|
|
|
|
Photo 1: Land preparation |
Photo 2: Seedling of Taro |
The experiment was conducted at the Integrated Farming Demonstration Centre, Champasack University, Lao PDR to investigate the effect of biochar and biodigester effluent on biomass yield of taro and on soil physical properties. The treatments were arranged in a randomized complete block design (RCBD) as a 3*2 factorial with 4 replications. The factors were application of biochar to soil at 30 tonnes/ha or none and three levels of biodigester effluent at 0, 50 or 100 kg N/ha. Twenty four plots were prepared with a total area of 235.2 m2. Each plot had an area of 9.8 m2 (2.8*3.5m). Taro was established from seedling with an average of about 1 month old. Plant spacing was 70 cm between rows and between plants in the row.
The result showed that there were differences on biomass yield of taro in DM at 84 days and 112 days after planting due to the application of biochar, but the yields due to 122 days was apparent more increased than 84 days. Besides the biomass yield in DM (both a plot and a hectare) also there was significant (P<0.05) in the treatment by application of biochar. However, combination of biochar and biodigester effluent was effected to more increase of the yields than application biochar or biodigester effluent only one. The water holding capacity of the soil was increased by application of biochar but there were no differences due to the level of biodigester effluent. Soil pH was increased by application of biochar from 5.3 to 5.94. There was no apparent effect of level of effluent on soil pH.
Taro (Colocasia esculenta (L.) Schott) is an ancient crop grown throughout the humid tropics for its edible corms and leaves, as well as other traditional uses. It occupies a significant place in the agriculture of the Asia-Pacific Region and supplies much-needed protein, vitamins and minerals, in addition to carbohydrate energy (Inno Onwueme 1999).
Taro has an energy content of above 4,000 kcal/kg of dry matter and can be a good source of energy in animal feed. The total production in Africa in 1998 reached about 6.5 million metric tons representing 75 % of the total world production (8.5 million tons) (Onwueme 1999). The average taro yield in Africa is about 5.1 t/ha as compared with 1.6 t/ha for maize (Raemaekers 2001).
According to Wang (1983), taro has great potential as animal feed in the tropics and subtropics where it is often a staple food for pigs. However, because of the problem of the presence of calcium oxalate, the leaves, petioles and corms of taro are often considered unacceptable for direct use as an animal feed (Jiang Gaosong et al 1996). Wang (1983) claimed that this problem could be solved by the fermentation occurring during the process of ensiling.
Recent interest in the use of biochar as a soil amender (Lehmann et al 2007) has its origin in the discovery, by Dutch soil scientist Wim Sombroek in the 1950's, of pockets of rich, fertile soil in the Amazon rainforest (otherwise known for its poor, thin soils). He gave it the name of Terra Preta ("black earth"). Carbon dating has shown that the carbon in these soils dates back to between 1,800 and 2,300 years (Glaser 2007).
The apparent high fertility of Terra preta soils, has led to research to measure the immediate effects of “biochar” addition to soils on plant growth. Major increases (up to 324%) in yield of a range of crops through addition of biochar at rates varying from 0.5 to 135 tonnes/ha were recorded in the review by Sohi et al (2009). However, these authors state that addition of nutrients from inorganic or organic fertilizers is usually essential for high productivity and to increase the positive response from the biochar amendment. Chan et al (2008) recorded a linear increase in yield of radish (Raphanus sativus) by addition of up to 50 tonnes/ha of biochar provided additional N fertilizer was also supplied. Glaser (2007) also indicated that there would be benefits in plant growth from combining the biochar with chicken manure.
Sismophone Southavong and Preston (2010) reported that the biochar could increase the water holding capacity of the soil from (37.9, 45.4, 51.8, 51.2 and 59.6 %) by different level of biochar (0, 2, 4, 6, and 8 %) and pH level of biochar was 9.8
Biodigester effluent from live stock excreta contains a high proportion of the nitrogenous constituents as ammonium salts. Pedraza et al (2002) observed that the proportion of ammonia-N in the effluent from plug-flow tubular plastic biodigesters was in the range of 0.65 to 0.75. Similar findings were reported by San Thy et al (2003). In their study, the proportion of ammonia-N to total-N increased from 0.077 to 0.12 in fresh pig manure to 0.46 to 0.65 in the effluent. The combination of biodigester effluent and biochar therefore should be synergistic in improving soil fertility and plant growth.
· The growth performance and the Biomass yield of Taro will be increased when biochar and biodigester effluent are applied.
· Application of biochar will improved soil properties and fertilities.
