STPM Chemistry Coursework/Project PBS Sample (2016)

TITLE : THE STUDY OF SOIL IN AGRICULTURE USE

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ABSTRACT

This experiment was conducted to determine soil moisture, soil organic matter(SOM),water

retention of four different soil sample. Loss on Ignition (LOI) analysis is used to identify the

percentage of organic matter and soil moisture. Universal indicator is used to determine soil pH.

Filtration is used to determine the water retention of different soil sample. The results show that

clay which is neutral has the highest soil moisture, water retention and soil organic matter

among four soil sample. Clay soil is most suitable for agriculture uses among four soil sample.

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CONTENT PAGE

TITLE 1

ABSTRACT 2

CONTENT 3

CHAPTER

1.0 INTRODUCTION

1.1 Literature Review 4

1.2 Problem Statement 6

1.3 Objective 6

2.0 METHODOLOGY

2.1 Theory 7

2.2 Procedure 7

2.3 Formula 9

3.0 OBSERVATION , RESULT AND DISCUSSION

3.1 Result 10

3.2 Discussion 13

4.0 CONCLUSION 16

REFERENCES 17

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1.0 INTRODUCTION

1.1 Literature Review

Soil is a mixture of minerals ,organic matter , liquid and organisms which is medium for plant growth

and water storage. Soil acts as a recycling system for nutrients and organic wastes contain mixture of

inorganic and organic particles.

Soil moisture is one of the few directly observable hydrological variables that plays an important

part in the water and energy budgets necessary for climate studies.[1] In advanced agriculture, many

instruments and methods have been used to monitor and measure soil moisture. Tensiometers,

resistance blocks, gravimetric methods, and granular matrix sensors have been commonly used for

many decades and will continue to be widely applied in irrigation scheduling.[2] Monitoring of soil

moisture is important because it have numerous benefits in the fields of meteorology, hydrology,

agriculture, and the monitoring of global climate change. For example, various research had improved

weather predictions through improved modeling of the interaction of land surface processes,[3]

improve flood forecasting through the influence on partitioning of precipitation between runoff and

infiltration[4] and increase crop yield through optimal soil moisture conditions at pre-planting and

during the growing season.[5]

Soil organic matter (SOM) plays a major role in the productivity of soils and is particularly

important in terms of soil fertility and the water holding capacity of strongly weathered soils of the

tropic. [6] SOM increases soil fertility by providing cation exchange sites and acting as reserve of

plant nutrients, especially nitrogen (N), phosphorus (P), and sulphur (S), along with micronutrients,

which are slowly released upon SOM mineralisation. Globally, soils and surface litter store 2-3 times

the amount of carbon (C) present in atmospheric CO2.[7]Consequently, any change in the size and the

turnover rate of soil C pools may potentially alter the atmospheric CO2 concentration and the global

climate. Soil respiration, which integrates below-ground plant and microbially derived CO2, is one of

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the largest annual transfers in the global C budget. The annual global CO2 flux from soils is estimated

to average (± S.D.) 68± 4 Pg C/ yr.[8] Managing soils to increase their carbon storage capacity has

been proposed as a means to reduce the rise of CO2 concentrations in the atmosphere. Increasing soil

C storages also improves soil fertility and productivity, and thus provides a clear win-win situation.

Appropriate action, however, requires an understanding of mechanisms governing the long-term

residence time of organic matter (OM) in soils. The mechanisms for C stabilization in soils are still

not well understood and the ultimate potential for C stabilization in soils is unknown.

Soil pH can affect plant growth directly and indirectly by affecting the plant availability of

nutrients, levels of phytotoxic elements, and microbial activity. Low pH can inhibit the activities of

soil micro-organisms that decompose SOM and so can lead to the preservation of SOM inputs into

the soil .[9] However, other research found the opposite trend with an increasing SOC accumulation

following afforestation with increasing pH (7 pH = 22%). [10]Their studies also found that the soil

pH had no significant effect on soil C stock changes.Some studies suggests that the SOC increase

with pH may be due to low pH soils retarding tree growth due to nutrient deficiencies, leading to a

decline in the inputs of SOM into the soil from trees compared to soils with a higher pH. [11] This

highlights the need for more research to fully distinguish the effect pH on soil C stocks following

afforestation.

