EFFECT OF SOIL PROPERTIES ON PHOSPHORUS SORPTION IN 13 SOILS WITH VARYING DEGREE OF WEATHERING

Vasileios Antoniadis, Revekka Koliniati, Evaggelia Golia, Spyridon Petropoulos

EFFECT OF SOIL PROPERTIES ON PHOSPHORUS SORPTION IN 13 SOILS WITH VARYING DEGREE OF WEATHERING

University of Thessaly, Department of Agriculture Crop Production and Rural Environment, Volos, Greece, vasilisrev@yahoo.com , Tel: ++302421093241 Abstract. Phosphorus sorption by soils depends on a series of soil properties, most important of which are pH, clay, organic matter, cation exchange capacity (CEC), amorphous Fe, Al and Mn oxides, as well as CaCO3. However, such properties may vary in soils of different degree of weathering. The aim of this work was to examine the soil properties that affect P sorption in 13 soils of Central Greece, evaluating the effect soil taxonomy may have on P sorption. We chose soils that differed considerably in pH (4 acidic and 9 alkaline) and in taxonomy (4 Alfisols, 4 Entisols, and 5 Inceptisols), and we conducted batch sorption tests with initial added element concentrations of C„=0-100 mg L-1 at 1-to-10 soil-to-solution ratio. We measured sorption at C„=100 mg L-1 (q100) and the distribution coefficient, Kd-100 (equal to q/C at C0=100 mg L-1). We also measured important soil physico-chemical properties, and the sorption indices were correlated with the measured soil properties. When soils were divided according to taxonomy, we found that Alfisols had significantly higher CEC, amorphous Fe and Mn oxides, and q100, but also significantly lower P extractability (water soluble-P and Mehlich-3-P). The other two soil orders did not have different soil properties. When soils were divided according to pH, exchangeable Ca, and the two above mentioned P extractability indices were lower in the acidic group of soils than in the alkaline. These results suggest that although differences in exchangeable Ca are entirely pH-related, differences in extractable P, as well as CEC, Fe and Mn oxides and q100 are taxonomy-related. We also found that Kd400.was significantly correlated only with exchangeable Ca (R2=0.304, p<0.05). Extractable P decreased with increasing sand, while organic C increased extractable P. We conclude that soil taxonomy is a key factor in understanding P sorption/extractability in soils, because highly weathered soils (here, Alfisols) have higher amorphous oxides content and this tends to enhance P retention by soils. Keywords: Extractable phosphorus; Alfisols; amorphous oxides.

INTRODUCTION Phosphorus is one of the most important nutrients, and its availability to plants depends on various soil properties, most important of which are pH, CaCO3, organic matter, and Al, Fe, and Mn oxides (Al-Rohily et al., 2013). There are two types of studies typically employed for estimating P availability: sorption studies and the use of P extractants. From such studies it has been reported that P tends to be strongly retained by soils in alkaline, as well as in acidic pH, for different reasons. In alkaline pH values, P is bound by CaCO3 (Naeem et al., 2013), while in acidic pH it is bound by soil oxides (Arai and Livi, 2013). Thus P availability is dramatically reduced in soil pH values that significantly depart from neutrality. Especially the role of oxides in P availability becomes more complicated because in weathered soils, oxides are of greater content but of higher crystallinity, and thus of lower reactivity. Thus there is a void in knowledge concerning the role of oxides from soils with variable degree of weathering. This is even

more evident in areas with low organic matter content (such as those in the southeast Mediterranean region), because in such soils one of the key factors controlling P availability is expected to have no significant effect. Thus the aim of this work was to study soil P mobility by using a series of soil extractants and batch sorption tests, in order to examine the role of various soil parameters in low organic matter soils with variability in the degree of soil weathering.

