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12, 12, , AOua, , Semi aud.asle, Homtd, , Dryland, Agriculture, nd E, Jota, , w t JomdANE, , dapemds m tnim, , Won-10uuptt, , wgrucltuwe, exelndes, , Jylands, dvugoion, nafcrops entirely undef rainfeconditions is known as dryland, agriculture), he, amount of rainfall received dryland agriculture can be grouped into threé Depending, ont, categories, PDry, Farming { Cultivation of crops in areas where rainfall is le_s than, oDry Farming, 750 mm per, annum is called dry farming.Prolonged dry spells during crop period are most common., Crop failures are more frequent junder dry farming conditions. Dry farming(regions are, equivalent to arid regions and móisture conservation practices are important in this region., , Dryland Farmingt Cultivation of crops in areas receiving rainfall above 750 mm, iskhown as dryland farming,Dry spells during crop period occur, but crop failures are less, frequent Dryland farming areas are grouped unde semiarid regions) Adoption of soil and, moisturé conservation practices and also provision of drainage espeially in black soils are, , necessary., Rainfed Farming :Cultivation of crops,in regions receiving more than 1,150 mmn, rainfall is know as rainfed farming It is practiced in humid regions where crop failures are_, , Tare and drainage, , is the, , important problem, , United Nations Economic and Social Commission for Asia and the Pacific distinguished, , dry grculture mainly into two categories: dryland and rainfed farming. The distinguishing, featresof these two types of farming are given in Table 12.1., the143.8 million hectares of cultivated land in India, irrigated area constitutes 30.5, , and 69.5 per, , cent, , is,dryland and rainfed area (Table 12.2),/These, , areas contribute, , and, 42% of the food graing. Almost of all coarse grains, about5% of the pulses, ramted, oilseedt h i r d s of mustard, most of soybean and groundnut are grown under, , Condition, , Jwsent, , Stelns

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a l w a y s o n de, , first among, and value of produce., , ranks, Indiaranks, , RES, N, the, , rainfed, , ApuanOn exceeas rainjal., , TATUS, agriculturál countries, , of the world, , regarding both extent, , In India, severe drought 1s experienced once in 50 years, partial drought once in 5 years, and, floods are expected every year in one and another part of the country., , The 128 districts in lndia have been recognized as dryland farming areas whereas, 74 districts, , recognized as drought-prone district., of the total arable land, 94 M ha fall under drylands constituting 65% of arable land andrainfed, The, area produces about 40% of the total food grains that feed 40% of the total population., , are, , remaining of 50 M ha constituting 35% ofirrigated areas account for 60% ofthe crop production., , inistry, , of Rural, , Development, , in 1993 constituted, , a, , committee under the, , chairmanship, , Prof. C.H. Hanumantha Rao to review the DPAP and DDP programmes., , Total arable land, , 143.8 M ha, , Dryland, Rainfed, Irrigated area, , 34.5 M ha, , 65.5 M ha (15 M ha flood-prone), 43.8 M ha, , 100%, , 24%, 45.5%, , 30.5%, , of

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TABLE 12.1., , to, , Growing season (days), , Growing regions, , rainfed, , farming, , the crop, , Rainfed farming, , <800, , 800, , Shortage, , Enough, , 200, Arid and semiarid as well as, , uplands, region, , Croppping system, , vs, , Dryland farming, , Constituent, Rainfall (mm), Moisture availability, , Dryland, , 200, Humid and sub-humidregi, , of sub-humid and humid, , Single crop or intercropping, , Intereropping or double, , cropping, Constraints, , Wind and water erosion, , Water erosion

