eChapters

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:

Soil is the outer loose layer of earth consisting of layers of mineral material (regolith) whose properties differ from one another and these differences are largely due to the variation in biological activities. Soil micro-environment principally comprizes of inorganic particulates (sand, silt and clay) plus certain oxides and hydroxides, plant roots, organic matter, microbial biomass and aqueous and gaseous phases. The uneven distribution of these components provides a great variety of conditions from field to micropores. The interaction of physical and chemical factors contributes to the creation of varied soil habitat and hence determines the composition and activity of soil biota at a particular site and time. Over geological times, microorganisms have had great opportunity to become distributed worldwide. Such growth and development of microorganisms as well as species diversity is of considerable significance. The existing geographic distribution is reflective of long term adaptation of microorganisms to the various environmental conditions. The preferred environment of an organism is usually referred as ‘habitat’.

Microbial Based Formulations examines preparations produced through beneficial microorganisms, fermentation, and indigenous microbial resources. It covers Waste Decomposer, Effective Microorganisms, Fermented Plant Extract, EM-Bokashi, Indigenous Microorganisms, Fermented Plant Juice, Fermented Fruit Juice, Oriental Herbal Nutrient, and lactic acid bacteria. Water-soluble potassium, phosphoric acid, and calcium preparations, brown rice vinegar, loess powder, fermented seawater, and microorganism-enriched mixtures are also discussed. The chapter demonstrates how microbial activity and fermentation can transform locally available materials into agricultural inputs. Together, these formulations illustrate approaches for nutrient management, plant growth support, compost enrichment, and ecological farming using biologically mediated processes and farm-level resources. for preparation.

Soil microbial biomass is an important parameter linking the plants to soil. It comprises about 2-3% of the total organic carbon in the soil and recognized as an important source of nutrients to plants. It is also a dynamic component of the soil associated with several functional properties of the terrestrial ecosystem. It represents the fraction of the soil responsible for the energy and nutrient cycling and the regulation of organic matter transformation.

Microbial biomass is a small but labile and living component of soil organic matter that is involved in most bio-geo-chemical processes in the terrestrial ecosystem. It interacts with crop productivity by regulating nutrient availability as a source; determining soil carbon storage- sink; and contributing to the atmospheric CO₂ from respiration. Thus it is the main agent that controls the flow of carbon and cycling of nutrient elements.

There is a close relationship between soil microbial biomass, decomposition rate, and nitrogen mineralization. It is also positively correlated with grain yield in organic farming and also contributes to soil structure and stabilization. Thus, there is the immense importance of microbial biomass in soil fertility as well as in agriculture.

The study of soil microorganisms involves various complicacies when compared with those of plants or animals aboveground. The complicated heterogeneous environment existing in soil and the varied growth behaviour of microbial populations in soil have necessitated the development of special techniques to study the microbes and their metabolic diversity, individually and holistically without disturbing their natural habitat. With the gradual improvement in microscopy since its discovery in 1667 and also with the greater understanding of the nature of soil microbes and their properties in relation to total ecosystem function, the concept of studying microbes in isolation has enormously changed. Microscopes have helped in magnifying these, otherwise invisible, minute creatures within the limits of naked eyes.

Soil microorganisms immobilize and mineralize various elements to satisfy their growth requirements. The subsequent turnover of microbial biomass also releases several mineral elements. The elements may be released as a result of organic matter decomposition (e.g. during the process of mineralization, ammonification, etc.) or through biological weathering. Other transformations may involve oxidation and reduction of various inorganic ions and compounds which are mostly catalyzed by chemoautotrophic bacteria during oxidation of ammonium, nitrite, sulphur, iron, etc. Such oxidations may also release energy for microbial growth.

Micronutrients are those elements essential for green plants but required in very small quantity for their growth and development. There are altogether eight micronutrient elements in soil consisting of iron, manganese, zinc, copper, boron, molybdenum and chlorine with the recent addition of nickel. These together with large number of other elements usually present in plants with small concentrations are formed as trace elements. Another element, cobalt is known to be required for microorganisms concerned mainly with nitrogen fixation in legumes affects indirectly the growth of many higher plants, thus, may be considered to be included in the list of essential micronutrient element. Similarly, Vanadium and sodium although present as beneficiary elements for plant growth may also have the possibilities to be enlisted into this group of elements.

ZINC (Zn)

Chandler et al., (1932) deduced the requirement of zinc by plants while working solution for little leaf or “rosette” on peach. Zinc plays significant role in assimilation of NO₃ and for synthesis of tryptophan. Involved in biosynthesis of indole acetic acid which is responsible for f lowering and fruiting, it is an activator of several enzymes (triphosphate dehydrogenase and tryptophan synthetase), involved in photosynthesis and nitrogen metabolism.

