Determining the relative fertility of soil using the biotest method with maize as indicator plant

Lotchana Tayxayngavong

Champasack University

Champasack province, Lao PDR

lotchanasouks@yahoo.com

^*Finca Ecológica, TOSOLY, UTA (Colombia)
AA #48, Socorro, Santander, Colombia
trpreston@mekarn.org

Abstract

The experiment was conducted at Kampong Cham National School of Agriculture, Cambodia. Five types of soil were taken from different places around Kampong Cham district to measure fertility of soils by using the bio-test with maize (Zea mays) as the indicators, according to a 5*2 factorial arrangement with four replications, the factors were: soil, with or without biochar. The soils were peaty soil, chalky soil, clay soil, Silty soil, and loam with compost, (All of soils took around 0-20 cm. depth).  The soil samples were put into 1.5 liters capacity plastic bags and 3 seeds of either maize were planted in each bag (4 bags per soil). Date to germination, plant height at every 3 days intervals and final weight of biomass after 26 days were measured.

There were significant differences between soils in the growth in height but no effect in the soil that mixing biochar and interaction for soil * Biochar for height measurements of maize. However, soil with mixing biochar; it was increase acid soil to tend to more alkaline, it was suitable for growing maize. Besides that, it was supported the germination of maize was very fast and increased biomass production of maize. In addition, physical composition of soil was positively correlated to plant growth particularly in maize. For maize, There was a close relationship between pH of soil and increase due to biochar (R² = 0.75).

It is suggested that the biochar increased soils pH, germination and amount of biomass of the maize and field research for a better understanding of biochar material and its ability to maintain soil quality.

Key words: Biochar, organic matter, pH, soil fertility, Peaty soil, chalky soil, clay soil, Silty soil, Loam with compost.

Introduction

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 (Chamnanwit Promkot 2001 and Nguyen Phuc Tien 2003). . According to Boonchan Chantaprasarn (2003), maize is a better indicator plant than rice.

Soil organic matter is partially decayed plant and animal matter. 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.

pH is a measurement 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 alkaline soil has a pH of around 8.5 whilst the pH of neutral soil is 7. Most plants grow best in soil with a pH of between 6.5 and 6.8.In addition for maize pH 6.5 sufficient and pH 6.0 sufficient for high pH subsoil (John 2003) 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.

Biochar is biomass (wood plants, plant waste) that has been converted to charcoal and it produced by pyrolysis: heating in the absence of oxygen, which prevent burning of the biomass (which happen in open fires). In addition, Biochar and its byproduct has multiple uses, when added to the soil it can significantly improve soil fertility. Especially if some volatile are left or recycle back in, the volatile fluids and gasses produce usable bio-fuels, that can be produce on the sustainable basic and then the carbon, when recycle into the soil, provides a stable long term removal of carbon (dioxide) from the atmosphere. Removing carbon from the atmosphere is called sequestration (Lukas Van Zwieten 2006 and Rick Davies 2007). Besides that, Biochar 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.2003a; Lehmann and Rondon 2005).

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 with stand frost. There are many types of maize and the grain may be yellow, white or red. The maize bio-test is suitable for evaluation of soil fertility (Promkot 2001).

In this experiment, maize was chosen as bio-test indicator plant for measuring fertility of soils.

Hypothesis

Mixing of biochar with 5 types of soil sample will increase the growth of maize but the increase will depend on the basic fertility of the soils that are chosen.

Objectives

Compare between 5 types of soil with mixing biochar in each soil by using maize (Zea mays) as biotest indicator plant.

Materials and methods

Location

The experiment was conducted in the experimental area of Kampong Cham National School of Agriculture, Cambodia from 7 August to 5 September, 2008. and the soil was collected from 5 different origins. Located around Kampong Cham district

Experimental design

The treatments were source of soils and levels of biochar arranged as a 5*2 factorial in a Completely Randomized Design (CRD) (see Table 1) with 10 treatments and 4 replications. The factors were:

-         Soils

-         With or without biochar

• Five types of soil were compared as show bellow:

• PS =                Peaty soil

·    CK=                Chalky soil

• CS =                Clay soil

• SS =                Silty soil

• LC =                Loam with compost

• PSB =              Peaty soil, 5% Biochar

• CKB =            Chalky soil, 5% Biochar

• CSB =             Clay soil, 5% Biochar

• SSB =              Silty soil, 5% Biochar

• LCB =             Loam with compost, 5% Biochar

The one indicator plant was:

• M = Maize

Procedure

Five types of soil (see Table 2) were taken from different places around Kampong Cham province and put into plastic bags (1.5 litters). Three seeds of maize 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. In addition the Color of plant, germination and growth of plants were observed every day. After germination the height of the plants were measured every 3 days over a total period of 30 days.After 30 days, the plants and roots were removed from the bags, were washed free of soil, and weighed 30 minutes later, the green parts (leaves and stems) and the roots separately.  

Measurements

Soil simples were analyzed for dry matter (DM), nitrogen (N), Ash, organic matter (OM), and pH at the beginning. The heights of the plants were measured every 3 days over a total period of 26 days. After 26 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 DM contents were determined using the micro-wave relation method of undersander et al (1993). N, OM and Ash were determined following by AOAC (1990) procedures. Except for pH of soil samples were determined by using Soil pH Test Kit (compare with examine color in natural light not fluorescent).

