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Of the various weather elements affecting crops, temperature and rainfall are perhaps the most important. It is the reason for the development of special flora and fauna in different climatic zones of the world as seen in the tropical, temperate and frigid zones. The tropical regions get abundant solar heat and the vegetation is high while it is low in the temperate regions. The vegetation is very little in the frigid zones. Similarly, natural vegetation is at its poor growth in the Arid Climates and better in the Humid Tropics. Xerophytes are confined to the Arid Climates where low rainfall is seen, while hydrophytes are confined to the Humid Tropics. Mesophytes are intermediate in their water requirement. Most of the crops are included in this group. If the crops are selected for cultivation on the basis of the optimum climatic requirements, it is likely that crop production can be maximised under rainfed as well as irrigated conditions. For example, coconut is grown in vast areas across the East and West Coasts of the Country in different agroclimatic zones and known as a coastal tree. It gives reasonably better yield in terms of quantity and quality in the Humid Tropics under rainfed conditions. However, the coconut yield scenario is totally different when the crop is cultivated in Semi-arid Tropics under irrigation. Therefore, it is a complex phenomenon to understand the influence of weather and climate on crops under rainfed and irrigated conditions in various climatic zones. The production potential of crops under field conditions could be explained through crop-wise agroclimatic zonation, whether the crop is well-suited with minimum inputs for maximising yields under rainfed conditions, but not under irrigated conditions due to crop manipulation. Many attempts were made to explain the climatic boundaries for various crops based on agroclimatic indices under rainfed conditions.

Introduction

The interest in soil as a natural body originated from its ability to produce and sustain crops. The scientific study of soil probably started in the mid-nineteenth century and was dominated by geologists, chemists and plant physiologists. Justus von Liebig (1840) in his famous publication, Chemistry Applied to Agriculture and Physiology, put forward the theory that plants assimilate mineral nutrients from soils which varied in their capacity of nutrient supply. The ‘Law of Restitution’ propounded by him states that whatever is being taken by plants from the soil needs to be restored to maintain the nutrient supplying capacity of the soil.

Rocks and minerals formed under a very high temperature and pressure, when exposed to atmospheric conditions of low pressure and low temperature, they become unstable and weather. Soils are formed from rocks through the intermediate stage of formation of regolith (parent material) which is the resultant of weathering.

3.1. What is weathering?

Weathering may be defined as the transformation process of solid rocks, involving the disintegration and decomposition of rocks and minerals, into soil.

There are different types of weathering: physical, chemical and biological.

3.1.1. Physical weathering

In physical weathering the chemical composition of the weathered products remains same as that of the parental rocks. It is involved in fragmentation of rocks into comparatively smaller sizes. It does not transform the parental rock into a newer one that may differ from the parental rock in chemical composition. The process is totally physical in nature. But this is also true that physical weathering encourages chemical weathering, and both may be carried out simultaneously because physical weathering promotes more surface area of parental rocks for more interaction with agents of chemical weathering.

INTRODUCTION

For centuries, social and technological changes have been affecting every profession. During the last two decades rapid technological development has affected library services as well. Specifically for the last five years, Web 2.0 technologies have significant impact on the higher education sector as well on the libraries all over world. Tim O’Reilly invented the term Web 2.0 in 2004

ABSTRACT

Expert systems are very popular computer programs designed to simulate the problem solving behavior of human thinking in a narrow domain. The world has changed into a global village. Information has become a powerful commodity and agricultural production has evolved into a complex business requiring the accumulation and integration of knowledge and information from many diverse sources. Rice is the staple food of over half the world’s population. India is the second largest producer and consumer of rice in the world. In order to remain competitive, the modern farmer often relies on agricultural specialists and advisors to provide information for decision making. In order to alleviate this problem, expert systems were identified as a powerful tool with extensive potential in agriculture. Rapid development of web technology benefits our decision-making and various activities in agriculture. With this background, web based rice expert system has been developed for diagnosing pest and disease problems of rice crop.

Key Words: Rice, Expert system, Knowledge, Decision making

Introduction

The innovative use of web technologies enables us to reach both local and distant users much more easily and effectively. Technologies such as email and Web provide tremendous opportunities for library & Information Scientists to deliver the information to the desktops of users. Web offers significant advantage by integrating different library & information services with a common user interface offered by Web browsers.

INTRODUCTION

The World Wide has become one of the most important media for sharing information resources, digital documents, images, movies and various other types of resources. The research results, new findings, and opinions can also be put on the web from any where at any time. Owing to the dynamic nature of web information, the contents of many websites and their web pages are constantly being updated to reflect the latest changes.

The Web has also freed the user‘s dependence on library resources for finding information related to address and contact details of a person/institution, contents pages of books, journals, etc. Looking at the web has become an innovative trend in the reference service to complement dated print sources. At present many academic institutes in India have their own website and present all kinds of information about themselves. Information content is, however, one thing; Web site design and organisation is quite another matter. The existing institutions of Web sites are as different as are the institutions because even a high-quality institution may have a low-quality Web site that turns users off. Obviously, different institutions have a wide range of target groups, level of service, resources etc. Stover (1997) has outlined the different types of Web sites that academic, public and special libraries have created.

