eChapters

3.1. Soil colloids

Clay fraction of the soil contains particles less than 0.002 mm in size.

Particles less than 0.001 mm size possess colloidal properties and are known as soil colloids.

Q. 1 Which type of gully is formed on flat land?
(A) U-shaped  (B) V-shaped
(C) L-shaped   (D) T-shaped

Soil conservation is the practice of preventing soil erosion, degradation, and loss while promoting sustainable land use and agriculture. It is crucial for maintaining the health and productivity of soils, which in turn supports agriculture, ecosystems, and human well-being. Here is a detailed explanation of soil conservation:

1. Erosion Control

Contour Farming: Plowing, planting, and harvesting crops along the contour lines of the land, which reduces water runoff and erosion.

Terracing: Creating level platforms with short, horizontal ridges, which reduce water runoff and erosion on steep slopes.

Windbreaks: Planting trees and shrubs in rows to act as wind barriers, reducing wind erosion.

Cover Crops: Planting cover crops in between main crops to protect the soil from erosion, improve soil structure, and fix nitrogen.

In soil culture, also known as in-ground culture, crops are raised on level ground as well as in raised beds. Soil culture is more often used in growing vegetables (e.g., tomatoes, lettuce, cucumbers, and peppers) rather than ornamental crops such as herbs, roses, freesia, and foliage plants as well as popular with smaller commercial and organic growers. The soil should be well drained, fertile, have a medium to light texture and be high in organic matter. The soil in a greenhouse should be worked as deeply as possible to break any existing hardpans or those that may have developed because of repeated traffic over the area. Fumigation or pasteurization of the soil is a must before each crop or at least once a year. This will help to destroy disease, nematodes and weeds. If soil is steamed, hold it at 180 degrees F (82°C) for 4 hours. Production techniques used in soil culture are similar to intensive crop production methods used in the field. Although soil is readily available at most places where a greenhouse is located most commercial growers, no longer rely on soil culture in the greenhouse as they did ealier. Some of the reasons include insect and disease pressures and costly fumigation.

14.1. Soil fertility

Ability of the soil to supply essential plant nutrients during growth period of the plants

Crop producing capacity of the soil

Soil health determines agricultural productivity, resource efficiency and long-term sustainability. Conventional laboratory and field-assessment methods provide valuable information but can be time-consuming and difficult to scale. This chapter presents a computational approach combining soil sensors, remote sensing and historical agronomic records. Indicators such as moisture, nutrients, pH and organic matter are processed using data-cleaning and feature-extraction techniques. Random Forest, Support Vector Machine and neural-network models estimate soil-quality parameters and identify degradation patterns. Explainable artificial intelligence improves the transparency and usefulness of predictions. Integration with edge computing enables real-time soil evaluation and supports targeted fertilization, efficient irrigation and sustainable soil-management decisions.

Q. 1 Hygrophilic soils are those
(A) Which attract water       (B) Which do not attract water
(C) Which transmit water    (D) Which produce water

4.1. Role of soil microorganisms

Soil N utilization by plants.

Dead organic matters decomposed.

Nutrient transformation.

Physical and chemical properties of soil.

CO₂ content.

Soil formation.

The water contents expressed under certain standard conditions are commonly referred to as soil moisture constants. They are used as reference points for practical irrigation water management. The usage of these constants together with the energy status of soil water gives useful knowledge. These constants are briefly explained below:

6.1 Saturation Capacity

Saturation capacity refers to the condition of soil at which all the macro and micro pores are filled with water and the soil is at maximum water retention capacity”. The matric suction at this condition is essentially zero as the water is in equilibrium with free water. Excess water above saturation capacity of soil is lost from root zone as gravitational water.

The soil water plays an important role in the physical, chemical and biological activities taken place in the soil which directly or indirectly affects the crop growth. The water content of the soil can be measured by different methods. These methods are gravimetric method, neutron scattering method and electrical resistance method.

Soil moisture stress in relation to crop and development of crop
Agronomic methods are supported with mechanical measures where land slope exceeds permissible limits and runoff gains erosive velocities. The following boxes explain the nature of agronomic measures which are essential in inter-bunded or terraced areas. These practices enhance the utility value of all kinds of mechanical structures.
1. Contour Tillage: All agricultural operations such as ridging, ploughing, harrowing, sowing, trenching, etc., are recommended to be done on the contour wherever possible or at least generally across the direction of the slope where holdings are very small. Even though the operation is very simple, it plays a major role in retarding the process of soil erosion through runoff. It also conserves soil, and due to increased time of concentration, more rainwater seeps through the soil profile to recharge ground water. Summer ploughing leaves the soil highly absorbent of initial rains.
2. Dead furrows: When all tillage operations are complete, it is advisable to leave a deep dead furrow at every 10 m interval. This should remain in position until the crop is harvested. Dead furrows aid in reducing the runoff velocity and they also conserve water.
3. Organic Matter: Indian soils are very poor in organic matter, especially in drought-prone areas: This can be improved by leaving the crop residue in situ (on the fields). Adding organic manures such as farmyard manure and compost every year as basal application to the soil improves the physical condition of the soil considerably.
Soil-Air, Soil-Temperature, and Soil-Moisture relationships are well balanced with the presence of organic matter. Organic matter improves the activities of soil microorganisms and also provides the much needed micro plant nutrients of all kinds, besides nitrogen, phosphorus and potash. Addition of large amounts of chemical fertilizers to dryland crops should be discouraged as it damages the soil due to:

Soil moisture is the water retained within soil pores and represents a critical link between precipitation, evapotranspiration, runoff, infiltration and groundwater recharge. It provides the principal water supply for plant growth and strongly influences crop establishment, nutrient availability and yield. This chapter discusses soil-moisture storage, field capacity, permanent wilting point, available water, infiltration, percolation and root-zone dynamics. It examines methods of measurement, estimation and monitoring and explains how soil texture, structure, organic matter, vegetation and weather influence moisture conditions. Effective soil-moisture management supports irrigation scheduling, drought mitigation, water-use efficiency and prevention of waterlogging, thereby strengthening agricultural productivity and environmental sustainability.

