Preface Understanding the basic principles of agronomy is as much important as that of knowing the latest developments scenario in the field of agriculture. It is strenuous strive to keep pace with the progress of such a vast subject like agronomy which is in practice throughout the globe. The budding agronomist has to brace himself with the fundamentals of the agronomy right from the first year of B.Sc (Agri). Under this circumstance, important and relevant information about the various principles and practices of Agronomy are compiled in a book form entitled “Agronomy: Principles and Practices”. The book is divided into 15 chapters and which covers comprehensively the syllabus of the principles of agronomy offered for first B.Sc (Agri) as stepping stone to other courses in agriculture particularly the rest of the agronomic courses. The authors acknowledge their indebtedness to the authors/ publishers of various books from which they have drawn the matter for compiling this book. The list of which is attached at the end. The authors thank Dr. K. Ramasamy, Vice-Chancellor, Tamil Nadu Agricultural University for providing foreword and necessary guidelines for bringing out this book. The authors profusely thank all the Professors of the Department of Agronomy, TNAU, Coimbatore, for extending useful suggestions for drafting this book. The authors are much indebted to the Tamil Nadu Agricultural University, Coimbatore for providing an excellent opportunity to bring out this piece of work. The authors thank their family members for their help, physical and moral support and M/s. New India Publishing Agency (NIPA), New Delhi for their sincere efforts in bringing out this book in time.

Agriculture is derived from two Latin words Ager and Cultura. Ager means land or field and Cultura means cultivation. Therefore the meaning of the word agriculture is cultivation of land. Definitions Agriculture is defined in the Agriculture Act, 1947, as ‘‘including horticulture, fruit production, seed production, dairy farming and livestock breeding/keeping, the use of land as grazing land, meadow land, osier land, market gardens and nursery grounds, and the use of land for woodlands where that use is ancillary to the use of land for other agricultural purposes”. Agriculture is defined as ‘purposeful work through which elements in nature are harnessed to produce plants and animals to meet the human needs’. It is a biological production process which depends on the growth and development of selected plants and animals within the local environment. Agriculture is defined as the art, the science and the business of producing crops and the livestock for economic purposes. As an art it embraces knowledge of the way to perform the operations of the farm in a skillful manner, but does not necessarily include an understanding of the principles underlying the farm practices. The skill is categorized as; Physical skill: It involves the ability and capacity to plough the field in an efficient and quick manner, handling of farm implements, animals, sowing of seeds, fertilizer and pesticides application etc., For example: Taking a straight furrow. Mental skill: It involves the ability of the farmer to take a decision based on his experience, he decides the correct and accurate timing of operation, such as i) time and method of ploughing ii) selection of crop and cropping system to suit soil and climate, iii) adoption of improved farm practices.

History is the continuous record of past events Heritage is the inherited values carried from one generation to other generation Agricultural heritage refers to the values and traditional practices adopted in ancient India which are more relevant for present day system. Agricultural Heritage in India Agriculture in India is not of recent origin, but has a long history dating back to Neolithic age of 7500-6500 B.C. It changed the life style of early man from ‘nomadic hunter of wild berries and roots’ to ‘cultivator of land’. Agriculture is benefited from the wisdom and teachings of great saints. The wisdom gained and practices adopted have been passed down through generations. The traditional farmers have developed the nature friendly farming systems and practices such as mixed farming, mixed cropping, crop rotation etc. The great epics of ancient India convey the depth of knowledge possessed by the older generations of the farmers of India. The modern society has lost sight of the importance of the traditional knowledge which had been subjected to a process of refinement through generations of experience. The ecological considerations shown by the traditional farmers in their farming activities are now-a-days is reflected in the resurgence of organic agriculture.

The word agronomy has been derived from two Greek words, agros and nomos having the meaning of field and to manage, respectively. Literally, agronomy means the “art of managing field”. Technically, it means the “Science and economics of crop production by management of farm land”. Definitions Agronomy is the art and underlying science in production and improvement of field crops with the efficient use of soil fertility, water, labour and other factors related to crop production. Agronomy is defined as “a branch of agricultural science which deals with principles and practices of field crop production and management of soil for higher productivity.