Deficiency results in poor growth of the terminal bud. Decrease in stem length resulting in resetting and whorling of leaves. Zinc deficiency disorder in rice is called khaira. Common when zinc availability is < 0.7 ppm. White bud in maize and malformation of fruits, reduction in water uptake. Interveinal chlorosis often with necrosis and pigmentation and reduced leaf size in broad leaved crops known as little leaf and malformation of leaves.

The crops which are known to respond for zinc application are maize, rice, soyabean, castor, onion, barley, wheat, potato, sorghum and cotton

Iron (Fe), zinc (Zn), copper (Cu), manganese (Mn), nickel (Ni), boron (B), molybdenum (Mo) and chloride (Cl) elements are known as micronutrients. The micronutrients are also called as trace elements or minor elements as they are required very small quantities by plants. The elements Fe, Zn, Cu, Mn and Ni are known as micronutrient cations and B, Mo and Cl are known as micronutrient anions and they behave accordingly in soils. Among these elements, Fe content in soil as well as plant is the highest and sometimes higher than phosphorus (P) and sulphur (S). In plant, the concentration of micronutrients often found up to 100 mg kg^-1, except that of Fe and Mn which may go up to 500 mg kg^-1 (dry weight basis). Another element, cobalt (Co) is also regarded to be essential for the growth of certain higher plants and animals, and likely to be included in the list of micronutrients. The importance of micronutrients has been realized during the past four decades when micronutrient deficiencies were observed in most of the soils in our country, where intensive agriculture is practiced.

18.1. Determination of Available Micronutrient Cations (Zn, Cu, Fe and Mn) in Soil

The available micronutrient cations (Zn, Cu, Fe and Mn) can be estimated in a single extraction with diethylene triamine pentaacetic acid (DTPA) as proposed by Lindsay and Norvell (1978). DTPA has the excellent property to combine with free metal ions in the solution forming soluble complexes. The stability constants of metal-DTPA complexes make DTPA as a most suitable extractant for simultaneous complex formation with Zn, Cu, Fe and Mn. In calcareous soil DTPA extractant may result overestimation due to excess dissolution of CaCO_3, thus releases occluded micronutrient cations which are not plant available. To avoid this excessive dissolution of CaCO₃, DTPA is buffered at pH 7.3 using triethanol amine (TEA). At this pH major part (3/4^th) of TEA is present as HTEA⁺ (protonation) and exchanges for Ca and Mg ion from the soil exchange site. This increases concentration of Ca and Mg in the solution phase and suppresses dissolution of CaCO₃. The DTPA has the capacity to complex each of the micronutrient cations 10 times of its atomic weight and it ranges from 550 to 650 ppm depending on the micronutrient cation.

The amount of cation in the extract is determined on an atomic absorption spectrophotometer (AAS). The experimental condition such as shaking time, DTPA concentration, pH and temperature during shaking influence the amount of Zn, Cu, Fe and Mn extracted. Increase in shaking time and temperature markedly influence the extractability of these cations.

25.1 Determination of Available Micronutrient cations (Zn, Cu, Fe and Mn) in Soil

The available micronutrient cations (Zn, Cu, Fe and Mn) can be estimated in a single extraction with diethylene triamine pentaacetic acid (DTPA) as proposed by Lindsay and Norvell (1978). DTPA has the excellent property to combine with free metal ions in the solution forming soluble complexes. The stability constants of metal-DTPA complexes make DTPA as a most suitable extractant for simultaneous complex formation with Zn, Cu, Fe and Mn. In calcareous soil DTPAextractant may result overestimation due to excess dissolution of CaCO₃, causingrelease of occluded micronutrient cations which are not plant available. To avoid this excessive dissolution of CaCO₃, DTPA is buffered at pH 7.3 using triethanol amine (TEA). At this pH major part (3/4^th) of TEA is present as HTEA⁺ (protonation) and exchanges for Ca and Mg ion from the soil exchange site. This increases concentration of Ca and Mg in the solution phase and suppresses dissolution of CaCO₃. The DTPA has the capacity to form complex with each of the micronutrient cations 10 times of its atomic weight and it ranges from 550 to 650 ppm depending on the micronutrient cation.

The amount of cation in the extract is determined on an atomic absorption spectrophotometer (AAS). The experimental condition such as shaking time, DTPA concentration, pH and temperature during shaking influence the amount of Zn, Cu, Fe and Mn extracted. Increase in shaking time and temperature markedly influence the extractability of these cations.