Study of soil and its water holding capacity is essential for the efficient utilization of irrigation

water. Hence identification of geotechnical parameters which influence the water retention capacity

and the method of adding admixtures to improve the retention capacity of soil, play an important role

in irrigation engineering. Coir pith, Coir Pith Compost and Vermi Compost are good admixtures for

improving the water retention capacity as well as nutrients of the soil. India is one of the leading

countries of the world in area and production of coconuts. The coconut husk finds numerous

applications due to its fibrous structure and resilience. Coir pith is a waste product produced during

the process of extraction of fibre from coconut husk which contains one third of fibre and two third of

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pith. Thus for every tonne of fibre about 2 tonnes of coir pith waste is generated. This is mostly

unutilized at present and poses a great problem to the fibre manufacturing units as it occupies large

area due to its fluffy nature ( dry density = 0.2gm/cc). Apart from space problem it also poses

environmental problems due to fire hazards and pollution. The adverse effects of acidic nature can be

mitigated by rinsing it with water three to four times.

1.2 Problem Statement

How soil organic matter, soil moisture, pH value, water retention in different type of soil

influence in the field of agriculture?

1.3 Objectives

The objectives for this experiment are :

i. To determine the percentage of organic matter, soil moisture and water retention in different

type of soil for the benefit in agriculture.

ii. To determine the pH in different type of soil for benefit in agriculture.

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2.0 METHODOLOGY

2.1Theory

Loss on Ignition (LOI) analysis is the difference in weight before and

after ignition of the soil sample. Soil organic matter is estimated from LOI

using regression analysis. This method is used to determine the percentage of

organic matter (% SOM) of a soil sample. The procedure involved is relatively

simple compared to others used to determine (% SOM).

LOI calculates (% SOM) by comparing the weight of a sample before and

after the soil has been ignited. Before weighing the ignition weight of the soil

sample, weight of soil before and after heating by Bunsen burner is recorded

to calculate the percentage of soil moisture. Before ignition the sample

contains organic matter, but after ignition all that remains is the mineral

portion of the soil. The difference in weight before and after ignition

represents the amount of the organic matter that was present in the sample.

2.2 Procedure

For soil moisture and soil organic matter (SOM) , a fresh sample of soil is weighed between

10-15 grams and recorded. The soil sample is dried at 130° C in drying oven for overnight to

remove moisture. Tongs are used to take the sample from the oven after oven-drying. Oven-

dried sample is reweighed to get the pre-ignition weight and calculate the percentage of soil

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moisture. Further heating of the sample will undergo by using Bunsen burner for 45 minutes.

Post-ignition weight is achieved when the sample is reweighed after further heating.

Subtraction is required for the weight of empty porcelain crucible from the post-ignition

weight to calculate the percentage of soil organic matter. The experiment is repeated

similarly by using the different soil samples.

For pH value of soil, one full spatula of barium sulphate is put into dry test tube.Barium

sulphate is used to precipate the soil particle so the pH test could be conducted. One full

spatula of soil is put into the test tube. Fill the test tube with distilled water until three over

four full. 5 to 6 drops of universal indicator is put into the solution drop by drop. A stopper is

placed and shake the tube well and allow the tube stand for short while until a clear coloured

liquid formed at top. The colour of the liquid is compared with the pH chart and record the

pH. The experiment is repeated with different soil sample.

For water rentention in soil, 4 types of fresh soil is prepared which is silt , sand ,clay and

chalky soil. 45 g of soil is weighted by using electronic balance.The filter paper is put into

filter funnel . The soil is put into filter funnel and put it on top of the conical flask. 40 cm 3 of

water is prepared in each of the 4 beaker. The water is poured into the filter funnel which

contained soil and start the stopwatch immediately. The amount of water leaked is recorded

into the beaker every 5 minutes. The experiment is conducted for 30 minutes.