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The Concept, The, , concept of rainfed agriculture (farming) under, , which both, , dry farming and drvland, , the earlier concent, (dryland agriculture) is included has been changed. Dry faring, farming, for which amount of rainfall (less then 500 mm annually) remained the deciding factor for more, was, , e, , than 60 years., n modern concept dryland areas are those where the balance of moisture is always on the, , deficit side. In other words, annual evapotranspiration exceeds precipitation) Indryland agriculture,, there is no consideration of amount of rainfall. It may appear quiet strangeto a layman that even, those areas which receive 1100 mm or more rainfall annually fall in the category of dryland, be more specific, the average annual rainfall of Varanasi is, under this, , agriculture, , concept. To, , around 1100 mm and the annual potential evapotranspiration is 1500 mm. Thus the average, , moisture deficit so created comes to 400 mm. This deficit in moisture is bound to affect the crop, , production under dryland situation, ultimately resulting into total or partial failure of crops., Accordingly, production is either low or extremely uncertain and unstable which are the real, problems of dryland in India., Success of crop production in these areas depends on the amount and distribution of rainfal,, as these influences the stored soil moisture and moisture used by crops. (Amount of watr used, by crop and stored in soil is governed by water balance equation : ET P-(R + S). )When, , balance of the equation shifts towards right, precipitation (P) is higher then ET, so that thére may, be waterlogging or it may even lead to runoff (R) and flooding. On the other hand, ifthebalance, , shifts to left, ET becomes higher then precipitation, resulting in drought. Taking the country as, per meteorological report, severe drought in large area is experienced once 1n of, years and partial drought once in five years while floods are expected every year in one part, the country or the other, especially during rainy season. In fact, the balance of the equation, a, , whole,, , as, , controlled by weather, season, crops and cropping patten., , S= P-(Rt+E T)

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The, , chronology, , A880, , 1920, , of, , major, , events in, , dryland agricultural research, , in India is, , The First, , as, , follows, , Famine Commission was appointed by the then British, Empire to suggest, ways and means to offset the adverse effects of recurring, droughts, which country, faced from 1860 onwards. An important recommendation of the, commission was, to set up protective irrigation project., The Royal Commission on Agriculture stressed the need for, scarcity tract, development., , 1923, , The then, , 1933, , Bombay Dry Farming Research Schemes at Bijapur and Sholapur--the centers of, , Imperial Council of Agricultural Research sanctioned six schemes and, established the first Dryland Research Station at Manjari (Pune) by Tamhane., famine tract., , 1934, , The Madras Dry Farming Research Scheme at Hagari (near Bellary) and the, , Hyderabad Dry Farming Research Scheme at Raichur., The, , Punjab Dry Farming, , 1942, , Research Scheme at Rohtak, Bombay Land Development act passed., , 1944, , Monograph on dry farming in India by NV Kanitkar (Bombay, Hyderabad and, , 1935, , (Punjab)., , Madras Dry, , Farming Practices), Establishing Central Soil Conservation Board., The Central Soil and Water Conservation Research and Training Institute at, , Dehradun., 1954, , Soil Conservation Research, Demonstration and Training Center, Ootacamund., , 1954, , Soil Conservation Research, Demonstration and Training Center, Bellary., , 1954, , Soil Conservation Research, Demonstration and Training Center, Kota., , 1955, , Soil Conservation Research, Demonstration and Training Center, Vasad., , 1957, , Soil Conservation Research, Demonstration and Training Qenter, Agra., , 1957, , Soil Conservation Research, Demonstration and Training Center, Chandigarh., , Central Arid Zone Research Institute (CAZRI) was established at Jodhpur to tackle, the, , 1962, 1962, , problems, , of arid, , agroecosystem., , Soil Conservation Research, Demonstration and Training Center, Ibrahimpatnanm., Launching of Soil Conservation in the Catchments of River Valley Projects., All, , India, , 1Ocations, , Coordinated Research Project for, , Drvland Agriculture (AlCRPDA) in 23, , Development, with the support from Canadian lnternational, signed between the, an instrument of bilateral collaboration, , (now 25), , Bency through, , Governments of India and Canada (up to 1987).

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268, , Moistuoe-Poetion, inde, , to Salusb, SalS, ehtotal Pe PLYaion Usedl to, PRINCIPLES OF AGRONOMY, , Plantheeda, , 1972, , Group on International Agricultural Research (CGIAR) established, Semi-Arid Tropics (ICRISAT) at, International Crops Research Institute for the, , The Consultative, , the, , Hyderabad., 1980, , Dryland Operational Research Projects., of Flood prone area., Integrated Watershed Management in the Catchment, , 1983, , Starting of 47, , 1984, , Initiation of World Bank assisted Watershed Development, , 1976, , Establishment of, , model watersheds under 1CAR., , Programmes in four, , states., , 1985, 1985, , 1985, 1986, 1989, 1989, , 2006, , The Central Research Institute for Dryland, , National Wasteland Development Board, , Launching of NWDPRA, , Integrated, , Watershed, , programmes, , by, , at, , Hyderabad., , (NWDB)., Government of India in 15, , Development Projects (IWDP) by, , Development Board (NWDB), , National Rainfed Area, , Agriculture (CRIDA), , Authority (NRAA), , National, , states., , Watershed

