eChapters

Vegetables have got an important place in agriculture development, human diet and economy of the country. All the developed and developing countries realized the importance of vegetables an essential diet due to medicinal and nutritional value for human health. There is a steady upward trend in vegetable production. China is ranking first in the world and currently produces 237 million tonne of vegetables. India has made a quantum jump in vegetable production securing the second position in the world. The total production of vegetable is more than 91 million tonne in the country. Diseases and pests are the most important factors for low vegetable production. Various fungi, bacteria, viruses, phytoplasmas, nematodes and weeds are responsible for causing diseases in vegetables resulting heavy reduction in yield and quality.

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

Soil Structure Defined

Soil structure is defined as the arrangement of individual soil particles with respect to each other into a pattern. Structure describes the gross, over-all arrangement ofthe soil solids. In other words, soil structure is the ‘architecture’ of a soil.

Soils are composed of structural units, called “peds”. The peds consist of many individual particles, bound together by cementing agents like organic matter, clay and hydrous oxides of iron and aluminium. However, the strength of the bonds, the size and shape of the peds and the proportion of the soil particles involved in the peds differ considerably among soils.

Soil survey is essentially a systematic examination of morphological, a set of other variable soil characteristics, description, classification and mapping of soil in an area alongwith a report making an interpretation to predict their potentials for various uses particularly for crop production.

Activities of Soil Survey Soil survey is composed of the following activities –

1. Anticipation of soil variability - The initial activity of soil survey is obtained by classifying the surveyed data according to different land forms and existing land uses either through field traversing, or aerial photo or by satellite images of the concerned area.

2. Characterisation and classification – This is done on the basis of soil profile description supported with soil analytical data.

3. Soil mapping - This is performed by showing the distribution of types of soil or soil mapping units based on already classified soils with their landforms, and land uses or their combinations.

4. Interpretation - It is the process of making prediction about the potentials of soils for various uses like choice of farm practices – agriculture, horticulture, forestry, pastures etc. and their management practices.

In recent times, the interpretations cover a wide spectrum of soil uses, both for agricultural and non agricultural (sewage and human waste disposal, high way construction, water and gas supply, recreation, wild life, urban and industrial structures) and many specialized uses. Soil survey if correctly carried out according to scientific principles, can provide the data base for various interpretations. This is because the same soil properties determine the behaviour of a soil for a variety of different uses. For instance, the content of clay, silt and sand, the shrink and swell behaviour, the permeability of soil to water and air, content of calcium carbonate, salts, organic matter, gypsum, soil depth, depth of ground water, hard pan formation, co-efficient of linear extensibility, water holding capacity etc. are examples of such properties that are important to plant growth and these properties also strongly influence non farm uses. Some examples in support are

A hard or petrocalcic horizon or other slowly permeable layer (clay-pan) in a soil restricts the movement of air and water, thus adversely affecting the plant root growth. Such a layer limits the soils suitability for septic tanks and other onsite waste disposal. It also makes a poor sub grade for high way construction.

A soil high in soluble salts is a poor medium for plant growth; it is also corrosive to iron and steel structures, such as pipelines and fences, causing high maintenance and repair costs.

High organic matter content is generally favourable to plant growth, but it is a limitation for road construction.

The strongly gypsiferous soils (gypsum content >10%) are considered unsuitable for arable crop cultivation because of its dissolution under irrigated or even moderate rainfall and making the surfaces uneven through the developments of sink holes. Such soils are unsuitable for irrigation and drainage canal networks and also for construction of roads, bridges etc.

The shrink- swell soils of India (vertisols) because of summer monsoon rains are suitable for growing a “kharif” crop but are very dangerous for construction of roads, air strips, buildings, laying gas, water pipelines which get distorted, develop cracks and lead to sunken floors etc.

Soil survey is essentially a study and mapping of soils in their natural environment. It is the systematic examination, description, classification and mapping of soils of an area.

2.1. History of Soil Survey in India

The original investigations on Indian soils were carried out by Voelcker dates back to 1893 and by Leather to 1898.They classified the soils of the country into four major groups, namely the Indo-Gangetic alluvium, the black cotton soil or regur, red soil and laterite soil. Schokalskaya (1932) has published a soil map of India based on the Russian concept which describes 16 soil groups such as climate,vegetation, soil-forming materials, salinity, alkalinity, swamps and peats (Bhattacharyya et al. 2013). In 1935,Wadia and his co-workers collected a soil map of India with significance on geological formations and classified the soils as red, black (regur), laterite and lateritic soils of Peninsular India and also Indo-Gangetic Plains (IGP) which includes delta, desert, bhabar, terai and alkali soils. Vishwanath and Ukil (1943) published a soil map of India by placing the soils in different climatic zones for the first time. This was prepared by Imperial Agricultural Research Institute, New Delhi, and published in the year 1943. There were 17 kinds of soils identified, viz., deep black soils, black clay soils, black loamy soils, black sandy soils, red sandy soils, brown sandy soils, red and yellow soils, dark reddish brown soils, mixed soils (white and yellow), alluvium (Indus, Gangetic, Brahmaputra), coarse alluvium, soils of swamp lands, calcareous soils, usar soils, kallar soils, coastal alluvium soils and soils of Great Himalayan Ranges.