The experiment was carried out in the integrated farming demonstration center of Champasack University located in the Huay Leusy village, about 13 km from Pakse district, Champasack province, Lao PDR between November 2011 and June 2012, the mean air temperature of 28.2°C and average annual rainfall of 2000mm/year.
· Biochar: With or without at 3 kg/m2.
· Effluent: 0, 50 and 100 kg N/ha.
The individual treatments were:
|
Table 1. Experimental layout |
||||||
|
Rep I |
B3E50 |
B0E0 |
B0E100 |
B3E100 |
B0E50 |
B3E0 |
|
Rep II |
B3E100 |
B3E0 |
B0E50 |
B0E0 |
B3E50 |
B0E100 |
|
Rep III |
B0E0 |
B3E0 |
B3E50 |
B0E100 |
B0E50 |
B3E100 |
|
Rep IV |
B0E50 |
B0E100 |
B3E0 |
B3E100 |
B0E0 |
B3E50 |
Twenty four plots were prepared by two wheels tractor (clearing was made at the same time) with a total area of 470 m2. Each plot has an area of 19.6m2 (5.6*3.5m). The sources of planting material were collected from the farmers in Pathoumphone district with an average of about 1 month old. Plant spacing was 70 cm between rows and between plants in the row, equivalent to 40 plants/plots or 20,408 plants/ha and the taro was planted in the depth of 20 cm.
|
|
|
|
Photo 1: Land preparation |
Photo 2: Seedling of Taro |
Samples of the effluent were analyzed for N before applying to the Taro plots. Effluent from the biodigester was applied to the treatments at the beginning of planting and then at 14 day interval (total 5 times). The quantities were calculated according to the N content of the effluent to give the equivalent of 50 or 100 kg N/ha or (5 or 10 g N/m2). As for the biochar was applied at 30 kg/ha (3 kg/m2) just once at the beginning of the trial. Water was applied uniformly to all plots every morning and evening.
|
|
|
|
Photo 3: Biochar |
Photo 4: Biodigester effluent |
Measurements were made of height, wideness and number of leaves at weekly until constant growth and the plats harvested from each plots were counted. Soil pH, dry matter, were recorded at the beginning and at the end of the trial.
Harvesting
The first harvest was started at 84 days after planting and continued of the second harvest at 28 days after first harvest or equivalent of 112 days after planting. All the mature leaves and petioles were removed leaving the two youngest to facilitate the re-growth.
|
Photo 5: Taro at 84 days after planting |
|
|
|
|
|
Photo 6: Harvest |
The data was analyzed by analysis of variance using the ANOVA option and General Linear Model of Minitab Reference Manual Release 13.20 (Minitab, 2000). The sources of variation in the model for the statistical analysis were: Biochar, biodigester effluent, biochar* biodigester effluent interaction, block and error.
Chemical analysis
The dry matter (DM) content of soil, biochar and biomass of Taro were determined using the micro-wave relation method of Undersander et al (1993). Soil samples were analyzed for organic matter (OM) by AOAC (1990) method. Biodigester effluent and biomass of Taro were analyzed for nitrogen (N) content according to AOAC (1990) method. The pH of soil samples was determined using microprocessor pH meter. Water holding capacity was determined by saturating the soil with water and then leaving it in a funnel lined with filter paper during 24 hours.
