eChapters

11.1. Definition

Jones: Variations or modifications of any aspect of social process, social patterns, social interaction or social organization.

Gillin and Gillin: Variations from the accepted modes of life; whether due to alteration in geographical conditions, in cultural equipment, composition on the population or ideologies and whether brought about by diffusion or inventions within the group.

Davis and Mac Iver: Change in the relationships.

10.1. Social value

Ideas which help an individual to discriminate whether a particular object or behaviour is good or bad, desirable or undesirable.

Norms: Times rules which govern the action

Normative behavior: People are expected to behave in accordance with the values held by the individual.

S.C. Dood defined the value as “desiderata” i.e., anything desired or chosen by someone, sometime.

Value may be considered as attitude-related attribute that are projected upon people, objects and situations.

Introduction

The hot arid zones in India are spread over nearly 31.7 million hectare area of which 41.5 per cent is arable and 19 per cent is cultural wasteland. These zones are perpetuated mainly in North –West and Southern part of the country. The major parts of the country under hot arid climatic conditions are Western Rajasthan (19.62 Million ha), North-western Gujarat (6.2 M. ha), South-western Punjab (1.45 M. ha), South-western Haryana (1.28 M. ha), Andhra Pradesh (2.16 M. ha), Karnataka (0.86 M. ha), and Maharashtra ( 0.13 M. ha). These areas/ zones are characterized by hostile agro-climate and fragile eco-system, an annual rainfall between 100 – 500 mm with a coefficient of variation (CV) varying from 40 – 70 per cent, low and erratic rainfall combined with extremes of temperature (450-500 cal/cm²/day); low relative humidity; high potential evapo-transpiration value ranging from 1600 mm in eastern part and 1800 mm in western part of the hot arid zones. Other important characteristics of the hot arid regions are hot winds with high velocity, poor soil condition, poor ground water with brackish and saline in reaction, poor vegetation, frequent occurrence of drought and frost, difficult to execute agro-techniques, difficulty in post harvest handling and marketing owning to limited and inefficient transportation and marketing facilities, etc (Yadav and Soni, 2008).

Soil pH

Danish scientist Sorensen (1909) first used the term pH. The H+ concentration is usually small and is expressed in terms of pH, defined as the logarithm of the reciprocal of the H+ concentration, in moles per litre. The pH scale ranges from 0 to 14, with 7 being neutral. Soil acidity is the concentration of H+ in the soil solution. This is active acidity. Besides, there is a potential acidity, that includes the H+ adsorbed on the colloidal fraction of soil. The pH scale is derived from the dissociation constant of water, Kw:

The soil acidity and alkalinity are major driving forces in regard to the mobility of plant nutrients from soil to plants. The extreme acidity or alkalinity cause damage to the crops and thus yield is affected. Correction of soil acidity or alkalinity depend upon the pH of the soil and its previous management options. Application of fertilizer in soil may be one of the factors affecting soil conditions. Exchangeable and soluble iron and aluminium ions and their hydroxy ion species may contribute hydrolysis to release H+ ions to the soil solution. The soluble salts of carbonate and bicarbonates also develop salinity in soils.

7.0 Soil reactions

Soil reaction is an indication of the acidity or alkalinity of soil and is measured in pH . The pH scale ranges from 0 to 14 with pH 7 as the neutral point. When the amount of active hydrogen ions in the soil solution increases the soil pH decreases and thus becoming more acidic in reaction. One of the outstanding physiological characteristics of the soil solution is its reaction. Soil reaction can influence the physico-chemical properties of soil which can regulate the growth and activity of plant and soil organisms associated with it.

Soil acidity is most conveniently measured by pH of soil suspension with water. Pure water undergoes dissociation into hydrogen and hydroxyl ions and are in equilibrium with undissiociated water molecules Thus, H2 O ??? ??? H+ + OH- (1) and in presence of another H2 O molecule, H+ converts to H3 O+ H+ + H2 O ??? ??? H3 O+ (2) Since water is a weak electrolyte and dissociates as per Eqn. 1, the ionic product of water can be written as – KW = aH+ x aOH- = (CH+ x COH– ) x ( fH+ x fOH-) (3) where, a, C, and f represents the activities, concentrations and activity coefficients of respective ions. In pure water and in dilute solutions the activity coefficients are approximately unity thus the product of concentrations of H+ and OH-1 is the ionic product of water and at ordinary temperature (250 C) this has a constant value of 10-14 gm ions per litre so, Kw =(CH+ x COH–1) = 10-14 gm ion per litre (4) such that, CH+ = COH–1 = 107 gm ion per litre Therefore, if hydrogen ion concentration of an aqueous solution exceeds this value, (10-7gm ion per litre), the solution is said to be acidic then there will be a proportionate decrease of OH- concentration to maintain the constant value of ionic product.

