CHAPTER IIREVIEW OF RELATED LITERATURE

1. WHEAT

About One half of the 2, 600, 000, 000 ac. (1, 052, 000, 000 ha.) of cultivated land in the world is used in the production of cereals, which provide 80% of food calories produced. About two-fifths of the cereal acreage (202, 303, 000 ha.) is used for wheat production. There are more pounds of wheat produce than of rice, but more people use rice as their chief food. Wheat is used for human food principally as leavened bread, cakes and pastries, macaroni and spaghetti, and other semolina products. Cultivation and harvest are fairly simple procedures. The grain is easily stored and transported.

Nearly all important civilizations are considered to have been founded upon the production of cereals. Wheat was probably one of the first cereal crops grown by man. Wheat and other cereals provide a nutritious food containing the important elements needed for an adequate diet and it is a food product that can be easily stored. Wheat production requires planting and harvesting on an annual basis and consequently, in order to cultivated wheat, man had to settle in permanent locations if he was to depend on cereals as the major source of food.

The grain of a Wheat grass is a single seed or nutlike fruit called a caryopsis. A grain or kernel of wheat is covered by a thin shell, the pericarp, a several other cell layers often referred to as the bran. The bran coat is generally reddish brown in color and varies from light to dark depending on the texture of the interior of the kernel and the intensity of the pigment in the bran.

The plant of a Wheatgrass when the kernel is placed in moist soil at 65F or less, germination will occur in 3 to 4 days. The root develops into the main shoot. At the base of this shoot, there are buds that develop into other shoots or tillers that develops depends on the variety of wheat, time of sowing, rate of planting or spacing plants and other environmental factors. (Encyclopedia Britannica Vol.23, William Benton)

0. Taxonomic Classification

KINGDOMPlantae

DIVISIONSpermatophyta

CLASSAngiosperma

ORDERPoales

FAMILYPoaceae

GENUSTriticum

SPECIEST. aestivum

Its Binomial name is called Triticum aestivum.

0. Nutrients of Wheatgrass

NUTRIENTS OF WHEATGRASS

Protein25%

Fat7.980 g

Calcium321 mg

Iron24.9 mg

Magnesium112.00 mg

Phosphorus575.00 mg

Potassium3255.00 mg

Sodium18.800 mg

Zinc4.870 mg

Copper0.375 mg

Manganese2.450 mg

Selenium2.500 mg

Vitamin C214.500 mg

Thiamin0.350 mg

Riboflavin16.900 mg

Pantothenic0.750 mg

Vitamin B61.400 mg

Folate1 100.00 mcg

Vitamin B120.800 mcg

Vitamin A513.00 IV

Niacin8.300 mg

Vitamin A, RE2 520.00 mcg

Vitamin E9.100 mg

Chlorophyll543 mg

0. Wheat and Wheatgrass

Wheat and Wheatgrass are the same plant, Triticum aestivum. The term wheat is generally used for the grain, commonly used in flour. While, wheatgrass is called into the plant before the grain is produced.

0. Wheat Production

THE CIMMYT WHEAT PROGRAM is dedicated to increasing world wheat production is dedicated to increasing world wheat production. To achieve this, it operates in two interrelated fields. First, it conducts research to develop better varieties, it enhance knowledge of disease and insect control, to improve agronomic practices, and to improve wheat quality, from both an industrial and nutritional standpoint. Second, it participates directly in drawing up and executing plans for accelerated national wheat production programs in India and Pakistan, and within the past year, in Tunisia and Morocco. Indirectly, CIMMYT is involved through such other agencies as U.S. AID, FAO, etc. in similar production programs in Afghanistan, Turkey, Lebanon and Nepal. Several of these production programs have reached the pay-off stage within the past 2 years and others are fast approaching it. Several other countries are interested in obtaining CIMMYT assistance for launching production programs.

The first section of this report summarizes progress made and obstacles met during the past year in the national production programs with which CIMMYT is collaborating. The second section gives more detail on production and research programs by country.

Since the national wheat production programs in Pakistan and India are the most advanced, this report draws heavily on experience in these two programs to illustrate certain principles and results obtained. (Proceedings of the wheat review and planning workshop)

0. Some Diseases of Wheatgrass

4. Bunt

A smut disease of wheat and other cereal grasses, caused by fungi of the genusTilletiaand resulting in grains filled with foul-smelling, sooty black spores. Also calledstinking smut. (Bunt and smut diseases of wheat: concepts and methods of diseases management)

0. Karnal Bunt

0. History of Karnal Bunt

Karnal Bunt or partial bunt is the most recent described smut disease of wheat. It was first reported in 1931 in experimental wheat at the Botanical Station at Karnal, India and was for many years known only in the plains of India and Pakistan. However, since 1974 it has been noted in many locations across northern India. (Bunt and smut diseases of wheat: concepts and methods of diseases management)

