eChapters

Seabuckthorn is an important plant of India and other regions of the world, where it is being widely used as an orchard plant for fruit production and in the ecological rehabilitation of waste lands and eroded areas. In India, seabuckthorn has been developed into a major environmental resource. Many areas that are virtually treeless and losses huge soil due to erosion, seabuckthorn has turned out to be useful because it withstands severe weather and grows huge root systems in poor soil. This is the reason that seabuckthorn is grown in Ladakh region of Jammu & Kashmir which is known as cold desert. In Mongolia several wild animal species have found a habitat in the sea buckthorn forest, including pheasant, hare and fox.

In Garhwal Himalayas, various economically important tree species including Seabuckthorn (Hippophae salicipholia) have been over exploited for fuel, fodder and seed, therefore presently exist only in some patches here and there. Due to excessive lopping for fodder, the seed are generally not available for natural regeneration. Hence, there is a need of developing technique for mass multiplication of these multipurpose tree species for afforestation and general well being of the rural people.

Originating in the New World tropics, peppers have become ubiquitous culinary essential now grown not only in warm climates but in temperate areas as well. They include both sweet and hot chilli varieties. Botanically chilli belongs to the genus Capsicum. The North East region has its own unique combination of living species, habitats and ecosystems, which together make up its diversity rich resource. While speaking strictly about plant diversity, two regions of the country are termed as hot spots. These are – Western Ghats and the North Eastern hill regions. The King’s chilli is an inter-specific hybrid cultivated in the Nagaland and Assam region of northeastern India and parts of neighboring Bangladesh. In 2007, Guinness World Records certified the Bhut Jolokia as the world’s hottest chili pepper, 400 times hotter than Tabasco sauce. From time immemorial, traditionally the Bhut jolokia is been cultivated and consumed by the local people in North eastern states like Assam, Nagaland, Manipur and Mizoram. A good amount of genetic variability exists in the landraces of the crop in respect of Pod size, shape, and colour etc.

In recent years, the King’s chilli (Bhut jolokia) is gaining importance in the scientific community as it was reported as the hottest chilli. Though Bhoot jolokia or Naga chilli was cultivated from time immemorial, but nobody really bothered to compare its heat with other record setters. The field of King’s chilli is still in a growing stage and it components and their beneficial uses are still to be exploited fully. Very little research towards the scientific cultivation of this potential crop was accomplished in recent years and until now no standard scientific package of practice is available for the cultivation of the crop.

There is tremendous scope for utilizing the available genetic variability of the crop in a well-planned plant breeding programme for further development of elite genotypes in this crop. Development of proper and efficient post harvest mechanism and also of different value added products of King’s chilli shall generate a great potential for earning revenue in the national as well as international markets.

The vegetable crops like knol-khol, Broccoli and kale belong to the genus brassica of the cruciferae family. They are essentially cold weather, hardy crops and thrive best in cool moist season. These crops, if grown under warm conditions, the produce become pungent due to development of glucocide called sinigrin containing sulphur. According to Chowdary (1967), the crops of this group have developed from wild cliff cabbage, also known as cole wrots, from which the name cole has been given. Their taste founds to be more sweat in hills due to low temperature and constitute at top in the list of preference vegetables for people all over India.

This chapter attempts to describe the cultivation of these three cole crops, exclusively grown in hills of India.

Knol-Khol

Knol-khol (Brassica oleracea var. gonylodes) is a well known green–leafy vegetable, which is consumed with leaves and knobs. It is popular among Kashmiri people and the people of hilly areas. Its cultivation is confined to Jammu and Kashmir, Himachal Pardesh, West Bengal, Uttranchal and Punjab. Due to its year round demand and conducive agro-climate available in J&K, it can be cultivated round the year. The crop is of short duration and be grown three to four times a year. Thus it gives very high productivity per unit area.

The present study was undertaken to study the trends of area, production and productivity of major fruit crops in the Himachal Pradesh state. The study was based on secondary data from 1974-75 to 2010-11. The data was collected from several government publications and website. To analyze the trend of area, production and productivity of major fruit crops in the Himachal Pradesh state, the linear, quadratic and exponential functional forms were used. To fit the trend, quadratic functional form was used due to its higher R² value as compared to other two forms. Besides these, compound growth rate, coefficient of variation and instability index was also estimated. The effects of area, productivity and their interaction towards increasing production were also estimated in the present study. The growing of major fruit crops was not risky in the Himachal Pradesh state as revealed by the lower coefficient of variation. The coefficients of variation (CV) of area, production and productivity of major fruit crops were less than 100.13 per cent. The instability indices for area, production and productivity for major fruit crops in the Himachal Pradesh state were positive and thereby indicating less risk for growing major fruit crops in the state. The increase in production is due to increase in area as well as interaction of area and productivity of fruit crops in the state. This may be due to the adoption of high yield variety seed of major fruit crops and adoption of improved methods by the farming community during last decade.