Soil organic matter is a key component of soil fertility, biological activity, aggregation and carbon storage. This chapter examines the origin, transformation and management of organic matter in agricultural soils, with particular attention to irrigated agroecosystems. It discusses the decomposition of organic matter under aerobic and anaerobic conditions and explains the major factors influencing decomposition rates. Microbial activity plays an important role in transforming organic materials and regulating nutrient cycling within the soil. The chapter introduces humus, humic substances and non-humic substances and explains interactions between clay and humus that influence soil properties. The relationship between soil organic matter and plant growth is also considered, highlighting its contribution to nutrient availability, soil structure and biological processes. Methods for maintaining soil organic matter and conserving soil carbon in agroecosystems are discussed along with factors controlling soil carbon levels. The chapter therefore establishes the importance of organic matter management for improving soil health, carbon conservation and the long-term sustainability of irrigated agricultural systems.

Pasteurization: The heat treatment given to soil to free it of harmful microorganisms or pathogens and pests is called pasteurization. It kills weed seeds also.

Pasteurization of greenhouse plant growing media

Greenhouse growing medium may contain harmful pests such as disease causing organisms, nematodes, insects and weed seeds. It is advisable to decontaminate it by heat treatment or by treating with volatile permissible chemicals.

This chapter presents laboratory procedures for measuring the major physical properties that regulate soil behaviour, water availability, aeration and root development. It begins with particle-density determination using a pycnometer and proceeds to bulk density, soil texture, moisture content, total pore space, porosity and water-holding capacity. Each practical exercise provides the underlying principle, required apparatus, procedural steps, calculations and relevant precautions. The hydrometer method is introduced for estimating the proportions of sand, silt and clay. Methods for evaluating moisture retention and pore relationships are also described. Collectively, these measurements help characterize soil structure, compaction, drainage, water storage and its suitability for crop production.

Soil physical properties
The physical properties of soil, particularly its mechanical behavior, significantly impact its suitability for plant growth. Factors like plant support, root penetration, drainage, aeration, moisture retention, and nutrient availability are all influenced by the soil’s physical condition. These properties also affect the soil’s chemical and biological activities.
A soil’s physical properties are determined by the quantity, size, shape, arrangement, and mineral composition of its particles, as well as its organic matter content and pore spaces.
Important Physical Properties of Soils
1. Soil Texture
2. Soil Structure
3. Surface Area
4. Soil Density
5. Soil Porosity
6. Soil Color
7. Soil Consistence
Soil Texture
Definition
Soil texture refers to the relative proportions of different-sized particles, specifically the percentage by weight of sand, silt, and clay. It’s a fundamental soil property that is difficult to alter. Soil textural determinations typically exclude particles larger than 2 mm in diameter (stones and gravels). While larger particles can affect land management and tillage, they contribute minimally to water-holding capacity (WHC) and nutrient storage/supply.

Soil structure is highly important for maintaining favourable conditions for water movement, aeration, root development and crop production. In irrigated agriculture, inappropriate management practices can cause structural degradation through compression, puddling, compaction and crust formation. This chapter examines the major processes responsible for deterioration of soil structure and their effects on soil physical properties and crop performance. Soil compaction is discussed in relation to agricultural machinery, pressure distribution, formation of compacted layers and restrictions to root growth and water movement. The chapter also explains soil crusting, its mechanisms, effects on seedling emergence and methods for evaluating crust strength. Slow-permeable soils, including Regur soils, highly permeable soils and soils with shallow water tables are considered from a management perspective. Appropriate management practices are emphasized to restore permeability, improve soil structure and maintain favourable soil-water relationships. The chapter provides an integrated understanding of structural degradation and its management for sustainable irrigated agricultur

13.1. Soil survey and soil mapping

Refers to study and mapping of soils in the fields.

Process of classifying soil types and other soil properties in a given area and geo-encoding such information.

Draws information on geomorphology, theories of soil formation, physical geography, analysis of vegetation and land use patterns.

Primary data for the soil survey are acquired by field sampling and by remote sensing.

Remote sensing principally uses aerial photography (Illuminating the object/ target with pulsed laser light and measuring the reflected pulses with sensor), but LiDAR ( Light Detection and Ranging) and other digital techniques.

Soil temperature is an important environmental parameter for plant growth and development. It has direct effects on microbial growth and development, organic matter decay, seed germination, root development, and water and nutrient absorption by roots. In general, the higher the temperature the faster these processes occur. Variation in soil temperature is much more pronounced because of varying characteristics and composition of soil.

The soil gains heat by absorption of solar radiation and longwave counter radiation from the atmosphere, downward transfer of sensible heat and horizontal transfer of heat from the surroundings. On the other hand, soil loses heat by longwave radiation to the atmosphere, upward transfer of sensible heat to air when the soil surface is hotter than air and with evaporation and horizontal transfer of heat from the column to surroundings.

Introduction

In order to cater to the nutritional needs of a rapidly growing population, it is imperative to increase food grain production on the same land while maintaining the soil’s productive capacity. This necessitates comprehensive research to establish a scientific foundation for enhancing and sustaining food production and soil productivity with minimal environmental impact (Rathore et al., 2010). Balanced nutrition extends beyond the application of nitrogen, phosphorous, and potassium in specific quantities through fertilizers. It entails ensuring that the soil contains the right proportions of available nutrients to meet the crop’s requirements for optimal yield (Rathore et al., 2010).