SOIL
During his ESS class, Chinmay walks through the school garden and notices how the ground beneath his feet supports tiny plants and insects. Curious, he asks RUPAL mam, “What exactly is soil?”
Soil is far more than just dirt; it's the foundation of life on Earth, a thin layer between the atmosphere and the lithosphere. It nourishes our plants, filters our water, and plays a vital role in combating climate change.
During lab class, Aaryaman examines a handful of soil and notices it’s made of different materials. He asks, “What are the main components that make up soil?”
Soil is made up of mineral particles, organic matter, air, water, and living organisms.
While feeling soil in the school garden, Aarush notices some soils feel gritty and others smooth. He asks, “Which property describes how coarse or fine soil feels?”
It describes the proportions of sand, silt, and clay, determining how coarse or fine the soil feels.
While walking in the school garden, Aaryaman notices small pieces of rock breaking off from bigger rocks. He asks, “Which process breaks down rocks into smaller particles to form soil?”
Weathering
During ESS class, Aarush asks, What does it mean when we say soil is a system?
a natural system made of inputs, outputs, and stores, where matter and energy flow and interact to support life.
During a school field trip, Shanarika observes how rainfall, roots, and worms constantly change the ground surface. Her friend Aaryaman asks if soil ever “stays the same.” Shanarika smiles, remembering her ESS class. “Wait… soil is always exchanging things with its surroundings! But what kind of system is it, and why?”
Soil is an open system because it continuously exchanges matter and energy with its surroundings through inputs like organic matter, precipitation, and sunlight, and outputs like erosion, leaching, and plant uptake.
While observing soil samples, Chinmay notices how some soils are sandy while others are sticky. He wonders, “Which 2 property determines how fine or coarse soil feels?”
It describes the relative proportions of sand, silt, and clay in soil.
It determines how coarse, smooth, or fine the soil feels and affects drainage and nutrient holding
Shanarika pours water on two soil samples — one soaks quickly, the other slowly. She wonders, “Which property explains how easily water moves through soil?”
Permeability is how easily water flows through those spaces.
Shanarika observes leaves and twigs decomposing on the forest floor. She asks, “How do dead plants contribute to soil formation?
Organic matter accumulation, decomposed plants and animals add nutrients and improve soil structure, helping form fertile soil.
Shanarika notices plants growing better in some soils than others. She asks, How do soil systems support ecosystems and human activity?
Soil supports life by providing nutrients, water, and habitat for organisms, controlling ecosystem productivity, and supplying resources for agriculture and humans.
While preparing for her ESS presentation, Khyati studies how soil connects to everything — air, rocks, water, and living things. She wonders, “How does soil actually link all parts of our planet together?”
Soil connects the atmosphere through gas exchange, the lithosphere through minerals and rock weathering, the hydrosphere through water storage and filtration, and the biosphere by providing habitat and nutrients for living organisms.
While digging a soil pit for class, Khyati notices that the soil looks darker at the top and lighter as she goes deeper. Curious, she asks, “What are soil horizons and the soil profile — and why does soil change in layers as we go down?”
Soil forms different horizons (O, A, B, C) because of weathering, organic matter, and leaching.
These horizons together make up the soil profile, showing how soil develops over time.
The upper layers are richer in nutrients and life, while the lower ones contain more minerals and are compact.
While digging a pit, Khyati notices that some soil layers are loose and crumbly, while others are hard and clumpy. She asks, “Which soil property describes how particles group together, and why does it matter?”
Soil structure it describes how soil particles form aggregates, affecting air and water movement, root growth, and fertility.
Rupal digs a small pit and sees worms and roots constantly turning the soil. She asks, “What is the process by which organisms help form soil, and how does it work?”
Bioturbation
it’s the process where soil organisms like worms, insects, and roots mix and disturb soil. They break down organic matter, nutrients, and create air spaces, improving soil structure, fertility, and water movement.
Aaryaman measures soil temperature in the garden and asks, “How does solar energy affect soil processes, such as water movement, decomposition, and nutrient cycling?”
solar energy warms the soil, drives water movement and evaporation, powers photosynthesis in plants, and influences decomposition and nutrient cycling, connecting the soil to ecosystem processes.
While revising for her ESS exam, Gatra thinks beyond how soil supports plants. She realises soil also helps ecosystems function on a larger scale — filtering water, cycling nutrients, and storing carbon. Curious, she asks: “What major ecosystem services does soil perform, and why are they vital for environmental stability?”
Soil supports primary productivity by supplying nutrients and anchorage for plants, regulates water through filtration and storage, and contributes to climate stability by storing carbon and cycling essential nutrients — making it vital for sustaining ecosystems.
During an ESS lab, Rupal compares how water drains through sandy and clay soil. She wonders, “How do different soil types affect the movement of water and plant growth — and why is this important in ecosystems?”
Soil texture (the mix of sand, silt, and clay) affects porosity and permeability, which control water movement.
Sandy soils drain water quickly, while clay soils hold water but reduce aeration.
Organic matter improves soil structure and water retention.
These differences influence plant productivity, nutrient cycling, and ecosystem stability
While examining the school garden, Chinmay notices that some soil is very hard and dense. He asks, “How does soil compaction affect soil health?”
Reduces air spaces between soil particles
Decreases water movement
Limits root growth
Reduces nutrient availability and fertility
a forest hike, Gatra notices that soils near the river are different from those on the hill. She asks, “How does transport and deposition affect soil formation in different areas?
Soil particles are moved by water, wind, ice, or gravity. This movement creates new soil layers in different locations. It changes soil texture and composition depending on what is deposited. It affects fertility, with river deposits often being richer than hilltop soils.
During a field trip, Gatra asks, Why is understanding soil as an open system important for managing the environment? 4 points
Tracks inputs and outputs like water, nutrients, and pollutants.
Helps understand nutrient cycling and energy flow.
Guides sustainable land and agricultural management.
Explains how human activities impact soil health.
While working on his ESS project, Aarush realises that soil isn’t just for plants — it drives the cycling of carbon, nitrogen, and phosphorus around the planet. He wonders, “How does soil help in these global nutrient cycles, and why is that role so important?”
Soil acts as a major storage and transformation zone for nutrients within the carbon, nitrogen, and phosphorus cycles. Through processes like decomposition, nitrification, and carbon sequestration, soil releases and recycles nutrients essential for plant growth. This continuous cycling maintains ecosystem productivity, regulates atmospheric gases, and ensures long-term sustainability of life on Earth.
During her ESS investigation, Gatra notices how fallen leaves slowly disappear into the soil. Curious, she asks, “How does soil recycle nutrients from dead plants, and why is this process so important for ecosystems?”5 POINTS
Decomposers like bacteria, fungi, and earthworms in the soil break down dead plants and animals into simpler substances.
These materials release essential nutrients such as nitrogen, phosphorus, and carbon back into the soil.
Plants absorb these recycled nutrients, allowing new growth and food production.
This process forms part of nutrient cycles, keeping the ecosystem balanced.
Without it, nutrients would run out, and life in the ecosystem could not continue.
Gatra is studying soil colour in different areas — some soils are red, others dark brown. She asks, “What does soil colour tell us about its properties and composition?” ANY 4
.Organic matter content — darker soils have more.
.Drainage and oxidation — red or yellow soils indicate iron oxidation.
.Soil age and fertility — colour can hint at maturity and nutrient richness.
.Soil colour helps understand soil health and suitability for plants.