Effect of biochar and biodigester effluent on growth performance of taro (Colocasia esculenta)

Souksakhone Vivasane, Sisomphone Southavong, Phetsamay Vyraphet and T R Preston*

Champasack University
Champasack province, Lao PDR
svivasane@yahoo.com
* Finca Ecológica, TOSOLY, UTA (Colombia)
AA #48, Socorro, Santander, Colombia

Abstract

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.

Application of biochar increased biomass yield of taro by 46, 42 and 84% at each of three successive harvests, the first after 84 days growth and the 2nd and 3rd at subsequent intervals of 28 days. There were linear responses in yield to biodigester effluent up to 100 kg N/ha, the increases when biochar was applied being 19, 75 and 84% at succeeding harvests. Responses in the absence of biochar were 33, 67 and 36% at successive harvests. Predicted annual yields per ha with biochar and 100 kg N effluent were 22.8 tonnes of DM and 2.9 tonnes of crude protein. 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 and level of effluent.

Key words: biomass, rice husk, soil pH, water holding capacity

Introduction

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 (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 2006) 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 (2010). 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 (2007) 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.  Southavong and Preston (2011) 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.

Hypothesis 

• 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 fertility

Materials and methods

Location 

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 October 2011 and May 2012, the mean air temperature of 28.2°C and average annual rainfall of 2000mm/year.

Experimental design 

The experiment was arranged in a Randomized Complete Block Design (RCBD) as 2*2 factorial with 4 replications, the factors were: 

·         Biochar: With or without at 3 kg/m².

·         Effluent: 0, 50 and 100 kg N/ha. 

The individual treatments were: 

• B3E0:              Biochar at 3 kg/m² + Biodigester effluent 0 kg N/ha.
• B3E50:            Biochar at 3 kg/m² + Biodigester effluent 50 kg N/ha.
• B3E100:          Biochar at 3 kg/m² + Biodigester effluent 100 kg N/ha.
• B0E0:              Biochar at 0 kg/m² + Biodigester effluent 0 kg N/ha.
• B0E50:            Biochar at 0 kg/m² + Biodigester effluent 50 kg N/ha.
• B0E100:          Biochar at 0 kg/m² + Biodigester effluent 100 kg N/ha.

Land preparation, plot size and seeding of Taro 

Twenty four plots were prepared by two wheel 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. 

Fertilizing 

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.

Measurements 

Measurements were made of height, width and number of leaves at weekly intervals until harvest. Soil pH and dry matter were recorded at the beginning and at the end of the trial. 

Harvesting 

The first harvest was made 84 days after planting and continued with the second and third harvest at 28 day intervals. All the mature leaves and petioles were removed leaving the two youngest to facilitate the re-growth. 

Statistical analysis

The data were 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. 

Results and discussion

Data on some attributes of the soil, biochar and effluent are in Table 2a. The N content of the effluent was rather low probably because of the quantity of water used in washing the pig pens.

On a DM basis, the leaves and petioles of the taro were equally balanced (Table 2b).

Effect of biochar and effluent on Taro biomass yield

Biomass yield of taro at the first harvest 84 days after planting and at subsequent harvests at 112 and 140 days was increased by the application of biochar, and was higher at the second and third harvests (Tables 3, 4 and 5; Figures 1 to 3). The yield response to level of biodigester effluent was linear at all three harvests except for the no biochar treatment in the third harvest when there were no differences in yield due to effluent level (Figure 3). These responses with taro are similar to those reported by Southavong et al (2012a) with water spinach when effluent was applied at 5 different levels (0, 25, 50, 75 and 100, N kg/ha) in combination with biochar at 0 or 40 g/m². This effect of biochar is agreement with reports by Sombroek et al (2003), Glaser et al (2002), Lehmann and Glaser (2003), Lehmann and Rondon (2005) and Lehmann (2007) that when biochar is applied to soil it helps to retain the nutrients which remain available to plants thus increasing the plant growth and yield.

Water-holding capacity and pH of the soil 

Biochar improved the soil water holding capacity by 15% (Table 6 and Figure 5) but there were no differences with level of biodigester effluent. The level of improvement with biochar was similar considerably lower to the value reported by Southavong et al (2012b) when 4% (by weight) biochar was added to the soil. This probably due to the amount of the biochar added to soil in the present study was lower (3% by weight). Chan et al (2007) showed that biochar application improved some physical properties of soils, such as increased soil aggregation and water holding capacity.

It has been already identified that biochar applied to soils improves the availability of phosphorus, total nitrogen and major cations (Glaser et al 2002; Lehmann and Glaser 2003). Additionally, biochar has positive liming effect when applied to low pH soils (Van Zwieten et al 2007), thereby the application of biochar to acidic soils increases the soil pH and therefore improves nutrient use efficiency. Our study showed the improvement in soil pH when biochar was added to acid soil at 3 kg per m² or 30 tonnes per ha (Table 6; Figure 4),

Annual yields of DM and crude protein are predicted in Table 7, on the basis of the recorded yields after 28 days of re-growth in the second harvest. At the highest level of biodigester effluent and with addition of biochar, annual yield of DM was estimated at 22.8 tonnes/ha and of crude protein at 2.9 tonnes/ha. These predicted annual yields are higher that were reported by Rodriguez and Preston (2009) for new Cocoyam (Xanthosoma sagitarrius) which were 14.5 tonnes of DM/ha and 1.8 tonnes of crude protein/ha. In Hue province in Vietnam taro species (Colocasia esculenta) planted in the lowland and coastal areas were reported to yield up to 273 tonnes/ha/year of fresh biomass, equivalent to 32 tonnes/ha of DM.

