Application of Bottom Ash Derived from Livestock Manure Combustion-Improved Soil Physicochemical Properties and Nutrient Uptake of Creeping Bentgrass

Abstract

This experiment examined the effects of blending bottom ash produced after combusting dry livestock manure (BACL, 2–4 mm particle) as a soil amendment on the physicochemical properties of the root zone and growth response of creeping bentgrass in sandy soil. The treatments were designed as follows: control [100% sand], 3% BACL (3% BACL + 97% sand), 5% BACL (5% BACL + 95% sand), 7% BACL (7% BACL + 93% sand), and 10% BACL (10% BACL + 90% sand). Although BACL improved the soil physical properties, such as the capillary porosity, total porosity, and hydraulic conductivity, it reduced the cation exchangeable capacity. The BACL treatments increased the pH, EC, Av-P₂O₅, and Ex-K compared to the control. The turf color index, chlorophyll content, shoot length, clipping yield, and shoot dry weight after the BACL treatments were similar to the control. The growth and nutrient uptake of the roots in the BACL treatment were higher than those of the control. The BACL application amount was positively correlated with the capillary porosity and total porosity of the root zone (p ≤ 0.01) and with the growth and nutrient levels of the roots (p ≤ 0.05). These results suggest that applying BACL as a soil amendment enhanced the uptake of phosphorus and potassium in the roots of creeping bentgrass by improving the soil porosity in the root zone and by supplying phosphate and potassium.

1. Introduction

Improvements in the quality of life have led to increased meat consumption by changing the food culture [1]. The numbers of cows, pigs, and poultry in the South Korea in December 2023 were 4.0 million, 11.1 million, and 18.2 million, respectively. A survey conducted by the Ministry of Agriculture, Food and Rural Affairs reported that 50.9 million tons of livestock manure (LM) was generated in 2023. Of this amount, approximately 84.5% of LM was recycled, with 72.7% composted and 11.8% processed into liquid fertilizer. Meanwhile, about 15.6% of LM was treated and purified in wastewater treatment facilities.

A study evaluating the application of a safe LM compost for crops in the field examined its quality by analyzing chemical properties such as total nitrogen, total carbon, and their ratio [2]. LM compost containing a large amount of phosphate (P₂O₅) was fertilized based on the nitrogen (N) content. Nevertheless, it might supply excessive P₂O₅ [3]. The application of LM compost improved plant root growth by increasing organic matter, cation exchangeable capacity (CEC), and soil porosity [4]. The excessive application of LM compost increased the available P₂O₅ content [5]. The soil erosion of a high content of available P₂O₅ might deteriorate the water quality of rivers adjacent to crop fields and rice paddies [6].

LM compost, composed of water and organic matter, must be reused because it produces greenhouse gasses during composting [7,8]. LM can be converted to biochar by pyrolysis, which can sequestrate carbon in the soil [9], and the biofuel produced can help ameliorate greenhouse gas emissions [10]. In South Korea, growing horticultural crops in winter requires heating facilities because of the low air temperature. Utilizing LM or LM compost as heating fuel in greenhouses might reduce the energy cost [11,12]. Generally, in South Korea, wood pellets are used as agricultural fuel [13]. Dried LM compost can be used as an agricultural fuel. In several farms in South Korea, a dried LM is currently being studied to be applied as an agricultural fuel in a pilot test.

When LM is used as an agricultural fuel in the greenhouse, it produces a combusting gas containing carbon dioxide, nitrogen oxides (NO_x), and sulfur oxides (SO_x) and a bottom ash. A gas treatment facility is needed to purify the exhaust combustion gasses [14]. Most purified combusting gas is carbon dioxide, which can be supplied as a necessary carbon source for vegetable growth in greenhouses in winter [15,16]. This is gas recycling technology. Bottom ash in the combustor and flying ash in the exhaust facility are representative byproducts after combusting. Because these ashes are materials containing inorganic ingredients of LM [3], they may be recycled as agricultural materials. Therefore, there is a necessity for research into recycling resources with these ashes in the agriculture.

In South Korea, an ash study was conducted mainly with bottom ash obtained from coal-fired power plants. Coal bottom ash (CBA) has been reused as artificial aggregates because it is composed of silica oxide and aluminum oxide [17]. CBA was applied as the soil amendment in golf courses and as the carrier of microbes [18,19]. On the other hand, there is no research into the applications of bottom ash produced after combusting dry livestock manure (BACL). The BACL properties differed with coal bottom ash. Research on applying BACL is needed to apply LM compost as agricultural fuel. Turfgrass on a golf course is planted on a sand base that has been blended with soil amendment to improve the properties of the root zone [20,21]. This study examined the effects of BACL applications as a soil amendment on the physicochemical properties of root zone soil and the growth of creeping bentgrass.

2. Materials and Methods

2.1. Materials

The experimental soil was sand matched on the particle distribution of USGA guidelines (

Table 1. Particle size distribution of sand used in this study.

