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be practiced utilizing summer showers to control weeds and conserve soil moisture. Light soils can be worked under wide range of moisture. Loamy soils can be easily brought to good tilth. Pulverization of clay soils is difficult as they dry into hard clods. 7.9 METHOD OF PLOUGHING Ploughing aims at stirring and disturb... | Agricultural_studies.pdf | Agri life sciences |
repeated ploughing, when the animal of the farm is having less work. Research has shown that frequent tillage is rarely beneficial and often detrimental. Repeated use of heavy machinery destroys structures, causes soil pans and leads to soil erosion. Moreover energy is often wasted during tillage processes. All these r... | Agricultural_studies.pdf | Agri life sciences |
matter in the soil. • Nodulation is affected in some leguminous crops like peas and broad beans. • Sowing operations are difficult with ordinary equipment. • Continuous use of herbicides causes pollution problems and dominance of perennial problematic weeds (weed shift). • Minimum tillage can be achieved by the followi... | Agricultural_studies.pdf | Agri life sciences |
and trash bars clear a strip over the previous crop row and planter–opens a narrow strip into which seeds are planted and covered. In zero tillage, herbicide functions are extended. Before sowing, the vegetation present has to be destroyed for which broad spectrum non-selective herbicides with relatively short residual... | Agricultural_studies.pdf | Agri life sciences |
during fallow periods. Sweeps or blades are generally used to cut the soil up to 12 to 15 cm depth in the first operation after harvest and the depth of cut is reduced during subsequent operations. When unusually large amount of residues are present, a disc type implement is used for the first operation to incorporate ... | Agricultural_studies.pdf | Agri life sciences |
heavy machinery in India is limited and therefore, problem of soil compaction is rare. The type of minimum tillage that can be practiced in India is to reduce the number of ploughings to the minimum necessary i.e., unnecessary repeated ploughings/harrowing can be avoided. 7.11 TILLAGE IMPLEMENTS Any device used to carr... | Agricultural_studies.pdf | Agri life sciences |
respectively. It covers 0.15 to 0.20 hectare in 8 hours. 2. Improved iron plough The bullock drawn improved iron plough is made of mild steel except the pole shaft and hence it has longer life. As and when the share wears off, it can be pushed forward. Pole shaft angle and height of the handle can be adjusted according... | Agricultural_studies.pdf | Agri life sciences |
size tractor drawn mould board ploughs can plough up to a depth of 30 cm. Mould board ploughs are used when soil inversion is necessary. Victory plough is an animal drawn mould board plough with a short shaft. 5. Turn wrest plough This is also called reversible plough. The mould board with share is hinged either left o... | Agricultural_studies.pdf | Agri life sciences |
out furrows, invert the furrow slice and pulverize them thoroughly. Disc plough is especially useful under the following soil conditions: Soil with hard pan and sticky soil, Dry hard ground,Rough and stony ground, Ploughing weedy lands and lands with stubbles, Deep ploughing. Fig. 7.3 Mould board plough Fig. 7.3a Disc ... | Agricultural_studies.pdf | Agri life sciences |
tractor drawn (coverage 5 ha/day) costs Rs. 6000/are available for usage. 7.11.2 Secondary Tillage Implements Secondary tillage is the shallow operation performed after the primary tillage. Secondary tillage implements are used for breaking clods and producing a loose, friable, smooth state. These implements are used w... | Agricultural_studies.pdf | Agri life sciences |
and it enters the soil properly and is better than others. In undulating lands the flexible types adjust themselves to the uneven surface. When the frame is of a zigzag type it called zigzag harrow. B. Spring tine harrow Instead of rigid tines strong steel springs shaped like the letter “C” are attached to the frame. D... | Agricultural_studies.pdf | Agri life sciences |
the tines of the junior hoe to make use of same harrow for different purposes. 296 A TEXTBOOK OF AGRONOMY Sweeps are blades that move horizontally under the soil and cut the shallow rooted weeds. There are two kinds of sweeps. The Central sweep attached to the central tines has horizontal wings extending on both the si... | Agricultural_studies.pdf | Agri life sciences |