Abstract

A huge technical improvement in Information Technology (IT) has made new instruments (e.g. WEB-GIS, Open Source platforms, DBMS with geometric data) available. Distributing geospatial information on the Internet is an enforcing factor for information providers. For dissemination of spatial data, Web-GIS technology can be used, which is amalgamation of several information technologies. Open Source is a philosophy of providing software with better quality, more flexibility, and lower cost. This paper explains the use of Open Source Web-GIS which provides a fast and globally reachable way not only to represent the information about natural resources through maps and statistics but also possibility of processing the information interactively on web.

Keywords : Web-GIS, Open Source, PostgreSQL, PostGIS, GeoServer, Wetlands

1.0 Introduction

India is blessed with diverse and abundant resources. India has been witnessing tremendous growth which has impacted practically every aspect of environment and the common man. Natural resource has been tremendously in use due to increase in population growth, thus generation, dissemination and sharing of information regarding natural resources and data amongst all stake holders have become a necessity. The utilization of modern technologies such as remote sensing, GIS which are effective in management of natural resources as user can store, retrieve and model the spatial information. Web media is playing a vital role in making people aware about the importance and conservation of natural resources. We are presenting such efforts with use of Free and Open Source Software (FOSS) tools.

The vision 2020 document of the Department of Agriculture and Co-operation envisages that “the tools of ICT will provide networking of Agriculture Sector not only in the country but also globally and the Centre and State Government Departments will have reservoir of databases” and also “bring farmers, researchers, scientists and administrators together by establishing ”Agriculture Online” through exchange of ideas and information”. To get realize the vision 2020 a large number of agriculture based websites and web portals have been established in India which is working for wellbeing of farming community. Majority of agricultural websites and web portals are providing need based technological information to the farmers as well as extension professionals. To revitalize our extension system these web based services can be used as ICT tool by extension personnel and farmers also. Therefore, to get access services from these websites and web portals or to replicate these ideologies in other part of country, elementary knowledge of working process and services available on these websites & web portals is essential. This chapter will provide a brief description about major ICT based projects dedicated to Indian farmers.

Weed Biology

Weed biology is the study of the establishment, growth, reproduction, and life cycles of weed species and weed societies/vegetation. Weed biology is an integrated science with the aim of minimizing the negative effects, as well as using and developing the positive effects, of weeds.

Life Cycle - Based on life cycle weeds are classified as annuals, biennials or perennials.

Annuals

Annuals complete their life cycle from seed in less than one year. There are two types: summer and winter annuals. Summer annuals germinate in the spring, mature, produce flowers and seeds and die before fall. Winter annuals germinate in the fall, overwinter in a seedling or rosette stage, mature, produce flowers and seeds, and die in the spring or early summer. Because of the seedling stage, annual weeds are generally easy to control. There are usually few annual weeds present in low bush blueberry fields.

Biennials

Biennials generally complete their life cycle over two years. The first year the seeds germinate and form a basal cluster of leaves and a tap root. The plant overwinters in this stage. During the second year the weed produces a flower stalk, sets seed and dies. Examples of biennial weed are evening primrose and wild carrot.

Methods of Weed Control

Prevention, eradication and control are the fundamental principles of weed control.First basic step is to prevent the infestation of a weed(s) in a locality in order to avoid their further spread. If one fails in preventing spread of weeds, eradication step must be adopted. Eradication is limited on a very small scale and adopted only when suitable methods of complete weed removal are available as eradication is cent per cent control of weeds alongwith its root system and other propagative parts. Further, if one fails in prevention and eradication techniques then different weed control methods must be strictly followed in which the objective is to bring down the weed population (with any method) to a level that economical crop yields are possible. The aim of each weed control method is to achieve reasonable good control of weeds. Following methods for controlling weeds are very common:

Preventive Methods

Try to prevent spread of weed seeds/vegetative parts with the adoption of following preventive techniques.

Weeds have been a problem to agriculture ever sine man started cultivation. Weed species by and large invade cropped areas and account for large economic losses to the farmer. Weeds are economically more important than insects, fungi or other pest organisms (Savary et al. 2000, 2006). Globally, weeds cause the highest potential loss to crop production (34%), with animal pests and pathogens being less important (losses of18% and 16% respectively). The loss in production due to weeds has been estimated as 5% in developed countries. It is around 10% in developing countries and 25% in least developed countries. (Oerke, 2006)

Weed Ecology

Ecology is the study of reciprocal relationship between organisms and their environments. The ecology of weed is thus concerned with growth characteristics and adaptations that enable weeds to exploit the ecological niches left open in those environments altered by man for his use and the survival mechanisms where by weeds persist in such environments. In simple words weed ecology is reciprocal relationship of weeds with their environments. Weeds grow voluntarily in all crops raised by human beings since ancient ecology of weeds is divided into two categories (types).

