Plant and Soil 256: 103–114, 2003. © 2003 Kluwer Academic Publishers. Printed in the Netherlands.
103
Soil properties and turf growth on a sandy soil amended with fly ash S.M. Pathan1 , L. A. G. Aylmore2 & T. D. Colmer1,3 1 School
of Plant Biology and 2 School of Earth and Geographical Sciences, Faculty of Natural and Agricultural Sciences, The University of Western Australia, 35 Stirling Highway, Crawley 6009, Western Australia, Australia. 3 Corresponding author∗ Received 26 November 2002. Accepted in revised form 3 April 2003
Key words: ammonium, Cynodon dactylon, nitrate, phosphorus, soil water, trace elements
Abstract Field lysimeters of a sandy soil were amended to a depth of 100 mm with four rates (0, 5, 10 and 20%, wt/wt) of fly ash, and effects on soil water content, nutrient leaching, turf growth and nutrition, and uptake of trace elements by turf were assessed. Measurements were taken for 70 days for lysimeters either planted with rhizomes of Cynodon dactylon (L.) Pers., cv. ‘Wintergreen’, or left bare. When irrigated daily, soil water content increased progressively with increasing rates of fly ash and leachate volumes were decreased by 17–52% for lysimeters containing fly ash amended soil. Fertiliser was applied equivalent to 28.4 g N m−2 and 10.3 g P m−2 for the entire 70 days (including pre-plant application). Macronutrient concentrations in leaf tissue were within levels regarded as sufficient. Total dry mass (root plus shoot) decreased when fertiliser application rates were reduced by 25%, irrespective of fly ash treatment. In ‘bare’ lysimeters containing fly ash amended soil, cumulative leaching of NO3 − , NH4 + and P were 0.32–0.88 of the values in non-amended soil. When planted with turf, leaching of those nutrients was minimal (equivalent to 3% of total N applied) and leaching loses did not differ among fly ash rates. Extractable soil P levels were increased 2.5–4.5-fold in the fly ash amended zone, compared with non-amended soil. Root mass in the top 100 mm was 1.2–1.5-fold larger for turf in fly ash amended soil, compared to non-amended soil. The Se concentrations were higher in leaf tissue grown in fly ash amended soil (being at most 0.63 µg g−1 ), but there was no effect of fly ash amended soil on As, Ba, B, Cd, Co, Cr, Cu, Pb, Hg, Mn, Ni, Ag or Zn in leaf tissues. Thus, fly ash amendment may be a suitable management option for turf culture on sandy soils, since fly ash improved soil water holding capacity and root growth in the amended zone.
Introduction Sandy soils pose a particular challenge for water and nutrient management due to the relatively low water holding and nutrient retention capacities of these substrates. The high hydraulic conductivity in sandy soils can also contribute to large amounts of water passing beyond the rooting zone of plants. Strategies are required for improvement of water and nutrient management in plant systems, including turf culture, on sandy soils. Fly ash, the fine residue captured from flue exhausts when coal is burnt in power stations, may be ∗ FAX No: 61 8 9380 1108.
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used as an amendment to enhance water and nutrient retention in sandy soils (Pathan et al., 2002, 2003). Fly ash comprises primarily fine sand- and silt-sized particles. If applied at sufficient rates to sandy soils, the fly ash can be used to change soil texture and increase water holding capacity (Aitken et al., 1984; Campbell et al., 1983; Chang et al., 1977; Pathan et al., 2003; Salter et al., 1971). In addition, fly ash can improve the nutritional status of soils via increases in cation exchange capacity (CEC) and by provision of essential nutrients (Carlson and Adriano, 1993; Roberts, 1966; Summers et al., 1998). Moreover, sorption of NO3 − , NH4 + and P on fly ashes can be higher than in sandy soils (Pathan et al., 2002). Thus, improved growth of several crops, turf grass, and pasture
104 species on fly ash amended soils have been reported (Hill and Lamp, 1980; Pathan et al., 2001; Rees and Sidrak, 1956; Roberts, 1966; Summers et al., 1998). However, some types of fly ash contain trace elements (e.g., B, Cd, Se) that, if present at high concentrations, may have adverse effects on crops and the environment (Carlson and Adriano, 1993; El-Mogazi et al., 1988). Trace element concentrations and adverse effects vary among fly ash sources (Adriano et al., 1980; Aitken and Bell, 1985; Bilski et al., 1995; Korcak, 1995; Page et al., 1979). The experiments reported here assessed fly ash from Kwinana Power Station in Western Australia as an amendment to improve water and nutrient management in turf grown on a sandy soil of the Swan Coastal Plain, Western Australia. Experiments using field lysimeters evaluated the impacts of fly ash amendments at four rates on soil water content, nutrient leaching, turf nutritional status, trace element concentrations, and growth during establishment of couch grass (Cynodon dactylon (L.) Pers., cv. ‘Wintergreen’). Materials and methods Soil and fly ash materials Soil (top 200 mm) from the Spearwood dune system of the Swan Coastal Plain in Western Australia (McArthur and Bettenay, 1960) was collected during March 1999 from a site (31◦ 56 S; 115◦ 47 E) cleared of natural vegetation (i.e. Banksia woodlands) in 1996 at Shenton Park, approximately 8 km west of Perth CBD. The soil is known locally as ‘Karrakatta sand’ (Xeropsamments; USDA, 1992). Properties of the soil include: pH in CaCl2 extract = 4.7, total C = 18 mg g−1 , total N = 0.8 mg g−1 , cation exchange capacity (CEC) = 2.2 cmol kg−1 , extractable P = 2.5 µg g−1 , P retention index (PRI; Allen and Jeffery, 1990) = 2.1, coarse sand = 92%, fine sand = 2%, silt = 2% and clay = 4% (for more details see Pathan et al., 2003). After collection, samples were air-dried for 5 days, passed through a 2.0 mm sieve, and stored at room temperature before use. Fly ash derived from a sub-bituminous black coal was collected from Kwinana Power Station in Western Australia. The fly ash was taken from an approximately 3 year old stockpile that had been collected from the electrostatic precipitators and pumped as a slurry to an old limestone quarry where the water drains/evaporates, leaving the solid particles. Properties of this ‘weathered’ fly ash include: pH in CaCl2