Karnal Bunt differs from other smuts of wheat in that the pathogen. Tilletia indica, infects during anthesis, unlike Tilletia caries, Tilletia foetida, Tilletia controvesa, Urocystis agropyri, and it sporulates on the same generation of the host that it infects, unlike Ustillago tritici. (Bunt and smut diseases of wheat: concepts and methods of diseases management)

0. Symptoms of Karnal Bunt

Not all spikes of a plant are affected by Karnal Bunt, and usually only a few irregularly distributed kernels are bunted. Furthermore, infection of individual kernels varies from small points of infection to completely bunted kernels. Affected kernels are usually partially infected ones are rare. The embryo is largely undamaged except when infection is severe. In infected spikelet, the glumes may be flared to expose bunted kernels, which reek of an odor similar to rotten fish causes by trimethylamine. The spikes of infected plants generally are reduced in length and in number of spikelets. (Bunt and smut diseases of wheat: concepts and methods of diseases management)

0. Treatments of Karnal Bunt

Hot water and solar energy treatments have been applied to Karnal Bunt infected seeds. However, they have had limited application. These treatments inhibit teliospore germination, but not as much as fungicide treatments have been tested for effectiveness, results have not been satisfactory.

Some fungicides applied to infected kernels, which were then stored for various periods, inhibited teliospore germination, but others had little or no effect. Most of the fungicides reported to be effective inhibitors of teliospore germination have not been tested for germicidal properties. However, the fact that they inhibit teliospore germination after months of storage suggests they might be useful to control Karnal bunt or to eradicate the pathogen from infected seed lots. For example, in one test, pentachloronitro-benzene in liquid or wettable formations applies to wheat seeds inhibited teliospore germination up to two months.

Chlorothalonil, as emulsifiable concentrate and wettable powder applied to infected kernels, inhibited teliospore germination up to eight months. Triphenyltin hydroxide, methoxyethylmercury acetate, and ethylmercury chloride inhibited teliospore germination for 18 months. (Bunt and smut diseases of wheat: concepts and methods of diseases management)

4. Smut

Any of various bacidiomycete fungi that are parasitic on plants and are distinguished by the black, powdery masses of spores that appear as sooty smudges on the affected plant parts. Smuts are parasitic chiefly on cereal grasses like corn and wheat and can cause enormous damage to crops. (Bunt and smut diseases of wheat: concepts and methods of diseases management)

1. Loose Smut

0. History of Loose Smut

The first written of the cereal smuts comes from Theophrastus (384-332 BC). Smut was known to the Romans, who named it Ustillago, which comes from the latin word for burn. This term was later used in many languages as the common name for smut. Loose smut of wheat was illustrated in 1556 in Hieronymus Bocks Herbal, and an accurate symphatology is given in Fabricius text of 1774.The accurate illustrations and descriptions of symptoms contrast with early views on the possible causes of cereals loose smut. Among them were: a superabundance of sap that fermented and dried up and was thought to be favored by certain soils and weather; the wrath of the gods or acts of the devil; a curse form malevolent neighbors; ill-boding solar, lunar, or stellar positions; and spontaneous generation, perhaps through previously disarranged plant tissue. These causes were held to be valid until about 1800, when the true causes of the smut diseases of cereals began to be uncovered. By 1890, three distinct fungal species had been shown to cause the loose smut of wheat, barley, and oat, and it was soon learned that wheat is infected via the ovary.

Loose smut of wheat is caused by the heterobasidiomycetous fungus Ustillago tritici (Persoon) Rostrup. It is the only Ustillago specie that occurs on wheat. A trinomial system to designate strains that are specialized on certain host species is impractical because of the multitude of possible formae speciales and the overlapping pathogenicity of each strain on several host species or genera. (Bunt and smut diseases of wheat: concepts and methods of diseases management)

0. Symptoms of Loose Smut

Masses of dark olivaceous brown spores are seen when the spike emerges from the boot with nearly all tissue of the spikelets affected. Only the rachis is intact, but it may be slightly shorter than the rachis of a healthy tiller. The dark spore mass can be seen through the wall of the boot several days before the heading. Rain or heavy dew cause the spore to cake into black, hardened mass as does a severe drought in the late stages of spore formation. Hyperparasites, usually Fusarium spp., may cover and permeate the sori with whitish to pinkish mycelium. Yellow streaks appear on the flag leaf the leaf sheath, or the peduncle under conditions such as those in the greenhouse. The mycelium of the loose smut fungus can be found in each node, but not the internodes, and is scattered in leaves of adult plant.

The physiological response of a susceptible host to infection includes increase in respiration; in catalase, peroxidase and polyphenoloxidase activity, and in glucose and saccharose content. The fungus produces trehalose, mannitol, and erythritol in liquid culture and in the host but these compounds do not appear to be translocated. A reciprocal flow of carbohydrates between host and fungus is suggested.

In plants with sporulation, the number and dry weight of roots are reduced along with number, height, and dry weight of tillers. After heading, plants with sporulation stop growing. The lower internodes are usually longer and the upper ones shorter than in the healthy plants, but the peduncle of the spike with sporulation is much shorter. The leaf-sheaths of some infected cultivars are grayish-purple; the leaves, particularly the flag leaf, are reduced in size, often yellowed and senesce early. Under some environmental conditions, sporulation may be confined to the lower part of the spike.