Item	Particle Size (mm)
	>4.00	2.00–4.00	1.00–2.00	0.50–1.00	0.25–0.50	0.15–0.25	0.15–0.053
Sand	0%	3.5 ± 0.4%	5.2 ± 0.4%	39.1 ± 1.8%	24.7 ± 2.%	23.0 ± 1.0%	4.5 ± 0.3%
UGSA guideline	0%	<10%		>60%		>20%	<10%

USGA means United States Golf Association.

). BACL donated from a sweet pepper farm in Cheongsong was applied as the soil amendment, and it was collected at particle sizes of 2–4 mm with sieves.

Table 2. Physicochemical properties of BACL.

Particle Size of BACL	pH	EC	CEC	Bulk Density	T-N	T-P2O5	T-K2O
	(1:5)	(dS∙m−1)	(cmolc∙kg−1)	(g∙cm−3)	(g∙kg−1)
2–4 mm	10.03 ± 0.03 (1)	10.12 ± 0.06	1.15 ± 0.07	0.91 ± 0.03	0.14 ± 0.00	141 ± 9	27.9 ± 0.5

⁽¹⁾ Mean ± standard deviation.

lists the properties of the BACL (Table 2). This was used to evaluate the physicochemical properties of root zone soil blending with sand and BACL. The growth of turfgrass in the root zone soil blended with BACL was investigated. The turfgrass used was a creeping bentgrass (Agrostis palustris L.; Penn A-1) donated from Green Space Co., Ltd. (Cheonan, Republic of Korea). The fertilizer used was a compound fertilizer (CF; N–P₂O₅–K₂O=21–17–17, Namhae Chemical Co., Ltd.; Yeosu, Republic of Korea) purchased from the store.

2.2. Evaluation of Physicochemical Properties in the Root Zone Blending with BACL

This experiment was conducted for two months from July to August 2023. Sand was dried for 16 h in an oven (OF-W155, Daihan Scientific, Daegu, South Korea) at 105 °C to remove moisture. The treatments were as follows: control (only sand without BACL, 100 sand), 3% BACL (3% BACL + 97% sand), 5% BACL (5% BACL + 95% sand), 7% BACL (7% BACL + 93% sand), and 10% BACL (10% BACL + 90% sand). The root zone soil was blended by volume or weight, considering the bulk density of the materials. The physicochemical properties of the soil blending with BACL were investigated, including pH, electrical conductivity (EC), cation exchangeable capacity (CEC), bulk density (BD), capillary porosity (CP), air-filled porosity (AP), total porosity (TP), and hydraulic conductivity (HC). The pH and EC of the root zone were analyzed using a pH meter (Seven Compact pH/ions220, METTLER TOLEDO, Columbus, OH, USA) and an EC meter (Orion 3 star, Thermo Fisher Scientific, Waltham, MA, USA), respectively. The CEC was measured using a 1N-ammonium acetate extraction method (pH, 7.0) [22]. The soil physical properties, such as BD, CP, AP, TP, and HC, were measured using a method reported elsewhere [23]. BD was measured with the compacted bulk density and HC with the constant head method. TP was calculated with BD and particle density (PD).

2.3. Growth of Creeping Bentgrass in the Root Zone Blending Sand and BACL

This experiment was conducted for seven months from September 2023 to March 2024. The root zone soil was blended with BACL (2–4 mm particle size) as a soil amendment. The treatments were as follows: control (100% sand), 3% BACL (3% BACL + 97% sand), 5% BACL (5% BACL + 95% sand), 7% BACL (7% BACL + 93% sand), and 10% BACL (10% BACL + 90% sand). Sand soil blending with BACL was performed in a plastic pot (diameter 12.7 cm, depth 13 cm) and was compacted by irrigation with tap water. The mixture was combined with creeping bentgrass seeds and placed into the pots (10 g∙m⁻²), which were managed for 50 days. CF was applied on 10 November, 8 December, 12 January, and 9 February, and a 1 L∙m⁻² dilution solution (3 N a.i. g∙m⁻²) was applied with the sprayer (Trigger sprayer 700, Apollo Industrial Co., Ltd.; Siheung, South Korea). The soil mixture was not treated with pesticides, such as fungicides and insecticides, and was irrigated with tap water 1–2 times a day. Temperature and relative humidity were 10–32 °C and 70–80%, respectively.

Turfgrass growth was examined with the turf color index (TCI), chlorophyll content, shoot length, and clipping yield. The TCI was measured using the turf color meter (TCM 500, Spectrum Technologies, Inc.; Plainfield, IL, USA) every week from 10 November, and the values were averaged monthly. The chlorophyll content and clipping yield were investigated on 10 November, 8 December, 12 January, 9 February, and 13 March. The samples were collected at a height of 30 mm with scissors and sterilized with 70% ethanol. One aliquot (0.1 g fresh weight) of the sample was analyzed for the chlorophyll content, and another was used to determine the clipping yield [24]. The clipping yield was evaluated according to the dry weight after drying with an oven at 70 °C for 24 h.

