Evaluation of different extractants for the estimation of bioavailable selenium in seleniferous soils of Northwest India.
Selenium is an important trace element found in most soils. Consumption of any vegetation species containing >5 mg Se/kg, the maximum permissible level, results in health hazards to animals and humans (Anderson et al. 1961; Yang et al. 1983; Dhillon and Dhillon 1997). Soils containing >0.5 mg Se/kg have been found to produce vegetation containing Se more than the maximum permissible level for animal consumption (Dhillon et al. 1992). Selenium exists in soil in several chemical forms that differ in their solubility and availability to plants. Total soil Se has proved to be of very little value in predicting plant uptake (Lindberg and Bingefors 1970). The soil solution is continuously replenished with Se as it is removed by plants or lost from the soil-plant system. Simulating the continuous depletion of Se, multiple extractions with 0.25 M KCI could extract 60-65% of total Se present in alkaline seleniferous soils (Dhillon and Dhillon 2004). Williams and Thornton (1973) reported highly significant relationship between plant Se concentration and EDTA-extractable Se for some potentially seleniferous organic soils from Ireland. Soltanpour and Workman (1980) advocated the use of AB-DTPA (ammonium bicarbonate-diethylene triamine penta acetic acid) extractable Se as a plant availability index for soils from North Dakota, USA. These studies indicate that suitability of a particular extractant for extracting available Se is related to the type and nature of the soil.
Some pockets of seleniferous soils-producing vegetation containing >5 mg Se/kg dry matter have been identified in Hoshiarpur and Nawanshehar districts of Punjab State in north-western India (Dhillon and Dhillon 1991). These soils have developed due to deposition of Se-rich material transported through flood water from nearby hills of the Shiwalik range. Parent material of the soils is derived from upper Shiwalik rocks composed mainly of polymictic conglomerates of variable composition containing many unstable materials such as granite, basalt, limestone, etc. (Dhillon and Dhillon 2003). Total Se concentrations in these soils range from 0.50 to 4.55 mg/kg. Animal and human health has been adversely affected by consuming plants grown on seleniferous soils (Dhillon and Dhillon 1997). To find an index of bioavailable Se in seleniferous soils of Punjab, there is need to ascertain the suitability of different extractants in simulating uptake of Se by plants. Laboratory and greenhouse experiments were, therefore, conducted to compare the efficacy of different extractants with that of plants in extracting Se from soil.
Materials and methods
Fifteen surface (0-0. 15 m) samples of seleniferous soils were collected from sites located in villages of Nazarpur (2) and Simbly (4) in Hoshiarpur, and Jainpur (4), Barwa (3), Mehindpur (1), and Bhanmazara (1) in Nawanshehar districts of Punjab. The soil samples were air-dried in shade, ground to pass through a 2-mm sieve, and stored for conducting greenhouse experiments. Physico-chemical characteristics of the soils reported in Table 1 were determined by following standard procedures. About 200 g soil from each bulk soil sample was further processed to pass through 100-mesh sieve for determining the amount of Se extracted by different extractants. Hot water soluble, 0.5 M [Na.sub.2]C[O.sub.3] extractable, and AB-DTPA extractable Se were determined by following the methods described by Jump and Sabey (1989). Soil samples were also extracted with 0.25 M KC1 and 0.1 M K[H.sub.2]P[O.sub.4] solutions (Chao and Sanzolone 1989). Isotopically exchangeable Se was determined by following the method given by Cary et al. (1967). Brief description of these methods is given below:
(a) Hot water soluble Se: 10g soil was taken in a conical flask (250 mL capacity), suspended in 50mL of glass distilled water, and refluxed over a boiling water bath for 30 min. Soil suspension was then filtered through a Whatman filter paper No. 42 and Se in the filtrate was analysed fluorometrically (Bio-Rad's VersaFluor[TM] Fluorometer).
(b) 0.5 M [Na.sub.2]C[O.sub.3] extractable Se: 5 g soil was shaken with 20 mL of 0.5 M [Na.sub.2]C[O.sub.3] solution for 30 min on a reciprocating shaker and the supernatant solution was analysed for Se.
(c) AB-DTPA extractable Se: 10g soil was shaken with 20mL of 1 M N[H.sub.4]HC[O.sub.3] and 0.005 M DTPA for 15 min on a reciprocating shaker and the supernatant was analysed for Se.