Certain cultivars respond to infection by some races with hypersensitive or incompatible reactions. In this type of reaction, some seedlings die before emergence; others emerge but are stunted and have leaves that are brittle, often distorted, dark green, and with necrotic tips; such seedlings succumb easily to root rot and seedling blights. If a secondary tiller is produced. It usually appears to be normal and will bear a healthy spike. This tiller develops from the coleoptile bud, which has escaped invasion by the mycelium. These symptoms are obvious in the greenhouse, but less so in the field, where most infected seedlings die before emergence. This resistance reaction will not be seen in commercial field because no spores of the causative race are produced. (Bunt and smut diseases of wheat: concepts and methods of diseases management)

1. Flag Smut

1. History of Flag Smut

Flag smut on wheat was first reported in South Australia in 1868. However, it had probably been there earlier because farmers referred to a black rust before this date. In 1848, Flag Smut was reported on Agropyron sp. In Europe and was attributed to Uredo agropyri.

The Australian Flag Smut pathogen was identified as Urocystis occulta, previously described on rye. However, it was later designated as Urocystis tritici on the basis spore morphology.

The history of the disease shows that incidence and severity is dependent on the cultivars grown. For example, in the USA, the replacement of a commonly grown susceptible cultivar by resistant cultivars in Illinois reduced flag smut incidence to a negligible level. Further, in Australia, serious losses occurred when susceptible cultivars were widely grown at various periods, including 1915 to 1930 and 1949 to 1966. However, the disease declined when susceptible cultivars were replaced by resistant cultivars. Chemical seed treatment has also contributed to flag smut control. (Bunt and smut diseases of wheat: concepts and methods of diseases management)1. Symptoms of Flag Smut

Infected seedlings are characteristically twisted and bent. Raised white areas with a blistered or vesicular appearance may develop on coleoptiles of some susceptible cultivars.

Miller and Millikan noted that, before typical symptoms are seen, infected plants may be distinguished by a large number of thin, stunted, wilted, and yellowish green leaves. In the field, symptoms may develop any time after the third and fourth leaf. However, the disease is more apparent after spikes form and is most obvious at the end of the season on late tillers.

On older leaves, first symptoms appear as white, striations, which occasionally extend into the inflorescence. The striations change from white through shades of gray to black. Infected plants produce increased numbers of stunted, twisted, and distorted tillers and may not develop spikes. Infected plants also produce less developed roots, fewer fertile spikes and seeds per spike, lighter seeds, and poorer germination of seeds.

Cultivars vary widely in response to flag smut. Some genotypes may be severely stunted and have blackened tillers and few if any spikes, whereas others may show only the occasional sign of infection. Some plants with a degree of resistance may have symptoms only on late tillers. Subterranean sporulation has been observed on Phleum alpinum and Deschampsia caespitosa. (Bunt and smut diseases of wheat: concepts and methods of diseases management)

1. Treatment of Flag Smut

Water and anaerobic seed treatments have not been reported for flag smut.

Control of the common bunt fungi (Tilletia tritici and Tilletia laevis) was the primary impetus for cereal seed dressing, and this has influenced the chemicals used for control of flag smut. Most of the fungicides used for control of bunt are also effective against flag smut, but there are some exceptions notably hexachlorobenzene.

The seed dressings currently recommended for control of flag smut in New South Wales include the triazoles (bitertanol, terbuconazole, triademeton) and the carbozanilides (carboxin, flutriafol). Carboxin is advised for the control of seedborne inoculum only, but the other systemic fungicides are recommended for both seedborne and soilborne infection. The rates are 70-100g/110kg of seed for the powder formulations or 100-250 ml/100kg of seed for the liquid treatments. (Bunt and smut diseases of wheat: concepts and methods of diseases management)

1. SOIL

The rocks and minerals of the Earths surface were the starting materials from which soils originated. Exposure to the elements and volcanic and tectonic actions has resulted in the disintegration of these rocks and minerals to give a more or less unconsolidated residue over the Earths surface which is called the regolith. Organisms grew in and on the regolith, and their partly decomposed carbonaceous compounds were added to the mineral mixture. Insoluble residue was left in place. Soluble compounds were moved towards the surface, in extreme dry areas, and down and possibly into drainage waters, in humid areas. When these processes were allowed to operate without further geologic mixing for long periods of time, the regolithic material differentiated into an orderly sequence of layers, or horizons. These chemically and biologically differentiated top layers of the regolith are the soil. (Encyclopedia Brittanica Vol.20, William Benton)

1. Layers of Soil

0. Topsoil

The situation in respect to the surface soil is somewhat different. In the first place, it is the major zone of root development, it carries much of the nutrients available to plants, and it supplies a large share of the water used by crops. Second, as the layer which is plowed and cultivated, it is subject to m anipulation and management. By proper cultivation and the incorporations of organic residues, its physical conditions may be modified. It can be treated with chemical fertilizers and limestone and it can be drained. In short, its fertility and to a lesser degree its productivity may be raised, lowered, or satisfactorily stabilized at levels consistent with economic map production. (The Nature and properties of soil, Nyle C. Brady)