extract = 5.6, total C = 30 mg g−1 , total N = 30 mg g−1 , CEC = 6.1 cmol kg−1 , extractable P = 92.5 µg g−1 , PRI = 4.1, coarse sand = 15%, fine sand = 29%, silt = 49% and clay = 7% (for additional information, see Pathan et al., 2003). Fly ash was collected during March, 1999. After collection, the fly ash was dried at 60 ◦ C, thoroughly mixed and stored in plastic-lined containers at room temperature. Experimental approach Two experiments, using lysimeters installed into field plots, were conducted. Experiment 1 evaluated the effect of fly ash incorporation rate on selected soil, leachate, and turf parameters. Three replications of a factorial design comprised four rates of fly ash (0, 5, 10, or 20%; wt/wt fly ash in the surface 100 mm) and two turf treatments (with or without turf). Twelve lysimeters were planted with rhizomes of couch grass (Cynodon dactylon (L.) Pers., cv. ‘Wintergreen’), and 12 lysimeters were kept without turf (i.e. bare). Rhizomes were planted after applying fly ash treatments. The fertiliser regime (based on current industry practice for establishment of turf in Western Australia) consisted of a pre-plant application of pelletised poultry manure at 210 g m−2 (Organic 2000, Carrabooda, Western Australia; N = 40 mg g−1 , P = 13 mg g−1 ) and superphosphate with micronutrients at 20 g m−2 (Wesfarmers CSBP Limited, Kwinana, Western Australia; P = 90 mg g−1 ). Thereafter, ‘Horticulture Special’ (Wesfarmers CSBP Limited, Kwinana, Western Australia; N = 122, P = 35, K = 102, Ca = 40, Mg = 4 and S = 120; all mg g−1 ) was applied at 32.8 g m−2 (equivalent to 4.0 g N m−2 ) on 5 selected dates (15/12/99, 29/12/99, 12/01/00, 26/01/00 and 09/02/00) during the 70 day experiment. Experiment 2 was designed to evaluate the effect of four fertiliser application rates (0, 50, 75 or 100% of amounts used in Experiment 1; including the pre-plant application) on growth and nutrient status in turf in lysimeters containing non-amended or 10% (wt/wt) fly ash amended soil (top 100 mm). Twenty-four lysimeters were planted with rhizomes of couch grass (Cynodon dactylon (L.) Pers., cv. ‘Wintergreen’) and supplied with one of the four fertiliser rates. The lysimeters (non-amended and 10% wt/wt fly ash amended) that received the 100% fertiliser rate in Experiment 2 were also those used in Experiment 1. Fertiliser was applied on 5 selected dates (same dates as given for Experiment 1) during the 70 day experiment.
105 For both experiments, lysimeters were PVC columns of 150 mm inner diameter and 600 mm internal length, with a 100 mm hollow base to house a collection bucket. Soil was packed into each column at a bulk density (1.5 Mg m−3 ) as measured for the soil at the collection site in the field. Fly ash was incorporated at four rates into the top 100 mm of soil in each lysimeter. Each lysimeter was inserted into a 155 mm inner diameter and 700 mm deep metal sleeve, previously dug into field plots. The surface of each lysimeter was flush with that in the plots, to avoid edge effects. Access holes (40 mm diameter) were located at 5 depths (100, 200, 300, 400 and 500 mm) and holes were sealed using waterproof tape. The base of the column contained a 52-µm polyester filter and a small wad of glass wool, funneled into a central exit point from which leachates were collected in a 250 mL plastic container located under each lysimeter. In both experiments, lysimeters were planted on 8 December 1999 and installed into field plots with the same rate of fly ash incorporation and planted with the same cultivar (planted 14 days earlier), or bare plots. The plots were located at Shenton Park, Western Australia (location given above). The irrigation regime for the first 7 days was 3.5 mm applied three times per day, followed by 5.0 mm twice per day for the next 21 days, and then for the remainder of the experimental period one irrigation was given each morning to replace 100% of the previous days net evaporation, measured using a class A pan adjacent to the plots. These irrigation regimes were as ‘current Western Australian industry practice’ for the establishment of turf during summer months. Selected environmental parameters at the field site during the study period are given in Table 1. During summer in South Western Australia (December – February) rainfall is very low. An ‘unusual’ rainfall event (58.8 mm) on 22 January 2000 caused rainfall recorded for January 2000 (Table 1) to be higher than long-term averages. Measurements taken for field lysimeters The changes in soil water storage (volumetric soil water content) in lysimeters were measured at selected times using a hand-held Theta Probe (Delta-T Devices, ML1, Cambridge, England) inserted via the access holes at different depths (100, 200, 300, 400 and 500 mm) and into the surface 50 mm. The probe was calibrated immediately prior to use and access holes were resealed using waterproof tape after each measurement.