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2.3 Formula

i . Weight of soil :

ii. Percentage of soil moisture :

To get the percentage of soil moisture, calculate the difference of the weight of sample before and after drying, divided by the initial weight and multiply

with hundred percent.

iii. Percentage of soil organic matter :

To get the percentage of soil organic matter, calculate the difference of the weight of sample before and after heating, divided by the initial weight and

multiply with hundred percent.

3.0 OBSERVATION, RESULTS AND DISUSSION

3.1 Result

Soil mositure and Soil organic matter (SOM)

Sandy soil

Weight of porcelain crucible with soil sample ̶ Weight of empty porcelain crucible

(Weight of sample beforedrying (̶ Weight of sampleafter drying)Weight of samplebefore drying

×100 %

(Weight of sample beforeheating (̶ Weight of sampleafter heating)Weight of samplebefore heating

× 100 %

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Weight(grams)

After heat in oven for overnight

After burn by Bunsen burner for 45 minutes

Empty porcelain crucible 48.40 31.62Porcelain crucible with

soil sample 59.28 42.70

Soil sample 59.28 - 48.40= 11.18

42.70 – 31.62= 11.08

Porcelain crucible with soil sample

(after experiment)59.50 42.63

Soil sample(after experiment)

59.50-48.40= 11.10

42.63 ̶ 31.62= 11.01

Result

% of Soil Moisture :11.18−11.10

11.18× 100 %

= 0.72%

% of Soil Organic Matter :11.08−11.01

11.08×100 %

= 0.63 %

Clay

Weight(grams)





Soil sample 58.37 ̶ 47.54= 10.83

46.33 ̶ 41.59= 4.74




52.28 ̶ 47.54= 4.74

45.14 ̶ 41.59= 3.55

Result% of Soil Moisture :10.83−4.74

10.83× 100 %

= 56.23 %

% of Soil Organic Matter :4.74−3.55

3.55× 100 %

= 25.11 %

Silt soil

Weight(grams)



Empty porcelain crucible 41.25 45.39

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Porcelain crucible with soil sample 51.87 54.19

Soil sample 51.87 ̶ 41.25= 10.62

54.19 ̶ 45.39= 8.80




50.01 ̶ 41.25= 8.76

54.01 ̶ 45.39= 8.62

Result

% of Soil Moisture :

10.62−8.7610.62

×100 %

= 17.51 %

% of Soil Organic Matter :

8.80−8.628.80

×100 %

= 2.05 %

Chalky soil

Weight (grams)





Soil sample 51.20 ̶ 41.11= 10.09

50.32 ̶ 41.23= 9.09




50.23 ̶ 41.11= 9.12

50.30 ̶ 41.23= 9.07

Result

% of Soil Moisture :

10.09−9.1210.09

× 100 %

= 9.61 %

% of Soil Organic Matter :

9.09−9.079.09

×100%

= 0.22 %

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Sandy soil Clay Silt soil Chalky soil0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

0.72%

56.23%

17.51%

9.61%

0.63%

25.11%

2.05% 0.22%

Soil Organic Matter & Soil Moisture

Soil MoistureSoil Organic Matter

Percentage

pH value of soil

Soil sample Colour pH value DenominationSandy soil Greenish-blue 8.0 Moderately alkaline

Clay Pale-green 7.0 NeutralSilt soil Pale yellow 6.5 Slightly acidic

Chalky soil Pale blue 9.0 Strongly alkaline

Water rentention in soil

Types of soilTime(s)

Sandysoil

Clay Siltsoil

Chalkysoil

5 23 8 25 3010 25 9 28 3415 26 9 30 3520 26 9 30 3625 26 9 30 3630 26 10 30 37

Volume of water absorbed(cm3)

14 30 10 3

Percentage of water absorbed (%)

35% 75% 25% 7.5%

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3.2 Discussion

Four experiment have been done to test the 4 types of soil on its soil organic matter , soil

moisture ,water retention and its pH in order to relate to its agriculture use.

