• Growing of crops entirely under rainfed conditions is known as dryland agriculture.
• Pitcher farming is a practice in dry farming where crop is irrigated through small holes made in the bottom of earthen pitcher. The practice is generally used for wider spaced plants.
• Cultivated land in India = 142 mha
• Dryland area = 34.5 mha (24 %)
• Rainfed area (including flood prone area of 15 mha) = 65.5 mha (45.5 %)
• Irrigated area = 43.8 mha (30.5 %)
• Per cent area under rainfed and dryland = 69.5 %
• Dryland contributes 42 % of total food grains.
• All coarse grains, 75% of pulses and oilseeds, two thirds of mustard, most of soybean and groundnut are grown under rainfed condition.
• First famine commission was appointed in 1880.
• Important recommendation of the first famine commission was to provide facilities for protective irrigation.
• Systematic research work was started from 1923 with the start of research centre at. Manjre near Pune
• In 1933, research stations established at Bijapur and Sholapur.
• In 1934 research stations established at Hagari and Raichur.
• In 1935 research station established at Rohtak.
• In 1944 Monograph on dry farming in India by Kanitkar.
• In 1953, establishment of Central Soil Conservation Board.
• During 1954, the soil conservation training and demonstration centres were established by ICAR at 8 locations.
• During 1970, ICAR started AICRP on Dryland Agriculture at 23 locations spread all over India.
• In 1972, ICRISAT was established.
• In 1976, establishment of dryland Operational Research Projects (ORPs).
• In 1983, 47 model watersheds were developed. In 1985, CRIDA was established.
• Extended period of deficient rainfall compared to normal rainfall of the region is called drought.
• Drought can be classified based on duration and nature of users.
• Meteorological drought refers to substantial deficit of rainfall relative to average of the region.
• IMD defines meteorological drought as a situation when there is 25% decrease in the average rainfall for a given period in a region.
• Atmospheric drought is due to low air humidity, frequently accompanied by hot dry winds. It may occur even under conditions of adequate available soil moisture.
• Plants growing under favourable soil moisture regime are usually susceptible to atmospheric drought.
• Agricultural drought refers to extended dry period in which lack of rainfall results in insufficient 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 water and consequent drying up of reservoirs, lakes, streams, rivers, cessation of spring flows and fall in ground water levels.
• Permanent drought is the characteristic of the desert climate where sparse vegetation growing is adapted to drought and agriculture is possible only by irrigation during entire crop season.
• Seasonal drought is found in climates with well defined rainy and dry seasons. Most of the arid and semiarid zones fall in this category. Duration of the crop varieties and planting dates should be such that the growing season should fall within rainy season.
• Contingent drought involves an abnormal failure of rainfall. It may occur almost any where especially in most parts of humid or sub humid climates. It is usually brief, irregular and generally affects only a small area.
• Invisible drought can occur even when there is frequent rains in area. When rainfall is inadequate to meet the evapotranspiration losses, the result is borderline water deficiency in soil resulting in less than optimum yield.
• Invisible drought occurs usually in humid regions.
• Dryspell is a rainless period more than 10 days in light soil areas and 15 days in heavy soil areas.
• Drought is prolonged dry spell resulting in wilting or drying of crops.
• Severe form of drought is called famine.
• Desertification process mainly occurs due to recurrent droughts, overgrazing, reduction in vegetation, soil degradation and reduction in water resources.
• Though there is sufficient amount of soil moisture, water deficits develop due to higher transpiration than absorption especially on hot mid days. This temporary wilting is known as incipient wilting or mid day depression.
• Stomatal closure occurs when leaf water potential approaches about -1.0 to -1.2 MPa or -10 bars to -12 bars.
• If soil moisture depleted to a level of -6 MPa (-60 bars), plants die permanently and this is known as ultimate wilting point.
• Moisture stress reduces photosynthetic rate due to reduction in CO2 entry, decrease in mesophyll conductance, due to stomatal resistance.
• Reduction in photosynthesis due to moisture stress is mainly by the reduction in leaf area than by photosynthetic rate.
• Decreasing the tissue water potential by only – 0.1 MPa (–1 bars) or less result in a perceptible decrease in cellular growth while photosynthetic rate is affected only at –1.6 MPa (–16 bars).
• Translocation of assimilates is affected by water stress, resulting in assimilate saturation, there by leading to reduction in photosynthesis.
• Drought stress induces oxidative damage due to release of free radicals.
• Activity of superoxide dismutase and catalase increases in response to moisture stress.
• Respiration increases with mild stress.
• Respiration decreases under severe water deficit.
• Stomata per unit leaf area tend to increase under moisture stress.
• Severe water deficits cause decrease in enzymatic activity. Peroxidase activity decreases.
• Enzymes involved in hydrolysis increase resulting in breakdown of starch and protein.
• Accumulation of sugars and amino acids takes place under moisture stress.
• Proline, an amino acid accumulates under moisture stress.
• Under moisture stress activity of growth promoting hormones like cytokinin, gibberellic acid and indoleacetic acid decreases.
• Growth regulating hormones like abscisic acid, ethylene, betaine etc. increases under moisture stress.
• Translocation of growth promoting hormones is also reduced by moisture stress.
• Abscisic acid content is inversely related to leaf water potential.
• Abscisic acid acts as water deficit sensor to minimize the loss of tissue water potential.
• Abscisic acid controls stomata and thus reduces water loss when there is moisture stress.
• Ethylene production due to moisture stress is the cause for leaf and fruit drop.
• Betaine produced by moisture stressed plants is an indicator of moisture stress.
• Moisture stress affects nitrogen fixation, uptake and assimilation
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