Aggregation is a direct indicator of soil structure. Ahealthy soil is considered to have well aggregated structure. Though not routinely followed during soil testing and chemical analysis, aggregation is one of the major indicators of soil physical health. Wet sieve method (Yoder, 1936) is usually followed for soil aggregate analysis. This involves gently raising and lowering a nest of sieves in water to assess the stability of aggregates to rapid wetting. However, the Yoder’s wet sieving method has been modified to make it simpler and currently, the method of Kemper and Rosenau, 1986 is being commonly used in research laboratories. One of the pre-requisites in these methods is the availability of wet sieving apparatus and further, these methods are laborious and time consuming. On the other hand, the method described by Cambardella and Elliott (1993) is considered very ideal because of its simplicity and is being widely used for aggregate bound soil carbon fraction study. The soil sample is wet sieved with a series of three sieves (2000, 250 and 53 micron size).

Aggregation is one of the basic physical characteristics of soil. Under natural conditions, primary soil particles, particularly clays, tend to join together to form secondary units called aggregates. Size distribution of soil aggregates is important because the size of the aggregates determines their susceptibility to water and wind erosion. Also, their size is important in determining the pore size distribution and regulating pore space in cultivated soils.

There are a variety of procedures being in use to test the stability of aggregates and aggregate size distribution. However, choice of the method for analysis of aggregate size distribution is determined by the purpose of analysis. The developed measures are relative and purpose specific. This chapter discusses dry aggregate analysis.

In natural condition primary soil particles cohere to each other to form a cluster or an aggregate through the cementing action of various agents like organic matter, oxides of iron and aluminium, carbonates, etc. Aggregate analysis tells one about the structural status, pore geometry which in turn influences the movement of air and water in soil, amount of water stable secondary particles (aggregate) as well as the extent of finer particles aggregated to the coarser particles and the erodibility status of surface soil against wind and water.

Methods of Analysis

Among the several methods of aggregate analysis the commonly used methods practiced in agriculture and related fields are wet sieving and dry sieving method of aggregate analysis.

In natural condition primary soil particles cohere to each other to form a cluster or an aggregate through the cementing action of various agents like organic matter, carbonates, oxides of iron and aluminium, etc. Aggregate analysis tells one about the structural status, pore geometry which in turn influences the movement of air and water in soil, amount of water stable secondary particles (aggregate) as well as the extent of finer particles aggregated to the coarser particles and the erodibility status of surface soil against wind and water.

9.1 Determination of Oxygen Diffusion rate (ODR) of Soil

The rate of movement of oxygen from atmosphere to respiring plant root cells is important for root respiration and thereby the growth and development of plant. While diffusion through the air-filled pores maintains the exchange of gases between the atmosphere and soil, diffusion through water films maintain the supply of oxygen and disposal of carbon dioxide from active root tissues which are typically hydrated.

Principle

Lemon and Erickson (1952) introduced a method for measuring oxygen diffusion in soil with the help of platinum electrode. The process measures the extent of chemical reduction of oxygen by the platinum electrode maintaining a constant potential of 0.65V with a reference electrode.

3.1 Important Soil Physical Properties

3.1.1 Analysis of Soil Texture

Soil texture refers to the relative proportions of sand, silt, and clay on weight basis. Soil texture was recognized from very early times by experienced farmers from the feel of moist soil placed between the thumb and forefinger. The size groups arbitrarily classified by the International Society of Soil Science (ISSS) into clay (< 0.002 mm), silt (0.002 0.02 mm), fine sand (0.02-0.2 mm), and coarse sand (0.2 2.0 mm). Each soil textural name specifies the weight percent of each fraction falls within certain defined limits. The determination of the percentage of the soil separate present in a sample is called particle-size analysis.