0. Subsoil

The productivity of a soil is determined in no small degree by the nature of its subsoil. That is of practical significance since the subsoil normally is subject to little field alteration except by drainage. Even when roots do not penetrate deeply into the subsoil, the permeability and chemical nature of the subsoil influence the surface soil in its role as a medium for plant growth. (The Nature and properties of soil, Nyle C. Brady)

0. Bedrock

A soil may be defined as the product of a weathering front passing through bedrock. Detritus and secondary products created by weathering accumulate during this process. Material is continually removed from the top of the soil column by erosion, while bedrock at the base of the column is continually being converted to soil. If the rate of removal and the rate of weathering are in equilibrium, a soil profile of constant thickness will persist through time. The weathering front producing the soil profile moves relatively downward through bedrock as the land surface is lowered by erosion. This means that material at the base of the profile has experienced less weathering than material at the top of the thematically from the bottom to the top of soil profile. Thus, by investigating mineralogical changes in and in situ soil column, we can evaluate the progression of reactions occurring as bedrock is altered. This can tell us much about how material is cycled through the Earth system. (The Nature and properties of soil, Nyle C. Brady)

1. Kinds of Soil

1. Clay Soil

Clay soil is a heavy soil that is hard and cracked when dry, sticky when wet that does not drain easily; it is hard to cultivate and allows little air to enter because clay particles are very small and can be stacked on each other very densely; however, it is usually very rich in minerals, and its texture improves considerably when river sand or coarse organic matter is incorporated. It looks like hard-baked, crusty and perhaps even deeply cracked when it dries out, scarce in pore spaces holding air and water and devoid of individual particles. It feels like harsh and rock hard when dry and sticky, greasy or rubbery when wet. (Our Soil, Jeff Van Haute and Lyds Quileste Van Haute)

0. Characteristics of Clay Soil

It is hard to work, very slow to absorb water or dry out and likely to form large congealed lumps if worked when wet. It needs substantial addition of organic materials to open channels for aeration and drainage. Some good choices: compost, manure, leaf mold, rice hulls, peat moss, coarse sand, sawdust and woodchips. Lime to improve its texture and free locked-up soil nutrients for the use of plants and leguminous green manure crops. (Our Soil, Jeff Van Haute and Lyds Quileste Van Haute)

1. Loam Soil

Loam is the type of soil that best suite most plants; it is rich in biomass that encourages our plants to develop an army of root hairs the mouthpieces of our plants. The nice thing for eco-farmers is that they can build up soil into good loamy soil by incorporating as much compost and other organic material as possible. As indicated, our classification into three major types is actually based on agricultural use of soil: sandy soil, because of its texture, is light and is easier to cultivate that clay soil, which is heavy hard when dry and sticky when wet. Loamy soil fits somewhere in between sand and clay and it has an ideal texture. Soil texture is important because it also determines the fertility of the soil and its capacity to retain moisture. Hence, the preference for loamy soil, because it is very fertile and it is a champion in moisture retention, while the capacity of sand soil to retain moisture is practically nil. (Our Soil, Jeff Van Haute and Lyds Quileste Van Haute)

1. Characteristics of Loam Soil

It looks like full of crumbs of various sizes and quite but falling apart readily when prodded or floury and talcum-powdery when dry and only moderate plastic when moist. Its easy to work, very productive, well-drained yet able to retain moisture as it is needed, well-aerated and retentive of nutrients. It needs regular infusions of organic matter to maintain its already excellent fertility and structure. (Our Soil, Jeff Van Haute and Lyds Quileste Van Haute)

1. Sandy Soil

Sandy soil has a loose, permeable structure that makes it easy to cultivate; it aerates very well but burns off humus very fast as a result and therefore needs constant replenishment with compost and other organic fertilizers. It does not retain moisture, warms up very fast, and thus dries out quickly. (Our Soil, Jeff Van Haute and Lyds Quileste Van Haute)2. Characteristics of Sandy Soil

It looks like loose and friable, quite porous, full of large, irregularly shaped mineral particles, more or less devoid of larger pieces or granules. It feels like particles and gritty, crumbly and wont hold its shape when squeezed. Its easy to work, fast-drying and low in nutrients because soluble plant foods are lost through leaching. It needs continual augmenting with large amounts of organic matter to hold water and nutrients within the range of plant roots, plentiful application of peat moss, compost, leaf mold or sawdust in topsoil layer and green manures to build structure. (Our Soil, Jeff Van Haute and Lyds Quileste Van Haute)

1. The Soil Profile

Examination of a vertical section of a soil in the field shows the presence of more or less distinct horizontal layers. Such a section is called a profile and the individual layers are regarded as horizons. The horizons above the parent material are collectively referred to as the solum, from the Latin legal term meaning soil, land, or parcel of land. Every well-developed, undisturbed soil has its own distinctive profile characteristics which are utilized in soil classification and survey and are of great practical importance. In judging a soil its whole profile must be considered.

