Livestock Research for Rural Development 25 (4) 2013 Guide for preparation of papers LRRD Newsletter

Citation of this paper

Synergism between biochar and biodigester effluent as soil amenders for biomass production and nutritive value of Mustard green (Brassica juncea)

Chhay Ty, Miech Phalla, Khieu Borin and T R Preston*

Center for Livestock and Agriculture Development. Pras Teat village, Rolous Commune, Kandal Stung district, Kandal province.
PO Box 2423 Phnom Penh 3, Cambodia
chhayty@celagrid.org
* Finca Ecológica, TOSOLY, AA #48, Socorro, Santander, Colombia

Abstract

An experiment was conducted in the dry season (February to March 2013) involving ten treatments arranged in a 2*5 factorial arrangement of a random block design with 2 replications. The first factor was level of biochar (0 and 4 kg/m2); the second factor was level of effluent from biodigester (0, 2.5, 5.0, 7.5 and 10 kg N/ha). The area of each plot was 1.6m2 (2.0m length x 0.8m width) with spacing between each plot of 0.5m. The experiment lasted 40 days. The biochar was from a paddy rice drier (combustion temperature with rice husks as feedstock was about 500°C).

For all levels of effluent N application, the addition of biochar led to more than two-fold increases in above ground biomass yield. Biochar had no effect on biomass yield in the absence of effluent, and there were no further responses to effluent N when this exceeded a level of 2.5 kg N/ha. Biochar increased the crude protein in the leaves by an average of 16%, with the relative increase being greater when effluent was applied. A reduction in crude fiber content of the leaves due to biochar was  observed at low levels (< 5 kg N/ha) of application of effluent N, with the opposite effect being apparent at levels of N of 7.5 and 10 kg/ha.

Key words: fiber, leaves, pH, protein, stems, yield


Introduction

Biochar is the carbon-rich product obtained when biomass, such as wood, manure or leaves, is heated in a closed container with little or no available air and at high temperatures (from 600 to 1000 °C). (Lehmann and Joseph 2009). Biochar is unlikely to have a major role as a fertilizer but, because of its structure, it can be expected to increase water-holding capacity, and be a good habitat for microbes and plant nutrients (Thies and Rillig 2009).

Huy Sokchea et al (2013) showed that application of 30 tonnes/ha biochar to a rice crop increased grain yield by 30% and straw yield by 40%. A study by Boun Suy Tan (2010) also showed that the rice yields were more than doubled (3.76 tonnes/ha) by application of 40 tonnes/ha of biochar compared with without biochar which yielded only 1.25 tonnes/ha. In a recent experiment we found that the yield and nutritive value of different types of vegetable were increased linearly with the application of biochar from 0 to 5 kg/m2; soil quality after the experiment was improved. 

The aim of the present study was to examine the possible synergism between biochar and digester effluent as soil amenders for biomass production and nutritive value of mustard green.


Materials and Methods

Location

The experiment was carried out at the Center for Livestock and Agriculture Development (CelAgrid) located in Prah Theat village, Sangkat Rolous, Khan Dangkor, approximately 25 km from Phnom Penh city. The experiment was conducted in the dry season from February to March 2013. 

Experimental design

The experiment design was a Randomized Complete Block (RCBD) involving ten treatments arranged in a 2*5 factorial arrangement with two replications. The first factor was level of biochar (0 and 4 kg/m2); the second factor was level of biodigester effluent (0, 2.5, 5.0, 7.5 and 10kg N/ha).

Land preparation

The land was plowed and sun-dried for a week before making the beds; the area of each bed was 1.6m2 (2.0m length x 0.8m width) and spacing between each bed was 0.5m.   

Planting vegetables

Mustard green was germinated in a nursery without applying any fertilizer and the best plants selected for transplanting at 18 days with 20 cm distance from plant to plant.

Irrigation, biochar and biodigester effluent application

The biochar was the residue from combusting rice husks in a paddy rice dryer in which the furnace temperature was from 500 to 6000C. This temperature is similar to that in a conventional down-draft gasifier and it has been shown that there were no differences in the yield response of rice to biochar from the paddy rice dryer and a conventional gasifier (Huy Sokchea et al 2013).  The biochar was incorporated in the upper 10 cm of the soil in each of the beds.