Soil survey works were started in 1954, in most of the states as a part of their agricultural development programme, and Bihar (Soil Survey and Land use Planning Scheme, Sabour) was pioneer. In 1954, the soil survey work was started under the leadership of Dr. P. P. Jha following the conventional procedures in Bihar (including Jharkhand) to delineate the soil associations based on geology, relief, physical and chemical characteristics of soils for the first time in India by the then Soil Survey Scheme at Sabour (Mishra et al. 2001; Mishra 2015, 2016). Meanwhile, the National Atlas Organization, Kolkata, prepared a soil map of India in 1957 classifying Indian soils into six major groups and 11 broad types. Murthy and Pandey (1983) applied the working principles of the USDA 7^th Approximation in classifying the Indian soils with available data on soil classes and thus used the US system for the first time at great soil group level, which was transformed into a soil map of India on 1:6.3 million scale. Mishra et al. (1994) attempted to propose “Fluvisols” as the 13th Order in USDA Soil Taxonomy for active floodplain soils frequently occurring in different parts of India and elsewhere. Mishra (2015, 2016) proposed a framework of Indian system of soil classification mainly based on land use options.

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.

AERATION, SOIL: The exchange of air in soil with air from the atmosphere. The air in a well aerated soil is similar to that in the atmosphere; the air in a poorly aerated soil is considerably higher in carbon dioxide and lower in oxygen.

Introduction

Soil resource catalogue provides an insight into the capability and the constraint

of mapped area for its optimum exploitation towards developmental planning.

For this motive soil survey series as an essential tool. Soil survey is essentially

a study and mapping of soils in their natural environments and systematic

examination, description, classification and mapping of soil of area.Soil survey

contains a group of compound operation involving

•             To study important properties of soils and associated land features.

 •            Define taxonomic units through correlation and classifications of soils.

•             To establish and draw a border of different kinds of soils on standard

topographical base map through mapping of soils.

 •            Transfer of technology from research farm to farmer ‘s field under

different soil condition and management practices.

Soil classification, or soil taxonomy as it is called, is grouping of soils in an orderly and logical manner based on soil properties (differentiating characters) for the purpose of studying and identifying them. The following are the purpose of soil classification:

To organize our knowledge of soils

To bring out and understand the relationships among the soils

To remember the properties of soils

To learn new relationships and principles in different soil groups

Temperature is a fundamental property of usually used to characterize the thermal condition of a system. The growth of any biological system is optimal within certain ranges of temperature and inhibited or ceased beyond this boundary. In addition to plant growth, the significance of temperature on agriculture can be ascertained by its role on physical, chemical and biological processes occurring in soil. Therefore, to study these soil properties intensively measurement of soil temperature is essential.

10.1 Measurement of Soil Temperature

Temperature of any system cannot be directly measured. It can only be estimated by its influence on some properties (thermometric properties) which respond to the variation in the intensity of heat of that system. These thermometric properties include volume, pressure, length, electrical resistance, thermal emf of the matter. Instruments built to take the advantage of any of these thermometric properties of the matter are called thermometer.

15.1. Soil Temperature

Soil temperature affects plant growth directly; influences soil moisture, aeration, structure, microbial activity, decomposition of plant residues and availability of plant nutrients. Intermediate temperatures, near optimum for each crop, are the desirable temperatures for crop growth. Extreme temperatures are undesirable, lest crop growth would be retarded and weeds and germs may be favoured. Moderate daily variations are desirable as they lead to soil moisture distribution and aeration.

15.1.1. Factors Affecting Soil Temperature

The mean annual soil temperature is about 1°C higher than the mean annual air temperature. Soil temperature is influenced mainly by climatic conditions. The factors which affect the transfer of heat through atmosphere from the Sun also affect the soil temperature. The following are the factors that affect soil temperature:

Temperature is the measure of the thermal state of a body with respect to its ability to transfer heat. Soil derives its heat almost entirely directly from the sun and losses much of it back into the atmosphere. The major processes for heat transfer in soil are: Radiation, Convection, Conduction and Latent heat exchanges between soil and atmosphere. The most important source of which is the incident radiation supplying almost all the heat energy for the biosphere and also determines the thermal regime of soil. Soil temperature or thermal regimes of soil is an extremely important property of soil as it regulates plant growth directly and influences moisture and aeration status in soil, soil structures, microbial activities and decomposition of plant residues and the availability of plant nutrients . It is controlled mainly by its thermal properties and radiation exchange over the surface and their variations within the soil. The quantity of incident solar radiation and heating the soil depends on the several factors such as exposure and latitude, albedo, soil colour, slope vegetation and composition of soil.

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.