Leachates collected in a plastic container under each lysimeter were sampled four times per week. An ‘unusual’ rainfall event (58.8 mm) occurred on 22 January 2000 (Table 1), and the rain was excluded from lysimeters by covering each with a PVC disk. The volumes of leachates from each lysimeter were measured, samples combined, and stored at 4 ◦ C to give a weekly total for each lysimeter. Sub-samples of the combined volume were filtered (0.45 µm) and stored frozen until analyses for NO3 − , NH4 + and P. Some samples were lyophilised in order to concentrate ions 10–20-fold (FD4 Freeze Dryer, Heto, DK 3450, Allered, Denmark) to detectable levels. Nitratewas measured using the hydrazinium reduction method (Kamphake et al., 1967) and NH4 + using a modified berthelot indophenol reaction (Searle, 1984; Selmer-Olsen, 1971); both were linked to a segmented flow auto analyser (Skalar, SAN Plus System, Breda, the Netherlands). Phosphate was measured using the malachite green oxalate method (Motomizu et al., 1983) and a spectrophotometer (Shimadzu, UV 1601, Kyoto, Japan). Recoveries of spikes of NO3 − , NH4 + and P added to leachate collection containers placed under spare lysimeters in the field were 94–107% (includes samples that were lyophilised). Cumulative leaching of NO3 − , NH4 + and P were calculated from the concentrations and volumes of leachates. Seventy days after planting the rhizomes, lysimeters were harvested. Soil samples at different depths (0–100, 100–200, 200–300, 300–400 and 400–500 mm) were taken, and NO3 − and NH4 + were measured by extracting 10.0 g air-dried samples with 100 mL of 2000 mol m−3 KCl at room temperature for 1 h. Extracts were centrifuged and filtered before analysing for NO3 − and NH4 + as described above. Extractable P in 1.0 g air-dried samples of soil shaken in 100 mL of 500 mol m−3 NaHCO3 at room temperature for 16 h (Olsen et al., 1954; as modified by Colwell, 1965; Rayment and Higginson, 1992) was quantified using a colorimetric method (Murphy and Riley, 1962) and a spectrophotometer (Shimadzu, UV 1601, Kyoto, Japan). At harvest, shoots were snipped off the lysimeters, and rhizomes and roots were washed from the soil. Samples were placed in paper bags, dried in a forcedair oven at 70 ◦ C for 72 h, and weighed. Leaf tissues were ground using a stainless-steel ball mill. Total N was determined using a CN analyser (LECO, CHN 1000, MI, USA). Total P, K, Ca, Mg and S were measured using X-ray florescence spectrometry (XRFS) (Philips, PW 1400, Eindhoven, the Netherlands). Total
106 Table 1. Selected environmental parameters during the period the experiments were conducted at Shenton Park, Western Australia. Average daily net evaporation and monthly rainfall data were measured adjacent to the plots and all other parameters were from an Automatic Weather Station located 500 m from the plots Month
Average daily temperaturea min
Average daily relative humiditya min max %
max ◦C
December 1999 January 2000 February 2000
17.9 (2.8) 18.5 (2.4) 18.3 (2.5)
30.2 (5.2) 29.2 (4.8) 30.1 (3.8)
32.2 (13.8) 39.8 (15.3) 35.7 (11.5)
76.6 (17.1) 81.2 (15.8) 75.6 (11.4)
Average daily net evaporationa
Total monthly rainfall mm
10.2 (2.6) 8.9 (3.4) 10.2 (2.1)
6.0 108.6 0.2
a Values given are means with standard deviation in brackets.
As, Ba, B, Cd, Co, Cr, Cu, Pb, Hg, Mn, Ni, Se, Ag and Zn were measured after digesting leaf tissues in nitric/perchloric acid. Inductively coupled plasmamass spectrometry (ICP-MS) (Pescien, Elan 6000, Ontario, Canada) was used to measure concentrations of elements in digests. Recoveries of spikes of trace elements added to the digests were 93–109%, and results were validated against plant tissue standards analysed using the same procedures.
Data analyses Treatment differences were evaluated through analysis of variance (ANOVA) and as least significant difference (l.s.d) among means. The error bars on the graphs at each data point represent the standard error of the mean (not visible when smaller than the size of the symbols).
