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Herbicides have received wide acceptance from farmers mainly due to ease of application and effectiveness. After application, herbicide molecules should penetrate plant tissue and get translocated to the target site. Once they reach the target protein they bind to them and disturb metabolic processes in plants by disrupting biosynthetic pathways and damaging cell structures by generating cytotoxic molecules that ultimately kill the plants. In this, the first step is penetration of herbicide into the plant system.

Herbicide Application

Generally, herbicides are applied in the form of solution or granules. Of the two, spraying solutions of herbicides formulated as wettable powders, soluble powders and emulsifiable and solution concentrates is more common. When herbicides are formulated as granular or encapsulated materials, they are applied by hand or with the help of a granular applicator.

A large number of herbicides are currently available in the market hence selection of suitable herbicide needs judicious understanding of the product and the requirement. When large number of chemical options are available it can make the process of selection a bit confusing. So it is important to know the crops in which a herbicide can be used, the weeds it will control, the appropriate rate, adjuvants included in the formulation. The different uses of the chemical and the different situations for which it will be useful. In addition to these it is important to understand the mode of action of the herbicide and also the mechanism of action of the chemical.

Herbicide History and Development

Common salt, ash, smelter waste, and like cheap materials have been used for centuries to control weeds on roadsides, fence rows, and pathways. But Chemical weed killing was born in 1896 when Bonnet, a French grape grower, observed that the Bordeaux mixture which he used against downy mildew of grape turned the leaves of Sinapis arvensis (a weed) black. Soon it was found that copper sulphate present in the Bordeaux mixture was responsible for its weed killing effect. Further tests in France, Germany, and U.S.A. established that copper sulphate could indeed be used for selective control of broadleaf weeds in small grains; wheat, barley, and oat. Between 1896 and 1908, several other inorganic salts, as also sulphuric acid, were found selective to small grain cereals. Of these, in Europe, a 6 to 10 per cent solution of sulphuric acid continued for considerable time as a satisfactory herbicide for broadleaf weed control in cereals, but it corroded the containers and sprayers. In the U.S.A., salts like sodium chlorate, carbon bisulphide, sodium arsenite, kainite, and calcium cyanamide were developed for non-selective eradication of perennial weeds, particularly, Convolvulus arvensis ‘field bind weed’ and Cirsium arvense ‘Canada thistle‘. In Hawaii, sodium arsenite solution was found highly effective for weed control in sugarcane plantations. Between 1930 and 1940, some boron compounds, thiocyanates, dinitro phenols (DNC and DNBP), ammonium sulphate, and certain mineral salts were developed in the west for selective and non-selective weed control. DNC and DNBP wereused extensively in Europe in small grains for broadleaf weed control, even though these chemicals dyed the hands and clothes of the users to yellow colour, almost permanently. Further milestones in weed control were introduction of organic chemical, 2-methyl-4, 6-dinitrophenoll (DMOC), in 1932 and discovery of hormone type selective weed killers. Selective residual chemicals such as substituted phenyl ureas and triazines, and non-residual chemicals diquat and paraquat are more recent discoveries.

The discovery of the herbicidal activity of 2, 4-D (2, 4-dichlorophenoxyacetic acid) first synthesized in 1941, triggered the development of modern herbicide technology. 2, 4-D proved to be an outstanding herbicide.

Herbicide Mixtures

A mixture of two or more herbicides could be more effective for controlling different weed species. In horticultural and plantation crops, weed free situation is needed during the entire year over several years. In such situations, herbicides are to be rotated to take care of all the species of weeds. A mixture of herbicides, due to chemical reaction, may enhance or reduce the efûciency of one or more compounds. Hence, knowledge of herbicides interactions is essential for efûcient use of herbicides in weed control.

Persistence of Herbicide in Soils

Most of the herbicides are applied to soil as pre-emergence for weed control under different situations. For effective weed control, herbicides must remain in soil in active and available form until their purpose is served. Larger persistence poses hazard to subsequent land use and is undesirable. The length of time that an herbicide remains active in the soil is called persistence or soil residual life. The quantity of herbicide that remains in the soil after its mission is accomplished is referred as residue. The term residue infers the continued presence of herbicide in the soil in very small quantities even though it may not be present in herbicidal quantities or available for plant absorption. Herbicide residues in soils are undesirable mainly because they may

Injure sensitive crops in a cropping system,

Be absorbed by succeeding crops and residues accumulated in unlawful amounts in the produce,

Result in building up of herbicide residues following repeated treatments that exceed their rate of dissipation, and

Inhibit growth of soil micro-organisms.