Soil are generally made up of varying mixtures of different size of soil particles.

From the experiments , clay soil has highest water retention because it absorb most amount of

water due to its highest water holding capacity . Thus , it has highest soil moisture among four

soil sample . Clay soil has the smallest soil particles and have many small pore spaces that

make water move slower when passing though it. Their smallest soil particle cause them have

good soil organic matter storage qualities due to the tiny size of its particles and its tendency to

settle together, little air passes through its spaces. It also slower to drain, it has a tighter hold on

plant nutrients. Thus , clay has the highest organic matter among four soil sample. Clay soil is

neutral and showed 7.0 . It is suitable for plants grow well from pH 6.0-7.0 such as

beans ,broccoli , pumpkins ,raspberry and others. Lettuce, chard, snap beans and other crops with

shallow roots prefer to grow in clay soil which has greater water holding capacity to retain its

moisture. Broccoli, brussels sprouts and cabbage often grow better in clay soil than looser loams.

Silt soil absorbed less water than clay soil but more water than sandy soil which was 14

cm3. Silt soil has weaker water holding capacity than clay because it has much smaller particles

than sandy soil but larger soil particles than clay soil . It has higher soil moisture that silt soil has

much smaller particles than sandy soil so it is smooth to the touch and soapy slick when

moistened. Silt soil retains water longer than sandy soil, but it cannot hold on to as much

nutrients as clay soil and it drains poorly . Hence ,silt soil contains poorer soil organic matter

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than clay soil. This is because they are made up of fine particles that can be easily compacted by

treading and use of garden machinery but they contain more nutrients than sandy soils and hold

more water and tend to be quite fertile for certain plants. Silt soil are slightly acidic and showed

pH 6.5 . It is suitable for plants such as carrots, potatoes , tobacco , tomatoes because most plant

prefer slightly acidic soil pH of 6.5 -7 the point where nutrients are most easily available .

Sandy soil has lower water retention than silt and clay due to its larger soil particles than

silt and clay soil and it have poor water holding capacity because there is huge space between

soil particles. it cannot hold on to water. Water drains rapidly, straight through to places where

the roots, particularly those of seedlings, cannot reach. Thus , Sandy soil has lower soil moisture

than silt and clay. Plants do not have a chance of using the nutrients in sandy soil more

efficiently as they are swiftly carried away by the runoff. Therefore, sandy soils are ideal for

crops such as watermelons, peaches and peanuts, and their excellent drainage characteristics but

low water and nutrient holding capacity make them suitable for intensive dairy farming. It cannot

hold on to water. But it made out of large particle which can hold more soil organic matter than

chalky soil which mostly consist of stones it had higher soil organic matter than chalky soil.

Sandy soils are generally more acid than clay soils and it showed pH 5.5 when test with universal

indicator and it is moderately acid and suitable for plants such as potatoes ,tomato and tobacco.

Chalky soil has largest soil particles among the soils and poorest water retention ability

among the soils . It consists of a large number of stones and they are prone to dryness and it is a

poor choice for plantation as the plants would need much more watering and fertilizing than on

any other type of soil. Chalky soil has lowest water moisture among the soils as it tends to drains

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really fast which is not ideal for moisture loving plants like runner beans, broad beans.

Moreover , it has lowest soil organic matter among four soil sample because it mostly consist of

stones and it tends to drains really fast which cause soil organic matter being washed away. Very

chalky soils may contain lumps of visible chalky white stone and make it harder to store soil

organic matter. Chalky or lime-rich soils may be light or heavy but are largely made up of

calcium carbonate and are very alkaline and they have a pH of 9.0 . Plant such as

conifers ,shrubs , herbaceous perennials ,ornamental grasses prefer to grow in free draining and

low in fertility soil which is chalky soil. Vegetables such as mushroom , yam , okra prefer grow

in highly alkaline soil which is chalky soil.

Some challenges were attained during this experiment. After a rainy day, soil moisture in

soil may vary in different area . Therefore, soil sample would not be collected after a rainy day.

