EAEF 3(1) : 32-37, 2010

Research Paper

Investigation into Possible Use of Methane Fermentation Digested Sludge

as Liquid Fertilizer for Paddy Fields *

Chanseok RYU*1, Masahiko SUGURI*2, Michihisa IIDA*2, Mikio UMEDA*3

Abstract

Difference in vegetation growth, taste properties, and grain yield between liquid fertilizer (LF) and chemical fertilizer (CF) applied fields were identified and analyzed to promote the use of the methane fermentation digested sludge as LF using precision agriculture technology. Vegetation growth and these ratios of LF to CF were different at panicle initiation and heading stages but no significant difference in nitrogen content was at the heading stage. Dry mass is greater in CF fields and nitrogen concentration is higher in LF fields is confirmed. In spite of no topdressing in 2006, differences in vegetation growth ratios were decreased because of the organic nitrogen in LF. Difference in GreenNDVI was decreased at the heading stage but the pattern was not changed. Differences in taste properties were significant in 2006 but not in 2005. When grain yield would be decreased 25% by hulls, brown rice yield of LF fields in 2005 was 93% of the average amount in the region (510 kg/10a) and 84% of that (505 kg/10a) in 2006.

[Keywords] liquid fertilizer, precision agriculture, vegetation growth, GreenNDVI, taste properties, grains yield

I Introduction

Food, energy, and environment are important for a sustainable world. It is necessary to maintain or increase the production of food using as little energy as possible to preserve the environment (Umeda, 2004). The ratio of total greenhouse gases from the agriculture sector to those from all the sectors is 2.6% in Japan. However, the ratios of total CH4 and total N2O emissions are high as 69.7% and 57.2%, respectively. It is suggested that the way of reducing CH4 and N2O emission at agriculture sections are water management, recycling of biomass, reducing the amount of nitrogen fertilizer, no-tillage (Nouchi, 2006). In Japan, 72% of concentrated feed and 22% of roughage are imported from abroad and 1.24 million tons of nitrogen is disposed and discharged annually (Agriculture white paper, 2000). Therefore, it is important to increase the amount of nitrogen recycled in domestic level toward a sustainable world. There are several ways to increase biomass utilization, such as gasification, composting, methane fermentation, and extraction of ethanol (Biomass Nippon Strategy, 2006).

Methane fermentation of animal wastes is attracting considerable attention not only for waste management but also in terms of production of both energy and liquid fertilizer (LF) (Haga et al., 1979). Yagi Bio-Ecology Center (YBEC) is a methane fermentation plant that has been involved in livestock waste treatment and food production since 1998. It is possible to generate electricity by biogas and to get hot water from the radiator of generator. Methane fermentation digested sludge is discharged into a river after subjecting it to chemical, which accounts for 40% of the total expenditure incurred in waste management (Ogawa et al., 2003).

Therefore, the application of methane fermentation digested sludge as LF to paddy fields has been suggested because rice is entirely cultivated in Japan. In a previous study, no significant difference in vegetation growth was identified between small plots that received LF and chemical fertilizer (CF) (Li et al., 2003). Therefore, it is necessary to identify, analyze, and manage spatial and temporal variability in a field and within fields using the technology of precision agriculture (Umeda et al., 1999) in order to spread out LF evenly. We have previously reported differences in nitrogen content at the panicle initiation stage in 2005 but not in 2004. At the heading stage, however, the differences decreased compared to that seen in the panicle initiation stage. Weather conditions, soil properties, and nitrogen discharge might be causing these differences (Ryu et al., 2007).

The objectives of this study are 1) to identify the differences in vegetation growth, rice taste, and grain yield between LF and CF fields using precision agriculture technology, 2) to analyze these data in several conditions to promote the use of methane fermentation digested sludge as liquid fertilizer.

* Presented at the 2nd Asian Conference on Precision Agriculture in August 2007*1 JSAM & KSAM Member, Corresponding author, Graduate School of Agriculture Kyoto University, ShirakawaOiwake-Cho, Sakyo-Ku, Kyoto, 606-8502, Japan; ryu@elam.kais.kyoto-u.ac.jp*2 JSAM Member, Graduate School of Agriculture Kyoto University, ShirakawaOiwake-Cho, Sakyo-Ku, Kyoto, 606-8502, Japan *3 JSAM & KSAM Member, Kyoto University, Yoshida Hon-machi, Sakyo-ku, Kyoto, 606-8501, JapanRYU, SUGURI, IIDA, UMEDA:33

Investigation into Possible Use of Methane Fermentation Digested Sludge as Liquid Fertilizer for Paddy Fields

Materials and Methods

Test fields

The test fields are located in Hidokoro district, Yagi town, Nantan city, Kyoto prefecture, Japan (13554E, 3509N and 120 m above sea level). The species of the test crop was

Oryza sativa L., cv. KINU-HIKARI. In 2006, one of the CF fields was changed. Two LF fields were managed by a guild, and two CF fields were managed personally. The soil type in field 1, 2 and 3 was silty clay and that in field 4 was light clay. But it was failed to analyze the soil type in field 3 in 2006.

