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Authors: Professor Dr. Tasnee Attanandana Dr. Prateep Verapattananirund Professor Dr. Russell Yost Illustrator: Wasinee Chantakorn

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Part 1: Our Earth It is a beautiful morning and Nidnoi is very excited because Uncle Pracha will take her to his home in the country during the school vacation. Uncle Pracha brings Pom, her cousin whom Nidnoi has not seen for a long time. My parents often talk about Uncle Pracha being a modern farmer as well as a community leader. This will also be my first trip to the country so I am really excited. Ding dong. Look! they are here. Hello Nidnoi, you’ve already grown up since I last saw you! Good morning Uncle Pracha. Hello Nidnoi. Good morning, Montri and Orr. I would like to ask for your permission to take Nidnoi to my farm for a few days. Sure, Pracha. Nidnoi has been so excited these last few days that she could hardly sleep last night. Nidnoi, be a good girl, and don’t be stubborn or naughty. Yes. 3

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OK, children, are you ready? Yes, we certainly are, Uncle. t e g s ’ lete car. So in th ye. B . e By Have a safe trip. Nidnoi, look at that. What? Oh My, it’s pretty. Over there is a fisherman. This is so much fun. I have never traveled this far before. We are passing beautiful scenery. I have only seen waterfalls, mountains, and seas on television. This is the first time I’ve seen the real thing. Nidnoi, you know, there are so many beautiful things in our world! And they are even prettier than on TV. Do you know how the earth was made? No, Uncle, how was the earth made? 4

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Our earth is about 4,600 million years old. Scientists believed that the earth used to be part of the sun that later disintegrated and gradually cooled down. Its surface turned into hard rocks but the inner core remained hot rock, so hot that it is molten like a liquid. About 3,500 million years ago, one-celled organisms started to occur in the sea followed by green algae and bacteria. About 1,150 million years ago hard-shelled animals including mollusks, coral, and starfish began to appear. Plants attached to sea algae appeared 590 million years ago. They were brought to shore by sea waves where they became attached to the rocks. The plants grew and spread. They helped cause the rocks to disintegrate into soil. 590 million years ago 3,500 million years ago 1,150 million years ago Plants and animals appeared on land and, together with warm temperatures and water, aided in more soil formation. With the presence of soil, a variety of terrestrial plants and animals developed. Dinosaurs and later human beings developed. The soil layers gradually became deep and thick. They supply four essential requisites of human beings; food, clothes, home and medicine. Children, our destination is round the next curve. Part 2 : Soil I like to grow trees. Trees help make the air pure and cool. Oh My! You have many trees and it is so nice and shady. 5

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Woof woof! Oh! I forgot to introduce our companion. This small dog is called “Jao Dang” How cute! Hi, Jao Dang. I took Jao Dang in when she appeared one day in front of the house. I was afraid she would be hit by a car. She is a wise dog. OK. Children! Come this way. I will take you to the farmers’ fields over there. Wow! This is so exciting. Look at Jao Dang, she is leading us to the farmers’ plots. Ha ha. What are they doing over there, Uncle? It looks quite interesting. She really is a smart dog! Ah! They are digging a new well. Look at the soil which was dug up. The soil has many layers that tell us much about the possible uses of the soil and sometimes, how it was formed. 6

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We notice that the surface soil is often darker in color than the deeper soil layers. This darker layer is often the result of old, disintegrated rock, residues from long dead plants and animals Soil layers At the deep levels of the soil, above the parent rock, the rock is decaying and disintegrating. At the deeper layers of soil, even deeper than the parent rock you can usually find the “bedrock”. This is the rock layer that has not yet decayed and disintegrated. Most plant roots grow and take up soil nutrients from the surface soil layer only. The deeper levels of soil, help support the plant roots and retain moisture that can be used by the plant. Children, do you know why soil is important for us? It’s used for growing vegetables and fruits. Soils often differ in depth. In deep soils, where the surface layers are thick, there is more space for plant roots to absorb more nutrients than in shallow soils where the surface layers are thin. It’s not only just for growing vegetables and fruits. Soil is the source of four good things that humans need: food, clothes, home and medicine. In addition, soil is the life-base of farmers. Soil is a little bit like the air we breathe, if we take care of it and don’t destroy it, it will be with us all of our lives. Just like we need to learn to keep air clean of smoke in order to use it, we need to keep the soil in good condition so it can continue to provide us with food, clothes, medicine, and a home. Oh, I see. So then how is soil formed? 7