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Arid and Semiarid Regions of India, Arid regions :(Moisture îndex of these regions varies from-66.7 to -100. Rainfall is less, than potential evaporation for the greater part of the year( Arable crop production is not possible, , without irigation. Effectide crop season is less than 75 days.), Semiarid regions : Moisture index varies from-33.3 to 66.7,)Crop production is possibly, with soil and water conservation practices, Effective crop season is between 75 and 119 days., , A semiarid climate is essentially a mixed climate in which a relatively rainy period alternates, with a rainless dry, period Rainfall occurs during 2 to 7 months of the year. If the number of wet, 2.0 to 4.5,, ia, as dry SAT, when rainy period ranges from 4.5 to 7.0, and, it, as wet, rainfall varies, 400 to 750 mm pekyear, with a variability, of 20 to 30 per cent. But, the onsèt closure and duration of rainy season exhjbits wide variability, , months is, is called, , it described, SATAmountof, , îrom, , between years. Distribution of rainfal within the season also exhibits wide îhctuations between, , years Mean-annual temperature is-more than 18°C( Total area under, , f, , arid and semiarid, , regions, , ofIndia extends over 135.8 Mha(Table 5.3)., Maximum temperature in arid_and semiarid temperate region is around 35°C in July and, minimum 14°C in January-February Temperature in arid and semiarid, of is maximum at, tropics, 40°-42°C in May and minimum varies from 3°-5°C in Punjab and Haryana to18°-24°C in Tamil, Nadu Rajasthan has the highest dry farming area (arid and, semiarid) followed by Maharashtra,, AP, Gujarat, Haryana and, , Karnataka.

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worldwide., , Progress of Research, , Agriculture, growing, crops, , was, , Drought, , tam tall, , mmo4OUt tOnstut ausl, , V)s, , Cxtoume Sca, , Hamine, , hoo, , agriculture. Providing of irrigation, dryland agriculture came due to famines. In, , of crops, started with rainfed, , adopted subsequently. The focus, , on, , 1880 the first famine commission was ppointed to suggest preventive measures to fake, drought and measures to avoid famines! One of the important recom-mendations of the fis, famine, , commission was to provide faeilhties, , for, , protectiye irTigation/, , Systematic research work was started from 1923 with the start of Research Centrea, Manjre near Pune, in Bombay province. Later Imperial Council of Agriculture Researc, , presently Indian Council Agricultural Research) started research schemes at Bombay, Madras, Hyderabad and Punjab provinces. Around 1933, systematic work was started on diferen, aspects of crop production under rainfed conditions. The findings of the period were relate

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DRYLAND AGRICULTURE, in, , fall, , analysis., , lle during, Spells, , It, , was, , UcAtou433, , found that rainfall was not only scarce but also erratic. The dry, , the crop period ranged from 20 to 55, , days. Therefore, the emphasis on research, as oiven conserve soii moistureand to reduce evaporation. Based on the studies conducted, 1933 and 1943, package was developed for better, et, crop production under rainfed, to, , conditions. The important practices are, , Formation of contour bunds. which u d n duum o, , tOTAen, , mois, , Repeated harrowing, Addition, , of, , in black soils to, conserve moisture., yard manure to maintain the soil, , farm, fertility., Wider spacing for crops grown on residual, moisture, The package of practices were named after the, province from which they were developed, as Bombay dry farming practices, Madras dry farming practices, Hyderabad dry farming, practices and Punjab dry farming practices. The adoption of these practices was low due to, marginal increase in yield. Government programmes mainly concentrated on contour bunding, which provided employment during drought periods. During 1954, the soil conservation, training and demoistration centres were established by Indian Council of Agriculture Research, at eight locations. These centres concentrated on soil conservation techniques and training of, oficers on soil cønservation, while crop production received low importance.During 1970., ICAR started All India Coordinated Research Project on Dryland Agriculture at 23 location, spread all over India Under the scheme, an integrated approach was adopted to solve the, , problems of dryland ágriculture, by including the disciplines of agronomy,, , soil science,, , plant, , breeding and agriculture engineering. The important practices developed under the scheme, , are contingent cropping, efficient crops and cropping systems, water harvesting and, , Supplemental irrigation, drought resistant varieties, fertilizer recommendation and agricultural, mplements. Watershed approach was fallowed to popularise these technology by including, , 5oil conservatiop-practices with improved dryland practices, alternate crops and other ancillary, , enterprises. In 1983, 47 model watersheds were developed. Based on the success of this, approach increasing the productivity of drylands, the national watershed development, programme for dryland agriculture was started through out the country.