Fertilizer application

Generally, LF consists of NH4 and organic nitrogen. The ratio of these components varied according to the materials added to the methane fermentation tank. The ratio of NH4 to total nitrogen in LF was 1650 / 3100 ppm in 2005, and 1683 / 4778 ppm in 2006. The amount of nitrogen fertilizer applied to LF fields was calculated based on the amount of NH4, because it is difficult to predict the amount of mineralized nitrogen (Nakamura et al., 2007). LF was applied with irrigation water at 7.6 tons per hour at basal dressing. Then, puddling was performed to spread LF as uniformly as possible. At topdressing, the speed of application was decreased to 3.4 tons per hour, because it was impossible to perform puddling. In CF fields, NK fertilizer (17% N and 17% K2O) was applied at basal dressing and topdressing while P fertilizer (17.5% P2O5) was applied at basal dressing.

Table 1 shows the management date and items for the test fields in 2005 and 2006. It was possible to control the management date in 2005 but not in 2006. It was impossible to apply topdressing in LF fields in 2006 because vegetation growth at the panicle initiation stage was inadequate.

Tabel 1. Management date and items for test fields in 2005 and 2006

(Soil type)AreaBasal*1T*4Middle*5Topdressing

S*6H*7

[ha]D*2N*3

DNDNDN

10.385/27355/306/27187/2618

9/99/20

LF0.335/27355/306/27207/2620

9/99/20

2

2005

0.415/26105/286/14147/27258/3259/99/16

3*8

CF0.305/26245/28

7/1611

9/99/18

4

10.386/3636/10

9/129/17

LF0.336/3596/10

9/129/21

2

2006

0.415/22415/246/7157/15257/25219/129/17

3*8

CF0.305/25365/25

7/1617

9/129/20

4

(1: Basal dressing, 2: Date, 3: Amount of nitrogen fertilizer [kg/ha], 4: Date of transplanting, 5: Fertilizer application between basal dressing and topdressing, 6:

Date of sampling for rice taste, 7: Date of harvesting, 8: Field was different in 2005 and 2006) 3. Vegetation growth

Vegetation growth at panicle initiation and heading stages was investigated in nine sampling points in each field and six stocks of rice plants at each point. These were separated into leaves and stems at the panicle initiation stage and into leaves, stems and ears at the heading stage. The separated parts of each sample were dried using a circulation drier at 80 for more than 72 hours and then weighed. The nitrogen concentration of the finely ground leaves and stems was measured three times for each sample with gas chromatography NC-900 (Sumica Chemical Analysis Service, Japan). Nitrogen content was calculated by multiplying the dry mass and nitrogen concentration.

Spatial variability of vegetation growth at each field was described by GreenNDVI, which has a relation with nitrogen content at vegetation growth stage and protein contents at ripening stage, as shown at equation (1).

GreenNDVI =(DN860 DN560 )(1)

(DN860+ DN560 )

where, DN860 and DN560 represent the digital number for near infrared (835~885 nm) and green (535~585 nm) of airborne digital sensor ADS40 (Leica Geosystems, USA). The images were taken on July 20, August 5, and September 2, in 2005, and on August 13, and September 9 in 2006 (Pasco Co., Japan).

Rice taste and grains yield

About one week before harvesting, six to eight stocks of rice plants were harvested at each sampling point. The samples were threshed and dried to about 15% of moisture content. Grains were then husked to brown rice and sorted using a 1.9 mm of mesh. Depending on the amount of brown rice, each sample was separated into two or three parts with 200 mL and then these were measured by the rice grain taste analyzer, RCTA11A (Satake Co., Japan). Rice taste, protein, amylose (amylopectin), fatty acid, and moisture content were obtained by calculating the average value of two or three of measurements (Ryu et al. 2004).

