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Variation in Growth Attributes, Dry Matter Yield and Quality Among 6 Genotypes of Napier Grass used for Biomass in Year of Establishment in Southern Kyushu, Japan



Lizah Khairani, Yasuyuki Ishii, Sachiko Idota, Renny Fatmyah Utamy and Aya Nishiwaki
 
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ABSTRACT

As for estimating the suitability of napier grass for biomass use in southern Kyushu, Japan, the objective of this study was to determine the most suitable genotype of napier grass for dry matter production and quality (fiber content) for biomass ethanol conversion in the year the plants were established. Six genotypes of napier grass, a dwarf early-heading type, a dwarf late-heading type, a hybrid of pearl millet with napier grass, a purple-foliage type and normal varieties of Merkeron and Wruk wona, were examined for growth attributes, dry matter yield, chemical composition and in vitro Dry Matter Digestibility (IVDMD) at the University of Miyazaki in southern Kyushu, Japan in 2009. Dry matter yield ranged from 13.4 to 33.5 Mg ha-1, with the highest yielder being normal Wruk wona, followed by Merkeron. Hemicellulose and cellulose content of both Leaf Blade (LB) and stem inclusive of leaf sheath (ST) did not differ significantly among genotypes, except for cellulose content in ST which was significantly higher for the dwarf early-heading type than for the other genotypes. The dwarf late-heading type had significantly higher IVDMD in ST (65.8%) due to lower acid detergent lignin and cellulose content in ST than the other genotypes. Based on dry matter production, fiber (carbohydrate) content in the current study and theoretical conversion efficiency from cellulose and hemicelluloses of 0.29 and 0.23, respectively, Merkeron appears the most promising genotype for biomass production, with theoretical ethanol production potential of 5850 L ha-1 year-1 in the year of establishment.

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Lizah Khairani, Yasuyuki Ishii, Sachiko Idota, Renny Fatmyah Utamy and Aya Nishiwaki, 2013. Variation in Growth Attributes, Dry Matter Yield and Quality Among 6 Genotypes of Napier Grass used for Biomass in Year of Establishment in Southern Kyushu, Japan. Asian Journal of Agricultural Research, 7: 15-25.

DOI: 10.3923/ajar.2013.15.25

URL: https://scialert.net/abstract/?doi=ajar.2013.15.25
 
Received: January 04, 2013; Accepted: February 11, 2013; Published: May 18, 2013



INTRODUCTION

By 2030, the Biomass Japan Comprehensive Strategy Promotion Council estimates that Japan will produce 6.0 million kL year-1 of bioethanol using domestic biomass resources, composed of 1.8-2.0 million kL year-1 from herbage as raw material (MAFF, 2007; Tanaka, 2007). It is very important to find the best candidate herbage and energy crop species in addition to crop by-products such as rice and wheat straw and sugarbeet and sugarcane tops which already are available and can also grow on currently unused agricultural lands (390 thousand ha in Japan) with no competition for cultivation of food crops (Maeda, 2007). However, for bioethanol purposes apart from Dry Matter (DM) production, plant materials should suit quality parameters to reach optimal energy efficiency which means high levels of fiber content and minimized environmental pollution which means low levels of water, N and ash content (Lemus et al., 2002; McKendry, 2002).

The bioethanol industry will need a continuous and reliable supply of biomass that can be produced at a low cost and with minimal use of water, fertilizer and arable land. As many C4 plants utilize light, water and nitrogen at high efficiency compared with C3 species, some might be ideal for energy crops and one candidate that offers significant potential for biomass use and is already adapted to Japan is napier grass (Pennisetum purpureum Schumach). Normal varieties of napier grass have been grown in several areas (Ito and Inanaga, 1988; Ito et al., 1988) for feedstock purposes under the cut-and-carry system (Ishii et al., 1995) and a dwarf variety has recently been adapted to the cut-and-carry (Mukhtar et al., 2003) and grazing system (Ishii et al., 2005).