As long ago as 1881 Charles Darwin wrote: “It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organized creatures”.

The soil of the food bowl states of our country viz. Punjab, Haryana, Western Uttar Pradesh and plains of Uttarakhand have become deficient in organic matter, macro and micro nutrients and trace elements. Now soil has become non living due to death of earthworms and beneficial micro organism. Farmers are using mainly nitrogen and phosphorus in crop production. However 17 elements are essential for plants nutrition for growing of crops. To get maximum yield and output from the crop plants, a vicious cycle of using the maximum amount of chemical amendments is going on. In the chemical amendments, indiscriminate use of both fertilizers and pesticides are included. Due to this indiscriminate use of these fertilizers and pesticides, our environment is being polluted and living organisms on this planet are experiencing the deleterious effects of all this on their health. These chemicals also exert their influence on soil flora and fauna, therefore the balance of macro and micronutrients release in soil is being disturbed and as a consequence soil fertility and productivity is decreasing day by day. Therefore, for sustainable agriculture healthy farming is fast becoming an urgent necessity.

The problems being faced are the destruction of the soil health leading to reduction in production potential, failure of pest control strategies due to the development of pesticide resistance, biomagnification of pesticides such as reside problems in food and water. The food grain produced and assessed with attributes of fertilizers, the fertilizer efficiency seems to be decreasing. In 1970-71 it was 17.1%, declined in 1980-81 to 10.3% and in 1988-89 reached to 8.1%. Now a day, farmers are not properly using organic, green and compost manures in crop husbandry. Soil fertility and ground water level has been declining very fast by adopting intensive farming. If soil health of any country has been depleted, then the food grain production will also tend to decrease.

Organic farming is the form of agriculture that relies on techniques such as crop rotation, green manure, compost and biological pest control. Organic farming uses fertilizers and pesticides but excludes or strictly limits the use of manufactured (synthetic) fertilizers, pesticides (which include herbicides, insecticides and fungicides), plant growth regulators such as hormones, livestock antibiotics, food additives, genetically modified organisms, human sewage sludge, and nano materials.

There is a need to look for new means to check this menace. Chemical fertilizers are necessary to feed the ever increasing population of the nation but this needs to be supplemented with the organic manures. But organic manures are not available in sufficient quantity. Besides, they alone cannot meet the nutritional requirement of the crops and have to be applied alongwith the chemical fertilizers. Experimental results have shown that if organic fertilizers are applied then chemical use can be brought down to half. This will lead to favourable impact on the soil ecology besides saving large amounts that are being pumped to subsidize the chemical fertilizers.

Organic agriculture is picking up in some parts of our nation and it can generate viable farming option to small and marginal farmers. But short supply of the organic inputs is emerging as one of the major bottlenecks. Vermicomposting of city wastes and farm wastes can generate substantial volume of the organic fertilizer for use in our fields, thereby, helping us to overcome major hurdle in taking up organic agriculture production. This chapter attempts to identify the find out the ways and benefits of practicing organic farming and determines the economics of Vermicomposting technology.

The North Eastern Hill Region is the most suitable area of India for organic agricultural farming because of its numerous advantages. This region is said to be, by and large, organic by default or the farmers of this region are de facto organic producers. Truly, the farmers of this region are using very minimal or not even minimal amount of inorganic inputs like fertilizer and pesticides. Almost in all the seven states of this region, farmers are practicing traditional agriculture for thousands of years. Recently, only pockets of the region, the use of inorganic inputs have been started but the level of use is almost negligible. This low chemical input use (inorganic input) is the biggest strength in term of the possibility of organic agriculture in this hilly region. The conversion period of organic from inorganic agriculture will be much lower and easier in this region as compared to other parts of the country. Further, the conversion process will be much easier due to the readily available huge amount of forest biomass and the residues of diverse livestock population. Moreover, experimental results show that during the transition period, the farmers face the problem of yield losses, but in NE India it was observed that yield loss was minimum, sometimes nil, because farmers of this region are using very low level of inorganic inputs. Additionally, the organic products usually fetch higher prices, nearly 20-25 per cent premium as compared to the conventional products, which, may compensate the problem of yield losses during early period of conversion and thereby increase the level of income.