MATERIAL AND METHODS We obtained 13 soil samples from Central Greece, so that they may represent the three major taxonomic orders of different progress in weathering: 4 Entisols (newly developed soils, without a B horizon), 5 Inceptisols (with intermediate level of weathering), and 4 Alfisols (highly weathered). The soils were purposefully obtained from cultivated areas so that they may be of low organic matter. The soils were air-dried, passed through a 2-mm sieve, and analysed for some selected

physico-chemical properties (according to Rowell, 1994): pH (1:2.5 HO), particle size distribution (Bouyoucos hydrometer), organic C (wet oxidation), CaCO3 (calcimeter), exchangeable Ca (1 M CH3COONH4), cation exchange capacity (CEC, 1 M CH3COONa), and Fe and Mn oxides (ammonium oxalate) (table 1). We also conducted four P extractions: Water soluble (10

mM CaCl2, thereafter, WS-P), ammonium oxalate (thereafter, AO-P), Mehlich-3 (thereafter, M3-P), and Olsen (0.5 M NaHCO3, thereafter, Olsen-P). Then we also conducted batch sorption tests at 1 -to-10 soil-to-solution ratio with added phosphorus concentrations of C0=1-100 mg L-1. We measured P sorption, q, and P in the equilibrium solution, C. From these we

Table 1 - Selected physicochemical properties of the 13 studied soils

Soils Sand Clay pH Org . C CaCO3 Exch.Ca CEC Fe-ox mg kg- Mn-ox

% % % % mg kg-1 cmol kg-1 1 mg kg-1

A1 37.2 30.4 6.80 0.76 -- 933.77 16.41 3217 1077

A2 28.4 38.4 6.73 0.62 -- 640.00 23.10 1986 599

A3 18.4 42.4 7.21 1.0 1 0.24 947.3 7 32.30 1699 594

A4 22.4 38 7.46 0.77 0.30 804.64 25.61 1729 557

E1 68.4 24.4 6.67 0.70 -- 180.00 5.14 750 228

E2 12.4 38.4 7.53 0.84 3.88 2000.00 40.67 1919 422

E3 54.4 24.4 7.62 0.99 1.42 803.92 11.58 398 3 45

E4 58.4 28.4 7.75 1.2 3 0.45 1082.78 17.86 1064 228

I1 56.4 14.4 7.83 1.1 9 2.18 1490.07 10.55 472 335

I2 36.4 20.4 6.55 1.18 -- 450.00 6.37 1095 272

I3 31.6 22.4 7.07 0.68 0.26 570.00 7.21 1025 329

I4 64.4 26.4 7.64 0.88 0.37 631.58 3.86 435 297

I5 32 28.4 7.82 0.27 0.36 996.7 1 13.90 1005 4 74

A: Alfisols; E: Entisols; I: Inceptisols

Table 2 - Extractability and sorption indices of P in the 13 studied soils

Soils WS-P AO-P M3-P Olsen-P -Kd-100 #100

№ kg-1 mg kg-1 mg kg-1 mg kg-1 kg L-1 mg kg-1

A1 387.3 318.71 77.14 60.92 3.18 241

A2 360.8 339.73 60.89 51.47 3.56 282

A3 350.2 326.84 52.62 53.75 3.34 250

A4 379.9 318.36 63.05 53.17 2.81 218

E1 444.1 295.62 85.96 54.31 2.10 173

E2 398.0 328.62 59.34 41.44 3.33 246

E3 776.8 323.67 172.76 63.32 0.67 62

E4 450.0 339.73 159.88 73.72 3.12 237

I1 610.9 368.24 333.71 90.24 4.31 301

I2 410.3 321.19 82.55 54.93 0.81 75

I3 586.3 334.57 49.74 35.17 0.81 75

I4 1135.9 357.79 113.91 67.64 2.97 227

I5 353.0 326.14 71.10 48.21 3.08 235

A: Alfisols; E : Entisols; I: Inceptisols; WS -P: Water soluble-extractable P; AO -P: Ammonium oxalate-extractable

P; M3-P: Mehlich-3-extractable P; Olsen-P: Olsen-extractable P;

^d-1oo: Distribution coefficient of P sorption at C0=100 mg L1; ^u»: P sorption at C0=100 mg L1

calculated the distribution coefficient at C„=100 mg L-1 (Kd_100). This sorption index, along with q100 (sorption at C0=100 mg L-1) were further used in this work for studying P (they, along with the P extraction, are reported in table 2).