1. Weed Auto Ecology

It is study of only one population i.e. how an individual species in a population interacts with its environment at all stages of its life cycle. So, in case of auto ecology competition within same species (intraspecific) or with crop plants (inter specific competition) is studied.

2. Weed Synecology

The study of relationships between communities of different weed species with their environment is called weed synecology. Different weed species grow in certain combinations and in specific patterns in the ûeld. The population of different weed species interact with the external environmental conditions and among themselves. Weed communities differ from field to field and crop to crop in the same locality. The community character is dynamic and changes in form and composition of weed flora takes place in course of time due to some external and internal factors prevailing in the community. This process is called ecological succession. With the passage of time there will be series of changes in the composition of weed community which ultimately results in stable community. This is termed as climax community.

Abstract

Invasion of field crops, orchards and waste-lands by weeds is a matter of concern for farmers and foresters because of the drag they inflict on productivity and the increase in cost of production involved in weed control. Science-based technologies offer workable and reliable recourse to minimizing and/or eliminating these losses to promote healthier and rewarding livelihoods. While studies have been conducted to combat brush-weed in waste-land and plantations, little work has been done on such aspects as biological control of weeds, development of herbicide resistance in weeds, and allelopathic interface of crops and weeds. In this chapter, attempt is made to assess the economics of weed management in major crops. Aspects of R&D on weed management that should be addressed for safeguarding yield in the future are highlighted with particular reference to situation in western Himalaya.

Weeds are unwanted and undesirable plants which interfere with the utilization of land and water resources and thus adversely affect crop production.

Classification of Weeds

Weeds can be classified in three different manner based on morphology, life cycle, habitat and origin.

6.1 Introduction

The birth of modern conventional agriculture coincides with industrial revolution. The identification of N, P and K as critical factors in plant growth led to the manufacture of synthetic fertilizers. While chemical fertilizers and pesticides have existed since the 19th century, their use grew significantly in the early 20 century with the invention of Haber-Bosch method for synthesizing ammonia. The rapid farm mechanization, especially in the form of tractor and combine harvester coupled with science-driven innovative management methods and resources led to the efficiency of enabling outputs of high quality produce per unit area and time.

Weeds have been existing on the earth ever since the man started domesticating /cultivating plants and animals around 10,000 B.C. and recognized as a problem since then. The battle against weeds is a never ending one and often the costliest agronomic input for successful crop production. Weeds are most under estimated crop pests in tropical agriculture although they cause higher reductions in crop yields than other pests and diseases. Of the total annual loss of agricultural produce from various pests in India, weeds roughly account for 37%, insects for 29%, diseases for 22% and other pests for 12%. Weeds decrease quantity and quality of the produces [food, fibre, oil, forage/ fodder, animal products (meat and milk)] and cause health hazards for humans and animals. Therefore, weed control is very important for a successful crop production.

Abstract
India shares one fourth of global annual grain legume production and is also largest consumer of it. Weeds are the most severe and widespread biological constraint on agricultural production systems and cause damage to cropped and non-cropped lands. They reduce crop yield and degrade the quality of the produce, besides raising the cost of production. The grain legumesare commonly grown under rainfed/dry land conditions and hence do not receive the best management practices that are required for maximization of crop productivity. Among various production inputs, weed management was found to be the most important one contributing about 31% in pigeon pea, 110% in urdbean and 60 % in mungbean towards total productivity. Effective weed management in grain legumes is essential for optimizing
crop yield and quality. This process involves a multi-faceted approach that integrates cultural, mechanical, and chemical methods to address the challenges posed by diverse weed species and varying environmental conditions. Traditional single-method approaches often fall short due to the complexity and variability of weed problems like development of resistance in weeds. Therefore, an integrated weed management approach becomes effective, combining timely interventions with adaptive strategies to manage weed competition throughout the growing season. This approach not only enhances crop competitiveness and yield but also offers economic and environmental benefits by reducing reliance on broad-spectrum herbicides and promoting sustainable practices. Continuous monitoring and adjustment
of weed management strategies are crucial to effectively tackle evolving weed populations and changing conditions, ensuring long-term success in grain legume cultivation.
Keywords: Broad-spectrum herbicides, Crop productivity, Crop weed competition, Grain legume, Integrated weed management

Weeds are unwanted and undesirable plants which interfere with the utilization of land and water resources and thus adversely affect human welfare. They can also be referred as plants out of place. Weeds rank first among different agricultural pests causing crop loss. About 30,000 species of weeds have been listed in the world, out of which 18,000 cause serious damage in different ways resulting in considerable loss to agricultural production.

1. DEFINITIONS

Various definations of weed have been proposed. Weed is defined as a valueless plant growing wild, especially one that grows on cultivated ground to the exclusion or injury of the desired crop. Weed means any undesirable or troublesome plant, especially one that grows profusely where it is not wanted. The weed have also been defined a plant considered undesirable. Weeds are commonly unwanted plants in human-controlled settings, such as farm fields, gardens, lawns and parks. A weed may be any plant that grows or reproduces aggressively, or is outside its native habitat. Some plants that often are considered to be weeds are Bermuda grass, creeping Charlie, dandelion, golden rod, poison ivy, ragweed, wild carrot, wood sorrel, nutsedge etc.