Napier grass is highly efficient at converting solar energy into chemical energy and is also efficient in fixing atmospheric CO2, it is capable of accumulating 10-85 mg DM ha-1 year-1 and its production potential is higher than other tropical grasses (Humphreys, 1994; Skerman and Riveros, 1990). However, yields of the grass vary depending on genotype (Schank et al., 1993; Cuomo et al., 1996), edaphic and climatic factors and management practice (Chaparro et al., 1995, 1996; Woodard and Prine, 1993). Boonman (1993) reported that napier grass accumulated a large quantity of DM (29 Mg DM ha-1 year-1) in a single cut per year when grown uninterruptedly for 3 years in Kenya while the yield varied from 10 to 40 Mg DM ha-1 year-1 depending on soil fertility, climate and management (Schreuder et al., 1993). Under four regimes of annual nitrogen (N) supply between 0 and 2000 kg ha-1, annual DM yield in napier grass varied from 18.3 to 49.7 Mg ha-1 in Australia (Ferraris, 1980) and from 10.7 to 85.9 Mg ha-1 in Puerto Rico under seven levels of N supply (0-2223 kg N ha-1) (Vicente-Chandler et al., 1959; Skerman and Riveros, 1990). Napier grass must be grown uninterruptedly under a high level of fertilizer N supply in the year of establishment to optimize ethanol production from the plants.

In feasibility studies of biomass to ethanol production in Hawaii, napier grass was the highest yielding and lowest cost feedstock using simultaneous saccharification and fermentation conversion (Mielenz, 1997). In napier grass, 42 Mg DM ha-1 produced 12,099 L ha-1 compared with energy cane (Saccharum spp.) at 108.2 Mg DM ha-1, yielding 44,300 L of ethanol ha-1. In Florida, sugarcane and napier grass achieved the highest yielding and the lowest cost biomass, at 54.4 Mg ha-1 and $21 Mg-1 and 44.5 Mg DM ha-1 and $22 Mg-1, respectively (Mielenz, 1997).

Dry matter yield and quality suitable for biomass use are expected to be variable, depending on the variation in growth attributes among genotypes of napier grass as affected by local climatic and edaphic factors at the examined site. High digestibility of feedstock facilitates enzymatic saccharification with cellulase (Kai et al., 2010). Therefore, the objective of this study was to determine the most suitable genotype of napier grass for dry matter production and quality (fiber content) for biomass use in ethanol conversion and to find the growth attributes, including digestibility which were closely correlated with high yield and quality under a favorable fertilizer supply without interruption in the year of establishment in southern Kyushu, Japan.

MATERIALS AND METHODS

Experimental site and climatic conditions: The study was carried out in the growing and wintering seasons from 27th May 2009 to 27th May 2010 for a year in Kibana Field, University of Miyazaki, in southern Kyushu, Japan which was located on andosols at 31 m above sea level (31°50'N and 131°25'E).

Image for - Variation in Growth Attributes, Dry Matter Yield and Quality Among 6 Genotypes of Napier Grass used for Biomass in Year of Establishment in Southern Kyushu, Japan
Fig. 1: Monthly rainfall (mm) and monthly mean of the daily mean, minimum and maximum temperatures (°C) in 2009-2010 (current) and in the 30-year average for 1980-2010 (average), Source: JMA, 2010

The temperature and rainfall data as shown in Fig. 1 were monitored from the Miyazaki Meteorological Observatory in addition to obtaining data on the 30 year average for 1980-2010 (JMA, 2010).

Treatments and design: Plots were arranged by a randomized complete design with 3 replications (main plots) and each subplot (genotype) having 4 rows 4 m longx5 m wide, with 1 m spacing between subplots and 2 m spacing between main plots. Genotypes of napier grass were selected having a wide range of phenotypic variation, such as a dwarf variety of an early-heading type (DE), a dwarf variety of a late-heading type (DL), a hybrid of pearl millet with napier grass (HY), a Purple-foliage type (PF) and the normal varieties of Merkeron (ME) and Wruk wona (WK). Plants were transplanted at a density of 2 plants m-2 on 27th May 2009 using nursery stock obtained from stem cuttings in the field-grown plants and had been grown in a glasshouse since November 2008. Plots were rain-fed and weeding was conducted by hand two times, on 16th June and 3rd July 2009. Basal fertilizer was supplied in the form of fermented cattle manure and dolomite at 400 and 20 g m-2, respectively, on 20th May 2009 and additional fertilizer was supplied in the form of a chemical compound fertilizer at the rate of 55 g N, P2O5 and K2O, each m-2 year-1 by 7 split applications on 27th May, 3rd June, 24th June, 8th July, 22nd July, 21st August and 14th September 2009.

