eChapters

Methods of soil fertility evaluation          
    I.    Nutrient deficiency symptoms on plants  
    II.    Plant analysis
    III.    Biological tests   
    IV.    Soil testing
    V.    Spectral sensing for site specific evaluation

The active management of soil nutrients to ensure optimal plant nutrition has been a fundamental practice in agriculture since its inception. For centuries, production of agriculture depended on the organic materials recycling like manure and crop residues. Interest in plant nutrition dates back to ancient times, first captivating philosophers and later becoming a subject of rigorous scientific inquiry. The history of how plants obtain nutrients is marked by numerous misconceptions and incorrect theories. Exploring the long-standing efforts to uncover this essential agricultural process highlights the perseverance and brilliance of early thinkers and scientists. It also underscores that modern understanding, which may now seem straightforward, is the culmination of significant scientific endeavour. The concept of managing fertility of soil to boost yield of crops is far from new—its origins are intertwined with the earliest practices of agriculture. Ancient civilizations recognized the value of applying organic matter such as green manure, farmyard manure, night soil, bone, and wood ashes to enhance soil productivity.

Introduction

In India, hot arid ecosystem covering an area of 31.7 million ha lies at north western part of the country and 62% of this area falls in western Rajasthan covering 12 districts i.e. Jodhpur, Jaisalmer, Jhunjhunu, Sikar, Hanumangarh, Sri Ganganagar, Bikaner, Barmer, Pali and Sirohi. The major landforms in arid western Rajasthan are dune and inter-dune plains having sandy to sandy-loam textured soils. Temperature remains high for most part of the year reaching up to 42-45°C during prolonged summer months (April to July), whereas annual rainfall is very low and highly sporadic (100-400 mm) mainly occurs during August and September. Annual potential evapotranspiration ranges from 1500-2000 mm. Loss of fertile top soil from denuded soil surface through wind erosion is frequent during summer months. The region is subjected to frequent occurrence of droughts, once in every three years, which further intensifies the process of desertification (Samra et al. 2006). Shorter growing period, sandy soils, very low available water capacity, inadequate nitrogen and phosphorus availability are the major constraints. Soils are prone to severe wind erosion, terrain deformation and nutrient depletion. The region is mostly mono cropped and double cropping is being practiced extensively in canal and tubes well command area. Extensive fallowing in the past even in very good rainfall years because of uneven undulating topography and severe windstorm are the cause of concern. Ground water is deep and is usually brackish, declining at alarming rate due to excessive withdrawal for irrigation and other purposes. The region, however, sustains on perennial vegetation of Prosopis cineraria, Tecomella undulata, arid shrubs and grasses, which are rich resources of fodder for animal because cropping is affected by vagaries of monsoon. During last two to three decades, a 2 to 3-fold increase in irrigated areas with cultivation of both kharif and rabi crops has been recorded and most of these increments are resulted through conversions from rainfed areas, grazing lands and sand dunes into irrigated areas.

Soil fertility management refers to the practices and techniques used to maintain and improve the fertility of soil. Soil fertility is crucial for agriculture because it determines the soil's ability to provide essential nutrients to plants, support their growth, and sustain productivity over time. Effective soil fertility management aims to optimize soil health and productivity while minimizing environmental impacts.

3.1 Key Aspects of Soil Fertility Management Include

1. Nutrient Management: This involves supplying essential nutrients (nitrogen, phosphorus, potassium, etc.) to the soil through organic or synthetic fertilizers to meet the needs of crops.

2. Soil Amendments: Adding organic matter (such as compost or manure) or other amendments (like lime or gypsum) to improve soil structure, water retention, and nutrient availability.

3. Crop Rotation and Diversification: Rotating crops and diversifying plant species can help manage nutrient depletion and improve soil health by reducing pest and disease pressures.

4. Conservation Tillage: Minimizing soil disturbance through reduced tillage or no-till practices helps preserve soil structure, reduce erosion, and maintain organic matter content.

5. Cover Cropping: Planting cover crops during fallow periods or between main crops helps prevent soil erosion, improve nutrient cycling, and enhance soil fertility.

Soil fertility

• Soil serves as a source of nutrient required for the growth and development of plant. This characteristic of soil is called soil fertility.

Management practices

• Improved organic matter and soil moisture in soil, favours the growth of micro-organism beneficial for maintaining fertility of the soil.