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Soil has been developed from old, decayed rock mixed with plant and animal parts for millions of years. It is a natural resource that can not be rebuilt. Soil is thus a valuable resource that we should maintain and conserve. Oh My! How do you know? It’s wonderful you understand so much! My teacher has assigned us to do a report on soils during the school break. That’s how I know. Well! Excellent! So let me help you remember by telling us again. Please tell me and Nidnoi what the soil is made of. Quite easy. The soil is made of the following, which helps plants grow: Old, soft, decayed rock =45% Old, dead and decayed plants =5% Water =25% Air =25% Each of these parts of soil does important things: soil nutrients to plant roots where they can help plants grow. Water dissolves and carries Air gives oxygen to plant roots for respiration. The old, soft, decayed rock is a source of plant food. help the soil become loose, stay moist, and be easy for roots to grow in, they are also the food for tiny soil animals and plants. 8 Old, dead and decayed plants

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Very good. Wow! Pom knows a lot about soil! Eh! How can we know which soil is good, sir? Pom, can you answer that? Yes, very easy. Good soil has four things about it, isn’t that right, sir? (2) A good soil is not acid, or alkaline or salty, (nothing that stops growth, good chemical properties) (1) A good soil has plenty of plant nutrients (plenty of “food” for plants!) (3) A good soil is easy for plant roots to grow in, (loose and easy for roots, good physical properties (4) A good soil has small creatures that help the plant grow, (many small helpful creatures, good biological properties) You are right, Pom. Good soil or soils which plants grow well should be like that. That means we add fertilizers to soil in order to add more plant food so plants can grow bigger and stronger. This helps the soil become more fertile, right? Therefore, adding fertilizers (plant food) helps plants grow but the soil needs to be loose and easy for roots to grow in, have none of the things that stop plants from growing, and have many small helpful creatures. 9

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So you mean that a fertile soil is not always a good soil, but a good soil must be a fertile soil. It sounds a little complicated. We have to start by determining which of the four things about soil causes it to be a poor soil, and then we can improve those things. We start by asking questions. For example: So how do we improve a poor soil, sir? ?? chemical fertilizers marl Does the soil contain sufficient plant food? We must determine how much plant food the soil contains: what levels, if low, chemical fertilizers should be applied Is the soil too acid or alkaline? If the soil is acid, then marl or a limestone material can be added (liming). If the soil is too alkaline, then treat the soil with an acid material. If the soil is too salty, the salt must be removed, perhaps by applying lots of water so that the water moves down through the soil. compost green manure manure old, dead and decayed plants Is the soil loose and easy for roots to grow in?“ Soils that are so hard that water does not soak in will not allow roots to grow normally. Dead and decomposed plants and animal parts; compost, manure and green manure should be added and mixed into the soil. 10 Does the soil contain many small creatures that help plant grow? Soils usually contain many tiny plants and animals, many of which are so small that they can not be seen. The bacteria mixed with legume seeds prior to planting will help plant obtain food from the air. The old, dead unused plant and animal parts can be added to the soil to increase the food for bacteria.”

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Soil in the forest usually is fertile because the tree roots take up nutrients from the soil to grow the leaves, fruits, stems and branches, and when the trees die, these plant parts fall onto the soil and decay, nutrients are released and become ready for use by new plants. When it rains, such nutrients will be removed to the deeper layer of soil as the water flows through the soil. From there, new plant roots will again take nutrients up for their growth. This cycle will go on and on. Why is soil in the newly opened forest good for growing plants and producing good yield, sir? nutrients In soils used for agriculture, the nutrients are used up by the food plants and when we collect the food plants, we also take away the nutrients in the plants from the soil. In this way the soil loses nutrients because they are taken away in the food plants. So, without returning nutrients, a good agricultural soil can eventually become poor soil. Do the different kinds of plants use different amounts of nutrients, sir? 11