Growth characteristics: Ten plants were measured for growth attributes such as plant height, plant length and tiller number in each subplot with 3 replications. Two mature stalks were harvested manually from each subplot, using a sickle to cut them at a height of 10 cm above the ground level, on 10th November 2009 to obtain samples for measurement of Fresh Weight (FW). Leaf area was measured with an AAM-8 automatic area meter (Hayashi Denkoh Co. Ltd., Tokyo, Japan) to calculate the Leaf Area Index (LAI). Subsampled (ss) herbage at around 400 g of FW was hand-separated into Leaf Blades (LB), stems inclusive of Leaf Sheath (ST) and dead leaves (D) and dried in a forced-air oven at 70°C to measure Dry Weight (DW). The overwintering ability was determined by the Percentage of Overwintered Plants (POP) and Regrowing Tiller Number (RTN) for all plants excluding border plants on 27 May 2010. The POP was calculated as the number of plants that emerged one or more regrowing tillers divided by the total number of plants and RTN was calculated by multiplying plant tiller number by plant density.

DM yield: The DM yield was calculated according to Tarawali et al. (1995) as follows:

Image for - Variation in Growth Attributes, Dry Matter Yield and Quality Among 6 Genotypes of Napier Grass used for Biomass in Year of Establishment in Southern Kyushu, Japan

Where:    
Tot FW = Total fresh weight (g m-2)
DWss = Dry weight of the subsample (g)
FWss = Fresh weight of the subsample (g)

Chemical analyses of cell wall components and in vitro dry matter digestibility (IVDMD): Samples were ground by mill (Model D3V-10, Hsiangtai Machinery Industry Co. Ltd., Taipei, Taiwan) to pass through a 1 mm mesh and were analyzed in duplicate samples for IVDMD, Neutral Detergent Fiber (NDF), Acid Detergent Fiber (ADF) and Acid Detergent Lignin (ADL) content using a detergent digestion protocol as described by Vogel et al. (1999). Samples were placed in preweighed bags and processed by a fiber extraction protocol (Vogel et al., 1999) and the ANKOM procedure (ANKOM 220 Fiber Analyzer, Model 220v; ANKOM Technology Corp., Fairport, NY, USA). These procedures estimate NDF, ADF and ADL contents. The content of cell wall components, namely hemicelluloses and cellulose, was calculated using component concentrations expressed on a dry weight basis, as follows:

On an oven-dry weight basis (g kg-1)
Hemicelluloses = NDF-ADF
Cellulose = ADF-ADL; (Jung and Vogel, 1992)
IVDMD content was determined by the pepsin-cellulase digestion method (Goto and Minson, 1977)

Estimation of ethanol production: The conversion efficiencies from Badger (2002) were adopted to estimate ethanol production potential from 6 genotypes of napier grass as listed in Table 1. Then the ethanol yield summed up from both cellulose and hemicelluloses was converted from kg ha-1 year-1 to L ha-1 year-1 by multiplying by 1.1527.

Table 1: Ethanol conversion efficiencies, assumed after Badger (2002)
Image for - Variation in Growth Attributes, Dry Matter Yield and Quality Among 6 Genotypes of Napier Grass used for Biomass in Year of Establishment in Southern Kyushu, Japan

Statistical analysis: Analysis of variance (ANOVA) was carried out using SPSS software (version 15.0) by one-way analysis procedures for growth attributes, DM yield, chemical components and IVDMD of napier grass in a randomized complete design. Mean separation was tested using the Least Significance Difference (LSD) method at the 5% level. Pearson correlation coefficients were calculated among growth attributes, DM yield, cell wall components, IVDMD and ethanol production potential using data from all genotypes (for each parameter, n = 36 except for LAI, n = 18). Correlation coefficients were considered high for r = 0.75, moderate for r = 0.50-0.75 and low for r<0.50. Multiple regression analyses by stepwise and forward selection and by stepwise and backward selection were performed for ethanol production potential (n = 36), where variables (predictors) were chemical composition and digestibility such as IVDMD, NDF, ADF and ADL content of LB and ST and the dependent variable was ethanol production potential; determination of variables was based on the significance of the standardized partial regression coefficient based on the t-value at the 5% level.

