Importance of phosphorus in hydroponic cultivation
Introduction
If you are looking for the optimal concentration of phosphorus for plant growth in hydroponics, you will probably find very different results from low to very high. This is inherently contradictory and difficult to understand, why do we not have a lower range for optimal P conditions? Why has it been so difficult to describe the best P levels? Today we will talk about phosphorus nutrition and why there is so much confusion about optimal phosphorus levels in hydroponic cultivation.
Almost all books on hydroponics and flowering plants put the optimum concentration of phosphorus in the solution between 20 and 50 ppm. They play well. Concentrations of nutrients used for other elements However, you will find articles on various plants that recommend P levels, which can range from 200 ppm to 10 ppm. Consider this article on Calendula, which recommends the use of P 10ppm, while this article on Lavender 60ppm. Note that optimal phosphorus may also depend on the desired result, as this article on Origanum dictamnus shows that essential oils move from leaves to brackets at higher concentrations of phosphorus in these plants.
Not only is there confusion about optimal phosphorus levels, but even the effects of phosphorus and the interaction of phosphorus with micronutrients are not well understood. There is evidence (see here) that phosphorus increases the uptake of manganese in tomatoes while suppressing the uptake of iron and zinc, while we have very different results in the atmosphere, where P actually inhibits the uptake of manganese. It becomes. The above two articles also have many references to the P absorption literature, which I suggest you review if you would like to know more.
The P literature is very extensive (I suggest you read this dissertation and its sources if you want to dig deeper), but in general we know that concentrations below 20 ppm are rarely optimal and we know that levels above 60 ppm are Can be optimal. Some plants under certain conditions in the thesis mentioned above we see that the Tabasco pepper plant after 90 days in phosphorus solution has about 120 ppm highest leaf area.
Assessing optimal phosphorus levels may be more difficult because it depends on the concentration of other elements in the solution as well as the pH of the solution and the temperature of the root zone. We know that low phosphorus stimulates root growth and reduces stem growth, while higher phosphorus levels have exactly the opposite effect. Therefore, changes in the ratio of phosphorus to other nutrients may be the optimal path for many crops, but it is very difficult to generalize because it depends on the specific growing conditions of each particular crop that is growing.
Unfortunately, the answer is that we do not have an “optimal P” that is compatible with all growing conditions and plants. We know that growth with a P value between 30 and 50 ppm gives you good results in almost all crops, but we also know that by optimizing P under specific growth conditions (plant, environment, temperature, etc.) Significant achievements can be achieved. ). In some cases, a 50% + increase in yield may be possible if the P is properly adjusted to the exact growth conditions used.
Your optimal P may be much lower or higher than what is recommended in the literature, so start with the ballpark literature recommendation and perform experiments from there to properly adjust the P to maximize the product. Also make sure that you do leaf tissue, media and runoff analysis while doing this to make sure you get the best results possible.
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