Andhra Pradesh. It has a horizontal wooden beam of 15 cm diameter with a fixed handle, shaft pole and blade. The blade is fixed to the beam near the ends by two standards at 25 cm distance from beam. The blade is 1.0 m long, 7.5 cm broad and 1.25 cm thick, with a cutting edge in front. Big sized guntakas are called as ... | Agricultural_studies.pdf | Agri life sciences |
is pushed and pulled alternatively by the operation in between rows of rice crop. The float provided will guide the implement smoothly while working and prevent the implement from sinking. (iii) Long-handled weeders Long handled weeders are used for weeding in row crops for removing shallow rooted weeds. Useful in dry ... | Agricultural_studies.pdf | Agri life sciences |
and for sowing crops in rows. It is suitable for all soils. A multipurpose tool carrier is made up to G.I. tube, which has the provision to attach cultivators (4 Nos.), ploughs (3 Nos.), ridger (2 Nos.), seed drill (4 Nos.) and bund formers (2 Nos.). The spacing between rows is adjustable. The field capacity of plough ... | Agricultural_studies.pdf | Agri life sciences |
is released when he gets down. (c) Wooden float It is a bullock drawn implement with a long sledge-like drag used for land smothering. By working the field with wooden float three or four times lengthwise, crosswise and diagonally the field is smoothen in a better way. 7.11.4.3 Land shaping implements (a) Ridge plough ... | Agricultural_studies.pdf | Agri life sciences |
little backward. When the implement is hitched near the yoke, a small quantity of earth alone is gathered. The gaps formed at the intersection of long and cross bunds while working with the implement are closed with manual labour. Ridges for sowing cotton and similar crops are also formed with bund former, with the bun... | Agricultural_studies.pdf | Agri life sciences |
the latest implement developed by TNAU, to create partial compaction in rice fields in light soils. It has a cylindrical drum with projections on the surface like sheep foot. 7.11.4.4 Sowing implements (a) Country seed drill/‘Gorru’ It consists of a horizontal beam on which a number of tines are fixed at suitable dista... | Agricultural_studies.pdf | Agri life sciences |
in the bed is possible using this drill. The implement consists of a pair of furrowers made of sheet metal with suitable hitching arrangements to the three-point linkage of the tractor. Over the framework of these furrowers 7 numbers of hoppers with metering mechanisms have been mounted. This implement simultaneously s... | Agricultural_studies.pdf | Agri life sciences |
the field, • To minimize leaching loss of nutrients and thereby increase the availability of plant nutrients, • To facilitate better availability of nutrient by achieving reduced soil condition, • To incorporate the weeds and stubbles into the soils, and • To minimize the weed problems The implements used for puddling ... | Agricultural_studies.pdf | Agri life sciences |
ha/day. The average depth of puddle is 23 cm. (vi) Helical bladed puddler It is used to puddle the wetland soil after initial ploughing with country plough or melur plough. It is a bullock-drawn implement. Five numbers of helical blades made of mild steel are fixed in a skewed shape and mounted on a wooden frame having... | Agricultural_studies.pdf | Agri life sciences |
consisting of three main parts namely seed coat, endosperm and embryo, which in due course gives raise to a new plant. Endosperm is the storage organ for food substance that nourishes the embryo during its development. Seed coat is the outer cover that protects or shields the embryo and endosperm. 8.1 CHARACTERISTICS A... | Agricultural_studies.pdf | Agri life sciences |
which reduces weed and disease, damages. • Uniform growth stages, maturity and products. • Maintain good quality under storage conditions. • Reduced cost. 8.3 SEED GERMINATION Germination is a protrusion of radicle or seedling emergence. Germination results in rupture of the seed coat and emergence of seedling from emb... | Agricultural_studies.pdf | Agri life sciences |
time. Table 8.1. Cardinal Temperature for important Crops Minimum °C Optimum °C Maximum °C Maize 8–10 20–25 30–35 Rice 10–12 20–27 30–32 Wheat 3–5 15–31 33 Light: The most effective wavelength for promoting and inhibiting seed germination is red (660 nm) and infrared (730 nm), respectively. Atmospheric gases: Most crop... | Agricultural_studies.pdf | Agri life sciences |
which attack seeds or seedlings growing there from. Seed treatment also includes control of pests when the seed is in storage and after it has been sown/planted. The seed treatment is done for the following reasons; • To protect from seed borne pests and diseases. • To protect from or repel birds and rodents. • To supp... | Agricultural_studies.pdf | Agri life sciences |
