eChapters

Determination of pH is actually measurement of hydrogen ions activity in soil-water system. It is defined as negative logarithm of the hydrogen ion activity. Mathematically, it is expressed

as:pH = - log a H⁺

The pH value of a soil is an indication of soil reaction i.e. acidic, neutral or alkaline. The nutrient availability is governed by soil reaction. It is maximum at neutral pH and decreases with increase in acidity or alkalinity. Thus, pH value gives an idea about the availability of nutrients to plants.

Principle

The pH is a measure of hydrogen or hydroxyl ion activity of the soil-water system. It indicates whether the soil is acidic, neutral or alkaline in reaction. Since crop growth suffers much under both very low (strongly acidic) as well as very high pH (alkaline) conditions.

Now a days, most of the pH meters have single combined electrode. Before measuring the pH of the soil, the instrument has to be calibrated with standard buffer solution of known pH. Since, the pH is also affected by the temperature, hence, the pH meter should be adjusted to the temperature of the solution by temperature correction knob.

Soil pores differ greatly in size, shape, tortuosity, and continuity. They are characterized generally in terms of total porosity, air-filled porosity, and pore-size distribution. The characterization of pore space is important in understanding the storage and movement of water and gases, the development of plant root systems, the flow and retention of heat, and soil strength. The observation that bulk density is considerably lower than the average particle density indicates that only part of the bulk volume is occupied by soil solids and the remainder is occupied by a lighter material, such as air and water.

Total Porosity

Total porosity (n) is the percentage of the bulk volume not occupied by solids and can be computed using following relationship:

Soil pH is the measure of hydronium ion (H₃O⁺) or more commonly hydrogen ion (H⁺) activity in the soil suspension. Soil pH can be measured in soil-water suspension, saturation extract or in 0.01 M CaCl₂ solution. Saturation extract is used to identify specific soil problems such as salinity or sodicity. Measurement of pH using 0.01 M CaCl₂ solution gives more reproducible results than measured through soil-water suspension. It also provides a good approximation of field conditions as the electrolytic composition of 0.01 M CaCl₂ is considered similar to that of soil solution. However, among the three methods, soil-water suspension is most commonly used in research laboratories as well as for fertilizer recommendation as it is simpler and more convenient.

(International/Robinson’s Pipette Method)

Principle

This method is based on Stoke’s law. According to this law, the rate of fall of a particle in liquid is directly proportional to the square of its radius.

The method is based on the Stokes law which states that the rate of fall of particles in suspension is directly proportional to their size. Accordingly, larger particle (sand) will settle first, followed by silt and clay. The resistance offered by the liquid to the fall of the particles varies with the radius of the sphere.

Principle

This method is based on the principle of dispersion and sedimentation techniques, employed to a given weight of soil sample. Mechanical stirring disperses macro aggregates while chemical dispersing required for micro aggregates. The mixture of dispersed soil particles in water is called a soil suspension. Sedimentation refers to the settling rates of the dispersed particles in water, which is a function of particle size and is governed by Stoke’s law.

As water enters the soil, air is displaced and the soil pores in the upper part of the profile become saturated. A continuous supply of water leads to an increasing depth of saturation. If the supply of water at the soil surface is cut off then the rapid downward movement of water may essentially ceased within 48 hours. The soil is then said to be at its field capacity. At this stage macropores are drained off but micropores are still filled with water for use by plants. Since it is difficult to draw a boundary line between macro-and micropores and there is no sudden change in the profile drainage rate for many soils, it is not easy to specify a depth and time after which soil water movement is negligible. Therefore, measurements are necessary in each soil to specify the time and depth of sampling after wetting. Special care would be necessary in soils with impeded drainage and sand lenses, which produce perched water tables.

Proportion of solid, liquid (water), and gas (air) components in a soil mass indicates physical conditions such as soil structure, porosity and water content. A well Structured soil may have a high pore volume whereas a compacted soil may have little pore-space for other phases to occupy. In general, soil solids may occupy 50 % of the soil volume in a well-aggregated fertile loam and the remaining volume may be occupied by liquid and gases interchangeably.

Purpose

The determination of water holding capacity in soils is important as it gives an idea of the capacity of soil to hold water for the use by crops. The light soils which do not hold such water require more frequent irrigations than heavy clay soils; well decomposed organic matter increases the water holding capacity. Exchangeable sodium and type of clay mineral also have a marked effect on water holding capacity. Water holding capacity of soils is useful for selection of soils for irrigability classification. It also helps for comparing other properties of soils.

