Soil bio-test to evaluate comparative fertility of the soils and effect of adding earth worm compost
 

Tran Thi Bich Ngoc

National Institute of Animal Husbandry, Hanoi, Vietnam
bichngocniah75@hotmail.com

Introduction

Knowing the fertility of soils is important in agriculture particularly in making decisions on planting of crops. The measurement of the fertility of soils is usually done by chemical analysis for plant nutrients such as nitrogen (N), potassium (K), phosphorus (P) and trace elements, as well as physical measurements of soil structure. Such analyses require access to a laboratory and this is not feasible for most farmers, especially those with limited resources. Planting some indicator plants in the soil and measuring their growth and production is one way to measure fertility of soils in an indirect way (Nguyen Phuc Tien et al 2003, cited by Boonchan Chantaprasarn 2003).

Worm compost is a valuable fertilizer and sol conditioner. It is reported that earthworm castings contain over five times the available nitrogen, eleven times the phosphorus, three times the exchangeable magnesium, eleven times the potash, and one-and-a-half times the lime (calcium) found in good topsoil. (http://www.worldwise.com/soilferandfe.html).  Another report indicates that to mulch with worm compost, apply a one-inch layer to the soil around the plants, and be sure the worm compost is not piled against plant stems. To amend soils, worm compost can be spread one half to two inches thick over garden soil and mixed in before planting, or mixed into the bottom of seeding trenches or transplanting holes.(http://www.deq.state.ok.us/factsheets/local/worms.pdf)

The maize bio-test is suitable for evaluation of soil fertility according to Chamnanwit Promkot (2001) and Boonchan Chantaprasarn (2003). The maize was better than rice as an indicator plant to compare the fertility of different soils (Boonchan Chantaprasarn 2003). Therefore, in this experiment, maize will be chosen as bio-test indicator plant for measuring fertility of soils

Hypothesis

Mixing of worn compost with the soil samples will increase the growth of maize but the increase will depend on the basic fertility of soils that are chosen.

Objectives

The maize biotest will be used to evaluate the relative fertility of four types of soils and the effect of using different levels of earth worm compost.
 

Materials and methods

Location

The experiment will be carried out in the Livestock Research Center, Nang Xuan village, Lao during 35 days starting on 15 September 2005.

The experimental design

The treatments are source of soils (S) and levels of earth worm compost (EC) arranged in a 4*4 factorial with 4 replications, in a completed randomized block design (CRB). The factors are:

Types of soil

• Sand (S) in LRC
• Poor soil in garden near to LRC (P)
• Medium soil in border river near to LRC (M)
• Good soil in rice field near to LRC (H)

Level of worm compost (EC)

• 0%EC
• 10% EC; 90% soil
• 20% EC; 80% soil
• 30% EC; 70% soil

The experimental layout of the plots is in Table 1.

Table 1: Experimental layout
Block 1	PEC20	EC0	MEC20	PEC10	EC30	EC10	MEC10	PEC0
	HEC20	EC20	HEC10	HEC30	MEC0	PEC30	MEC30	HEC0
Block 2	PEC0	MEC0	EC10	MEC10	HEC20	EC30	PEC20	EC20
	EC0	HEC30	HEC0	MEC30	PEC30	PEC10	MEC20	HEC10
Block 3	HEC30	EC0	PEC20	EC30	MEC30	HEC10	HEC20	EC10
	PEC0	MEC10	EC20	PEC30	MEC0	PEC10	MEC20	HEC0
Block 4	PEC20	EC30	PEC10	MEC10	HEC30	EC0	MEC30	PEC0
	EC10	MEC0	EC20	HEC20	HEC10	MEC20	HEC0	PEC30

Procedure

The substrates will be put into plastic bags (capacity 1 litre). Three seeds of maize will be planted in each bag according to the experimental layout in Table 1. After germination, plants will be removed to leave only one maize plant in each bag. Many holes will be put around each bag so the excess water can drain away. Water will be applied uniformly to all bags every morning and evening. Color of plant, soil, germination and growth of plants will be observed every day.

Measurements

The dry matter (DM), organic matter (OM) and N of soils and earth worm compost will be analyzed at the beginning and in the substrates at the end. The height of the plants will be measured every 5 days over a total period of 35 days. After 35 days, the plants and roots will be removed from the bags, washed free of soil, and weighed 30 minutes later, the green parts (leaves and stems) and the roots separately.

Laboratory analyzes

AOAC (1990) methods will be used to determine N and ash. DM will be by micro-wave radiation (Undersander et al 1993)..

Statistical analyzes

The linear regression of height on days will be calculated to determine growth rate in height. The ANOVA GLM option of the Minitab software will be used to analyze the data. Ssources of variation are: soils, level compost, interaction soils*compost, blocks and error. The Tukey test in the Minitab software will be used to separate mean values when the F-test is significant at P<0.05.
 

References

AOAC 1990 Official methods of analysis. Association of Official Analytical Chemists, Arlington, Virginia, 15^th edition, 1298 pp.

Boonchan Chantaprasarn 2003 Measuring fertility of soils by the bio-test method. MEKARN Miniprojects 2003-2005 http://www.mekarn.org/msc2003-05/miniprojects/webpage/cont_mp.htm

Chamnanwit Promkot 2001 Study of the use of maize and water spinach in a biotest for evaluation of soil fertility. MEKARN Miniprojects 2001-2003 http://www.mekarn.org/minipro/cham.htm

Debra Lynn Dadd  Soil fertility and fertilizer, http://www.worldwise.com/soilferandfe.html

Minitab 1993 statistical software Version 13.3.

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

Worm composting http://www.deq.state.ok.us/factsheets/local/worms.pdf