Photo 1: Biochar from paddy rice dryer

Photo 2: Soil without biochar

Photo 3: Soil mixed with biochar, 4kg/m2

The biodigester effluent was from a fixed dome brick and concrete model which had a capacity of 15m3. It was charged with manure from pigs fed a commercial concentrate feed and spent brewer's grain. The biodigester effluent was pumped into PVC containers located in the experimental area. It was applied at levels of  0, 2.5, 5.0, 7.5 and 10 kg N/ha. The amounts applied were as proportions of the total application) of 20, 40 and 40% at 21, 28 and 35 days of age of the plants, respectively. The effluent was diluted with water in proportions of 50:50 (fresh basis) before application. The plots were irrigated 2 times a day (morning and evening). 

Measurements

The plant height and numbers of leaves were measured at 21, 28, 35 and 40 days after planting. At the end of the experiment (40 days), representative plants were harvested including the roots in order to measure total biomass yield and composition.  

Chemical analysis

Soil samples were analyzed before and after completing the experiment). Soil and biochar samples were analyzed for pH, organic content (OM) and N by methods from "Soil chemical analysis": http://www.icarda.org/Publications/Lab_Manual/PDF/part5.pdf). The biodigester effluent was analyzed for DM, N and NH3-N at each application. The mustard green biomass was analyzed for organic matter, N and crude fiber following the methods in AOAC (1990); DM was determined using the method of Undersander et al. (1993).

Statistical analysis

The data were recorded in MS Excel and analyzed by the General Linear Model option in the Analysis of Variance (ANOVA) program of the Minitab software (2000). Sources of variation were: blocks, levels of biochar, level of biodigester effluent, interaction between level of biochar * level of biodigester effluent and error.


Results and discussion

Photo 4. Photos of the Mustard Green expeiment
Chemical composition of biochar and effluent 

The pH of the biochar was close to the level of 10.9 reported by Huy Sokchea et al (2013)  but the organic matter was higher in this study compared with the 10.3% reported by Huy Sokchea et al (2013).

Table 1: Chemical composition of biochar and effluent during experiment

Parameter

Biochar

Effluent

pH

9.07

ND

Dry matter, %

58.9

0.34

Organic matter, % in DM

19.8

ND

Nitrogen in DM, %

0.49

25.3

Nitrogen in fresh basis, %

0.29

0.086

NH3-N, % of total N

ND

68.0

ND: Not Determined 

 

 

Effects of biochar on the soil

The chemical composition of the soil showed improvements with increased content of organic matter, nitrogen and pH as a result of addition of biodigester effluent and the biochar at 4kg/m2.  Similar effects were reported by Chhay Ty et al (2013) and Huy Sokchea et al (2013) using biochar from a paddy rice dryer. Other studies with biochar from a downdraft gasifier (Rodriguez et al 2009) and updraft stove gasifier (Southavong et al 2012) confirmed similar effects of biochar as soil amendment.

Table 2: Chemical composition of soil before and at the end of the experiment (as % of DM)

 

 

level of biochar (b)

level of effluent (e)

b*e

 

 

0

4

SEM

Prob

0

25

50

75

100

SEM

Prob

Prob

Soil before

 

 

 

 

 

 

 

 

 

 

 

 

 

Organic matter

4.60  

Nitrogen

0.185  

pH

6.03  

Soil at the end

 

 

 

 

 

 

 

 

 

 

 

 

 

Organic matter

 

3.33

5.71

0.108

<0.001

4.02

4.59

4.87

4.46

4.67

0.171

0.053

0.004

Nitrogen

 

0.20

0.26

0.005

<0.001

0.168

0.180

0.222

0.302

0.290

0.009

<0.001

<0.001

pH

 

6.28

6.98

0.04

<0.001

6.26

6.68

6.63

6.80

6.79

0.06

0.001

0.016

 

 

 

 

 

 

 

 

 

 

 

 

 

 

There were interactions between level of biochar and level of effluent application on organic matter, N and pH of the soil. Soil pH was increased by biochar by 3% when no effluent was applied but the increases were much higher (from 11 to 16%) when effluent was applied (Figure 1). Organic matter levels in soil were increased linearly by effluent N in presence of biochar but the response to effluent N was curvilinear in the absence of biochar with the maximuym at 5 kg N/ha (Figure 2). There was no effect of biochar on soil N when no effluent was applied but there were increases in soil N wwhen effluent was applied (Figure 3).