Water holding capacity of soil is the amount of water that a given soil can hold against the force of gravity. Soil texture and organic matter are the key components that determine the water holding capacity of a soil. Soils with smaller particle sizes (silt and clay) have larger surface area and can hold more water as compared to sand which has large particle sizes and smaller surface area. It is an important hydro-physical characteristic of a soil because it provides simple means of determining useful moisture levels to maintain soil for good plant growth. Detail procedure for determination of water holding capacity of soil using Keen box method (Piper, 1966) is described here.

Over most of the wetness range in which plant roots normally function, all the water in soil is controlled by matric forces. A relationship between water content and matric or soil water suction is referred to as water characteristics of the soil. Increase in matric suction is associated with decrease in water content in the soil and the process is known as desorption. On the other hand with decrease in suction soil moisture content increases and this process is known as sorption. The curves showing relationship during progressive intake and withdrawal of water are known as sorption and desorption curves respectively.

Tensiometer is suitable for finding out soil water characteristic at tension values below 2.0 kPa, whereas gas phase pressure is required for higher tensions. A pressure chamber containing a porous membrane or a ceramic plate with all its accessories to provide regulated compressed air is most convenient. A detailed methodology to determine water characteristic curve by pressure plate apparatus is described below.

Soil aggregates refers to a group of two or more primary particles which cohere to each other more strongly than surrounding particles. Under field condition, all such units also cohere to some degree with neighboring aggregates and form larger aggregates. Such aggregates form and break easily into smaller aggregates during tillage and by disruptive action of water and air. The aggregates maintaining their identity are those in which the cohesive forces among particles are greater than the disruptive forces. A quantitative characterization of aggregates is done by determining aggregate stability and size distribution of aggregates. The aggregate stability refers to the resistance of soil aggregates to breakdown by water, air and mechanical manipulations.

The soil aggregates which can stand the disruptive forces of wetting by water are known as water stable aggregates. Therefore, the process of wetting, disruption of dry aggregates and screening of aggregates of different sizes should reasonably compare to the disruptive action of water and mechanical forces of tillage under wet conditions. The vacuum wetting of dry soil largely simulates the process of soil wetting in the surface layers but the immersion wetting is more comparable to the wetting of surface soil by irrigation. Similarly, sieving under water compares more closely with the disruptive action of water and other mechanical forces. The mean weight diameter (MWD) of water stable aggregates is a useful index to characterize the change in structure due to tillage. The mean weight diameter can be calculated using following equation.

Abstract

Brinjal being native vegetable crop of India possesses rich variability. It is one of the important crops for arid region with limited irrigation water. The large variability in genetic resources available in this crop, provide scope for development of varieties with desirable characteristics such as earliness, high fruit quality and yield, tolerance to high temperature and fruit and shoot borer (FSB).

1. Introduction

With the advent of globalization and subsequent economic liberalization, the focus of Indian agriculture is shifting from “subsistence” to “commercial” mode, where farming is viewed as a “business” rather than “life-support” system of poor farmers. Enabling farmers “decision-making” capacity is a primary driver of success in the market-oriented agriculture. This “commercial focus” has brought tremendous changes in the “nature” and “mode” of extension work. On the other hand, extension work organizations in developing countries like India, are being impacted by sharp decline in public sector funding, rapid technological innovations especially in the Information and Communication Technologies (ICTs), and the shift to a knowledge-based workforce. These developments created new opportunities for the extension workers to perform the information dissemination, capacity building and technology application more effectively. 

Introduction

The globally growing demand for water has ushered the need for its efficient and judicial utilizations in all fields, and agriculture in particular being a single largest consumer of water. The majority of irrigation projects in India perform at a very low efficiency, which calls for application of efficient water management technologies for meeting the increasing water demands. Estimation of soil moisture or crop evapotranspiration from climatic parameters provides objective criteria for irrigation management. Methods to estimate evapotranspiration require huge climatic data, which are seldom available and not applied by common crop growers. Determining crop water requirement through soil moisture measurement at several locations is time consuming, destructive exercise, and may not give proper assessment of crop water need. The plant based indicator approach considers the plant water status for scheduling irrigation. This might be considered as the ideal criterion because the plant water is a good integrator of the soil, water and climatic parameters.

Circular economy principles provide a framework for developing materials that minimize resource consumption and waste while maintaining functional performance throughout their life cycle. This chapter examines the development of green nanocomposites through sustainable sourcing, circular material design, appropriate processing technologies, and functional enhancement. It discusses strategies for selecting renewable raw materials, designing composites for circularity, applying nanotechnology to improve performance, and evaluating environmental impacts through life-cycle assessment. Applications of sustainable green nanocomposites and challenges in implementing circular economy principles are also considered. The chapter concludes by highlighting future innovations in synthesis, design, processing, and evaluation needed to expand the contribution of green nanocomposites to global sustainability.