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Major problems, , of, , dryland agriculture include, , Vagaries of monsoon rainfail., , A Soil constraints., , Lack of suitable varieties., , Traditional cultivation practices., , Heavy weed infestation., , 5.2.1. VAGARIES OF, Based, , on, , eicient and, , Socioeconomic constraints., , MONSOON, , average annual raintall,, , the, , country, , can be, , divided into, , three zones: low (less, medium (750-1,150 mm) and high, than 750, (aore, than, 1,150, mm), rainfall zones. Dryland area is, nearly equally distributed among the, three. Areas with less, mm)., , 1,150 mm (arid and semiarid), than, crop production. Main characteristics, (features) of rainfall influencing, crop production are its variability,, and, intensity, distribution, late onset and early withdrawal of, monsoon and prolonged dry, spells during the crop period., are, , the, , problem, , areas for, , Variable Rainfall, Annual rainfall varies greatly, from year to year. Table, coefficient of variation. Generally,, the, , higher, , otherwords, crop failures due to uncertain rains, , Jausal, , met, , kighest Cv, CV, Cv omnnuavuomall, , 5.4 indicate annual rainfall and its, , rainfall, less is the coefficient of variation.) n, , are, , more frequent in regions with lesser raintal., , 20-3o /

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coeiñcient, annual r a i n f a l l and, TABLE 5.4. Mean, i n s e l e c t e d locations., , of variation, , Annual rainfall, , Location, Hissar (Haryana), , Anantapur (AP), Ludhiana (Punjab), Sholapur (Maharashtra), Kovilpatti (TN), Anand (Gujarat), , Mean (mm), , CV (%), , 451, 565, 661, , 31, 30, 50, , 708, 749, , 28, 27, , 869, 888, , 40, , Ranchi (Bihar), , 1,264, 1,308, 1,338, , 20, 22, 24, 16, , Mohanpur (WB), , 1,389, , 19, , Bangalore (Karnataka), Ranichauri (UP), , Jabalpur (MP), , Intensity and Distribution, received in 3 to 5 rainy davs., In general more than 50 per cent of total rainfall is usually, due to surface runoff.)This process als0, Such intensive rainfall re_ults in substantial loss of water, , accelerates soil erosion Distribution of rainfall during the crop growing season is more important, thantotal rainfall in drýland agriculture., Late Onset and Early Cessation of Rains, , Due to late onset of monsoon, sowing of crop is delayed resulting in poor yields. Sometimes, , the rain may cease very early in the season exposing the crop to drought during flowering and, maturity stages which reduces the crop yields considerably, , Prolonged Dry Spells During Crop, , Period, , Long breaks in the rainy season are an important feature, , of Indian, , monsoon. These intervening, , dry spelis when prolonged during crop period reduces crop growth and yield and when unduly, prolonged crops fail., , 5.2.2. SOIL CONSTRAINTS, , Ot, , A4isols, , Sud2, , Alluvial soilsthese, occupy, the largestarea in dryland bgriculture Problems of crop production are not, soils as they are in black and red soils) Majór problems are encountered m, Vertisols, Alfisols and related soils) Black (Vertisols), red (Alfisols) and associated soils are mostly, distributed in central and south India. The coastal areas have Alfisols, laterite and lateritic soils., , Alfisols, These are commonly referred as red soils,Problems relating to crop productionare, , Poor crop stand due to crusting and rapid drying of surface soil., Poor crop growth due to unreliable soil moisture supply, low moisture storage capacity), , due to shallow depth jand drought spells during crop season., Low soil fertility due to low organic matter) poor nutrient status particularly with respect, to N, P, S and Ca and compact subsoil layer (argillic horizon)., Land degradation from soil erosion and crusting.