The spatial variability of grains yield in each field was estimated by yield monitoring combine with RTK-DGPS (Trimble MS750, USA), with an accuracy of 2cm. Grains yield was calculated based on the amount of grains and not that of brown rice. Moisture content was measured by the single kernel moisture contents analyzer CTR-800E (Shizuoka Seiki Co, Japan). The grains yield maps was constructed using the kriging method with GS+ software (Gamma Design Software, USA) (Iida et al., 2004).34Engineering in Agriculture, Environment and Food Vol. 3, No. 1 (2010)

Results and Discussions

Vegetation growths

Panicle initiation stage

Vegetation growth at panicle initiation stage was measured on July 21 in 2005 and July 24 in 2006. Table 2 shows the descriptive statistics of vegetation growth in 2005 and 2006. The differences in vegetation growth between LF and CF fields were significant with 5 % of level. Differences in that in LF fields between 2005 and 2006 were also significant. While dry mass ratios and nitrogen contents ratios of LF to CF fields were greater than 0.6 in 2005, they were less than 0.5 in 2006. The similar trend that dry mass is greater in CF fields and nitrogen concentration is higher in LF fields (Ryu et al., 2007) was confirmed in this study. In spite of the similar field management in 2005, vegetation growths in LF fields had a different tendency from that in CF fields. Nitrogen concentration ratios of LF to CF fields in 2006 were higher than these in 2005. It might be influenced by the insufficiency of dry mass. Moreover, first topdressing in CF fields was applied few days before sampling, except for field 3 in 2005.

Table 2 Descriptive statistics of vegetation growth data at panicle initiation stage in 2005 and 2006

Panicle initiationD1 [kg/m2]NC2 [%]N3 [kg/m2]

(Date of sampling)LeafStemTotalLeafStemLeafStemTotal

Mean1481603083.311.194.881.906.79

LF9.0910.39.545.458.198.959.739.06

2005CV4

Mean200*+259*+459*+2.95*+1.15+5.88*+2.90*+8.78*+

(7/21)

CF8.6313.410.911.326.89.8218.1412.2

CV

Ratio L/C0.740.620.671.121.040.830.660.77

Mean59.0*43.0*102*4.13*2.03*2.42*0.8*83.29*

LF23.326.519.54.376.3323.626.720.0

2006CV

Mean160+#174+#334+#3.08*+1.34*#+4.92+#2.31+#7.23+#

(7/24)

CF27.121.423.27.006.1826.317.922.4

CV

Ratio L/C0.370.250.301.341.510.490.380.46

(1: Dry mass, 2: nitrogen concentration, 3: nitrogen content, 4: coefficient of variation [%], Ratio L/C: the ratio for vegetation growth of LF to CF, *: vs. LF 2005, +: vs. LF 2006, #: vs. CF 2005 with 5% significant level)

Fig. 1 shows the differences of weather conditions between 2005 and 2006. Weather condition, especially the accumulated radiation, in 2005 was better than that in 2006. The difference in the accumulated temperature and radiation hours between LF and CF fields were 7 and 13 hours in 2005, but 70 and 55 hours in 2006. It was difficult to determine the reason of the difference in vegetation growth between 2005 and 2006 because field management and weather conditions influence vegetation growth.

Fig. 1 Weather conditions in 2005 and 2006

Fig. 2 shows the GreenNDVI maps taken of the test fields at the panicle initiation stage on July 20 in 2005. Nitrogen content in CF fields was higher than that in LF field. Nitrogen content in the upper parts of LF fields was higher than that in the lower parts. It was influenced by the total solid content of LF, which was combined with organic nitrogen making it difficult to spread out (Iida et al., 2009). It is necessary to control field management factors, including using consistent ratios of LF to irrigation water or new application methods to apply LF as uniformly as possible.

Fig. 2 GreenNDVI maps at panicle initiation stage in 2005

Heading stage

Except one sample in CF fields in 2005, vegetation growth was investigated on August 9 in 2005 and on August 14 in 2006. Table 3 shows the descriptive statistics of vegetation growth in 2005 and 2006. The differences in dry mass and nitrogen concentration between LF and CF fields were significant with 5% of level, except dry mass of leaves and nitrogen concentration in 2005. However, there were no significant differences in nitrogen content. The differences in vegetation growth in LF fields between 2005 and 2006 were also significant. In 2005, nitrogen content ratios of LF to CF fields were similar to each other, ranging from 0.87 to 1.01.RYU, SUGURI, IIDA, UMEDA:35

Investigation into Possible Use of Methane Fermentation Digested Sludge as Liquid Fertilizer for Paddy Fields

Table 3 Descriptive statistics of vegetation growth data at heading stage in 2005 and 2006

Heading

D*1 [kg/m2]

NC*2 [%]N*3 [kg/m2]

