Steel Slag as an Iron Fertilizer for Corn Growth and Soil Improvement in a Pot Experiment1

Pedosphere 16(4): 519-524, 2006 ISSN 1002-0160/CN 32-1315/P @ 2006 Soil Science Society of China Published by Elsevier Limited and Science Press

Steel Slag as an Iron Fertilizer for Corn Growth and Soil Improvement in a Pot Experiment*' WANG Xian1i2 and CAI Qing-Sheng1i*2 College of Life Sciences, Nanjing Agricultural University, Nanjing 210095 (China). E-mail: wxy7674 @yahoo.com Department of Biology, Zhoukou Normal College, Zhoukou 466000 (China) (Received February 22, 2006; revised June 2, 2006)

ABSTRACT The feasibility of steel slag used as an iron fertilizer was studied in a pot experiment with corn. Slag alone or acidified slag was added t o two Fe-deficient calcareous soils at different rates. Results showed that moderate rates (10 and 20 g kg-l) of slag or acidified slag substantially increased corn dry matter yield and Fe uptake. Application of steel slag increased the residual concentration of ammonium bicarbonate-diethylenetriamine pentaacetic acid (AB-DTPA) extractable Fe in the soils. The increase of extractable Fe was usually proportional to the application rate, and enhanced by the acidification of slag. Steel slag appeared to be a promising and inexpensive source of Fe to alleviate crop Fe chlorosis in Fe-deficient calcareous soils. Key Words:

corn growth, iron fertilizer, pot experiment, soil improvement, steel slag

INTRODUCTION Application of industrial wastes as fertilizer has become a common practice in agriculture (Liu et al., 2002; Yang and Zhang, 2005; Zhang et al., 2003). As a by-product of steel factories, slag as well as its disposal poses environmental concerns. However, because the waste contains high levels of Fe, Mn, K, and P, and because the contents of Cd, Pb, and other harmful trace metals in slag are at safe levels to the environment, according to GB8173-87of China, slag is a potential source of plant nutrients, especially in the areas where plant iron chlorosis is a problem. Iron chlorosis is widespread in many crops grown on calcareous soils, and it results in not only significant yield losses (Chen et al., 2005; Clark, 1982;Si et al., 2004;Vose, 1982;Yu et al., 2005), but also iron malnutrition in many developing nations (WHO, 2002). Iron, a sensitive element, markedly influences plant growth (Bienfait et al., 1985). Several reports show that addition of Fe industrial by-products to soils tends to raise Fe availability and alleviate Fe deficiency in plants (Mortvedt, 1988; Wallace et al., 1982; Sikka and Kansal, 1994). Anderson and Parkpian (1984)applied Fe dust, a by-product of a steel plant containing 430 g Fe kg-', as Fe fertilizer to an alkaline soil, with or without sulfuric acid, and found that the application of this waste increased the dry matter yield of sorghum. Similarly, the use of Ferrosul (a mixture of sulfuric acid and iron sulfates) on calcareous soils corrected Fe chlorosis in corn and alfalfa (Stroehlin and Berger, 1963). Slag, containing a large amount of Fe oxides including Fe(II), can be of great agricultural importance wherever Fe deficiency symptoms are found. In addition, the waste may also be a source of available Mn, K, and P, which are useful nutrients for plants. In China, however, due to its high content of soluble silicon, slag has been mainly investigated as a source of silicon fertilizer in rice field experiments, where it increased the available Si (Liu et al., 2002; Yang and Zhang, 2005; Zhang et al., 2003). The objective of the present study was to evaluate the feasibility of slag as Fe fertilizer, especially in the area where the risk of iron deficiency is present. *lProject supported by the National Natural Science Foundation of China (No. 30270800). *'Corresponding author. E-mail: [email protected].

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MATERIALS AND METHODS

A steel slag sample, obtained from the Wuyang Steel Factory, Henan Province, China, was ground into a fine powder with pH and EC (Rhoades, 1996) being determined in a suspension with a s1ag:water ratio of 1:2.5 using a Metrohm 320 pH meter and a 644 conductor meter, respectively. The chemical composition of the steel slag is presented in Table I. The compound contained about 640 g kg-' Fe oxides, and a considerable amount of Mn and P. TABLE I Chemical composition of steel slag from t h e Wuyang Steel Factory, Henan Province, China Element