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DRYLAND AGRICUL TURE, , 271, , Soil crusts are dry, thin and hard soil surface layers that develop due to the action of rain, r)The impact of rain and or irrigation disrupts the soil aggregates, reduces, water,, drop or irrigation, of the structural units and causes resorting and repacking by water movement in, size of, the m e a n, lach flow and sedimentation process. On subsequent drying, it results in the development of, p, , ontinuous layer of closely packed soil particles The crust has high bulk density, lower macro, arosity and higher mechanical strength than below.,)Soil crusts often hinder the emergence of, po., d hence establishment of crop stand Effects of crust on soil and crop include:, eedlings and, , .Reduction in soil infiltration rate., .Increased runoff and erosion., .Impedance to emerging seedling., , .Injury, , to, , young seedling, , Management practices, , by, , of, , movement, , to overcome crust, , large, , blocks, , of crusts during, , cultivation., , problems include, , .Shallow and dense sowing., , .Dragging thorny branches on crusted soil surface., .Mulching., Light harrowing after rain., Planting on shallow furrows and on sides of ridges., , Vertisols, , characterised, , commonly called as black soils are, Important constraints for crop production are, soil, Physical constraints such as narrow range pf, become waterlogged and poor trafficability, N, available P., to, Low soil fertility due low and, These soils, , and, Land degradation from soil erosion, , by high clay content (30-70%)., , water content, , for, , tillage, tendency, , salt accumulation, especially, , in, , lowlying, , to, , areas., , Inceptisols and Entisols, , and, , holding capacity, have low, These are commonly termed alluvial soils. Theysoils for crop production is relatively, low nutrient holding capacity. )Management of these, to land, erosion is, however, a problem leading, Soil, black, and, soils., easy compared to red, degradation., as well as moderate, medium to, water, , as, , deep, depth is, These soils are, depth)., mm m, profíle, is, (300, high, In clay content. Moisture retention capacity, Due to high rainfall,, in high production system., in nitrogen. Phosphorous may be limiting, poOr, double cropping is possible in these soils., by the Ca CO, effective depth being influenced, soils,, depth)., Ierozems are extremely light, is low (150 mm m soil, capacity, holding, moistre, Concentration in soil profile. ts, Subsoil salinity, spmetimesyinadequate in phosphorous, and, loams Where post, sandy, rOZemie soils are low in nitrogen, in, deep, monsoon cropped except, n These soils are mostly, Submountain soils are medium, , in, , texture and, , Onsoon cropping is also possible. Crusting is very frèquent., , .2.3. LACK OF SUITABLE VARIETIES, , There are, , under, , im, , all the crops, is for crops, nprovement, in almost, rainfall., conditions of scarce, exclusively for, CLIes, , irtgacultivars, , As such,, , no, , pertorming

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PRINCIPLES OF AGRONOMY, , 272, , well under irrigation are not expressing their yield potential under undependable precipitation in, , dryland farming., 5.2.4. TRADITIONAL CULTIVATION PRACTICES, Most of the farmers practicing subsistence farming are adopting traditional cultivation practices, , evolved based on long term experience by their ancestors. Cultural practices such as tillage, without considering land slope, untimely sowing, sowing the seed by broadcasting, inadequate, nutrient supply, untimely weeding, low productive cropping systems, etc are still followed by, farmers, , leading, , to low, , yields., , 5.2.5. HEAVY WEED INFESTATION, This is the most serious problem in dryland areas.)Soil environmentideal for crop growthis also, congenial for weed growth. Weed seeds germinate carlier than crop seeds and suppressthe crop, , growth. Weed infestation is severe in dryland agriculture due to continuous rains and acute labour, shortage.) Since crop performance under dryland farming is unpredictable, farmers hesitate to, investment money for weed management leading to heavy loss in crop yield., , 5.2.6. SOCIO-ECONOMIC CONSTRAINTS, , The socio-economic status of dryland farmers, generally, will not permit them in adopting the, recommended dryland technology. Major socio-economic constraints are, ., , Lack of capital, support price for the produce, marketing and credit facilities make the, farmers hesitate to invest on recommended technology., , .Most of the resource p0or farmers opt for avoiding risk in dryland agriculture., .Poor organisational structure for input supply in dryland areas.