There are nine essential micronutrients, namely, iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), boron (B), molybdenum (Mo), chlorine (Cl), vanadium (V) and nickel (Ni). Out of these, Fe, Mn, Zn, Cu and Ni (Dominic et al., 1978) are taken up by plants in their ionic form X²⁺, Mo as MoO^2-, chlorine as Cl^– form and boron as boric acid (H₃BO₃) or as its ionic form B (OH)₄ ^–. The absorption of vanadium by plants has received only limited attention (Lepp et al., 1983); it may be absorbed as cation V or vanadyl (VO²⁺) and anion vanadate (VO₄ ^3–). Bulk of the information is available on Fe, Mn, Zn and Cu, because of the acceptability of the single DTPA (Diethylene triamine pentaacetic acid)–CaCl₂ extraction test of Lindsay and Norvell (1978) for availability of all these four nutrients followed by their estimation on Atomic Absorption Spectrometer (AAS). Available B is estimated by hot 0.15 M CaCl₂ extraction method (Saha and Singh, 1997). Molybdenum data base is poor, because its determination is dif?cult and Mo de?ciency in crops has not been much noticed in India. Chloride is available in plenty in irrigation water and soil in India and has not received much attention in India.

1. Introduction
The amount of water present in the soil is called as soil moisture. The soil moisture availability is an important topic to study as it affects plant growth, agricultural outputs and the water resource management as well. The amount of soil moisture present in a place and in a time depends on the factors like soil type, Land use, vegetation cover of the place and evaporation taking place in that area at that time. The amount of water hold by the pores in the soil determines the soil moisture. This water holding by the soil depends on various factors like temperature, moisture levels, organic matters and the soil living organisms (Rasheed et al., 2022). Essential Climate variable (ECV) is very important to our planet which can be recognized by GCOS (Global Climate Observing System). Important sustainable development issues say drought, flood management, food security, ecological health and water resources are being impacted by the soil moisture. Soil moisture changes have also a role in evapotranspiration, rainfall, and the runoff distribution and intensities. (Zeng et al., 2023).
Soil moisture content (SMC) have a huge impact in shaping the water, carbon cycles of earth and energy balance in different scales of time and space. It is an important factor for the effective water management due to its influence on the precipitation, surface temperature and evaporation which will be affecting the processes say river runoff, vegetation health, and irrigation practices. The highcost traditional methods make to overlook for SMC in environmental modelling (Edokossi et al., 2020). The atmospheric and the land surface process are blinked by the key facto of SMC as said by Robinson et al. (2008). For gaining the knowledge on water, carbon cycles and energy as well as for studying extreme weather conditions, understanding soil moisture is very much needed. (Vereecken et al., 2014; Li et al., 2007; Seneviratne et al., 2010; Robock & Li, 2006).
Due to the soil moisture’s impact on the factors say when to plant, when to blossom and when to harvest the crop, soil moisture should be considered as the important factor as it is in improving the water resources and boost the agricultural output. Remote sensing methods like microwave remote sensing plays vital role in creating maps depicting the distribution of soil moisture spatially and temporally high resolutions. These maps help in effective crop planning, in-season drought assessment, irrigation and soil managements. The traditional methods like TDR probe, Soil moisture utilizing neutron probe and gravimetric methods are inefficient in studying the soil moisture with high spatial and temporal resolutions due to factors like Variations in terrain, soil type and land use pattern. We can overcome these and enhance our ability to map soil moisture in different scales through the recent advancements of microwave remote sensing (active and passive microwave remote sensing) which are having advantages like clear, accurate and timely measurements of soil moisture content.
Irrigation water sources are controlled through the soil moisture studies by executing the sustainable water management plans and by monitoring high yields despite the environmental changes, increasing water demands and climate changes. To predict the agricultural output, irrigation management, drought early warning, creating vegetation indices, soil moisture study with high temporal and spatial resolutions will be a key factor as it improves the crop stress reduction also which are the major driving forces of yield reduction (Doraiswamy et al., 2004). So, the soil moisture has a direct impact on the crop yield which are studied using variable rate technology say selective application of pesticides which can improve farmers financially as well as environmentally (Harris et al.,1964).

The living organisms in the terrestrial ecosystem have unique characteristics of taking up the substances from atmosphere and soil for the synthesis of their own cellular component or as a source of energy. The supply and absorption of chemical compounds required for the growth and metabolism of the organisms may be defined as nutrition and the compounds required by them are called nutrients. The process by which the nutrients are converted to cellular material is known as the metabolism. Out of 118 chemical elements so far detected in the modern periodic table, 92 elements from hydrogen to uranium are naturally occurring, a large portion (more than sixty) of such have been detected in the plant tissues. But, the elements which take part in the nutritional requirement and metabolic processes of the plant are said to be essential elements, others which do not participate in such processes are considered non-essential.

Mineral

A mineral is defined as “a natural substance, usually inorganic, having a definite chemical composition and commonly a definite molecular arrangement which is usually expressed in geometric form”.