In general crop is an organism grown or harvested for obtaining yield. Agronomically crop is a plants cultivated for economic purpose. Classification of Crops Classification is done to generalize similar crop plants as a class for attaining better understanding of them. Field crops are classified in the following ways. According to range of cultivation According to the place of origin Botanical classification Commercial classification Economic / Agricultural / Agrarian classification Seasonal classification Classification based on ontogeny

Internal Factors The increased yield and other desirable characters are related to the genetic make up of the plant. They are : High yields under given environmental conditions. Early maturity (in some cases late maturity). Resistance to lodging. Drought, flood and salinity tolerance. Tolerance to insects and diseases. Chemical composition of grains (high percentage of oil, increase in protein quantity or quality, etc.) Quality of grains (fineness, coarseness, etc.) Quality of straw (sweetness, juiciness, etc.)

Soil is defined as the thin layer of earth’s crust made up of disintegrated and decomposed rocks, complex mineral compound, organic matter, water/air and living organism like bacteria, fungi, insects and worms and serves as the natural medium of growth of plants. It provides nutrients, moisture, anchorage (support) and provides air to root system. There are different soil groups found in varied regions of India. Each group differs from other in physical and chemical properties. The variation in behaviour is mainly due to the nature of the parent material from which the soils are formed. Parent materials are Igneous rocks, sedimentary rocks and metamorphic rocks. Physical properties like structure, texture, colour, water holding capacity, depth etc. are to be noted. Chemical properties like the presence of various plant elements, pH, EC, CEC, acidic or alkaline, etc. are considered.

Agricultural Seasons Season is defined as “part of the year during which a distinguished type of weather prevails”. A) Seasons of Temperate region Spring (March – May) is the first season of the year in which plants being to grow and leaves emerge. Summer (June – August) is the second and warmest season of the year out side the tropics during which plants flourish Fall or Autumn (September – November) is the third season of the year in which leaves turn brown. Winter (December – February) is the last and the coldest season of the year. Many trees loose their leaves.

For better understanding of different systems of farming it is essential to study certain terminologies. Farm is a piece of land with specific boundaries, where crop and livestock enterprises are taken up under a common management. Farming is the process of harnessing solar energy in the form of economic plant and animal products or it is the business of cultivating land, raising livestock etc. System refers to an orderly set of interdependent and interacting components none of which can be modified without causing a related change elsewhere in the system. There are three district systems of farming as wetland system of farming, garden land (irrigated dry land) system of farming and dryland system of farming. Wetland: Pertaining to soils flooded or copiously irrigated through lake or pond or tank for a least several weeks in each year (or) to crop growth in such soils. The water is not entirely under the control of the farmer.

Tillage operations in various forms have been practiced from the very inception of growing plants. Primitive man used tools to disturb the soils for placing seeds. The word tillage is derived from the Anglo-Saxon words tilian and teolian, meaning to plough and prepare soil for seed to sow, to cultivate and to raise crops. Jethro Tull, who is considered as father of tillage suggested that thorough ploughing is necessary so as to make the soil into fine particles.

Seed is a fertilized ripened ovule consisting of three main parts namely seed coat, endosperm and embryo which in due course gives rise to a new plant. Seed is the nucleus of life. Endosperm is the storage organ for food substance that nourishes the embryo during its development. Seed coat is the outer cover that protects or shields the embryo and endosperm. Importance Plants reproduce sexually by seeds and asexually by vegetative parts. Grains which are used for multiplication are called seeds while those used for human or animal consumption are called grains. Good stalks of planting materials are basic to profitable crop production. The seed or planting material largely determines the quality and quantity of the produce. A good seed or stalk of planting material is genetically satisfactory and true to type, fully developed and free from contamination, deformities, diseases and pests.

Crop Stand Establishment Good crop establishment is one of the most important features in better crop production. The better crop establishment is in turn expressed as optimum plant population in fields. Plant population is the number of plants per unit area in a cropped field. It indicates the size of the area available for individual plant. Optimum Plant Population It is the number of plants required to produce maximum output or biomass per unit area. Any increase beyond this stage results in either no increase or reduction in biomass. Crop geometry is the pattern of distribution of plant over the ground or the shape of the area available to the individual plant, in a crop field.

