Need to know about soil
- Healthy soil can improve air quality by taking CO2 out of the air
- There is not one particular ‘healthy soil’ as different soils are good for growing different things e.g for growing vegetables lots of nitrogen, phosphorus and organic matter is needed
- Soil supports all food production
- Too large a quantity of nitrogen, phosphorus and other nutrients can end up in waterways and rivers. This causes algae growth which pollutes the water and kills the fish living in it
- The pH of soil can impact the growth of particular foods and plants e.g the pH for growing blueberries should be around pH 4 and grass pH 6
- You can observe the nutrient status of soil by looking at the plants e.g the leaves on tomato plants will turn slightly purple when the soil is potassium deficient
- You can observe the soil structure and health by doing a simple Visual Soil Assessment
- Avoid spraying soil with fertilizer if the soil is really close rivers or water ways
- Nutrient status can be determined by a simple pH test
- Compost made from grass cuttings, leaves, and sticks is very beneficial to the soil because the leaves provide potassium in the compost and the sticks and grass are full of nitrogen. Compost is also full of worms and their casting (poo) is really good for healthy soil and therefore plant growth.
- Clay soil is soil that has been excessively compacted (by walking on it) and although it is full of nutrients, there is no accessing of the roots.
- To make grass grow on clay soil, add compost make from grass, leaves and sticks
What makes healthy soil?
Us: So what makes healthy soil? Such as the nutrients in it?
Louis: Right. So, the thing about healthy soil is that it depend on what you want to use it for. Because, different soils are good for different things, right? So if you want to grow vegetables, you want have what’s called good soil tilth, which is if you look at soil, go out and have a look sometime, and have look you’ll find little crumbs about that big *gestures to a small circular shape about the size of a pinky fingernail* of soil that kind of hold together? And if you have that nicely distributed throughout the soil, it’s very easy for plants to grow their roots through that, and those little balls (they’re called aggregates) they hold on to nutrients, they hold onto soil organic matter which is really important to give you good food production, right? But, if you want to grow kauri trees, or a native forest, you actually want really low nutrient content in the soil, and maybe poor drainage so it’s wet all the time, which is not a good thing for growing vegetables, alright? So, so what makes it good soil depend on what you want to use it for. If you want to grow vegetables, you need this good soil tilth, lots of nitrogen, phosphorus, you need lots of organic matter, organic matter is the broken down bits of roots and leaves, insects and all that soil that hold on to the nutrients that binds the soil together acts like a bit of a glue, so that’s if you want to grow vegetables. If you want to grow different things like kauri forest or natives forest, you want something that has much lower nutrients in it and might be more poorly drained and more wet and that’s good for those trees. So it differs. That make sense? You’ve got to match the soil to what you want to use it for. The key properties are the amount of nutrients you have, how much water it has, and what sort of a structure it has, how it’s kind of clumped together. Alright?
Our Research:
The structure of soil is important for plant growth and regulating the movement of air and water. It influences root development and has an effect on nutrient availability. Good quality soils are friable (crumbly) and have fine aggregates so the soil breaks up easily if you squeeze it. Poor soil structure has coarse, very firm clods or no structure at all. Soil porosity refers to the pores within the soil. Porosity influences the movement of air and water. Good quality soils have many pores between and within the aggregates. Poor quality soils have few visible pores, cracks or holes. Earthworms improve soil porosity through their burrowing. They also help with nutrient cycling and supply. Earthworm numbers tend to be lower in compacted or pugged soils.
Louis: Right. So, the thing about healthy soil is that it depend on what you want to use it for. Because, different soils are good for different things, right? So if you want to grow vegetables, you want have what’s called good soil tilth, which is if you look at soil, go out and have a look sometime, and have look you’ll find little crumbs about that big *gestures to a small circular shape about the size of a pinky fingernail* of soil that kind of hold together? And if you have that nicely distributed throughout the soil, it’s very easy for plants to grow their roots through that, and those little balls (they’re called aggregates) they hold on to nutrients, they hold onto soil organic matter which is really important to give you good food production, right? But, if you want to grow kauri trees, or a native forest, you actually want really low nutrient content in the soil, and maybe poor drainage so it’s wet all the time, which is not a good thing for growing vegetables, alright? So, so what makes it good soil depend on what you want to use it for. If you want to grow vegetables, you need this good soil tilth, lots of nitrogen, phosphorus, you need lots of organic matter, organic matter is the broken down bits of roots and leaves, insects and all that soil that hold on to the nutrients that binds the soil together acts like a bit of a glue, so that’s if you want to grow vegetables. If you want to grow different things like kauri forest or natives forest, you want something that has much lower nutrients in it and might be more poorly drained and more wet and that’s good for those trees. So it differs. That make sense? You’ve got to match the soil to what you want to use it for. The key properties are the amount of nutrients you have, how much water it has, and what sort of a structure it has, how it’s kind of clumped together. Alright?
