IJERD – International Journal of Environmental and Rural Development (2013) 4-2

Research article
erd

Effects of Adding Bacillus sp. on Crop Residue Compostingand Enhancing Compost Quality
LIEXIANG LI
Graduate School of Agriculture, Tokyo University of Agriculture, Japan

YUTA ISHIKAWA
Graduate School of Agriculture, Tokyo University of Agriculture, Japan

MACHITO MIHARA*
Faculty of Regional Environment Science, Tokyo University of Agriculture, Japan
Email: m-mihara@nodai.ac.jp
Received 21 December 2012

Accepted 10 June 2013(*Corresponding Author)

Abstract Local farmers tend to burn crop residues to simplify soil preparation for thefollowing season cultivation. Along with the environmental conservation policies thatwere implemented by the government, local farmers began to consider the adverse effectsof crop residue burning. In this regard, efficient utilization of organic resources throughcomposting of crop residues has been practiced. The objectives of this study were to findout the effects of adding Bacillus sp. on composting of crop residues and to observe theeffects of Bacillus sp. added crop residues on plant growth. The number of Bacillus sp.
colonies existing in crop residue and soil were determined by agar culture medium.
Composting was carried out based on the number of Bacillus Bacterial colonies (cfu):
1.5×1014, 1.5×1016 or 1.5×1018 cfu. Carbon-to-nitrogen (C/N) ratio and number of Bacillus
Bacteria were measured once a week. To observe the effects of Bacillus sp. added
compost on plant growth, pots were prepared as control pots; crop residue pots; Bacillus sp.
added crop residue pots; and burned crop residue pots. Komatsuna (Brassica rapa) werecultivated. Based on the experimental results, it was found that compost with higher
number of Bacillus sp. have significant decrease of C/N ratio with time. Also, it was foundthat the mass of the crops in the pots added with Bacillus sp. (average 1.4 g) was larger
than that control pots (0.5 g). Therefore, adding of Bacillus sp. can promote decompositionof crop residues and enhance the quality of compost.
Keywords Bacillus sp. growth, C/N ratio, crop residues compost

INTRODUCTION
Burning of crop residues influenced the degradation of soil ecosystem and its quality (Srimuang etal., 2004). Therefore, treating of crop residues such as composting, for bio-fertilizer on crop isstrongly recommended (Li et al., 2012). Compost, a kind of organic fertilizer made from cropresidues, is an effective material for improving physical and chemical properties of soil. The
important factors to enhance decomposition are moisture, air and microorganisms. (Mihara et al.,2009). At rural areas, manure has become the source of microorganisms for compost. But withincrement in the rural development, family livestock industry has reduced. Therefore, crop residue
compost by manure is difficult to be sustained in the rural areas. Although there were many reportson the effect of adding organic matter on the crop residue composting, few studies have added
Bacillus sp. on decomposition. Therefore this study has been proposed. The objectives of this study
are 1) to find out the effects of adding Bacillus sp. on composting of crop residues and 2) toobserve the effects of Bacillus sp. added crop residues on plant growth.

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METHODOLOGYTo extract from corn residue, Bacillus Bacterial was cultured for 3 days in the incubator. This is
the Bacillus sp. in liquid used for the experiment. The number of Bacillus sp. colonies existing wasdetermined by agar culture medium. The concentration of Bacillus sp. liquid was 6×1015 cfu/ml(colony-forming units per milliliter). Dilution of the Bacillus sp. liquid was made in different
concentrations of 6×1011 cfu/ml, 6×1013 cfu/ml, 6×1015 cfu/ml with crop residue compost (Fig. 1).

Fig. 1 Bacillus sp. liquid made by corn residue
The different concentrations of Bacillus sp. at 250 ml was added to the finely cut dry corn
residues at 50 g in a tray (L186 mm, W147 mm, and H47 mm). The different concentrations
sprinkled were control tray (no cfu added), 1.5×1014 cfu added tray (same cfu of 50 g residues),
1.5×1016 cfu added tray (100 times more than cfu of 50 g residues) and 1.5×1018 cfu added tray
(10000 times more than cfu of 50 g residues) at tray (Table 1). Period of composting was from
August 3rd to August 31st, temperature of the experiment was about 25 degrees Celsius to 37
degrees Celsius in Tokyo (Japan). 50 ml of water was sprinkled once every 3 days, and samples
were stirred after that (Fig. 2). The experiment data was collected once a week. Samples ofdifferent concentrations were subjected to carbon-to-nitrogen (C/N) ratio analysis, to understandthe effects of adding Bacillus sp. on crop residue composting processes. Following that, the numberof Bacillus Bacteria was measured after water was sprinkled.
Table 1 Number of Bacillus Bacterial cfu at corn residues and Bacillus sp. liquidCorn residues
3 ×1012 cfu/g
1.5×1014 cfu/50g