Soil samples were dried under shade after being collected on 1 September (the day before the experiment) and 13 March (the final day of the experiment) and were passed through a 2 mm sieve. The pH, EC, organic matter (OM), total nitrogen (T–N), available phosphate (Av-P₂O₅), and exchangeable potassium (Ex-K) were analyzed according to the soil chemical analysis method of the Rural Development Administration (RDA) in South Korea. The main nutrients in the turfgrass leaves were analyzed using the collected clippings (dry weight samples) according to the plant analysis method of the RDA. The nitrogen (N), phosphorus (P), and potassium (K) contents in the leaves were analyzed using the Kjeldahal method with a distillation device, the colorimetric method with a UV-spectrophotometer (UV-1800, Shimadzu, Kyoto, Japan), and the atomic absorption method with a flame photometer (PFP7, Jenway, Staffordshire, UK), respectively.

2.4. Statistical Analysis

Statistical analyses were conducted using Statistical Products and Service Solutions for Windows (SPSS; version 12.1, IBM, New York, NY, USA). The data were analyzed using an analysis of variance (ANOVA), and the differences among the means were tested using Tukey’s test (p < 0.05). The correlation coefficient between the BACL treatment amount and respective factors of soil properties or turfgrass growth was analyzed.

3. Results and Discussion

3.1. Physicochemical Properties of Root Zone Soil Blended with Sand and BACL

The pH and EC of sand blending with BACL were higher than those of the control (

Table 3. Physicochemical properties in the soil after applying BACL.

Treatments (1)	pH	EC	CEC	Bulk Density	Capillary Porosity	Air-Filled Porosity	Total Porosity	Hydraulic Conductivity
	(1:5)	(dS∙m−1)	(cmolc∙kg−1)	(g∙cm−3)	(%)			(mm∙h−1)
Control	7.76 ± 0.14 c (2)	0.18 ± 0.01 c	2.04 ± 0.07 a	1.582 ± 0.007 a	20.5 ± 0.1 d	19.8 ± 0.2 c	40.3 ± 0.3 d	91.1 ± 9.5 d
3% BACL	7.95 ± 0.19 c	0.18 ± 0.01 c	2.24 ± 0.02 a	1.568 ± 0.002 b	20.9 ± 0.1 c	20.0 ± 0.1 bc	40.8 ± 0.1 c	110.6 ± 11.2 c
5% BACL	8.19 ± 0.12 b	0.20 ± 0.02 c	2.16 ± 0.25 a	1.563 ± 0.003 b	21.0 ± 0.1 c	20.0 ± 0.1 bc	41.0 ± 0.1 c	150.9 ± 11.0 b
7% BACL	8.36 ± 0.05 ab	0.23 ± 0.02 b	2.05 ± 0.16 a	1.546 ± 0.009 c	21.3 ± 0.0 b	20.3 ± 0.3 b	41.7 ± 0.3 b	157.3 ± 7.2 ab
10% BACL	8.46 ± 0.01 a	0.28 ± 0.01 a	2.20 ± 0.11 a	1.517 ± 0.002 d	21.8 ± 0.2 a	20.9 ± 0.3 a	42.7 ± 0.1 a	173.2 ± 1.8 a
Correlation	0.9208 **	0.8999 **	0.1666 NS	−0.9564 **	0.9698 **	0.8424 **	0.9564 **	0.9376 **

⁽¹⁾ Treatments were as follows. control: 100% sand; 3% BACL: 3% BACL + 97% sand; 5% BACL: 5% BACL + 95% sand; 7% BACL: 7% BACL + 93% sand; 10% BACL: 10% BACL + 90% sand. BACL means a bottom ash produced after combusting dry livestock manure, and its particle size was 2–4 mm diameter. CF was applied 4 times on 10 November, 8 December, 12 January, and 9 February. ⁽²⁾ Means with same letters within column are not significantly different by Duncan’s multiple range test p ≤ 0.05 level. Mean ± standard deviation. ^NS and ** represent no significance or a significance at the 0.01 probability level by correlation coefficient between the ratio blending BACL and soil factor, respectively.

). The pH and EC of sand were positively correlated with the BACL ratios (p ≤ 0.05). The reason for this was that the pH of BACL was alkaline and the EC was 10.19 ± 0.22 dS∙m⁻¹. The physicochemical properties of the soil changed according to the properties of the soil amendments [25]. The CEC of BACL treatments was not significantly different from that of the control. The CP, TP, and HC were increased by blending BACL. Hence, BACL improved the physical properties of the soil, such as CP, TP, and HC. In golf course management, the improvement of the physical properties of the root zone, such as porosity or hydraulic conductivity, was more important than the chemical properties because it affected the uptake of fertilizers and the growth of turfgrass root in turfgrass management [22,25]. BACL of 2–4 mm particle sizes used in this examination improved the soil physical properties, while BACL particles smaller than 2 mm did not affect th soil physical properties (data no shown). Turfgrass growth in the root zone was investigated, applying BACL (2–4 mm particles) as the soil amendment.

Table 3 shows a correlation among physicochemical factors (

Table 4. Correlation coefficients among physicochemical factors in the soil after applying BACL.