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Different plants need different kinds and also different amounts of nutrients. For example: 1 ton of rice grain removes 12 kg of nitrogen, 3 kg of phosphorus and 3 kg of potassium from the soil where it is grown. There are even more nutrients removed in the straw, stem and roots needed to produce the rice grain. Therefore, returning the straw, stems, and roots to the soil helps to keep the soil fertile. Nidnoi, if you don’t understand anything, please ask. Yes sir. (Scream!!!) earthworms! Ha, Ha! Nidnoi, are you afraid of earthworms? Be careful!. Try to avoid stepping on earthworms. Please do not be afraid of them. Did you know that earthworms are some of the many small creatures that are useful to soil? Earthworms loosen up the soil and improve it since they dig through soil making the soil loose, more open, and easy for roots to grow in. When earthworms die, they will be decomposed and return the nutrients in their bodies to the soils. What about nutrients in soil, where do they originally come from? Pom. Soil nutrients (plant food) come from rock that becomes old and soft, soil minerals, plant and animal residues. Soil in newly-opened forests is usually good soil with lots of plant food, water, and air which help plants grow well. nutrients 12 nutrients

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When forest is prepared for agricultural use, not only is the plant food removed when crop plants are harvested and the food is eaten, but nutrients may be lost from the area when rain seeps into the soil or when the rain carries soil away during a storm. The loss of soil nutrients in surface soils may result in the loss of so many nutrients that the plant no longer grows well.. Plants need 17 essential nutrient elements Uncle Pracha, and water : provide the elements carbon, hydrogen, what are the essential -Air and oxygen. foods for plants? -Soil: provide nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, manganese, zinc, copper, boron, molybdenum, chlorine, and nickel. Amazingly, the soil usually contains enough of the elements or plant foods for good plant growth. Of the large num- ber of elements mentioned here there are three that are special because they are needed by plants in large quantities and often soils do not contain enough of these elements for the plants to grow at their best. This I know, sir. I have learned about this in my class about agriculture Nitrogen (is shortened to N), phosphorus to P, and potassium to K. This makes it easier to remember (NPK)! That’s right. Every nutrient element that we have mentioned is equally important. Without even one of these elements a plant cannot grow. You will be interested to know that each of these nutrient elements is used in different ways by the plants. Children, are you tired yet? Let’s rest over there and then I will explain about the nutrients, Nitrogen, Phosphorus, and Potassium, and how the plant uses them differently. 13

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Nitrogen helps plants become strong and increase crop yield. Plants can not grow stems and leaves without it. If there isn’t enough, the yield decreases. On the other hand, if there is too much nitrogen, the plant may grow too fast, become weak and fall over. Potassium helps plants grow strong stems and helps the plant resist diseases and insects. If there is not enough potassium in the soil, in the case of rice, more unfilled grains will be obtained. If potassium is not enough for corn, there also will be grain that does not complete its growth and the cob may have no grain in some places. Phosphorus helps the growing roots, flowers, and making grain, fruits, and other plant parts. If there isn’t enough phosphorus in the soil the plants will be small and have thin stems, will not flower as early, and the grain or fruits will not ripen as fast as normal. Yay, very good indeed. Uncle Pracha has made it easier to understand in this briefing than reading by myself. Ha, Ha, I am going to put what Uncle Pracha told us in my report. Pracha, why can Pom, why didn’t you Uncle plants grow better in loamy read it yourself? soils than in clayey or sandy soils? The way sandy, silty and clayey soils are different from one another is because of the size and how the soil particles fit together to form spaces in the soil or pores. - Small pores or micropores are filled with water and may hold the water too tightly for the plants to use. - Large pores or macropores are filled with air, not water, and therefore, do not hold water for plant use. Well-structured or loamy soil has about 50% pores. One half may be small pores while another half has large pores. About 45% of the soil is composed of old, decayed, crumbled and crushed rock. The remaining 5% is old dead plant and animal parts. 14

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