Content

Fe3+ Fe2+ Ca Si

g kg-' 316.07 152.35 44.60 6.22

Element Mn K

P Mg

Content

Element

Content

g kg-' 8.05 2.57 1.58 1.51

Na Zn Al V

g kg-' 1.41 0.32 0.58 0.45

Element

Content

S

g kg-' 1.40

Two calcareous soils, a sandy loam and a loamy sand, were collected from Shangqiu County and Kaifeng County of Henan Province, China, respectively, areas with severe iron chlorosis symptoms. Some characteristics of the soils are shown in Table 11. TABLE I1 Some physical and chemical propertiesa) of two calcareous soils selected Soil texture

pH

Sandy loam Loamy sand

8.0 7.9

EC

OM

N

CaC03

g kg-' 0.3 0.3

-

2.6 5.0

dS m-' 10.1 10.7

449 306

P

K

Fe

12.3 12.2

198.6 360.2

mg kg-' 3.9 9.8 3.4 10.4

Mn

Zn

Cu

1.3 1.3

1.3 1.2

a)pH: in saturated paste; EC: electrical conductivity in saturated paste extract; OM: organic matter from t h e Walkley and Black method; N: total N by the Kjeldahl method; C a C 0 3 : calcium carbonate from titration with NaOH; P : measured with the ascorbic acid method; K: extracted with 1 mol L-' ammonium acetate; Fe, Mn, Zn, and Cu: extracted with ammonium bicarbonate-diethylenetriamine pentaacetic acid (AB-DTPA).

A pot experiment was conducted in a greenhouse. Soil treatments in three replicates included 0, 10, 20, and 40 g kg-' slag (To,T I , T2, and T3, respectively), 10 and 20 g kg-' slag acidified to pH 2.5 and mixed with soil (Tal and Ta2, respectively), 10 g kg-' slag acidified to pH 2.5 and placed a t the bottom of pots as a uniform layer 5 cm in height (Tam'),and 5 mg Fe kg-' of soil from iron ethylenediamine di(o-hydroxyphenylacetic) acid (FeEDDHA) (Tseq)injected into the soil by a syringe. Wager pots, 20 cm in height and 20 cm in diameter were used in the experiment, and four seeds of corn (variety 647 Single Cross) were sown in each pot containing 5 kg of soil. Seedlings were thinned to 2 when they were about 10 cm high. During the growth period, pots were irrigated with distilled water when needed. All pots received 50 mg N kg-' in the form of ammonium nitrate one week after thinning the seedlings. The plant shoots were harvested 10 weeks after germination. Shoot dry matter yield was determined after the shoots were dried at 70 "C for 48 h. Sub-samples of dry shoots were ground, dry-ashed in a furnace at 550 "C, and then extracted with 2 mol L-' HC1. Concentrations of Fe, Mn, Zn, and Cu in the extracts were measured by an atomic absorption spectrophotometer, whereas the concentration of K was determined by a flame photometer and P by a spectrophotometer. Soil samples from each pot were analyzed for ammonium bicarbonatediethylenetriamine pentaacetic acid (AB-DTPA) extractable Fe and Mn. The EC and pH were also determined in a suspension of 1:2.5 (soi1:water) as described earlier. Data were analyzed using analysis of variance (ANOVA) with MSTATC and SAS software. Duncan's

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521

multiple range test was used for mean separation when the ANOVA was significant ( P 5 0.05). RESULTS AND DISCUSSION

C o r n d r y m a t t e r yields When the sandy loam soil was treated with 20 g kg-' slag (Tz), corn dry matter yield, as compared to the control (To),increased significantly ( P 5 0.05) (Table 111). Further increasing the rate of application (T3), however, revealed no significant differences from dry matter yield of the control, possibly due to the high pH of slag, which could slightly enhance soil pH (Liu e t al., 2002; Yang and Zhang, 2005). TABLE 111 Dry matter yield and uptake of Fe, Mn, Zn, Cu, P, and K in corn for the pot experiment with two calcareous soils treated with steel slag or iron ethylenediamine di(o-hydroxyphenylacetic) acid (FeEDDHA) Soil

Treatmenta)

Dry weight

Uptake Fe

Mn

Zn

P

K

9.58 bc 13.61 a 9.84 b 13.26 a 13.50 a 7.52 c 8.44 c

116.30 c 118.36 c 119.43 c 209.27 a 168.99 b 110.60 c 119.61 c

7.57 c 12.34 a b $2.42 a b 10.75 b 13.55 a 13.53 a 12.27 a b

37.00 c 206.53 b 278.05 a 267.05 a 220.95 b 274.40 a 251.56 a

g pot-'