Results Experiment 1: soil water content, nutrient leaching, turf nutrition and growth Soil water content The volumetric soil water content was measured in situ, 24 h after irrigation (i.e. before daily irrigation), on 6 days (data for one of these days are shown in Figure 1). In the amended soil zone (top 100 mm) of lysimeters without (Figure 1a) or with turf (Figure 1b), water contents were 1.6–3.2-fold higher (P < 0.001) when compared to values in lysimeters with non-amended soil. For example in lysimeters with turf, volumetric soil water content in the top 100 mm was 6.7% in control lysimeters and 17.3% in lysimeters amended with 10% (wt/wt) fly ash (Figure 1b). Similar
Figure 1. Soil water content at different depths in field lysimeters without turf (a) or with turf (b) for a sandy soil amended (top 100 mm) with various amounts of fly ash. Lysimeters were watered daily at 100% replacement of net evaporation and measurements were taken using a Theta Probe, 24 h after irrigation (i.e. before daily irrigation). The l.s.d for measurements in the top 50 and 100 mm were: in (a) 2.27 and 3.62, respectively, and in (b) 4.08 and 1.58. Symbols: ....◦....Control; —— 5% (wt/wt) fly ash; —— 10% (wt/wt) fly ash; —•— 20% (wt/wt) fly ash.
fly ash effects on soil water holding capacity, with or without turf, were observed in measurements taken on the 5 other selected days (data not shown). Leachate volumes and nutrient contents For ‘bare’ lysimeters, the cumulative volumes of leachates from fly ash amended soil were 0.48–80
107
Figure 2. Cumulative volume of leachates on a weekly basis (L m−2 ) from lysimeters containing a sandy soil with the top 100 mm amended with various amounts of fly ash. Lysimeters were either left bare or planted with rhizomes of Cynodon dactylon (L.) Pers. The l.s.d of cumulative leaching for (a) without turf and (b) with turf were 29 and 37, respectively. Symbols: ....◦.... Control; —— 5% (wt/wt) fly ash; —— 10% (wt/wt) fly ash; —•— 20% (wt/wt) fly ash.
(P < 0.001) of the volumes from non-amended soil (Figure 2a). During the 70 day study, 20–34% of the applied water drained from the ‘bare’ lysimeters containing fly ash amended soil, while 42% drained from lysimeters with non-amended soil. When planted with turf the cumulative volumes of leachates from lysimeters containing fly ash amended soil were 0.75– 0.83 (P < 0.01) of the volume from lysimeters with non-amended soil (Figure 2b). During the 70 days, 32–36% of the applied water drained from lysimeters planted with turf and containing fly ash amended soil, while 43% drained from lysimeters with turf and containing non-amended soil. Though N was applied as NO3 − and NH4 + , NH4 + in the soil is usually converted into NO3 − within a few days (McLaren and Cameron, 1996). Therefore, while the absolute amounts of leaching losses of NO3 − and NH4 + are presented (Figure 3), the data are also discussed as amounts of the total N applied rather than total NO3 − or NH4 + applied. The cumulative amounts of NO3 − leached from the ‘bare’ lysimeters containing fly ash amended soil were 0.70–0.88 (P < 0.05) of the amounts from the
Figure 3. Cumulative leaching of (a) NO3 − , (b) NH4 + and (c) P, from lysimeters containing a sandy soil with the top 100 mm amended with various rates of fly ash. Leachates were collected 4 times a week, weekly totals were measured, and the total cumulative amounts after 70 days are shown. During the period total applications of N and P (including pre-plant application) were 28.4 and 10.3 g m−2 , respectively. Extractable P added due to fly ash incorporation was 0, 0.7, 1.4, and 2.8 g m−2 for 0, 5, 10 and 20% wt/wt fly ash in the top 100 mm. The l.s.d of cumulative leaching for NO3 − , NH4 + and P from lysimeters with turf were: n.s, n.s and 0.02, respectively; for lysimeters without turf were: 1.39, 0.03 and 0.03, respectively. (Note: n.s = not significant at the 0.05 probability level). Symbols: closed columns with turf and open columns without turf.
lysimeters with non-amended soil (Figure 3a). After 70 days, the cumulative NO3 − leached from ‘bare’ lysimeters without fly ash was equivalent to 29% (i.e. 8.2 g m−2 ) of the total N applied, whereas 25, 22 and 20% (i.e. 7.1, 6.3 and 5.7 g m−2 ) were leached from ‘bare’ lysimeters containing 5, 10 and 20% (wt/wt) fly ash amended soil, respectively. However, cumulative NO3 − leached from lysimeters planted with turf were 0.11–0.15 of the values leached from the ‘bare’ lysimeters (Figure 3a). Under turf, less than 3% of the total applied N was leached as NO3 − . When planted with turf, fly ash amendment had no significant effect on NO3 − leaching.