RESULTS AND DISCUSSION

Climatic conditions: Changes in the monthly mean, minimum and maximum air temperatures and precipitation in the growing season showed that even though the current maximum and minimum temperatures were slightly higher than those in an average year, temperatures were not significantly different from those in an average year (Fig. 1). Precipitations in May-July 2009 were lower than the average rainfall, in contrast to a higher level than average in November 2009. Temperatures in the wintering season were slightly higher than average in January-March and rainfall was slightly higher than average in February-April 2010.

Growth attributes and DM yield: Values for the mean and standard deviation of growth attributes and yield at harvest in November 2009 (Table 2) showed that the HY and DE and the normal varieties of WK and ME had similar values for each attribute and yield, except for the highest plant height and DM yield and the lowest tiller number in WK among genotypes while DL and PF tended to have lower values than the other 4 genotypes, except for the highest tiller number and LAI in DL among the 6 genotypes. We estimated the correlation between lowest plant height in DL with highest tiller number and LAI from the largest amount of leafage in DL. Even though DE had lower plant height up to August than normal varieties (data not shown), the stem elongation triggered by floral induction in this genotype led to increasing plant height and yield components similar to other normal varieties such as WK and ME and HY at harvest in November. In contrast, PF had the lowest LAI, even falling in the middle rank of plant height which correlated with the lowest rank of yield components as well as DL. Therefore, fresh and DM yield among genotypes ranged from 90.1 to 156.7 and 13.4 to 33.5 Mg ha-1, respectively, where WK was the highest yielder for both fresh and DM, followed by ME. The current study was in agreement with Utamy et al. (2009), who reported a similar DM yield for DL, the highest yielding variety at 13.6 Mg ha-1 among several sites in the year of establishment. Rajvanshi and Nimbkhar, 2008 also determined DM yield for HY as 24-40 Mg ha-1 in India. Anderson et al. (2008) reviewed the DM productivity of ME in the South of the United States at 27.76 Mg ha-1 in Georgia, 30-60 Mg ha-1 in southern and central Florida and 20-30 Mg ha-1 in the northern part of the region. However, HY has some variation in genotype which showed yields of 10-18 Mg DM ha-1 in a warm temperate climate being affected by planting density in Australia (Pearson and Anthony, 1977).

Table 2: Effects of genotypes on agronomic attributes and chemical compositions of napier grass genotypes in November of the year of establishment
Image for - Variation in Growth Attributes, Dry Matter Yield and Quality Among 6 Genotypes of Napier Grass used for Biomass in Year of Establishment in Southern Kyushu, Japan
Mean±Standard deviation, Agronomic attribute: PH: Plant height, TN: Tiller number, LAI: Leaf area index, DMY: Dry matter yield, PST: Percentage of stem inclusive of leaf sheath to total dry weight, Pdd: Percentage of dead leaves to total dry weight. Chemical composition: ADL: Acid detergent lignin, IVDMD: In vitro dry matter digestibility, LB: Leaf blade, ST: Stem inclusive of leaf sheath. Genotype: DE: Dwarf variety of early-heading type, DL: Dwarf variety of late-heading type, HY: Hybrid of pearl millet with napier grass, PF: Purple-foliage type, ME: Normal varieties of Merkeron and WK: Wruk wona. *, p<0.05; ns, not significant (p>0.05), Values with different superscripts in the same column differ significantly by LSD method (p<0.05), ‡ Significance at 5% level by ANOVA

The LAI values ranging from 2.5 to 8.5 were in a good agreement with research carried out for DE, DL, ME and WK in Miyazaki (Mukhtar et al., 2003) and ME in Fukuoka (Kubota et al., 1994) in Kyushu, Japan.

Biomass quality: Values for mean and standard deviation of chemical composition of both LB and ST at harvest in November 2009 (Table 2) showed that the composition of several components of LB, such as hemicelluloses, cellulose content and IVDMD in LB, were not significantly different among the 6 genotypes. In contrast, in ST, cellulose, ADL content and IVDMD in ST were significantly different among the same genotypes, where DL had the lowest cellulose and ADL content and the highest IVDMD at 65.8% and DE had the highest cellulose content at 43.6% in ST.