Knowledge of persistence and carry over residual effect of herbicides is essential to use them safely and effectively. Persistence of herbicides in soils pose hazard when

Highly persistence herbicides are used,

Crop failure necessitates replanting,

A susceptible crop follows a short term crop which received a persistence herbicide, and

Decomposition of the applied herbicide proceeds very slow.

Resistance

The intensive and continuous use of herbicides over the last five decades has resulted in the development and evolution of weeds resistant to the normally phytotoxic chemicals. Although herbicide resistance was reported as early as 1957 against 2, 4-D from Hawaii the first confirmed report of herbicide resistance was against triazine herbicide in common groundsel (Senecio vulgaris) was reported in l968 from U.S.A. Over the years, more than 150 weed species have been identified as having developed biotypes resistant to at least one or more herbicide classes. Resistance to at least 15 classes of herbicides have been noted. Moreover, the area of land infested with resistant weeds is increasing rapidly. Reports of evolution of newly resistant biotypes continue to emanate from all over the world, including developing countries, e.g., India, where extensive use of herbicides in grain crops began only in the late 1970s. These reports indicate that herbicide resistance problems are accelerating and, consequently, management of weeds is becoming increasingly more difficult and complex.

The phenomenon of herbicide resistance in plants, especially in weeds, is analogous to the evolution of changes that arise in insects and pathogens in response to the continuous use of insecticides and fungicides. Herbicide resistance is the result of selection for traits that allow weed species to survive specific herbicide usage, which would otherwise cause mortality. Herbicide resistance contributes a trait of resistance within the plant species to a herbicide and resistant weeds are those plant species that express the genetic variation required to evolve mechanisms to escape control. Like other crop pests (insects, pathogens, etc.) with reference to pesticides (insecticides, fungicides, etc.), herbicide-resistant weeds are the result of intensive selection pressure in weed populations.

Generally, resistance is defined as the ability of a plant species to withstand the phytotoxicity of a chemical. This is the trait normally found in crop plants, as against weeds, thus forming the basis for herbicide selectivity. Crop resistance to a herbicide is often different from the one that exists in the phenomenon of herbicide resistance in weeds.

Herbicide resistance in the context of weeds is defined as a characteristic of the weed species to withstand a herbicide dosage substantially higher than the wild type of the same plant species can withstand. It is the inherent or acquired ability to withstand the dosage of herbicide normally used for satisfactory weed control. Resistant weed populations are unharmed by a concentration of herbicide that completely kills all unselected populations. This herbicide concentration is the one that in field practice produces an effective kill.

Herbicide susceptibility represents the other end of the scale, encompassing natural variability in sensitivity to herbicides within the unselected populations. Tolerance, on the other hand, indicates reduced susceptibility (or conversely enhanced resistance) which may sometimes result from selection by herbicides. It is a response rather less than 100% survival accompanied by zero reduction in growth at herbicide concentrations, which normally give 100% Kill of susceptible biotypes. Tolerance may also be considered the natural or normal variability of response to-herbicides that exists within a species and can easily and quickly evolve.

1. Herbicide –herbicide interaction

Herbicides cause some effects as follow:

(i) Synergistic: Synergism is defined as the cooperative action of different chemicals in a mixture such that the total effect is greater than the sum of the independent effects (Green et al., 1997). In relation to herbicides, the total  induced by an herbicide mixture is greater than the sum of the responses by each herbicide alone (Anderson, 1996). Synergistic  is often used to describe the effect of drugs working together — where one drug increases the other’s effectiveness. Synergy is the interaction of multiple elements in a system to produce an effect different from or greater than the sum of their individual effects.

