sssaj2002.1182

Clemente, R., D.J. Waljker, and M.P. Bernal. 2005. Uptake of heavy metals and as by Brassica Juncea grown in a contamination soil in Arnalcollar (Spain): The effect of soil amendments. Environ. Pollut. 136:46-58. http://dx.doi.org/10.1016/j.envpol.2005.02.019

Cole, C.V., S.R. Ols e n a nd C.O. Scot t. 1953. The nat u re of phosph a te sorption by calcium carbonates. J. Soil S ci. Soc. Am. P roc. 17:352-356. http://dx.doi.org/10.2136/sssaj1953.03615995001700040013x

Dahiya, S., A.V. Shanwal and H.A.G. Hedge. 2005. Studies on the sorption and desorption characteristics of Zn(II) on the surface soils of nuclear power plants sites in India using a radiotracer technique. Chemosphere. 60:1253-1261. http://dx.doi.org/10.1016/j.chemosphere.2005.01.089

Fox, R.L., a nd E.J. K amprat h. 1970. P hosphate sorption isot h e rm for t he evaluating t he phosph a te requireme nt of soils. Soil Sci. Soc. Am. P roc. 34:902-907. http://dx.doi.org/10.2136/sssaj1970.03615995003400060025x

Gregory, T., L.K. Chelsey and K.D. Shimizu. 2005. A critical examination of the use Hamadan, westren Iran. J. Environ. Geol. 53:365-374.

Gunary, D. 1970. A new adsorption isotherm for phosphate in soil. J. Soil Sci. 21:72-77. http://dx.doi.org/10.1111/j.1365-2389.1970.tb01153.x

Holford, I.C.R., and G.E.G. Mattingly. 1976. Phosphate adsorption and plant availability of phosphate. J. Plant Soil. 44:377-389. http://dx.doi.org/10.1007/BF00015889

Hussain, A., A. Ghafoor, and G. Murtaza. 2006. Use of model for phosphorus adsorption of some sodic soil of Punjab. Int. J. Agric. Biol. 8:242-248.

Hussain, A., G. Murtaza and A. Ghafoor. 2007. Derermination internal and external P requirement of wheat on calcareous soils by adsorption isotherm. Pakistan J. Agric. Sci. 44:103-109.

J alali, M. 2007. P hosphor us s tat us a nd sorption c h a rac t e ristics of some calca reous soils of Hamada n, we st e rn Iran. J. En viron. Geol. 53:365-374. http://dx.doi.org/10.1007/s00254-007-0652-7

Jalali, M., and A. Jalali. 2011. Competitive adsorption of trace elements in calcareous soils as affected by sewage sludge, poultry manure, and municipal waste compost. J. Environ. Earth. Sci. 63:731-739. http://dx.doi.org/10.1007/s12665-010-0742-9

Javid, S. 1999. Residual effect of phosphate fertilizer measured using the Olsen method in Pakistani soils. Ph.D. Diss. Uni. Reading, UK.

Johnson‐Beebout, S.E., J.G. Lauren and J.M. Duxbury. 2009. Immobilization of zinc fertilizer in flooded soils monitored by adapted DTPA soil test. Commun. Soil Sci. Plant Anal. 40:1842– 1861. http://dx.doi.org/10.1080/00103620902896738

Karimian, N., and G. R. Moafpourian. 1999. Zinc adsorption characteristics of selected soil of Iran and their relationship with soil properties. Commun. Soil Sci. Plant Anal. 30: 1722-1731. http://dx.doi.org/10.1080/00103629909370325

Khan, N. I., A.U. Malik, F. Umer and M.I. Bodla. 2012. Effect of tillage and farmyard manure on physical properties of soil. Int. Res. J. Plant Sci. 1(4):75-82.

Khoshgoftarmanesh, A.H., H. Shariatmadari, N. Karimian, M. Kalbasi and M.R. Khajehpour. 2006. Zinc efficiency of wheat cultivars grown on a saline calcareous soil. J. Plant Nut. 27: 1953–1962. http://dx.doi.org/10.1081/PLN-200030068

Kiekens, L. 1995. Zinc. In B.J. Alloway (ed.) Heavy Metals in Soils. Chapman & Hall, London. pp. 284–303. http://dx.doi.org/10.1007/978-94-011-1344-1_13

Lin, C., W. J. Busscher, and L. A. Douglas. 1983. Multifactor kinetics of phosphate reactions with minerals in acidic soils: I Modeling and simulation. Soil Sci. Soc. Am. J. 47:1097-1103. http://dx.doi.org/10.2136/sssaj1983.03615995004700060008x

Lindsay, W.L. 1974. Role of chelation in micronutrient availability. In E.W. Carson (ed.) The Plant Root and Its Environment. Univ. of Virginia Press, Charlottesville.

Manzoor, A. 2013. Critical soil solution phosphorus concentrations essential for plant growth in calcareous soil series. PhD thesis, SES department, The University of Agriculture Peshawar, Pakistan.

Mattigod, S.V., and G. Sposito. 1977. Estimated association constants for some complexes of trace metals with inorganic ligands. Soil Sci. Soc. Am. J. 41: 1092- 1097. http://dx.doi.org/10.2136/sssaj1977.03615995004100060015x

Obrador. A., J. Novillo, and M. Alvarez. 2003. Mobility and availability to plants of two zinc sources applied to calcareous soil. Soil Sci. Soc. Am. J. 67: 564-572. http://dx.doi.org/10.2136/sssaj2003.5640

Ozanne, P. G. 1980. Phosphate nutrition of plants- A general treatise. In The Role of phosphorus in agriculture. American society of Agronomy. Crop Science Society of America. Soil Science Society of America, Madison, WI. pp. 559-589.