108 The cumulative amounts of NH4 + leached from the ‘bare’ lysimeters containing fly ash amended soil were 0.33–0.78 (P < 0.001) of the amounts from lysimeters containing non-amended soil (Figure 3b). After 70 days, the cumulative NH4 + leached from bare lysimeters without fly ash was equivalent to 1.12% (i.e. 0.32 g m−2 ) of the total N applied, whereas 0.84, 0.47 and 0.36% (i.e. 0.24, 0.13 and 0.10 g m−2 ) were leached from the lysimeters containing 5, 10 and 20% (wt/wt) fly ash amended soil, respectively. However, cumulative leaching of NH4 + from lysimeters planted with turf was 0.22–0.45 of that in the ‘bare’ lysimeters (Figure 3b). Less than 0.24% of applied N was leached as NH4 + from all treatments when planted with turf. Moreover, when planted with turf, fly ash amendment had no significant effect on NH4 + leaching. The amounts of P leached from lysimeters containing soil, with or without fly ash amendment (0, 5, 10 and 20%; wt/wt) in the top 100 mm, are shown in Figure 3c. In ‘bare’ lysimeters containing fly ash amended soil, the cumulative amounts of P leached were 0.32–0.61 (P < 0.001) of the amounts from lysimeters containing non-amended soil (Figure 3c). After 70 days, the cumulative P leached from ‘bare’ lysimeters without fly ash was equivalent to 3.26% (i.e. 0.34 g m−2 ) of the total P applied, whereas 1.98, 1.67 and 1.07% (i.e. 0.20, 0.17 and 0.11 g m−2 ) were leached from those containing 5, 10 and 20% (wt/wt) fly ash amended soil, respectively (Figure 3c). When planted with turf the cumulative leaching of P was 0.25–0.52 of that in lysimeters without turf, so that under turf (with or without fly ash amended soil) less than 0.74% (i.e. 0.08 g m−2 ) of the total applied P was leached (Figure 3c). Nevertheless, for lysimeters planted with turf the cumulative leaching of P from those containing fly ash amended soil were 0.67–0.84 (P < 0.05) of the amount leached from lysimeters containing non-amended soil (Figure 3c). Extractable soil nutrients The amounts of extractable NO3 − , NH4 + and P in the top 100 mm of soil in lysimeters with or without fly ash amendment (0, 5, 10 and 20%; wt/wt) are shown in Figure 4. Extractable NO3 − levels were not significantly different among samples from the lysimeters containing fly ash amended soil or non-amended soil (Figure 4a). However, extractable NO3 − levels were 6–7-fold higher in samples from lysimeters without turf, when compared to those with turf, irrespective of fly ash amendments (Figure 4a). Extractable NH4 + levels were also not different among samples from
Figure 4. Effect of fly ash on extractable (a) NO3 − , (b) NH4 + and (c) P in the top 100 mm of a sandy soil amended with various rates of fly ash. Samples were taken from lysimeters with or without turf after 70 days of treatments. During the period total applications of N and P (including pre-plant application) were 28.4 and 10.3 g m−2 , respectively. Extractable P added due to fly ash incorporation was 4.6, 9.2 and 18.4 µg g−1 for 0, 5, 10 and 20% wt/wt fly ash in the top 100 mm. The effect of fly ash was not significant in (a) or (b), but was in (c) for which the l.s.d was 13 (without turf) and 19 (with turf). Symbols: closed columns with turf and open columns without turf.
the lysimeters containing fly ash amended soil and non-amended soil (Figure 4b). However, extractable NH4 + was 1.3–1.6-fold higher in samples from lysimeters without turf when compared to those with turf, irrespective of fly ash amendments (Figure 4b). Extractable P was 2.5–4.5-fold higher (P < 0.001) in samples of fly ash amended soil, than in non-amended soil, both for lysimeters with or without turf (Figure 4c). Turf growth, nutrition and trace elements Root growth was 1.2–1.5-fold higher (P < 0.05) in the top 100 mm zone for turf in lysimeters containing fly ash amended soil, when compared to turf grown in lysimeters containing non-amended soil (Figure 5). However, there was no significant effect of fly ash
109 Table 2. Effect of fly ash amendment at increasing rates on concentrations of trace elements in leaf tissue of Cynodon dactylon (L.) Pers. Samples were taken from field lysimeters 70 days after rhizomes were planted Element 0
As Ba B Cd Co Cr Cu Pb Hg Mn Ni Se Ag Zn
0.76 ± 0.09 30.49 ± 2.58 15.31 ± 0.58 0.11 ± 0.02 0.33 ± 0.03 30.22 ± 2.58 12.37 ± 0.13 11.39 ± 1.28 0.01 ± 0.00 89.99 ± 6.04 25.62 ± 5.45 0.03 ± 0.00 20.86 ± 2.45 55.92 ± 5.12
Concentrations in leaf tissuea Fly ash incorporation rate (%, wt/wt) 5 10 µg g−1 0.62 ± 0.01 29.08 ± 0.88 21.31 ± 5.21 0.12 ± 0.01 0.50 ± 0.06 38.16 ± 2.36 11.49 ± 0.67 6.67 ± 0.58 0.01 ± 0.00 84.37 ± 7.89 32.46 ± 7.23 0.13 ± 0.01 21.53 ± 2.71 57.50 ± 1.59
0.48 ± 0.09 25.89 ± 0.43 19.92 ± 1.64 0.15 ± 0.01 0.62 ± 0.07 39.14 ± 6.92 10.69 ± 0.52 8.22 ± 0.80 0.01 ± 0.01 85.82 ± 3.08 42.22 ± 6.38 0.31 ± 0.03 26.16 ± 4.39 59.32 ± 1.91
l.s.d 20 0.57 ± 0.06 27.75 ± 4.84 18.46 ± 3.73 0.15 ± 0.01 0.76 ± 0.15 36.59 ± 1.04 13.82 ± 1.65 9.11 ± 3.18 0.01 ± 0.01 86.75 ± 5.94 37.32 ± 1.21 0.63 ± 0.05 25.51 ± 4.38 70.03 ± 7.03
n.sb n.s n.s n.s n.s n.s n.s n.s n.s n.s n.s 0.11*** n.s n.s
a Data given are means of 3 replicates ± standard errors. b n.s, not significant at the 0.05 probability level. ∗∗∗ Significant at the 0.001 probability level.