Although lack of sophisticated equipment such as soil moisture sensor, soil moisture values

measured by manual drying method are generally considered as the most accurate and reliable

data. The absence of apparatus muffle furnace had lead to the alternative use of Bunsen burner to

heat the oven-dried soil sample. 45 minutes was the most suitable duration to decompose the

organic content in the soil sample. Some precautions were taken to get an accurate and consistent

result. To maintain the freshness of soil samples, they were kept in refrigerator minimum at 4°C

but not more than 14 days. A dry and clean porcelain crucible was ready for each soil sample,

record each of the crucible corresponding to each sample to avoid inaccurate data.

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4.0 CONCLUSION

From the experiment, clay has the highest soil moisture, water retention and soil organic

matter (SOM) among four soil sample. Hence, clay soil is most suitable for agriculture uses

because it has highest water holding capacity and tighter hold on plant nutrients and contain

richest soil organic matter that required by plant growth.

For soil pH , the pH in increasing order as follows, sandy (5.5)<silt (6.5)<clay (7)<chalky

(9.0). Silt soil and clay soil made the ideal condition for plant growth because most plant prefer

slightly acidic soil pH of 6.5 -7 where nutrients are most easily available.

In general, the future developments in soil science research must be directed to a better

understanding of the processes and reactions in soils related with crop production, chemical

recycling and water balance, over a range of spatial and temporal scales. This has to be followed

by the development of simplified simulation models to find the best combination of management

practices, integrating selected critical parameters of soils, crops and climate.

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REFERENCE

1. Jackson, T. J., 1993. III Measuring Surface Soil Moisture Using Passive Microwave

Remote Sensing. Hydrol. Processes, 7: 139-152.

2. Seyfried M.S. and Murdock, M.D. (2001). Response of a new soil water sensor to

variable soil, water content and temperature. Soil Sci. Soc. Am. J. 65:28-34

3. Fast, J. D., and McCorcle, M. D., 1991. The Effect of Heterogenous Soil Moisture on a

Summer Baroclinic Circulation in the Central United States. Mon. Wea. Rev., 119: 2140-

2167.

4. Entekhabi, D., Nakamura, H., and Njoku, E. G., 1993. Retrieval of Soil Moisture by

Combined Remote Sensing and Modeling. In: Choudhury, B. J., Kerr, Y. H., Njoku, E.

G., and Pampaloni, P. (Eds.), ESA/NASA International Workshop on Passive Microwave

Remote Sensing Research Related to Land-Atmosphere Interactions, St. Lary, France,

485-498.

5. Topp, G. C., Davis, J. L., and Annan, A. P., 1980. Electromagnetic Determination of Soil

Water Content: Measurements in Coaxial Transmission Lines. Water Resour. Res., 16(3):

574-582.

6. Coleman D.C., Oades J. M., Uehara G., 1989. Dynamics of Soil Organic Matter in

Tropical Ecosystems. Published by NifTAL Project. 249 pp

7. Houghton, R.A., The comtemporary carbon cycle. In: Schlesinger, W.H.

(Ed.).Biogeochemistry, Elsevier-Pergammon, Oxford, 2005, 473-513.

8. Raich, J. W.; Schlesinger, W. H., The global carbon dioxide flux in soil respiration and

its relationship to vegetation and climate. Tellus B 1992, 44, 81-99.

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9. Aciego Pietri, J.C., Brookes, P.C., 2008. Relationships between soil pH and microbial

properties in a UK arable soil. Soil Biology and Biochemistry. 40, 1856–1861.

10. Laganière, J., Angers, D.A., Parè, D., 2010. Carbon accumulation in agricultural soils

after afforestation: a meta-analysis. Global Change Biology. 16, 439-453.

11. Augusto, L., Ranger, J., Binkley, D., Rothe, A., 2002. Impact of several common tree

species of European temperate forests on soil fertility. Annals of Forest Science. 59, 233–

253.

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Education

STPM Chemistry Coursework/Project PBS Sample (2016)