SOIL HORIZONS. The upper layers or horizons of a soil profile generally contain considerable amounts of organic matter and are usually darkened appreciably because of such an accumulation. Layers thus characterize are referred to as the major zone of organic matter accumulation. When a soil is plowed or cultivated, these layers are included in the familiar surface soil, which is sometimes referred to as the furrow slice because it is the portion of the soil turned or sliced by the plow.

The underlying subsoil contains comparatively less organic matter than the upper layers. The various subsoil layers, especially in mature, humid-region soils, present two very general belts: (a) an upper zone of transition, and (b) a lower zone of accumulation of compounds, such as iron and aluminium oxides, clays, gypsum, and calcium carbonate.

The solum thus describe extends a moderate depth below the surface. A depth of 3 or 4 feet is representative for temperate region soils. Here, the noticeably modified lower subsoil gradually merges with the less weathered portion of the regolith whose upper portion is geologically on the point of becoming a part of the lower subsoil and hence of the solum.

The various layers comprising a soil profile are not always distinct and well defined. The transition from one to the other is often so gradual that the establishment of boundaries is rather difficult. Nevertheless, for any particular soil the various horizons are characteristic and greatly influence the growth of higher plants. (The Nature and properties of soil, Nyle C. Brady)

1. Subsoil and Surface Soil

The productivity of a soil is determined in no small degree by the nature of its subsoil. This is of practical significance since the subsoil normally is subject to little field alteration except by drainage. Even when roots do not penetrate deeply into the subsoil, the permeability and chemical nature of the subsoil influence the surface soil in its role as a medium for plant growth.

The situation in respect to the surface soil is somewhat different. In the first place, it is the major zone of root development, it carries much of the nutrients available to plants, and it supplies a large share of the water used by crops. Second, as the layer which is plowed and cultivated, it is subject to manipulation and management. By proper cultivation and the incorporation of organic residues, its physical condition may be modified. It can be treated with chemical fertilizers and limestone and it can be drained. In short, its fertility and to a lesser degree its productivity2 may be raised, lowered, or satisfactorily stabilized at levels consisted with economic crop production.

2 The term fertility refers to the inherit capacity of soil to supply nutrients to plants in adequate amounts and in suitable proportions. Productivity is related to the ability of a soil to yield crops. Productivity is the broader term since fertility is only one of the factors that determine the magnitude of crop yields.

This explains wide much of the soil investigation and research has been expended upon the surface layer. Plowing, cultivation, liming, and fertilization are essentially furrow-slice considerations. The term soil in practice usually denotes the surface layer, the topsoil, or, in practical terms, the furrow-slice. (The Nature and properties of soil, Nyle C. Brady)

1. Determination of Soil Class

FEEL METHOD. The common field method of determining the class name of soil is by its feel. Probably as much can be judged about the texture and hence the class name of a soil merely by rubbing it between the thumb and fingers as but any other superficial names/means. Usually, it is helpful to wet the sample in order to estimate plasticity more accurately. The way a wet soil sticks out or develops a continuous ribbon when passed between the thumb and fingers gives a good idea of the amount of clay present. The sand particles are gritty, the silt has a floury or talcum-powder feel when dry and is only moderately plastic and sticky when wet. Persistent cloddiness generally is imparted by silt and clay.

The method as outlined is used in field operations such as soil survey and land classification. Accuracy in such a determination is of great practical value and depends largely on experience. Facility in class determination is one of the first things a field man should develop.

The figure shows he relationship between the class name of a soil and its particle size distribution. In using the diagram the points corresponding to the percrentages of silt and clay present in the soil under consideration are located on the silt and clay lines, respectively. Lines are then prjected inward, parallel in the first case to the clay side of the triangle and in the second case parallel to the sand side. The name of the compartment in which the two lines intersect is the class name of the soil in question.

LABORATORY METHOD. A more accurate and fundamental method has been devised by the U.S. Department of Agriculture for the naming of soils based on a mechanical analysis. The relationship between such analyses and class names is shown diagrammatically in the given figure. The diagram reemphasizes that a soil is a mixture of different sizes of particles. It illustrates how mechanical analyses of field soils can be used to check on the accuracy of the soil surveyors class designations as determined by feel. A working knowledge of this method of naming soils is essential. (The Nature and properties of soil, Nyle C. Brady)

1. Four Major Components of Soil

The definition just cited leads logically to the question of soil composition. Mineral soils consist of four major components: mineral materials, organic matter, water, and air. These exist mostly in a fine state of subdivision and are so intimately mixed that satisfactory separation is rather difficult.

VOLUME COMPOSITION OF MINERAL SOILS. (Figure 1:4) shows the approximate volume composition of a representative silt soil/loam soil in optimum condition for plant growth. Note that it contains about 50 percent pore space (air and water). The solid space is made up of about 45 percent mineral matter and 5 percent organic matter. At optimum moisture for plant growth, the 50 percent of pore space possessed by this representative soil is divided roughly in half 25 percent water space and 25 percent air. The proportion of air and water is subject to great fluctuations under natural conditions, depending on the weather and other factors.