(d) 0.25 M KC1 extractable Se: 1 g soil was shaken with 25 mL of 0.25 M KC1 for 30 rain on an end-to-end shaker. The soil suspension was centrifuged and the supernatant solution was collected for analysis of Se.
(e) 0.1 M K[H.sub.2]P[O.sub.4] extractable Se: 1 g soil was extracted with 25 mL of 0.1 M K[H.sub.2]P[O.sub.4] solution by shaking for 30 min on an end-to-end shaker. The supernatant solution was analysed for Se.
(f) Isotopically exchangeable Se: 100 g soil was labelled with [sup.75]Se as sodium seleno-sulfate (100-200 mCi/g Se)@2.4 KBq/g soil by subjecting to alternate wetting and drying cycles over a period of 1 month. After air drying, the soil was ground to pass through 100-mesh sieve and a 2.5-g portion of the soil was extracted with 25mL of 0.1 M sodium selenite. The extract was radio-assayed for [sup.75]Se using multichannel [gamma]-ray spectrometer (Berthold make, model LB 2104).
Se uptake by plants
To determine the amount of plant-available Se, raya (Brassica juncea) followed by maize (Zea mays L.), and wheat (Triticum aestivum L.) followed by lowland rice (Oryza sativa L.), respectively, were grown in different soils in the greenhouse. The 2 crops were, however, grown after a gap of 4 months. Four kg of well-ground soil was placed in polyethylene-lined earthen pots. The soil in each pot was mixed with recommended levels of N, P, and K supplied through urea, K[H.sub.2]P[O.sub.4], and KC1, respectively. Each treatment was replicated 4 times. Seeds of raya (cv. RL 1359), maize (cv. Parbhat), and wheat (cv. PB 343) were sown in soil at field capacity moisture, and five 25-day-old seedlings of rice (cv. PR 114) were transplanted in pots in which 15 mm depth of water was maintained at the soil surface. After germination, when the seedlings of raya, wheat, and maize were well established, 5 plants were retained in each pot. In pots with raya, wheat, and maize, irrigation was applied to maintain soil moisture levels near field capacity. Enough water was applied almost daily to pots with rice to maintain 15 mm depth of water at the soil surface. Raya, wheat, maize, and rice plants were harvested after 52, 55, 54, and 50 days after sowing/transplanting, respectively. Samples of above-ground portion were collected and washed free of any contamination. After air-drying, the samples were dried in an oven at 60 [+ or -] 5 [degrees]C to a constant weight and dry matter yield was recorded.
Analysis of soil and plant samples
For analysis of Se and other nutrients, plant samples were ground in Willey grinding mill. Soil (0.25 g of 100-mesh size) and plant (0.5 g) samples were digested in a 10mL mixture of perchloric and nitric acids in the ratio of 2 : 5. The acid digest was subjected to Se analysis by following the method described by Levesque and Vendette (1971). A known volume of the digest was taken in culture tubes to which 2 mL of 1 N HCI was added and the contents were heated at 90[degrees]C for 30 min on a thermostatically controlled heater (Kjel-plus) for transforming selenate into selenite. After cooling to room temperature, 2 mL of 0.04 M EDTA solution was added. Tubes were again heated at 60[degrees]C for 30 min. After cooling the tubes to room temperature, 1 mL of freshly prepared 0.1% diaminonaphthalene (DAN) solution was added and the tubes were again heated at 60[degrees]C for 30 min. Thereafter, the contents of culture tubes were transferred to 125-mL separatory funnels and 5 mL of cyclohexane was added. The samples were shaken vigorously for 1 min and when the 2 layers separated, the aqueous phase was drained off. A blank was also prepared by following the above procedure. Fluorescence emitted by the cyclohexane layer was measured by fluorometer (Bio-Rad's VersaFluor[TM] Fluorometer) fitted with an excitation filter of 364 nm and emission filter of 523 nm wavelength. Standard curve was prepared by taking 1 mL of sodium selenite solution containing 0, 20, 40, 60, 80, 100, 120, and 250 [micro]g Se/L. Available S and P in the soil were estimated by extracting 1 g soil with 20 mL of 0.5 M NaHC[O.sub.3]. Plant digests and 0.5 M NaHC[O.sub.3] extracts were analysed for S (Chesnin and Yien 1950) and P (Watanabe and Olsen 1965).