The term weed can be described in many ways. In general, it is said that weed is a plant, which is not sown by the farmers or which is out of place. Weed is defined as the unwanted, undesirable plant, growing out of its proper place, which interferes with the utilization of natural resources, is prolific, persistent, competitive, harmful and even poisonous in nature and can grow in adverse climatic conditions.There are more than 30,000 species of weeds distributed world over, out of which 18,000 are noxious and cause serious losses. Around 250 species are causing serious economic losses. Weeds in orchards reduce crop yields by competing for moisture, nutrients, light and space. They also act as a host for insect pests and diseases. When they become large, they interfere with orchard operations as well as water bodies. There are some weeds, which are parasitic partially or completely on the host tree e.g. striga and loranthus, in mango.

Indian tea has a global reach being the second largest tea producer in the world. Indian tea is one of the finest in the world. Darjeeling tea is the first product to get a geographical indicator tag in India. 83 % of the tea produced in India is from Assam and West Bengal and 17% from the south Indian states of Kerala, Karnataka and Tamilnadu. Weeds are a major problem in tea gardens.

Weed flora

Drymaria cordata, Bidens pilosa,, Cynodon dactylon, Panicum repens, Celosia argentea, Ageratum conyzoides, Centella asiatica, Borreria hispida, Oxalis latifolia, Mikania micrantha, Paspalam conjugatum,

Rice is the primary food source for half of the Asian population. Nearly 2,000 million in this region obtain 60 to 70 per cent of their calories from rice and its products. Considering the importance of the crop, United Nations General Assembly declared 2004 as the “International Year of Rice” (IYR). In India, the crop covers one-fourth of the total cropped area. About half of the Indian population use rice as their staple food.

Rice based cropping systems are not only important for food security but also for maintaing an ecological balance. Low land rice fields conserve water and prevent runoff .They preserve the sustainability of the ecosystem.

Weed is a plant that is growing in the wrong place. Weeds have many mechanisms and characteristics that enable them to compete, having thick waxy cuticle leaves that can be resistant to some chemicals, fast reproduction methods, the ability to reseed in 6 week cycles and deep tap roots enabling the weed to survive in compacted dry ground conditions.

There are many reasons to control weeds in annuals/biennial and perennial ornamentals. Weeds compete with the plants by absorbing essential nutrients and water, or by blocking light or air circulation. Weeds dramatic reduce the growth of the plants. The greatest damage is often done when the weeds and ornamental plants are small. Weeds also interfere with harvesting by physically hindering. They lower flower quality further by harbouring insects, such as whiteflies, thrips mites, slugs, snails and/or diseases.

Growing under optimal conditions for the flower will reduce the ability of weeds to compete against the crop. Controlling humidity/ventilation, water, light, pH, nutrients and temperature all figure prominently in providing flower optimal conditions. A plant health strategy to greenhouse weed control contains three principal elements, prevention/sanitation, evaluation of water quality and using all controls available physical, cultural and chemical. Prevention and sanitation can include the use of mulches in orchidhouse weed control. Rice hulls, perlite, pumice, corn gluten meal bark, Penn Mulch - pelletized recycled paper and human hair have all been used for this purpose. Prevention also includes, eliminating air borne weed seeds from entering the greenhouse by screening vents and other openings and preventing perennial weeds from growing under foundations. A 1-3 meter weed free zone should be maintained immediately adjacent to the greenhouse.

INTRODUCTION

Control of weeds below economic threshold level in potato crop is a substantial component of crop management strategy for achieving optimum productivity. In our country, potatoes are raised eitherin assured irrigation or as rainfedcrop with comparatively heavy doses of fertilizers. Therefore, weedsarebound to become menaceduringactive cropgrowth period of this cropand theseundesired plants needs to be controlled in early stages of crop growth by adopting several techniques. Current scenario of crop production is different from past due to manyreasons. Farm holdings are becoming smaller day-by-day and majority of potato growers are small and marginal farmers. They have limitedcapacity for purchase of inputs and farm machines. They need economical, efficient and easier to adopt weed control technologies.Farm labour is also costly nowin many regions as they are migrating towards cities and industrial townships. This scenariobecomes more complex as weeds would be major challenge due to global warming, which is slowly changingclimatesof potato growingregions in India.Theconcern forenvironmentalissuesemphasizeuponadoptingsystems and integrated approach for managing weeds in such away that thesedo not reducethe potato and system productivity (CPRI, 2014).

Objectives

1. To study the weeds and its control.
2. To study the herbicides, their types, timing and methods of application.

Weed: A wild plant growing where it is not wanted and in competition with cultivated plants.

Or

Weed is such undesirable plant grown in association with crop which snatches major parts of nutrients, water, light, place and CO₂ available to the crop.

Due to tough competition crop suffers adversely and the production is reduced.