In presenting such an arbitrary volume representation of a surface mineral soil, it must be emphasized that the four major components of the normal soil exist mainly in an intimately mixed condition. This encourages both simple and complex reactions within and between the groups and permits an ideal environment for the growth of plants.

The volume composition of subsoil is somewhat different from that just described. Compared to topsoil they are lower in organic matter content, are somewhat more compact, and contain a higher percentage of small pores. This means they have higher percentage of minerals and water and a considerably lower content of organic matter and air. (The Nature and properties of soil, Nyle C. Brady)

1. Mineral ( Inorganic Constituent in Soils )

A casual examination of a sample of soil illustrates that the inorganic portion is variable in size and composition. It is normally composed of small rock fragments and minerals of various kinds. The rock fragments are remnants of massive rocks from which the regolith and in turn the soil have been formed by weathering. They are usually quite coarse. The minerals, on the other hand, are extremely variable in size. Same are as large as the smaller rock fragments, others, such as colloidal clay particles, are so small that they cannot be seen without the aid of an electron microscope.

Quartz and some other primary minerals have persisted with little change in composition from the original country rock. Other minerals such as the silicate clays and Iron oxides have been formed by the weathering of less resistant minerals as the regolith develop and soil formation progressed.

Size FractionCommon NameMeans of ObservationDominant Compositon

Very CoarseStone, gravelNaked eyeRock fragments

CoarseSandsNaked eyePrimary Minerals

FineSiltMicroscopePrimary and Secondary minerals

Very FineClayElectron MicroscopeMostly secondary minerals

These minerals are called secondary minerals. In general, the primary minerals dominate the coarser fractions of soil, whereas secondary minerals are most prominent in the fine materials, especially in clays. Clearly, mineral particle size will have much to do with the properties of soils in the field. (The Nature and properties of soil, Nyle C. Brady)

1. Soil Organic Matter

Soil organic matter represents an accumulation of partially decayed and partially synthesized plant and animal residues. Such material is continually being broken down as a result of the work of soil microorganism. Consequently, it is rather transitory soil constituent and must be renewed constantly by the addition of plant residues.

The organic matter content of a soil is small only about 3 to 5 percent by weight in a representative mineral topsoil. Its influence on soil properties and consequently on plant growth, however, is for greater than the low percentage would indicate. Organic matter functions as a granulator of the mineral particles, being largely responsible for the loose, easily managed condition of productive soils. Also, it is a major soil source of two important mineral elements, phosphorous and sulfur, and essentially the sole source of nitrogen. Through its effect on the physical condition of soils, organic matter also increases the amounts of water a soil can hold and the proportion of this water available for plant growth. Finally, organic matter is the main source of energy for soil microorganism. Without it, biochemical activity would come practically to a standstill.

Soil organic matter consists of two general groups: (a) original tissue and its partially decomposed equivalents, and (b) the humus. The original tissue includes the undecomposed roots and the tops of higher plants, These materials are subject to vigorous attack by soil organism, both plant and animal, which uses them as sources of energy and tissue building material.

The gelatinous, more resistant products of this decomposition, both those synthesized by the microorganisms and those modified from the original plant tissue, are collectively known as humus. This material, usually black or brown in color, is colloidal in nature. Its capacity to hold water and nutrient ions greatly exceeds that of clay its inorganic counterpart, Small amounts of humus thus augment remarkably the soils capacity to promote plant production. (The Nature and properties of soil, Nyle C. Brady)

1. Clay and Humus The Seat of Soil Activity

The dynamic nature of the finer portions of the soil clay and humus has been indicated. Both these constituents exist in the colloidal stage, wherein the individual particles are characterized by extremely small size, large surface of area per unit weight, and the presence of the surface charges to which ions and water are attracted.

The chemical and physical properties of soils are controlled largely by clay and humus. They are centers of activity around which chemical reactions and nutrient exchanges occur. Furthermore, by attracting ions to their surfaces, they temporarily protect essential nutrients from leaching and then release them slowly for plant use. Because of their surface charges, they also act as contact bridges between larger particles, thus helping to maintain the stable granular structure which is so desirable in a porous, easily worked soil.On a weight basis, the humus colloids have greater nutrient- and water-holding capacities than does clay. However, clay is generally present in larger amounts, and its total contribution to the chemical and physical properties will usually equal that of humus. The best agricultural soils contain a balance of the properties of these two important soil constituents.

