Livestock Research for Rural Development 30 (4) 2018 Guide for preparation of papers LRRD Newsletter

Citation of this paper

Biochar as amendment to soil growing cassava for foliage

Outhomphone Senviset and T R Preston1

Savannakhet University, Lao PDR
outhomphone8@hotmail.com
1 Centro para la Investigación en Sistemas Sostenibles de Producción Agropecuaria (CIPAV), Carrera 25 No 6-62 Cali, Colombia

Abstract

The design of this experiment was a 2*2*5 factorial with 3 replications in a split-plot arrangement. The main plots were biochar levels of 0, 0.5, 1, 1.5 and 2 kg/m2 of soil; the split plots were cassava variety (sweet or bitter) and partial peeling (or no peeling) of the cassava stems prior to planting.

The rate of germination was much higher for stems from bitter compared with sweet variety of cassava, and was higher when the stems were partially peeled, but was not affected by soil amendment with biochar. Yields of all components of the above-ground biomass were much higher for the bitter than the sweet cassava variety. There were no effects on foliage yield due to level of biochar. Soil pH, water-holding capacity, content of organic matter and of nitrogen were all enhanced with linear trends as the level of biochar added to the soil was increased.

Key words: foliage, germination, planting method, variety


Introduction

Cassava is a staple food crop in Lao PDR. However, it has now become the second most important crop in Lao PDR, as a result of the development of industrial extraction of starch from the cassava roots. It has also recently been shown that the byproduct pulp from cassava starch extraction, as well as the whole cassava root, can be the basis of intensive fattening systems of local cattle (Phanthavong et al 2016a,b; Sengsouly and Preston 2016). The cassava foliage can also be used as the basal diet for intensive feeding of goats (Sina et al 2017).

These developments have encouraged the introduction of improved cassava varieties with higher yield potential. Most of the new varieties are considered to be “bitter” varieties because of the higher concentrations of cyanogenic glucosides. The sweet varieties are those used for human consumption.

However, there appears to be no information on the relative responses of both “bitter” and “sweet” varieties to new agronomic practices such as the use of biochar as soil amender (Lehman and Joseph 2011; Preston 2015).

The objective of the experiment to be reported in this paper was to study the response of bitter and sweet varieties of cassava to application of increasing levels of biochar. Cassava was established by planting short lengths of stems directly in the soil. Possible advantages from limited peeling of the stems to encourage germination were also examined in view of the successful use of this technique for hastening the germination and survival of stem cuttings of the mulberry tree (Morus alba) (Moreno et al 2005; Bouaravong et al 2017).


Materials and Methods

Location

The experiment was conducted on Nongpheu campus, Savannakhet University, Lao PDR. The trial covered a period of 150 days from 12 June to 8 November 2016.

Experimental design

The design was a 2*2*5 factorial with 3 replications in a split-plot arrangement. The main plots were biochar levels of 0, 0.5, 1, 1.5 and 2 kg/m2; the split plots were cassava variety (sweet or bitter) and partial peeling (or no peeling) of the cassava stems prior to planting.

The total area was 240 m2 (6*40 m). The plots were 1.5*1.5m; the distance between each replication and plots was 0.5 m; the distance between rows in each plot was 0.5 m with 0.5 m between individual stems.

Procedure

The cassava stems were from cassava plants 8-12 months old. They were cut into lengths of 20 cm and inserted vertically 10 cm into the soil. The first harvest of foliage was made at 60 days and the second harvest 90 days later.

Biochar was produced from rice husk combusted in a gasifier stove (Photos 1 and 2). It was mixed into the top 10 cm of soil according to the treatments.

Urea was applied as fertilizer at the rate of 50 kg N/ha. The plots were irrigated every evening. Weeds were removed on days 31 and 91.