as plants. SEEDS AND SOWING 303 8.6.1 Methods of Sowing Seeds are sown directly in the field (seed bed) or in the nursery (nursery bed) where seedlings are raised and transplanted later. Direct seeding may be done by (a) Broadcasting (b) Dibbling (c) Drilling (d) Sowing behind the country plough (e) Planting (f) Transp... | Agricultural_studies.pdf | Agri life sciences |
Seeds are drilled continuously or at regular intervals in rows. It requires more time, energy and cost, but maintains uniform population per unit area. Rows are set according to the requirements. (d) Sowing behind the country plough It is an operation in which seeds are placed in the plough furrow either continuously o... | Agricultural_studies.pdf | Agri life sciences |
soils (black soils), sowing operation is difficult after the receipt of rain. To over come this difficulty, sowing is taken up in dry soil prepared with summer rains, 7-10 days before the anticipated receipt of sowing rains. The seeds germinate after the receipt of the rainfall. This method of sowing is known as dry so... | Agricultural_studies.pdf | Agri life sciences |
require close contact with soil particles to ensure that water can be absorbed readily. A tilled soil makes the contact easier. Forming the soil around the seed (broadcasted seeds) after sowing improves the soil–seed contact. (vi) Seedbed fertility: Tillering crops like rice, ragi, bajra etc., should be sown thinly on ... | Agricultural_studies.pdf | Agri life sciences |
not posses any harmful effect on seeds/emerging seedlings. Chapter 9 Plant Density and Crop Geometry Plant density is the number of plants per unit area in a cropped field. It indicates the size of the area available for individual plant. Crop geometry is the pattern of distribution of plant over the ground or the shap... | Agricultural_studies.pdf | Agri life sciences |
the plant density is optimum. (a) Plant Density and Yield Biological yield increases with increases in plant density up to a point and reaches a plateau with further increase in density, thus no additional biological yield can be obtained. On the other hand, the economic yield increases with increase in plant density u... | Agricultural_studies.pdf | Agri life sciences |
between the minimum size of the plant that can produce some economic yield to the maximum size of the plant that can reach under unlimited space and resources is the elasticity of the plant. The optimum plant density range is high in indeterminate plants. For example, in indeterminate red gram varieties the optimum pla... | Agricultural_studies.pdf | Agri life sciences |
the factors are: (i) Time of sowing The crop is subjected to different weather conditions when sown at different periods. Among the weather factors, the most important factors that influence optimum plant density are day length and temperature. Photosensitive varieties respond to day length resulting in change in size ... | Agricultural_studies.pdf | Agri life sciences |
like trees/shrubs are under this arrangements (i) Square planting Square arrangements of plants will be more efficient in the utilization of light, water and nutrients available to the individual plants than in a rectangular arrangement. (ii) Rectangular planting Sowing the crop with seed drill, wider inter-row and clo... | Agricultural_studies.pdf | Agri life sciences |
higher density due to over seed rate or more seeds/hole and uneven broadcasting. Gap filling is done to fill the gaps that exist due to (i) poor quality seed, (ii) soil crusting, (iii) very shallow or very deep placement of seeds, and (iv) poor moisture availability in dry land. Gap filling is done to maintain density ... | Agricultural_studies.pdf | Agri life sciences |
very similar to that of wild plants in the region. Some of the crops for example including the wheat of today are the derivatives of wild grass. Man has further improved them to suit his own taste and fancy. Even today they are crossed with wild varieties to transfer the desirable characters such as drought and disease... | Agricultural_studies.pdf | Agri life sciences |
weed seeds are small in size and contribute enormously to the seed reserves. Weed seeds germinate earlier and their seedlings grow faster. They flower earlier and WEEDS SCIENCE 309 mature ahead of the crop they infest. They have the capacity to germinate under varied conditions, but very characteristically, season boun... | Agricultural_studies.pdf | Agri life sciences |
