Comparison of worm compost and biodigester effluent as fertilizer for water spinach
 

Latsamy Phounvisouk

Living Aquatic Resource Research Center
NAFRI, Vientiane, Lao
meetouna@yahoo.com

Introduction

The economy in Lao is largely based on agriculture. Approximately 80% of the population live in rural areas and grow rice as their staple crop. Vegetable production is second in importance in Lao and is mainly in lowland areas, and other regions near the rivers, where the soils are very fertile. At the LRC the soil is very poor. Therefore, the intensive cultivation and improvement of  productivity per unit area is a key factor. Research on plantslant such as water spinach (Ipomoea aquatica) is important because this plant has a very high biomass yield. Water spinach has a short growth period and is resistant to common insect pests and is a variable water and marsh plant, rich in protein that is traditionally planted as a vegetable in many tropical countries (AFRIS 2005). It is used traditionally in tropical regions for consumption by people and animals. Using water spinach as a protein source for BaXuyen pigs and Large White sows have given good results in feed intake and digestibility (Le Thi Men et al 1999). Yield of water spinach biomass showed a linear response to application of biodigester effluent up to 140 kg N/ha (Kean Sophea and Preston 2001).

Recycling pig or cattle manure through biodigesters gives rise to an effluent which was shown to be superior in fertilizer value to the original manure (Le Ha Cha 1998a, b). Another organic fertilizer is worm compost which was was superior to urea in promoting biomass growth and crude protein content of water spinach. Iin contrast to use of urea, application of worm compost had beneficial effects on soil fertility when this was measured biologically and chemically (Tran Hoang Chat et al 2005). Worm compost is more concentrated than most other organic fertilizers, because of the way worms digest food waste and amend the soil. It is valuable for  fertilizing house plants and for mixing with potting mixes (Hopp and Slater 1949).

Hypothesis

Objective

This is to determine the effect of supplementary N fertilizer levels on growth of water spinach using earth worm compost and biodigester effluent as the fertilizer.
 

Material and methods

Location

The experiment will be conducted at the Livestock Research Centre, Vientiane province of Laos starting on September 15 2005, and lasting 35 days.

Design and treatments

There are two factors in a 5*2 split plot arrangement  These are:

Sources of fertilizer are the main plots

• Earth worm compost (EC)

• Biodigester effluent (BE)

Level of N fertilizer (kg N/ha) is the split plot

• 0

• 10

• 20

• 30

• 40

There are 3 replications in a random block arrangement (see below)

1	Fertilizer N, kg/ha	10	40	20	30	0
		EC	BE	EC	BE	EC
		BE	EC	BE	EC	BE
2	Fertilizer N, kg/ha	20	10	0	40	30
		EC	EC	BE	BE	BE
		BE	BE	EC	EC	EC
3	Fertilizer N, kg/ha	0	40	30	20	10
		EC	EC	EC	BE	BE
		BE	BE	BE	EC	EC

Land preparation, planting, fertilizing and irrigation

Thirty baskets will be used.  The water spinach will be planted from seed (60g/m²) with spacing between seeds of 1-2 cm at 2 cm depth. The distance between rows will be 5-7 cm.  The distance between plots will be 50 cm. For effluent treatment, the effluent will be applied 3 times in the growing period, the quantities being 1 litre daily20%, 40% after 1 week and 40% after 2 weeks. In each case diluted with water. Baskets will be watered each day with same quantity for each treatment. The effluent has 100 mg N/litre, and the compost has 0.79% N (DM basis) and the DM content is 56% the total quantities are then:

Litres effluent	g of compost,g
1.6	36
3.2	72
4.8	108
6.4	145

 

Measurements

The length of leaves and stems of water spinach will be measured every 3 days /time. The color of water spinach will be observed everyday, and measured germination rate (daily over first 7 days). First harvest will be made at 28 days after planting. All water spinach in individual basket will be weighed. Leaf and stem will be separated for determination of leaf: stem ratio. Samples of each will be collected at random and analyzed for DM, OM, N and water soluble DM and N.

The compost will be analyzed for total N, OM and DM. Samples of soil will be taken from each plot before planting and after harvesting for determination of OM, N, and DM.

Analyses

AOAC 1990 methods will be used to analyze OM and N retention in both leaves and stems of water spinach and in earthworm compost or bio-digester effluent. DM is measured by micro-wave radiation (Undersander et al 1993). Water extractab le DM and N will be determined by th method of Ly and Preston (1997).

Statistical analysis

The data will be analysed by ANOVA using the General Linear Model (GML) software of Minitab (Version Release 13.2). Sources of variation are sources of fertilizer, levels of N, interaction fertilizer*N level, blocks and error
 

References

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

AFRIS 2005 Animal Feed Resources Information System, FAO, Rome. Retrieved June 7, 2005, from http://www.fao.org/ag/AGA/AGAP/FRG/afris/default.htm

Hopp H and Slater C S 1949 The effects of earthworms on the productivity of agricultural soil." Jour. Agri. Research 78:325-339.

Kean Sophea and Preston T R 2001 Comparison of biodigester effluent and urea as fertilizer for water spinach vegetable. Livestock Research for Rural Development 13 (6). Retrieved June 7, 2005 from, http://www.cipav.org.co/lrrd/lrrd13/6/kean136.htm

Le Ha Chau 1998a Biodigester effluent versus manure from pigs or cattle as fertilizer for production of cassava foliage (Manihot esculenta). Livestock Research for Rural Development. Volume 10, Number 3, December 1998. Retrieved June 7, 2005 from,http://www.cipav.org.co/lrrd/lrrd10/3/chau1.htm

Le Ha Chau 1998b Biodigester effluent versus manure, from pigs or cattle, as fertilizer for duckweed (Lemna spp.) Livestock Research for Rural Development. Volume 10, Number 3, December 1998. Retrieved June 7, 2005 from.http://www.cipav.org.co/lrrd/lrrd10/3/chau1.htm

Le Thi Men, Ogle B and Vo Van Son 1999 Evaluation of water spinach as a protein source for Baxuyen and Large White sows fattening crossbred pigs. MSc thesis, Swedish University of Agricultural Sciences, Uppsala

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://www.cipav.org.co/lrrd/lrrd13/1/ly131.htm

Tran Hoang Chat, Ngo Tien Dung, Dinh Van Binh and Preston T R  2005: Effect on yield and composition of water spinach (Ipomoea aquatica), and on soil fertility,  of fertilization with worm compost or urea.  Livestock Research for Rural Development. Volume 17, Article # 108. Retrieved, from http://www.cipav.org.co/lrrd/lrrd17/10/chat17108.htm

Undersander D, Mertens D R and Lewis B A 1993. Forage analysis procedures. National Forage Testing Association. Omaha pp 154