Bacillus sp. liquid I
6 ×1011 cfu/ml
1.5×1014 cfu/250ml

Bacillus sp. liquid II
6 ×1013 cfu/ml
1.5×1016 cfu/250ml

Bacillus sp. liquid III
6 ×1015 cfu/ml
1.5×1018 cfu/250ml

Fig. 2 Crop residue compost in laboratory of Japan
Meanwhile, in the growth experiment; 20 pots were prepared (unit area is 1/10000 a, and aheight of 150 mm), and was divided into four experimental pots. In control pots, 900 g of soil wasput into 5 pots. In residue added pots, 900 g of soil and 12.2 g dry corn residue was put into 5 pots.
In Bacillus sp. added pots, 900 g of soil, 12.2 g dry corn residue and 61 ml Bacillus sp. liquid(6×1015 cfu/ml) was put into 5 pots. In ash of residues added pots, 900 g of soil and ash of 12.2 g
dry corn residue was put into 5 pots. Kamatsuna (Brassica rapa) were cultivated (Fig. 3). The© ISERD
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growing period was from August 10th 2012 to September 7th 2012, temperature during theexperiment was about 25 degrees Celsius to 37 degrees Celsius in Tokyo (Japan); 100 ml of water
was sprinkled once every 3 days; and length of growth was obtained after the water was sprinkled.
And at the final experiment, weight of growth was measured in laboratory.

Fig. 3 Crop growth in laboratory
RESULTS AND DISCUSSION
In the crop residue composting of sprinkled Bacillus sp. experiment with 1.5×1018 cfu added tray
crop residue, it presented decomposition closer to compost maturity over the others concentrationsof Bacillus sp. liquid added tray. The carbon-to-nitrogen data showed that 1.5×1018 cfu added tray
has a tendency to decrease throughout all of the experiment; meanwhile the other tray showed
increment at 3 weeks times followed with continuous decrease pattern (Fig. 4). Initially, rise in the
carbon-to-nitrogen ratio were observed due to the growth of the added microorganisms and theirconsumption of nitrogen. After that, in order to decompose organic matter, microorganisms absorb
from raw material. Once the decomposition process started the microorganisms populations
continually increase to the maximum population level. Having reached maximum population, theC/N ratio decreases to the conversion with the normal composting line where there is no moredecomposition (Nishio, 2009) is possible.

control (no cfu added), 1.5 ×1014 cfu added (same cfu of 50 g corn residues added), 1.5 ×10 16 cfu added (100 times morethan cfu of 50 g corn residues added), 1.5 ×1018 cfu added (10,000 times more than cfu of 50 g corn residues added)

Fig. 4 Changes in carbon-to-nitrogen with difference concentration of Bacillus sp. added
In finished crop residue compost, the number of Bacillus Bacterial colonies returned to thesame number of that preceding the addition of Bacillus sp (Fig. 5). Therefore, the added Bacillus sp.
was used as a nutrient during the composting experiment.
Besides that, in this experiment, the effect of Bacillus sp. added into crops can be observed bycomparing the height of crop growth. It was found that crops grown in pots added with Bacillus sp.
have grown 2.8 times higher (1.4 cm) than that of control pots (0.5 cm). A significant difference at© ISERD117

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99% was also observed. Although the crop grown in pots added with Bacillus sp. is higher thanresidue pots and ash of residue pots, there is no significant difference observed by the method ofdispersion ratio (Fig. 6). The experiment result shows the crop grown with residue grows muchbetter than the crop grows without residues because the residue is rich in nutrients (Zhong et. al2003).

control (no cfu added), 1.5 ×1014 cfu added (same cfu of 50 g corn residues added), 1.5 ×10 16 cfu added (100 times morethan cfu of 50 g corn residues added), 1.5 ×1018 cfu added (10,000 times more than cfu of 50 g corn residues added)

Fig. 5 Change in quantity of Bacillus sp. before and after the experimentcontrol (only put soil in pots), residue (put residues and soil in pots), bacillus sp. and residue (put bacillus sp., residues
and soil in pots), ash of residue( put ash and soil in pots)

Fig. 6 Height of crop in growth experiment
The effect of Bacillus sp. added compost into crops can be observed by comparing the weightof crop growth. It was found out that crop grown in Bacillus sp. added into pots have 2.5 times
higher (1.5 g) than control sample (0.6 g). Furthermore, the crop grown in Bacillus sp. was 1.9
times heavier than crop grown in ash of residue in Fig.7. A confidence interval at 99% was also
observed. Moreover, the order of experiment results which is more environmental friendly way togrow the crop is: adding Bacillus sp. > adding residue > adding ash of residue > control. Therefore,
based on the result of the experiment, mixing Bacillus sp. liquid with mulching crop residues is thebest way to improve crop growth compared to burning crop residues in the farmland.

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IJERD – International Journal of Environmental and Rural Development (2013) 4-2control (only put soil in pots), residue (put residues and soil in pots), bacillus sp. and residue(put bacillus sp., residues and soil in pots), ash of residue( put ash and soil in pots)

Fig. 7 Weight of crop in growth experiment
CONCLUSION
Crop residue composting of sprinkled Bacillus sp. experiment found that in the 1.5×1018 cfu added
tray crop residue decomposition was closer to compost maturity than the others concentration ofBacillus sp. liquid added tray. Within the experiment, the added Bacillus sp. pots showed better
length and weight of crop growth compared to other pots. Therefore, adding Bacillus sp. to crop
residue compost is recommended. Plus, adding Bacillus sp. has positive influence to crop growth.
This experiment was carried out during summer season in Tokyo (Japan). Temperature has asignificant impact with crop residue composting. Therefore, location and temperature are two
important factors to be taken into consideration in this study.
ACKNOWLEDGEMENTS
The authors wish to acknowledge the support made by members of Lab. of Land and Water Use
Engineering, Tokyo University of Agriculture, Japan.
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