COLLOIDO-BIOLOGICAL CONCEPT. Two major concepts must be emphasized before moving into a more detailed study of soil components. First, most of the chemical activity in soils is associated with a relatively small proportion of the total soil components the colloidally active clay and humus. Second, there is a vigorous soil organism population associated with humus and plant residues which largely controls the turnover of organic materials, including humus, and regulates the supply of several nutrient elements. These two ideas lead logically to the fact that the study of soils from the standpoint of plants can best be approach from a colloid-biological viewpoint. (The Nature and properties of soil, Nyle C. Brady)

1. Nutritional Importance of Soil pH

The soil pH may influence nutrient absorption and plant growth in two ways: (a) through the direct effect of the hydrogen ion; or (b) indirectly, through its influence on nutrient availability and the presence of toxic ions. In most soils the latter effect is of great significance. Although at extreme pH values the direct toxic effect of the hydrogen ion can be demonstrated, most plants are able to tolerate a wide range in the concentration of this ion so long as a proper balance of the other elements is maintained. Unfortunately, the availability of several of the essential nutrients is drastically affected by soil pH, as in solubility if certain elements that are toxic to plant growth.

Several essentials elements tend to become less available as the pH is raised from 5.0 to 7.5 or 8.0. Iron, manganese, and zinc are good examples. Molybdenum availability, on the other hand, is affected in the opposite way, being higher at the higher pH levels. Phosphorus is never readily soluble in soil, but it seems to be held with least tenacity in a pH range centering around 6.5. Here, most plants seem to be able to extract it from the soil with least difficulty.

At pH values below about 5.0, aluminum, iron, and manganese are often soluble in sufficient quantities to be toxic to the growth of some plants. At very high pH values, the bicarbonate ion is sometimes present in sufficient quantities to interfere with the normal uptake of other ions and thus is detrimental to optimum growth. These few examples of the indirect effectsw of soil pH show why much importance must be placed on this characteristic in the diagnosis of fertility problems. (The Nature and properties of soil, Nyle C. Brady)

1. NPK

2. Nitrogen

Nitrogen is a remarkable substance. It surrounds us, yet we cannot see it, feel it, or smell it. Nitrogen does even do very much scientist says it is inert, because it does not normally react with other substances. But without nitrogen, life would be impossible.Nitrogen compounds are a vital part of every living thing, since they are one of the main ingredients of the proteins from which cells are made. Every breath you take is mainly nitrogen, since nitrogen makes up almost four-fifths of air. The other main constituent is oxygen, and there are also small amount of carbon dioxide and water vapor.

At the center of each atom is a nucleus. This contains tiny particles called protons, which have a positive charge. Nitrogen has an atomic number seven which means it has seven protons. The nucleus also contains neutrons, which have no charge. The neutrons and protons give nitrogen an atomic mass of 14.

Around the nucleus are even smaller negatively charged particles called electrons. The number of electrons is the same as the number of protons, so the nitrogen atom also contains seven electrons. (The Elements Nitrogen, John Farndon)

0. Existence in Earth

In nearly all circumstances on Earth, nitrogen is a gas; it does not condense until the temperature plummets to -321F. It does not freeze until the temperature drops even further to -346F, which is far colder than anywhere ever found naturally on Earth.

Nitrogen is the sixth abundant substance in the universe. It is found in stars, in nebulae, in the sun, and in meteorites.

Most of the nitrogen in and around Earth is found in the atmosphere. There is very little nitrogen in Earths crust (the outer layer) or in its hot interior. But some nitrogen is found in the clouds of gas that erupt from volcanoes and in mineral water springs. A mineral called sodium nitrate, also known as Chile saltpeter, is mined in quarries and contains nitrogen attached to oxygen and sodium metal.

All plants and animals have nitrogen in their bodily cells. The amount of nitrogen inside living things is small in terms of the universe, but it is essential to life. (The Elements Nitrogen, John Farndon)

0. Procedure

To get the nitrogen in a sample soil: Measure 20 g of soil into a 100 mL cylindrical container Add 50ml of extracting solution Shake for 5 minutes on a reciprocal shaker. Read the potential while suspension is being stirred with magnetic stirrer. Record the millivolt reading (if using a calibration curve technique) or read the NO3N concentration directly from a pH/ion meter.(Recommended Chemical Soil Test Procedures)

2. Phosphorus

Phosphorus is a nonmetallic chemical element that is essential to all living organisms. The element is not found naturally on Earth but is always combined with other elements, especially oxygen, as compounds. Phosphorus also occurs in the Suns atmosphere and in meteorites reaching Earth from space. Its main use in industry is in the manufacture of phosphate fertilizers.

Just like all the other chemical elements, phosphorus is made up of tiny particles called atoms. In its nucleus the tiny bit heavy center of an atom each phosphorus atom has 15 positively charged particle called protons. No other element shares this number, and phosphorus is said to have an atomic number of 15.

The nucleus also contains other particles, called neutrons, which are about the same size as protons but uncharged. Some elements have different versions of their atoms, called isotopes that contain different numbers of neutrons. There is only one natural isotopes of phosphorus. It has 15 protons and 16 neutrons, making a total of 31 nuclear particles. Other isotopes can be made artificially but are radioactive, which means they will eventually break up.

