Influence of biochar use on sugarcane growth, soil parameters, and groundwater quality.
This study deals with the influence of biochar use on sugarcane
growth and nitrate-nitrogen percolation losses, as well as chemical and
physical properties of Shimajiri maji soil. Two varieties of biochars,
biosolids and bagasse (residues of sugarcane stalks after juice
extraction), were mixed with Shimajiri maji soil. Changes in
nitrate-nitrogen concentration in percolating water, specific gravity,
and available soil moisture before sugarcane planting and after harvest
were investigated. Indices of sugarcane growth (stem diameter and
length), Brix, and yield of estimated available sugar in each plot were
Results indicated that bagasse charcoal reduced soil dry density and increased available moisture of Shimajiri maji soil. Maintaining suitable soil water content increased yields and sugar content of sugarcane, while nitrate-nitrogen concentration in percolating water also decreased. Hence, bagasse charcoal use may reduce nitrogen loads in Shimajiri maji soil.
Additional keywords: available soil moisture, Brix, nitrate-N, soil water content, water balance, yield of estimated available sugar.
Sugarcane (Environmental aspects)
|Publication:||Name: Australian Journal of Soil Research Publisher: CSIRO Publishing Audience: Academic Format: Magazine/Journal Subject: Agricultural industry; Earth sciences Copyright: COPYRIGHT 2010 CSIRO Publishing ISSN: 0004-9573|
|Issue:||Date: Sept-Nov, 2010 Source Volume: 48 Source Issue: 6-7|
|Topic:||Event Code: 310 Science & research Computer Subject: Company growth|
|Product:||Product Code: 2861250 Charcoal; 0133100 Sugar Cane NAICS Code: 325998 All Other Miscellaneous Chemical Product and Preparation Manufacturing; 11193 Sugarcane Farming SIC Code: 2819 Industrial inorganic chemicals, not elsewhere classified; 2861 Gum and wood chemicals; 0133 Sugarcane and sugar beets|
|Geographic:||Geographic Scope: Australia Geographic Code: 8AUST Australia|
Shimajiri maji soil comprises ~90% of the total cultivated area of Miyako Island, southern Japan. A low level of available soil moisture and highly saturated hydraulic conductivity are predominant growth-limiting factors of Shimajiri maji soil. Sugarcane is the main crop on Miyako Island, and sugarcane quality is influenced by available soil moisture and nutrient content (Sumi et al. 2001).
Furthermore, groundwater is the source of most agricultural and drinking water on Miyako Island. In recent years, groundwater quality has deteriorated because of inappropriate management of cattle manure and superfluous fertilisation (Nakanishi et al. 2001; Tashiro and Takahira 2001). It is essential to reduce nitrate-nitrogen (N) concentration in percolating water to ensure water purity. Use of biochars in Shimajiri maji soil decreases nitrate-N in percolating water by denitrification of the nitrate-N and adsorption of ammonium-N by charcoal (Chen and Shinogi 2005).
In this study, we examined the potential for improving water quality using biochars in Shimajiri maji soil. We evaluated the effects of using 2 varieties of biochar: (i) bagasse (residues of sugarcane stalks after juice extraction), and (ii) biosolids. Biosolids charcoal is expected to function as a fertiliser (Niwa et al. 2001; Maid and Watanabe 2004; Shingyouji and Matsumaru 2007) on Shimajiri maji soil and facilitate sugarcane growth, nitrate-N concentration in percolating water, and available soil moisture.
The bagasse and the biosolids were collected on Miyako Island, the former from a sugar factory, the latter from agricultural sewage. Bagasse was heated to 600[degrees]C using an outer-side, 3-stage, screw-conveyor furnace. Biosolids were heated to 600[degrees]C using an outer-side, rotary-kiln furnace. Chemical and physical properties of bagasse and biosolids charcoals were then measured. Chemical properties (pH, N[H.sub.4]-N, N[O.sub.3]-N, total N, total C, [P.sub.2][O.sub.5], [K.sub.2]O contents) as well as physical properties (specific surface area, micropore volume, iodine adsorption ability, dry density) are presented in Table 1. A scanning electron microscope (SEM) image of bagasse charcoal is indicated in Fig. 1. The mean pore size of bagasse charcoal is regular grid.
Concentrations of total N, N[H.sub.4]-N, P, and K were higher in biosolids charcoal than in bagasse charcoal, whereas the concentration of total C was lower in biosolids charcoal than in bagasse. The most significant N component in both varieties of charcoal was organic N.