Most of us consider weeds to be the troublesome, competitive, aggressive, undesirable, unsightly elements of the plant world. We hate weeds since desirable plants cultivated by us are deprived of food, water, sunlight and space by these plants. They can easily colonize an area and thrive even under non-ideal conditions of growth and may affect human welfare adversely. It is perhaps due to this that the saying, when weeds win all the people lose, has come into existence.

The terminology committee of the Weed Society of America gives the simple definition of weed as a plant growing where it is not desired. King (1974) in his book Weeds of the World observed that ‘‘a plant classed as a weed in one region where it has few, if any, uses may when growing in another region, possess some very valuable uses, or in few cases may actually be cultivated’’. For instance, Bermuda grass (Cynodon dactylon) is a highly troublesome weed in crop fields, but in village pastures, it is a much sought for forage grass. Quack grass (Agropyron repens) is a very good soil binding grass on erodable non-crop lands but it is a serious weed when it infests crop fields and orchards. Campbell (1923) considered weeds as ‘honest, independent competitors for food materials in the struggle for existence’. He pointed out that the term, weed has developed in the minds of people not according to specific qualities or by a definite concept in the mind of man, but by human caprice, e.g., corn is a cultivated crop, hence, desirable plant in a corn field. However, if a corn plant grows in a Soya bean field, it is considered a weed by the Soyabean farmer. Sometimes, two persons may differ about the weedy nature of a plant at the same place and time, e.g., water hyacinth (Eichhornia crassipes) is a weed for fisherman but it is a plant of aesthetic value for a city dweller.

Thus, a corollary to the above definitions of weed is that weeds are those plants, which grow out of their place, interfere with the utilization of natural resources, prolific, persistent, resistant, competitive, harmful and even poisonous in nature and can grow under adverse conditions.

Weed management practices are evaluated for its efficiency in terms of effective control of weeds and economics of control measures through various indices under sole crop situation as well as intercrop situation.

6.1. Indices for Sole Crop Situation

The absolute effect of particular method or a chemical in reducing the weed competitions and increasing the crop productivity are measured effectively by various indices. The comparisons of weed control methods are usually based on the yield, weed population and weed dry matter from the control as well as treated plots.

With Judicious Use of Herbicides

Herbicides are the chemicals used for killing or suppressing the growth of weed plants from field / horticulture / plantation crops as well as non-cropped areas/ water bodies etc. The herbicide is said to be an ideal herbicide when it is very safe to the crop on which it is applied and on the other hand, it must control all associated weeds effectively. Also, ideal herbicides should leave no residual effects on the succeeding crop(s). Herbicides are of two types i.e.

1. Selective herbicides and
2. Non-selective herbicides.

A selective herbicide is that which is very safe to crop plants but unsafe to weed plants e.g. atrazine in maize, clodinafop in wheat etc. On the other hand, non-selective herbicides are those which kill all green plants including crop and weed plants which come in their contact e.g. paraquat and glufosinate ammonium.

Weed management in natural farming emphasizes natural, chemical-free methods that align with ecological principles. Instead of using herbicides or synthetic chemicals, natural farming promotes approaches that maintain biodiversity, improve soil health, and reduce weed pressure through various cultural, mechanical, and biological methods.
Here are key strategies for weed management in natural farming:
1. Mulching
Mulching is an agricultural and horticultural practice in which organic or inorganic materials are spread over the soil surface to protect and improve soil quality. In natural farming, mulching plays a key role by fostering a healthier ecosystem for plants without synthetic inputs.
Types of Mulch
Mulches are broadly categorized into organic and inorganic types:
• Organic mulch includes materials such as straw, leaves, grass clippings, crop residues, compost, wood chips, and sawdust. These materials decompose over time, enriching the soil with organic matter and nutrients.
• Inorganic mulch consists of materials like plastic sheeting, landscape fabric, and gravel. While these do not decompose, they effectively suppress weeds and retain moisture but do not improve soil fertility.

Weed

Definition: “Weed is an unwanted plant growing where it is not desired.” – Jethro Tull

Commonly noticed weed species in fruit orchard:

• There are more than 30,000 species of weeds distributed world over, out of which 18,000 are noxious and cause serious losses.
• Around 250 species are causing serious economic losses.
• Monocot weeds (Narrow leaf/Grasses): Cyprus, Cynodon, Poagrass, Rye grass, Quackgrass etc.
• Dicot weeds (Broad leaf weeds): Dandelion, Chenopodium spp., Parthenium, Solanum, Euphrobia spp., Ground ivy etc

Symbolic to its nomenclature, ’PULSE’ (P = people, U = umbrella, L = livestock, S = soil and E = energy) is a superb group of agricultural crops extending an energy umbrella to people (as a major source of dietary protein), livestock (as a green nutritious fodder and feed) and soil (as a builder and restorer of soil fertility through biological N₂ fixation). On account of these qualities, pulses have occupied a unique position in the Indian farming system. Crop diversification with greater inclusion of legumes is essential to alleviate declining factor productivity, input use efficiency and increasing cost of cultivation for realizing sustainable use of natural resources. Pulses are increasingly becoming a component of the intensive cropping systems as intercrop, substitute crop or catch crop. In upland situations, pulses play an important role as intercrops and ensure more income and efficient use of resources. While analyzing the reasons of low productivity of pulses in various parts of the country, it is observed that non availability of high yielding disease resistant varieties, cultivation on marginal and sub-marginal lands under deficit moisture and fertility and poor pest management are the major constraints in realizing optimum yield potential.