operation. • Aquatic weeds transpire large quantity of water, obstruct flow of water; thus affecting fishing, swimming and recreation. • Reduce the land value (white horse nettle–Solanum elagenifolium and Parthenium hysterophorus). • Some weeds are poisonous to livestock–Lochnera pusilla and Abrus precatorius. • Weeds ... | Agricultural_studies.pdf | Agri life sciences |
is to be rejected, especially when the crop is grown for seed. For example, the wild oat weed seeds are similar in size and shape of the crops like barley, wheat, and its admixture may lead to rejection for seed purpose. Contamination by poisonous weed seeds is unacceptable and increases costs of crop cleaning. The lea... | Agricultural_studies.pdf | Agri life sciences |
may limit the cultivation of sorghum or sugarcane. 7. Loss of human efficiency Weeds reduce human efficiency through physical discomfort caused by allergies and poisoning. Weeds such as congress weed (Parthenium hysterophorus) cause itching. Thorny weeds like Solanum sp. restrict movement of farm workers in carrying ou... | Agricultural_studies.pdf | Agri life sciences |
used as greens. Weed as soil binders Panicum repense is an excellent soil binder; keeps bunds in position and prevents soil erosion in high rainfall regions and hilly slopes. Hariyali, kikuyu grass, kollukattai grass (Cenchrus sp.) etc., can be used as soil binders. WEEDS SCIENCE 311 Weeds as manure When weeds are plou... | Agricultural_studies.pdf | Agri life sciences |
bad soils. E. colonum occurs in rich soils while Cymbopogon denotes poor light soil and Sedges are found in ill-drained soils. Other economic uses • Useful in manufacturing of agarbattis) e.g., Cyperus rotundus • Cymbopogon citrates (Citronella oil) and C. martinii (Palmrosa) are used for manufacturing aromatic oil. • ... | Agricultural_studies.pdf | Agri life sciences |
arvensis, Abutilon indicum. 10.3.2 Based on Life Span of Weeds Based on life span (Ontogeny), weeds are classified as Annual weeds, Biennial weeds and Perennial weeds. (a) Annual Weeds Those that live only for a season or year and complete their life cycle in that season or year is called annual. These are small herbs ... | Agricultural_studies.pdf | Agri life sciences |
as with one of the following. Rhizome: Plants having underground stem–Sorghum halapense Stolen: Plants having horizontal creeping stem above the ground–Cynodon dactylon Roots: Plants having enlarged root system with numerous buds–Convolvulus arvensis Tubers: Plants having modified rhizomes adapted for storage of food–C... | Agricultural_studies.pdf | Agri life sciences |
crop lands: The majorities of weeds infest the cultivated lands and cause hindrance to the farmers for successful crop production. e.g., Phlaris minor in wheat. (b) Weeds of pasture lands: Weeds found in pasture/grazing grounds. e.g., Indigofera enneaphylla (c) Weeds of waste places: Corners of fields, margins of chann... | Agricultural_studies.pdf | Agri life sciences |
(b) parasitic weeds, and (c) aquatic weeds. (a) Poisonous weeds The poisonous weeds cause ailment on livestock resulting in death and cause great loss. These weeds are harvested along with fodder or grass and fed to cattle or while 314 A TEXTBOOK OF AGRONOMY grazing, the cattle consumes these poisonous plants. e.g., Da... | Agricultural_studies.pdf | Agri life sciences |
weeds are mostly vascular plants that produce all or most of their vegetative growth beneath the water surface, having true roots, stems and leaves. e.g., Utricularia stellaris, Ceratophyllum demersum. Emersed weeds These plants are rooted in the bottom mud, with aerial stems and leaves at or above the water surface. T... | Agricultural_studies.pdf | Agri life sciences |
10.4 WEED DISSEMINATION (DISPERSAL OF WEEDS) Dispersal of mature seeds and live vegetative parts of weeds is nature’s way of providing non-competitive sites to new individuals. Had there been no way of natural dispersal of weeds, we would not have had them today in such widely spread and vigorous forms. In the absence ... | Agricultural_studies.pdf | Agri life sciences |
are passed in viable form with animal excreta (0.2% in chicks, 9.6% in calves, 8.7% in horses and 6.4% in sheep), which is dropped wherever the animal moves. This mechanism of weed dispersal in called endozoochory e.g., Lantana seeds by birds. Loranthus seeds stick on beaks of birds. Farm animals carry weed seeds and f... | Agricultural_studies.pdf | Agri life sciences |
3. Packing material and 4. Nursery stock. e.g., Parthenium hysterophorus. 10.5 WEED ECOLOGY Knowing weed biology such as seed production capacity, germination dormancy and their ecological 316 A TEXTBOOK OF AGRONOMY adaptations will help in formulating suitable weed control measures. Ecology is the interrelationship be... | Agricultural_studies.pdf | Agri life sciences |