(Date of sampling)LeafStemEarTotalLeafStemLeafStemTotal

Mean191376976713.110.975.973.649.61

LF21.644.010.771.30.350.211.110.871.91

2005CV*4

Mean207+476*+133*+833*+2.830.875.92+4.17+10.1+

(8/9)

CF33.053.314.687.90.350.251.451.312.71

CV

Ratio L/C0.930.790.730.811.101.111.010.870.95

Mean139*252*67*460*2.80*0.79*3.89*2.01*5.90*

LF15.316.618.515.27.7213.017.823.519.1

2006CV

Mean184*+#390+#163*+#751+#2.51*+#0.66*+#4.61*#2.56*#7.17*#

(8/14)

CF12.316.618.113.07.9710.814.117.014.2

CV

Ratio L/C0.760.650.410.611.121.200.840.790.82

(*1: Dry mass, *2: nitrogen concentration, *3: nitrogen contents, *4: coefficient of variation [%], Ratio L/C: the ratio for vegetation growth of LF to CF, *: vs. LF 2005, +: vs. LF 2006, #: vs. CF 2005 with 5% significant level)

Although there were no significant differences in nitrogen contents between LF and CF fields in 2006, those ratios of CF to LF ranged from 0.79 to 0.84. In spite of not performing topdressing, the differences in vegetation growth ratios of LF to CF fields at the heading stage were decreased compared with these at the panicle initiation stage. This suggests that organic nitrogen, which is included at basal dressing and supplied by the soil, supported vegetation growth from panicle initiation to heading stages. The ear dry mass ratios of LF to CF fields were different as 0.73 in 2005 and 0.41 in 2006.

Fig. 3 GreenNDVI maps at heading stage in 2005 and 2006 Fig. 3 shows the GreenNDVI maps taken at the heading stage on August 5 in 2005 and August 13 in 2006. Spatial variability of GreenNDVI between LF and CF fields in 2005 was less than that in 2006. The difference in GreenNDVI between LF and CF fields at the heading stage (Fig. 3) was less than that at the panicle initiation stage (Fig. 2). The pattern of great nitrogen content (higher GreenNDVI) in the upper parts of LF fields was seen at the panicle initiation stage, was also seen at the heading stage. This implies that vegetation growth at the panicle initiation stage influences grows at the heading stage. Therefore, it is important to apply basal dressing uniformly to decrease spatial variability of vegetation growth at the heading stage.

2. Rice taste

Rice taste, amylose, and protein contents were investigated in each field on September 9 in 2005 and on September 12 in 2006. Because the amount of sample was less than 200 mL, three samples in LF fields and one sample in CF fields could not be measured in 2005. Table 4 shows the descriptive statistics of taste properties in 2005 and 2006. Difference in taste properties between LF and CF fields was not significant in 2005 but significant with 5% level in 2006. Spatial variability of taste properties in 2005 was larger than that in 2006. Although the amount of ears in CF fields was greater than that in LF fields, protein content ratios of LF to CF fields were similar to each other. It means that protein content in LF field might be decreased when the amount of ears are increased.

Fig. 4 shows the GreenNDVI maps constructed at the ripening stage on September 2 in 2005 and on September 9 in 2006. GreenNDVI at the ripening stage has a relation with protein contents of grains.

Table 4 Descriptive statistics of taste properties

(Date of sampling)Amylose [%]Protein [%]Taste [Points]

LFMean18.96.5876.9

(n=15)

2005

CV*13.3510.58.94

CFMean18.6+6.37+80.1+

(9/9)

(n=17)CV2.237.045.51

Ratio L/C *21.021.030.96

LFMean19.17.67*75.3

2006(n=18)CV0.993.012.70

CFMean18.7+7.38*+#78.8+

(9/12)

(n=18)CV0.792.472.08

Ratio L/C1.021.040.96

(*1: coefficient of variation [%], *2: the ratio for vegetation growth of LF to CF,

*: vs. LF 2005, +: vs. LF 2006, #: vs. CF 2005 with 5% significant level)36Engineering in Agriculture, Environment and Food Vol. 3, No. 1 (2010)

Fig. 4 GreenNDVI maps at ripening stage in 2005 and 2006

The difference in GreenNDVI between LF and CF fields at the heading stage (Fig. 3) was similar to that at the ripening stage (Fig. 4). It means that the areas where nitrogen content was higher at the heading stage were higher protein content at the ripening stage. Although protein content ratios of LF to CF fields in 2006 were similar to each other as shown at table 4, spatial variability of protein content in LF fields was higher than that in CF fields. Spatial variability of GreenNDVI in 2005 was less than that in 2006, whereas spatial variability of taste properties was larger in 2005 than that in 2006.

