Soil Science 🌍

Capillarity 🌊

Definition: Capillarity is the ability of water to rise up between the narrow pores in the soil, against the force of gravity. 🌌

How it Works:

• Water moves upwards in soil where particles are close together yet not touching. ⬆️
• The tiny pore spaces lower down are filled with water, while those nearer to the surface are air-filled. 🌬️
• Water is drawn upwards by surface tension into the air spaces, sometimes reaching the soil surface. 🌿

Experiment: Comparing Capillarity of Sand and Clay 🧪

• Aim: To compare the capillarity of sand and clay. 🏖️
• Method:
  • Take two glass tubes and fill them with two different soil types. 🧫
  • Plug the tubes at the base with cotton wool to prevent the soil from falling out. 🧶
  • Place the base of each tube in a bowl of water and observe the extent to which water rises up each tube. 🥣
  • Note which type of soil shows the greatest capillarity. 📊
• Conclusion: Clay soils, with tiny pores, hold more water by capillarity and lose less water through drainage than sandy soils. 💧

Drainage 🚰

Definition: Drainage is the downward movement of water through soil due to gravity. ⬇️

Porosity

• Good crumb structure: Numerous pore spaces allow water to pass freely. 🌾
• Compact structure: Low porosity, slow drainage (e.g., clay soils). 🏔️
• Loose soils: Rapid drainage due to large particles and air spaces. 🌬️

Experiment: Determining Drainage Rates of Soil Samples 🧪

• Aim: To determine the drainage rates of different soil samples. 📈
• Method:
  • Take two different soil types and place about 50 ml of each into two filter funnels, plugged at the neck with cotton wool. 🧪
  • Place the funnels in measuring cylinders. 📏
  • Add 50 ml of water to each funnel over a period of 5 minutes. ⏳
  • Observe and note the amount of water that drains into each cylinder. 📊
• Conclusion: Sandy soils drain water more quickly and retain less water than clay soils. 💧

Types of Soil Water 🌊

• Gravitational Water: Free water that moves through soil by gravity and is unavailable to plants. 🌧️
• Capillary Water: The main source of water for plants, held in smaller air spaces by surface tension. 🌱
• Hygroscopic Water: Forms a thin film surrounding soil particles and is unavailable to plants. 💧

Factors Affecting Soil Fertility 🌱

• Soil Structure: Good structure allows air circulation and water retention. 🌬️
• Organic Matter (Humus): Improves structure and provides nutrients. 🍂
• pH: Influences nutrient uptake and microbial activity. ⚖️
• Parent Rock: Mineral composition affects fertility. 🪨
• Management: Practices like fertilization and cultivation impact nutrient levels. 🌱
• Soil Microorganisms: Break down organic matter to release nutrients. 🦠
• Water: Dissolves nutrients for plant uptake. 💧
• Air: Essential for root and microbial respiration. 🌬️
• Crops: Some crops deplete nutrients while others replenish them. 🌾
• Climate: Influences crop growth based on rainfall, seasons, and sunlight. ☀️

The Nitrogen Cycle 🔄

• Ammonification: Decomposition into ammonia and ammonium. ♻️
• Nitrification: Conversion of ammonium to nitrites, then nitrates. 🔄
• Denitrification: Conversion of nitrates back to nitrogen gas. 🌬️
• Nitrogen Fixation: Conversion of atmospheric nitrogen into usable compounds by bacteria. 🦠

The Carbon Cycle 🔄

• Photosynthesis uses carbon dioxide from the atmosphere. 🌞
• Decomposition releases carbon dioxide back into the air. 🌬️
• Combustion of fuels adds carbon to the atmosphere. 🔥

Causes and Agents of Erosion 🌊

• Wind 🌬️
• Water 💧
• Fire Burning 🔥
• Floods 🌊
• Slope of Land ⛰️
• Soil Type 🪨
• Vegetation Type 🌳
• Overgrazing 🐄

Types of Soil Erosion 🌪️

• Sheet Erosion: Large areas of soil eroded by a layer of water. 🌊
• Gully Erosion: Caused by fast-flowing water, common on slopes. ⛰️
• Wind Erosion: Soil is blown away and deposited elsewhere. 🌬️

Controlling Soil Erosion 🛡️

• Cover Crops 🌱
• Wind Breaks 🌳
• Controlled Grazing 🐄
• Grass Strips 🌾
• Contour Farming 🌄
• Strip Cropping 🌱
• Mulching 🍂
• Afforestation 🌳
• Intercropping 🌾
• Crop Rotation 🔄

Soil pH 🌡️

Measures acidity or alkalinity, affecting nutrient availability and microbial activity. ⚖️

Effects of Excessive Fertilizer Use 🚫

• Changes soil pH levels. ⚖️
• Causes eutrophication due to runoff into water bodies. 🌊
• Can lead to soil structure degradation in light soils. 🏜️

Neutralization of Soil Acids ⚖️

• Lime Application: Used to neutralize acidic soils and improve soil structure. 🍋
• Types of Lime: Ground limestone, slaked lime, and quicklime. 🪨