Manures

• It is an organic waste material of plant and animal origin. It is used improvement of soil fertility. There are major 2 types of manure

1. Bulky organic manures
2. Concentrated organic manures

14.1. Soil fertility

Ability of the soil to supply essential plant nutrients during growth period of the plants

Crop producing capacity of the soil

Abstract

Understanding the impacts of organic or inorganic nutrient management on soil biology and biochemistry may help to develop more sustainable fertilization strategies. The results from comprehensive study made on a field experiment comparing the long-term (more than 100 years) effects of organic manures and inorganic chemical fertilizers on soil biological and biochemical properties are reviewed. The soils adopted with three nutrient managements viz., no fertilization (control), inorganic chemical fertilizers (IC) and organic amendments (OM) obtained from long-term fertilizer experiment were assessed for physical, chemical, microbiological and biochemical properties in three successive years. The response of most of the assessed soil variables to long-term organic nutrient management was significantly higher than those from inorganic fertilization and control (OM > IC = control).

Introduction

Ideal plant health and productivity of a cropping system depends on an adequate amount of plant nutrients. Fertility of the soil refers to its capacity to support the production of crops. A productive fertile soil can support optimal plant growth, seed germination to plant maturity by providing adequate soil volume for plant root development, essential plant nutrients to meet the nutritional requirements of the plants, and encourage for the consequent plant structure. These attributes of the soil can be distinguished as inherent or dynamic soil quality indicators.Optimum plant health and productivity of a cropping system depends on an adequate supply of plant nutrients. The quantity of nutrients required by plants varies depending on many interacting factors including:

• Agronomic effects

• Soil properties

• Climatic condition

• Management practices

ACID-FORMING FERTILIZER: A term applied to commercial fertilizers which leave an acid residue in the soil. The amount of calcium carbonate required to neutralize the acid residue is referred to its equivalent acidity.

Soil fertility is defined as the quality that enables the soil to provide proper nutrient compounds in proper amounts and in proper balance for the growth of specified plants. Soil fertility is also defined as the ability of soil to supply adequately the nutrients normally taken from the soil by plants.

Soil fertility is the resultant of several factors, not the least important of which is the soil itself. Theoretically, the soil only plays the part of a support and could be very easily dispensed with and replaced by sand and even that can be replaced by a wire framework to support the plant mechanically and it will grow quite well if the right amount of nutrient materials have been added to water. ‘Where does the soil come in?” you will ask. The importance of the soil is two-fold: (1) It provides vast reserves of plant food which is slowly made available. (2) It provides limiting factors which restrict plant growth; these limiting factors must be neutralized. We have already discussed these reserve food materials and limiting factors in Chapter II.

It has been shown that if we treat a soil with dilute acid exhaustively we can remove everything from it except the mineral framework. If we try to grow anything in this mineral framework nothing will grow. Yet it is not like sand, for whereas in sand by adding appropriate amounts of nutrient materials in water solution you could grow a crop, nothing will grow if you added the same solution of nutrient materials to the soil. This mineral framework, therefore, is not inert like sand, but it is active and can react with the nutrient salts in such a way that either they are rendered unavailable or something else which is toxic is produced by the interaction between the soil and the nutrient salts. This mineral framework is not acted upon by dilute acids, but it reacts with alkalies in such a way that the alkalies are neutralized. In this respect, therefore, the mineral frame work behaves like an acid. With alkalies it forms salts and different alkalies are required in equivalent amounts for the formation of these salts. Thus we can have salts of a number of bases and if we use sodium hydroxide for neutralizing we shall have sodium soil, similarly we can have a calcium, magnesium or potassium soil. Now in nature, all the various bases principally, calcium, magnesium, sodium, and potassium, are associated with it in different proportions. The nature and amount of these bases determines the physico-chemical properties of the soil affecting crop yield and leading to soil infertility. We have already indicated the method of bringing the soiil to the normal state when it suffers from any of the defects associated with the soil framework.

1. White alkali soils also know as

a. Acid soil                  b. Saline soil

c. Saline sodic soil    d. Sodic soil

Although the application of fertilizer to even fairly fertile soils can give a great increase in crop yield, soil fertility is not simply a matter of nutrient content. It is dependent on a number of complex of issues:

Soil depth

The volume of soil from which the crop draws its nutrition varies according to the rooting depth of the crop. However hard or rocky layers can restrict natural root development; this is particularly the case with micro irrigation systems.

Soil structure

Particle size and soil aggregate size and distribution, effect the size and distribution of pores and therefore the availability of air and water to the roots.