Results and discussion
The soils were alkaline in reaction with pH ranging from 7.7 to 8.2, organic carbon from 0.5 to 1.0%, calcareous and silty loam to silty clay loam in texture. Total Se concentration of the soils varied from 0.6 to 3.1 [micro]g/g soil (Table 1). The soils containing >0.5 [micro]g Se/g generally produce fodders containing Se more than the maximum permissible level of 4-5 [micro]g/g for animal consumption and are considered as seleniferous (Dhillon et al. 1992).
Efficacy of different extractants
Available Se concentration of seleniferous soils as extracted by different reagents is reported in Table 2. Among the various extractants, 0.5 M [Na.sub.2]C[O.sub.3] was found to extract the smallest, and isotopically exchangeable the largest, amount of Se. On the basis of average values of Se concentration, different extractants could extract Se from seleniferous soils in the following decreasing order: isotopically exchangeable > 0.1 M K[H.sub.2]P[O.sub.4] > 0.25 M KCI > hot water [greater then or equal to] AB-DTPA > 0.5 M [Na.sub.2]C[O.sub.3]. The smallest or the next slightly greater amount of Se extracted by all the extractants was invariably from soil No. 6 (Simbly-4), which incidentally also contained the smallest amount of total Se (0.6 [micro]g/g) (Table l). The largest amount of extractable Se came from the soils that contained total Se >2.0 [micro]g/g. Jump and Sabey (1989) have reported that among different extractants 0.5M [Na.sub.2]C[O.sub.3] extracted the greatest amount of Se, which was attributed to high organic carbon content of the soils (1-11.2%), but in the present investigation, soils had relatively low organic matter content (0.5-1%). The findings of Jump and Sabey (1989) that hot water and AB-DTPA had similar extracting ability are, however, in line with our observations. Soltanpour and Workman (1980), however, observed that AB-DTPA extracted about 31% more Se than hot water from the mine and overburden samples. Sharmasarkar and Vance (1997) reported that the total amount of desorbed Se in different extractants followed the order: K[H.sub.2]P[O.sub.4] >> NaOH >> AB-DTPA > hot water > deionised water. These authors observed that selenite was the dominant inorganic species in AB-DTPA and K[H.sub.2]P[O.sub.4] extracts and selenate was the major species in deionised water, hot water, and NaOH. As 0.25 M KCl is known to extract the non-specifically adsorbed selenate form of Se (Chao and Sanzolone 1989), it extracted amounts of Se greater than hot water soluble, as well as AB-DTPA extractable Se in the present investigation. One criterion that seems to control the amount of Se extracted by different extractants is the soil:solution ratio (Fujii et al. 1988).
Hot water soluble Se was significantly correlated with 0.25 M KC1 extractable (r = 0.710, P <0.01) as well as total Se concentration of the soils (r = 0.710, P <0.01). Amount of Se extracted with 0.1 M K[H.sub.2]P[O.sub.4], which mainly represented exchangeable Se, was significantly correlated with isotopically exchangeable (r = 0.562, P <0.05), [Na.sub.2]C[O.sub.3]-extractable (r = 0.619, P <0.05), and total Se concentration (r = 0.666, P <0.01) of the soils.
Hot water extractable Se was positively correlated with electrical conductivity (r = 0.514, P <0.05), and isotopically exchangeable Se was negatively correlated with organic matter content (r = -0.556, P <0.05) of the soils. Organic matter possibly effects through chelating of selenite by proteins, fulvic acids, or other organic compounds that are continuously produced in soils through the activities of microorganisms (Hamdy and Gissel-Nielsen 1976).
Bioavailability of Se from seleniferous soils
Availability of Se to different crops was determined by growing raya followed by maize and wheat followed by rice in different soils under greenhouse conditions. Dry matter yield and Se concentrations of different crops are reported in Tables 3 and 4.
