Measuring fertility of soils by the bio-test method

Boonchan  Chantaprasarn

Dairy Farming Promotion Organization of Thailand (DPO)
Northeast branch, 344 Moo 15 Thapra, Muang, Khon Kaen, 40260, Thailand
chantaprasarn@yahoo.com

Khon Kaen University, Muang, Khon Kaen, 40000, Thailand

Abstract

The experiment was conducted at An Giang University, Viet Nam. Eight kinds of soil were taken from different places around An Giang University to measure fertility of soils by using the bio-test with maize (Zea mays) and rice (Oryza sativa) as indicators, according to a  8x2 factorial arrangement  with three replications. The soils were sand (negative control) , clay soil, loam mixed with compost 1:1, loam with leaves and compost from the shade under the trees, sandy loam, sub-soil under loam, sub-soil under sandy loam (sub-soil taken at  more than 20 cm. depth) and compost (positive control).  The soil samples were put into 2 liters capacity plastic bags and 3 seeds of either maize or rice was planted in each bag (3 bags per soil/indicator plant). Date to germination, plant height at every 5 days intervals and final weight of biomass after 28 days were measured.

There were significant differences between soils in the growth in height and the amount of biomass of both the maize and rice after 28 days, and a significant interaction for soil * plant for both measurements.  Physical composition of soil was positively correlated to plant growth particularly in maize. For maize, there is a positive curvilinear response of biomass weight to level of organic matter and percentage of N in the soils (R²= 0.67 and 0.92), but no response in rice (R²= 0.03 and 0.015).

It is suggested that measuring fertility of soils by the bio-test method is a simple, practical and low cost procedure in integrated farming systems. The maize bio-test indicator was better suited to measuring fertility of soil than rice.        

Key words: Bio-test method, maize, organic matter, pH, rice, soil fertility
 

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).

Organic matter is partially decayed plant and animal matter (www.heinzctr.org/ecosystems/farm/soil_slnt.shtml). It helps the soil hold water and supplies nutrients, which are crucial for crop production; it also protects against erosion and helps support a healthy and diverse set of microscopic plants and animals. Organic matter content, erosion, soil salinity, and soil biological condition are key indicators of soil quality, reflecting the effect of agriculture on soils and the influence of changing crop and soil management practices.
 (www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex890?opendocument).

pH is a measure of how acidic or basic is the soil and is measured using a pH scale between 0 to 14, with acidic media having a pH between 0-7 and basic media having a pH from 7 to 14. For instance, lemon juice and battery acid are acidic and fall in the 0-7 range, whereas seawater and bleach are basic (also called "alkaline") and fall in the 7-14 pH range. Pure water is neutral, or 7 on the pH scale. The pH of soil or more precisely the pH of the soil solution is very important because soil solution carries in it nutrients such as nitrogen (N), potassium (K), and phosphorus (P) that plants need in specific amounts to grow, thrive, and fight off diseases (ltpwww.gsfc.nasa.gov/globe/nftg/nftgame.htm).

Maize (Zea mays) is widely cultivated in the tropics and sub-tropics for both human and animal feed. It requires a long, warm period to ripen the grain and cannot withstand frost. There are many types of maize and the grain may be yellow, white or red. (file:///D:/www.fao.org/ag/aga/agai/far/afris/data). The maize bio-test is suitable for evaluation of soil fertility (Promkot, 2001).

Rice (Oryza sativa) is intimately involved in the culture as well as the food ways and economy of many societies. Rice is grown on farms under conditions only slightly different from those to which wild rice was subject. The growth duration of the rice plant is 3 to 6 months, depending on the variety and the environment under which it is grown.
(file:///D:/chan/Documents%20and%20Settings/T%20R%20Preston/My%20Documents/MEKARN/msc2003/miniprojects/chan/www.riceweb.com).

In this experiment, maize and rice were chosen as bio-test indicator plants for measuring fertility of soils.

Materials and Methods

Treatments

There were two sets of treatments (types of soil and indicator plants), arranged as a 8*2 factorial with 3 replications in a Randomized Complete block design  (RCB) (Table 1).

 

Table 2 : 8 types of soil
Types of soil	Detail
Sand (Nc)	Used as a negative control
Clay soil (Cl)	Took from behind animal experiment unit place, 0-20 cm. depth.
Loam with compost (Lo)	Loam took from the rear of animal experiment unit place, 0-20 cm. depth and mixed with compost 1:1
Sub soil loam (Sm)	Sub soil under loam, more than 20 cm. depth
Loam with leaf (Ll)	Loam with leaf compost Took from shade area under trees, 0-20 cm. depth.
Sandy loam (Sl)	Took from the rear of guest house, 0-20 cm. depth.
Sub soil sandy (Ss)	Sub soil under sandy loam, more than 20 cm. depth
Compost (Pc)	Used as a positive control

The  two indicator plants were:

• M = Maize
• R = Rice

Procedure

The 8 types of soil (Table 2) were taken from different places around  An Giang University and put into plastic bags (2 liters capacity). 3 seeds of maize or rice were planted in each bag according to the experimental layout in Table 1. A hole was put in the bottom of each bag so the excess water could drain away. Water was applied uniformly to all bags every morning and evening and observations made of germination and growth of the plants. When the seeds had germinated 1 or 2 plants were removed to leave only one seedling in each bag (Photo 1).