North-Eastern Hill Region is suitable for growing a number of high value crops and following good agricultural practices for cultivation of these crops are likely to increase farm income substantially. Enabling the state to follow systematic organic farm practices is likely to make the farming profession more remunerative. Present socio economic study indicated that the organic farm practices might be quite favourable particularly for few crops like pineapple, turmeric, ginger and cashew, which have readymade potential.

Medziphema rural development block is known for producing sweetest pineapple in Nagaland. A few years earlier, farmers predominantly practised indigenous method of pineapple cultivation where productivity was less. Under horticulture technology mission, farmers have been trained to grow pineapple scientifically. Therefore, a study was conducted to know the scientific orientation of pineapple growing farmers in Medziphema rural development block of Nagaland. Sample pineapple growing farmers were selected as respondents from three purposively selected villages under Medziphema rural development block. Respondents were selected following random sampling procedure. A structured and pretested interview schedule was used for collection of primary data from the respondents. Data analysis was done using SAS software. Findings of the study revealed that, majority of the pineapple growing farmers possessed medium level of scientific orientation, followed by high and low level of scientific orientation. The variable ‘scientific orientation’ was significant and positively associated with the ‘entrepreneurial behaviour’ of the pineapple growers and it was found as an important predictor variable influencing the entrepreneurial behaviour of the pineapple growers. It was inferred from the study that off late, farmers are realising the importance and benefits of growing pineapple scientifically. Scientific orientation can promote the pineapple based entrepreneurial activities which can bring about the socio economic development of the rural people.

Animal Husbandry is a major activity in hilly areas and women contributed the most in maintaining this enterprise. It is of immense importance to conduct study for alleviating drudgery of farm women in hilly areas. Since women’s contribution in animal husbandry is significant to our economy, their technological empowerment is equally important and needs to be given high priority.

This chapter covers a study of a project conducted in Udaipur district of Rajasthan. The concerted efforts made under this project through skill training, field demonstration, constant technical support and motivation resulted in acquisition of knowledge and skills in handling various drudgery reducing technologies in animal husbandry. Technological intervention has made farm women aware of new technologies available to assist them in performing the tasks. As a result there is a change in the practices of women and they have begun to adopt new technologies to improve their work efficiency in animal husbandry. By the use of technologies, there is considerable reduction in the drudgery of farmwomen. Equipment like rake, shovel, and wheel barrow and chaff cutter has not only decreased time and energy consumption but have improved work efficiency in terms of output.

Introduction

Livestock development has always been a major concern in the Indian economy along with agriculture. Animal husbandry and Dairy development play a prominent role in the rural economy in supplementing the income of rural household particularly, the landless, small and marginal farmers. It also provides subsidiary occupation in semi-urban areas and more so for people living in hilly, tribal and drought prone areas where crop output may not sustain the family. Animal husbandry output constitutes about 30 percent of the country’s agricultural output. In recent years, animal husbandry has become more indispensable for human kind because of increasing pressure on cultivable land owing to the population explosion.

The Himalayan region extends all along the Northern boundary of India. It experiences harsh environmental conditions, coupled with unfavourable climate, poor physical capacity of soil and threaten habitat. However, low and mid altitude areas provide environment ranging from sub tropical to temperate, where plant life thrives. The diverse eco-habitat of Himalayan region hosts a wide range of plant diversity as well as crop diversity on which native people rely for their food and nutritional security. Among them, amaranth, buckwheat, chenopod, job’s tear millet and rice bean are the potential crop species of the region as they can easily be grown in harsh environments and degraded lands. These crops possess an exceptionally high nutritional value with higher content of protein, lipids and minerals as well as balanced composition of essential amino acid as compared to other cereals. Majority of people in the country are unaware of the nutritive values of underutilized crops. The chapter provides information on taxonomy, origin and distribution, nutritive value, uses, improved varieties, production and protection technology of the major underutilized crops grown in Himalayan region.

Underutilized crops are well adapted to the lands of Himalayan region and provide food and nutritional security to millions of impoverished people who do not have access to modern agricultural inputs. Owing to their nutritional superiority, underutilized crops are becoming popular in urban area as well as in developed countries as for example Amaranth in USA. With constantly increasing awareness for health products, the demand of underutilized crops is likely to grow in near future. Accelerated research and development are, therefore, essential for increasing production as well as productivity of underutilized crops along with mechanization and value addition.