Sandy loam

To Tseq

Ti Ta1 Tz Taz T3

Loamysand

To Tseq

T1 Ta1 Tam1

Tz Taz

cu

4.68 cdb) 5.76 b 4.76 c 5.73 b 6.39 a 3.35 e 4.38 d

0.84 c 1.21 a 0.87 c 1.07 b 1.19 a 0.66 d 0.93 c

0.46 a 0.42 a b 0.40 ab 0.41 ab 0.40 ab 0.26 d 0.34 c

mg pot-l 0.40 c 0.10 bc 0.78 a 0.13 b 0.38 c 0.15 a 0.52 b 0.14 a 0.38 c 0.14 a 0.29 d 0.09 c 0.27 d 0.11 b

3.04 e 5.70 d 7.94 a 6.86 b 6.28 c 7.54 a 6.44 c

0.63 c 0.77 c 1.02 b 0.77 c 1.01 b 1.27 a 0.95 b

0.30 c 0.44 a 0.44 a 0.33 bc 0.33 bc 0.43 a 0.41 ab

0.63 b 0.50 c 0.54 c 0.42 d 0.36 de 0.72 a 0.31 e

0.07 c 0.15 b 0.20 a 0.19 a 0.18 a 0.19 a 0.14 b

")To, T I , Tar and T3: 0, 10, 20, and 40 g kg-' slag, respectively; Tal and Ta2: 10 and 20 g kg-' slag acidified to pH 2.5 and mixed with soil, respectively; Taml: 10 g kg-' slag acidified t o pH 2.5 and placed at the bottom of pots as a uniform layer 5 cm in height; Tseq: 5 mg Fe kg-' of soil from FeEDDHA. The corn plants in Taml treatment of sandy loam were died 1 week after thinning and two replicates in the T3 treatment of loamy sand were damaged accidentally. b)Values followed by the same letter(s) in each column for each soil are not significantly different at P 5 0.05 using Duncan's multiple range test.

Corn dry matter yield with 10 g kg-' slag treatment (TI) was not significantly different from the control (To), and was significantly less ( P I: 0.05) than the treatment with 10 g kg-' acidified slag (Tal) for the sandy loam (Table 111),suggesting that the decrease of soil pH might increase corn growth. Ryan and Stroehlin (1976) reported that although jarosite material from a copper production process was ineffective on sorghum yield, a combination of this material with H2SO4 proved to be more effective than either material alone and as effective as conventional materials, i e . , FeS04.7H20 with about 200 g Fe kg-' and FeEDDHA with about 70 g Fe kg-l. In the present study with the sandy loam, dry matter yield significantly decreased in 20 g kg-l acidified slag treatment (Ta2) compared to the control (Table 111),possibly due to a significant increase ( P 5 0.05) in EC of the soil (Table IV). This may also be the reason why the plants died in the treatment with 10 g kg-' acidified slag placed a t the bottom as a uniform layer (Taml). Because soil Fe availability normally decreases with increasing salt levels, superfluous salts may result in a decrease of yield and an increase of chlorosis in plants (Dahiya and Singh, 1979; Si e t al., 2004). In chlorosis studies, elevated EC generated by acid paste also disrupted plant growth (Liu e t al., 2005; Loeppert e t al., 1994), despite the fact that this observation has not been reported elsewhere.

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TABLE IV Residual ammonium bicarbonate-diethylenetriamine pentaacetic acid (AB-DTPA) extractable Fe and Mn, and pH and EC in two calcareous soils treated with steel slag or iron ethylenediamine di(ehydroxypheny1acetic) acid (FeEDDHA) Treatmenta)

Sandy loam Fe

Loamy sand Mn

- mg kg-'

To

Ta1

7.34 c 7.42 c 7.34 c 7.42 c

Tam1

-

-

16.09 b 24.96 a 22.05 a b

8.50 b 9.80 a 8.00 bc

Ti

Tz TaZ

T3

EC

Fe

dS m-' 2.09 b 2.11 b 2.05 b 2.13 b

- mg kg-'