We then performed correlation analyses between soil properties versus P extractability and P sorption indices. Also average values in various soil divisions were compared for their significance at the level of p<0.05. All such analyses were conducted with the use of the statistical package Statgraphics.

RESULTS AND DISCUSSION

Soils varied considerably in their physico-chemical properties (table 1) and in their P extractability and P sorption (table 2). In an attempt to study these data according to soil taxonomy and to soil pH, we divided them and compared them statistically (table 3). We found that in Alfisols, clay content was significantly higher and sand significantly lower than the other two orders (Inceptisols and Entisols). This has also seemed to have affected CEC, which was significantly higher in Alfisols than in the other soils.

These differences in sand, clay and CEC may be incidental, but may also be a reflection of soil development conditions. This could be the case, should Entisols were recently developed in alluvial plains in short distance from the river-source or in sandstone and igneous felsic rock deposits (Fanning and Fanning, 1989). This hypothesis, although we can not support it in a definite manner, can not be ruled out. Alfisols also had a significantly lower WS-P and M3-P than the other soils, as well as significantly higher Fe and Mn oxides contents. The higher oxides content is connected with higher retention ability of soils for P (Igwe et al., 2010), and this was also observed here, with Alfisols having a significantly higher q100 average value relative to the other soils.

When soils were divided according to their pH (acidic vs. alkaline), we found that in

acidic soils pH was significantly lower (by the definition of this soil differentiation), as well as lower WS-P, M3-P, and exchangeable Ca. This seems to suggest that differences in exchangeable Ca is pH-affected only, as would rather be expected (i.e., acidic soils have a lower base saturation, and thus lower exchangeable Ca). However, the two P extractability indices (WS-P and M -P) were affected within this soil division due to both pH and taxonomy. Indeed, highly weathered soils typically have lower pH (this was not evident in our case, due to the fact that our "highly weathered soil—Alfisols—included two alkaline soils, A3 and A4), and also of higher

oxides content, which in turn are the colloidal phases mostly responsible for P retention.

These findings were also confirmed in our correlation analysis, where we compared soil properties against P extractability and sorption indices (table 4). Sand was proportionally and significantly correlated with WS-P, M3-P, and Olsen-P, meaning that light-textured soils are likely to extract more P. As expected by the sand effect, clay was inversely and significantly correlated with M -P. Also Fe oxides affected WS-P, but no other significant correlation between Fe oxides and P indices was generated.

Table 4 - Coefficients of determination, R2, of extractable P and sorption indices versus soil properties. A positive sign denotes a proportional relationship, and a negative sign denotes an inversely proportional relationship

WS-P AO-P M3-P Olsen-P ^d-100 ^100

Sand 0.355* 0.027 0.329* 0.413* 0.014 0.164

Clay -0.178 0.071 -0. 411* 0.206 0.122 0.157

pH 0.128 0.291 0. 249 0.159 0.119 0.089

Org. C 0.044 0.109 0.307* 0.379* 0.001 0.001

CaCO3 0.001 0.084 0.125 0.0012 0.061 0.036

Exch.Ca -0.019 0.161 0. 097 0.028 0.304* 0.249

CEC 0.222 0.017 0. 133 0.156 0.157 0.160

Fe-ox 0.356* 0.093 0. 255 0.108 0.097 0.117

Mn-ox 0.141 0.003 0.096 0.017 0.017 0.130

WS-P: Water soluble -extractable P; Mehlich-3-extractable P; Ols en -P: Olsen -sorption at C0=100 mg L-1; q100: P sorption

AO -P: Ammonium oxalate -extractable P; M3 -P: extractable P; ^d-100 : Distribution coefficie nt of P at Co=100 mg L-1; *Significant at the level ofp<0.05.

CONCLUSION Soil taxonomy is a key factor for understanding P mobility (recorded in this study as extractability and sorption) : Soils with more progressed development (even Alfisols, which, typical to soils in the Mediterranean region, are not

highly weathered compared to other soils, e.g., in the tropics), are of higher ability to retain P compared to newly developed (here, Entisols) and of intermediate weathering (here, Inceptisols) soils.