Figure 1. Effect of biochar on soil pH with increasing levels
of application of nitrogen from biodigester effluent
Figure 2. Effect of biochar on soil organic matter with increasing
levels of application of nitrogen from biodigester effluent
Figure 3. Effect of biochar on soil pH with increasing levels
of application of nitrogen from biodigester effluent
Effects of biochar on the chemical composition of the plants

The DM content of leaves and stems were high on zero of biochar compared with 4kg/m2 but crude protein content of leaves was affected by the level of biochar that was applied; however, it was not affect on crude fiber in leaves as the application of biochar was increased from zero to 4 kg/m2. The value of DM content of leaves and stem in this study were contract with study of Chhay Ty et al (2013) who have been reported that the DM content of leaves and stems was not affected by the level of biochar that was applied (from 0, 1, 2, 3, 4 and 5kg/m2), but the crude protein content of leaves and stem increased 30% and the crude fiber decreased by 30% as the application of biochar was increased from zero to 5 kg/m2. The improvement in nutritive value can be as a result of soil amendment with biochar.

The chemical composition of mustard green leaves were improvement as content of DM, crude protein and fiber as a result of level of biodigester effluent application. Meanwhile, there was interaction on crude protein and crude fiber (P<0.05) but not on DM content (P>0.05).

Table 3: Effect of different level of biochar and level of effluent on chemical composition of mustard green

 

level of biochar (b)

level of effluent (e)

b*e

 

0

4

SEM

Prob

0

25

50

75

100

SEM

Prob

Prob

Dry matter, %

 

 

 

 

 

 

 

 

 

 

 

Leaves

16.1

11.9

0.53

<0.001

15.4

14.8

14.5

14.0

11.4

0.85

0.052

0.207

Stem

23.4

19.4

1.15

0.036

21.4

22.2

22.1

22.0

19.3

1.82

0.774

0.844

Crude protein, %

 

 

 

 

 

 

 

 

 

 

 

Leaves

15.9

18.6

0.12

<0.001

13.1a

16.0b

18.1c

19.6d

19.6d

0.20

<0.001

0.002

Crude fiber, %

 

 

 

 

 

 

 

 

 

 

 

Leaves

25.5

25.0

0.19

0.141

30.1a

26.5b

25.9b

21.6c

22.5c

0.30

<0.001

0.006

Application of biochar increased the crude protein in the leaves by an average of 16%, with the relative increase being greater when effluent was applied (Figure 4) . The reduction in crude fiber content of the leaves due to biochar was only observed at low levels of application of effluent N (Figure 5), with the opposite effect being apparent at levels of N of 7.5 and 10 kg/ha.

Figure 4: Relationship between level of biochar and level of
effluent on crude protein content of mustard green leaves

Figure 5: Relationship between level of biochar and level of
effluent on crude fiber content of mustard green leaves

Growth in height and numbers of leaves
The rate of growth in height of leaves was greater when biochar was applied and tended to increase (P=0.10) with increasing level of effluent N (Table 4; Figure 6). Similar responses were observed for effects of treatments on numbers of leaves (Figure 7). These effects of biochar were similar to those recorded previously by Chhay Ty et al 2013) with the same vegetable.

