YOU WANT WET PLANTS , NOT SOAKED PLANTS
Overwatering is a common mistake that can lead to pythium and other pathogens invading plant tissue .
process of transpiration from the larger leaf surface area and more nutrients are required in the root zone . Recent transplants may only require one or less irrigations per day , while a mature tomato plant may need as many as six to eight depending on environmental factors . Since most of the water supplied to substrate-based crops is lost through leaf transpiration , the growing environment is largely what drives irrigation requirements . Plants grown under low humidity with a high rate of transpiration will need significantly more frequent and larger irrigations than those under high humidity and low temperatures with minimal water lost from the foliage . Temperature , root size and health , and light also play a major role in plant irrigation requirements . This is why automatic irrigation programs are often linked to the measurements of environmental factors .
Symptoms of Incorrect Irrigation Scheduling
Most growers are familiar with the symptoms of underwatering or irrigation failures — plants typically wilt rapidly in the restricted root volume of a hydroponic system if the irrigation fails .
Longer term , slight under-watering may have very minimal effects , apart from smaller or shorter than normal plant size , as plants have the ability to adjust to the moisture status in the root zone to a certain degree . Chronic underwatering , however , may look like nutrient deficiencies , particularly of calcium , which moves within the transpiration stream of the plant . It may also lead to reduced growth and yields as photosynthesis is restricted when plants shut down stomata to conserve moisture . Waterstressed plants may also be more prone to pests and diseases and other physiological disorders . Overwatering is a far more common occurrence in hydroponic systems than underwatering and can have severe implications for plant health . The number one cause of pythium and other
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Overwatering is a far more common occurrence in hydroponic systems than underwatering and can have severe implications for plant health .” root rot pathogen infection is roots that have become damaged by oversaturation and the subsequent root suffocation this causes . Root zone saturation can be difficult to diagnose in the early stages , as symptoms like wilting , or epinastic leaf drooping during the warmest time of day , foliage yellowing and leaf drop , may appear very similar to water-stressed plants . However , unlike water-stressed plants , oversaturated root zones do not respond to increasing the volume or frequency of irrigation , and often by this stage , root dieback and browning can be seen .
Manual Methods of Irrigation Control
The volume of nutrient to be applied or irrigation schedule to be followed is typically based on each grower ’ s particular crop , substrate and environment , and needs to be adjusted over time as plants develop . For this reason , using recommendations for set irrigation times and duration of nutrient application should only be considered a starting point . Irrigation determination in hydroponic systems may be manual or automatic . Many smaller indoor and greenhouse growers base decisions on when and
54 Maximum Yield USA | October 2016