[FIGURE 1 OMITTED]
Fine-fibred bagasse charcoal was lighter than biosolids charcoal (dry density of bagasse charcoal 0.08 g/[cm.sup.3]) and the specific surface area of bagasse charcoal was 15 times greater than biosolids charcoal. The iodine adsorption ability of bagasse charcoal was 1.7 times higher than for biosolids charcoal.
Six outdoor lysimeter plots were set up at the Miyago Island Branch of Okinawa Prefectural Agricultural Research Center. The main soil in Miyago Island, Shimajiri maji, was used to fill the lysimeter. Physical properties of Shimajiri maji are indicated in Table 2; the soil texture of Shimajiri maji is heavy clay. The dimensions of each plot were 3.0 by 3.0 by 1.35 m (1.0 m depth Shimajiri maji and 0.35 m rock). Sugarcane was grown from July 2005 to October 2006.
Plots were performed in duplicate and comprised: (i) control (chemical fertiliser use only); (ii) bagasse charcoal (3% by weight in 0.30 m ploughing-depth soil, N equivalent 333 kg/ha, inorganic N equivalent 0 kg/ha); (iii) biosolids charcoal (1% by weight in 0.30m ploughing-depth soil, N equivalent 438 kg/ha, inorganic N equivalent 33 kg/ha).
The chemical fertiliser used was N : [K.sub.2]O : [P.sub.2][O.sub.5] (16%:9%:9%). Base fertiliser was applied on 28 July 2005 at 450 kg/ha (72 kg N/ha). Topdressing was applied on 20 October 2005 at 300 kg/ha (48 kg N/ha), and again on 21 February 2006 at 750 kg/ha (120 kg N/ha).
During cultivation, percolating water was collected from each plot. Discharge and nitrate-N concentration in percolating water were analysed by ion chromatography. Rainfall was recorded with a rain gauge. The nitrate-N concentration of in both rainfall and irrigation water were measured.
Indices of sugarcane growth such as stem diameter, length, and weight, SPAD (Soil and Plant Analyzer Development) value, Brix, fibre content, polarisation (sucrose content of juice), and N concentration were measured in each part of the plant. Analyses were as follows: total plant N, by NC analyser (combustion method); SPAD value, using apparatus for measuring chlorophyll content; Brix, with a Brix meter; fibre content, by the decoct-drying process; polarisation, by refractometer. Yield of estimated available sugar was calculated as follows:
YEAS (kg/a) = CCS (%) x YS (kg/a) (1)
CCS = [3P (95 - F) - B (97 - F)]/200 (2)
where YEAS is yield of estimated available sugar, CCS is commercial cane sugar, YS is yield of stalk, P is polarisation, B is Brix, and F is fibre content (Saranin 1986).
Soil moisture in each plot was analysed weekly when initiating cultivation using soil moisture meters manufactured by Hydrosense. Physical properties such as available soil moisture, specific gravity, dry density, and permeability, as well as chemical properties such as total N and total carbon contents, were measured in each plot before and after cultivation. Total N and carbon content of soils was analysed by NC analyser (combustion method) and available soil moisture (pF 1.6-3.0) was analysed by the pressure-plate method.
Results and discussion
Changes in soil moisture for each plot during the first 10 weeks of cultivation are presented in Fig. 2. No significant differences in soil moisture were observed between biosolids and control plots. Soil moisture in bagasse charcoal plots was significantly higher than in the other plots. Thus, bagasse charcoal, with its high water-absorption rate (500%), could have increased soil moisture.
Sugarcane plants photographed in October 2005 are shown in Fig. 3; the average height of sugarcane stalks in the plots for both varieties of biochar was observed to be greater than that in the control plots. Sugarcane growth is summarised in Table 3. The stalk crop in the biosolids plot was greater than in the other plots. We believed that N (inorganic) from biosolids charcoal increased the yield of sugarcane in that plot. Brix level in the bagasse charcoal plot was higher than in the other plots, and consequently, yield of estimated available sugar was higher. Because pF levels of 2.0-3.0 provided higher water use efficiency for sugarcane (Hossain et al. 2002), maintaining appropriate levels of soil water content increased the yield as well as sugar content of sugarcane. The observed differences between the varieties of biochar in their effects on sugarcane growth may be explained by differences in chemical properties and porosity.