genetically identical nature and as such may not well adapted to change in environment. The vegetative structures include stolons, rhizomes, tubers, bulb, corms and roots. B. Seed Dormancy as Survival Mechanism Weed seeds possess a variety of special germination mechanisms adapted to changes in temperature, moisture, a... | Agricultural_studies.pdf | Agri life sciences |
years of burial in soil. Weed seeds exhibit three types of dormancy. 1. Enforced dormancy It is due to deep placement of weed seeds in soil during ploughing of the field. Weed seeds germinate readily when they are restored to top 3-5 cm. Enforced Dormancy is a non-specific character of seed. Cultivation encounters enfo... | Agricultural_studies.pdf | Agri life sciences |
In an agricultural situation, the cropping system with its (associated habitat) management practices, determines the persistence of weed species. It is largely influenced by climatic, edaphic (soil) and biotic factors, which affect its occurrence, abundance, range and distribution. Factors affecting persistence 1. Clim... | Agricultural_studies.pdf | Agri life sciences |
Neutophiles Alkaligrass – Puccinalia spp. Cynodon dactylon Common weed Quack grass – Agrophyron repens Digitaria sanguinalis Several weed species of compositae family grow well in saline soils. A shift in soil pH, towards acid side due to continuous use of Ammonium sulphate as a ‘N’ source could cause a shift in the we... | Agricultural_studies.pdf | Agri life sciences |
Without interference by man, weeds would easily wipe out the crop plants. This is because of their competition for nutrients, moisture, light and space, which are the principle factors of production of crop. Generally, an increase in on kilogram of weed growth will decrease one kilogram of crop growth. 1. Competition f... | Agricultural_studies.pdf | Agri life sciences |
more of N, 10 times more of P and 7 times more of K. 2. Competition for moisture In general, for producing equal amounts of dry matter, weeds transpire more water than do most of our crop plants. It becomes increasingly critical with increasing soil moisture stress, as found in arid and semi-arid areas. As a rule, C4 p... | Agricultural_studies.pdf | Agri life sciences |
deficiency. Leaf area development is reduced. Yield attributes will be lowered. It reduces the water use by the crop and affects the dry matter production. It lowers the input response and causes yield reduction. Pest and disease incidence on crops will be more due to weeds. B. Factors affecting the Competitive Ability... | Agricultural_studies.pdf | Agri life sciences |
Crops and their varieties differ in their competing ability with weeds e.g., the decreasing order of weed competing ability is as: barley, rye, wheat and oat. High tolerance of barley to competition from weeds is assigned to its ability to develop more roots that are extensive during initial three weeks growth period t... | Agricultural_studies.pdf | Agri life sciences |
compete with crops, in both moisture stress and ample moisture conditions. Removal of an intense moisture stress may thus benefit crops more than the weeds leading to increased yields. If the weeds were already present at the time of irrigation, they would grow so luxuriantly as to completely over power the crops. If t... | Agricultural_studies.pdf | Agri life sciences |
top 3 to 5 cm of soil rapidly WEEDS SCIENCE 321 enough to deny weed seeds opportunity to absorb moisture for their germination usually postpones weed emergence until the first irrigation. By this time the crop plants are well established to compete with late germinating weeds. (h) Cropping practices Cropping practices,... | Agricultural_studies.pdf | Agri life sciences |
expenditure without proportionate increase in yield. Table 10.4. Critical period of Weed Competition for important Crops Sl.No. Crops Days from sowing 1. Rice (lowland) 35 2. Rice (upland) 60 3. Sorghum 30 4. Finger millet 15 5. Pearl millet 35 6. Maize 30 7. Cotton 35 8. Sugarcane 90 9. Groundnut 45 10. Soybean 45 11.... | Agricultural_studies.pdf | Agri life sciences |
allelochemicals it. • Life cycle: If weed emerges later there will be less problem of allelochemicals. • Plant age: The release of allelochemicals occurs only at critical stage. For e.g., in case of Parthenium, allelopathy occurs during its rosette and flowering stage. • Plant habit: The allelopathic interference is hi... | Agricultural_studies.pdf | Agri life sciences |
leachate of decaying leaves of Polygonum contains flavonoides which are toxic to germination, root and hypocotyls growth of weeds like Amaranthus spinosus. • Inhibitor secreted by decaying rhizomes of Sorghum halepense affect the growth of Digitaria sanguinalis and Amaranthus sp. 10.7 WEED CONTROL For designing any wee... | Agricultural_studies.pdf | Agri life sciences |
