Water quality management in plug seedlings and flower production
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July 30 10:15:32, 2025
Water quality plays a crucial role in the production of plug seedlings and flower grasses. Many issues that growers face are directly linked to the quality of water used for irrigation. This article aims to provide a comprehensive overview of common water quality problems, helping growers better understand the characteristics of their local water supply and how to manage it effectively for optimal plant growth.
One of the most significant factors affecting plant health is the alkalinity of irrigation water. Alkalinity is primarily determined by the presence of calcium carbonate, which acts like lime in the water. High-alkalinity water can raise the pH of the growing medium over time, leading to potential nutrient imbalances and poor root development if not managed properly.
The main components contributing to alkalinity include calcium carbonate, magnesium carbonate, and sodium carbonate. While plants require calcium and magnesium for healthy growth, excessive sodium can be harmful. In many cases, the levels of these minerals in the water may not be sufficient, so additional supplementation is often necessary.
For example, during seedling production, an ideal calcium concentration in irrigation water ranges from 60 to 80 ppm, while grass cultivation requires 80 to 120 ppm. Growers with low-alkalinity water should note that this is generally favorable, as it won't cause pH increases. However, such water lacks buffering capacity, making it more susceptible to sudden pH drops when acidic fertilizers are applied. Maintaining a pH above 5.5 is essential, as lower values can lead to trace element toxicity or calcium deficiency.
Plants like marigolds, geraniums, and impatiens are particularly sensitive to these issues. If calcium levels fall below 20–30 ppm, it's advisable to supplement with calcium-containing fertilizers. Gypsum (calcium sulfate) is a good option, as it adds calcium without significantly affecting pH. It also provides sulfur, which many plants lack. However, gypsum has a high salt content, so its impact on electrical conductivity (EC) should be monitored.
Similarly, magnesium deficiencies can be addressed using magnesium sulfate or by adding small amounts of magnesium sulfate heptahydrate to irrigation water. Boron is another critical nutrient; a recommended concentration is 0.06 grams per liter, though adjustments should be made based on specific conditions.
When dealing with high-alkalinity water, acids like citric, sulfuric, and nitric acid can be used to neutralize excess calcium carbonate. Citric acid is popular due to its organic nature and minimal harm to plants, though it can form complexes with other substances, requiring careful dosing. Sulfuric acid is commonly used but must be handled with care due to its corrosive nature. Nitric acid offers a balanced approach, promoting calcium absorption without causing leaf spotting.
Calcium, magnesium, sodium, and boron are key elements to monitor in both water and plant tissues. These nutrients form the basis of a successful fertilization plan. For most plants, tissue analysis shows calcium levels around 2% and boron around 75 ppm. Proper management of these elements ensures strong root development and overall plant health.
Some commercial fertilizers, like 20-20-20 or 20-10-20, lack calcium and may lead to deficiencies. Additionally, high phosphorus content in some fertilizers can interfere with calcium uptake, causing symptoms of calcium deficiency. Growers should choose fertilizers carefully depending on the crop needs and environmental conditions.
Other factors, such as soluble salts, also affect plant growth. High EC levels can be toxic to sensitive seeds, especially in early growth stages. Measures like leaching, reverse osmosis, or changing water sources may be necessary.
Water temperature is another consideration. For certain species like Impatiens, a temperature between 18°C and 21°C is ideal. Lower temperatures can cause uneven growth, while warmer water can aid in seed coat removal, improving germination and root development.
Finally, a summary table outlines key water quality parameters, including sodium adsorption ratio (SAR), which reflects the balance between sodium and other cations. Sodium can interfere with calcium and magnesium uptake, negatively impacting root growth. Understanding these factors helps growers make informed decisions about water and fertilizer management.