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-AET, , Amt, , o H0 thod s, , OAxtuoll, , SOUat by eyapoJoilion, , PE T, , SUUatAL by ET, , th, , todampiu, , Meoawe oh the obiity o, , aaaraassaxsaaaaoxxsaxaxsgaxasaussssxss.ac.cces335s3s33, , 462, , um. o d m, , almos to umove Ha0 o, AGRONOMY FACTS tor COMPETITIONC, , ham thee, , S amle M0, , Classification of rainfall zones in India, Net, , sown area, , Category, , Rainfall (mm), , Zone, , Very low, , s500, , Arid, , 16, , Low, , 500 750, , Semi-arid, , 17, , Medium, , 750, , Dry sub-humid, , 35, , High, Very high, , 1100 1400, , Moist sub-humid, , 24, , >1400, , Humid mountains, , 8, , 1100, , (), , pd. m whidh k, DNailosle doid moistoe, , Length of growing period, Crop growing period, Nil or slight water stress, , AET, , PET/2, , Moderate drought, , : PET/2 > AET> PET/4, , Severe drought, , PET/4> AET, , *AET, , PET, , Actual Evapotranspiration, , 30mmw Length, , of crop, , to m t the ET, , w emou, , uA, , dylomd rofa., , Potential Evapotranspiration, , growing, , season, , 4 mm, , Jaisalmer, Barmer, Jodhpur, Ganganagar and western Rajasthan, , Less than one month, , Normal growing season in northwest and arid zone, , 30-90 days, , Arid, , zone, , in southern, , peninsula, , 120 days, , Gangetic alluvial plains of UP and western Bihar, Interior, , peninsula, , India, , (except, , KR and, , adjoin, , TN, , Less than 180, more, , than 210, , days), , Less than 180, , Assam and some parts of Kerala, , More than 300, , Most parts of Assam, , 365 days, , days, days, days

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5.4. DROUGHT, Since time immemorial, mankind has lived under the threat of natural disasters. Amongst various, , hazards of nature,, , is the most disastrous. In the past, India had been a frequent victim, which resulted in famine deaths of large members of human and livestock., , drought, , pt disastrous droughts,, , Drought, thus, is a precursor of famine and undoubtedly man's worst natural enemy. Technological, , developments and natural efforts are fn progress to ameliorate the impacts of drought and being, about sustainability, , to, , agricultural productivity, , in the country., , Low rainfall or failure of monsoon rains is a recurring feature in India. This has been responsible, , famines. The word drought, generally, denotes scarcity of water in a region., Though ardity and drought are due to insufficient water, aridity is a permanent climatic featurey, and is thelculmination of a number of long term processes However drought is a temporary, , for droughts and

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condition that, , occurs, , for, , a, , short, , period due, , to deficient precipitation)for vegetation, river, , water supply and human consumption Drought is due to anomaly, , Drought, , is, , flow,, , atmospheric circulationy, , climatic, , anomaly, characterised by deficit supply of moisture resulting either, from subnormal rainfa!l, uneven, distribution, higher water need or a combination all the factors., Droughts lead to problems like widespread crop failure, unreplenished groundwater resources,, depletion in lakes/reservoirs, shortage of drinking water, reduced fodder availability etc., 5.4.1. DEFINITION OF DROUGHT, There is, , a, , universally accepted definition of drought. Early workers defined drought as prolonged, period without rainfall According to Ramdas (1960), drought is a situation when the actual, seasonal rainfall is deficient by more than twice the mean deviation American, Meteorological, Society defined drought as a period of abnormally dry weather, sufficiently prolonged for lack, of water to cause a severe hydrological imbalance in the area, affected., In general, drought means different things to different, peoplel To a meteorologist it is the, absence of rain while to the agriculturjst it is the deficiency of soilmoisture in the crop, root zone, to support optimum crop growth and productivity. To the hydrologist it is the, lowering of water, levels in lakes, reservoirs etc, while for the city management it may mean the shortage of, no, , drinking water availability Thus, it is unrealistic to expect a universal definition of drought for, , all fields of activity., Prolonged deficiency ofsoil moistureladversely affect crop growth indicating incidence of, agriculture drought It is the result of imbalance between soil moisture and evapotranspiration, needs of an area pver a fairly long period as to cause damage to standing crops and to reduce, , the yields.

