Submission Procedures for Root Medium, Water, Fertilizer Solution, and Plant Tissue Samples 6/98 HIL-560 Brian E. Whipker Floriculture Extension Specialist

Providing the proper nutrition program for your plants is important for controlling growth. Sampling the root medium or plant tissue is a simple check of the nutritional status of the crop and can provide clues about a crop's performance before deficiency or toxicity symptoms appear. Plant leaf-tissue analysis is especially useful when one needs to determine micronutrient levels in the plant. Testing your irrigation water provides information on pH, electrical conductivity (EC), and alkalinity levels. High alkalinity can significantly increase the root medium pH over time. The pH of your root medium dramatically influences the availability of various nutrients to your plants. In addition, growers may want an analysis of their fertilizer solution to double check their mixing procedures or to check the calibration of their injectors.

 The purpose of this leaflet is to provide instructions to growers for taking representative samples for laboratory analysis. A selected list of labs specializing in greenhouse root medium, irrigation water, fertilizer solution, and plant tissue samples is provided in Table 1.

Conducting routine medium analysis is essential in determining the nutrient status of your crop. It is recommended that samples be sent to a lab every 3 to 4 weeks to check nutrient levels. A standard analysis usually includes: pH, EC, NO₃-N, NH₄-N, P, K, Ca, and Mg. In some cases growers may also want to test for sulfur and micronutrients (S, B, Cu, Fe, Mn, Mo, and Zn) in their media. Generally, testing for micronutrient concentration in the root medium is recommended only under special circumstances and not for routine analysis. Plant tissue analysis is a better indicator of micronutrient concentration.

 Sampling Procedure

The medium sample should be representative of the crop or problem you wish to analyze.

1. For routine analysis, samples should be collected from 5 to 10 pots and combined into a single sample. The sample should be collected from either: a) the top to the bottom of the pot, excluding the top 1/2 inch of the medium or b) the center 1/3rd of the pot (pinch a handful of medium).
2. Thoroughly mix the subsamples together to make a single homogeneous sample.
3. Sample problem pots or benches individually.
4. Place the samples in a plastic bag, which is labeled with your name, address, the crop, and location of sample.

• Follow the same procedure every time you sample so you can compare results and detect trends over time.
• One to 2 pints of medium are required for conducting analysis, but smaller volumes can be submitted; however, the results may not be as accurate.
• New medium should be wetted to container capacity by placing the sample in a growing container, watering it until drainage occurs, and after drainage stops the sample can be bagged and mailed. With mail delivery time, this allows 2 days for the lime to react and correct pH readings can be obtained.

Alkalinity can be a major factor affecting pH changes in the root medium. The higher the alkalinity level, the quicker there will be an increase in pH of soilless root medium. Water tests are recommended for each well that you have and should be done one to four times a year. A standard analysis usually includes pH, EC, and alkalinity.

 Growers may also want to test for macro- and micronutrients (N, P, K, Ca, Mg, S, B, Cl, Cu, Fe, Mn, Mo, and Zn) in their water. Testing for macro- and micronutrients should be done for each well at least once a year. Growers with excessive alkalinity levels will need to neutralize it by acid addition. Check to see if your lab provides an acid addition rate.

Sampling Procedure

1. Allow the water to run for 5 minutes to clear the line.
2. Rinse a clean plastic 16 oz. container 2 to 3 times with the water to be tested.
3. Fill the container completely and cap tightly.
4. Label bottle with your name, address, and type of analysis requested.
5. Mail the sample within 24 hours.

Fertilizer water tests are recommended for checking the accuracy of their injector or to check their mixing procedures. Testing by commercial labs should be done 2 to 4 times a year. In addition, growers should conduct weekly in-house EC testing of their injectors accuracy. A standard analysis usually includes: pH, EC, NO3-N, NH4-N, P, K, Ca, and Mg. Before submitting a sample, growers should accurately weigh out their fertilizer and thoroughly mix it to have a representative sample.

Sampling Procedure

1. Allow the fertilizer water to run for 5 minutes to obtain a representative sample.
2. Rinse a clean plastic 16 oz. container 2 to 3 times with the water to be tested.
3. Fill the container completely and cap tightly.
4. Label bottle with your name, address, and type of analysis requested.
5. Mail the sample within 24 hours.

Plant tissue analysis can be conducted to determine the nutrient status of the crop or for problem solving. Plant tissue analysis is especially useful when one needs to determine micronutrient levels in the plant. A standard analysis usually includes: macroelements (N, P, K, Ca, and Mg) and micronutrients (B, Cu, Fe, Mn, Mo, and Zn).

Sampling Procedure

1. The leaf tissue samples should be representative of the crop or problem you wish to analyze.
2. For routine analysis, collect leaves from 20 to 30 plants (more leaves are required for plants with small leaves) and combine into a single sample.
3. Sample problem plants or benches individually.
4. If foliar nutrient sprays have been used, gently wash the leaves in distilled water for 10 to 20 seconds to remove surface contaminants.
5. Send samples in a paper bag, which is labeled with your name, address, the crop, and location of sample.
6. Mail the sample within 24 hours. Try to collect the sample at the beginning of the week so delivery will not be delayed over the weekend.

• Plant analysis standards for many of the minor floriculture crops have not been established. Submit a problematic and a non-problematic sample for a comparison.
• Generally, the most recently matured, fully expanded leaves are collected from the upper part of the plant.
• Follow the same procedure every time you sample so you can compare results and detect trends over time.

Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.