on shoot (leaf plus rhizome) growth during the study period. Leaf tissue concentrations of the macronutrients: N, P, K, Ca, Mg and S, were all regarded as sufficient for turf (Jones, 1980; Turner, 1993). The average concentrations of macronutrients in leaf tissues (across all fly ash treatments) were (all mg g−1 ): N = 33.6 ± 0.5, P = 3.4 ± 0.3, K = 18.5 ± 0.8, Ca = 3.6 ± 0.2, Mg = 2.1 ± 0.1 and S = 3.4 ± 0.1. Concentrations of all trace elements, except Se, were not statistically different in leaf tissue from turf grown in lysimeters containing fly ash amended soil, compared with non-amended soil (Table 2). For Se, leaf tissue concentrations were progressively higher for turf grown in lysimeters containing 5, 10 or 20% (wt/wt) fly ash amended soil. Experiment 2: turf growth and nutrition in response to fertiliser application rate The fertiliser response experiment used lysimeters without fly ash amendment, or with one level of amendment, 10% wt/wt. Shoot (leaf plus rhizome) and root growth increased with higher fertiliser application rates in lysimeters with or without fly ash amendment (Table 3). There was no significant effect of fly ash on shoot (leaf plus rhizome) growth.
However, total root dry mass for turf in lysimeters containing 10% (wt/wt) fly ash amended soil was 1.3– 1.4-fold higher when compared to non-amended soil, for paired comparisons at all fertiliser application rates (Table 3). In lysimeters to which no fertiliser was applied, shoot and root growth both responded positively to fly ash amendment (10%, wt/wt); shoot and root dry mass were 1.4- and 1.3-fold higher, respectively, when compared to turf in non-amended soil (Table 3). There were significant effects of fertiliser rate on leaf tissue concentrations of N, P, K and S, for turf in lysimeters with or without fly ash amendment (Table 4). By contrast, there was no significant effect of fertiliser rate on Ca or Mg in leaf tissue. For turf in lysimeters without fertiliser applications, there was no significant effect of fly ash on N, K or Mg in leaf tissue, but the concentration of P was 1.2-fold higher (P < 0.05) in turf grown in fly ash amended soil (Table 4). By contrast, the concentrations of Ca and S were lower (1.4- and 1.3-fold, respectively) in leaf tissue of turf grown in lysimeters containing 10% (wt/wt) fly ash amended soil compared with non-amended soil, when no fertiliser was provided.
110 Table 3. Effect of fertiliser rates on (a) shoot (leaf plus rhizome) and (b) root, dry mass in lysimeters containing non-amended soil and 10% (wt/wt) fly ash amended (top 100 mm) soil. Lysimeters were managed as described in the ‘Materials and methods’ and samples were taken 70 days after rhizomes of Cynodon dactylon (L.) Pers., were planted. Note: 100% industry application rate is equivalent to N at 28.4 g m−2 and P at 10.3 g m−2 for the entire 70 days (including pre-plant application) Dry massa Fertiliser application rates (%, industry practice)
Fly ash incorporation rates (%, wt/wt) 0
(a) Shoot (leaf plus rhizome) dry mass (g m−2 ) 0 231 ± 42 10 324 ± 49 l.s.d n.sb
l.s.d
50
75
100
466 ± 78 625 ± 76 n.s
569 ± 53 689 ± 16 n.s
808 ± 67 1165 ± 97 n.s
203** 257***
3622 ± 240 5075 ± 303 1015∗ ∗
759** 709***
(b) Root dry mass (g m−3 ) 0 10 l.s.d
Root dry massa 2565 ± 328 2962 ± 179 3584 ± 149 3829 ± 150 922∗ 518∗
2056 ± 105 2791 ± 204 576∗
a Data given are means of 3 replicates ± standard errors. b n.s, not significant at the 0.05 probability level.