Correlation analysis of growth attributes, yield and chemical compositions: Correlation coefficients of growth attributes, yield and chemical composition of both LB and ST among the 6 genotypes (Table 3) showed that plant height was positively correlated (p<0.01) with DM yield, hemicellulose content in LB and cellulose and ADL content in ST, influenced by the lower values of these attributes in DL and of DM yield in PF. Tiller number was negatively correlated (p<0.01) with percentage of stem to total dry weight (PST), influenced by the lowest value in DL. The DM yield was positively correlated with PST and negatively correlated with tiller number, ADL content in LB and IVDMD in ST and was influenced by the lowest PST and the highest ST-IVDMD in DL.

Table 3: Correlation coefficients of agronomic attributes and chemical compositions with ethanol production potential of six napier grass genotypes in the year of establishment
Image for - Variation in Growth Attributes, Dry Matter Yield and Quality Among 6 Genotypes of Napier Grass used for Biomass in Year of Establishment in Southern Kyushu, Japan
Agronomic attribute: PH: Plant height, TN: Tiller number, LAI: Leaf area index, PST: Percentage of stem to total dry weight, DMY: Dry matter yield. Chemical composition: LB-Hemi: Hemicelluloses content in leaf blade, ST-Hemi: Hemicelluloses content in stem inclusive of leaf sheath, LB-Cellu: Cellulose content in leaf blade, ST-Cellu: Cellulose content in stem inclusive leaf sheath, IVDMD: In vitro dry matter digestibility, LB-IVDMD: IVDMD in leaf blade, ST-IVDMD: IVDMD in stem inclusive leaf sheath, ADL: Acid detergent lignin, LB-ADL: ADL content in leaf blade, ST-ADL: ADL content in stem inclusive leaf sheath, *Significant at p<0.05, **Significant at p<0.01 by Pearson correlation analysis (n = 36, except for LAI, n = 18), ns: Not significant at p>0.05

PST was a good indicator for chemical composition, since it was positively correlated (p<0.01) with cellulose and ADL content in ST and negatively correlated (p<0.01) with ST-IVDMD which was influenced by the lowest values of PST and cellulose and ADL content in ST and the highest values of ST-IVDMD in DL.

Ethanol production potential and future perspective: Significant differences in ethanol production potential of the 6 napier grass genotypes were detected from both LB and ST in the range 1826-5850 L ha-1 year-1 (Fig. 2), where ME and WK were the highest producers of both tissues, followed by DE and HY and the lowest in PF and DL among genotypes.

If we could grow the highest potential genotype of ME in the whole area of abandoned cropland, a total of 386,000 ha in Japan (Matsumoto et al., 2009), then ethanol production is expected to reach 2.258 millions kL year-1 which equals 53.96 PJ of energy potential, corresponding to the target energy potential of domestic biofuel from herbage at 1.8-2.0 millions kL year-1 in 2030 (MAFF, 2007; Tanaka, 2007). Our estimates of ethanol production could increase by achieving an optimized composition of structural carbohydrates (hemicelluloses and cellulose) by improved agronomic practices (Schmer et al., 2008) and by optimizing the efficiency of hydrolysis and fermentation to more than 90% (Gunasekaran and Chandra Raj, 1999).

We examined these 6 genotypes in southern Kyushu using the Percentage of Overwintered Plants (POP) and Regrown Tiller Number (RTN) as indices of sustainability on 27 May 2010 (Table 4). Based on these results which are derived from overwintering ability only after the first year following establishment, it is difficult to accurately predict the sustainability of genotypes; however, POP was lower (p<0.05) in PF than the other 4 genotypes except for DE and RTN significantly differed (p<0.05) among genotypes, being the highest in DL, followed by DE, HY and ME and WK and PF.