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
[FIGURE 4 OMITTED]
Changes in cumulative percolating water volume (Fig. 4) show that the amount of percolating water was reduced by 9 and 12% with bagasse and biosolids charcoal use, respectively. The water balance of each plot is indicated in Fig. 5. Because of the change in soil moisture in the bagasse charcoal plot, evapotranspiration from increased transpiration was greater only in the biosolids charcoal plot than in the control plot, and percolation in both varieties of biochar plots was lower than in the control plot.
[FIGURE 5 OMITTED]
[FIGURE 6 OMITTED]
[FIGURE 7 OMITTED]
Changes in cumulative loads of nitrate-N for each plot are shown in Fig. 6. Nitrate-N concentrations in percolating water were reduced by 59% with bagasse charcoal use through absorption and increased denitrification. Although nitrate-N concentration in the biosolids charcoal plot was higher than in the control plot, percolating water level was reduced by 12% with biosolids charcoal use. In addition, nitrate-N concentration in percolating water reduced by 11% with bagasse charcoal use.
The N balance of each plot is indicated in Fig. 7. Although there was more sugarcane stalk and top in the bagasse and biosolids charcoal plots than in the control, the N concentration of both stalk and top in both varieties of biochar plots was lower than in the control plot, and N absorption by stalk and top was lower than for the control. Furthermore, the N concentration in dead leaves was twice that of the stalk; hence, we believe that dead leaves could be used as a good-quality N fertiliser. In addition, bagasse charcoal use increased N absorption for sugarcane and N accumulation in the soil, along with decreased N eluviation. Therefore, we conclude that bagasse charcoal reduces N loads in Shimajiri maji soil.
Chemical and physical properties of soil
Nitrogen and carbon concentrations increased in the soil with biochar use (Table 4). In particular, carbon concentration in the bagasse charcoal plot increased greatly. Furthermore, topdressing and earthing-up were performed twice during the cultivation, with resulting reduction in soil carbon concentration by physical spreading.
The dry density of Shimajiri maji soil decreased with bagasse charcoal use (Table 5). Therefore, sugarcane roots in that plot were thicker and longer than in other plots. Furthermore, the available soil moisture increased the bagasse charcoal function. Although the soil in each plot hardened by farm work and consolidation from irrigation and rainfall, and the available soil moisture had fallen during the cultivation period, the soil in the bagasse charcoal plot still maintained a higher available soil moisture than the other plots.
The results indicate that bagasse charcoal increases available soil moisture in Shimajiri maji soil. Therefore, maintaining an appropriate level of water content in the soil increases not only yield but also sugar content in sugarcane. In addition, N absorption by sugarcane as well as decreased N eluviation and accumulation in the soil can be achieved with bagasse charcoal use. Therefore, we conclude that bagasse charcoal use can reduce N loads in Shimajiri maji soil. Taking into account the soil conditions on Miyako Island, bagasse charcoal could play an important role in groundwater conservation and soil improvement in future.
This work was supported by a grant from the Ministry of Agriculture, Forestry and Fisheries of Japan (Rural Biomass Research Project, BEC (Biomass Ethanol Conversion)--6100).
Manuscript received 5 January 2010, accepted 5 May 2010
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Yan Chen (A,C), Yoshiyuki Shinogi (A), and Masahiko Taira (B)
(A) National Agriculture and Food Research Organization, National Institute for Rural Engineering, 2-1-6 Kannondai, Tsukuba-shi, Ibaraki 305-8609, Japan.
(B) Department of Agriculture, Forestry and Fisheries, Okinawa Prefectural Government, 517 Yamakawa, Haebaru-Cho, Okinawa 901-1115, Japan.