REFERENCES

Al-Rohily, K.M., Ghoneim, A.M., Modaihsh, A.S., Mahjoub, M.O., 2013. Phosphorus availability in calcareous soil amended with chemical phosphorus fertilizer, cattle manure and sludge

manure. Int. J. Soil Sci. 8, 17-24.

Arai, Y., Livi, K.J., 2013. Underassessed phosphorus fixation mechanisms in soil sand fraction. Geoderma 192, 422-429.

Fanning, D.S., Fanning, M.C.B., 1989. Soil Morphology, Genesis, and Classification. John Wiley and Sons, New York.

Igwe, C.A., Zarei, M., Stahr, K., 2010. Fe and Al oxides distribution in some Ultisols and Inceptisols of southeastern Nigeria in relation to soil total phosphorus. Environ. Earth Sci. 60, 1103-1111.

Naeem, A., Akhtar, M., Ahmad, W. 2013. Optimizing available phosphorus in calcareous soils fertilized with diammonium phosphate and phosphoric acid using Freundlich adsorption isotherm. Scientific World J. 2013, 680257 (article number).

Rowell, D.L., 1994. Soil Science: Methods and Applications. Prentice Hall, Harlow.

РЕЗЮМЕ

В. Антониадис, Р. Колиниати, Е. Голия, С. Петропулос

ВЛИЯНИЕ СВОЙСТВ ПОЧВЫ НА ПОГЛОЩЕНИЕ ФОСФОРА В 13 ТИПАХ ПОЧВ ПРИ РАЗЛИЧНЫХ УСЛОВИЯХ ВЫВЕТРИВАНИЯ

Университет Фессалии, Министерство сельского хозяйства, растениеводства и сельских территорий, Волос, Греция, vasilisrev@yahoo.com , Тел : ++302421093241

Поглощение фосфора почвами зависит от ряда свойств почв, наиболее важными из которых являются рН, глина, органическое вещество, мощностемкость катионного обмена (CEC), аморфные Fe, Al и Mn, оксиды, а также CaCO3. Однако такие свойства могут варьироваться в почвах в условиях разных атмосферных воздействий. Целью данной работы было изучение свойств почв, которые влияют на поглощение фосфора в 13 типах почв Центральной Греции, с учетом влияния таксономии. Мы выбрали почвы, значительно отличающиеся значением рН (4 кислые и 9 щелочные) и таксономии (4 Альфисоли, 4 Энтисоли и 5 Инсептисоли). Проведен ряд испытаний на поглощение с исходными концентрациями элементов C0=0-100 mg L-1 в соотношении почва-раствор 1 к 10. Были измерены поглощения при C0=100 mg L-1 (q100) и коэффициенте распределения, Kd 100, (равной (q/C at C0=100 mg L-1).

Мы также измеряли важные физико-химические свойства почвы и показатели сорбции были соотнесены с измеренными свойствами почв. Когда почвы были разделены по признакам таксономии, мы обнаружили, что Альфисоли имели значительно более высокий CEC, аморфные Fe и Mn оксиды, и q100, но также имели значительно более низкую экстрагируемость фосфора (водорастворимый-P и Mehlich-3-Р). Два других ряда не имели различий в свойствах почвы. Когда почвы были разделены в соответствии с рН, то обменный Са, и два вышеупомянутых показателя выделяемости фосфора были в кислотной группы почв ниже, чем в щелочной. Эти результаты свидетельствуют о том, что, хотя различия в обменном Са полностью связаны с рН, различия по экстрагируемому фосфору, а также CEC, Fe и Mn, оксидам и q связаны с таксономией. Мы также обнаружили, что K . достоверно коррелирует только с обменным Са (R2=0.304, p<0.05). Экстрагируемый фосфор уменьшается с увеличением песка, в то время как органический С увеличивал извлекаемый фосфор. Мы пришли к выводу, что таксономия почв является ключевым фактором в понимании фосфорной сорбции / экстрагируемости в почвах, так как крайняя эрозия почвы (здесь альфисоли) имеют наивысшее содержание аморфных оксидов, и это, как правило, способствует сохранению фосфора в почвах.

