hi guys welcome back today we're on to our fifth episode of the series where we're going to be looking at soil and food production systems so trying to apply the system's approach once again to soil so something that's very important for overall Earth's functioning so to start with what is soil well so is a very complex ecosystem where plants grow animals eat habitat for many microorganisms which can hold minerals and nutrients it can filter water and it stores and transfers heat so you can already see there are few similarities here with an ecosystem for example it is a habitat there's stores and transfers these are components of a system and it can be considered also a non-renewable resource so non-renewable meaning that it takes a long time to replenish and therefore it's hard to use at a sustainable rate so this should give you a little bit of an overview on kind of the the interesting resource and the interesting system that soil is and there there's a variety of approaches to take when looking at so in more detail so what we have here is a diagram of what can be considered the five key spheres on earth beginning with biosphere or living things which is what we went over in topic 2 the hydrosphere so the water cycle what we talked about in the last episode and now we're going to come to the pedis fear so soil systems the two remaining are atmosphere which we will be looking at next week and life the sphere which concerns Rock cycles which we don't look at in the ESS syllabus but is equally as interesting and important so you can see they were applying the systems approach to four of these five spheres so what are some transfers and transformations in soil then since we are applying it the systems approach here and it is an open system what are the transfers and transformations well the transfers in terms of inputs are organic and parent material precipitation infiltration through the soil layers and energy as well the outputs include leaching so when minerals or water are leached out of the soil uptake of nutrients by plants as well and mass movement in terms of transformations we have decomposition weathering and nutrient cycling including carbon and nitrogen cycles so again because of the transfers and transformations going on we can conclude that it is an open system this is what a soil profile looks like the IB want you to be familiar with the different layers and be aware of how they change through the layers starting with the bedrock moving to the parent material subsoil alluvion or horizon and then the topsoil and just by looking in this image you can see how the consistency and what's going on in each of these layers is vastly different so now let's move on to soil texture now slow is composed of four main components mineral particles organic remains water and air so the mineral particles are mainly from underlying rocks organic remains come from dead plants mainly and then water and air in the spaces between the pores and on the right here I have a also known as a triangle about soil composition and there being way to be able to read off what exactly the consistency of a sample of soil would be and you can see on the Left we have percent clay at the bottom percent sand and on the right percent silt and you literally just read it off with a ruler like that and in this diagram you can already see in the centre something called loam and right before I went to my exams I remember the first the one thing I wanted to remember is that loam is good and what do I mean by that well let's discuss so on that left here I have a diagram showing you the different sizes of particles depending whether you have sand or clay particles of soil so you can see that the sand is much larger than the clay what that means is when you have a large proportion of these particles together on the diagram on the right you can see that clay particles are much more compact together and there's much less space between particles sound on the other hand there is a lot of space between particles because they can't be as compact together in the same way so what are the implications well it means that sand compared to clay has much more free drainage of water in between the pores because of these large spaces spaces due to the large pores clay on the other hand has restricted drainage so as we will see in a second both of them have weaknesses because of their features so what are the implications then for primary productivity let's remind ourselves that primary productivity is the rate at which energy is created by autotrophs by the first robic level via photosynthesis well it's dependent on a few factors spending on mineral content drainage of water in contrast water holding capacity the spaces between the pores the biota sand the living things and the potential to hold organic matter so thinking about the different sizes of the particles have a thing and pause the video if you want about which would be best for all of these different features well the answer is it's a mixture of the two extremes so sand as we went over has very large pore size which leads to a lot of water filtering true filtering through very quickly and basically leaching out all of the nutrients so there's no potential to hold any water at all and very little plant growth as a consequence which renders the productivity very very low clay on the other hand has the opposite problem so the pores are way too small to allow any drainage so there's too much retention of water however it's too small for any biota to live there and that's in the end in that way the productivity is limited so what we need instead is loam the perfect balance which has a mixture of sand and clay particles so it makes use of the water retention capacity of clay particles but also because it has some larger particles allows for air spaces for biota to establish itself and this leads to the highest available productivity so now I want to move a little bit away from soil to talk about food production systems and the first thing that the IB do in this section of the topic and I'd like to do as well is to distinguish a few terms starting with extensive versus intensive farming so extensive is low inputs low outputs whereas intensive is more concentrated high inputs high outputs type of farming the distinction between past role and arable is that past role is raising animals on lands that aren't really suited for crops whereas arable is growing crops on land so this difference between animals and crops and again for feet and then finally the distinction between subsistence farming and commercial farming they're kind of related to extensive versus intensive is that subsistence farming is basically enough just for to feed your family so usually based on poly culture so using lots of different crops so as to not to punish the soil of nutrients whereas commercial farming is farming for profit so very intensive monoculture where you just crop one type of crop and a large scale as well and the main message when it comes to free production systems is that there is enough food but an imbalance in how it is distributed and there's also an issue where culturally so cultural factors that influence our decisions when it comes to harvest of food lead to a large type of harvesting from higher trophic levels and if you remember from topic 2 there's very inefficient transfer of energy between trophic levels which means by the time you get to our trophic level as you can see in this diagram we've already lost a lot of energy in between those previous trophic levels as there is 90% energy loss between them and I want to briefly mention something about aquatic food production systems which is interesting because most food comes from higher trophic levels so minimum fourth or higher and although the conversions between trophic levels is more efficient in water systems the initial intake of energy is lower because of absorption and reflection of reflection of solar energy by water so aquatic food production systems are interesting to consider because of those two aspects and the final thing I want to tell you guys about is how we can increase sustainability of food production systems and hopefully you can see that eating at lower trophic levels so reducing meat consumption an increasing consumption of locally grown food would increase sustainability also improving labeling so allowing consumers to make more informed choices about where their food is coming from and what is in it and then at a higher level monitoring and controlling practices by a national and most national food corporations so these are ways that we can increase sustainability so that concludes episode 5 but go ahead and click on episode 6 to hear about the atmosphere as a system and as always guys make sure to check out our website to learn how I and others can become your tutor as well