Common plant watering mistakes made by home growers
Plant watering is a frequent action required to keep plants healthy and support their growth. As such, wrong practices can have a profound negative effect on plants. The good news is that these can be corrected very easily. Based on the experience we have in supporting growers on the Agrio app, we list the most common mistakes we encounter and explain how to avoid them.
Prolonged periods of wet soil
When it comes to soil moisture, it is easy to get it wrong. When the soil is wet, the process of gas exchange in the roots cannot take place at normal rates. If the gas exchange process is being interfered for a long period It can cause injuries to the roots. Soil moisture is also a crucial factor when it comes to soil-borne disease triggering. The presence of standing water will promote such diseases.
Dry soils on the other hand, can cause damage as well. The balance might be tricky when the environment is not monitored constantly.
Before we discuss a simple approach to monitoring water requirements, let’s discuss the factors that affect water availability.
Evapotranspiration is a process in which water vapor is released into the atmosphere from the soil, leaves, and other surfaces. It is one of the ways in which water moves from plants to the air.
Evapotranspiration is a major contributor to water cycling in the global hydrologic system. The rate of evapotranspiration depends on many factors such as plant type and cover, temperature, humidity, wind speed, solar radiation, soil type, and depth. In essence, the water that we provide to the plants should compensate for the water that was lost in the evapotranspiration process.
Evapotranspiration can change considerably when the weather changes, or when we change the plant location. There is no simple way to predict a watering schedule if environmental factors are not monitored.
Overwatering and poor soil drainage
One of the main reasons for prolonged times of wet soil is overwatering. If the watering rate is above the plant needs, accumulation of water in the plant’s surroundings can happen.
When water has nowhere to go, the soil can dry itself based on evaporation. But the rate is many times not sufficient.
One common mistake we encounter is the lack of holes at the bottom of the pot. This includes situations in which the holes are blocked by stones that made their way to the bottom of the pot with time.
When selecting the container you are going to use, make sure it contains holes that allow good soil drainage, and occasionally check to see that the holes are not blocked. It is a good practice to re-pot once a year to prevent soil compaction that can contribute to poor soil drainage and root development.
Excessive water should be removed soon after the plant’s watering is finished. This is important when the pot is placed inside a tray that collects the excessive water. The tray serves as a water reservoir if not emptied. The water from the tray is pulled back into the pot, not allowing the soil to dry and keeping it wet for longer than we intended.
Why container size affects soil drainage
When the plant is still small and the roots don’t spread to the entire soil volume, the drainage is poor. You can think about the soil sections that are not reachable by the plant roots as water reservoir. Therefore, it is important to start with a small pot. The small pot will constrain the size of the roots and will not allow the plant to reach its full potential. Therefore you should re-pot once the plant grows.
If you didn’t follow the watering rules we just discussed, you might be able to get a warning sign before the situation gets out of control. You will often see fungal growth on the surface of the soil. This might indicate that the soil moisture stayed high for too long time.
When the weather becomes hotter, you might forget to adjust the watering volumes. This can result in poor water conduction to the foliage that, in turn, will show up as a tip burn or wilt of the plant. When the plant is exposed to direct sunlight, the early symptoms can be sunburns due to the poor ability of the plant to cool itself.
Soil that stays dry for a long time will cause injuries to the roots, which are often irreversible.
How to decide when to water plants
As a rule of thumb, the plant should be watered whenever the top 3 inches (roughly 10 cm) of the soil dry out. Use your fingers to feel the soil moisture level and decide if watering is needed. Note that If the soil is still wet after 7 days since the last watering, there might be a problem with the drainage.
Salinity and plant watering
Salinity is the total concentration of the ions in a medium. Ions concentration goes up when salts are dissolved. High concentrations of different salts can cause problems. High concentrations of sodium chloride can have a devastating impact on seed germination and create osmotic stress causing plants to become water deficient. High concentrations of sodium chloride can also cause ion imbalances and toxicity seen on older leaves as burned tips, which can develop into more extended necrosis.
Check the level of salts in the designated soil before planting. Plan in advance, considering crop susceptibility to sodium chloride, soil structure, and characteristics, and the quality of your water source. If necessary, initiate preventive measures that can improve overall drainage or initiate several pre-planting, high-volume irrigation executions to wash and push aside salts.
Regularly search for visual symptoms of salinity, especially after heavy rains. Look for white-colored patches on the soil. This will improve response times to prevent serious damage from occurring.
How to check the salts concentration in the soil and water
Measuring devices are available in gardening stores to help you test the electrical conductivity of the soil and water. The electrical conductivity is proportional to the concentration of dissolved salts in the medium.
Avoid tap water when salts concentration is high
Very often, tap water is not a good source for plant irrigation. Tap water might contain heavy fluoride and chlorine that can aggregate in the soil and become toxic to plants. Tap water can also have a high pH that will cause an undesirable change to the soil pH in the long run. Rainwater should be the preferred option. It is common practice to aggregate rainwater in barrels during the winter and use them to irrigate plants all year.
Reverse water osmosis filters can be used to remove salts from tap water if rainwater is not a viable option.
As a last resort, put water In open containers for at least 24 hours to get rid of the fluoride. Unfortunately, this approach will not change the chlorine content in the water, and therefore it should not be the preferred approach to preprocess the water.
Prevent salt accumulation in the soil
To reduce the salt accumulation in the soil, don’t stop watering until water starts to come out from the bottom of the pot. This will allow the water to dissolve salts and remove them from the roots zone.
Overhead irrigation and increased disease risk
You might be tempted to stand in the middle of the garden and water your plants with a hose. It is a convenient way to cover the entire garden fast. But this approach is not recommended.
Overhead irrigation increases the leaf moisture and might cause a spread of pathogens from the soil to the plants.
Generally speaking, leaf wetness makes the environmental conditions more favorable for bacterial, fungal, and oomycete pathogens. By pouring the water on the soil, we can make sure that the leaves stay dry and decrease the risk of disease development.
Splashing water from contaminated soil
Another risk factor for disease development is the potential transfer of pathogens from the soil to above-the-ground plant parts. Water splashing can be how pathogens find their way from contaminated soils to stems, foliage, and fruits. Avoiding overhead irrigation is one way to lower this risk. Growers can also cover the soil with polyethylene or mulch to lower the risk even further.
With a few simple practices, you can ensure that your plants get an adequate amount of high-quality water. We are looking forward to welcoming you to our community and supporting you with any questions you might have regarding plant watering and plant health. In the meanwhile, as always, we wish you an abundant harvest.