Pérez-Novo, C., D. Fernández-Calviño, A. BermúdezCouso, J.E. López-Periago, and M. Arias-Estévez. 2011. Phosphorus effect on Zn adsorption-desorption kinetics in acid soils. Chemosphere. 83: 1028-1034. http://dx.doi.org/10.1016/j.chemosphere.2011.01.064

Perez-Novo, C., M. Pateiro-Moure, F. Osorio, and J. C. Novoa-Munoz . 2008. Influence of organic matter removal and competitive and non-competitive adsorption of copper and zinc in acid soils. J. Colloid Interface Sci. 322: 33- 40. http://dx.doi.org/10.1016/j.jcis.2008.03.002

Sanyal. S. K., S. K. De-Datta, and P.Y. Chan. 1993. Phosphate sorption-desorption behavior of some acidic soils of south and south-east Asia soil. Sci. Soc. Am. J. 57:937-945. http://dx.doi.org/10.2136/sssaj1993.03615995005700040011x

Shuman, L.M. 1986. Effect of ionic strength and anions on Zn sorption by two soils. Soil Sci. Soc. Am. J. 50:1438-1442. http://dx.doi.org/10.2136/sssaj1986.03615995005000060012x

Shuman, L.M. 1999. Organic waste amendments effect on zinc fractions of two soils. J. Environ. Qual. 28: 1442–1447. http://dx.doi.org/10.2134/jeq1999.00472425002800050008x

Solis, P., and J. Torrent. 1989. Phosphate sorption of calcareous vertisols and inceptisols of Spain. Soil Sci. Soc. Am. J. 53:456-459. http://dx.doi.org/10.2136/sssaj1989.03615995005300020026x

Soltanpour, P.N. 1985. Use of ammonium bicarbonate- DTPA soil test to evaluate elemental availability and toxicity. Commun. Soil Sci. Plant Anal. 16(3):323-338. http://dx.doi.org/10.1080/00103628509367607

Syers, J.K., M.G. Browman, G.W. Smillic and R.B. Corey. 1973. Phosphate sorption by soil evaluated by the Langmuir adsorption equation. Soil Sci. Soc. Am. Proc. 37:358-363. http://dx.doi.org/10.2136/sssaj1973.03615995003700030015x

Tani, M.A., K.T. Kato and M. Koik. 2010. Effect of organic ligands on phosphate adsorption and availability in Andisols of eastern Hokkaido, Japan. 19th World Congress of Soil Science, Soil Solutions for a Changing World 52 1 – 6 August 2010, Brisbane, Australia. Published on DVD.

Vega, F.A., E.F. Covelo, J.J. Vazguez and L. Andrade. 2007. Influence of mineral and organic components on copper, lead, and zinc sorption by acid soils.J Environ Sci Health A Tox Hazard Subst. Environ Eng. 14:2167-73. http://dx.doi.org/10.1080/10934520701629682

Viets, F.G. 1962. Chemistry and availability of micronutrients in soils. J. Agri. Food Chem. 10:174-178. http://dx.doi.org/10.1021/jf60121a004

Walker, D.J., R. Clemente, A. Roig and M.P. Bernal. 2003. The effect of soil amendments on heavy metal bioavailability in two contaminated Mediterranean soils. Environ. Pollut. 22:303-312. http://dx.doi.org/10.1016/S0269-7491(02)00287-7

Wang, J.J., and D.L. Harrel. 2005. Effect of ammonium, potassium and sodium cations and phosphate, Nitrate, and chloride anions on Zn sorption and lability in selected acid and calcareous soils. Soil Sci. Soc. Am. J. 69:1036-1046. http://dx.doi.org/10.2136/sssaj2004.0148

Wang, Z., P. Yin, R. Q u, H. C hen, C. Wa n g and S. Ren. 2013. Adsorption kin e tic s, t h e rmody n amics a nd isot h e rm of Hg (II) from aqu eous solu tions using buckwheat h ulls from Jiaodong of China. Food Chem. 136:1508–1514. http://dx.doi.org/10.1016/j.foodchem.2012.09.090

Xie, R.J., and A.F. Mackenzie. 1991. Effects of autoclaving on surface properties and sorption of phosphate and zinc in phosphate-treated soils. Soil Sci. 152(4):250-258. http://dx.doi.org/10.1097/00010694-199110000-00003

Yongku, Y., L.Li, and W. Dingyong. 2010. Effect of dissolved organic matter on adsorption and desorption of mercury by soils. J. Environ. Sci. 20:1097–1102.

Yusran, F.H. 2010. The Relationship between phosphate adsorption and soil organic carbon from organic matter addition. J. Trop. Soil. 15(1):1-10.

Zahedifar, M., N. Karimian and J. Yasrebi. 2010. Zinc desorption of calcareous soils as influenced by applied zinc and phosphorus and described by eight kinetic models. Comm. Soil Sci. Plant Anal. 41:897-907. http://dx.doi.org/10.1080/00103621003592408

Zhao, K., and H.M. Selim. 2010. Adsorption-desorption kinetics of Zn in soils: influence of phosphate. Soil Sci. 175:145-153. http://dx.doi.org/10.1097/SS.0b013e3181dd51a0