Factors (1)	pH	EC	CEC	BD	CP	AP	TP	HD
pH	1.000 **	0.826 **	0.037 NS	−0.851 **	0.900 **	0.706 **	0.851 **	0.923 **
EC		1.000 **	0.053 NS	−0.937 **	0.930 **	0.848 **	0.937 **	0.813 **
CEC			1.000 **	−0.185 NS	0.166 NS	0.187 NS	0.185 NS	0.131 NS
BD				1.000 **	−0.957 **	−0.945 **	−1.000 **	−0.859 **
CP					1.000 **	0.810 **	0.957 **	0.884 **
AP						1.000 **	0.945 **	0.743 **
TP							1.000 **	0.859 **
HD								1.000 **

⁽¹⁾ EC: electrical conductivity, CEC: cation exchangeable conduct, BD: bulk density, CP: capillary porosity, AP: air-filled porosity, TP: total porosity, HD: hydraulic conductivity. ^NS and ** represent no significance or a significance at the 0.01 probability level by correlation coefficient among physicochemical factors.

). pH was positively corelated between EC, CP, AP, TP, and HD (p ≤ 0.01), and TP was positively correlated between EC, CP, aP, and HD (p ≤ 0.01). All factors, except for CEC, were positively correlated with the ratio blending BACL (p ≤ 0.01, Table 4). The changes in the physicochemical factors in the soil blended with BACL were influenced by the properties of BACL [25].

3.2. Growth of Creeping Bentgrass in the Root Zone Soil Blended with Sand and BACL

This study examined the changes in the chemical properties of the root zone soil before and after growing creeping bentgrass following the application of BACL as a soil amendment (

Table 5. Chemical properties of root zone soil blended with BACL in the creeping bentgrass.

Treatments (1)	pH	EC	OM	T-N	Av-P2O5	Ex-K	CEC
	(1:5)	(dS∙m−1)	(%)		(mg∙kg−1)	(cmolc∙kg−1)
Before	7.45 ± 0.06 c (2)	0.23 ± 0.01 c	0.60 ± 0.06 a	0.006 ± 0.001 a	39 ± 6 e	0.10 ± 0.00 e	1.34 ± 0.04 a
Control	7.54 ± 0.10 c	0.24 ± 0.03 bc	0.55 ± 0.06 a	0.011 ± 0.002 a	46 ± 6 e	0.14 ± 0.01 e	1.47 ± 0.19 a
3% BACL	7.63 ± 0.09 bc	0.26 ± 0.02 b	0.57 ± 0.14 a	0.011 ± 0.001 a	194 ± 19 d	0.19 ± 0.01 d	1.45 ± 0.04 a
5% BACL	7.64 ± 0.05 bc	0.26 ± 0.02 b	0.60 ± 0.06 a	0.010 ± 0.001 a	255 ± 16 c	0.21 ± 0.01 c	1.40 ± 0.02 a
7% BACL	7.74 ± 0.02 ab	0.32 ± 0.00 a	0.59 ± 0.06 a	0.011 ± 0.001 a	316 ± 6 b	0.24 ± 0.00 b	1.46 ± 0.07 a
10% BACL	7.77 ± 0.01 a	0.33 ± 0.01 a	0.59 ± 0.11 a	0.011 ± 0.001 a	352 ± 41 a	0.26 ± 0.01 a	1.43 ± 0.14 a
Correlation (3)	0.8252 **	0.8705 **	0.1598 NS	−0.0560 NS	0.9544 **	0.9846 **	−0.1052 NS

⁽¹⁾ Treatments were as follows. control: 100% sand applying compound fertilizer (CF, 3 N g∙m⁻²∙month⁻¹); 3% BACL: 3% BACL + 97% sand applying CF (v/v), 5% BACL: 5% BACL + 95% sand applying CF; 7% BACL: 7% BACL + 93% sand applying CF; 10% BACL: 10% BACL + 90% sand applying CF. BACL means a bottom ash produced after combusting dry livestock manure. CF was applied 4 times on 10 November, 8 December, 12 January, and 9 February. ⁽²⁾ Means with same letters within column were not significantly different according to Duncan’s multiple range test at p ≤ 0.05 level. Mean ± standard deviation. ^{(3) NS} and ** represent no significance and a significance at the 0.01 probability level by correlation coefficient which was correlated between the ratio blending BACL and soil chemical factor, respectively.

). Compared to soil (only sand) before the BACL treatment, although the soil chemical properties of NF and the control were similar, the pH, EC, Av-P₂O₅, and Ex-K increased after the BACL treatments. In addition, these factors were positively correlated to the ratio applying BACL (p ≤ 0.05). The Av-P₂O₅ supplied by BACL was unavailable to the plant according to the change in pH or the presence of Fe, Al, or Ca in the soil [26]. As the Av-P₂O₅ collects in ponds as a soil leachate in the golf course, it might cause the eutrophication of water [18,27].

The TCI of creeping bentgrass growing in the root zone after blending with BACL was investigated (

Table 6. Turf color index (TCI) of the creeping bentgrass grown in the root zone soil blended with BACL.

