Water and irrigation Soil infiltrationSoil infiltration –Clay = slow –Sand = fast
Water and irrigation Soil water retentionSoil water retention –OM and clay = high –Sand = low Gravitational water = ground water (well water)Gravitational water = ground water (well water)
Water and irrigation Field capacity = maximum amount of water that a soil can hold against the force of gravityField capacity = maximum amount of water that a soil can hold against the force of gravity Capillary water = available to the plantCapillary water = available to the plant Wilting point = point at which a plant is unable to take up additional water from the soilWilting point = point at which a plant is unable to take up additional water from the soil Hygroscopic water = water not available to the plantHygroscopic water = water not available to the plant
Water and irrigation Water and plant growthWater and plant growth –Leaves 65% water –Roots 70% water –Fruits 85% water Melons 95% water !Melons 95% water ! Water is a solvent in plants that helps to dissolve mineral nutrients and sugars and to transport themWater is a solvent in plants that helps to dissolve mineral nutrients and sugars and to transport them
Water and irrigation Turgid = plant parts filled with waterTurgid = plant parts filled with water Wilted = lack of turgidity!Wilted = lack of turgidity!
Rule of Thumb 1 of water is needed per week during the growing season
Water and irrigation Excess soil moistureExcess soil moisture –Lack of aeration, root cells cant function well –Result is wilted foliage! –Diseases Fungal and bacterialFungal and bacterial Damping-off (a fungal disease)Damping-off (a fungal disease)
Water and irrigation - problems Excess humidityExcess humidity –Fungal spores germinate on foliage and fruit Botrytis
Water and irrigation - problems Excess humidityExcess humidity –Guttation
Water and irrigation - problems Excess rainfallExcess rainfall –Cracking of sugar-rich crops like cherries and tomatoes –You should not overhead irrigate these fruits when they are close to harvest! –Erosion –Leaching of mineral nutrients –Anaerobic respiration produces alcohol in water-logged roots
Water and irrigation - problems Water deficiencyWater deficiency –First symptom is gray foliage (esp. ferns) –Leaves and stems wilt –Leaves curl and drop off –Fruits wither and drop –Plants often experience temporary wilting in summer (leaves transpire more than roots take up!). Esp. on vine crops with large leaves
Water retention crystals Hold 200x their weight Potassium co-polymer Break down over 3-5 years
Water Quality PollutantsPollutants –Algae blooms from excess phosphorus in surface water –Depletes oxygen from the water at night and kills fish!
Water Quality Hard waterHard water –High concentration of dissolved minerals (often found in well water) –Water softeners replace calcium and iron with sodium chloride (table salt) which is damaging to houseplants!