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DROUGHT OR MOISTURE STRESS, Anlextended period of deficient rainfall compared to normal rainfall of the region is called, , drought Depending on, , the criteria, , used, drought is called as meteorological, agriculture or, hvdrological drought(Meteorological dröught refers to substantial deficit of rainfall relative, toaverage of the region. Indian Meteorological Department defines meteorological drought, , as a situation when there is a 25% decrease in the average rainfall_for a given period in_a, , region,Agricultural drought refers to extended dry period in which lack of rainfall results, n insuficient moisture in the root zone of the soil causing adverse effects on crops., , Hydrological drought is extended dry period leading to marked depletion of surface wáter, , and consequent drying up of reservoirs, lakes, streams, rivers, cessation of spring flows and, fall in groundwater levels., Based on extent of rainfall deficit, the terms like dry spell, drought and famines are, , USed.Dry spell is rainless peridd more than 10 days in light soils areas and 15 davs in

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434, , PRINCIPLES OF AGRONOMY, , heavy soil areas. Drought is prolonged dry spell resulting wilting-ordrying of crops. Severe, formdrought is called famine, Desertification is land deradation in arid, semiarid and dry humid areas resulting from, various factors including climate variation and human, activities) Desertification process mainly, , due to recurrent droughts, over grazing, reduction in, soil degradation and, reduction in water resources. The main effect of drought is reduction in crop, growth, reduction, in yield and/or crop failure depending on the intensity of, effects of, , Vegetation,, , Occurs, , drought., , drought are acute shortage of fodder and drinking water to livestock., , The other, , Soil moisture is the most limiting factor in dry farming and dryland farming situations, Understanding of the physiological processes that occur during moisture stress or droght, stress is necessary to ameliorate the stress, effects either by management practices or by plant, improvement.., , In biology, stress is the result of action of external factor on an, organism) Moisture, stress indicates the action of lack of or excess of water on plants. The, (term moisture stress, is, , generally used, , for, , deficit moisture conditions though, , also. Since moisture deficit, , it, , iS, , applicable to excess moisture, , is most prevalent under dry farming conditions, the effect of, moisture stress due to deficit is discussed in this chapter. Stress due to excessive moisture, is discussed under irrigation.

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DROUGHT, , Drought is a precursor of Famine, is, Aridity is a permanent climatic feature whereas, drought temporary, short period/because of insufficient rainfall to vegetation., -, , Drought is a situation, , when the actual seasonal, , condition occurs for a, a, , rainfall is dejicient by more than twice the, , mean deviation,, Drought Classification, Based on duration and nature, 1., Permanent drought: It occurs in a desert climate where agriculture is possible only by irrigation, in, 2., , a, , whole, , year., , Seasonal drought: It occurs in arid and semi-arid regions where rainy season and dry seasons, , are well defined., , 3.Contingent drought: It is the abnormal failure of rainfall. It especially occurs in humid, and sub-humid regions and usually affects small areas, 4 Invisible drought: It occurs when there is frequent rain in a region. When rainfall is insufficient, to meet ET loss, the result is borderline water deficiency.It occurs in humid regions.

