Classification of nutrients

 

What is an essential nutrient?

Essential nutrients are those nutrients needed by a plant to grow normal and to complete its life cycle. Sixteen elements were classified as essential for all crops. The essential nutrients are divided in macro-elements and trace-elements (also called micro-elements).

What is the difference between macro and trace elements?

The macro-elements are needed in large quantities. Only traces of the trace-elements or micro-elements are needed.

Do you know?

The trace elements occur in extremely small amounts in plants.

In a plant are, for an example, about 1 million nitrogen atoms (nitrogen is a macro – element) for every molybdenum atom (molybdenum is a trace element).

One hectare of cutroses in substrate needs 2 – 5 kg nitrogen per day, but they need only 1 – 3 grams copper per day.

As a matter of interest: If you irrigate your garden with a hose pipe connected to a copper tab, enough copper (copper is a trace element) will be released from the tab to supply your garden with adequate amounts of copper.

What are the names and symbols of the different nutrients?

The names and symbols of the nutrients are listed in the following table.

Macro-elements are: C (Carbon) H (Hydrogen) O (Oxygen) N (Nitrogen) P (Phosphate) S (Sulphur) K (Potassium) Ca (Calcium) Mg (Magnesium)

The trace-elements are: Fe (Iron) Cu (Copper) Mn (Manganese) B (Boron) Mo (Molybdenum) Zn (Zinc)     Cl (Chlorine)

 

All of these nutrients (macro – and trace elements) are needed by plants and must be included in a fertiliser program.

 

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Macro-elements: symptoms of disorders

 

Nitrogen The leaves of  nitogen-deficient roses are small and dull. Phosphate The most common symptom of phosphate deficiency is reduction in leaf and flower size.

Potassium Symptoms of deficiency: Stems are thin. Plants are less resistant to frost. Flowers are usually pale and small. Low resistance to fungi diseases.

Calcium Roses with a calcium deficiency have a short fase life and is not resistant to diseases. Magnesium Magnesium is very mobile in the plant and deficiency shows as yellowing between the veins of the older leaves. Click here to see the visual symptom of magnesium deficiency in roses.

 

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Trace elements: symptoms of disorders

 

Iron Fe deficiency always shows as yellowing of the youngest leaves. Click here to see the visual symptom of iron deficiency in roses. Molybdenum The deficiency symptoms are similar to moisture stress symptoms, chemical burn or low humidity burn.

Manganese, copper and zinc Symptoms of deficiency and toxicity vary from yellowing of the leaves to brown or dead spots on the leaves. Oxygen Oxygen deficiency causes leaf drop and yellowing of the leaves.

Boron Symptoms of deficiency: Bend necks. The outer petals open too soon. Click here to see the visual symptom of Boron  deficiency in roses. Symptoms of toxicity: Brown edges of the older leaves. Click here to see the visual symptom of Boron toxicity in roses.

 

 

 

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Fertilisers

 

Granular fertilisers consist of different ratios N:P:K. The ratio between the nutrients and the concentration of the nutrients are reflected in the name of the fertiliser.

One example of the many products available is:

The fertiliser in this example contains 11 parts N, 1 part phosphate and 8 parts potassium. The concentration is 20%.

Some suppliers have also added calcium, magnesium and trace elements.

 

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Feeding of garden roses

 

Rose growers in greenhouses feed their roses up to 18 times per day. Each application contains all the macro and trace elements in small concentrations. These fertigation programmes are based on frequent analysis of the growth medium.

For garden roses such an accurate and scientific calculated feeding program is neither possible nor necessary.

Production of good quality garden roses will be possible if you remember the following tips:

• Roses prefer a pH value just below neutral.
• Phosphate is needed for good flower development. Phosphate is not soluble and the best is to fork it deep into the soil before planting.
• Roses need potassium for the production of thick stems and big flowers.
• Nitrogen is needed for vigorous growth and a healthy and glossy appearance of the leaves.
• Roses need calcium for a good vase life and to make the plants more resistant to diseases.
• Magnesium is needed for a glossy appearance of the leaves.
• Your rose bed needs compost to improve the physical characteristics of the soil and also to supply the roses with the trace elements. It is however important to use good quality compost.
• Never apply fertilizers on a dry soil and always irrigate immediately after the application of granular fertilizers.

Program

(The following advice is only a guideline (the irrigation water and the soil is not taken into consideration).