Herbicides are chemical substances that are capable of either killing or injuring plants and so used for elimination of unwanted plants. In Latin, the term ‘herba' means plant and ‘caedere’ means to kill. There are many reasons for the increased use of chemicals for weed control. Shortage and high cost of agricultural labour prevent economic control of weeds by manual and mechanical means. Benefits offered by herbicides include efficient weed control, higher crop yield, better soil, water and energy conservation and higher income.

SYNOPSIS

Flavor is the sensory impression of a food or other substance, and is determined mainly by the chemical senses of taste and smell. The flavor of the food, as such, can be altered with natural or artificial flavorings which affect these senses. Smell is the main determinant of a food item’s flavor. While the taste of food is limited to sweet, sour, bitter, salty, umami (savory), pungent or piquant, and metallic – the seven basic tastes – the smells of a food are potentially limitless.

Introduction

Apart from the general way of flood-flushing practiced at different sites of Indus Civilization, mention may be made of the following practices particularly undertaken in Sind. This is evident in the writings of inscriptions on seals from Mohenjo-Daro which state: ‘Two canals were constructed in the month of Kudam (Aquarius) and Mina (pisces). Another seal records that it took ‘thirteen months to construct a canal’. These canals were cut at low gradient and waters were allowed to merge ultimately into low ground in a direction oblique to the river so as to secure a great fall as possible. This fall varied from a foot to a few inches in a mile. They were up to hundred feet wide and about a dozen feet deep, not enough to draw off from the river except in flood. These were natural streams and probably seasonal. The perennial canals of the Indus system were cut to an extra depth and could receive water even when the main river was low, but their real purpose seems to increase the discharge during inundation.

Irrigation system

Irrigation system was consisting of lifting of water by water-wheel and by means of Shaduf from adjoining water sources. There was also provision of tank irrigation. Rice cultivation shows necessary moisture of soil probably retained by now using contour bunding for locking up monsoon rain-waters by tank-irrigation. Rainfall under vernal equinox or winter solstice has not been given much importance in the context of agriculture. Artificial rain making agents was the twin stars, Asvinis and Dadhici, described as horse headed sign. The exact time of their appearance cannot be ascertained definitely. Their association with cool season can be surmised from their name Dasra implying the same as referred to in the text of Panini. Moreover, their attributes as sender of hima (cold or snowfall) after the scorching heat of summer associates them as belonging to vernal equinox. That they appeared at the time of sun’s movement to another house, is explicitly mentioned in the Rigveda. It is a fact which shows the rising of these stars at the junction of two solstices, summer and winter. The Rigveda in one place described them as associated with winter solstice. They were found to have been associated with three kinds of watery discharges, viz. rain (vristi), dew (madhu) and snow (hima).

Preamble

In India, agriculture plays an important role as it accounts for about 18% of the GDP and supports nearly 58% of the total working population for employment. Food grain production increased significantly from a low level of 50 million Tons during 1950-51 to a record of 230.7 million Tons in 2007-08. The demand for food is growing rapidly due to increasing population and rising income levels, hence we need to produce about 320 million Tons of foodgrains by the year 2025. It implies more pressure on our exhisting land, soil and water resources which are already in short supply, degraded, fragile and this similar situation is being faced by mainly developing countries today. Plant parasitic nematodes are of great economic significance. Since most of them live in the soil hence represent one of the most difficult pest problems in terms of identification, demonstration and management.

10.1. Heterosis

Occurrence of a genetically superior offspring from mixing the genes of its parents.

Superiority of F₁ hybrids over its both parents in terms of yield and vigour.

8.1. Biofloc aquaculture

Among the innovations in the field of aquaculture, biofloc technology (BFT) has attracted great attention due to its ability to foster the goals of sustainable aquaculture (Khanjani et al., 2022a). If implemented correctly, BFT capitalizes on the existing organisms in water to significantly reduce water use and environmental impact and increase biosafety at farms (Avnimelech, 2012).

Besides diversities and advantages in hills, the communities sustain largely on subsistence farming due to following constraints A.Natural constraints in hills There are large number of Inherent limitations in hill agriculture like, remote areas, vulnerability, marginality , eroded soil and short growing seasons. These Inherent constraints can be judged by the use of unsustainability indicators of hill agriculture which further showed increased in soil erosion rates from sloping farmlands , leaving of agricultural land due to decreasing soil fertility, appearance of stones and rocks on the cultivated lands, reduction in forest and grazing areas and more emphasis on monocropping that widened the cycle of inadequate food production and lead to food insecurity and increasing unemployment and frustration (Table 3) (Shrestha, 1992). These natural constraints are.

