Effect of different levels of effluent on growth and composition of water spinach grown in beds with high and low mixtures of cattle manure and soil

Nguyen Van Hiep

Nong Lam University, Viet Nam
nguyenvanhiep5@yahoo.com

Introduction

Water spinach (Ipomoea aquatica ) has a very high biomass yield. It is used traditionally in tropical regions for consumption by people and animals. Using water spinach as a protein source for Ba Xuyen and Large White sows has given good results in feed intake and digestibility (Le Thi Men et al 1999). Water spinach has a short growth period and is resistant to common insect pests. It can grow both in soil and in water and it is very easy to grow by farmers. The traditional practice is to use urea as fertilizer but price of urea is expensive in the recent years.

Observations in Colombia indicate that water spinach has a high need of organic matter in the soil in order to grow well. Vegetables require many nutrient elements for good growth and production, but N, P and K are three elements of most concern. Leafy vegetables are especially heavy users of nitrogen such as water spinach. The maximum biomass yield was obtained with 30 kg N of urea/ha according to Luyen and Prestonnes (2004).

Biodigester effluent charged with pig manure is high in N sources and cattle manure is a good source of organic matter. Both are very cheap in price and can be applied easily to water spinach in the local area. Biodigester effluent at 75 kg N/ha was supported the same fresh biomass yield of water spinach as urea at the same N application rate (Kean Sophea and Prestonnes 2001).

Hypothesis

The response of water spinach to fertilization with biodigester effluent will be greater when it is grown on beds with high content of cattle manure.

Objective

This study evaluates the effect of different levels of effluent from a biodigester charged with pig manure and the interaction with low and high cattle manure levels on growth and composition of water spinach.

Materials and methods

The study will be arranged as a completely randomized block design (CRBD) with 2 factors. The man factor is cattle manure with 2 levels (20 and 40 tonnesnes/ha) which will be used mixed in the  soil before seeding the water spinach. The other factor is N from biodigester effluent with 5 levels (0, 10, 20, 30 and 40 kg/ha) which will be applied 20% at first week, 40% at second week and 40% at the third week. The biodigester effluent will be divided to apply each day with the same quantity.

Treatments:

• LM00N: 20 tonnes cattle manure/ha + 0 N kg biodigester effluent/ha

• LM10N: 20 tonnes cattle manure/ha + 10 N kg biodigester effluent/ha

• LM20N: 20 tonnes cattle manure/ha + 20 N kg biodigester effluent/ha

• LM30N: 20 tonnes cattle manure/ha + 30 N kg biodigester effluent/ha

• LM40N: 20 tonnes cattle manure/ha + 40 N kg biodigester effluent/ha

• HM00N: 100 tonnes cattle manure/ha + 0 N kg biodigester effluent/ha

• HM10N: 100 tonnes cattle manure/ha + 10 N kg biodigester effluent/ha

• HM20N: 100 tonnes cattle manure/ha + 20 N kg biodigester effluent/ha

• HM30N: 100 tonnes cattle manure/ha + 30 N kg biodigester effluent/ha

• HM40N: 100 tonnes cattle manure/ha + 40 N kg biodigester effluent/ha

There are 3 replications of each treatment arranged within 3 blocks. The plot size is 1m² with a space of 50 cm between plots (Diagram 1).

Diagram 1: Layout of experiment

Block 1	LM40N	HM10N	HM20N	HM40M	LM10N	LM0N	LM30N	LM20N	HM0N	HM30N
Block 2	HM40N	HM10N	HM0N	LM40N	HM30N	LM20N	HM20N	LM0N	LM30N	LM10N
Block 3	HM40N	HM0N	LM10N	HM20N	LM30N	LM40N	HM10N	LM0N	LM20N	HM20N

     Low cattle manure (2 kg/m²)                            High cattle manure (10 kg/m²) 

                  0N, 10N, 20N, 30N, 40N: biodiogester effluent levels

Land preparation

The soil will be cultivated by hoe, raising beds 15 cm high and separating the plots. To each soil plotcattle manure  will be applied before seeding.

Planting and management

The water spinach seed rate is 60 g/m²; they will be planted in rows at spacing 5 cm and 2-3 cm depth. The low biodigester effluent volume treatments will be supplemented water to balance with the highest biodigester effluent volume treatment.

Measurements

Biodigester effluent sample will be analyzed for N content to calculate effluent volume for each treatment. Soil samples at the beginning will be collected for analysis of DM, OM and N. Germination and color of plant will be observed every day. Plant height (from the bottom to top) and leaf length of water spinach will be measured every 4 days. The biomass will be harvested at 28th days and immediately separated into leaves and stems to analysis DM content (60^oC). These leaves and stems samples will be ground with a coffee grinder and analyzed for  DM content by micro-wave radiation(UNdersander etal 1993). OM and N are analysed according to AOAC (1990).  Water soluble DM is done by the method of Ly and Preston (1997.

Statistical analysis

The data will be analyzed by ANOVA using the software of Minitab version 13. Sources of variation are: level of manure, level of N in effluent and interaction Manure*effluent N, blocks and error

Work plan

	Sep 12 and 13	Sep 14	Sep 15	Sep 16 - 19	Sep 19, 22, 25, 28, Oct 1, 4, 7, 10, 13	Sep 21 and 28	Oct 14 and 15	Oct 16 - 21
land preparation	**
effluent sample analysis and fertilization		*
Seeding			*
Germination observation				****
Height measurement					*********
Effluent apply