Each type of particle present makes its contribution to the nature of the soil as a whole. Sandy soils are usually quite permeable to air, water, and roots, but they have two important limitations. One is their relatively low water-holding capacity; the second is that they are poor storehouses for plant nutrients. These limitations of sandy soils can, of course, be overcome if both fertilizer and irrigation water are available, but the costs are large.

Clay not only have a large surface area per gram, it also has electrically charged particles. These charges give clay the capacity to attract plant nutrient ions to its surface in forms available to plants, but sand lacks this capacity. Clay holds much more water than sands because they have a large surface area to be coated with water. One important problem with clay soils is their stickiness. When wet, they stick to ploughs, boots, or whatever they contact. Loam and silt loam soils are highly desirable for most uses. They have enough clay to store adequate amount of water and plant nutrients for optimum plant growth but not so much clay as to cause poor aeration or to make working with them difficult.

Soil sampling is the first step of soil analysis. As very small fraction of the huge soil mass is used for analysis, it becomes extremely important to get a true representative soil sample of the field.

3.1 Concepts of Soil Sampling

Samplinginvolvesthe selection fromthe total populationof a subset ofindividuals upon which measurements will be made. The measurements made on this subset (or sample) will then be used to estimate the properties (or parameters) of the total population.Samplingisinherent toanyfield research programinsoilscience because the measurement of the total population is impossible for any realistic study.

Samplingdesign involves theselection of the mostefficient method forchoosing the samples thatwill be used to estimatethe properties of the population. The definition of the population to be sampled is central to the initial formulation of the research study. The sampling design defines how specificelementswill be selected from the population, and these sampled elements form the sample population.

Pedogenetic and soilgeomorphic studies focus on determining the processes thatformed the soilproperties or landscapes under study and the environments that controlled the rates of these processes. Pedonscale studies are closely associated with thedevelopmentof soil taxonomic systems andfocus onvertical, intrapedon processes. Soil geomorphic studies are the interface between quaternary geologyand soil science and soil geomorphologistsfocus on lateral transferprocesses and the historical landscape evolution. Hence sampling is difficult for a particular population and is differentfor differentstudy.

SOIL MANAGEMENT PRACTICES

Good soil management is the basic for deriving greater benefits from the fertilizers used in crop production. Some of the good soil management practices are

Good tilth is the first feature of good soil management. It means a suitable physical condition of the soil and implies in addition a satisfactory regulation of soil moisture and air.

The maintenance of soil organic matter which encourages granulation is an important consideration of good tilth.

Tillage operations and timings should be adjusted as to cause the minimum destruction of soil aggregates. Good tilth minimizes erosion hazards.

The choice and sequence of adaptable crops or crop rotation are other very important considerations. These are related to climate, particularly rainfall and its pattern of distribution and the characteristics of the soil profile, including drainage and extent and duration of available soil moisture. A proper sequence of crop varieties greatly influences soil conditions. It is more realistic to evolve cropping patterns and land management practices according to land capability. Cropping patterns chosen and management practices adopted should aim at soil and moisture conservation for efficient nutrient and moisture utilization.

As compared to total N soil total P is present in much smaller amounts in soil; it is roughly about 10% of total N. Further, while N in soil is in the largest amount in surface 0 to 15 cm layer, soil P may be the same or in larger amounts in the sub-soil. Again, organic P constitutes only a small portion of total P. Thus, the Chemistry of soil P is generally centered on inorganic P. Total and organic P in some Indian soils is given in Table 8.1; hill soils had the highest and the desert soils the least total as well as organic P.

FRACTIONS OF INORGANIC P

All P in soils has originated from apatites [3 (Ca₃ (PO₄)₂.Ca×₂, where ×₂ could be F, Cl, (OH) or CO₃). Large deposits of apatites form phosphate rocks, which are the major materials for making phosphate fertilizers. As the soil weathering proceeds, P in apatite reacts with Al, Fe and other cations and forms compounds of different solubility. A knowledge of these can help in understanding the P-supplying capacity of soils. A number of chemical extractants and resins are used for determining different fractions. In general, 7 fractions of inorganic soil P are mentioned. These are: saloid-P (soluble and loosely bound P extractable by NH₄Cl), labile P (determined by using anion-exchange resins), Al-P (NH₄F extractable), Fe-P (NaOH extractable), Ca-P (H₂SO₄ or HCl extractable), reductant-soluble- P (CDB or sodium citrate-sodium dithionite-sodium bicarbonate extractable) and occluded P (CTB followed by NaOH extractable)