Around the nucleus orbit 15 negatively charged electrons. Although electrons are much lighter protons, they balance the positive electrical charge of the protons, making the atom electrically neutral. (The Elements Phosphorus, Richard Beatly)

1. Existence in Earth

Phosphorus is found throughout the universe. It forms part of the atmosphere of the Sun and is also found in meteorites that reach Earth from space. The distribution of phosphorus on Earth has resulted from millions of years of activity under the surface of our planet. Molten material moving upward through the crust, for example, may cool down and separate out into different rocks, some of them rich in phosphorus. Some of these igneous rocks (created by fire) are mined commercially.

Phosphorus forms around 0.1 percent of Earths crust by weight. It is a highly reactive element and is always found combined with other element compounds. Most of the phosphorus on Earth is found in combination with oxygen, and the element nearly always occurs in nature as compounds containing the phosphate ion (PO43-). Phosphorus is essential to most living organisms. As a result, the element is concentrated in living things and their remains. Guano, the accumulated droppings of birds or bats, is rich in phosphorus. Deposits of guano are often collected and used as a fertilizer. (The Elements Phosphorus, Richard Beatly)

1. Procedure

To get the phosphorus content of a given soil, simply follow the steps: Scoop 2 g of soil Add measured volume of soil to a 50 mL Erlenmeyer flask, tapping the scoop on the funnel or 24 Recommended Chemical Soil Test Procedures flask to remove all of the soil from the scoop. Add 20 mL of extracting solution to each flask and shake at 200 or more epm for 5 minutes with the room temperature at 24 to 27C (8). Filter extracts through Whatman No. 42 filter paper or through a similar grade of paper. Refilter if extracts are not clear. Transfer a 2 mL aliquot to a test tube (or remove quantitatively all but 2 mL from the filter tube if color is to be developed in the filter tube). Add 8 mL of working solution so that thorough agitation and mixing occurs. Allow 10 minutes for color development. Read percentage transmittance or optical density on a colorimeter or spectrophotometer set at 882 nm. Color is stable for about 2 hours. Prepare a standard curve by aliquoting 2 mL of each working standard, developing color and reading intensity in the same manner as the soil extracts. Plot color intensity against P concentration of the standards. Determine ppm P in the extracts using the standard curve and convert ppm concentration in filtrate to concentration in the soil.(Recommended Chemical Soil Test Procedures)

2. Potassium

Potassium is one of the most common elements in Earths crust, but you are unlikely to find it as an element in nature. This soft, silvery-white metal is so reactive that it almost always exists combined with other elements as compounds. All living things from plants to people need potassium to stay healthy. Potassium compounds have many other important uses. They help matches to burn and give fireworks their bright, colorful explosions. They are also found in breathing apparatus, cotton dyes, liquid soaps and photographic chemicals.

Everything in the universe consists of tiny particles called atoms. Atoms are made up of even smaller particles called electrons, neutrons and protons. The neutrons and protons cluster together in the nucleus at the center of each atom. The electrons orbit the nucleus in layers called electron shells. There are 19 negatively charged electrons orbiting the nucleus of each potassium atom. The number of electrons and protons in an atom is always the same, so potassium has 19 positively charged protons in the nucleus. Neutrons are about the same size as protons but have no electrical charge. Most potassium atoms have 20 neutrons in the nucleus. (The Elements Potassium, Chris Woodford)

2. Existence in Earth

Potassium is the seventh most common element in Earths crust after oxygen, silicon, aluminum, iron, calcium, and sodium. In nature, most potassium occurs as crystals called feldspars and micas. Both of these crystals contain potassium combined with aluminum, silicon and oxygen. Rainwater and carbon dioxide (CO2) from the air gradually turn feldspars into potash (potassium carbonate; K2CO3). Potash supplies most of the potassium used by plants. Nature is very good at recycling chemical elements. Some of the largest natural deposits of potassium compounds on Earth today came from the remains of prehistoric plant life.

Other naturally occurring potassium compounds include silvite (potassium chloride; KCl), silvinite (a mineral formed from sodium chloride [NaCl] and potassium chloride), langbenite (a sulfate of potassium and magnesium), and carnallite (a mineral formed from potassium chloride, magnesium chloride [MgCl2], and water [H2O]). (The Elements Potassium, Chris Woodford)

2. Procedure

To get the amount of potassium in a soil, apply the procedures that follow: Scoop 2 g of prepared soil into an extraction flask. (See Chapter 2 for scooping techniques. Use the appropriate number of blanks and reference samples per laboratory quality assurance/quality control procedures.) Add 20 mL of extracting solution to the extraction flask. (Note: The quantity of soil and extracting solution may be varied as long as the 1:10 ratio is maintained.) Shake for 5 minutes on the shaker at 200 epm. Recheck speed weekly. Filter the suspensions through Whatman No. 2 or equivalent filter paper. Refilter or repeat if the extract is cloudy. Set up the atomic adsorption/emission spectrometer for K by emission. After warmup, determine the standard curve using the standards and obtain the concentrations of K in the soil extracts. To convert K concentration (ppm) in the soil extract solution to ppm in a soil (mg K/kg), multiply by 10. To convert to pounds of K per acre, multiply by 20.(Recommended Chemical Soil Test Procedures).