eChapters

Wet sieving procedure separates soil into different size aggregates. However, for comparing the aggregate size distribution among management treatments and soil types, it is convenient to use indices. Mean weight diameter (MWD) and water stable aggregate percentage are some of the common indices used in aggregate stability studies.

Mean Weight Diameter (MWD)

This index was proposed by Van Bavel (1949) and is being used widely. The entire soil sample is passed through an 8 mm sieve prior to analysis and is subjected to wet sieving procedure as described before. The parameter which Van Bavel (1949) called the MWD is equal to the sum of the product of (a) the mean diameter (d ) of each size fraction and (b) the proportion of the total sample weight (w ) occurring in the corresponding size fraction. The summation is carried out over all ‘n’ size fraction including the one that passes through the finest sieve.

Participation means different things to different people. They way participant is defined largely depends upon the context and back ground in which participation is applied. While the Economic Commission for Latin America (1973) considers contribution by the people to public programmes to the complete exclusion of any involvement in the decision making process as participation. Cohem and Uphoff (1977) maintain that participation tools includes the peoples involvement in the entire decision making process. Like Cohem & Uphoff, FAO (1982) emphasizes participation in all the decision making processes but by the people’s organization and through self organized action. Paul (1987) introduces the concept of enhancement of well-being in terms of values cherished by the communities as being the ultimate objective of participation.

Measurement of water used in irrigation ensures the application of required amount of water in crops. Knowing the rate of flow the adjustment to period of control at gates, etc. can be done to regulate the water at different branches of canals. To get the total control over the supply of water there should have the provision of water measurement at the critical points in irrigation systems.

Units of Measurement

Water is measured at rest or in motion. The water of reservoir, ponds, tanks, etc. at rest is measured in volumetric unit as liter, cubic meter, hectare-meter and hectare-centimeter. Water flowing in rivers, canals, channel, etc. is measured in litre/sec , liter per hour, meter per sec and hectare-meter per hour or day.

Water Quantity and Measurement: The amount of water to be applied and its measurement are crucial aspects of irrigation management. There are various methods and tools used to measure and control the flow of water, including:
1. Parshall flume
2. Orifice
3. Weirs
4. Water meter
5. Float method
6. V-Notch
Methods of Soil Moisture Measurement
The measurement of soil moisture is essential to determine when to irrigate, the amount of water needed, to evaluate evapotranspiration, and to monitor soil matric potential. Soil moisture is measured in two ways: direct and indirect methods.
Direct Methods
1. Gravimetric method: The gravimetric method is a standard method for measuring soil water content directly. It involves collecting soil samples from the field and determining their moist and dry weights. The mass water content is then calculated as the ratio of the weight loss in drying to the dry weight of the soil sample. This method is accurate but time-consuming and requires laboratory equipment.
2. Spirit burning method: The spirit burning method is a direct method for measuring soil moisture in the field. Soil moisture is evaporated by adding alcohol and igniting it. The time taken for the soil to dry is then used to calculate the soil moisture content. This method is quick and easy but can be affected by soil temperature and organic matter content.

Measurement of soil aeration

Oxygen Diffusion Rate (ODR) - the rate at which O₂ in soil air is replenished. ODR decreases with soil depth.

Measurement of ODR in soil

Lemon and Erickson (1952) devised a method for measuring oxygen diffusion in the soil system with the help of platinum micro electrode

Principle

When a certain potential is applied across the platinum electrode and a reference electrode inserted in the soil, oxygen is reduced at the platinum surface. The electric current flowing between two electrodes is proportional to the rate of oxygen reduction. The later, in turn, is related to the rate of oxygen diffusion to the electrode. The oxygen diffusion rate (ODR) is calculated from the measured electric current with the following equation.

The ratio of soil air-to-soil water permeability indicates the magnitude of breakdown of structure as a result of wetting. A value of one indicates no change in structure and a value greater than one reflects a deterioration of soil structure.