Out of the three primary plant nutrients (NPK), potassium (K) is taken up by crop plants in the largest amount, yet as compared to N and P, only a tiny fraction of it goes in the grain or seed. For example, Shivay et al. (2015) reported from a study on rice that about 20 kg N, 6 kg P (13.7 kg P2O5) and 46 kg K (55.2 kg K2O) was taken up by the crop to produce each Mg or tonne (1,000 kg) of rice kernel; however, only 4.3% of K taken up by the crop was found in the rice kernel as compared to 44% of N and 66% of P taken up by the crop. Some information on N, P and K removed per tonne of grain/ seed for some crops is given in Table 9.1.

Introduction

Many of the globe’s major food crops viz., wheat, rice and vegetables have reached “yield stagnation” or “yields plateau”. This can be attributed to the land degradation and soil diminishing capacity to supply nutrients at the required rate due to over mining of essential nutrients. Further, imbalance use of fertilizers and lesser use of organic manures over the years have badly affected the soil health. To bring back life to the soil and relieve it from nutrient stress; fertilizers and manures/bio-fertilizers have to be applied in a scientific manner. At the same time, their indiscriminate use can result either in their under utilization and toxicity or leaching to the lower horizons, leading to underground water and create pollution problems. The soil is also the main source of sixteen mineral elements identifies in view of their importance for plant growth. These are N, P, K, S, Ca, Mg, Na, Fe, Mn, Zn, Cu, Mo and Cl (Tisdale et al., 1985). Nitrogen, potassium and phosphorus have been designated as major nutrient elements in order of their removal by the plant; sulphur, calcium and magnesium as secondary nutrients while zinc, copper, iron, manganese and molybdenum are called micro nutrients as these are taken by plant in traces. 
Nutrients need of vegetables depends upon the yield response to applied nutrients from fertilizers, agro-climatic conditions, variety and nutrient availability from the soil pool. The nutrient status of the soil further depends upon the quantity of total and available nutrients present in the soil pool. The soil tests helps in selecting the proper manuring schedule for various crops in a sequence by knowing about the nutrient build up or depletion in the soil profile. The adequacy of soil testing methods to correctly predict the fertilizer needs varies with the soil type, climate/soil moisture and crop species. The rainfall also influences the efficiency of soil testing methods, especially nitrogen and potassium when it becomes imperative to have tissue analysis for modify the fertilizer recommendations. Plant tests also help to identify the nutrient deficiency in standing crop and in the event of deficiency of a particular nutrient helps in taking corrective measures (Sud 
et al., 2008).

Introduction

The natural resources of arid regions particularly soil and water are limited and is often in a delicate environmental balance. Desert encroachment due to lack of conservation planning, and the dangers of destroying or depleting beyond recovery these productive resources, are evident at present time and may be disastrous if development is based on short term expediency rather than long term stability.

The arid zone of India is spread over 38.7 million ha area, out of which 31.7 m ha in under hot arid region and 7 m ha under cold region. The hot arid region occupies major part of north-western India (28.57 m ha) and occurs in small pockets (3.13 m ha) in south India. The north-western arid region occurs between 22o30' and 32o05' N latitudes and from 68o05' to 75o45' E longitudes, covering western part of Rajasthan (19.6 m ha, 69%), north-western Gujarat (6.22 m ha, 21%) and 2.75 m ha (10%) in south-western part of Haryana and Punjab (Faroda et al. 1999). Rainfall distribution is highly uneven over space and time (CV>60%). The region receives low rainfall (<100 mm to 500 mm), has high evapotranspiration and high temperature regime (Rao and Singh 1998). Groundwater is deep and often brackish. The western-central area is devoid of drainage system and surface water resources are meager (Fig. 20.1). Due to low and erratic rainfall, replenishment of water resources is also very poor. The entire Rajasthan state is being categorized as the driest state and water scarce (having per capita water availability below 1000 m3 year-1) since 1991 in the country. Increasing pollution by industrial units, big and small, unregulated mining and even over-extraction of water from deep wells also add to the water quality problem in number of districts. Rapid urbanization and industrialization make such existing differences even more