Pulses occupy an important place in hill agriculture. They are complementary to cereals in production and consumption being an important source of protein and nitrogen fixing ability which helps in improving soil health. Thus, cultivation of pulses has a positive relationship with our environment, human health and food security. Pulses produced in the hills are famous for their cooking quality, taste and flavour.
 
Himachal Pradesh has emerged as a model hill state in which agriculture is a dominant economic activity and major source of employment and income to the rural people. Being a hilly state, agriculture is practiced on about 10% of the geographical area. Out of which nearly 80% is rainfed. During the last three decades, the farming scenario has changed significantly. The area under fruits, vegetables and cereals has increased tremendously at the cost of pulses and oilseeds. There is, therefore, an urgent need to reverse this trend as pulse cultivation will not only increase soil health but save precious foreign exchange.

With the sharp development of urban and industrial growth, the area under agriculture is declining year by year. On the other hand, human and animal population is increasing at a very fast rate. So, to meet the growing demand of food and fodders, a vertical increase in yield is required. Crop productivity per unit area can be enhanced with the manipulations of some agronomist practices such as sowing the crops at appropriate time, selection of suitable field for raising a crop, adoption of best planting techniques, use of appropriate seed rates, adoption of proper irrigation schedule, proper and need based application of fertilizers, adoption of zero till technology, green manuring, mulching, addition of well decomposed farm yard manure, timely and proper weed management, selection of recommended crops and crop varieties, proper control of insects and pests, adoption of marketing tips etc.

INTRODUCTION

In biology, fertility is de?ned as capacity to produce off-springs; however, in Soil Science a ?ne difference is made between a fertile and a productive soil. Soil Productivity is the ability of a soil to produce a crop using the entire spectrum of its physical, chemical and biological attributes, while Soil Fertility refers to the capacity of a soil to supply all essential plant nutrients in the desired amounts. Thus, soil fertility management is basically the nutrient management. To put it in simple words, a productive soil is always fertile, while a fertile soil may not be productive for a variety of factors, such as lack of adequate moisture in drier regions or lack of adequate air due to water-logging for most upland crops. Of late, a term ‘ Soil Health’ has been introduced. Soil Health is an assemblage of chemical, physical and biological parameters that closely relate to native or acquired production capacity and sustenance of ecologically important regulatory role (Katyal et al., 2016). It is measured against prede?ned parameters of soil’s status of fertility, compact ability, erodibility and biology. This again tends to relate soil fertility to nutrient content, availability and management.

Introduction

Farming system is complicated inter-related with soil, plants, animals, implements, power, labour, capital and alternative inputs controlled partly by farming families and influenced to varied degrees by political, economic, institutional and social forces that operate at several levels. The farm is viewed during a holistic manner. The farmers are subjected to several socio-economic, biophysical, institutional, body and technological constraints. Farming system conceptually may be a set of components or parts that are reticulate that act amongst themselves. At the centre of the interaction is that the farmer exercise management and selection concerning the sort and results of interaction. It’s the human setting that gives ample condition for development and utilization of a specific system. A farming system clearly is incredibly complicated system. Therefore, any agricultural technology compatible to a specific agroecological state of affairs and socio-economic environment might not be adopted by alternative farmers. Unless each natural and human environment is thought-about, agricultural analysis won’t end in relevant agricultural technology. The income from cropping alone in tiny and marginal farms is hardly ample to sustain the farmers’ family. With the decline in farm size (0.15 ha) because of explosion of population, it’d be more and more tough to provide enough food for the family by the tip of the century. Therefore, the farmer, to be assured of an everyday income for a good living (above the poverty line), a considered mixture of anybody or additional of those enterprises with agronomic crops ought to complement the farm income and facilitate in usage the farm residue/waste. The choice of enterprises should be supported the cardinal principle of minimizing the competition and maximizing the complementarily between the enterprises.