A lot of infrastructure in the form of sheep breeding or production facilities such as sheep breeding research stations with adequate number of animals have been established and research technologies generated. The research technologies generated have however not been fully adopted by State Animal Husbandry Departments in the field except in Jammu & Kashmir, Himachal Pradesh and Parts of Rajasthan because of artificial insemination under field conditions due to migratory and semi-migratory practices in sheep husbandry, illiteracy among sheep farmers, their prejudices and convictions and difficulties in the preservation and storage of ram semen and main power requirement.

There is need to study the factors associated with adoption and rejection of sheep rearing as a subsidiary occupation and to know the attitude and knowledge of rural people. So that measures could be suggested to bring greater adoption of sheep rearing. The present study was undertaken to reveal the knowledge and attitude of adopters and non-adopters towards sheep rearing with the identification of factors helping and hindering the adoption of sheep rearing enterprise.

This chapter deals with the review of problems, objectives, hypothesis, research methodology and summary of major findings and conclusions based upon them. In addition, recommendations have also been made to accelerate adoption of sheep rearing programme in the five villages of Block Rajouri, District Rajouri, Jammu and Kashmir.

The present study was conducted to measure the knowledge and attitude of rural people towards sheep rearing and to find out the factors responsible for adoption and rejection of sheep rearing. Suitable measures are therefore suggested to bring greater adoption of sheep rearing in the hills of Jammu & Kashmir.

Sustainable sericulture has to take more care about retaining or rebuilding soil quality and health, since it is very high drain on the nutrient content of soil. Sustainability should an evolution criterion in the process of identifying, screening and adopting techno-biological solutions to the sericultural problems. Greater attention should be paid to learn from the indigenous knowledge. In many of the government-sponsored programmes sericulture has been regarded as one of the essential tool for the rural development in the country. As the activities in the sericulture are capable enough to engage the households completely throughout the year and is ideally suited for improving the socioeconomic standards of the rural poor and has often been utilized under various employment programmes in India. As a result, sericulture is being intensively promoted in traditional states like Karnataka, Tamil Nadu, Andhra Pradesh, West Bengal and J & K.

This chapter tries to find out the constraints in adoption of sericulture as subsidiary enterprise the farmers in the Poonch district of Jammu & Kashmir. Since sericulture is not a major activity in the district and farmers never reluctant to cultivate mulberry in their land and allow only dry land for plantation of mulberry and hardly take care thereafter. Under such circumstances the mulberry grows with lesser leaves production and farmers always faced acute shortage of mulberry leaves during silkworm rearing and they did not get the expected return out of the sericulture. Land, water, proper training of mulberry plants, application of fertilizers guarantee high production and productivity over a wide range in the same areas would qualify to be called as sustainable sericulture system in dry/hilly areas. Besides, other components of technology that can ensure sustainability are soil and water conservation, pests control etc.

Livestock plays a subsidiary role in the farm as far as food production is concerned. Their role in absorbing the huge quantities of crop residues, coarse grains, cereals by-products and farm left-over and returning valuable manure to the soil to sustain their fertility for generation is significant. Livestock in general and dairying in particular is emerging as a driving force in the growth of agricultural sector in India. Dairying is the backbone of the marginal farmers and landless labourers spread over numerous villages scattered throughout the country. It is primary source of income and employment for many of India’s poor. This sector can play an important role in determining future prospects for the employment generation and poverty alleviation in the country.

After the Independence of India, the occupational avenues have undergone a tremendous change. With the spread of education and other amenities of life the traditional occupational structure has considerably changed. The Gujjars who had been a nomadic tribe are extensively becoming sedentary. The Gujjars are one of the important pastoral communities of India. Different social scientists and anthropologists have documented the origin and social aspects of the present Gujjars, who lived a pastoral life. Gujjars have their own Gujri language, which they generally speak among themselves. But they correspond with other people in Urdu generally. The main source of income for Gujjars is dairying. Consumers also prefer milk sold by them, as the quality of milk is good. The role of Gujjars to the rural and urban economy cannot be undermined.

Though information on sociological and anthropological aspects of the pastoral communities has been generated in various studies elsewhere but socio-economic studies are scanty. No concerted efforts have so far been made to study the socio economic of Gujjars, particularly with reference to various important economic parameters like resource structure, family composition, education status, economic status.

The present chapter is an attempt to study the socio economic aspects of one of the well known pastoral communities- the Gujjars of the Jammu district.