Introduction

Pedology:- Pedology word drive from Greek word pedon, means soil or earth and logos means to study. Pedology is concerned with origin of the soil, its classification, distribution and character (Physical, Chemical and Biological).

Definition:- Soils are natural bodies made from both mineral and organic materials and capable of supporting plants out-of-doors.

Composition of soil on volume basis (Soil components)

i. Mineral matter :- 45%

ii. Organic matter :- 5%

iii. Soil water :- 25%

iv. Soil air :- 25%

Soil formation is a long term process. It takes several million years to form a thin layer of soil. The soil is made up of broken down rock material of varying degree of fineness and changed in varying degrees from the parent rocks by the action of different agencies such that the growth of vegetation is made possible. As soil is a complex mixture of various components, its formation is also more complex. The Formation of a particular type of soil depends upon the physico-chemical properties of the parent rock, intensity and duration of weathering, climatic and other parameters.

Soil formation takes place in two consecutive stages:

1. The weathering of rocks into regolith

2. The formation of true soil from regolith

The evolution of true soil from regolith takes place by the combined action of soil forming factors and processes. The first step is accomplished by weathering (disintegration and decomposition) and the second is associated with the action of soil forming factors which are known as pedogenic factors.

The pedogenic processes are dynamic and extremely complex involving several chemical and biological reactions, usually operating simultaneously in a given area. One process may counteract another, or two different processes may work in tandem to achieve the same result. Different processes or combination of processes operate under varying natural environments. The combined interaction of various soil forming factors under different environmental conditions set a furtherance to certain recognized soil forming processes. Pedogenic processes include:

Rock

A rock may be defined as “an aggregate of one or more minerals”. An aggregate of single mineral calcite gives rise to crystalline limestone. Granite is a combination of several minerals. Most rocks are hard and compact as granite and basalt, but some are loose and feebly aggregated as sandstone. Rocks possess certain characteristics such as structure, colour, specific gravity, cleavage and mineralogical make-up by which we can identify the rocks and also distinguish one from the other.

2.1. Minerals

Primarily, minerals are usually inorganic substances possessing a definite chemical composition and a definite molecular arrangement which is usually expressed in geometric form. The mineral matter is made up of various elements, combined to form compounds. Usually, minerals consist of more than one constituent elements. Quartz contains two elements, silicon and oxygen. Other minerals may contain many elements, such as amphibole consists of several elements that include sodium, calcium, magnesium, iron, aluminium, silicon, and oxygen. Some elements exist as such without forming compounds. They contain exceptionally one element. Graphite (C), diamond (C), and Sulphur (S). Minerals are naturally occurring crystalline solid where the atoms are arranged in a regular three-dimensional array. A crystal is a solid, formed by a repeating three-dimensional pattern of atoms, ions, or molecules & possessing fixed distances between the different parts. Minerals that do not grow in these regular or crystalline patterns are called amorphous solids. When we talk about ‘naturally occurring’, we exclude the laboratory-synthesized crystalline solids. Glass and amber are also naturally occurring solid, but they are not crystalline and thus, they are not considered as minerals, rather they are referred as amorphous solids.

Soil genesis, or pedogenesis, is the combined effect of physical, chemical, biological and anthropogenic processes working on soil parent material (rocks & minerals). Soil is said to be formed when organic matter has accumulated and colloids are washed downward, leaving deposits of clay, humus, iron oxide, carbonate, and gypsum, producing a distinct layers. These constituents are moved from one level to another by water and animal activity.

Introduction

Soil health and fertility are pivotal to the success and sustainability of agricultural systems. The condition of soil directly influences plant growth, crop yield, and overall farm productivity. A focus on soil health encompasses not just the physical and chemical properties of soil but also its biological vitality, which includes the diverse community of microorganisms, fungi, and fauna that interact within the soil ecosystem. Biodynamic farming, founded by Rudolf Steiner in the early 20th century, offers a distinctive approach to soil health and fertility, integrating organic principles with a holistic view of agriculture that encompasses cosmic and spiritual dimensions. Biodynamic farming is an agricultural philosophy that extends beyond conventional organic practices. It views the farm as a living organism, where soil, plants, animals, and cosmic forces are interconnected and interdependent. This perspective emphasizes that the health of the soil is intrinsically linked to the broader ecological and cosmic environment. According to biodynamic principles, soil fertility is not merely a function of nutrient inputs but a reflection of the overall balance and vitality of the farm ecosystem.