Se availability under raya and maize
Dry matter yield of raya in the experimental soils varied from 4.4 to 7.8 g/pot and that of maize varied from 14.1 to 19.8 g/pot (Table 3). The experimental soils differed significantly with respect to availability of Se to both the crops as indicated by wide range in Se concentration in raya (1.5-86.6 [micro]g/g) and maize (l.5-8.6 [micro]g/g) shoots. Greatest value of Se concentration in both the crops was recorded from soil No. 15 from Bhan-mazara and the smallest in soil No. 10 (Jainpur-4). The highly significant positive correlation (r = 0.841, P <0.001) between Se concentrations in maize and raya indicated that the amount of Se extracted by the 2 crops from different soils varied in the same proportion, but the crops differed in their ability to absorb Se from seleniferous soils. Raya crop absorbed 10 times more Se than that absorbed by maize, especially from soils containing high total Se concentration. Larger differences in Se concentration of the 2 crops may be attributed to the 2 factors: (i) raya, being an S accumulator crop, absorbed greater amounts of Se than did maize; (ii) low concentrations of Se in maize can be partly attributed to the dilution effect due to greater dry matter yield of maize (2.5-3.0 times) than raya. Selenate (Se[O.sup.2-.sub.4]) is preferentially absorbed by plants and may utilise the same pathways as for S[O.sup.2-.sub.4] uptake (Gissel-Nielsen 1973; Banuelos and Meek 1989). As Se[O.sup.2-.sub.4] and S[O.sup.2-.sub.4] are chemical analogues, plants cannot adequately discriminate between these anions (Leggett and Epstein 1956). Thus, Brassica species which have a known ability to accumulate S (Rosenfeld and Beath 1964) will be more apt to take up available Se.
Considering 5 [micro]g Se/g dry matter as the maximum permissible level for animal consumption, maize and raya plants absorbed Se in toxic amounts in 4 and 9 soils, respectively (Table 3). For the same dry matter yield of raya ([approximately equal to] 5.3 g/pot), extremely variable Se concentrations in raya, i.e. 2.7, 13.4, 34.0, and 86.6 [micro]g/g, have been recorded. Thus, the significant negative relationship (r = -0.672, P <0.01) between dry matter yield and Se concentration in raya appears to be more due to wide variation in yields obtained in different soils than to decrease in yield due to high Se concentration in plants. Dhillon and Dhillon (1991) reported that Se concentration in Brassica sp. (at grain formation stage) from seleniferous soils of Punjab varied from 80.5 to 159.7 [micro]g/g, whereas in maize shoots it varied from 0.2 to 9.3 [micro]g/g. Selenium concentration varied from 40.3 to 80.1 [micro]g/g in forage samples collected from some toxic sites in sub-Himalayan areas of West Bengal (Ghosh et al. 1993). In some seleniferous soils of China containing 4.06 [+ or -] 1.24 [micro]g Se/g, maize absorbed 6.47 [+ or -] 4.29 [micro]g Se/g (Zhu and Zheng 2001).
Among the various extractants, hot water soluble Se was significantly correlated with Se concentration in raya (r = 0.705, P <0.01) as well as maize (r = 0.698, P <0.01) (Fig. 1). Selenium concentration in maize was also significantly correlated with 0.25 M KCl extractable Se (r = 0.646, P <0.01) and total Se concentration (r = 0.628, P <0.05) of the soils. Cary and Allaway (1969) showed that plant uptake of Se was closely correlated with the water-soluble Se fraction in soils rich in Se, although such a correlation has not been demonstrated for soils low in Se. Kabata-Pendias and Pendias (1984), however, reported that total soil Se gives a better measure of plant response than does its soluble fractions.
[FIGURE 1 OMITTED]
Among different soil characteristics, only CaC[O.sub.3] content of soils was significantly correlated with Se concentration in maize (r = 0.523, P <0.05). Significant positive coefficients of correlation between CaC[O.sub.3] and available Se concentration of soils (r = 0.43, P <0.001) as well as that of plants (r = 0.37, P <0.001) in the seleniferous region of Punjab (Dhillon et al. 1992) indicated that Se adsorbed on CaC[O.sub.3] particles is easily accessible to plants for absorption. Adriano (1986) has reported that Se tends to concentrate in carbonaceous debris in sandstone. Hamdy and Gissel-Nielsen (1976) reported that addition of CaC[O.sub.3] increased readily available Se in mineral soils at the expense of potentially available Se.