Photo 1. Burning rice husk to make biochar Photo 2. Biochar from rice husk


Photo 3. Arrangement of the plots Photo 4. Appearance of the soil with biochar
levels from 0 to 2 kg/m2


Photo 5. Bitter cassava with biochar (2 kg/m2)
after 60 days of growth
Photo 6. Sweet cassava with biochar (2 kg/m2)
after 60 days of growth
Photo 7. Filtering of biochar after 24h
suspension in water
Data collection

Samples of soil were analyzed at the beginning and end of the trial for DM (drying at 100oC for 24h), pH and water holding capacity (WHC). WHC of the soil and water retention rate (WRR) of the biochar were measured by suspending 1 kg of soil/biochar in 5 liters of water for 24h. The suspension was then filtered  (Photo 7) to determine the amount of water retained by the  soil/biochar. WHC was exprssed as percentage of water in the saturated soil. WRR  was expressed as liters of water/kg biochar.

Observations were made of germination of the stems and the height of the plants. At harvest the above-ground biomass was separated into stems, leaves and petioles.  AOAC (1990) methods were followed for analysis of : DM and crude protein in each component of the cassava foliage, and of ash and N in the soil and the biochar.

Statistical analysis

The data were analyzed using the GLM option of the Minitab (2000) ANOVA software. Sources of variation were; biochar level, sweet or bitter cassava, peeling or no peeling the stems; interaction biochar level*sweet or bitter cassava, and error.


Results

Chemical composition of the soil and the biochar

The soil was acid and low in organic matter and nitrogen (Table 1).The water retention rate (WRR)  of the biochar was similar to the value reported by Orosco et al (2018) for biochar produced from rice husks.

Table 1. Composition of soil and rice husk biochar.

DM, %

pH

WHC, %

WRR

OM, %

N, %

Soil

86.6

5.40

42.5

 

0.80

0.05

Biochar

93.5

8.61

-

4:1

-

Germination

The rate of germination was much higher for stems from the bitter compared with the sweet variety of cassava and was higher when the stems were partially peeled (Table 2; Figures 1 and 2) but was not affected by soil amendment with biochar.

Biomass yield

Yields of all components of the above-ground biomass were much higher for the bitter than the sweet cassava variety. There were no effects on foliage yield due to level of biochar (Tables 2 and 3, Figures 3 and 4) and no interaction (p= 0.71) between variety and level of addition of biochar.

Table 2. Mean values for effects of variety and peeling of the cuttings on germination, height and biomass yield of bitter and sweet cassava

Cassava

p

Peeling

p

SEM

Bitter

Sweet

No

Yes

Germination, %

96.3

55.6

0.001

71.9

80.0

0.05

2.8

First harvest

Height, cm

72.4

60.3

0.001

67.3

65.4

0.62

2.69

Fresh biomass, kg/m2

Total

2.65

0.99

0.001

1.94

1.7

0.23

0.054

Stem

0.89

0.31

0.001

0.65

0.55

0.23

0.048

Petiole

0.74

0.31

0.001

0.58

0.47

0.11

0.060

Leaves

1.03

0.37

0.001

0.72

0.68

0.62

0.20

Second harvest

Height, cm

237

230

0.33

233

234

0.82

4.9

Fresh biomass, kg/m2

Total

12.5

9.16

0.001

10.5

11.1

0.50

0.67

Stem

6.27

5.00

0.02

5.43

5.84

0.46

0.38

Petiole

2.29

1.41

0.001

1.66

2.04

0.15

0.19

Leaves

3.62

2.50

0.001

3.11

3.01

0.70

0.19



Table 3. Mean values for effect of biochar on germination, height and biomass yield of cassava grown for forage (average of bitter and sweet varieties)

Biochar, kg/m2

p

SEM

0

0.5

1.0

1.5

2.0

Germination, %

80.6

80.6

80.6

80.6

80.6

0.77

0.40

First harvest

Height, cm

63.8

69.8

67.9

62.1

68.1

0.68

4.25

Fresh biomass yield, kg/m2

Total

1.92

1.95

1.83

1.67

1.71

0.87

0.23

Stem

0.66

0.63

0.63

0.53

0.55

0.78

0.09

Petiole

0.53

0.52

0.58

0.5

0.5

0.29

0.08

Leaves

0.74

0.81

0.63

0.65

0.67

0.52

0.09

Second harvest

Height, cm

232

231

237

222

245

0.35

7.7

Fresh biomass yield, kg/m2

Total

11.1

10.7

11.2

9.55

11.6

0.71

1.07

Stem

5.8

5.3

5.93

5.03

6.12

0.68

0.60

Petiole

1.75

1.67

1.85

1.72

2.27

0.64

0.30

Leaves

3.30

3.19

2.97

2.38

3.48

0.12

0.31



Figure 1. Germination was much higher for the bitter variety of cassava than the
sweet one and was higher when the stem was partially peeled
Figure 2. Germination was not affected by application of biochar to the soil