7.48 a b 7.37 b 7.37 b 7.42 b

-

9.50 cb) 15.88 b 10.26 c 17.06 b

Tseq

PH

~

7.55 a 7.24 c 7.55 a

-

2.18 b 3.20 a 2.00 b

Mn

PH

EC

-

10.30 d 14.47 c 12.93 cd 25.18 a 17.30 b 18.45 b 27.85 a

8.93 b 8.45 b 11.33 a 9.34 b 8.86 b 11.33 a 8.37 b

7.57 7.62 7.51 7.56 7.52 7.62 7.52

-

-

-

ab a a

ab b a

b

dS m-i 2.39 b 2.52 b 2.67 a b 2.70 a b 2.50 b 2.67 a b 3.09 a

-

")To, T I , Tz, and T3: 0, 10, 20, and 40 g kg-' slag, respectively; Tal and Ta2: 10 and 20 g kg-' slag acidified t o pH 2.5 and mixed with soil, respectively; Tam': 10 g kg-' slag acidified t o pH 2.5 and placed at the bottom of pots as a uniform layer 5 cm in height; TSeq:5 mg Fe kg-' of soil from FeEDDHA. The corn plants in Tam' treatment of sandy loam were died 1 week after thinning and two replicates in the T3 treatment of loamy sand were damaged accidentally. b)Values followed by the same letter(s) in each column are not significantly different at P 5 0.05 using Duncan's multiple range test.

For the loamy sand soil, the maximum yield response (7.94 g pot-') with 10 g kg-' slag treatment (TI) was significantly greater ( P 5 0.05) than, and over twice the yield of, the control (Table 111). Although the treatment Tseqwas significantly greater ( P 5 0.05) for dry matter yield than the control, the other treatments were all significantly greater than Tseqfor the loamy sand soil. It is possible that FeEDDHA used in Tseqwas not a very effective Fe source for alkaline soils. Hergert et al. (1996) found that FeEDDHA (Fe, 0.5 kg ha-') was not as effective as FeS04.7H20 (Fe, 11 kg ha-') in promoting growth at a high pH site for non-tolerant hybrid corn. The treatment Tarn' also significantly increased yield ( P 5 0.05), but significantly less ( P 5 0.05) than Tal for the loamy sand soil. The H2SO4 applied into soils reacts with free carbonates in the soils and lowers the pH in the application zone. Consequently, the reduced carbonate content and lower pH of the soils make Fe more accessible to the plant (Zhang et al., 1991). However, high rates of H2S04 may either drastically lower the pH or relatively increase salt content of the soil or both, which in turn may result in plant yield reduction (Dahiya and Singh, 1979; Si et al., 2004).

Mineral uptake in corn Results from the sandy loam soil showed that the Fe uptake in corn plants was significantly higher ( P 5 0.05) in the treatments Tseq,Tal, and T2 compared to all other treatments, whereas the treatment Ta2 was significantly lower ( P 5 0.05) than all other treatments (Table 111). In the loamy sand soil, however, Fe uptake in the treatment T2 was significantly greater than ( P 5 0.05), and twice as much as, the control. Meanwhile, Fe uptake in the treatments Tseqand Tal were not statistically different from the control. In contrast to Fe uptake, in the sandy loam soil Mn uptake of chlorotic plants grown in the control was greater than that of the normal green plants in all other treatments (Table 111).The depressed Mn uptake in the green plants was likely due to the antagonistic effect between Fe and Mn (Alam et al., 2001). Most of the investigations on the interaction between Fe and Mn in plants indicate a negative correlation between Fe and Mn accumulation in the shoots of susceptible cultivars (El-Jaual and Cox, 1998; Si et al., 2004). Also, in some plants high concentrations of Fe depress absorption of Mn (Kohno and Foy, 1983; Si et al., 2004). In the treatments Tal and Tz of sandy loam and the treatments TI, Tal, Tam', and T2 of loamy

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523

sand, the uptake of Cu, P, and K were significantly greater than the control ( P 5 0.05), while the Zn uptake was significantly greater in the treatment Tal of sandy loam and the treatment T2 of loamy sand than the control (Table 111). This may be resulted from the higher dry matter yields of these treatments and the increase of Zn, Cu, P, and K in soils with the addition of slag. As for the uptake of Zn, Cu, P, and K in slag by plants, a thorough investigation is necessary.

Soil residual Fe For both calcareous soils tested a significant increase ( P 5 0.05) in plant dry matter yield with FeEDDHA application (TSeq)was observed (Table 111) and corn plants in the controls were chlorotic while the plants in all other treatments appeared normal green, confirming that Fe deficiency existed in the calcareous soils used in this study. Soil residual AB-DTPA extractable Fe was significantly greater ( P 5 0.05) than that of the control after crop harvest for all treatments except TI and Taml in the sandy loam and TI and T3 in the loamy sand (Table IV). It usually increased with application of slag, and was significantly increased ( P 5 0.05) by the acidification of slag (Table IV). This suggested that slag containing large amounts of Fe could be a promising and inexpensive source of Fe to alleviate crop Fe chlorosis in the Fe-deficient calcareous soils. To validate this hypothesis, however, a thorough investigation with various crops in various field conditions is required.

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