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DRYLAND AGRICULTURE, , 463, , Based on user, , rieultural drought:, , nofranspiration, Support, , of, , It, a, , optimum growth, , According, , resulted from, , imbalance between available soil moisture, and, crop. This insufficient soil moisture in crop root zone does not, , and, , an, , development., , National Commission, , It is also, , known, , as, , soil drought., , Agriculture (1976), agriculture drought is defined as a, neriod of 4 successive weeks with a rainfall deticiency of more than 50% of LTA (long-term, to, , on, , average) during crop season (mid-May to mid-October) or 6 weeks during another season., , 2., , Atmospherie drought: lt is due to low atmospheric humidity accompanied by hot, dry winds, adequate so1l moisture., Hydrological drought: It resulted when depletion of surface water and consequent drying of, thereservoir, tanks, ponds, etc. it occurs when meteorological drought prolongs., even, , under, , Meteorological drought: According to IMD,, , it is, , a, , situation when the rainfall, , deficiency is, , 25%ormore of the LTA of a meteorological sub-station. It is categorized as moderate drought, Cif rainfall deficiency is between 26 to 50%) and severe drought (if rainfall deficiency is higher, than 50%)., , harvested due to, e.g., Cherapunjee in Meghalaya, , Sufficient water is there but could not be stored, 5 Economical drought:facilities, economic investments,, , lack of infrastructural, receives the, , highest, , poor, rainfall in the world but suffers from extreme, or, , or, , drought during the, , winter, , season., , unable to absorb water from the soil, due to the osmotic pressure of soil solution owing to increased, , Physiological drought: A condition where crops, , evenwhen water is available,, salt concentration, , as, , in saline, , and alkaline soils, , are

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Criteria of Drought, In, , India various states, , and, , official commission have, , droughts., , adapted different criteria for classifying, , Irrigation Commission, while adopting the, IMD classification of Meteorological, hased on departure of annual rainfall from, drought, normal,, considered, those, which, regions, experienced, drought in 20 per cent of years as drought areas and those, which, arça, experienced drought in, more than 40 per cent ot the years as, chroniç drought areas, , National Commission on Agriculture (1976) considered, agricultural drought as an occasion, when at least four consecutive weeks receive, fainfall half of the normal (normal rainfall, being, 5 mm or more) during the crop season, (mid-May to mid-October) or six such weeks during other, period., The criteria adopted in different states also, vary depending on the rainfall and crops grown, in the region. Tamil Nadu considers region, receiving less than 900 mm rainfall as drought, while, affected,, Karnataka considers regions, rainfall less than 400 mm, , less than 30 per cent, stages of crop growth, , scarcity, , receiving, , during crop, as, , year when the, , season, , drought affected, , and 20 per, areas., , cent, , Rajasthan, , deficiency, on, , during kharif and, during crucial, considers an yea, , of rainfall, , the other hand, , productiyity, , decrease by 50 per cent compared to a good crop year., Many of the states also follow the Annawary" system wherein the crop conditions are assessed, through visual estimates. The criterion followed is, , as, , Production above 75 per, Production 50, , cent, , of normal, , 75 per cent of normal, Production 25 to 50 per cent of normal, to, , drought., Moderate drought., Severe drought, , No, :, , Production less than 25 per cent normal: Disastrous drought., Besides rainfall, various other climatic and soil factors have also been used for drought, , classification.(These include the aridity index (la) anomaly and ratio of actual to potential, evapotranspiration (AE/PE) Studies at CAZRI categorised drought based on moisture stress, during crop growing seasoD using the following criteria :, , rought, , free, , period, , :, , When cumulative AE, , oderate drought period, PE4 curves, , When cumulative AE, , is above cumulative PE/2, , curve, , curve., , lies between cumulative PE/2 and, , below cumulative PE/4 curve., Hence, a novel method, lmpact of drought depends on the phonological state of crop growth., values ot AE, classification of agricultural droughts was attempted at CAZRI, considering the, , Severe drought period, of, , :, , curve, , :, , When cumulative AE, , curve, , is, , E during different phenophases of crop growth as indicated in Table 5.0.

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Impact of Droughts, , is felt is agriculture. With increased, One of the sectors where immediate impact of drought, a significant fall in food production is often, of, duration, prevalence,, extended, or, drought, intensity, noticed. Drought results in crop losses of different magnitude depending on their geographic, at, but also, incidence, intensity and duration. Drought not only affects food production farm level, national economy and overall food security as well. Besides shortage of food and drinking water,, impact of drought is also felt due to, , Deficit groundwater recharge., Non availability of quality seed., Reduced draught power for agricultural, , operations, , due to distress sale of cattle., , .Land degradation., ., , Fall in investment, , capacity, , of farmers for further investment in, , agriculture.