ТYЙIН

В. Антониадис, Р. Колиниати, Е. Голия, С. Петропулос

ТYРЛI АЗУ (ЭРОЗИЯ) ЖАFДАЙЫНДА 13 ЖЕРДЩ ТОПЫРАFЫНА ФОСФОРДЬЩ СЩ1Р1ЛУ1НЕ ТОПЫРАК КДСИЕТТЕР1НЩ ЭСЕР ЕТУ1

Фессалии университетi, Ауыл шаруашылыгы, встдж шаруашылыгы жэне ауыл аймацтар министрлт, Волос, Грекия, vasilisrev@yahoo.com , Тел : ++302421093241

Топырактыи фосфорды сiн,iруi топырактыи бiркатар касиеттерше байланысты, олардьщ ей мацыздылары рН, сазбалшык, органикалык заттектер, катиондык айырбас куаттылыгы (CEC), аморфтык Fe, Al жэне Mn тотыктары, сондай-ак CaCO3. Алайда м^ндай касиеттер TYрлi атмосфералык ыкпалдар жагдайында топыракта TYрлiше болуы MYмкiн.

Б^л ж^мыстъщ максаты топырактыи P сiиiруiне таксономияныи эсер етуiн ескере отырып, Орталык Грекияныи 13 жерiнiи топырагында Р сщруге ыкпал ететiн топырак касиеттерш зерттеу болды. Бiз pH (4 кышкыл жэне 9 сiлтi) жэне таксондардардыи (4 Alfisols, 4 Entisols жэне 5

Инсептисоли) болуымен бiршама ерекшеленетiн топырактарды тацдап алдык, жэне бiз С„=0-100 mgL-1 элементгердiи бастапкы шогырлануыныц топырак-ерmндi 1ден 10 катынасында сiиiрiлуiне бiрнеше сынак ЖYргiздiк. С0=100 mg L-1 ^100) жэне белу коэффициентi Кй-100, (q/C at С0=100 mgL-1 тец) кезшдеп сiиiрулер елшендi.Сонымен катар, бiз топырактьщ физикалык-химиялык касиеттерiн де елшедiк жэне сщру керсеткiштерi топырактыц елшеулi касиеттерiмен аракатынасы белгiлендi. Топырактар таксономия белгiлерi бойынша белiнген кезде Альфисолиде айтарлыктай жогары СЕС, аморфты Fe жэне Мп тотыктар, и q100 бар екеш, бiрак белiну Р (суга ерiгiш-Р жэне Mehlich-3-Р) темен екенш аныктадык. Баска екi топырак катарынан топырактыц TYрлi касиеттерi табылмады. Топырак рН-ка сэйкес белiнген кезде, айырбас Са жэне жогарыда аталган ею Р белiнушiлiк керсеткiшi топырактыц сштт тобына караганда, кышкылды тобында темен болды.

Б^л нэтижелер айырбас Са-да айырмашылык рН-пен толык байланысты болганымен, белiнетiн Р, сондай-ак СЕС, Fe жэне Мп тотыктар жэне бойынша айырмашылыктар таксономиямен байланысты. Сонымен бiрге, Кй400 тек айырбас Са-мен ^2=0.304, р<0.05) гана анык аракатынас орнататынын аныктадык. К^м кебейген сайын бвлiнетiн Р азаяды, ал органикальщ С алынатын Р-ны арттырды. Топырак таксономиясы топырактагы Р сiиiру/белiну TYсiнiгiнде мацызды фактор болып табылады, ейткеш топырактыц тым азуы (м^нда Альфисоли) кеп мелшердегi аморфты тотыкты камтиды, б^л эдетте, топыракта Р сакталуына ыкпал етедi.

Кiлттi свздер: бетнетш фосфор; Альфисоли; аморфты тотык