*Significant at the 0.05 probability level. **Significant at the 0.01 probability level. ***Significant at the 0.001 probability level. Table 4. Effect of fertiliser rates on concentrations of macronutrients in leaf tissue of Cynodon dactylon (L.) Pers., grown in lysimeters containing (a) non-amended soil and (b) 10% (wt/wt) fly ash amended soil. Lysimeters were managed as described in the ‘Materials and methods’ and samples were taken 70 d after rhizomes of Cynodon dactylon (L.) Pers., were planted. Note: 100% industry application rate is equivalent to N at 28.4 g m−2 and P at 10.3 g m−2 for the entire 70 days (including pre-plant application) Nutrient 0
Concentrations in leaf tissuea Fertiliser application rates (% industry practice) 50 75 mg g−1
(a) Turf grown in non-amended soil N 15.0 ± 1.2 P 2.2 ± 0.1 K 14.8 ± 0.6 Ca 4.1 ± 0.1 Mg 1.9 ± 0.1 S 2.8 ± 0.2
l.s. days 100
30.5 ± 0.7 3.5 ± 0.1 19.6 ± 0.6 3.6 ± 0.1 1.8 ± 0.1 3.9 ± 0.1
35.0 ± 1.8 3.7 ± 0.1 21.5 ± 0.7 3.8 ± 0.1 2.0 ± 0.1 4.1 ± 0.2
35.3 ± 1.8 3.2 ± 0.1 20.4 ± 0.8 4.2 ± 0.3 2.2 ± 0.1 4.2 ± 0.2
3.9*** 0.4*** 2.4*** n.sb n.s 0.6**
(b) Turf grown in 10% (wt/wt) fly ash amended soil N 16.0 ± 1.1 25.1 ± 2.1 P 2.7 ± 0.1 3.4 ± 0.1 K 13.9 ± 0.2 18.1 ± 0.2 Ca 2.8 ± 0.1 2.5 ± 0.1 Mg 1.6 ± 0.1 1.6 ± 0.1 S 2.1 ± 0.1 3.2 ± 0.1
29.3 ± 1.6 3.5 ± 0.1 19.2 ± 0.1 2.9 ± 0.2 1.7 ± 0.1 3.6 ± 0.1
33.6 ± 3.5 3.4 ± 0.1 18.7 ± 0.4 3.4 ± 0.2 1.9 ± 0.1 3.1 ± 0.1
7.6*** 1.9*** 0.8*** n.sb n.s 0.3**
a Data given are means of 3 replicates ± standard errors. b n.s, not significant at the 0.05 probability level.
** Significant at the 0.01 probability level. *** Significant at the 0.001 probability level.
111
Figure 5. Effect of rate of fly ash incorporation in the top 100 mm of a sandy soil on (a) shoot and (b) root growth, of turf in field lysimeters. Lysimeters were managed as described in the ‘Materials and methods’ and samples were taken 70 days after rhizomes of Cynodon dactylon (L.) Pers., were planted. The effect of fly ash was significant only for root dry mass in the amended soil zone (i.e. top 100 mm), with l.s.d of 623. Symbols for (b) root dry mass: closed columns amended soil zone (i.e. top 100 mm) and open columns non-amended soil zone (i.e. below 100 mm).
Discussion The potential benefits of applying fly ash to sandy soils include improved soil water holding capacity and decreased drainage (Adriano and Weber, 2001; Campbell et al., 1983; Gangloff et al., 2000; Ghodrati et al., 1995; Pathan et al., 2003). Similarly, incorporation of fly ash with a dominance of silt-sized particles into a sandy soil in the present study increased soil water holding capacity (Figure 1). Larger volumes of the irrigation water were held in the fly ash amended soil, presumably because incorporation of fine-sized particles can increase total porosity (Aitken et al., 1984) and perhaps more importantly shift pore size distribution from primarily large ‘macropores’ to many more ‘micropores’ (Ghodrati et al., 1995). Since fly ash amended soil can hold a greater volume of water and also reduce infiltration rates by 2–8fold (Pathan et al., 2001), a reduction in cumulative drainage from lysimeters containing amended soil was also observed (Figure 2). The cumulative volumes of
leachates from lysimeters containing fly ash amended soil and planted with turf (Figure 2b) were higher than the volumes from lysimeters without turf (Figure 2a), presumably due to preferential flow down macropores formed by the root systems (Devitt and Smith, 2002; Magesan et al., 1999). The proportions of water lost as leachates in the present study (43% of water applied for turf on non-amended soil) were similar in magnitude to that leached (46% of the water applied) from creeping bentgrass when irrigated at 38 mm week−1 in a sandy soil and grown in a controlled (21 ◦ C day, 18 ◦ C night) environment (Mancino and Troll, 1990). The relatively low level of N (NO3 − plus NH4 + ) leached under turf (equivalent to 3% of total N applied) in the present study (Figure 3a,b) indicates that the fertiliser regime used supplied N at a rate and frequency suitable for the demand and uptake capacity of the turf. Under turf, leaching losses as high as 53% of applied N have been observed, but generally are less than 10% (Petrovic, 1990). Thus, N leaching from turf, when managed appropriately, is generally considered not to be a threat to groundwater quality (Geron et al., 1993). Applied NH4 + is rapidly converted into NO3 − in most soils (McLaren and Cameron, 1996). Therefore, N leaching occurs primarily as NO3 − , with NH4 + losses being negligible (Mancino and Troll, 1990). Fly ash amendments retarded NO3 − leaching in the same sandy soil in our earlier laboratory study (Pathan et al., 2002). In the present study, the reduced NO3 − leaching from ‘bare’ lysimeters containing fly ash amended soil may result from slower water through-flow (Figure 1a) and specific adsorption on the fly ash (Pathan et al., 2002). Turf species have extensive root systems and are efficient at taking up NO3 − and NH4 + from the soil (Liu et al., 1997), so that levels of these nutrients in the soil when planted with turf were much lower when compared to soil without turf (Figure 4a, b). Phosphorus leaching under turf is considered to be a potential problem only on some soil types and when high rates of soluble sources and high irrigation are applied (Shuman, 2001). In the present study, only small amounts of P leached under turf (Figure 3c). P leaching was lower from lysimeters containing fly ash amended soil than in lysimeters containing nonamended soil, for those with or without turf (Figure 3c). In our earlier laboratory study, initial P leaching was enhanced in fly ash amended soil because fly ash itself contains 92.5 µg g−1 extractable P (Pathan et al., 2003). In the present study, that scenario was not observed presumably due to the larger columns con-