13.1 INTRODUCTION

Weed is defined as an unwanted plant growing at a place where it is not desired. Weeds are unwanted and undeserved plants that interfere with the utilization of the land and water resources and thus adversely affect crop production and human welfare. Thus, a plant out of its place or a plant growing where it is not desired at that time is a weed. Weed has no species, but name was suggested as a useless and harmful plant that persistently grows where it is quite unwanted. According to Jethro Tull, the father of Weed Science, weed is defined as the unwanted, undesirable plant, growing out of their proper place, which interfere with the utilization of natural resources, prolific, persistent, competitive, harmful and even poisonous in nature and can grow in adverse climatic conditions. Of the total losses caused by pests, weeds have a major share (30%). They reduce the crop yield and decrease the quality of produce and hence reduce the market value of the turnout. Weeds are a major problem to horticultural production as they take advantage of their initial slow growth rate. Weeds reduce crop yield, lower their quality, act as alternate host of many pests/diseases and also have allelopathic effects on crops. Weeds also interfere with vital farm operations like weeding, fertilizer application, herbicide application and harvesting. Both annual and perennial weeds are common in their actions reducing the productivity of fruit trees. Weeds also provide shelter to various pathogens by becoming an alternate or collateral host of invaded crops by a number of fungal, bacterial and viral diseases.

The worst weeds found in the world are Cyperus rotundus, Cynodon dactylon, Echinochloa crusgalli, Echinochloa colona, Eleusine indica, Sorghum halepense, Imperata cylinderica, Eichhornia crassipes, Portulaca oleracia, Chenopodium album, Digitaria sanguinalis, Convolvulus arvensis, Avena fatua, Amaranthus hybridus, Amaranthus spinosus, Cyperus esculentus, Paspalum cojugatum, Rottboelia exaltata (Rana and Rana, 2016). All of these weeds are found in India. It has been reported that about 36-42% losses may occur due to inadequate management of weeds in apple (El- Metwally and Hafez, 2007). Therefore, management of weeds in all agro-ecosystems is crucial to sustain our crop productivity and to ensure the food security to the rapidly increasing population.

Site-specific weed control technologies practiced in precision farming are defined as machinery or equipment embedded with technologies that detect weeds growing in a crop and take action to maximise the chances of successfully controlling them taking into account predefined factors such as economics.Some of the commercial hardware and software developed for precision agriculture practices comprise tools for weed mapping and control software that adapts spraying to local weed occurrence. However, few farmers have adopted sitespecific weed management, although several studies have shown that weed occurrence and density varies significantly within a farm or a field. Site-specific weed control techniques have gained interest in the precision farming community over the years. Managing weeds on a subfield level requires measuring the varying density of weeds within a field. Decision models aid in the selection and adjustment of the treatments, depending on the weed infestation. The weed control can be done either with herbicides or mechanically. A site-specific herbicide application technology can save large amounts of herbicides. Mechanical weed control techniques adapting to the weed situation in the field are applicable to a wide spectrum of crops.

A system for the discrimination of different weed species and crops from images is done which generates weed maps automatically. Models for the yield effect of weeds are developed and applied in on-farm-research experimental setups. Economic weed thresholds are derived and used for an herbicide application with a patch sprayer.Herbicide use has not eliminated weed problems in agriculture and the need for manual weed removal is still an issue within specialty crop systems, particularly during the first several weeks of crop emergence when competition for resources is greatest.

Precision agriculture is a powerful technology with potentially important applications to weed management. However, growers should remember good agronomic practices, including preventing weed infestations, managing herbicides wisely to prevent resistance, and minimizing environmental impact associated with weed management. Weeds, and methods used to control weeds, can have negative economic and environmental impacts. With precision agriculture, growers can take advantage of the patchy nature of weeds by targeting management efforts only where they are needed instead of wasting expensive and potentially hazardous inputs where weeds are not present. Weeds are patchy because weed spread, survival, and reproduction are variable within a field and over time. Weed patches stay in about the same place from year to year, even though weed density within a patch may vary

Weed

Weed in orchards reduce crop yields by competing for moisture, nutrients, light and space. They also harbour insect pests and diseases. When they become large they interfere with orchard operations. Some of weeds climb on the trees and shade the foliage. There are some weeds which are parasitic partially or completely on the host tree e.g. Striga and loranthes on mango.

Different crops are grown in a field. Any plant growing in a place where it is not desired competing with the main crops, has to be weeded out and such plants are called ‘weed’.

Effect of weed menace The weeds

Reduce crop yield and production efficiency. It competes with the main economical crop for space, water and nutrients.