Introduction

India is the second largest producer of fruits crops in the world but productivity of arid fruit crops especially in western Rajasthan is miserably low.The productivity as well as the quality of fruit crops is affected to a greater extent due to various physiological disorders. The extremes of environmental variables like changing environmental conditions such as temperature, moisture, unbalanced soil nutrients, inadequate or excess of certain soil minerals, extremes of soil pH, poor drainage and deficiency of micronutrients as well as macronutrient causes many more disorders (Kumar and Kumar, 2015). At present, the climatic scenario of arid region is also changing and the problems like frost, temperature fluctuation, moisture fluctuation, high evaporation and low precipitation as well as nutrient imbalances are becoming a challenge for cultivation of many arid fruit crops. Reasons of low productivity in hot arid ecosystem of western Rajasthan are primarily physiological or stress related disorders such as styler-end browning in ber, fruit cracking in bael and pomegranate, internal necrosis in aonla and black and white nose in date palm. The world wide approximately 70% of crop yield reduction is the direct effect by abiotic factors (Acquaah 2007). In this chapter, we discussed the problems associated with ber, pomegranate, aonla, date palm & bael especially physiological disorders which will certainly help the farmers in timely overcoming of these maladies for getting satisfactory remunerative prices from arid fruit crops under hot ecosystem of western Rajasthan.

Introduction

Globally, the SOC pool of 1,550 Pg (1 Pg = 1015 g) to 1-m depth is about three times that of biotic and twice that of atmospheric pools (Post et al. 1982, Watson et al. 2000). In arid and semi-arid ecosystems, SOC contents show high degree of spatial variability due to patchiness of vegetation (Wiesmeier et al. 2009). The arid ecosystem might play a key role in mitigation of climate change effects through sequestering carbon in soils (United Nations 2011). Therefore, a suitable land use system having high C sequestration potential for arid ecosystem needs to be identified and promoted. However, the prevailing conditions of arid ecosystems normally does not support dense vegetation. Therefore, low carbon stock is expected in both above-ground vegetation and below-ground soil. Fruit trees are an integral part of arid farming system and played a significant role to improve the nutritional security and employment opportunity of farmers but also have potential role to increase carbon storage both in biomass and soil. To quickly assess the soil carbon restoration programmes, it is important to know how much soil carbon is stored in an agricultural farm through adoption of different land management practices. Therefore, reliable estimates of SOC pools are essential to establish the soil carbon sequestration programmes at different landscape scales.

Introduction

A complex spatial soil properties pattern is directly controlled by soil internal factors and anthropogenic impacts.Hartemink et al. (2001) elaborate a strong decline in mineralogy, morphology and genesis of soil research than strong increase in pedometrics applications during 1967 to 2001. Hartemink and McBratney (2008) identified this change as “soil science renaissance”. Basically, the soil science deeply rooted in agriculture, geology, and chemistry but the paradigm has been shifted from classification and inventorization to quantification of soil patterns in spatial as well as temporal patterns and their impact on the ecosystem health and hydrological cycle. The environmental keen approach explains that soil is in the center of the ecosystem and highly interacting with the biotic and abiotic factors of the ecosystem and a complex pattern and process has been co-evolved with the time.

Elevation or height data of land surface above a defined vertical datum is stored in the form of raster grids which is known as Digital Elevation Model (DEM). The DEM data can be processed to derive many useful parameters like slope, aspect, curvature, roughness, etc. This process of quantitatively describing terrain obtained from DEM data through computation of many variables is known as Digital Terrain Analysis. Digital terrain analysis has applications in the various fields like hydrology, ecology, geomorphology, etc. DEM data for digital terrain analysis are available from the satellites like ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer), Cartosat, ALOS (Advanced Land Observation Satellite), and SRTM (Shuttle Radar Topography Mission).

In this exercise, we are going to discuss the derivation of some primary and secondary terrain attributes from DEM data in R software. For performing digital terrain analysis in R, following packages are required.

Introduction

Disaster is defined as a serious disruption of the functioning of a community or a society causing widespread human, material, economic or environmental losses, which exceed the ability of the affected community or society to cope using its own resources (ISDR 2002).

Disaster in Global context - The impact of natural disasters in terms of human and economic losses has risen in recent years, society in general has become more vulnerable to natural disasters. Those usually most affected by natural and other disasters are the poor and socially disadvantaged groups in developing countries as they are least equipped to cope with them (IFRC 2001).