Our Research:
The structure of soil is important for plant growth and regulating the movement of air and water. It influences root development and has an effect on nutrient availability. Good quality soils are friable (crumbly) and have fine aggregates so the soil breaks up easily if you squeeze it. Poor soil structure has coarse, very firm clods or no structure at all. Soil porosity refers to the pores within the soil. Porosity influences the movement of air and water. Good quality soils have many pores between and within the aggregates. Poor quality soils have few visible pores, cracks or holes. Earthworms improve soil porosity through their burrowing. They also help with nutrient cycling and supply. Earthworm numbers tend to be lower in compacted or pugged soils.
Why is healthy soil important for a sustainable world?
Us: Why in you opinion is good soil important for a sustainable world?
Louis: Well, I mean, because all of our food comes out of healthy soil. You need to look after your soil, right? And also, if you want to have all that food production without all that environmental impact or by minimizing that environmental impact you’ve got to have good soil. And one do the funny things about good soil is, well, do you know why Hamilton is built where it is? It’s because we have great soil! And in Auckland there’s some great soils and many of the bigger cities of the world. Or the most important cities in the world. Or where people originally settled because they went “Ah, there’s some really good soil here. We can grow lots of food here. So let’s stay here!!!” And so they built a town there and then the town gets bigger because they produce lots of food and all that sort of stuff. And then the unfortunate thing is that, we see this everywhere in the world, is that the city gets bigger and bigger and bigger and goes over all the good soil. So you lose your best soils. So that’s happened in Hamilton and it’s happened up in Auckland as well where a lot of houses are now being built on excellent soils for growing food. So in terms of a sustainable world, food production and food comes from soil.
Louis: Well, I mean, because all of our food comes out of healthy soil. You need to look after your soil, right? And also, if you want to have all that food production without all that environmental impact or by minimizing that environmental impact you’ve got to have good soil. And one do the funny things about good soil is, well, do you know why Hamilton is built where it is? It’s because we have great soil! And in Auckland there’s some great soils and many of the bigger cities of the world. Or the most important cities in the world. Or where people originally settled because they went “Ah, there’s some really good soil here. We can grow lots of food here. So let’s stay here!!!” And so they built a town there and then the town gets bigger because they produce lots of food and all that sort of stuff. And then the unfortunate thing is that, we see this everywhere in the world, is that the city gets bigger and bigger and bigger and goes over all the good soil. So you lose your best soils. So that’s happened in Hamilton and it’s happened up in Auckland as well where a lot of houses are now being built on excellent soils for growing food. So in terms of a sustainable world, food production and food comes from soil.
So what makes healthy soil? Such as the nutrients in it?
Louis: Right. So, the thing about healthy soil is that it depend on what you want to use it for. Because, different soils are good for different things, right? So if you want to grow vegetables, you want have what’s called good soil tilth, which is if you look at soil, go out and have a look sometime, and have look you’ll find little crumbs about that big *gestures to a small circular shape about the size of a pinky fingernail* of soil that kind of hold together? And if you have that nicely distributed throughout the soil, it’s very easy for plants to grow their roots through that, and those little balls (they’re called aggregates) they hold on to nutrients, they hold onto soil organic matter which is really important to give you good food production, right? But, if you want to grow kauri trees, or a native forest, you actually want really low nutrient content in the soil, and maybe poor drainage so it’s wet all the time, which is not a good thing for growing vegetables, alright? So, so what makes it good soil depend on what you want to use it for. If you want to grow vegetables, you need this good soil tilth, lots of nitrogen, phosphorus, you need lots of organic matter, organic matter is the broken down bits of roots and leaves, insects and all that soil that hold on to the nutrients that binds the soil together acts like a bit of a glue, so that’s if you want to grow vegetables. If you want to grow different things like kauri forest or natives forest, you want something that has much lower nutrients in it and might be more poorly drained and more wet and that’s good for those trees. So it differs. That make sense? You’ve got to match the soil to what you want to use it for. The key properties are the amount of nutrients you have, how much water it has, and what sort of a structure it has, how it’s kind of clumped together. Alright?
Are there any problems with bad nutrients in the soil at the moment?
Sure. If you have too much nutrients in the soil, and we put a lot of fertilizer on some of our agricultural land, that supports production and makes cheap food for us (and we all like to eat). But if you get too much nutrients, they don’t stay where they’re put. Particularly nitrogen but also phosphorus - they’re two of the key nutrients you need for growing plants. For nitrogen, it will what’s called leach down through the soil profile, so it will move down the soil and hit ground water which might be a meter or tens of meters below the surface. And then it will move with that ground water to streams and rivers and lakes and then pop up there. Now what you’ve done is the nutrients and fertilizer you put on to the land is now, some of it, in waters. And there it acts as a fertilizer as well. Right, so then you get algal growth, and you don’t want algae growing, you know you get green looking kind of rivers, and you don’t want to swim in that, ay? And it’s not good for drinking. So if you have too much nutrients it’ll move away from the land and end up in the waterways. And then of course there is unwanted algae growth which then kills fish. Yeah, so you know United States, in the Mississippi basin, which is this huge area that goes back up off the Gulf of Mexico and all the Gulf of Mexico drains down the Mississippi and ends up in the Gulf of Mexico. Every year there’s is an area, about the size of the Waikato which becomes what’s called the ‘Dead Zone’, where there’s too many nutrients that have gone in there and you get these big algal growths and then the fish are not very happy. So it’s a quite a large global issue. If you have too much nutrients, it will leave the land and end up in waterways and causes pollution. So it’s about balance you have got to have enough nutrients if you want cheap food, but too much nutrients and it ends up in the waterways. So the nutrients and fertilizer are not bad, it’s about how much. It’s like sugar.