Statistical analysis

The linear regression of height on days was calculated to determine growth rate in height. The ANOVA GLM option of the Minitab software (version 13.1) was used to analyze the data. The sources of variation in the model were: soils, biochar, and interaction soil*biochar 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 soil

The DM content was highest in the peaty soil and lowest in the clay soil. The soils with high organic matter content were also high in nitrogen (Figure 1). Organic matter was highest in the Loam with compost (LC) and lowest in Silty soil (SS). Most of the soils were acidic (pH <7). Also Nitrogen content was highest in Loam with compost (0.261 %) and lowest in Silty soil (0.012 %). For biochar there was no nitrogen and it was  slightly alkaline (pH 9.5), that why when mixture with biochar into soils, it was increase the pH of soil (Table 3).

Germinations

Germination of maize after 4, 5 and 6 days, maize germinated faster in the soil with mixing biochar than the soil without biochar. Especially, on day 6 the percentages of maize germinated were higher than the soil without biochar (Table 4).

Growth in height of the maize

There were significant differences in maize height between soils. However, there were no effect on soil with mixing biochar and interaction between soil and biochar(Table 5).

Height of the maize

The highest was in the peaty soil with mixing biochar and the lowest was in the chalky soil with mixing biochar. Besides, loam with compost that mixing with or without biochar were quite equally because both of these soils were higher pH more than another soils, so when adding biochar into soils it was high alkaline (7.5) that why it was not suit table for maize. For adding biochar was increased slightly from CKB to CSB (figure 2 and 3).

Biomass production

There were different in the responses of maize as the indicator plants (Photo 7 and 8; Figures 4).

The highest biomass yield with maize was in the soil with mixing biochar. In addition, highest yield of maize was in the peaty soil with mixing 5% biochar (PSB). (figure 4). However, for loam with compost without biochar also higher than Loam with biochar. On the other hand, the lowest yield of maize was in chalky soil with or without biochar (CK and CKB). Besides, there were a lot of amount of root of the maize on soil with mixing biochar (More amount of root was easy to take off nutrient from the soil) (Table 6 and figure 5). Therefore we could say adding biochar to soil would not only dramatically improve soil and increase crop production. But it was in crease biomass of maize.

For low soil pH not only stunts maize growth and development, but can actually kill maize plants in extreme situations. Besides stunted plants, symptoms of low soil pH commonly include a beaded reddish or necrotic striping of the lowermost leaves (sometimes also associated with magnesium deficiency) and brown stubby (thickened) roots (Bob Nielsen 2005). Low pH levels affect nutrients by converting them into forms that are not readily available to the crop. In addition, low pH levels can increase the solubility of plant toxic metals such as aluminum resulting in stunted growth and a general lack of plant Therefore, to obtain optimum plant growth it is critical that soils be limed to increase pH levels. However, when mixing with biochar into Peaty soil which had a low pH content in a neutral material to acidic soil will tend to make it more alkaline, since the total volume of soil has been increased with no increase of acidic chemicals, biochar were neutral, or slightly alkaline, it would decrease the alkalinity of soil that was highly alkaline to begin with by diluting that alkalinity. The same biochar added to highly acidic soil would indeed, make it more alkaline. Both those scenarios assuming biochar that is neutral or slightly alkaline (Andrew J ajmorris 2008). In addition, which was to be expected as improves soil structure and water retention, enhances nutrient availability, and lowers acidity (Winsley Peter 2008). Similar relationships for increases in pH particularly interesting are the improvements in soil physical properties were reported by Tom Miles (2008). And Scientists researching these soils now recognize that biochar makes soil higher in nutrients, better at holding moisture, and lower in pH, or soil acidity (Robert 2008). So, we could say the biochar increased soil pH, water holding capacity, potassium availability, moisture retention and increase soil health.

There was a close relationship between pH of soil and increase due to biochar (R² = 0.75), soil which had a lowest pH was highest because of adding biochar into soils was increases the pH of soil in order to suitable for growing maize.

The proportion of green parts (leaves and stems) of the maize growing in low pH of the soil was higher than that of the roots (Figure 10). However, there were a lot of amount of root more than the soil without biochar.  

The amount of biomass of maize was higher in soil with mixing biochar, similar with B.Liang and J. Lehmann 2006 reported Biochar may significantly affect nutrient retention and play a key role in a wide range of biogeochemical processes in soils, especially for nutrient cycling. With high contents of biomass .

The height and grow rate of maize

The height and grow rate of maize was highest in peaty soil with mixing  5% biochar (PSB). However, the height and grow rate of maize lowest in the same soil with or without biochar (Chalky soil and Chalky soil with 5% biochar) (Table 7). 

There was a close relationship between maize height, and stems, leaves and total biomass (green parts and roots) yield (Figures 11 and 12).

Conclusions

·        Biochar was increase acid soil to tend to make it more alkaline. Besides that, it was facility for maize germinations faster. And also when added biochar into the soil there were a lot of amount of root (More root could take off nutrient easily from soil and transfer to another part of its plant).

·        There were no differences among the soils in maize height when 5% biochar was added to the soils. However, the soil that mixing with 5% biochar, it was higher biomass than soil without biochar.

Acknowledgements

The mini-project was carried out at Kampong Cham National School of Agriculture Cambodia. 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 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 CelAgrid, Mr. Chhay Ty and staff of NAFRI, Ms Latsamy and Kampong Cham National School of Agriculture staff who provided valuable assistance in helping to analyze the data in the laboratory and preparing the materials for conducting the mini-project. Many thanks to my classmates in the MSc course for their contributions, suggestions and friendships.

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