3. Grains yield

Grain yield was measured on September 16, 18 and 20 in 2005 and September 17 and 20 in 2006. Table 5 shows the total amounts of applied nitrogen fertilizer and grain yields in 2005 and 2006. Grain yields in 2005 were higher than those in 2006, except in field 4 in 2006. In spite of receiving 1.5 times the total nitrogen fertilizer amount in 2006, grain yield in field 3 was lower than that in the other fields. On the other hand, grain yield in field 4 was better despite having received less nitrogen fertilizer. This could be attributed to compost application in field 4, which was done after harvesting in 2005. The average amounts of brown rice produced Kyoto prefecture were 510 kg/10a in 2005 and 505 kg/10a in 2006 (MAFF of Japan, 2007). When grain yield would be decreased 25% by hulls, brown rice yield in field 4 was only larger than the average amount of that in the region. Table 5 Total amounts of applied nitrogen fertilizer and grain yield in 2005 and 2006

(Date of harvesting)Amount ofAmount ofAmount of

nitrogen fertilizergrains yieldbrown rice yield*

1 (9/20)7.9632474

LF8.5627470

2 (9/20)

2005

3 (9/16)7.4664498

CF3.5667500

4 (9/18)

1 (9/17)6.5574431

LF6.1558419

2 (9/21)

2006

10.2504378

3 (9/17)

CF5.3727545

4 (9/21)

(Unit: [kg/10a], *: Amount of grain yield 0.75)

Brown rice yield in LF fields was 92% ~ 93% of the average amount in 2005. However, in 2006, it was 83% ~ 85% of the average amount of brown rice in the region. It might be influenced by the difference in the amount of ears between LF and CF fields in 2006.

Fig. 5 shows grain yield maps in 2005 and 2006. Grain yield varied spatially not only in LF fields but also in CF fields. In LF fields, areas with higher grain yield were similar in 2005 and 2006. A similar pattern was also found in field 4. This spatial variability of grain yield can be attributed to different soil properties and/or field surface elevation (Yanai et al., 2001).

Fig. 5 Grain yield maps in 2005 and 2006RYU, SUGURI, IIDA, UMEDA:37

Investigation into Possible Use of Methane Fermentation Digested Sludge as Liquid Fertilizer for Paddy Fields

It is necessary to determine the optimal amount of LF to improve grain yield and rice taste. In addition, it is necessary to find the other crops that are suited for Yagi region and absorb nitrogen well in order to promote the methane fermentation digested sludge more widely as liquid fertilizer. Because the amount of LF used in 1 ha of paddy fields is around 45 tons, more than 400 ha of paddy fields are necessary to consume the methane fermentation digested sludge produced by YBEC.

IV Summary and Conclusions

In this research, the difference in vegetation growth, taste properties, and grain yields between LF and CF fields were identified and analyzed to promote the utilization of LF using precision agriculture technology.

There were the differences in vegetation growth at panicle initiation and heading stages between LF and CF fields but there were no significant differences in nitrogen content at the heading stage. Vegetation growth ratios of LF to CF fields were different because of the difference in weather condition between 2005 and 2006. Dry mass is greater in CF fields and nitrogen concentration is higher in LF fields is similar to previous research. In spite of no topdressing in 2006, the differences in vegetation growth ratios of LF to CF fields were decreased because of the organic nitrogen in LF.

The difference in GreenNDVI between LF and CF fields was decreased at the heading stage. However, the pattern of GreenNDVI in the field was not changed. Spatial variability of GreenNDVI in 2005 was less than that in 2006, whereas that of taste properties was larger in 2005 than in 2006. Difference in taste properties between LF and CF fields was not significant in 2005 but significant in 2006. When grain yield would be decreased 25% by hulls, brown rice yield in LF fields was 93% of the average amount in the region (510 kg/10a) in 2005 and about 84% of that (505 kg/10a) in 2006.

It is possible to use the methane fermentation digested sludge as liquid fertilizer for paddy field. However, it is necessary to control field management factors, including using consistent ratios of LF to irrigation water or new application methods to apply LF as uniformly as possible. It is also important to improve grain yield and rice taste.

Acknowledgements

This study was supported by the Ministry of Agriculture, Forestry and Fisheries of Japan under the "Research project for utilizing advanced technologies". In this regard, we would like to express our thanks to Mr. Nakagawa, the head of Agricultural and Forestry Promotion Division, who support the experiment and collect the information of fields. References

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(Received: 5. June. 2009, Accepted: 8. October. 2009)