(C) Corresponding author. Email: email@example.com
Table 1. Chemical and physical properties of biochars Charcoal: Bagasse Biosolids Specific surface area ([m.sup.2]/g) 32.9 2.2 Micropore volume (mL/g) 0.04 0.01 Iodine adsorption ability (mg/g) 237 135 Dry density (g/[cm.sup.3]) 0.08 0.4 pH([H.sub.2]O) 7.3 7.2 Total N (g/kg) 3.7 14.6 N[H.sub.4.sup.+] -N (g/kg) 0.0 0.9 N[O.sub.3] -N (g/kg) 0.0 0.0 Total C (g/kg) 632.3 151.4 [P.sub.2][O.sub.5] (mg/kg) 0.8 4.1 [K.sub.2]O (mg/kg) 19.9 125.2 Table 2. Physical properties of soil in the study plots Particle size distribution (%) Specific Soil gravity Gravel Coarse Fine Silt Clay texture sand sand 2.76 0.26 0.77 7.32 32.96 58.69 HC Table 3. Comparison of sugarcane growth in each plot Plot Stalk length Stalk diam. (cm) (cm) Control 205.0 [+ or -] 22.3 2.35 [+ or -] 0.19 Bagasse charcoal 218.4 [+ or -] 16.9 2.55 [+ or -] 0.21 Biosolids charcoal 233.1 [+ or -] 22.5 2.43 [+ or -] 0.17 Plot Stalk weight SPAR (g) Control 618.4 [+ or -] 93.8 36.1 [+ or -] 3.26 Bagasse charcoal 801.5 [+ or -] 69.5 33.2 [+ or -] 3.40 Biosolids charcoal 693.1 [+ or -] 43.5 35.0 [+ or -] 4.69 Plot Brix Fibre cont. (%) Control 16.9 [+ or -] 0.42 15.1 [+ or -] 0.1 Bagasse charcoal 17.9 [+ or -] 0.71 15.3 [+ or -] 0.9 Biosolids charcoal 14.8 [+ or -] 018 14.8 [+ or -] 0.5 Plot Polarisation Stalk crop (%) (kg/ha) Control 8.7 [+ or -] 0.1 944.4 [+ or -] 137.1 Bagasse charcoal 11.4 [+ or -] 0.7 1000.0 [+ or -] 6.5 Biosolids charcoal 6.2 [+ or -] 0.5 1133.3 [+ or -] 49.2 Dry weight of sugarcane (kg/ha) Plot Yield estim. avail. sugar (kg/ha) Dead leaves Tops Stalk Control 51.1 [+ or -] 12.9 97.0 16.3 129.0 Bagasse charcoal 91.1 [+ or -] 2.6 94.1 18.8 19.4 Biosolids charcoal 48.7 [+ or -] 1.4 97.4 19.9 16.8 Concentration of N (%) Plot Dead leaves Tops Stalk Control 0.59 0.97 0.47 Bagasse charcoal 0.66 0.83 0.37 Biosolids charcoal 0.63 0.93 0.44 Table 4. Changes in chemical properties of soil Plot Total N (%) Oct. 2005 Sept. 2006 Control 0.14 [+ or -] 0.01 0.16 [+ or -] 0.00 Bagasse charcoal 0.18 [+ or -] 0.02 0.21 [+ or -] 0.02 Biosolids charcoal 0.20 [+ or -] 0.02 0.23 [+ or -] 0.02 Plot Total C (%) Oct. 2005 Sept. 2006 Control 0.69 [+ or -] 0.13 0.69 [+ or -] 0.15 Bagasse charcoal 5.01 [+ or -] 0.15 4.21 [+ or -] 0.14 Biosolids charcoal 1.22 [+ or -] 0.21 1.18 [+ or -] 0.23 Table 5. Changes in physical properties of soil Plot Specific gravity Control 2.81 [+ or -] 0.063 Bagasse charcoal 2.71 [+ or -] 0.039 Biosolids charcoal 2.76 [+ or -] 0.020 Plot Dry density (g/[cm.sup.3]) Oct. 2006 Sept. 2006 Control 0.86 [+ or -] 0.04 1.07 [+ or -] 0.10 Bagasse charcoal 0.57 [+ or -] 0.12 0.70 [+ or -] 0.16 Biosolids charcoal 0.87 [+ or -] 0.13 1.00 [+ or -] 0.08 Plot Permeability (cm/s) Oct. 2006 Sept. 2006 Control 0.079 [+ or -] 0.022 0.016 [+ or -] 0.004 Bagasse charcoal 0.047 [+ or -] 0.011 0.011 [+ or -] 0.003 Biosolids charcoal 0.077 [+ or -] 0.022 0.021 [+ or -] 0.004 Plot Available soil moisture (%) Oct. 2006 Sept. 2006 Control 28.54 [+ or -] 2.78 14.14 [+ or -] 1.39 Bagasse charcoal 39.32 [+ or -] 0.23 16.06 [+ or -] 0.55 Biosolids charcoal 29.13 [+ or -] 5.25 10.97 [+ or -] 4.05
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