Hello, my name is Chloe, and I'm a geography field studies tutor.

This lesson is called Field Work: Planning a Soil Inquiry and Collecting Data.

It forms part of a unit of work called Rocks, Weathering, and Soil: Why is Geology Important? In this lesson, we're going to be looking at the kind of field work you can do when you're investigating soils in more detail.

We're going to be planning a piece of field work, and then, by the end of the session, we're actually going to go out and collect some data.

Let's get started.

By the end of this lesson, you will be able to collect soil texture data on your own school site.

Before we get started, let's review some of the key words we're going to be using in this lesson, first of all, soil texture.

This refers to the characteristics of soil, such as how large the soil particles are, or how large the pores or the spaces between those particles are.

Then there's porosity.

This is how porous soil structure is, i.

e.

the size and the quantity of spaces between different soil particles.

And then of course, infiltration.

This is the movement of water from the surface to the lower soil layers.

The lesson is divided into two parts.

We're first of all going to be looking at how we might plan a soil inquiry, and then it's all about how we might collect the data associated with that inquiry.

So let's start with the planning stage.

Geographers often use inquiries when they carry out field work, so there's lots of elements that we need to be thinking about as we get into our planning stage.

We need to think about what needs to be investigated.

We need to formulate an inquiry question.

Then we need to follow a set inquiry structure.

And we need to make predictions about the outcome of the inquiry.

A geographical fieldwork inquiry follows a set structure.

We're gonna go through that now.

First of all, there's the inquiry question, a question about the place you are interested in.

Then there's the data collection stage.

This is about measuring and recording data, and that will help you answer your inquiry question.

What follows that is data presentation, presenting your data using maps and graphs, for example.

And once you've presented the data, you then want to analyse it.

You're going to be looking for patterns in your data and thinking about what that data tells you.

Following that is the conclusion.

Here, you answer your inquiry question based on the data that you have collected.

And then finally, completing our inquiry cycle, is our evaluation.

This is where we think about how we carried out our inquiry, and what we would change to improve the accuracy of our conclusions were we to do it again.

So let's check our understanding of those points so far.

In what stage of a geographical field work inquiry would a geographer reflect on the strengths and weaknesses of their investigation? Is it A, in the data presentation, B, in the data analysis, C, in the conclusion, or D, in the evaluation? Pause the video here and have a think about what you've just learned about in the inquiry cycle, and then come back to me with the right answer.

Okay, hopefully you remembered that it's D, the evaluation.

Hope you got that right.

So we're gonna be looking at this first stage of our cycle, and that is the inquiry question.

In this fieldwork inquiry, the title question is, how does soil texture affect infiltration around our school site? The data required to answer this question is infiltration rate, how fast the water moves through the soil, the soil type, how it's made, what the different particles are that make up our soils, and soil compaction, so how compact the soil is, how small those pores or air spaces are between the different types of soil.

Soil type is likely to have a strong influence on the speed at which water moves through it.

A soil made up of large particles, such as a sandy soil, will have high porosity.

In other words, it will have large pores between the particles.

This means that water can infiltrate more easily and quickly through the soil.

A soil made up of small particles, such as a clayey soil, will have a low porosity, so there'll be very small pores in between the particles.

This means that water takes a lot longer to infiltrate through the soil.

It will start off on the surface and very slowly move through.

Compaction of the soil, such as by humans continually walking on it, can reduce the pore size even more.

A hypothesis is a statement that can be tested.

Geographers use hypotheses to help them answer their inquiry question and focus their ideas.

Aisha and Jacob have made some hypotheses.

Aisha says, "I hypothesise that the soil samples with the highest percentage of sand will have the fastest infiltration rates." Jacob says, "I hypothesise that the areas with the greatest soil compaction will have the slowest infiltration rates.

These soils will have lower porosity as a result of the compaction." Let's check our understanding based upon Aisha's hypothesis there.

How might we explain her hypothesis further? Remember, she says, "I hypothesise that the soil samples with the highest percentage of sand will have the fastest infiltration rates." Is the explanation for that that the large sand particles in soil create larger pores? Is it that small sand particles in soil create larger pores? Or is it that small sand particles in soil create smaller pores? Think back to those diagrams we saw a moment ago, and then pause the video and have a think and come back to me.