Treatments (1)	Turf Color Index (3)
	November	December	January	February	March	Means
NF	6.84 ± 0.07 b (2)	6.31 ± 0.03 b	5.71 ± 0.07 b	5.32 ± 0.08 b	5.05 ± 0.06 b	5.84 ± 0.05 b
Control	7.06 ± 0.08 a	7.35 ± 0.02 a	7.58 ± 0.02 a	7.54 ± 0.03 a	7.07 ± 0.05 a	7.32 ± 0.03 a
3% BACL	7.03 ± 0.04 a	7.34 ± 0.07 a	7.60 ± 0.02 a	7.54 ± 0.03 a	7.17 ± 0.05 a	7.34 ± 0.01 a
5% BACL	7.12 ± 0.09 a	7.33 ± 0.08 a	7.58 ± 0.04 a	7.51 ± 0.02 a	7.17 ± 0.08 a	7.34 ± 0.02 a
7% BACL	7.03 ± 0.07 a	7.38 ± 0.05 a	7.61 ± 0.03 a	7.53 ± 0.02 a	7.18 ± 0.07 a	7.34 ± 0.02 a
10% BACL	7.06 ± 0.05 a	7.37 ± 0.02 a	7.58 ± 0.04 a	7.51 ± 0.02 a	7.12 ± 0.12 a	7.33 ± 0.03 a
Correlation (4)	0.0148 NS	0.2106 NS	0.0438 NS	−0.3908 NS	0.1670 NS	0.1523 NS

⁽¹⁾ Treatments were as follows: control: 100% sand applying compound fertilizer (CF, 3 N g∙m⁻²∙month⁻¹); 3% BACL: 3% BACL + 97% sand applying CF (v/v), 5% BACL: 5% BACL + 95% sand applying CF; 7% BACL: 7% BACL + 93% sand applying CF; 10% BACL: 10% BACL + 90% sand applying CF. BACL means a bottom ash produced after combusting dry livestock manure, and its particle size was 2–4 mm diameter. CF was applied 4 times on 10 November, 8 December, 12 January, and 9 February. ⁽²⁾ Means with same letters within column were not significantly different according to Duncan’s multiple range test at p ≤ 0.05 level. Mean ± standard deviation. ⁽³⁾ The turf color index scale ranged from 1 to 9, with 1 representing the worst, 6 considered acceptable, and 9 representing the best. ^{(4) NS} represents no significance by correlation coefficient between the ratio blending BACL and TCI.

). The NF TCI decreased gradually with the experiment time. Compared to the control, the TCI values after the BACL treatments were similar. The correlation coefficient between the TCI and BACL ratio was not significant. The TCI value is mainly an index representing turfgrass quality, which was affected by N uptake [28]. Kim et al. [28] reported that N application improved the turfgrass quality by promoting N uptake into Zoysia matrella. This might not affect the TCI of turfgrass growing in the root zone blended with BACL because BACL does not contain N (Table 2).

The chlorophyll content was 1707–2167 μg∙g⁻¹ in the leaves of creeping bentgrass growing in root zone blended with BACL (

Table 7. Chlorophyll content and shoot length of the creeping bentgrass grown in the root zone soil blended with BACL.

Treatments (1)	10 November	8 December	12 January	9 February	13 March
Chlorophyll content (μg∙g−1 in fresh wegiht)
Control	1752 ± 48 a (2)	2114 ± 48 a	1984 ± 42 a	1891 ± 42 a	1730 ± 42 a
3% BACL	1787 ± 130 a	2167 ± 121 a	1947 ± 55 a	1832 ± 55 a	1797 ± 55 a
5% BACL	1707 ± 146 a	2069 ± 146 a	1968 ± 146 a	1873 ± 49 a	1755 ± 49 a
7% BACL	1742 ± 63 a	2105 ± 63 a	1986 ± 87 a	1888 ± 63 a	1724 ± 63 a
10% BACL	1738 ± 124 a	2100 ± 124 a	1955 ± 114 a	1867 ± 98 a	1724 ± 98 a
Correlation	0.1989 NS	0.2120 NS	−0.0524 NS	−0.0062 NS	−0.1173 NS
Shoot length (cm)
Control	4.70 ± 0.04 a	5.42 ± 0.01 a	7.32 ± 0.17 a	8.14 ± 0.16 a	5.47 ± 0.06 a
3% BACL	4.65 ± 0.02 a	5.57 ± 0.05 a	7.31 ± 0.02 a	8.22 ± 0.09 a	5.52 ± 0.03 a
5% BACL	7.71 ± 0.04 a	5.57 ± 0.04 a	7.29 ± 0.08 a	8.20 ± 0.13 a	5.63 ± 0.15 a
7% BACL	4.63 ± 0.11 a	5.50 ± 0.17 a	7.37 ± 0.14 a	8.25 ± 0.13 a	5.64 ± 0.24 a
10% BACL	4.66 ± 0.04 a	5.52 ± 0.11 a	7.34 ± 0.04 a	8.21 ± 0.18 a	5.51 ± 0.11 a
Correlation (3)	−0.2263 NS	0.2249 NS	0.1266 NS	0.1849 NS	0.1985 NS