The population of India is estimated to touch 1.4 billion by the year, 2025, which will need at least 300 million tonnes of food grain. This necessitates the production of additional food grain from the same land without loosing the production potential of the soil. This, in turn, requires extensive research to provide a scientific basis for enhancing and sustaining food production as well as soil productivity with minimum environmental degradation. In order to attain this it is essential that the amount of nutrients removed from the soil should be replenished through judicious use of fertilizers and manures. This needs a more comprehensive approach for fertilizer use, incorporating components like soil test, field research and economic evaluation ofthe results. Soil testing is one of the best scientific means for quick and reliable determination of soil fertility status. Soil test crop response study in the field provides soil test calibration between the level of soil nutrients as determined in the laboratory and the crop response to fertilizers as observed in the field for predicting the fertilizer requirements of the crop.

Objectives of soil testing.

Soil testing provides a sound information about the suitability, fertility and productivity of the soil. This enables the farmers to make the most profitable use of some of the costly inputs in farming. However, lack of information among the farmers about soil testing and their importance in management of resources necessitates that the work of soil testing should be taken extensively. Soil testing is a useful tool for making fertilizer recommendations for various crops and cropping sequences as well as reclamation of problem soils. Thus the major objective of soil testing are to identify the type of soil related problems like salinity, alkalinity, and acidity and to suggest appropriate reclamation/amelioration measures and to evaluate the fertility status in terms of available nutrients for making soil test based fertilizer recommendations.

Maximum potato yield occurs when sufficient P is available during early vegetative development and the entire period of tuber growth. Total plant P uptake increases rapidly during tuber initiation, levels off to a constant rate during tuber bulking, and ceases with plant maturation occurs primarily through the transfer of P reserves from the vine and roots. Phosphorus uptake by potatoes is relatively low compared with uptake of potassium or nitrogen but similar to uptake of sulfur. The amount of P in the soil solution that is readily available for plant uptake is very small compared with the total amount of P in the soil.

A general blanket application of fertilizer leads to its poor efficacy and wastage of costly resources as well as of environmental pollution. This becomes more relevant in case of P as unlike nitrogen applied P remains in soil and adds to its build up. In addition, this has resulted in severe imbalance of nutrients in soil (Kumar et al., 2009).

Keeping this in view, a multilocation experiment was conducted in the major potato growing states of India under the All India Coordinated Research Project on Potato to evaluate suitable dose of P based on soil test on P economy in potato (table 52). Exact quantification of phosphorus fertilizer based on soil test is very important.

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).

Scientific agriculture is the only solution for increasing productivity of various crops and the input resources most effectively. Fertilizer, the most efficient and often the most expensive input can be applied to crops on the basis of generalized state level fertilizer recommendations. However, state level fertilizer recommendations do not take into consideration fertility status of the field which is neither uniform nor constant and which varies from field to field. Sometimes more fertilizers are added leading to unnecessarily higher investment, while under another situation, inadequate quantities of fertilizers may be added, resulting in lower returns. Inefficient and imbalanced uses of fertilizers affect both soil health and agricultural productivity.

Therefore, the best and most effective method for fertilizer recommendation is soil testing. It is a mode of assessing the nutrient supplying capacity of a soil.

Sustainable agriculture warrants a wise management of natural resources and inputs to satisfy human needs in the fast changing scenario while maintaining, if not improving, the quality of environment. Soil as a natural resource is facing more and more serious degradation threats under modern agriculture. Incidence and expansion of multi-nutrient deficiencies in Indian soils owing to inadequate and unbalanced nutrient input through fertilizers is considered one of the major reasons for decline in factor productivity of crops. The problem of soil fertility depletion is spectacular across the soil types and agro-climatic zones, but it is more acute in intensively cropped areas, where annual nutrient removal by the crops often far exceeds replenishments. Recent diagnostic surveys indicate that in several high productivity areas of irrigated ecosystems like, Trans-and Upper Gangetic Plain zones, farmers are resorting to even excessive use of fertilizers, especially N, to maintain the yields at levels attained previously with lower fertilizer application rates. With an unabated deterioration in soil health in general, and soil fertility in particular, and a mounting pressure on finite land resources due to increase in population, the interest in soil fertility and soil health has revived due to several reasons:

Stagnation in growth rates of production and productivity of staple foodgrains - threat to food security

Decline in factor productivity, thus increasing cost of production

Nutrient withdrawals in excess of replenishment

Low nutritional value of food and feed grown on nutrient-starved soils - threat to nutritional security

Poor quality of produce fetching low price - threat to economic security

Introduction

It is well-known that soil testing is agronomically sound, beneficial and environmentally responsive tool for monitoring the nutrient as well as pollutant status of soils, and also for making precise fertilizer recommendations for various crops and cropping sequences. Soil testing with associated plant and water analysis is the only tool known which helps to control soil fertility. Nutrient supplying power of soils, crop responses to added nutrients and fertilizer and amendment needs can safely be assessed through sound soil testing programme. Monitoring of soil fertility, against depletion and accumulation of certain elements in toxic proportions over time, is also possible through appropriate soil tests. This also helps to economize on cost of fertilizers and also in increasing fertilizer use efficiency.