|
Table 2: Mean values for composition of experiment materials and composition of Taro biomass yield |
|||||
|
DM, % |
OM, % in DM |
pH |
N, g/ Littre |
||
|
Experimental materials |
|||||
|
Soil |
78.69 |
11.6 |
5.3 |
0.11# |
|
|
Biochar |
83.0 |
4.11 |
6.1 |
NA |
|
|
Effluent |
NA |
NA |
7.16 |
0.26 |
|
|
NA: Not analysed # N, g/kg soil |
|
||||
|
Table 3: Mean values for Water holding capacity of the soil before planting |
|
|
Soil amender |
Water holding capacity, % |
|
Biochar |
18.33 |
|
None |
18.16 |
|
Table 4: Mean values for effects of biochar and level of effluent on soil pH and water holding capacity (after 84 days from planting) |
||
|
|
Soil pH |
WHC, % |
|
Soil amender |
|
|
|
Biochar |
5.94 |
8.9 |
|
Soil |
5.53 |
8.48 |
|
Prob. |
0.22 |
0.49 |
|
SEM |
0.23 |
0.27 |
|
Effluent level |
|
|
|
0 |
5.64 |
7.82c |
|
50 |
5.68 |
8.85b |
|
100 |
5.88 |
9.18a |
|
Prob. |
0.81 |
0.03 |
|
SEM |
0.28 |
0.34 |
|
Prob. (interactions) |
||
|
S*E |
0.74 |
0.45 |
|
S: Soil amender, E: Effluent level, Prob: Probability |
||
|
The superscript ab in the same column is significantly different (P<0.05) |
||
|
|
|
|
Figure 7: Effect of biochar and biodigester effluent on soil |
Figure 8: Effect of biochar and biodigester effluent on water holding capacity |
|
Table 5: Mean values for effect of soil amender and level of effluent on height and green biomass weights of Taro (after 84 days from planting) |
||||||||
|
|
Height, cm |
No. of leaves |
Width of leave, cm |
Length of leave, cm |
Biomass yield , (g/plot) DM |
kg/ha, DM |
||
|
Leave |
Petiole |
Total |
||||||
|
Soil amender |
|
|
|
|
|
|
|
|
|
Biochar |
83.6a |
5 |
25.7 |
41.7 |
114.7a |
141.9 |
257a |
873a |
|
None |
75.6b |
4 |
23.4 |
38.1 |
72.3b |
96.4 |
169b |
574b |
|
Prob. |
0.02 |
0.28 |
0.07 |
0.09 |
0.01 |
0.06 |
0.02 |
0.02 |
|
SEM |
2.7 |
0.16 |
0.94 |
1.47 |
11.3 |
15.7 |
25.2 |
84.6 |
|
Level of effluent, kg N/ha |
|
|
|
|
|
|
||
|
0 |
77.4 |
4 |
23.9 |
38.8 |
85 |
97 |
182 |
619 |
|
50 |
78 |
5 |
24.1 |
39.4 |
102 |
116 |
218 |
742 |
|
100 |
83.4 |
5 |
25.6 |
41.7 |
94 |
144 |
237 |
809 |
|
Prob. |
0.33 |
0.49 |
0.51 |
0.48 |
0.68 |
0.26 |
0.47 |
0.47 |
|
SEM |
3.3 |
0.2 |
1.15 |
1.81 |
13.1 |
19.3 |
31.9 |
104 |
|
Prob. (interactions) |
|
|
|
|||||
|
S*E |
0.37 |
0.66 |
0.45 |
0.37 |
0.95 |
0.96 |
0.99 |
0.99 |
|
S: Soil amender, E: Effluent level, Prob: Probability The superscript ab in the same column is significantly different (P<0.05) |
||||||||
|
|
|
Figure 9: Effect of biochar on total biomass yield (1st harvest at 86 days) |
|
Table 6: Mean values for effect of soil amender and level of effluent on height and green biomass weights of Taro (after 112 days from planting) |
|||||||||
|
|
|
|
|
|
Biomass DM yield |
||||
|
|
Height, cm |
No. of leaves |
Width of leaf, cm |
Length of leaf, cm |
-----------g/plot----------- |
kg/ha |
|||
|
Leaves |
Petioles |
Total |
Total |
||||||
|
Soil amender |
|
|
|
|
|
|
|
||
|
Biochar |
93 |
4 |
27 |
44 |
215 |
167. |
3 |
1301 |
|
|
None |
86 |
4 |
25.4 |
41 |
150 |
110 |
261 |
886 |
|
|
Prob. |
0.05 |
0.52 |
0.23 |
0.24 |
0.01 |
0.04 |
0.02 |
0.02 |
|
|
SEM |
2.5 |
0.06 |
0.87 |
1.43 |
17.2 |
18.6 |
35.2 |
119 |
|
|
Level of effluent, kg N/ha |
|
|
|
|
|
|
|||
|
0 |
85 |
3 |
24.6 |
40.6 |
155 |
114 |
269 |
916 |
|
|
50 |
89 |
4 |
26 |
42 |
167 |
132 |
299 |
1018 |
|
|
100 |
94.5 |
4 |
28 |
46 |
226 |
170 |
396 |
1347 |
|
|
Prob. |
0.08 |
0.27 |
0.1 |
0.07 |
0.07 |
0.24 |
0.13 |
0.13 |
|
|
SEM |
3.06 |
0.07 |
1.07 |
1.75 |
21.1 |
22.9 |
43.3 |
147 |
|
|
Prob. (interactions) |
|
|
|
||||||
|
S*E |
0.34 |
0.2 |
0.26 |
0.63 |
0.07 |
0.15 |
0.33 |
0.1 |
|
|
S: Soil amender, E: Effluent level, Prob: Probability The superscript ab in the same column is significantly different (P<0.05) |
|||||||||
|
|
|||||||||
|
|
|
Figure 10: Effect of biochar on total biomass yield (2nd harvest at 112 days) |
|
Table 7. Mean values for biomass yield of Taro, with and without biochar, and increasing levels of biodigester effluent |
|||||||||
|
Biochar, tonnes/ha |
0 |
0 |
0 |
30 |
30 |
30 |
|||
|
N/ha, kg |
0 |
50 |
100 |
0 |
50 |
100 |
|||
|
1st harvest |
SEM |
P |
|||||||
|
kg DM,ha |
457 |
598 |
666 |
781 |
885 |
952 |
150 |
0.56 |
|
|
2nd harvest |
|||||||||
|
kg DM/ha |
646 |
948 |
1066 |
970 |
1187 |
1746 |
208 |
0.097 |
|
|
kg DM/ha/yr# |
5961 |
7798 |
8684 |
|
10178 |
11537 |
12413 |
|
|
|
# Predicted biomass yield, assuming the biomass yield at 112 days, after 28 days of regrowth, in projected to an annual basis |
|||||||||
The authors are very grateful to the MEKARN program funded by sida SAREC project, Sweden, for the support for this research.