Before planting:

1. Broadcast per square meter on the soil surface:
   • 5 to 10 cm of good quality compost and
   • 45 gram 7:7:7(20) with calcium, magnesium and trace elements. 
   • Also broadcast 150 gram dolomitic lime per square meter if the soil is too acid.
2. Incorporate with forks up to a depth of 30 cm Water abundantly before planting.
   • Dolomitic lime contains calcium and magnesium and will help to increase the pH if the soil is too acid.

Note: The pH of a sandy soil is usually lower than the pH of a clay soil.

 

 

Repeat every 8 weeks throughout the flowering season:

1. Broadcast 30 gram 11 – 1 - 8 (20) with calcium, magnesium and trace lements per square meter.
2. Water abundantly after this application.

 

Every year after pruning:

1. Broadcast 150 gram good quality compost per square meter on the surface of the rose bed.
2. Also broadcast 75 gram dolomitic lime per square meter if the soil is too acid.   Do not incorporate with the topsoil.

 

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Fertilisation

 

Greenhouses

Fertilizers are applied with the use of  fertigation systems. This means that fertilizers are given in a soluble form via the irrigation system.

The advantages of this system are:

• Fertilizers can be given in the correct ratios and concentrations.
• Small concentrations of fertilizers can be applied frequently.
• The nutrient status can be kept near the optimum value permanently.
• The nutrient status can be adjusted according the growth phase and needs of the crop.
• Fertilizers move with the irrigation water into the growth medium and are therefore spread more evenly than in the case where granular fertilizers are broadcasted on the soil surface by hand.

With the A and B – tank system stock solutions of fertilizers are dissolved in two tanks called the A and B – tank. The size of each of these tanks is normally 1000 litre and the concentration of the stock solution in each tank is 10% (100kg of fertilizers in each tank). Fertilizers are injected from these tanks into the mainline of the irrigation system. The amount of fertilizers injected from the concentrated tanks is controlled with an automatic electric conductivity meter (EC – meter). This instrument measures the conductivity (EC) of the irrigation water in the units mS cm-1. The EC is a function of the total amount of salts in the water and regulation of the EC is therefore an accurate way to regulates the amount of fertilizers in the irrigation water.

The rose garden

The A and B tank system is however too complicated and expensive for the growth of roses in your garden. A less expensive alternative is to make a ready to use mix of fertilisers in a big tank (between 1000 and 5000 liters) and to irrigate your roses once a week directly from this tank. The following mix may be used as long as the quality of your irrigation water is good.

Add the following fertilizers once a week per 1000 liters of irrigation water:

• Sandy soils: 400 gram calsiumnitrate + 250 gram potassiumnitrate + 25 gram mono ammonium phospate + 100 gram magnesiumsulphate.
• Clay soils: 350 gram calsiumnitrate + 200 gram potassiumnitrate + 25 gram mono ammonium phospate + 100 gram magnesiumsulphate.

Warning: If the above mix is not properly diluted unwanted chemical reactions will take place (Example: the calcium in the calcium nitrate will react with the sulphate in the magnesiumsulphate and insoluble gypsum will be formed). For the prevention of unwanted reactions use the following procedures:

1. Fill the tank to the 1000 liter mark.
2. Add the CaNO₃ and stir.
3. Add the KNO₃ and stir.
4. Add the MgSO₄ and stir.

5. Add the MAP and stir.

Warning:

• Do not use a stronger concentration unless otherwise advised by a soil scientist.
• Give once a month a foliar spray with a foliar feed containing all the trace elements.
• Remember: The fertigation replace the broadcasting of nitrogen, potassium, phosphate and magnesium.

 

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Soil analysis

 

The application of too much fertilizers will harm your roses and the application of too less will not give the results you want. The programmes given in this section do not take into consideration any soil analysis and the quality of your irrigation water is also not taken into consideration. Our advice is to do a soil analysis once a year and to adjust the program according the analysis. Send the result of the analysis to Florcom for an accurate adjustment of your program.

How to take a sample for analysis

Soil: Take 10 sub samples from a depth of 0 – 30 cm randomised from your rose garden. Mix and send 500g to the laboratory. Do not dry out and do not leave in the sun. Use clean bags and/or containers.

Irrigation water: Send 500ml to the laboratory. Use a plastic bottle. Use clean bottles. Fill the container to the maximum (no air between the lid and the water). Do not put the sample in the sun. Store in dark.

 

Ask the laboratory to measure the pH, EC and the concentrations of Ca, Mg, K, NO₃ and PO₄.

 

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