Principle

The permeability of soil to air can be obtained essentially in the same way as the permeability of soil to water. The measurement of permeability of soil to air involves the preparation and placement of the soil in a suitable container with provision for monitoring pressure differential across the sample and the rate of flow of air through it. For steady state case, this involves measurement of inlet and outlet pressures and the volume flux of air. The suitable form of the Darcy’s equation for calculating permeability of soil to air is:

Tensiometer is a device to measure soil moisture tension or equivalent negative pressure of water in the soil. A tensiometer consists of a tube sealed at one end by a porous ceramic cup which is in contact with the soil and a vacuum gauge or a manometer connected at the other end above the soil surface. When the tensiometer is filled with water, the manometer or gauge will read zero tension. When such a tensiometer is placed in an unsaturated soil, the soil in contact with the porous ceramic cup will immediately start sucking water through the porous cup wall. The water in the soil pores immediately establishes hydraulic equilibrium with the water in the cup through saturated pores of the cup wall. Water and solutes can f low through the pores of the cup wall but not the air within the working range of the tensiometer. Water could be sucked from the tensiometer by the soil until vacuum created inside the tensiometer is just sufficient to overcome the suction of the soil. At equilibrium, the tensiometer reads directly the amount of soil suction. The outf low of water from the cup is very little. The effective range of the tensiometer is 0 to 0.85 bars depending on quality of the porous cup.

The measurement of soil moisture is needed to determine when to irrigate and the amount of water needed when irrigating, to evaluate evapotranspiration, and to monitor soil matric potential. The soil moisture is measured in two ways- direct and indirect methods as follows:

Soil temperature plays an important role in plant growth. Solar radiation received on the earth surface raises the temperature of the soil surface from morning to solar noon followed by a decline until the next morning. Soil temperature gradients established on the surface lead to flow of heat downwards causing a rise in temperature of lower layers. These variations in temperature affect germination, emergence and further growth of plants. Several types of thermometers such as mercury or liquid in glass, bimetallic, bourdon gauge, thermocouples and electrical resistance have been used in soil research but the use of thermocouples and thermistors has been found most useful. A brief description of different types of thermometers used in measurement of soil temperature is given below:

Liquids in Glass Thermometer

A liquid-in-glass thermometer (Figure 20.1) consists of a capillary glass tube with a bulb at one end filled with a thermometric liquid (mercury), vacuumed and sealed. By reading the position of the liquid level on a scale the temperature value can be obtained.

Mechanism of Bioinputs explains the biological processes through which beneficial microorganisms and other bioinputs influence plants, pathogens, and agricultural ecosystems. The chapter examines direct and indirect plant-growth-promoting mechanisms of rhizobacteria, mycorrhizal fungi, endophytes, and biocontrol microbes. It also covers entomopathogenic bacteria, fungi, nematodes, viruses, and the modes of action of microbial and botanical biopesticides, predators, parasitoids, and semiochemicals. Environmental factors, microbial variability, pathogen interactions, and relationships with other organisms are considered as influences on biocontrol performance. The chapter therefore connects biological mechanisms with practical application, helping readers understand why particular bioinputs work under specific agricultural conditions. across varied farming conditions.

Bacterial biofertilizers are supplied as carrier based inoculants. Peat or lignite is used as carrier material. Carrier based bacterial inoculants are applied by the following methods.

1. Seed treatment or seed inoculation.
2. Seedling root dip and
3. Main field application

Seed Treatment

One packet of the inoculant (200 g) 7is mixed with 200 ml of rice kanji to make a slurry. The seeds required for an acre are mixed in the slurry so as to have a uniform coating of the inoculant over the seeds and then shade dried for 30 minutes. The shade dried seeds should be sown within 24 hours. One packet of the inoculant (200 g) is sufficient to treat 10 kg of seeds.