112 taining a large soil layer (500 mm) beneath the fly ash amended zone, and the soil (Karrakatta sand) itself has a moderate capacity for P retention (McPharlin et al., 1992). The increased extractable P in the top 100 mm of amended soils (Figure 4c) would result from fly ash incorporation (5, 10 and 20% wt/wt) adding 4.6, 9.2 and 18.4 µg g−1 of P to the top 100 mm, together with sorption by the fly ash of P added in fertilisers (Pathan et al., 2002). Considerable work has been carried out on the effects of fly ash on growth and elemental compositions in plants (reviewed by Adriano et al., 1980; Carlson and Adriano, 1993; El-Mogazi et al., 1988). The effects range from significant increases to reductions in growth due to toxic effects of one or more elements. Positive yield responses to several sources of fly ash have been reported for several crops on a variety of soil types (Adriano et al., 1980; Bilski et al., 1995; Hill and Lamp, 1980; Rees and Sidrak, 1956). In an earlier study of Kwinana fly ash, addition of 10 kg m−2 increased dry matter yield of clover-based pasture by an average of 56% on a sandy soil in Western Australia (Summers et al., 1998). In the present study, root growth of turf was enhanced in the soil zone containing Kwinana fly ash, presumably due to improved soil water holding capacity (Figure 1) and supply of additional P (Figure 4c). Root proliferation in nutrientrich patches has been reported previously (Fransen and De Kroon, 2001). The leaf tissue concentrations of macronutrients (N, P, K, Ca, Mg and S) in turf grown under ‘current Western Australia industry fertiliser practices for turf establishment’ (Experiment 1) were well within adequate levels (Jones, 1980; Turner, 1993), and there was no effect of fly ash on the leaf concentrations of these elements. In experiment 2, the fertiliser application rate was progressively reduced. Leaf N and P concentration remained at levels considered as sufficient even when fertiliser was applied at 50% of current practices to non-amended or amended soil; although growth had declined significantly. When no fertiliser was applied turf growth was lower than when supplied with fertiliser; however, leaf tissue P (Table 4) and total dry mass (Table 3) were higher in turf on 10% (wt/wt) fly ash amended soil compared to nonamended soil. The 92.5 µg g−1 extractable P in fly ash was equivalent to 14% (1.4 g P m−2 for the 10% wt/wt fly ash rate) of the P applied in current fertiliser practice for the 70 days. In earlier work, application of P increased growth of turf during establishment,
whereas little response to P was shown for established turf (Christians et al., 1979; Turner, 1993). Some fly ash amendments can affect trace element concentrations in tissues of plants grown on these modified soils (Adriano et al., 1980, 2002; Carlson and Adriano, 1993; El-Mogazi et al., 1988). For the turf grown in the present study, 14 trace elements were analysed and only Se concentrations were significantly higher in leaf tissue of plants grown in fly ash amended soil (Table 2). The values for Se (0.63 µg g−1 at the highest amendment rate) were much smaller than those (4–5 µg g−1 ) regarded as potentially hazardous (CMBEEP, 1976). In earlier studies, other plant species grown on fly ash amended soils also contained higher levels of Se (Adriano et al., 2002; El-Mogazi et al., 1988; Mbagwu, 1983). In contrast, tissue concentrations of some trace elements, including Cd, Cu, Cr, Mg, Mn and Zn, decreased in plants grown in some fly ash amended soils (Adriano et al., 2002; Elseewi et al., 1980; Schnappinger et al., 1975). The present study showed that amendment of coarse-textured sand with fine-textured fly ash significantly improved soil water holding capacity and reduced drainage. Thus, fly ash amendment may have the potential to improve plant growth in sandy soils by increasing the amount of plant available water in the root zone (Campbell et al., 1983; Gangloff et al., 2000). In addition, fly ash increased extractable P in the soil and reduced NO3 − , NH4 + and P leaching in the sandy soil without turf. The sorption of NO3 − , NH4 + and P on some fly ashes can be higher than in some sandy soils (Pathan et al., 2002). The low levels of NO3 − , NH4 + and P leached under turf (equivalent to 3% of total N applied) in the present study indicate that the fertiliser application rate and frequency used was suitable for the demand and uptake capacity of the turf. Thus, when planted with turf there was no significant effect of fly ash on nutrient leaching under current practices in Western Australia. Long-term field trials of established turf (i.e. maintenance rather than establishment phase) with a range of irrigation and fertiliser treatments, would provide additional information on the potential beneficial use of fly ash to enhance nutrient and water use efficiency in turf grown on sandy soils.
Acknowledgements We thank the members of the ‘UWA Turf Industries Research Steering Committee’ for their valuable ad-
113 vice and enthusiastic support during this project, Dr. Louise Barton for helpful comments on draft versions of this manuscript, and Mr. Michael Smirk for instruction on the use of analytical equipment. This project was funded by the Western Power Corporation and Ash Development Association of Australia.
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