Figure 3. Yield components of cassava were not affected by biochar Figure 4. Biomass yield of cassava was higher for bitter than sweet variety
Soil fertility

Soil pH, water-holding capacity, content of organic matter and of nitrogen were all enhanced with linear trends as the level of biochar added to the soil was increased (Table 4; Figures 5, 6, 7 and 8).

The soil pH was increased linearly from 5.40 to 6.92 as the level of biochar was increased from 0 to 2.0 kg/m2 (Tables 1 and 4, Figure 5). Similar responses have been reported by many researchers (eg: Rodríguez et al 2009; Southavong et al 2012; Dao et al 2013). Water holding capacity was increased by application of biochar from 42.5 to 54.4% (Tables 1 and 4, Figure 3). The result was similar to that reported by Sokchea et al (2011) and Southavong et al (2011). The organic matter in the soil was increased from 0.80 to 1.43% at the biochar level of 2 kg/m2 (Tables 1 and 4 and Figure 4). The soil nitrogen was increased ten-fold (from 0.12 to 1.53%) when biochar was added to the soil at 2 kg/m 2 (Table 4; Figure 8).

Table 4. Mean values for effect of biochar on soil pH, water-holding capacity (WHC), organic matter and nitrogen content

Level of biochar, kg/m2

p

SEM

0

0.5

1.0

1.5

2.0

pH

5.95

5.98

6.56

6.59

6.92

0.04

0.25

WHC, %

42.3

46.3

47.3

50

54.4

<0.001

1.44

OM, %

0.85

1.1

1.17

1.4

1.43

<0.001

0.05

N, %

0.12

0.57

0.89

1.09

1.53

<0.001

0.11



Figure 5. Biochar increased the soil pH Figure 6. Biochar increased the water holding capacity of the soil




Figure 7. Biochar increased the organic matter content of the soil Figure 8. Biochar increased the nitrogen content of the soil


Discussion

The positive effects of adding biochar to the soil on pH, water-holding capacity, organic matter, nitrogen and pH are in line with the report of Chittavong et al (2017) who recorded similar effects of biochar amendment in the same soil type. However, while these soil improvements were associated with increased biomass yields - in the case sugar cane (Chittavong et al 2017) - in our experiment, biomass yield of cassava was not affected. The quality of the biochar was not considered to be a factor as the water retention rate (WRR = 4:1), assumed to be indicative of the capacity of the biochar to adsorb nutrients/microbes, was of the same magnitude as was reported by Orosco et al (2018) for biochar made from rice husks.

We have no explanation for our results in which soil fertility was improved by addition of biochar but this improvement was not reflected in biomass yield of the cassava grown for forage. Clearly this is an area of research that should be studied comprehensively in view of the increasing importance of cassava cultivation in Lao PDR.


Conclusions


Acknowledgements

This research was done by the senior author as part of the requirements for the MSc degree in Animal Production "Improving Livelihood and Food Security of the people in Lower Mekong Basin through Climate Change Mitigation" in Cantho University, Vietnam. The authors would like to express their appreciation to: the MEKARN program funded by SIDA for providing the opportunity and budget to carry out the study; and to Savannakhet University for the facilities to conduct the experiment. We thank the BSc students and staff of Savannakhet University for their help in facilitating the execution of the experiment.