Reduce crop quality.

Hamper intercultural operations.

Reduce crop quality.

Obstruct the flow of water in the irrigation channels.

Exert allelopathic effect on crops.

Harbour insect and pests, which affect the main crop of interest.

Increase the cost of production.

Abstract
Legumes are an excellent group of fertility restorer crops which can be grown either as sole crop or as a component crop in the cropping system. As they are tolerant to drought condition, they can be grown throughout the year. The yield of legume crop is largely depending on pest, diseases and weeds. Among these weeds plays a major role as the weed seed bank inside the soil influence the weed population in the cropping season. Hence it is important to manage the weed seed bank for better productivity of legumes. Though legumes are short duration and fast growing crops, the germination percentage of weed seed bank will determine the final yield of legumes. There are many strategies to which the weed seed bank can be controlled to tolerable level before which the weed seed bank present in the soil has to estimate. Annual weed seed bank can be minimized by killing the weeds before they set seeds, harvest weeds, crop rotation, cover crops, inter cropping and ensiling. Weed seed bank depletion can be done by tillage, tricking the weed seeds, conditioning weed seeds, soil solarisation and herbicide application. Thus integrating various technologies may help in effective controlling of weed seeds to tolerable level thereby enhancing the yield of leguminous crops.
Keywords: Estimation of weed seed bank, legumes, tillage, yield, weed seed bank

Shifts or changes in the abundance and types of weeds within agricultural systems are common. These shifts can occur for a number of reasons and may result from cultural, mechanical, or chemical weed management strategies. The right combination of weeds and relying too heavily on any one practice is often the most common cause. Some of the concepts associated with weed species shifts are discussed below.

A weed shift is the change in the composition or relative frequencies of weeds in a weed population (all individuals of a single species in a defined area) or community (all plant populations in a defined area) in response to natural or human-made environmental changes in an agricultural system. Weed shifts occur when weed management practices do not control an entire weed community or population. Some species or biotypes are killed by (or susceptible to) the weed management practice, others are not affected by the management practice (tolerant or resistant), and still others do not encounter the management practice (dormant at application).

Those species that are not controlled can grow, reproduce, and increase in the community; resulting in a weed shift. Any cultural, physiological, biological, or chemical practice that modifies the growing environment without controlling all species equally can result in a weed shift. Weed shift may be due to introduction of new species or change in relative proportion of members of the existing community. Latter is the most common.

A. Species shift: Change in density of one or more species in field

B. Biotype shift: Change in density of biotypes within a species. These shifts often found noticed since biotypes typically are similar in appearance. Herbicide resistantbiotypes are the most frequently studied.

Weed monitoring is conducted to detect significant weed problems, rank them for relative severity and sort them by management type annuals, biennials, perennials, grasses and broadleaves. Weed monitoring provides information to tailor weed management efforts that reduce the impact of the weeds. The primary objective of weed survey and mapping is to accurately identify and delineate land with populations of unwanted plants. These surveys are conducted so that scientists and managers can predict those areas potentially subject to weed invasion; understand the biology of the invasion process and determine means by which weeds spread; develop, implement and evaluate weed management plans; assess the economic impact of weed invasion and increase public awareness, education and weed management efforts. Weed survey information is collected and compiled into maps showing the distribution and severity of infestation. Weed monitoring involves repetitive surveys to track weed populations over time. A standardized system of weed surveying and mapping is necessary to provide consistently reliable information that can be compared from year to year. Further, a standardized system allows weed survey data to be incorporated into a state wide weed survey database for the production of state wide noxious weed maps.

5.1 Weeding and Interculture Equipment

The aim of weeding and intercultivation operation is to provide best opportunity to crop to establish and grow vigorously up to time of maturity. The main objectives of weed control are to improve the soil conditions by reducing evaporation from the soil surface, improve infiltration of rain or surface water, and reduce runoff to maintain ridges or beds on which the crop is grown and to reduce competition of weeds for light, nutrients and water. Mechanical methods of weed control are simple and easily understood by farmers. The tools and implements for mechanical weed control are mostly manual and animal operated. Manual method is most effective but is slow. It is popular in regions where labour wages are low and labour is easily available during the season. The additional cost of weeding using implements is comparatively less than the gains due to extra yields obtained. First weeding operation is mostly done between and along the rows. Remaining operations are done mostly between the rows. Hand hoes are generally used for removing weeds between plants in a row.

19.1. Need for weeding

Weeding is the critical operation to be carried out to obtain a good crop. Weeds are plants which grow in places where they are not wanted. They grow in the fields competing with crops for water, soil nutrients, light and space and thus reduce crop yields. They also harbor insect pests and micro-organisms. Certain weeds release the inhibitors or poisonous substances into the soil which are harmful to plants, human beings and livessecks. They increase the expenditure on labour and equipment, render harvesting difficult and reduce the quality and marketability of agricultural produce. When grown in water channels, they block and or reduce the flow of water.