How can you tell the state of soil? Do you test it in a lab?
Yeah, so again it depends on what you’re looking for. But if you’re looking particularly for how much fertilizer to put on, then you’ll take samples and send to somewhere like Roger Hill’s Laboratories, and they’ll analyze it for specific things particularly phosphorus, and what they call base cations. Base cations are calcium, magnesium, sodium and potassium. And you’ll need all those as well, they’ll test it for that and they also measure for pH which is how acidic or how alkaline it is. Depending again on what you’re wanting, then you adjust the soil. So for example, pH is a really good one. pH is how acidic or how alkaline it is. If you want to grow blueberries, you want to have a pH of about 4, which is quite low, it’s resonably acidic. If you want to grow grass, you want to be around pH 6. If you want to grow truffles, do you know what truffles are?
Yeah truffles are a fungi that grows on oak trees, on the roots, and they form these little balls and like those little balls they like tat might be worth a few thousands of dollars cause they plane it onto food cause it releases aromatic...i don’t know, something. So if you want to grow truffles, you need a pH of the soil at around 10. So you test the soil, and find out what you have got, and then you have to figure out if that matches with what the plants you want to grow, want. So it isn’t like there is one soil that is great for everything.
Yeah truffles are a fungi that grows on oak trees, on the roots, and they form these little balls and like those little balls they like tat might be worth a few thousands of dollars cause they plane it onto food cause it releases aromatic...i don’t know, something. So if you want to grow truffles, you need a pH of the soil at around 10. So you test the soil, and find out what you have got, and then you have to figure out if that matches with what the plants you want to grow, want. So it isn’t like there is one soil that is great for everything.
Is there a way to analyze the quality of soil without using lab testing?
Yes, there’s something, but it’s not going to tell you about nutrient content too much, but there are two different ways. You can test the soil to find out how much nutrients you’ve got or you can look at the plants. If the plants aren’t looking very well, it’s quite likely that there is a nutrient missing and very good people, who have done this for years with pastural systems, you know like agriculture with cows and stuff, they can usually tell nutrients are missing by looking at the plants. Like for example, tomato plants will go slightly purplish on the leaves if they are potassium deficient. So you can tell if you go into a pasture and you really know what you’re doing, I don’t do this stuff, you can look at the plants and you’ll get a sense that “Oh, this is probably deficient in this or that or this” Alright? So that tells you about nutrient status without testing the soil. So the other thing you can do to look at soils is something called a visual soil assessment (VSA) and you can look that up online it’s in the science learning hub, I don’t know if you’ve looked there, but it’s done by the university of Waikato and there’s a whole section there on soils and farming that’s got exercises you can do and stuff. One of those exercises is the visual soil assessment. So you can go on there and you can see how to do a VSA. All that requires is a spade, and essentially a tub. And then basically what you do, is you get out a chunk of soil about that big * roughly 20cm long* of topsoil and then you drop it 3 times in a row until it falls apart and then you look for the aggregates ( the little crumbs of soil) and you organize it and then you compare it against sample photos and that will then tell you about the physical health of the soil. So look that up, Visual Soil Assessment. My wife wrote that exercise and its based on some work that was in a science organization in New Zealand. So it’s a really nice way of doing it.
How is soil quality and greenhouse gasses related?
So, with greenhouse gases there are three main ones. Well, the three main ones we can affect, which are: carbon dioxide, nitrous oxide, and methane. And all of those interact with soil. So, the organic matter that I was mentioning before in soil, that’s just carbon, and that’s exchanging - the plants take CO2 out of the air and convert it into leaf material and roots and that enters the soil and that can be stabilized in the soil. So, you might end up sort of banking CO2 in a different form as organic matter in the soil. So that will be good, because you can get CO2 out of the atmosphere. And in fact, of the fossil fuels that we’ve burned we don’t find as much CO2 in the air as we think there should be. But a lot of that because it has been captured by plants growning and it’s gone into the soil. So that’s one thing soil does. Nitrous oxide gets produced in soil. It’s a really important greenhouse gas. It’s produced and consumed in soil so if you can make sure that you minimize the production of nitrous oxide, then you can decrease the impacts of the greenhouse gas. So soil has a very key role to play in managing climate change.
Terminology
Aggregates- naturally occurring clusters of soil
VSA - Visual Soil Assessment
pH- how basic or how alkaline a material or substance is
Tilth - the physical condition of the soil e.g moisture content
VSA - Visual Soil Assessment
pH- how basic or how alkaline a material or substance is
Tilth - the physical condition of the soil e.g moisture content