⁽¹⁾ Treatments were as follows. control: 100% sand applying compound fertilizer (CF, 3N g∙m⁻²∙month⁻¹); 3% BACL: 3% BACL + 97% sand applying CF (v/v), 5% BACL: 5% BACL + 95% sand applying CF; 7% BACL: 7% BACL + 93% sand applying CF; 10% BACL: 10% BACL + 90% sand applying CF. BACL means a bottom ash produced after combusting dry livestock manure, and its particle size was 2–4 mm diameter. CF was applied 4 times on 10 November, 8 December, 12 January, and 9 February. ⁽²⁾ Means with same letters within column were not significantly different according to Duncan’s multiple range test at p ≤ 0.05 level. Mean ± standard deviation. ^{(3) NS} represents no significance by correlation coefficient between the ratio blending BACL and chlorophyll content or shoot length.

). The chlorophyll content of the BACL treatments was higher than that of NF and similar to that of the control. The chlorophyll content of turfgrass leaves was related to the N uptake [28,29]. N was not found in the BACL because it was lost in the combustion process [30]. The shoot length of BACL treatments was 2.88–8.25 cm during this experiment (Table 7). The shoot length in the BACL treatments was similar to that of the control.

The clipping yield of turfgrass after the BACL treatment as a soil amendment was 125.7–130.9 g∙m⁻² (

Table 8. Clipping yield collected in the creeping bentgrass grown in the root zone soil blended with BACL.

Treatments (1)	10 November	8 December	12 January	9 February	13 March	Total
	(g∙m−2, Dry Weight)
Control	4.2 ± 0.5 a (2)	12.2 ± 1.4 a	44.8 ± 0.5 a	38.2 ± 0.5 a	26.3 ± 17.0 a	125.7 ± 15.2 a
3% BACL	3.7 ± 0.5 a	11.9 ± 0.8 a	47.9 ± 9.3 a	38.7 ± 9.3 a	28.7 ± 14.8 a	130.9 ± 14.2 a
5% BACL	4.2 ± 0.5 a	12.6 ± 0.9 a	41.3 ± 2.3 a	36.9 ± 2.3 a	30.8 ± 6.4 a	125.9 ± 5.3 a
7% BACL	4.2 ± 0.9 a	11.8 ± 0.8 a	42.9 ± 3.3 a	38.4 ± 3.3 a	30.3 ± 12.6 a	127.6 ± 13.5 a
10% BACL	4.2 ± 0.5 a	12.9 ± 1.2 a	43.7 ± 10.5 a	37.4 ± 10.8 a	28.7 ± 10.8 a	126.9 ± 11.9 a
Correlation (3)	0.1141 NS	0.1394 NS	−0.1516 NS	−0.0252 NS	0.1889 NS	−0.0027 NS

⁽¹⁾ Treatments were as follows. control: 100% sand applying compound fertilizer (CF, 3 N g∙m⁻²∙month⁻¹); 3% BACL: 3% BACL + 97% sand applying CF (v/v), 5% BACL: 5% BACL + 95% sand applying CF; 7% BACL: 7% BACL + 93% sand applying CF; 10% BACL: 10% BACL + 90% sand applying CF. BACL means a bottom ash produced after combusting dry livestock manure, and its particle size was 2–4 mm diameter. The clipping yield was collected on 10 November, 8 December, 12 January, and 9 February, and then CF was applied. ⁽²⁾ Means with same letters within column were not significantly different according to Duncan’s multiple range test at p ≤ 0.05 level. Mean ± standard deviation. ^{(3) NS} represents no significance by correlation coefficient between the ratio blending BACL and a collected clipping yield.

). The clipping yield of BACL treatments was similar to the control. The BACL treatments affected the clipping yield in turfgrass growth by fertilization, not through P₂O₅ or K₂O but through N [30,31]. BACL did not affect turfgrass growth, such as the clipping yield and shoot length, because it mainly contained P₂O₅ or K₂O (Table 2). In this experiment, the clipping yield was correlated with the shoot length in creeping bentgrass (r = 0.9767 **, p ≤ 0.01).

The dry weight of the shoot and root in the creeping bentgrass sampled on 13 March 2024 was 259.6–286.0 g∙m⁻² and 325.0–353.1 g∙m⁻², respectively (

Table 9. Growth of shoot and root in the creeping bentgrass grown in the root zone soil blended with BACL.