The weed seeds germinate earlier and grow faster than the crop plant. This phenomenon is more pronounced when coupled with favourable environment like fine soil tilth and the soil receiving adequate water and fertilizers. Weeds flower earlier and produce seeds profusely ahead of the crop. So, these seeds get mixed up with the harvested crop and are distributed to the next season or transported to other places along with the harvested produce.

An agricultural weeder is a tool designed to remove weeds from fields or gardens. It can be used manually or attached to machinery like tillers and power weeders. Weeding is necessary to eliminate unwanted plants that compete with crops, ensuring better growth and profitability. Effective weed management is crucial in crop production, as weeds can reduce yields by stealing nutrients and attracting harmful pests. In recent years, research has focused on non-chemical methods and environmentally friendly alternatives to herbicides for weed control. Mechanical weeding is often the most cost-effective solution. Tools like rotary weeders, mechanical hand weeders, and wetland weeders are generally effective, with wetland versions gaining popularity due to their ability to function in shallow water. These tools uproot weeds and bury them in the mud through their pull-and-push action, making them both safe and eco-friendly. Weeding should be done at least three times during a growing season, with early weeding being the most effective for completely eliminating young weeds.
FUNCTIONS OF WEEDING EQUIPMENT
Secondary tillage equipment is often used for weed management. Weeders help control weeds between planted crops or before sowing. Some weeding machines use mechanical methods to remove unwanted plants without the need for chemicals.
Usage Instructions
• Early weeding is essential: Perform the weeding within 20 days after sowing.
• Delayed weeding can lead to competition between paddy and weeds, harming the crop.
• Move the weeding machine back and forth between rows.
• Conduct a second round of weeding after 15 days, and if possible, a third.

Origin of weeds : Weeds originated together with crop plants. They have been there since the man started cultivating crops about 10,000 BC. Man during his stage of development, explored certain crop plant to suit his own taste and fancy and cultivated them as ‘crops’. The unexplored / unwanted / troublesome plants which are interfering with his activities are considered as weeds. About 30,000 plants species have been identified as definite weeds in the World. Which are infesting crop lands, water bodies, gardens, orchards, road sides, railway lines, irrigation channels etc.

Plants are differentiated into

a) Crops: Which meet the needs of human being.

b) Weeds: Which compete or interfere in human affairs.

Jethrotull is the first person to use the word weed.

3.1. Cereals and millets

3.1.1. Rice

1. Major weeds

Grasses

Weeds are the plants growing where and when they are not desired. They compete with crops for soil moisture, nutrients, solar radiation and space, and thus reduce crop yields. Weeds also act as alternate hosts that harbour insect pests and diseases and other microorganisms. Some weeds release poisonous substances into the soil which may be harmful to crop plants, human and livestock. Weeds reduce the quality of marketable produce and render harvesting difficult, leading to increased expenditure on labours, equipment and chemicals for their removal.

Classification of weeds

A. Based on life cycle

Annuals-Complete their life cycle in a year or in a single growing season. Based on the season they may be summer annuals and winter annuals.
Summer annual e.g, Echinochloa crusgalli

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

A. Answer the following questions:

1.    What is proximate analysis?

Ans: Proximate analysisis a systemforapproximatingthenutritive valueof a feedstuff without actually usingit in a feedingtrial.

2.    Why proximate analysis is called Weende analysis?

Ans: In 1865, two scientists namely Wilhelm Henneberg and FriedrichStohmanndeviseda methodcalledWeende analysis/ proximate analysis at Weende Experiment Station, near the University of Goettingen, Germany. Hence, it is called ‘Weende Analysis’.

3.    Write the six proximate principles?

Ans: Water (moisture), ether extract (crude fat), crude fibre, total ash, crude protein and nitrogen free extract (NFE).

4.    Why ether extract is also called as crude fat?

Ans: As it is composed of true fats (glycerides of fattyacids) along with other substances like hydrocarbons, free fatty acids, fat solublevitamins,pigmentslike carotene & chlorophyll,waxes, sterols,lecithin(phospholipids), alkali substances,volatile oils and resins.

5.    What is NFE?

Introduction

In a research laboratory, we frequently need weigh chemicals and prepare different solutions of varying strength, as per the requirements. Accuracy in weighing and preparation of solution, with respect to weight/volume and strength, determines the success of experiment. In turn, the accuracy depends on weighing of solid chemical and/or measuring the volume of liquid chemical/making up the volume. In this Chapter, weighing of chemicals using appropriate weighing balance, preparation of solutions of different strength, their dilution, and precautions while preparing will be discuss in brief.

Weighing of Chemical

The primary method to determine the amount of chemicals to be used is weighing the chemical by using a balance.

In general, there are two types of balances to weigh chemicals in a laboratory:

1. Standard laboratory balance

2. Analytical balance

Standard Laboratory Balance

Generally, a standard laboratory balance is used for weighing a chemical when an error of ±0.02 g is acceptable. It is also used for pre-weighing, where approximate mass needs to be determined. Precise mass of the chemical is then determined using an analytical balance. Following are the steps in using a weighing balance in a laboratory.