Well done if you remembered that sand is one of our largest soil particles that we can have.

This means that it creates large pores in between the particles, and yes, that means that it's likely that infiltration will happen at a faster rate.

Let's move on to our first practise task now.

Examine a plan of your school site.

Choose an area where you hypothesise that the soil compaction will be the highest.

Then hypothesise where you think soil compaction will be the lowest.

Then I'd like to justify your hypotheses.

Say why you think the soil compaction will be highest and lowest in those places.

This might be something you would want to discuss with somebody nearby to see what their thoughts are.

So do pause the video and then come back to me with your ideas.

Right, let's look at some examples of the kind of thing you could have said.

First of all, we're thinking about where you could find a soil that has a high amount of compaction.

Andeep here is talking about this particular part of his school site.

He says, "I think this area will have the highest soil compaction because it is the only route from the changing rooms to the football pitch, so everyone uses it." Yes, you could imagine that that part of the soil, that part of the school grounds is gonna get a lot of feet running over it, and therefore the soil's going to be really compact.

So that's a well justified hypothesis that Andeep has made.

Then Andeep had to think about where on his school site soil compaction would be at its lowest, and you can see where he's chosen in the diagram there.

He says, "I think this area will have the lowest soil compaction because it is an area that is out bounds, so nobody goes there to walk over the soil." So Andeep is suggesting that means that the soil won't have as much compaction as other areas because it's just doesn't get the footfall.

Another sensible justification for his hypothesis.

Now we'll move on to the second part of today's lesson, which is all about actually collecting some data to do with soil texture.

So we're moving on to the second stage in our inquiry cycle, data collection.

The soil texture survey has three parts to it.

We're going to be measuring infiltration rates, we're going to be measuring soil compaction, and we'll be measuring the soil type as well.

In order to do this, we're going to be using some specific field work equipment.

We're going to need an infiltrometer.

This is a plastic tube, which sometimes has markings on it to show depth, and this will get slightly hammered into the soil.

We're gonna be hammering it in using a soft rubber mallet.

And they're gonna be using something called a soil augur.

This is like a small drill which you can hammer into the soil, and when you pull it out, you'll get a small plug of soil sample remaining in the barrel of the auger.

And finally, a measuring cylinder.

So this case, it's a glass measuring cylinder of about a hundred millilitres.

To measure infiltration, an infiltrometer is gently hammered into the ground.

Please note here, the person doing the hammering is keeping their hands well away from where the hammering point is.

Then 500 millilitres of water is poured into the tube.

A timer is started as soon as the pour starts.

Once all the water has infiltrated into the soil, the timer is stopped, and it's this amount of time that is recorded.

To measure soil compaction, a soil auger is held on the soil surface.

The auger is struck firmly with a mallet, until it is entered the soil to a depth of 10 centimetres.

Please note again that the person doing the hammering is keeping their fingers well away from where the hammer site is.

The number of strikes it takes to do this is then recorded.

The greater the number of strikes, the more compact the soil is.

It is important that each strike of the mallet is as equal in force as possible.

To measure soil type, the soil auger is hammered 10 centimetres into the ground.

The auger is removed carefully with a slight twisting motion.

A slug of soil will be present in the auger.

You can see it there in the picture.

That slug of soil is transferred into a clear measuring cylinder.

Water is poured into the measuring cylinder until the slug is covered generously.

Covering the open end of the cylinder, the contents are shaken vigorously.

It is left to stand then for 24 hours.

We will start to see some settlement in the cylinder almost straight away.

After 24 hours, three distinct layers should be visible in the measuring cylinder.

You should be able to see sand at the bottom, followed by a layer of silt, and then a layer of clay.

You will have to look quite carefully at your measuring cylinder, and possibly shine a bright light onto it to really see this distinction between the different layers.

The depth of each layer is measured using a ruler, as well as the total height of the soil sample.

You can then calculate the percentage of each type of soil in the sample.

You can see how you would do it using this equation.

The depth of the sand in centimetres divided by the total height of the sample, also in centimetres, times 100.

That will give you your percentage.

Jun is commenting on the data collection method here.

He says, "I'm going to do three infiltration surveys at each site.

That way I may get a more accurate picture of what each area is like." Why might Jun's data collection method actually be a bad idea? Sophia says, "That would mean the second and third surveys at each site would have different starting conditions.

