Lecture 7: Water Management Flashcards
WATER MANAGEMENT
- time application of needed water
- removal of excess water
EFFECTS OF LACK OF WATER
- poor crop stand
- stunted growth
- yield reduction
- pest/diseases
- nutrient deficiency
TOMATO BLOSSOM END ROT
- calcium deficiency (lack of water)
EFFECTS OF EXCESS WATER
- nutrients leaching from soil
- high acidity of soil
- water-logged condition
- lack of oxygen causing root death
- root-rotting pathogens
EXAMPLES OF ROOT-ROTTING PATHOGENS
- Phytophthroa
- Pythium
- Rhizoctonia
- Fusarium
EFFECTS OF FLUCTUATION IN WATER SUPPLY
- fruit cracking (tomato, mango, banana, carrots)
PURPOSE OF IRRIGATION
- timing and frequency of irrigation
- adequate supply of water
- efficient method
FACTORS AFFECTING IRRIGATION PROGRAMS
- soil factors
- climate factors
- plant factors
IRRIGATION: SOIL FACTORS
- soil texture, structure, depth
- affects WHC, water percolation
IRRIGATION: CLIMATIC FACTORS
- temperature, length and intensity of sunlight, relative humidity, wind movement
- affects rate of water loss (evaporation and transpiration)
IRRIGATION: PLANT FACTORS
- rooting characteristics, drought tolerance, growth stages
DROUGHT RESISTANCE
- dictated by genetics
DROUGHT TOLERANT CROPS
- siniguelas
- cashew
- mango
- tamarind
DROUGHT-SUSCEPTIBLE CROPS
- banana
- lanzones
- durian
- papaya
- cacao
STAGES AFFECTED BY WATER STRESS
- early vegetative growth
- flowering
- fruit setting
- fruit development
FLOWER INDUCTION
- triggered by application of irrigation after brief drought
- durian, rambutan, citrus, lanzones, coffee
METHODS TO DETERMINE IRRIGATION SCHEDULES
- available soil moisture
- evapotranspiration rate
- visual symptoms of plants
- feel of soil
- soil-cum-sand mini plot technique
IRRIGATION SCHEDULE DETERMINATION: SOIL MOISTURE
- gravimetry: oven drying and computing for soil moisture content
- tensiometer: measure water potential; inversely proportional to amount of available water
THRESHOLD LEVEL IN ESTIMATING AVAILABLE SOIL MOISTURE
- 50% of available water
IRRIGATION SCHEDULE DETERMINATION: EVAPOTRANSPIRATION
- use of evaporative pan
- applied over short time intervals
IRRIGATION SCHEDULE DETERMINATION: VISUAL SYMPTOM
- temporary wilting
- color of foliage
IRRIGATION SCHEDULE DETERMINATION: SOIL FEEL
- sandy: dry; doesn’t form ball
- loam: crumbly; particles hold together
- clay: pliable; forms ball; doesn’t form ribbon
IRRIGATION SCHEDULE DETERMINATION: SOIL-CUM-SAND TECHNIQUE
- choose 2-3 hills from representative section
- dig pits of 1 cubic meter
- add 5% sand to soil and return mixture to pit
- plant seedlings
- limiting soil moisture: wilting of seedlings 2-3 days ahead
METHODS OF IRRIGATION
- surface irrigation system
- sprinkler irrigation
- drip system
- sub-surface irrigation system
SURFACE IRRIGATION SYSTEM
- furrow method
- flooding method
- basin method
SURFACE IRRIGATION: FURROW METHOD
- row crops (corn, peanut, banana)
- uniform gentle slopes (0.25-2.5%)
- windy areas
- abundant water
SURFACE IRRIGATION: FLOODING METHOD
- lowland rice
- closely planted upland crops
- flat areas
- windy areas
- abundant water
DISADVANTAGE OF FURROW AND FLOODING METHOD
- inefficient
- weed growth
- limited application
SURFACE IRRIGATION: BASIN METHOD
- crops planted far apart (tree)
- more efficient
- flat to steep slope areas
SPRINKLER IRRIGATION
- highly pressurized water
- use of network of pipes
- fine droplets of water
ADVANTAGE OF SPRINKLER IRRIGATION
- sandy soil
- flat to steep slope areas
- more efficient
- temperate reduction
DISADVANTAGE OF SPRINKLER IRRIGATION
- high initial investment
- high operating cost
- water distribution affected by wind
- diseases and wind growth
- high evaporation losses
DRIP SYSTEM
- use of network of pipes
- drips as water output
- water applied directly to root zone
- continuous supply of small amount of water
ADVANTAGE OF DRIP SYSTEM
- wide application
- highly efficient
- combines irrigation and fertilization
DISADVANTAGES OF DRIP SYSTEM
- high initial investment
- clogging of nozzles
SUB-SURFACE IRRIGATION SYSTEM
- applied below soil surface
- reacher plant root system by capillary movement
- potted indoor plants; greenhouse plants
SOURCES OF IRRIGATION
- river, stream, lake (dam; pumping)
- farm reservoir
- water impounding system
- ground water (open well; tube well)