Weeds are the plants, which grow where they are not wanted. Jethro Tull (1731) coined the word weed. Weeds can also be referred to as plants out of place. Definition Weeds are unwanted and undesirable plant that interfere with utilization of land and water resources and thus, adversely affect crop production and human welfare. In organic agriculture weeds are treated as childrens of the soil. In the world 30,000 species of weeds have been listed, of which nearly 18,000 cause serious damage to agricultural production. Eighteen weeds are considered as the most serious in the world and about twenty six species have been listed as principal weeds in crop fields of India, and are listed in annexure V

Irrigation Irrigation is defined as the artificial application of water to the soil for the purpose of crop production in supplement to rainfall and ground water contribution. Time of Irrigation The time schedule which indicates when irrigation water is to be applied and the quantity of water to be applied at that time is called irrigation schedule. There are several approaches for scheduling irrigation: Soil moisture depletion approach based on the available soil moisture in the root zone. Climatological approach based on the amount of water lost by evapotranspiration. Combination approach based on soil moisture depletion and climatological approaches. Critical stage approach which indicates the growth stages at which moisture stress leads to yield loss. These stages are known as critical period or moisture sensitive period. In cereals and millets panicle initiation and flowering stages are moisture sensitive stages. In pulses and oilseeds, flowering and pod development stages are critical stages. In sugarcane active tillering or formative stage is critical and in cotton boll development is the critical stage.

Growth is the development of a plant as a whole or of a specific organ. Besides the genetic factors, the environmental factors grouped as climatic factors and soil factors influence plant growth. The supply of mineral nutrient elements to the plants is discussed in this chapter. A complete analysis of plants detects large number of elements. But only certain elements are essential. An element is said to be essential if the plant cannot complete its life cycle without it, and if the malady (deficiency) that develops in plants in its absence can be remedied only by that element. Earlier 16 elements were considered as essential for plant growth. They are carbon, hydrogen, oxygen, nitrogen phosphorus, potassium, calcium, magnesium, sulphur, iron, manganese, zinc, copper, molybdenum, boron and chlorine. Recently, sodium, cobalt, vanadium, silica, selenium, gallium, aluminium and iodine are added to the above list. One or the other of these elements (recently added) has been found to be essential for a particular species of plants. Carbon dioxide, water and molecular oxygen are the forms in which C., H and O are assimilated by plants. Others are taken up by plants from the soil. Nutrient uptake by plants accounts for about 10 percent of total dry weight of crops, the remaining percentage being water. The chemical symbol and the ionic forms in which the essential elements are absorbed by the plants are as follows.

Harvesting: “Removal of entire plant or economic parts after maturity from the field" is called harvesting. It includes the operation of cutting, picking, plucking or digging or a combination of these for removing the useful part or economic part from the plants / crops. The portion of the stem that is left in the field after harvest is called as stubble. The economic product may be grain, seed, leaf, root or entire plant. Harvest Index: (H.I): It is the ratio of the economic yield to the total biological yield expressed as percentage. H.I = Economic yield / Biological yield x 100 Time of Harvesting: If the crop is harvested early, the produce contains high moisture and more immature ill filled and shriveled grains. High moisture leads to pest attack and reduction in germination percentage and impairs the grain quality. Late harvesting results in shattering of grains, germination even before harvesting during rainy season and breakage during processing.

Selected References Biwas, T.D. and S.K.Mukherjee. 1994. Text Book of Soil Science, Tata Mc Graw Hill Publishing Company Ltd., New Delhi. Brady, N.C. 1990. The Nature and Properties of Soils, Mac Millan Publishing Co., New York, USA. Cheema, S.S., Dhaliwal, B.K. and T.S.Sahota. 2000. Theory and Digest Agronomy, Kalyani Publishers, New Delhi. Dahama, A.K. 1996. Orgnaic Farming for Sustainable Agriculture, Agri. Botanical Publishers, Bikaner. DAS, P.C. 2000. Manures and Fertilizers. Kalyani Publishers, New Delhi. Gopal Chandra De. 1997. Fundamentals of Agronomy, Oxford and IBH Publishing Co. Pvt. Ltd., New Delhi. ICAR. 1996. Handbook of Agriculture, Indian Council of Agricultural Research, New Delhi. Mandal, R.C. and P.K. Jana. 1998. Water Resource Utilization and Micro-irrigation; Sprinkler and Drip System, Kalyani Publishers, Ludhiana. Michael, A.M. 1978. Irrigation – Theory and Practice, Vikas Publishing House Pvt., Co. New Delhi. Morachan, Y.B. 1986. Crop Production and Management, Oxford and IBH Pub. Co.New Delhi.