Sulfur concentration in raya varied from 0.63 to 1.28%; in maize it varied from 0.27 to 0.48%. Significant positive relationship was observed between S and Se concentrations in raya (r = 0.773, P <0.001). Although several workers (Mikkelsen et al. 1988; Wu and Huang 1992; Dhillon and Dhillon 2000) have reported a negative interaction between Se and S, a decrease in Se concentration in plant tissue by S application may be the result of dilution of plant biomass due to increased growth rather than direct competition between sulfate and selenate or selenite ion. Carter et al. (1969) have shown that uptake of Se by alfalfa from BaSe[O.sub.4] was enhanced with the application of S as BaS[O.sub.4] in an alkaline silt loam soil, particularly when the S : Se ratio approached 10. A similar synergism between Se[O.sup.2-.sub.4] and S[O.sup.2-.sub.4] was also reported by Smith and Watkinson (1984), who found that increasing Se concentration in soil solution increased the S tissue concentration of rye grass (Lolium perenne L.) and white clover (Trifolium repens L.). Mikkelsen and Wan (1990) found that synergistic interaction between Se[O.sup.2-.sub.4] and S[O.sup.2-.sub.4] occurred in a variety of plant species at low concentrations of substrate S[O.sup.2-.sub.4] ion. In the present investigation, no meaningful relationship has been observed between Se and P concentrations of raya and maize. Interaction between P and Se has been reported to be both antagonistic (Wu et al. 1988) and synergistic (Carter et al. 1972; Levesque 1974).
Se availability under wheat and rice
When grown in seleniferous soils, dry matter yield of wheat varied from 3.0 to 4.7 g/pot and that of rice from 13.6 to 17.4 g/pot (Table 4). Large variations in Se concentration in shoots (0.7-58.3 [micro] g/g in wheat and 1.3-4.6 [micro]g/g in rice) suggested that soils varied greatly in making Se available to crop plants. Wheat crop absorbed about 13 times more Se than rice, especially from the soils having higher Se concentration. Conspicuously lower concentrations of Se in rice than in wheat may be partly due to low availability of Se under reduced conditions (Elrashidi et al. 1987) and partly due to the dilution effect because of greater yields of rice than wheat. Under waterlogged conditions, decreasing soil pH and/or lower redox potentials favour the formation of selenite, with a concomitant decrease in soil solution concentration and mobility of Se (Parker and Page 1994). Dungan and Frankenberger (1999) demonstrated that selenate and selnite ions undergo dissimilatory microbial reduction to produce elemental Se in soil. The greatest Se concentrations in wheat and rice were recorded in soils 11 (Barwa-l) and 13 (Barwa-3) and lowest in soils 6 (Simbly-4) and 10 (Jainpur-4), respectively. In 8 of the experimental soils, wheat absorbed more Se than the maximum permissible level of 5 mg Se/kg. But from none of the soils did rice absorb Se in levels toxic for animal or human consumption. Selenium concentrations in wheat were significantly correlated with those of maize (r = 0.782, P <0.001) and raya (r = 0.959, P <0.001). Lack of such relationship in the case of rice showed that it did not absorb Se from different soils in proportions similar to wheat, maize, or raya.
Among the extractants, hot water soluble Se exhibited a significantly positive relationship with Se concentration in wheat (r = 0.693, P <0.01) as well as rice (r = 0.559, P <0.05) (Fig. 1). Soltanpour and Workman (1980) reported a high degree of correlation between Se concentrations in alfalfa grown on potted soils with AB-DTPA extractable Se ([R.sup.2] = 0.99). These authors suggested 100 [micro]g/kg of AB-DTPA extractable Se as a critical level for feed toxicity. But in the present investigation, although none of the soils contained >81 [micro]g/kg of AB-DTPA extractable Se, a large number of soil samples produced raya, wheat, and maize plants with toxic levels of Se.
Concentrations of S and P in wheat shoots varied from 0.48 to 1.11 and 0.21 to 0.41%, respectively. A highly significant positive relationship was observed between S and Se concentrations in wheat (r = 0.879, P <0.001). Appreciable variations in the concentrations of both the nutrients were also recorded in rice shoots. Unlike wheat, Se concentration in rice was not significantly correlated with S or P concentrations in rice plants.
Hot water soluble Se should serve as a reliable index of bioavailable Se in alkaline seleniferous soils. Plant species varied significantly in their efficiency to absorb Se from seleniferous soils, as wheat and raya crops absorbed about 10-13 times more Se than rice and maize. Rice did not accumulate Se more than the safe levels in any of the soils. While Se levels in maize grown in about 70% of soils were well within permissible safe limits, raya and wheat could accumulate Se in toxic levels in the majority of the soils.
K.S. Dhillon(A,B), (A) Department of Soils, Punjab Agricultural University, Ludhiana--141 004, India. (B) Corresponding author. Email: firstname.lastname@example.org
Neeraj Rani (A) S.K. Dhillon (A) (A) Department of Soils, Punjab Agricultural University, Ludhiana--141 004, India.