Eradication • Control • Management A. Preventive Method The appearance of weeds in the cropped areas can be prevented by adopting the following measures for adoption wherever possible and practicable. It encompasses all measures taken to prevent the introduction and/or establishment and spread of weeds. Such areas may ... | Agricultural_studies.pdf | Agri life sciences |
area in which a severe weed has become established and prevent the movement of the weed into an uninfected area. • Use of pre-emergence herbicides also helpful in prevention because herbicides will not allow the germination of weeds. • Avoid feeding screenings and other material containing weed seeds to the farm animal... | Agricultural_studies.pdf | Agri life sciences |
area and that weed will not reappear unless reintroduced to the area. Because of its difficulty and high cost, eradication is usually attempted only in smaller areas such as few ha., a few thousand m2 or less. Eradication is often used in high value areas such as green houses, ornamental plant beds and containers. This... | Agricultural_studies.pdf | Agri life sciences |
weeds present by some kind of physical or chemical means while weed management is a system approach whereby whole land use planning is done in advance to minimize the very invasion of weeds in aggressive forms and give crop plants a strongly competitive advantage over the weeds. Weed control methods are grouped into cu... | Agricultural_studies.pdf | Agri life sciences |
useful implement to obtain results effectively and cheaply. It supplements the cultivator in row crops. Hoeing is particularly more effective on annuals and biennials as weed growth can be completely destroyed. In case of perennials, it destroyed the top growth with little effect on underground plant parts resulting in... | Agricultural_studies.pdf | Agri life sciences |
prevent soil erosion. Mowing is a machine-operated practice mostly done on roadsides and in lawns. 7. Burning Burning or fire is often an economical and practical means of controlling weeds. Burning the weeds will control the weed problem in sugarcane widely spaced field crops and orchards. It is used to (a) dispose of... | Agricultural_studies.pdf | Agri life sciences |
tillage, planting, fertilizer application, irrigation etc., are employed for creating favourable condition for the crop. These practices if used properly, help in controlling weeds. Cultural methods, alone cannot control weeds, but help in reducing weed population. They should, therefore, be used in combination with ot... | Agricultural_studies.pdf | Agri life sciences |
group of species occurring is greater if the same crop is grown year after year. In many instances, crop rotation can eliminate at least reduce difficult weed problems. The obnoxious weeds like Cyperus rotundus can be controlled effectively by including low land rice in crop rotation. Inclusion of smothering crop or co... | Agricultural_studies.pdf | Agri life sciences |
utilization of solar energy for the desiccation of weeds. In this method, the soil temperature is further raised by 5–10ºC by covering a presoaked fallow field with thin transparent plastic sheet. The plastic sheet checks the long wave back radiation from the soil and prevents loss of energy by hindering moisture evapo... | Agricultural_studies.pdf | Agri life sciences |
weeds. • Proper crop rotation programme. • Higher plant population per unit area results in smothering effect on weed growth. Merits • Low cost for weed control • Easy to adopt • No residual problem • Technical skill is not involved • No damage to crops • Effective weed control • Crop-weed ecosystem is maintained Demer... | Agricultural_studies.pdf | Agri life sciences |
way. It must possess reproductive capacity sufficient to overtake the increase of its host species, without too much delay. (ii) Merits • Least harm to the environment • No residual effect • Relatively cheaper and comparatively long lasting effect • Will not affect non-targeted plants and safer in usage (iii) Demerits ... | Agricultural_studies.pdf | Agri life sciences |
controlled by larvae of Crocidosema lantana, a moth bores into the flower, stems, eat flowers and fruits. • Cuscuta spp. is controlled by Melanagromyza cuscutae. • Cyperus rotundus Bactra verutana a moth borer. • Ludiwigia parviflora is completely denuded by Altica cynanea (steel blue beetle). • Herbivorous fish Tilapi... | Agricultural_studies.pdf | Agri life sciences |