.
Reference
AOAC 1990 Official methods of analysis. Association of Official Analytical Chemists, Arlington, Virginia, 15th edition, 1298 pp.
Chan K Y Van Zwieten L, Meszaros I, Downie A and Joseph S 2007 Using poultry litter biochars as soil amendments. Australian Journal of Soil Research 46(5) 437–444
Glaser B 2007 Prehistorically modified soils of central Amazonia: a model for sustainable agriculture in the twenty-first century. Philosophical Transactions of the Royal Society. 362, 187–196 http://rstb.royalsocietypublishing.org/content/362/1478/187.full
Houba V J C, Lee J J Van der, Novozamsky and Walinga 1988 Soil and Plant Analysis. Department of Soil Science and Plant Nutrition, WageningenAgricultural University. De Dreyen 3 Wageningen. The Netherland. http://ssc.undp.org/uploads/media/Acid.pdf
Inno Onwueme 1999 Taro Cultivation in Asia and the Pacific. Food and Agriculture organization of the United Nation (FAO). Regional office for Asia and the Pacific. Bangkok, Thailand. RAP publication: 1999/16
Jiang Gaosong, Ramsden L and Corke H 1996 Multipurpose uses of Taro (Colocasia esculenta). Review. In Proceedings of the Inter. Symposium held in Nanning, Guangxi, China. November 11-15, 1996. pp.262-265.
Lehmann J, Gaunt J and Rondon M 2006 Bio-char sequestration in terrestrial ecosystems—a review. Mitigation Adaptation Strategies. Global Change 11: 395–419 http://www.css.cornell.edu/faculty/lehmann/publ/MitAdaptStratGlobChange%2011,%20403-427,%20Lehmann,%202006.pdf
Onwueme I 1999 Taro cultivation in Asia and pacific. FAO of the United Nations, regional office for Asia and the Pacific. Bangkok, Thailand, 25 p.
Pedraza G, Chará J, Conde N, Giraldo S y Giraldo L 2002 Evaluación de los biodigestores en geomembrana (pvc) y plástico de invernadero en clima medio para el tratamiento de aguas residuales de origen porcino. Livestock Research for Rural Development. Volume 14, Article No. 2 http://www.lrrd.org/lrrd14/1/Pedr141.htm
Raemaekers R H 2001 Crop production in tropical Africa, 23-45, 221-229.
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
San Thy, Preston T R and Ly J 2003 Effect of retention time on gas production and fertilizer value of biodigester effluent. Livestock Research for Rural Development 15 (7). http://www.lrrd.org/lrrd15/7/sant157.htm
Sisomphone S and Preston TR 2011Growth of rice in acid soils amended with biochar from gasifier or TLUD stove, derived from rice husks, with or without biodigester effluent . http://www.lrrd.org/lrrd23/2/siso23032.htm
Sohi S, Loez-Capel E, Krull E and Bol R 2009 Biochar's roles in soil and climate change: A review of research needs. CSIRO Land and Water Science Report 05/09, 64 pp.
Undersander D, Mertents D R The ix N 1991 Forage analysis Procedures. National Forage Testing Association, Amaha 154
Wang J K 1983 Taro, a review of Colocasia esculenta and its potential. University of Hawaii Press. pp. 300-312.