Rainfed areas currently constitute 55 per cent of the net sown area of India and are home to two-thirds of livestock and 40 per cent of human population. Livestock plays an important role in the rainfed agro-ecosystem, because of inherent risk involved in the crop farming. The aspect of milk production costs in the country need to be reduced to make the dairy industry competitive. The milk production costs are generally high because of small herd size, difficult collection conditions in hills and high feed costs. Cost of production of rearing animals can be reduced either by improving per unit productivity or reducing feed cost which is the major constituent of total cost. The scientific practices of growing feed and fodder needs to be disseminated among the farmers for increasing the efficiency of dairy animals.

Forages also contribute in prevention of soil erosion and decline in organic matter and fertility. They can also help in reducing nitrogen fertilizer costs and the energy costs associated with application of nutrients.This chapter attempts to determine the economics of different fodder and fodder seed crops for highlighting their importance in the livestock sector in hills.

Introduction

Livestock are vital to subsistence farming and sustainable livelihood in most developing countries. Of India’s population of one billion people, more than 70 percent live in the rural areas. India also has more than 30 percent of the world’s bovine population. So, Milk production costs are generally high Livestock rearing plays a significant role in the economy of the Indian people. Crop residues and pastures / grasslands are the major feed resource for this activity.

Climatic, topography, physiographic factors, altitude and related aspects have influenced the distribution of various crop and grass species, which determine the fodder/forages production both qualitatively and quantitatively (Whyte, 1968). Though livestock rearing is an important occupation of farmers in India, the scientific forage cultivation has remained almost neglected. Thoughtless cutting of trees and indiscriminate use of grazing areas has lead to denudation of hill slopes, which has resulted in critically low biomass availability and adverse effects on livestock production in hills and thus, the livestock productivity remains very low.

The North-East Hilly Region (NER) has a good dairy and animal husbandry infrastructure and climatic condition conducive for raring high yielding dairy animals. Other than acting as a supplementary source of family nutrition, dairying is more as a source of livelihood as 90 per cent of the milk is sold out. The various dairy development programme and schemes launched in the region provide the necessary backward and forward linkages to the dairy farmers in term of feed and veterinary aids and collection, processing and marketing of milk. Considering the changing trends of competitiveness in the dairy market and dairy enterprise as such there is a need for a scientific and technological intervention to transform the traditional dairy farming system into a modern and profitable enterprise. The farmers need to be trained and exposed to modern dairy farming system in order to survive in the long run. The outlook for milk production has changed a lot and people are more concerned on the quality of milk and so necessary emphasis has to be made on clean milk production. To order to use the resources effectively and in order to sustain dairying there is a need to upgrade or replace the low yielding animals by high yielding breed/ variety. The SWOT analysis gives a strong signal for opportunities and avenues for further development of dairying in the region. To harness the opportunities of dairying a strong dairy supply chain need to be developed in an organized manner starting from milk producer to ultimate consumer.

Mechanization should not be an end in itself and therefore, in a free choice situation, Governments should refrain from making policies which will stipulate by which means or by how much, agriculture will be mechanized. The type and degree of mechanization should be decided by the producer to best suit his business and his own particular circumstances, and the choice of suitable methods will therefore be just one of a number of choices that the farmer has to make. The decision on if and how to mechanize is often a complicated mix of reasons with economic reasons paramount. The introduction of machines will not only make agriculture more acceptable but will also provide opportunities for the use of higher intelligence, skill and initiative. This chapter attempts to work out the comparative economics of some of the machinery that are useful for hill regions.

For the sustainable development of agricultural mechanization, it is needed to locally fabricate widely used agricultural tools, implements and machinery. However, the prevailing policy does not favour production of agricultural machinery locally (high custom duty of raw materials, no support in promotion, irregular power supply, high electricity cost, poor research & testing support etc.). Hence there is need of reform in policy and program to encourage and support local fabricators to fabricate/manufacture agricultural machinery locally. There is need of testing and standardization of agricultural machinery to reduce the accidents related to agricultural machinery and to provide quality standard agricultural machinery to the farmers.

Weed Management

The productivity of crops much depends on intercultural and weeding operation. The efficient management practices ultimately increases the yield level. The productivity is much dependent on various attributes starting from the variety, climate including human resource management and other factors known well to the farmers. It is estimated that nearly 30-50 per cent of the crop is lost due to weed menace in the agricultural fields. The farmers use various methods of weed control like cultural, mechanical, chemical and manual means. Encompassing all these control measures is known as integrated weed management.

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.

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.

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.