Abstract

Agroforestry is an integrated self-sustainable land use management system that is not only capable of producing food from marginal agricultural land but also capable of maintaining and improving the quality of environment. It plays a vital role in achieving integrated rural and urban development. But reliable data on number of trees and area under agroforestry is not available as methodology for estimation of even area under agroforestry is not yet standardized. In this paper, a methodology for estimation of number of trees under agroforestry using high resolution satellite data has been proposed and estimation of number of trees as well as area under agroforestry in Ludhiana district of Punjab State has been done using the proposed methodology. Land use/land cover map of the district has also been generated using ERDAS IMAGINE software. It has been observed from the accuracy assessment that the estimates of number of trees as well as area under agroforestry obtained using the proposed methodology under this study are very reliable. Therefore, the proposed methodology may be replicated for estimating number of trees as well as area under agroforestry in other parts of the country.

Keywords: Agroforestry; Estimation of number of trees, Area estimation; Remote Sensing; GIS

Introduction

The main objective in analysing fertilizers is to assess their quality. The analysis examines both their physical and chemical composition. The quality of fertilizers is stated by the manufacturers and, in most countries, it is statutorily notified. Hence, analysis is carried out to determine whether the stated quality meets the statutorily notified standards or not. Together with the statutory notified composition of the fertilizers, the testing methods are specified. In situations where the testing methods are not notified, the prevalent standard methods are followed. Generally, the term fertilizer refers to mineral fertilizers, which are manufactured chemical products of standard composition, while the term manures refers to organic manures, compost, agro-industrial wastes, etc. The compositions of organic fertilizers, unlike mineral fertilizers, are quite variable and, thus, difficult to regulate precisely.

Fertilizer quality is notified in terms of physical and chemical characteristics. The physical parameters include moisture content and particle size. The chemical parameters refer to the amount and form of nutrients, and to various impurities that may be toxic to plants above a critical limit, e.g. biuret in urea. The efficiency of a fertilizer depends on its form of nutrient content. A phosphatic fertilizer may have water-soluble, citrate-soluble, water-insoluble or citrate-insoluble forms of phosphate. A nitrogenous fertilizer may contain ammoniacal, nitrate and amide forms of N in various proportions.

Introduction and Scope

Plant and soil testing enable scientific assessment of the needs of the plant for nutrient elements and of the capacity of the soil to supply them. The nutrient elements enter the plant in ionic form from the soil solution. Ion transport to the root surface may take place through ion diffusion and bulk transport (mass flow). Mass flow is the sweeping along of ions as water moves to the root. It is particularly important for ions that are not absorbed on soil colloids such as nitrates and sulphates. Because of mass flow, a plant deficient in N can extract all the nitrates from the soil. Potassium, phosphate and the micronutrient cations are absorbed on soil colloids with various degrees of affinity and are greatly retarded in movement with the soil water. Diffusion (movement along a concentration gradient) is the main mode of transport from the solid phase to the root surface for these non-mobile ions. There is also a possibility that some of them are absorbed by a direct exchange of an ion, usually hydrogen, between the root surface and ions absorbed on soil colloids. Most ions are sorbed by the root against a concentration gradient and, thus, the process involves the use of metabolic energy. The fact that nutrient uptake is an active process explains some of its peculiarities. Plants not only accumulate nutrients against a concentration gradient, they are also able to select from the nutrients at the root surface according to their requirements (preferential uptake).

Introduction

Soil is the main source of nutrients for the plants. Soil also provides support for plant growth in various ways. Knowledge about soil health and its maintenance is critical to sustaining crop productivity. The health of soils can be assessed by the quality and stand of the crops grown on them. However, this is a general assessment made by the farmers. A scientific assessment is possible through detailed physical, chemical and biological analysis of the soils. Essential plant nutrients such as N, P, K, Ca, Mg and S are called macronutrients, while Fe, Zn, Cu, Mo, Mn, B and Cl are called micronutrients. It is necessary to assess the capacity of a soil to supply nutrients in order to supply the remaining amounts of needed plant nutrients (total crop requirement - soil supply). Thus, soil testing laboratories are considered nerve centres for nutrient management in crop production systems and plantation forestry.