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Manuscript received 7 November 2004, accepted 28 April 2005
Table 1. Physico-chemical characteristics of seleniferous soils Soil Location pH (A) EC (A) OC (B) no. (dS/m) (%) 1 Nazarpur-1 7.67 0.21 0.63 2 Nazarpur-2 7.94 0.23 0.75 3 Simbly-1 7.94 0.34 0.63 4 Simbly-2 7.95 0.31 0.78 5 Simbly-3 8.04 0.35 0.67 6 Simbly-4 7.82 0.22 0.78 7 Jainpur-1 7.92 0.66 0.62 8 Jainpur-2 8.06 0.54 0.82 9 Jainpur-3 8.15 0.28 0.49 10 Jainpur-4 7.96 0.23 0.63 11 Barwa-1 8.03 0.36 0.82 12 Barwa-2 8.18 0.30 0.93 13 Barwa-3 8.22 0.26 0.78 14 Mehindpur 7.88 0.60 0.97 15 Bhan-mazara 8.05 0.44 0.64 Soil Location CaC[O.sub.3] (C) Avail. P (D) Avail. S (E) no. (%) ([micro]g/g) ([micro]g/g) 1 Nazarpur-1 0.22 5.70 25.75 2 Nazarpur-2 0.22 13.30 10.12 3 Simbly-1 1.21 12.80 28.37 4 Simbly-2 0.78 19.60 7.50 5 Simbly-3 0.53 9.65 5.00 6 Simbly-4 0.06 13.30 34.50 7 Jainpur-1 0.71 17.10 33.75 8 Jainpur-2 1.97 12.35 5.00 9 Jainpur-3 3.37 13.30 7.50 10 Jainpur-4 1.18 30.45 7.50 11 Barwa-1 2.78 26.45 12.62 12 Barwa-2 2.25 14.25 7.50 13 Barwa-3 0.50 11.45 12.62 14 Mehindpur 1.88 68.45 55.50 15 Bhan-mazara 1.43 22.70 15.25 Soil Location Silt (F) Clay (F) Total Se (G) no. (%) (%) ([micro]g/g) 1 Nazarpur-1 33.5 35.2 2.08 2 Nazarpur-2 30.1 34.7 1.66 3 Simbly-1 52.1 31.3 2.28 4 Simbly-2 53.4 22.5 2.32 5 Simbly-3 57.0 18.7 2.92 6 Simbly-4 30.5 24.0 0.60 7 Jainpur-1 44.1 12.8 2.45 8 Jainpur-2 22.4 25.1 2.08 9 Jainpur-3 34.6 29.2 2.94 10 Jainpur-4 58.2 16.3 1.53 11 Barwa-1 30.4 23.5 3.06 12 Barwa-2 38.1 29.7 2.05 13 Barwa-3 34.6 25.3 2.41 14 Mehindpur 30.5 20.5 2.76 15 Bhan-mazara 34.7 24.1 2.40 (A) pH and electrical conductivity 1 : 2 soil: water ratio. (B) Organic carbon (Walkley and Black 1934). (C) Calcium carbonate (Puri 1930). (D) Olsen et al. (1954). (E) Chesnin and Yien (1950). (F) Day (1965). (G) Levesque and Vendette (1971). Table 2. Amount of selenium extracted ([micro] g/kg) by different extractants from seleniferous soils 0.5 M Soil no. Location AB-DTPA [Na.sub.2] C[O.sub.3] 1 Nazarpur-1 40.13 38.17 2 Nazarpur-2 30.37 18.77 3 Simbly-i 63.31 25.79 4 Simbly-2 52.07 37.24 5 Simbly-3 19.83 35.29 6 Simbly-4 15.64 11.59 7 Jainpur-1 46.20 39.12 8 Jainpur-2 27.83 27.69 9 Jainpur-3 81.37 27.36 10 Jainpur-4 25.42 47.32 11 Barwa-1 25.53 37.82 12 Barwa-2 22.96 31.07 13 Barwa-3 50.05 51.98 14 Mehindpur 60.63 31.46 15 Bhan-mazara 35.48 25.79 Mean [+ or ] s.d 39.79 [+ or -] 18.78 32.43 [+ or -] 10.36 0.1 M Soil no. Location Hot water K[H.sub.2] P[O.sub.4] 1 Nazarpur-1 21.84 119.38 2 Nazarpur-2 22.25 74.91 