Table 4: Effect of different level of biochar and level of effluent on the height (cm) of mustard green

 

level of biochar (b)

level of effluent (e)

b*e

 

0

4

SEM

Prob

0

25

50

75

100

SEM

Prob

Prob

 Plant age, day

 

 

 

 

 

 

 

 

 

 

 

 

21

10.1

10.9

0.74

0.482

11.7

9.25

10.5

9.50

11.6

1.17

0.479

0.493

28

11.5

13.0

0.77

0.223

12.2

11.1

13.3

11.0

13.8

1.22

0.429

0.493

35

12.8

16.2

1.26

0.090

12.2

12.9

16.5

13.6

17.3

1.99

0.327

0.555

40

13.8

19.2

1.31

0.016

13.4

14.1

19.3

15.4

20.5

2.08

0.126

0.588

Growth, cm/day

0.20

0.44

0.06

0.035

0.09

0.25

0.46

0.31

0.47

0.10

0.137

0.541


Table 5: Effect of different level of biochar and level of effluent on number of mustard green leaves

 

level of biochar (b)

level of effluent (e)

b*e

 

0

4

SEM

Prob

0

25

50

75

100

SEM

Prob

Prob

 Plant age, day

 

 

 

 

 

 

 

 

 

 

 

 

21

3.0

3.7

0.12

0.003

3.2

3.3

3.8

3.3

3.2

0.20

0.182

0.251

28

4.7

5.6

0.23

0.034

4.5

5.1

5.8

4.6

5.7

0.37

0.089

0.638

35

6.0

7.8

0.49

0.026

5.3

6.8

8.2

6.7

7.6

0.78

0.173

0.498

40

7.2

9.5

0.59

0.022

6.2

7.9

9.6

8.2

9.9

0.94

0.108

0.657


Figure 6: Relationship between level of biochar and level of
effluent on growth in height of mustard green leaves
Figure 7: Relationship between level of biochar and level of effluent
on numbers of leaves of mustard green leaves at 40 days
 Biomass yield

Over all levels of effluent N application, the addition of biochar led to more than two-fold increases in above ground biomass yield (Table 6). Biochar had no effect on biomass yield in the absence of effluent, but with 2.5 kg N/ha  there were two to three fold increases in yield (Figures 8 and 9). Maximum response to biochar was with 5 kg N/ha with no advantage from application of higher levels of N. Many researchers have emphasized the importance of nutrient supply, especially nitrogen, as a determinant of plant growth response to soil amendment with biochar (see review by Sohi et al 2009). Similar synergistic effects on plant growth by combining charcoal with chicken manure were observed by Steiner et al (2007).

Table 6: Effect of different level of biochar and level of effluent on the yield of mustard green

 

level of biochar (B)

level of effluent (E)

B*E

 

0

4

SEM

Prob

0

25

50

75

100

SEM

Prob

Prob

Yield in fresh basis, g/m2

 

 

 

 

 

 

 

 

 

Leaves

230

679

55.8

<0.001

141

141

141

141

141

85.8

0.007

0.309

Stems

30.4

54.2

9.3

0.102

346

346

346

346

346

16.6

0.163

0.785

Root

18.0

41.0

10.4

0.148

4.13

34.0

25.0

26.1

59.3

13.3

0.146

0.83

Leaves + stems

260

733

54.5

 <0.001

156

369

685

520

752

86.2

0.005

0.347

Yield in DM, g/m2

 

 

         

 

 

 

Leaves

34.1

77.8

5.75

<0.001

20.5

40.5

81.5

63.1

74.3

9.09

<0.001

0.45

Stems

6.78

10.62

1.89

0.185

3.03

4.72

10.7

10.7

14.4

2.99

0.185

0.65

Leaves + stems

40.9

88.5

5.91

<0.001

23.5

45.2

92.2

73.8

88.7

9.35

0.002

0.4


Figure 8: Relationship between biochar and effluent N on
fresh biomass yield (leaves + stems) of mustard green
Figure 9: Relationship between biochar and effluent N on
biomass DM yield (leaves + stems) of mustard green


Conclusions


Acknowledgements

The authors would like to express their gratitude to the MEKARN project financed by Sida, and to the Center for Livestock and Agriculture Development (CelAgrid), for providing resources for conducting this experiment.


References

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Received 13 March 2013; Accepted 31 March 2013; Published 2 April 2013

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