Image for - Variation in Growth Attributes, Dry Matter Yield and Quality Among 6 Genotypes of Napier Grass used for Biomass in Year of Establishment in Southern Kyushu, Japan
Fig. 2: Ethanol production potential in 6 genotypes of napier grass in the year of establishment Genotype: DE: Dwarf variety of early-heading type, DL: Dwarf variety of late-heading type, HY: Hybrid of pearl millet with napier grass, PF: Purple-foliage type and ME: Normal varieties of Merkeron and WK: Wruk wona; LB: Leaf blade; ST: Stem inclusive of leaf sheath. Values with different superscripts in each plant tissue differed significantly among genotypes by the LSD method (p<0.05)

Table 4: Percentage of overwintered plants and regrown tiller number of napier grass genotypes in May 2010
Image for - Variation in Growth Attributes, Dry Matter Yield and Quality Among 6 Genotypes of Napier Grass used for Biomass in Year of Establishment in Southern Kyushu, Japan
Genotype: DE: Dwarf variety of early-heading type, DL: Dwarf variety of late-heading type, HY: Hybrid of pearl millet with napier grass, PF: Purple-foliage type, ME: Normal varieties of Merkeron and WK: Wruk wona, POP: Percentage of overwintered plants, RTN: Regrown tiller number, Mean±Standard deviation; Values with different superscripts in the same column differ significantly (p<0.05) by LSD method, *Significance at 5% level by ANOVA

However, the overwintering ability was affected by the temperature conditions in the wintering season (Ishii et al., 2000) and the current study period of January-March 2010 had higher temperatures than the average over the past 30 years. Therefore, we need to monitor the sustainability of 6 genotypes in subsequent years.

Multiple regression analysis: Multiple regression analyses for ethanol production potential showed that in stepwise and forward selection, NDF content in ST (X1) and ADL content in LB (X2) could be used as variables to estimate ethanol production potential (Y) as follows:

Y = 1012.6+129.4 X1-406.6 X2, adjusted R2 = 0.489 (p<0.01), SSE = 1181.91

Anderson et al. (2010) demonstrated that NDF content is also the best predictor among cell wall components to estimate ethanol production in bermuda grass (Cynodon dactylon). However, stepwise and backward selection showed that predictors could be ADL content in LB (X1) and in ST (X2), estimating ethanol production potential (Y) as follows:

Y = 2306.9-450.9 X1+795.5 X2, adjusted R2 = 0.467 (p<0.01), SSE = 1207.3

Isci et al. (2008) also pointed out that ADL content could be the sole predictor to estimate ethanol yield from corn stover samples which is in a good agreement with our analysis.

CONCLUSION

We found that napier grass has a wide range of genotypic variation in DM yield, structural carbohydrate content and digestibility which results in variation of ethanol production potential among genotypes. The normal variety of ME was identified as the most promising genotype to produce bioethanol from napier grass, with a yield of 5850 L ha-1 year-1 in the year of establishment in southern Kyushu under the assumption of theoretical conversion efficiency of 0.29 and 0.23 from cellulose and hemicelluloses, respectively.

REFERENCES

1:  Anderson, W.F., B.S. Dien, S.K. Brandon and J.D. Peterson, 2008. Assessment of bermudagrass and bunch grasses as feedstock for conversion to ethanol. Applied Biochem. Biotechnol., 145: 13-21.
CrossRef  |  PubMed  |  Direct Link  |  

2:  Anderson, W.F., B.S. Dien, H.J.G. Jung, K.P. Vogel and P.J. Weimer, 2010. Effects of forage quality and cell wall constituents of Bermuda grass on biochemical conversion to ethanol. Bioenerg. Res., 3: 225-237.
CrossRef  |  

3:  Badger, P.C., 2002. Ethanol from Cellulose: A General Review. In: Trends in New Crops and New Uses, Janick, J. and A. Whipkey, (Eds.). ASHS Press, Virginia, USA., pp: 7-21

4:  Boonman, J.G., 1993. Elephantgrass Husbandry. In: East Africa's Grasses and Fodders: Their Ecology and Husbandry, Boonman, J.G. (Ed.). Kluwer Academic Publisher, Netherlands, pp: 235-257

5:  Chaparro, C.J., L.E. Sollenberger and C.S. Jones Jr., 1995. Defoliation Effects on `Mott` Elephantgrass Productivity and Leaf Percentage. Agron. J., 1995: 981-985.
Direct Link  |  