The results would not be accurate." Sophia is right.

Performing the infiltration survey three times means that on the second and third survey, the soil is likely to already be saturated with water.

That means those pores between the particles will already be filled with water, therefore, it's actually gonna slow the infiltration rate down on the second and third attempts.

This would create misleading results.

Let's check our understanding of those points.

What measures should be taken to ensure the infiltration data between the sites is comparable? A, use the same equipment.

B, use the same volume of water.

C, survey the sites at exactly the same time.

D, have the same starting conditions.

E, ensure the data is the same.

And F, ensure the sites have the same soil type.

Read those options again carefully, and maybe have a chat with somebody nearby as well, and then come back to me when you've had the chance to have a think with the right answer.

So it's a little bit tricky this one.

There's obviously more than one right answer.

Well done if you got those three.

Yes, you should be using the same equipment each time.

It ensures there's consistency as you go from one site to another.

And you should also be using the same volume of water.

We suggest 500 millilitres, but if it's less than that, make sure that you're using the same amount in each site.

And you need to have the same starting conditions.

That means that we make sure that each site is comparable with another.

Now, you might have chosen C as well, that you're gonna survey the sites at exactly the same time.

Now, yes, you'd want to survey the sites on exactly the same day, but maybe not exactly at the same time.

It's important that you survey them on the same day, because we need to make sure that there's not been any rainfall in between the surveys.

Now, a data collection sheet can be used to record the data in the field.

Here's an example of one that's available to you.

The site name or number tells the geographer where the data is being collected.

The number of strikes tells the geographer how compact the soil is.

And remember, the higher the number, the more compact the soil is.

The infiltration column.

That value tells the geographer the number of seconds it takes for 500 millilitres of water to infiltrate into the soil.

The lower the value, the faster the rate of infiltration.

And then finally, the soil type columns.

This shows the composition of the soil in percentages, and indicates the size of the particles that make up the soil.

Remember, sand is the largest particle, and clay is the smallest.

Izzy is trying to work out where to do her soil texture surveys.

She wants to cover as much of the school site as possible, but she knows that she's only got time for four surveys.

She says, "I'm going to divide our school site into four equal parts using a grid.

Then I will do a soil texture survey as close to the centre of each square as possible." There is a system to how Izzy is choosing her sites, and so, this is known as systematic sampling.

True or false now.

Izzy has chosen her data collection sites randomly.

Is that true or false? Pause the video, have a think, and then come back to me.

Well done if you recognise that's false.

Now tell me why.

Yes.

So Izzy has chosen her data collection sites systematically.

Now your practise task for this lesson.

Look at your own map of your school site.

Use a grid to divide the school grounds into four equal areas.

Choose a location in each grid square where a soil texture survey, that means the infiltration survey, the compaction survey, and the soil type survey, can take place.

Carry out a soil texture survey at each survey location using a copy of the data collection sheet.

What I'd also like you to do though, is make a note of any things that you would change about the way you collected your data if you were to do it again.

So reflect on that when you come back inside and have actually completed your data collection.

Of course you're gonna want to pause the video so that you can get out there and collect some data, but do come back to me and I'll run through some ideas that I've got as well.

So your first task was to decide where you were going to be doing your data collection and where those survey sites were going to be in your school grounds.

Hopefully you've got something like this where you've got a plan of your school site, and you've got the four data collection sites clearly marked in each grid square.

Then you went outside and actually collected some data, but you also made a note of the things that you would change about the way that you collected it.

So here's some things that you might include in your answer.

We found it really hard to make sure we were hammering the auger into the ground with the same force each time.

We decided that the same person should do it each time to try to make it even.

A sensible adjustment has been made to this method.

We realised that because we were not washing the soil auger between the sites, there was the potential for soil from one area to be measured in another.

Let's now summarise our learning for today's lesson.

A soil texture survey helps geographers understand the relationship between soil type, infiltration, and soil compaction.

When doing comparisons, geographers often choose their sites systematically.

They make sure they use identical methods and equipment when collecting their data.

Well done for, first of all, planning a piece of field work, but also going out there and collecting some data on soil texture.

The theory associated with this piece of field work is relatively straightforward, but I wonder if our data is gonna follow that theory exactly?.