odorata) in Phytophthora palmivora causes root rot. citrus 2. Collego Wettable powder containing fungal spores Joint vetch (Aeschyomone virginica) of Colletotrichum gloeosporoides causes in rice, soybean stem and leaf blight 3. Bipolaris A suspension of fungal spores of Bipolaris Jhonson grass (Sorghum halepense) sorgh... | Agricultural_studies.pdf | Agri life sciences |
to dispersal of weed species through seed. It is profitable where labour is scarce and expensive. Herbicide application is well suited for minimum tillage concept and it provides early season/zero day weed control and its application is highly economical. 330 A TEXTBOOK OF AGRONOMY III. Demerits • Pollutes the environm... | Agricultural_studies.pdf | Agri life sciences |
Non-selective Selective (Arsenicals) Selective (Sodium arsenate, Thiocynates) Volatile (Carbon bisulphide) Nonvolatile (Sodium chlorate) Herbicides Sprayed over foliage Soil applied Translocated Non-selective Non-selective WEEDS SCIENCE 331 2. Based on target site Depending on the target site, the herbicides are classi... | Agricultural_studies.pdf | Agri life sciences |
(d) Fumigation Application of volatile chemicals into confined spaces or into the soil to produce gas that will destroy weed seeds is called fumigation. Herbicides used for fumigation are called as fumigants. These are good for killing perennial weeds and as well for eliminating weed seeds. E.g., Methyl bromide, Metham... | Agricultural_studies.pdf | Agri life sciences |
glove are useful here. 2. Based on mode of action Selective herbicide A herbicide is considered as selective when in a mixed growth of plant species, it kills some species without injuring the others. e.g., Atrazine. Non-selective herbicide It destroys majority of treated vegetation e.g., Paraquat. 3. Based on mobility... | Agricultural_studies.pdf | Agri life sciences |
Hence, these have to be made in forms suitable and safe for their field use. An herbicide formulation is prepared by the manufacturer by blending the active ingredient with substances like solvents, inert carriers, surfactants, stickers, stabilizers etc. The objectives in herbicide formulations are as follows: • Ease o... | Agricultural_studies.pdf | Agri life sciences |
to soil and incorporated before sowing rainfed groundnut while glyphosate can be applied on the foliage of perennial weeds like Cyperus rotundus before planting of any crop. (ii) Pre-emergence Application of herbicides before a crop or weed has emerged. In case of annual crops application is done after the sowing of th... | Agricultural_studies.pdf | Agri life sciences |
of herbicides Crop factor Monocots and dicots show differential tolerance to a herbicide, accordingly depending on type of crop cultivated the choice of herbicides varies. e.g., Monocots like rice has tolerance to 2,4-D Na salt while dicots like soybean gets killed when used as post-emergence. Nature of weeds present B... | Agricultural_studies.pdf | Agri life sciences |
Fluchloralin 0.90 Basalin 45% EC Pre-emergence Pendimethalin 0.90 Stomp 30% EC Pre-emergence 2,4-D Na salt 1.00 Fernoxone 80% SS Post-emergence 2. Rice (Upland Thiobencarb 1.25 Saturn 50% EC Pre-emergence direct sown) (8 DAS) Pretilachlor 0.45 Refit 50% EC Pre-emergence 3. Sorghum Atrazine 0.25 Atrataf 50% WDP Pre-emer... | Agricultural_studies.pdf | Agri life sciences |
AND FUNGICIDES Simultaneous or sequential application of herbicides, insecticides, fungicides, antidotes, fertilizers etc. are followed in a single cropping season. These chemicals may undergo a change in physical and chemical characters, which could lead to enhancement or reduction in the efficacy of one or more compo... | Agricultural_studies.pdf | Agri life sciences |
effect of a combination is smaller than the effect of the most active component applied alone. e.g., combination of EPTC with 2,4-D, 2,4,5-T or dicamba has antagonistic responses in sorghum and giant foxtail. Similarly, chlorpropham and 2,4-D have antagonism. When simazine or atrazine is added to glyphosate solution an... | Agricultural_studies.pdf | Agri life sciences |
Atrazine but they become susceptible in wet weather, particularly when air temperature is low. Extra succulence has been found to increase atrazine absorption and low temperature decrease its metabolism inside the plants. Quality of water used may also determine herbicide action. Dusty water reduces action of paraquat.... | Agricultural_studies.pdf | Agri life sciences |
may decrease the incidence of root rot in wheat. E. Herbicide-fertilizer Interaction Herbicides have been found to interact with fertilizers in fields. e.g., fast growing weeds that are getting ample nitrogen show great susceptibility to 2, 4-D, glyphosate than slow growing weeds on poor fertility lands. The activity o... | Agricultural_studies.pdf | Agri life sciences |