Treatments (1)	Dry Weight of Shoot	Dry Weight of Root	T/R Ratio
	(g∙m−2)		(g∙g−1)
Control	259.6 ± 23.1 a (2)	325.0 ± 19.6 a	0.80 ± 0.1 a
3% BACL	261.2 ± 12.7 a	338.4 ± 4.8 a	0.77 ± 0.0 a
5% BACL	286.0 ± 29.2 a	349.4 ± 3.3 a	0.82 ± 0.1 a
7% BACL	270.7 ± 2.3 a	353.1 ± 6.3 a	0.77 ± 0.0 a
10% BACL	270.4 ± 17.6 a	336.3 ± 27.8 a	0.81 ± 0.0 a
Correlation (3)	0.2335 NS	0.3106 NS	−0.0029 NS

⁽¹⁾ Treatments were as follows. control: 100% sand applying compound fertilizer (CF, 3 N g∙m⁻²∙month⁻¹); 3% BACL: 3% BACL + 97% sand applying CF (v/v), 5%BACL: 5% BACL + 95% sand applying CF; 7% BACL: 7% BACL + 93% sand applying CF; 10% BACL: 10% BACL + 90% sand applying CF. BACL means a bottom ash produced after combusting dry livestock manure, and its particle size was 2–4 mm diameter. CF was applied 4 times on 10 November, 8 December, 12 January, and 9 February. The dry weight of the shoot and root of the creeping bentgrass was investigated on 15 March 2024. ⁽²⁾ Means with same letters within column were not significantly different according to Duncan’s multiple range test at p ≤ 0.05 level. Mean ± standard deviation. ^{(3) NS} represents no significance by correlation coefficient between the ratio blending BACL and partial dry weight of turfgrass.

). The dry weight of the shoot and root in the BACL treatments was higher than those of NF and similar to those of the control. Although the correlation coefficient between the shoot dry weight and the BACL blending ratio was not significant, the root dry weight was positively correlated with the BACL blending ratio (p ≤ 0.05). As 2–4 mm BACL was applied as a soil amendment to improve the capillary porosity in root zone soil (Table 3), it might promote turfgrass root growth and water uptake [21]. An improvement in the root growth by the BACL treatment could increase shoot growth by promoting nutrient uptake in creeping bentgrass [32]. Kim and Lim [33] reported that the BACL treatment as a soil amendment improved the root growth of perennial ryegrass (Lolium perenne L.).

The N, P, and K contents of shoot leaves in creeping bentgrass after BACL treatment as soil amendment were 3.27–3.50%, 0.15–0.16%, and 1.08–1.13%, respectively, and their uptake was 12.58–13.99 g∙m⁻², 0.59–0.68 g∙m⁻², and 4.20–4.60 g∙m⁻², respectively (

Table 10. Nutrient content and uptake of the shoot and root of the creeping bentgrass grown in the root zone soil blended with BACL.

Treatments (1)	Nutrient Content in the Tissue (%)			Nutrient Uptake (g/m2)
	N	P	K	N	P	K
Shoot
Control	3.27 ± 0.20 a (2)	0.15 ± 0.04 a	1.09 ± 0.02 a	12.58 ± 0.07 a	0.59 ± 0.05 a	4.20 ± 0.24 a
3% BACL	3.38 ± 0.20 a	0.15 ± 0.02 a	1.08 ± 0.02 a	13.27 ± 0.44 a	0.60 ± 0.10 a	4.25 ± 0.35 a
5% BACL	3.38 ± 0.20 a	0.16 ± 0.00 a	1.11 ± 0.04 a	13.99 ± 0.98 a	0.68 ± 0.06 a	4.60 ± 0.42 a
7% BACL	3.50 ± 0.35 a	0.16 ± 0.03 a	1.13 ± 0.06 a	13.90 ± 2.41 a	0.65 ± 0.11 a	4.50 ± 0.76 a
10% BACL	3.38 ± 0.53 a	0.15 ± 0.02 a	1.10 ± 0.06 a	13.51 ± 2.33 a	0.61 ± 0.10 a	4.37 ± 0.58 a
Correlation (3)	0.1737 NS	0.0599 NS	0.2184 NS	0.2570 NS	0.1306 NS	0.2645 NS
Root
Control	2.22 ± 0.20 a	0.14 ± 0.02 bc	1.18 ± 0.17 b	7.23 ± 0.48 b	0.46 ± 0.05 bc	3.85 ± 0.04 c
3% BACL	2.45 ± 0.35 a	0.14 ± 0.02 bc	1.38 ± 0.13 a	8.29 ± 0.14 ab	0.48 ± 0.07 bc	4.68 ± 0.10 b
5% BACL	2.57 ± 0.20 a	0.17 ± 0.02 ab	1.54 ± 0.11 a	8.97 ± 0.34 a	0.61 ± 0.09 ab	5.39 ± 0.47 a
7% BACL	2.45 ± 0.00 a	0.19 ± 0.04 ab	1.57 ± 0.05 a	8.65 ± 0.80 ab	0.65 ± 0.22 a	5.54 ± 0.54 a
10% BACL	2.45 ± 0.00 a	0.20 ± 0.03 a	1.57 ± 0.04 a	8.24 ± 0.69 ab	0.66 ± 0.23 a	5.55 ± 0.28 a
Correlation (3)	0.3413 NS	0.6751 *	0.7691 **	0.3725 NS	0.6956 **	0.8217 **

⁽¹⁾ Treatments were as follows. control: 100% sand applying compound fertilizer (CF, 3 N g∙m⁻²∙month⁻¹); 3% BACL: 3% BACL + 97% sand applying CF (v/v), 5% BACL: 5% BACL + 95% sand applying CF; 7% BACL: 7% BACL + 93% sand applying CF; 10% BACL: 10% BACL + 90% sand applying CF. CF was applied 4 times on 10 November, 8 December, 12 January, and 9 February. BACL means a bottom ash produced after combusting dry livestock manure, and its particle size was 2–4 mm diameter. The shoot and root of the creeping bentgrass was sampled on 15 March 2024. ⁽²⁾ Means with same letters within column were not significantly different according to Duncan’s multiple range test at p ≤ 0.05 level. Mean ± standard deviation. ^{(3) NS}, *, and ** represent no significance or a significance at the 0.05 and 0.01 probability level by correlation coefficient between the ratio blending BACL and content or uptake amount of nutrient, respectively.