6:  Chaparro, C.J., L.E. Sollenberger and K.H. Quesenberry, 1996. Light interception, reserve status and persistence of clipped Mott elephantgrass swards. Crop Sci., 36: 649-655.
Direct Link  |  

7:  Cuomo, G.J., D.C. Blouin and J.F. Beatty, 1996. Forage potential of dwarf napiergrass and a pearl millet x napiergrass hybrid. Agron. J., 88: 434-438.
Direct Link  |  

8:  Ferraris, R., 1980. Effect of harvest interval, nitrogen rates and application times on Pennisetum purpureum grown as an agroindustrial crop. Field Crops Res., 3: 109-120.
CrossRef  |  

9:  Goto, I. and D.J. Minson, 1977. Prediction of the dry matter digestibility of tropical grasses using a pepsin-cellulase assay. Anim. Feed Sci. Technol., 2: 247-253.
CrossRef  |  Direct Link  |  

10:  Gunasekaran, P. and K. Chandra Raj, 1999. Ethanol fermentation technology-Zymomonas mobilis (Review). Curr. Sci., 77: 56-68.

11:  Humphreys, L.R., 1994. Tropical Forage: Their Role in Sustainable Agriculture. Harlow, Longman, UK

12:  Isci, A., P.T. Murphy, R.P. Anex and K.J. Moore, 2008. A rapid Simultaneous Saccharification and Fermentation (SSF) technique to determine ethanol yields. Bioenerg. Res., 1: 163-169.
CrossRef  |  

13:  Ishii, Y., K. Ito and K. Fukuyama, 2000. Effect of several cultivation factors on the overwintering ability of napiergrass in southern Kyushu. Jpn. J. Crop Sci., 69: 209-216.
Direct Link  |  

14:  Ishii, Y., K. Ito and H. Numaguchi, 1995. Effects of cutting date and cutting height before overwintering on the spring regrowth of summer-planted napiergrass (Pennisetum purpureum Schum). J. Jpn. Grassland Sci., 40: 396-409.

15:  Ishii, Y., M. Mukhtar, S. Idota and K. Fukuyama, 2005. Rotational grazing system for beef cows on dwarf napiergrass pasture oversown with Italian ryegrass for 2 years after establishment. Grassland Sci., 51: 223-234.
CrossRef  |  

16:  Ito, K. and S. Inanaga, 1988. Studies on dry matter production of napiergrass, 1: Comparison of dry matter productivities and growth parameters between Tokyo and Miyazaki. Jpn. J. Crop Sci., 57: 90-96.
Direct Link  |  

17:  Ito, K., Y. Murata, S. Inanaga, T. Ohkubo and T. Takeda et al., 1988. Studies on dry matter production of napiergrass. II. Dry matter productivities at six sites in southern area of Japan. Jpn. J. Crop Sci., 57: 424-430.
Direct Link  |  

18:  JMA, 2010. Previous climatic data. Japan Meteorological Agency.

19:  Jung, H.J., K.P. Vogel, 1992. Lignification of switchgrass (Panicum virgatum) and big bluestem (Andropogon gerardi) plant parts during maturation and its effect on fiber degradability. J. Food Sci. Agric., 59: 169-176.
CrossRef  |  

20:  Kai, T., T. Tanimura, N. Nozaki, M. Suiko and K. Ogawa, 2010. Bioconversion of soft cellulosic resources into sugar and ethanol. Seibutsu-kogaku Kaishi, 88: 66-72.
Direct Link  |  

21:  Kubota, F., Y. Matsuda, W. Agata and K. Nada, 1994. The relationship between canopy structure and high productivity in napier grass, Pennisetum purpureum Schumach. Field Crops Res., 38: 105-110.
CrossRef  |  

22:  Lemus, R., E.C. Brummer, K.J. Moore, N.E. Molstad, C.L. Burras and M.F. Barker, 2002. Biomass yield and quality of 20 switchgrass populations in southern Iowa, USA. Biomass Bioenergy, 23: 433-442.
CrossRef  |  

23:  Maeda, S., 2007. Research and development trends in energy crops and biofuel conversion technologies. Science and Technology Trends, Japan. http://www.nistep.go.jp/achiev/ftx/eng/stfc/stt025e/qr25pdf/STTqr2504.pdf.