Photo 1: The maize and the rice plants growing in the different soils

Measurements

The dry matter (DM),  organic matter, N and pH of soils were measured at the beginning. The height of the plants were measured every 5 days over a total period of 28 days. After 28 days, the plants and roots were removed from the bags, washed free of soil, and weighed 30 minutes later, the green parts (leaves and stems) and the roots separately. 

Laboratory analyses

The chemical analyses were done following standard procedures according to the Association of Official Analytical Chemists procedures (AOAC 1988), except for DM which was determined by micro-wave radiation (Undersander et al 1993).

Statistical analyzes

The linear regression of height on days was calculated to determine growth rate in height. The ANOVA GLM option of the Minitab software was used to analyze the data. The sources of variables in the model were: soils, blocks and error. The Tukey test in the Minitab software was used to separate mean values that differed when the F-test was significant at P<0.05.
 

Results and discussion

Chemical composition of soils

The DM content was highest in the negative control of sand (Nc) and lowest in the positive control of compost Pc (Table 3). The soils with high organic matter content were also high in nitrogen. Organic matter was highest in the positive control of compost (Pc) and lowest in Nc. Most of the soils were alkaline (pH >7) except Ll that had a pH of 5.8. Nitrogen content was highest in Pc (1.82 %) and lowest in Nc (0.05 %).

 Germination

Maize germinated faster than rice (P<0.001) but there were no differences due to type of soil (P = 0.21) (Table 4).  

 

Biomass production

There were different in the responses of the two indicator plants (Table 4; Figures 1 and 2; Photo 2).

Highest biomass yield with maize was in the positive control of compost. In contrast, highest yield of rice was in the loam with leaf compost taken from under the trees (Ll). The lowest yield of maize was in the sub-soil taken from under the sandy loam (Ss); while the lowest yield of rice was in the negative control (Nc). (Table 5.)

 

 

The soil samples which had a high organic matter content (compost, loam mixed with compost and loam with leaf compost from under the trees) supported high biomass production, which was to be expected as organic matter helps the soil hold water and supplies nutrients, which are crucial for crop production (Lickacz and Penny 2001). In the case of maize, biomass production was strongly related to soil organic matter (R² = 0.67) and N (R² = 0 .92) (Figures 3 and 4). Similar relationships for maize were reported by Promkot (2001). There was no relationship between biomass production and soil organic matter, or N, for rice.   

 

 

The proportion of green parts (leaves and stems) of the plants growing in high organic matter soils was higher than that of the roots (Figure 5).

The height and grow rate of plants

The height and grow rate of maize was highest in loam with compost (Lo), while rice highest in loam with leaf (Ll). But the height and grow rate of the both plants lowest in the same soil with negative control (Nc). (Table 6.) 

 

There was a close relationship between plant height and stems and leaves and total biomass (green parts and roots) yield (Figures 6 and 7), indicating that plant height of maize after 25 days growth could be used as the indicator of soil fertility. 

Conclusions

• Maize  was better than rice as an indicator plant to compare the fertility of different soils.

• For maize, growth in height was equally suitable as total biomass weight after 28 days as a means of comparing the different soils.

• Maize growth was closely correlated with organic matter and N content of the soils

Acknowledgements

The mini-project was carried out at An Giang University, Vietnam. I would like to thank the SIDA- SAREC for funding this mini-project - a part of the MSc program course through the regional MEKARN project. I would like to express gratitude to Dr Thomas R Preston, Dr Julio Ly and Dr Do van Xe for patient guidance and encouragement and making it possible for us to complete the mini-project.  I also would like to express my sincere thanks to staff of UTA, Mr. San Thy and Mr. Chhay Ty and An Giang University staff who provided valuable assistance in helping to analyze the data in the laboratory and preparing the materials for conducting the mini-project.

 

References

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

Chamnanwit Promkot 2001 Study of the use of maize and water spinach in a biotest for evaluation of soil fertility. MSc. Course 2001-2003, Sida-SAREC http://www.mekarn.org/MSc 2001-03/minipro/cham.htm

Christy S 2001 About soil pH. ltpwww.gsfc.nasa.gov/globe/soil_pH/plant_pH.htm

Food and Agricultural Organization. Zea mays. www.fao.org/ag/aga/agai/far/afris/data

Lickacz J and Penny D 2001 Soil organic matter, Plant Industry Division, Alberta. http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex890?opendocument

Minitab 1993 statistical software Version 13.

Nguyen Phuc Tien, Ngo Tien Dung, Nguyen Thi Mui,  Dinh Van Binh and Preston T R  2003: Improving biomass yield and soil fertility by associations of Flemingia (Flemingia  macrophylla) with Mulberry (Morus alba) and cassava (Manihot esculenta) on sloping land in Bavi area.  In: Proceedings of Final National Seminar-Workshop on Sustainable Livestock Production on Local Feed Resources (Editors: Reg Preston and Brian Ogle). HUAF-SAREC, Hue City, 25 – 28 March, 2003. Retrieved September 23, 2003, from http://www.mekarn.org/sarec03/tienbavi.htm

Rice web History and general information www.riceweb.com

Soil organic matter 2002 Soil organic mater. www.heinzctr.org/ecosystems/farm/soil_slnt.shtml

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