Soils may have large amounts of nutrient reserves in them. All or a part of these reserves may not be of any use to crops because they may not be in plant-available form. For the purpose of estimation or analysis of plant-available soil nutrients, such methods are to be used that have been tested/verified for the correlation of nutrients extracted and their plant availability. This book describes internationally accepted and widely used methods. Apart from nutrients, soil pH estimation is also critical in the assessment of soil health. Generally, plants prefer soils that are close to either side of neutrality. However, there are acid- loving plants and also plants that can withstand high soil alkalinity. Hence, good yields and economic returns from farming are possible in acid and alkali soils. With proper amendments, still higher yields can be obtained in acid and alkali soils. Soil pH also has a considerable influence on the activity of soil micro-flora and on the availability of soil nutrients to crops. It is also important to estimate physical properties such as soil texture, structure, bulk density, soil colour, water content and soil temperature.

Introduction

Irrigation water always contains some soluble salts irrespective of its source. The suitability of waters for a specific purpose depends on the types and amounts of dissolved salts. Some of the dissolved salts or other constituents may be useful for crops. However, the quality or suitability of waters for irrigation purposes is assessed in terms of the presence of undesirable constituents, and only in limited situations is irrigation water assessed as a source of plant nutrients. Some of the dissolved ions, such as NO₃, are useful for crops.

Sometimes, effluents and domestic sewage water is utilized for irrigating field crops. For using these water safely in the farming system, assessment of undesirable pollutants and organic and microbial constituents with regard to their suitability is fore-most important. Determination of organic constituents is generally carried out under two categories viz., (i) organic substances that quantify an aggregate amount of organic C and (ii) individual or specific organic substances, such as benzene, DDT, methane, phenol and endosulphan. Important determinations are the chemical oxygen demand (COD), which gives the total organic substances, and the biochemical oxygen demand (BOD), which gives the amount of total biodegradable organic substances in the water sample.

In order to get maximum benefit from manures and fertilizers, they should not only be applied in proper time and in right manner but any other aspects should also be given careful consideration. Different soils react differently with fertilizer application. Similarly, the N, P, K requirements of different crops are different and even for a single a crop the nutrient requirements are not the same at different stages of growth. The aspects that require consideration in fertilizer application are listed below:

Methods of fertilizer application

Two major methods are used to apply fertilizers  
I) Application of fertilizers in solid form 
II) Application of fertilizers in liquid forms

Irrigation Methods

Surface

Sub-surface

Pressurized irrigation

12.1 Surface Irrigation

Surface irrigation method refers to the manner or plan of water application by gravity flow to the cultivated land wetting either the entire field (uncontrolled flooding) or part of the field (furrows, basins, border strips). Most irrigated areas have characteristic land features and differ from those in other areas. Hence, for efficient application of water it is important to select such method of irrigation, which fits one’s own land.

The adoption of a certain method need not be necessarily based on convention or that followed in the adjoining farm. The factors, which determine the suitable method of irrigation are local conditions (soil type - its permeability & water storage capacity; land topography, climate, water availability & water quality), crop type, type of technology, previous experience with irrigation, required labour inputs etc. Good yield of crops can be obtained from irrigated land only if the water is applied judiciously to meet the needs of the plant, but not to cause waste and damage. Irrigation water is applied to cultivated land by the following surface methods of irrigation:

1.1 Introduction
Irrigation is the artificial application of water needed to the crop field. It is the process of uniformly wetting the root zone depth. The wetting may be done over the land surface or below of it. The application of water in excess to the requirement or accumulation of water in crop field due to rain or unplanned seepage is not considered as irrigation. However, irrigation is supplemental to rainfall. Irrigation water is considered as single most important input for crop production.