3 Simbly-i 35.65 143.46 4 Simbly-2 38.24 114.65 5 Simbly-3 54.42 135.99 6 Simbly-4 21.49 32.41 7 Jainpur-1 47.26 142.50 8 Jainpur-2 33.81 104.82 9 Jainpur-3 39.70 148.06 10 Jainpur-4 17.72 162.58 11 Barwa-1 55.22 143.40 12 Barwa-2 47.90 115.55 13 Barwa-3 47.61 134.74 14 Mehindpur 49.97 113.46 15 Bhan-mazara 68.62 168.74 Mean [+ or ] s.d 40.11 [+ or -] 14.82 123.64 [+ or -] 34.72 Isotopically Soil no. Location 0.25 M KCl exchangeable 1 Nazarpur-1 37.05 980 2 Nazarpur-2 29.43 559 3 Simbly-i 54.71 600 4 Simbly-2 57.01 622 5 Simbly-3 82.47 656 6 Simbly-4 26.53 183 7 Jainpur-1 62.75 659 8 Jainpur-2 73.89 558 9 Jainpur-3 81.51 917 10 Jainpur-4 13.56 318 11 Barwa-1 58.77 711 12 Barwa-2 40.39 518 13 Barwa-3 55.72 589 14 Mehindpur 45.83 495 15 Bhan-mazara 79.43 480 Mean [+ or ] s.d 53.27 [+ or -] 21.12 590 [+ or -] 189 Table 3. Dry matter (DM) yield (g/pot) and Se concentration ([micro]g/g) in raya and maize grown in seleniferous soils Raya Maize Soil no. Location DM yield Se cone. DM yield Se cone. 1 Nazarpur-1 6.28 3.25 14.17 2.24 2 Nazarpur-2 5.34 2.72 15.16 2.80 3 Simbly-1 6.17 15.23 17.05 4.91 4 Simbly-2 5.61 12.75 15.65 5.60 5 Simbly-3 6.51 12.33 19.45 4.42 6 Simbly-4 9.94 1.78 16.51 1.70 7 Jainpur-1 6.99 3.62 16.21 2.25 8 Jainpur-2 6.63 6.50 14.17 2.98 9 Jainpur-3 5.28 13.45 13.59 6.40 10 Jainpur-4 5.96 1.48 13.69 1.55 11 Barwa-1 4.39 75.27 14.11 8.12 12 Barwa-2 5.33 34.02 19.84 3.48 13 Barwa-3 5.43 9.62 17.57 2.92 14 Mehindpur 7.80 4.43 16.21 3.82 15 Bhan-mazara 5.28 86.65 15.41 8.63 l.s.d. (P = 0.05) 0.901 3.368 n.s. 0.889 n.s., Not significant. Table 4. Dry matter (DM) yield (g/pot) and Se concentration ([micro]/g)in wheat and rice grown in seleniferous soils Wheat Rice Soil no. Location DM yield Se cone. DM yield Se cone. 1 Nazarpur-1 3.17 1.42 15.81 2.27 2 Nazarpur-2 3.64 0.86 16.53 2.00 3 Simbly-1 4.15 11.00 17.06 3.56 4 Simbly-2 4.31 9.71 13.64 2.25 5 Simbly-3 4.30 12.83 16.48 2.22 6 Simbly-4 4.35 0.74 17.38 1.50 7 Jainpur-1 4.52 1.43 17.43 2.28 8 Jainpur-2 4.02 4.43 15.16 1.75 9 Jainpur-3 3.94 11.19 14.27 2.46 10 Jainpur-4 3.00 0.79 17.43 1.26 11 Barwa-1 4.32 58.35 14.83 3.01 12 Barwa-2 4.65 41.97 17.31 3.40 13 Barwa-3 4.72 8.51 15.75 4.58 14 Mehindpur 4.39 2.12 17.29 2.51 15 Bhan-mazara 4.26 52.82 16.40 2.83 l.s.d. (P = 0.05) 0.607 4.712 n.s. 0.731 n.s., Not significant.
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|Author:||Dhillon, K.S.; Rani, Neeraj; Dhillon, S.K.|
|Publication:||Australian Journal of Soil Research|
|Date:||Sep 1, 2005|
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