References

AOAC 1990 Official Methods of Analysis. Association of Official Analytical Chemists. 15th edition (K Helrick editor). Arlington pp 1230

Bouaravong B, Dung N N X and Preston T R 2017 Effect of biochar and partial peeling of stems on soil fertility and germination of Erythrina variegata cuttings. Livestock Research for Rural Development. Volume 29, Article #70. http://www.lrrd.org/lrrd29/4/boun29070.html

Chittakone I, Xuan Dung N N and Preston T R 2017 Sugar cane had higher yield when established from node cuttings rather than from long stems and had a higher sugar content when the soil was amended with biochar. Livestock Research for Rural Development. Volume 29, Article #219. http://www.lrrd.org/lrrd29/11/lay29219.html

Dao T T, Canh N T, Trach N X and Preston T R 2013 Effect of different sources of biochar on growth of maize in sandy and feralite soils. Livestock Research for Rural Development. Volume 25, Article #59. http://www.lrrd.org/lrrd25/4/dao25059.htm

Lehmann J and Joseph S 2011 Biochar for Environmental Management, Science and Technology, Earthscan, UK.

Minitab 2000 Minitab reference Manual release 13. User’s guide to statistics. Minitab Inc., USA

Moreno F A, Márquez A y Preston T R 2005 Cuatro métodos de propagación vegetativa de Morera (Morus alba). Livestock Research for Rural Development. Volume 17, Art. No. 58. http://www.lrrd.org/lrrd17/5/more17058.htm

Orosco J, Patiño F J, Quintero M J and Rodríguez L 2018 Residual biomass gasification on a small scale and its thermal utilization for coffee drying. Livestock Research for Rural Development. Volume 30, Article #5. http://www.lrrd.org/lrrd30/1/jair30005.html

Phanthavong V, Khamla S and Preston T R 2016a Fattening cattle in Lao PDR with cassava pulp. Livestock Research for Rural Development. Volume 28, Article #10. http://www.lrrd.org/lrrd28/1/phan28010.html

Phanthavong V, Preston T R, Viengsakoun N and Pattaya N 2016b Brewers' grain and cassava foliage (Manihot esculenta Cranz) as protein sources for local “Yellow” cattle fed cassava pulp-urea as basal diet. Livestock Research for Rural Development. Volume 28, Article #196. http://www.lrrd.org/lrrd28/11/phan28196.html

Preston T R 2015 The role of biochar in farming systems producing food and energy from biomass. In: Geotherapy: Innovative Methods of Soil Fertility Restoration, Carbon Sequestration and Reversing CO2 Increase (Editor: Thomas J Goreau) CRC Press, Tayler and Francis Group, Boca Raton, Florida USA

Rodríguez L, Salazar P and Preston T R 2009 Effect of biochar and biodigester effluent on growth of maize in acid soils. Livestock Research for Rural Development. Volume 21, Article #110. http://www.lrrd.org/lrrd21/7/rodr21110.htm

Sengsouly P and Preston T R 2016 Effect of rice-wine distillers’ byproduct and biochar on growth performance and methane emissions in local “Yellow” cattle fed ensiled cassava root, urea, cassava foliage and rice straw. Livestock Research for Rural Development. Volume 28, Article #178. http://www.lrrd.org/lrrd28/10/seng28178.html

Sokchea H and Preston T R 2011 Growth of maize in acid soil amended with biochar, derived from gasifier reactor and gasifier stove, with or without organic fertilizer (biodigester effluent). Livestock Research for Rural Development. Volume 23, Article #69. http://www.lrrd.org/lrrd23/4/sokc23069.htm

Southavong S and Preston T R 2011 Growth of rice in acid soils amended with biochar from gasifier or TLUD stove, derived from rice husks, with or without biodigester effluent. Livestock Research for Rural Development. Volume 23, Article #32. http://www.lrrd.org/lrrd23/2/siso23032.htm

Southavong S, Preston T R and Man N V 2012 Effect of biochar and biodigester effluent on growth of water spinach (Ipomoea aquatic) and soil fertility. Livestock Research for Rural Development. Volume 24, Article #34. Retrieved April 4 2017, from http://www.lrrd.org/lrrd24/2/siso24034.htm

Sina V, Preston T R and Ho Thanh Tham 2017 Brewers’ grains have a synergistic effect on growth rate of goats fed fresh cassava foliage (Manihot esculenta Crantz) as basal diet. Livestock Research for Rural Development. Volume 29, Article #137. http://www.lrrd.org/lrrd29/7/sina29137.html


Received 10 January 2018; Accepted 28 February 2018; Published 1 April 2018

Go to top