Nutrient solution is the basis for the full plant growth with drip irrigation. Currently, drip irrigation is widely used in greenhouse vegetable growing with various automated irrigation systems. One of the components of successful operation is the proper preparation of nutrient solution.
Let’s look at this process in detail, since it is the basis for the exact parameters of the nutrient solution entering the plants.
HEDP аcid functions for nutrient solution
There are two ways to make a nutrient solution. One is based on complex fertilizers, the other one is adding of extremely simple fertilizers. It is very important to take into account that fertilizers must be completely water soluble and not contain ballast impurities, when selecting fertilizers. If you decide to use simple domestic fertilizers then you need to provide the acquisition of HEDP аcid. This acid should be used in small quantities (400-800 g / 1000 L of the nutrient solution depending on the chemical composition of irrigation water) and it performs four functions:
• facilitating the absorption of nutrients by plants, forming metal chelates (as a chelating reagent),
• improving the solubility of fertilizers and obtaining a clear solution,
• increasing the concentration of the nutrient solution (very important for the summer),
• prevention of the mineral salts deposition in drippers and pipelines, which extends the life span of the irrigation system.
When designing drip irrigation systems, it is necessary to provide the installation of a preliminary solution preparation unit, where the process of preparing the nutrient solution begins.
How to prepare a nutrient solution for drip irrigation?
Presumably, we need to prepare 1000 liters of the nutrient solution using simple domestic fertilizers. We can do it as follows:
- Pour 500 liters of hot water into the tank for preliminary solution preparation and turn on the mixer gear motor.
- Add acid.
- Add HEDP acid, if we have tank B which includes potassium sulfate, which is the most insoluble fertilizer. When using imported complex fertilizers, we don’t need HEDP acid, since it is already part of fertilizers.
- Add fertilizers starting with the most insoluble.
- Pour the finished solution through the filter (130 microns) into the main tank of the irrigation unit after thorough mixing using a special pump.
- Rinse the pipeline from the tank for preliminary solution preparation to the main tank by adding water to the vacated tank for preliminary solution preparation and using the same pump.
- Prepare separately a solution of micro-elements (e.g. in a bucket) and pour it into the tank with the nutrient solution. It is better not to use a tank for preliminary solution preparation to avoid the slightest loss of micro-elements in this case.
- Bring the level of the nutrient solution by adding water to the level of 1000 L in the main tank.
In order to achieve better acidity control of the nutrient solution, it is recommended to add acid in the nutrient solution the way when the pH is 6.0 by preparing the solution (without turn on the acid tank). For achievement a given pH of 5.5-6.0 the acid tank should be turn on.
It is necessary to monitor the acidity of the nutrient solution into which the metal chelate is added, since the solution maintains its stability at a pH value which is determined for each type of chelate. Usually, it is enough to add 3 liters of 58% nitric acid into the tank when using Fe chelate DTPA (the pH of the solution is 3.5-4.0). All the remainder of acid required by the calculations is added to another tank.
How to check the quality of the solution?
The agronomist can always control the solution quality after the solution is prepared. Add 10 ml of solution A and 10 ml of solution B to one liter of water, mix and measure the EC and the pH of the resulting solution. The result of measurements should correspond to the calculated indicators.
By calculating the quantitative composition of the solution, you should take into account the correspondence of the concentration of the nutrient solution and the specified EC parameter. For the operation stability of the mixer, it is better that the difference between the calculated and set EC parameters is within 0.5 mSm / cm. For example, if the nutrient solution is diluted of 1: 100 and has an EC = 2.5 mSm / cm, then this solution can be used in the range of 2.0-3.0 mSm / cm.
The solution quality also affects the duration of its use. This fact must be taken into account (especially in periods with a low consumption of the solution) and you have to prepare such an amount of the solution that will be used up in no more than a week. Solution tanks must be lightproof and must be closed with lids and kept clean.
Thus, a correctly calculated and prepared nutrient solution will ensure reliable operation of the mixer, it will ultimately create the conditions for proper plant nutrition in the greenhouse and will exactly lead to increased yields.
Our company has developed a computer software «Agronomist» that can bring clarity to the work related the calculation of nutrient solution.