Conclusions

• Biomass yield of taro was increased by 46, 42 and 84% at each of three successive harvests, the first after 84 days growth and the 2nd and 3rd at subsequent intervals of 28 days.
  
  
• There were linear responses in yield to biodigester effluent up to 100 kg N/ha, the increases when biochar was applied being 19, 75 and 84% at succeeding harvests. Responses in the absence of biochar were 33, 67 and 36% at successive harvests.
  
  
• Predicted annual yields per ha with biochar and 100 kg N effluent were 22.8 tonnes of DM and 2.9 tonnes of crude protein.
  
  
• 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 and level of effluent.

Acknowledgement

The authors are very grateful for the support received from the MEKARN program funded by Sida, Sweden. We also would like to thank Champasack University for access to facilities and the experimental site. Mr Douayang Noryeng and Mr. Onsy Xayyalath, students of the Faculty of Agriculture, provided valuable help in data collection and taking care of the experiment. 

References

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, Lehmann J and Zech W 2002 ‘Ameliorating physical and chemical properties of highly weathered soils in the tropics with charcoal –A review’. Biology and Fertility of Soils. 35, 219–230.

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 of London Series B: Biological Sciences 362, 187–196.

Jiang Gaosong, Ramsden L and Corke H 1996 Multipurpose uses of Taro (Colocasia esculenta). Review. In Proceedings of the International Symposium held in Nanning, Guangxi, China. November 11-15, 1996. pp.262-265.

Lehmann J and Glaser B 2003 ‘Nutrient availability and leaching in an archaeological Anthrosol and a Ferralsol of the Central Amazon basin: fertilizer, manure and charcoal amendments’, Plant and Soil 249, 343–357.

Lehmann J and Rondon M 2005 ‘Bio-char soil management on highly-weathered soils in the humid tropics’, in N. Uphoff (ed.), Biological Approaches to Sustainable Soil Systems, Boca Raton, CRC Press, in press.

Lehmann J, Gaunt J and Rondon M 2006 Bio-char Sequestration in Terrestrial in Ecosystem – A Review. Mitigation and Adaptation Strategies for Global Change (2006) 11: 403–427. Springer 2006.

Lehmann J 2007 Bio-energy in the black. Front Ecol Environ 2007; 5(7): 381–387. http://www.google.la/url?sa=t&rct=j&q=lehman+bioenergy+in+the+black&source=web&cd=1&ved=0CFMQFjAA&url=http%3A%2F%2Fwww.css.cornell.edu%2Ffaculty%2Flehmann%2Fpubl%2FFrontiersEcolEnv%25205%2C%2520381-387%2C%25202007%2520Lehmann.pdf&ei=S7O7T-7HHuSPiAf9vMz-CA&usg=AFQjCNGq7oN2rOKTKM194D_kxAE00UTGiQ

Minitab 2000 Minitab Release 13.31 for windows, Windows* 95/98/2000/xp. Minitab Inc., State College Pennsylvania, USA.

Onwueme I 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

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 and Preston T R 2009: Effect of planting method on biomass yield of New Cocoyam (Xanthosoma sagittifolium). Livestock Research for Rural Development. Volume 21, Article #137. http://www.lrrd.org/lrrd21/8/rodr21137.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

Sohi S P, Krull E, Lopez-Capel E and Bol R 2010 A review of biochar and its use and function in soil. Advances in Agronomy 105, 47–82.

Sombroek W, Ruivo M L, Fearnside P M, Glaser B and Lehmann 2003 Amazonian Dark Earths as carbon stores and sinks. In: Lehmann J, Kern D C, Glaser B, and Woods W I (Eds). Amazonian Dark Earths: origin, properties, management. Dordrecht, Netherlands: Kluwer Academic Publishers.

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. http://www.lrrd.org/lrrd23/2/siso23032.htm

Southavong S, Preston T R and Man N V 2012a: Effect of soil amender (biochar or charcoal) and biodigester effluent on growth of water spinach (Ipomoea aquatica). Livestock Research for Rural Development. Volume 24, Article #26. http://www.lrrd.org/lrrd24/2/siso24026.htm

Southavong S, Preston T R and Man N V 2012b: Effect of biochar and charcoal with staggered application of biodigester effluent on growth of water spinach (Ipomoea aquatica). Livestock Research for Rural Development. Volume 24, Article #39. http://www.lrrd.org/lrrd24/2/siso24039.htm

Undersander D, Mertens D R and Theix N 1993 Forage analysis procedures. National Forage Testing Association. Omaha pp 154.

Van Zwieten L, Kimber S, Downie A, Chan K Y, Cowie A,Wainberg R, Morris S 2007 Paper mill char: benefits to soil health and plant production. In: International Biochar Initiative Conference, Terrigal, Australia, 30 April–2 May 2007.

Wang J K 1983 Taro, a review of Colocasia esculenta and its potential. University of Hawaii Press. pp. 300-312.

Received 24 May 2012; Accepted 28 May 2012; Published 1 June 2012

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