24:  MAFF, 2007. The biomass Japan comprehensive strategy promotion council. Prime Minister's Report, The Ministry of Agriculture, Forestry and Fisheries (MAFF), Tokyo.

25:  Matsumoto, N., D. Sano and M. Elder, 2009. Biofuel initiatives in Japan: Strategies, policies and future potential. Applied Energy, 86: S69-S76.
CrossRef  |  

26:  McKendry, P., 2002. Energy production from biomass (part 1): Overview of biomass. Bioresour. Technol., 83: 37-46.
CrossRef  |  

27:  Mielenz, J.R., 1997. Feasibility studies for biomass-to-ethanol production facilities in Florida and Hawaii. Renewable Energy, 10: 279-284.

28:  Mukhtar, M., Y. Ishii, S. Tudsri, S. Idota and T. Sonoda, 2003. Dry matter productivity and overwintering ability of the dwarf and normal napiergrasses as affected by the planting density and cutting frequency. Plant Prod. Sci., 6: 65-73.
CrossRef  |  Direct Link  |  

29:  Pearson, C.J. and D.T.W. Anthony, 1977. Hybrid pennisetum in a warm temperate climate: Effects of plant density on summer production. Austr. J. Exp. Agric. Anim. Husbandry, 17: 284-289.
CrossRef  |  Direct Link  |  

30:  Rajvanshi, A.K. and N. Nimbkhar, 2008. Sweet sorghum R and D at the Nimbkar Agricultural Research Institute (NARI). Nimbkar Agricultural Research Institute (NARI), Maharashtra, India. http://www.nariphaltan.org/sorghum.pdf.

31:  Schank, S.C., D.P. Chynoweth, C.E. Turick and P.E. Mendoza, 1993. Napier grass genotype and plant parts for biomass energy. Biomass Bioenergy, 4: 1-7.
Direct Link  |  

32:  Schmer, M.R., K.P. Vogel, R.B. Mitchell and R.K. Perrin, 2008. Net energy of cellulosic ethanol from switchgrass. Proc. Natl. Acad. Sci. USA, 105: 464-469.
CrossRef  |  Direct Link  |  

33:  Schreuder, R., P.J.M. Snijders, A.P. Wouters, A. Steg and J.N. Kariuki, 1993. Variation in OM digestibility, CP, yield and ash content of Napier grass (Pennisetum purpureum) and their prediction from chemical and environmental factors. Research Report, National Animal Husbandry Research Station, Naivasha, Kenya, pp: 1-62.

34:  Skerman, P.J. and F. Riveros, 1990. Tropical Grasses. Food and Agriculture Organization, Rome, Italy, ISBN: 9789251011287, Pages: 832

35:  Tanaka, R., 2007. Biofuels in Japan. Science and Innovation Section, British Embassy Tokyo.

36:  Tarawali, S.A., G. Tarawali, A. Larbi and J. Hanson, 1995. Methods of Evaluation of Forage Legumes, Grasses and Fodder Trees for use as Livestock Feed. ILRI, Nairobi, pp: 51
Direct Link  |  

37:  Utamy, R.F., Y. Ishii, A. Wadi, S. Idota, N. Harada and K. Fukuyama, 2009. Adaptibility and sustainability of DL napiergrass under cut-and-carry and grazing systems for small holder farmers in southern Kyushu Japan. Proceedings of the 3rd Korea-China-Japan Joint Symposium on Grassland Agriculture and Livestock Production, August 10-14, 2009, Konkuk University, Seoul, Korea, pp: 62-63

38:  Vicente-Chandler, J., S. Silva and J. Figarella, 1959. The effect of nitrogen fertilization and frequency of cutting on the yield and composition of three tropical grasses. Agron. J., 51: 202-206.
Direct Link  |  

39:  Vogel, K.P., J.F. Pedersen, S.D. Masterson and J.J. Toy, 1999. Evaluation of a filter bag system for NDF, ADF and IVDMD forage analysis. Crop Sci., 39: 276-279.
Direct Link  |  

40:  Woodard, K.R. and G.M. Prine, 1993. Dry matter accumulation of elephantgrass, energycane and elephantmillet in the subtropical climate. Crop Sci., 33: 818-824.
Direct Link  |  

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