the conscious employment of natural limiting factors. IWM is the rational use of direct and indirect control methods to provide cost-effective weed control. Such an approach is the most attractive alternative from agronomic, economic and ecological point of view. Among the commonly suggested indirect methods are land p... | Agricultural_studies.pdf | Agri life sciences |
Indiscriminate herbicide use and its effects on the environment and human health. C. Concept • Uses a variety of technologies in a single weed management with the objective to produce optimum crop yield at a minimum cost taking into consideration ecological and socio-economic constraints under a given agro-ecosystem. •... | Agricultural_studies.pdf | Agri life sciences |
Labour saved Less input No or less toxic Co-existed with other technique Useful Agents WEEDS SCIENCE 339 10.10 HERBICIDE MIXTURES Involves mixing of two or more herbicides used for effective and economical weed control. A. Advantages • A mixture will broaden the spectrum of herbicidal action and kill a variety of weeds... | Agricultural_studies.pdf | Agri life sciences |
(Herbicide is captured in vacuole and inactivated excluding the herbicide from site of action). • Reduces the quantities of herbicide required for optimum weed control over the years. • Provides most effective weed control for the duration of crop growth. • Reduces the building up of herbicide residue problems. • It of... | Agricultural_studies.pdf | Agri life sciences |
of a population • Genetic variation by mutation or activation of pre existing genes Conditions favourable • Repeated use of same herbicide or use of herbicide with same mode of action due to the practices of monoculture • Areas where minimum/zero tillage is followed • Fields where farmers rely on only herbicides for hi... | Agricultural_studies.pdf | Agri life sciences |
to improve the herbicidal effects, sometimes making a difference between satisfactory and unsatisfactory weed control. Mode of Action: Adjuvants aid the herbicide availability at the action site in plants. WEEDS SCIENCE 341 Kinds of adjuvants 1. Surfactant (Surface active agents) • Aid in wetting the waxy leaf surface ... | Agricultural_studies.pdf | Agri life sciences |
is used to solubilize a herbicide in a concentrated form; the resulting solution is soluble with water in all proportions. e.g., 2,4-D is insoluble in water, but it can be dissolved in polyethylene glycol to make it water soluble. Common solvents: Benzene, acetone, petroleum ether, carbon tetrachloride. 4. Humicants (H... | Agricultural_studies.pdf | Agri life sciences |
which can help to minimise the residue hazards in soil. 342 A TEXTBOOK OF AGRONOMY A. Use of Optimum Dose of Herbicide Hazards from residues of herbicides can be minimized by the application of chemicals at the lowest dosage by which the desired weed control is achieved. Besides, applying herbicides in bands rather as ... | Agricultural_studies.pdf | Agri life sciences |
cropped with cowpea is the recommended weed control practice. The above weed management schedule did not show any residual effect in the cropping system because the herbicides are changed for every crop. E. Use of Non-Phyto-Toxic Oil Atrazine residual hazard could be reduced by mixing non-phyto-toxic oil, which would a... | Agricultural_studies.pdf | Agri life sciences |
roots. Chapter 11 Irrigation and Water Management Plants and any form of living organisms cannot live without water, since water is the most important constituent of about 80-90% of most plant cell. Water is essential not only to meet agricultural needs but also for industrial purposes, power generation, live stock mai... | Agricultural_studies.pdf | Agri life sciences |
balance. • It reduces salinity and alkalinity. • It influences weed growth. • It influences atmospheric weather. 344 A TEXTBOOK OF AGRONOMY • It helps the beneficial microbes. • It supports human and animal life. • It helps for land preparation like ploughing, puddling etc., weeding, fertilizer application etc., by pro... | Agricultural_studies.pdf | Agri life sciences |
as a beauty • Water as a destructive force to be controlled • Water as a fuel for urban development • Water a place for recreation and wild life habitat. 11.2 IMPORTANCE OF IRRIGATION MANAGEMENT Irrigation is the artificial application of water made for supplementing the moisture in the soil that is deficient and does ... | Agricultural_studies.pdf | Agri life sciences |
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