). The correlation coefficient between the blending ratio of BACL and nutrient content or uptake amount was not significant. The N, P, and K contents of the root tissue in creeping bentgrass after the BACL treatment were 2.22–2.57%, 0.14–0.20%, and 1.18–1.57%, respectively, and they correlated with the blending ratio of BACL positively (p ≤ 0.05). The P and K levels of the root were higher in the 10% BACL-treated soil than in the control. The N, P, and K uptake were 7.23–8.97 g∙m⁻², 0.46–0.66 g∙m⁻², and 3.85–5.55 g∙m⁻², respectively, and positively correlated with the BACL blending ratio (p ≤ 0.01). The root growth of creeping bentgrass in the BACL treatment was positively related to the P content of the root (r_P = 0.5867 **, p ≤ 0.01) or the K content (r_K = 0.5867 **, p ≤ 0.01). When BACL used as a soil amendment was blended with sand, the P or K in BACL was taken up by the turfgrass (Table 2 and Table 4). P and K in the soil improved root growth and their uptake in the turfgrass [34], but did not improve shoot growth [31]. In this experiment, the application of BACL did not affect the creeping growth and quality, and the same amount of N was fertilized. Generally, turfgrass growth or quality was related to N application [31].

The fuel of the biomass boiler applied for green houses in South Korea consists of biomass material, such as wood pellets and coals. Recently, types of biomass fuel are diversifying [35]. Livestock manure, which mainly consist of water and organic matter, is not only used as a composting fertilizer but also as a biomass fuel [36]. Bottom ash is produced during the biomass fuel combustion process and required recycling [35].

The agricultural recycling of bottom ash was used for soil amendment or fertilizer [35]. As bottom ash produced from coal plants is used as a soil amendment, it increases the capillary porosity and decreases leachates [18]. The pH of soil blending with bottom ash was alkaline due to its high pH value. In this study, the pH value of sand soil blending with BACL was alkaline (Table 3). The particle size of the soil amendment affected the physicochemical properties [36]. Perlites of large particle sizes increased the soil porosity and hydraulic conductivity, while zeolites of small particle sizes increased CEC [36]. Cabalar and Akbulut [37] reported that the hydraulic conductivity of large sand particles increased in speed. Applying 2–4 mm BACL increased soil physical properties like porosity and hydraulic conductivity (Table 3).

Soil porosity slightly improved turfgrass quality and growth [38]. The shoot growth of turfgrass was promoted by the root growth [38]. Turfgrass root absorbed water and nutrients from the soil, thereby improving root and shoot growth [39]. BACL treatment enhanced the uptake of phosphorus and potassium in the root of the creeping bentgrass (Table 10). Creeping bentgrass grown without N fertilizer impacted its growth and quality due to its very low N content. Therefore, N was used to fertilize turfgrass when BACL was used as a soil amendment.

As summarized in this examination, applying BACL as a soil amendment improved the porosity and hydraulic conductivity in the root zone and promoted root growth after seeding creeping bentgrass. The porosity of soil treated with BACL was positively correlated with the dry weight of the root (p ≤ 0.01). BACL had higher P and K contents than N, so it might be a fertilizing source in the early root growth of creeping bentgrass. The BACL from feed or feed supplements must be monitored for changes in major constituents during collection season [40] and for heavy metals, such as copper and zinc [41].

4. Conclusions

BACL is an inorganic material produced by combusting dry livestock manure fuel. This study was conducted to investigate the change in physicochemical properties in sand soil blended with BACL and the change in the growth and quality of creeping bentgrass. The application of BACL was positively correlated with soil porosity and hydraulic conductivity. The positive change in these physical factors in the sand-based root zone suggests potential use as a soil amendment, with their application enhancing the root growth of turfgrass.

As compared to the control, the shoot growth of creeping bentgrass grown in the sand-based root zone amended with BACL was not significantly different, while the phosphorus and potassium uptake in the roots increased. Since BACL mainly contains phosphorus and potassium, these nutrients are absorbed by the root of turfgrass. These results indicate that the application of BACL as a soil amendment improved soil porosity and hydraulic conductivity and enhanced phosphorus and potassium levels in the turfgrass root. BACL containing phosphorus and potassium may be utilized as a fertilizer source and applied as a soil amendment in turfgrass fields such as in home gardens, arboretums, turfgrass farms, soccer fields, and golf courses.