s

In Cambodia, vegetables are the pivotal source of food and income for rural families. To grow them, chemical fertilizers need be used. Recently, the price of fuel has highly increased and so has the price of commercial fertilizers. It is a constraint for farmers to buy them for their crops. To solve this, farmers should use low cost organic fertilizers. Besides, farmers can use fine-grained charcoal (biochar) to add to the soil because charcoal fertilization can permanently increase soil organic matter content and improve soil quality, persisting in soil for hundreds to thousands of years. Soils receiving charcoal produced from organic wastes were much looser, absorbed significantly more water and nutrients and produced higher crop biomass. The results demonstrate that charcoal amendment is a revolutionary approach for long-term soil quality improvement (Marsh and Bernstein 2008). Biochar is traditionally produced in smoky kilns from biomass (wood, plants, organic residue such as tree leaves and wood chips) heated in the absence of oxygen through a process called pyrolysis (SSC 2008) or in a gasification system. From recent field experiments, biochar also appears to have potential to provide further climate benefits by reducing nitrogen fertilizer requirements, as well as cropland nitrous oxide and methane emissions from soil (Swift and Roger 2001). In a nutshell, Bio-char can act as a soil conditioner enhancing plant growth by supplying and, more importantly, retaining nutrients and by providing other services such as improving soil physical and biological properties (Glaser et al 2002; Lehmann et al 2003; Lehmann and Rondon 2005).

On the other hand, effluent is one kind of nutrient-rich fertilizer which is the liquid waste from low cost biodigester that farmers can set up for multipurpose utilization in their family. When applied to vegetables and plants, we will get higher biomass yield and content of moisture and crude protein such as on Chinese cabbage (San Thy and Pheng Buntha 2005) water spinach (Kean Sophea and Preston 2001, Ho Bunyeth and Preston 2004) and cassava (Le Ha Chau 1998).

What is the difference between effluent and biochar? If these two fertilizers are applied together on the crops, what will happen? Therefore, a research on the use of effluent and biochar as fertilizer for water spinach will be conducted.

Hypothesis

When used as fertilizer, Biochar can act as a soil conditioner enhancing water spinach growth by supplying and retaining nutrients and by improving soil physical and biological properties. Effluent can increase biomass yield and content of crude protein of water spinach and their quality too. When mixing together these two kinds of fertilizers, water spinach will growth well and gain higher biomass and better quality.

Objectives

Materials and methods

Location

The experiment will be conducted for 20 days in the experimental farm of Kampong Cham National School of Agriculture.

Materials

The biochar was brought from Columbia by gasification system. The effluent can be found from biodigester in the experimental farm of Kampong Cham National School of Agriculture. The soil used in the trial is the poor soil taken from the farm field of Kampong Cham National School of Agriculture. Water spinach seeds are bought from the market.

Experimental design

The experiment will be designed as 2*2 factorial arrangements with 4 replications, in a completely randomized block design (CRBD).

Table 1: experimental layout
Block 1	BCE	BE	C	BC
Block 2	BE	BC	BCE	C
Block 3	C	BC	BCE	BE
Block 4	BCE	BE	C	BC

Procedure

Cultivation preparation

The 20 kg of poor soil will be put into the plastic baskets (size about 37*51cm) according to the experimental layout in table 1. Some seeds (60 seeds) of dry-land water spinach species will be planted in baskets. The distance between rows will be 10cm. The baskets are set up with the net so that the excess water can drain away easily. The water will be applied uniformly to all baskets every morning and evening. In the case of raining, water will not be applied. Color of plant, germination and growth of plants will be observed every day.

Fertilizing

The biodigester effluent will be applied at the beginning and every 5 days for 30 days for a total of 6 times during the growing period for certain groups. The effluent is from a biodigester charged with pig manure.

Data collection

Plant height will be measured every 5 days before applying the effluent. The measurement will be done on a random number of plants (10 plants/basket). The water spinach will be harvested at 30 days after planting. All plants will be separated into stem and leaf and after weighing the two components, samples will be analyzed immediately to determine dry matter by microwave radiation (Undersander et al 1993), N (AOAC 1990) and water extractable DM and N (Ly and Preston 1997).

Laboratory analysis

The sample of soil will be analyzed for DM, N, pH, ash and the sample of biochar will be analyzed for only ash.

Statistical analysis

The data will be analyzed by Analysis of variance (ANOVA) using the General Linear Model (GLM) procedure of the Minitab software (version 13.3). Sources of variation will be: biochar, effluent, interaction of biochar*effluent, blocks and error.

Reference

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

Glaser, B., Haumaier, L., Guggenberger, G. and Zech, W.: 2001, ‘The Terra Preta phenomenon – A

model for sustainable agriculture in the humid tropics’, Naturwissenschaften 88, 37–41.

Lehmann, J., da Silva Jr., J.P., Steiner, C., Nehls, T., Zech, W. 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

Ly J and Preston T R 1997 An approach to the estimation of washing losses in leaves of tropical trees. Livestock Research for Rural Development (9)3: http://cipav.org.co.lrrd/lrrd13/1/ly131.htm

Swift, Roger S 2001 Sequestration of Carbon by Soil, Soil Science, November 2001, Vol 166, No. 11, pages 858 – 871.

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

Effluent and biochar as fertilizer for water spinach

Kong Saroeun

Center for Livestock and Agriculture Development (CelAgrid)

Kandal province, Cambodia

Introduction