The Pro Farmer

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The Role of Nitrogen in Plant Growth and Development

In order to grow properly and produce improved and quality fruits, our plants need nutrients in the right proportions and at the right time.

During the life cycle of the plant – growth and flowering, it needs different nutrients.

During the growth period the plant will need larger doses of nitrogen than in the flowering period,

The flowering period is when the plant will need larger doses of nutrients like phosphorus and potassium.

Plants show signs when they are not getting the nutritious minerals and also when they are getting too much of them.

In addition, a situation can arise where these elements are not available for absorption.

The availability of nutrients depends not only on the amount of fertilizer we add to the irrigation water but also on environmental factors such as the level of water acidity and the temperature of the growing area.

Fertilizer contains one or more of the essential nutrients needed by a plant:

Macro elements:
A. Nitrogen (N ׂ)
B. Phosphorus (P)
c. Potassium (K)

Also included in this group are: calcium (Ca), magnesium (Mg) and sulfur (S), which are required for fertilization in inert growing media and in unique soil and water conditions.

There are types of fertilizer solutions that also contain elements needed for the plant in minimal amounts and are called micro-elements:

Iron (Fe), Zinc (Zn), Manganese (Mn), Molybdenum (Mo), Copper (Cu), Boron (B) and more.

Nitrogen (N)

Nitrogen is a major component of the plant.

In many cases other nutrients are found at reasonable levels in the soil, and often are not generally given in fertilizer.

Lack of nitrogen fertilization (including compost) in most cases will be crucial to the success of the orchard yield in a commercial crop.

Lack of nitrogen will cause growth retardation, lack of flowering and embalming, little amount of fruit and small size fruits.

Excess nitrogen will cause accelerated vegetative growth, susceptibility to diseases and pests, and low fruit quality
and shelf life.

Plants need a lot of nitrogen in their growth stage, but excess nitrogen can be easily reached.

In this case, wash the growing medium with clean water.

Nitrogen deficiency:

Slow growth rate and yellowing leaves will most often be signs of nitrogen deficiency.

Nitrogen is a mobile element and signs of deficiency from it will begin to appear in the lower part of the plant in mature leaves, and in the absence of treatment the deficiency will spread and also appear in higher parts of the plant.

If we detect a nitrogen deficiency at the end of the flowering period, the situation is completely normal since the plant depletes its nitrogen stores during the flowering process.

But, if the plant loses a lot of yellowing leaves or the loss of the leaves begins to climb up the plant especially during the growth period, before the plant begins to flower then there is probably a lack that the grower needs to take care of to prevent damage.

Nitrogen Excess:

Increased vegetative growth, a tall plant with too thin stem.

The leaf will be stronger, dark green and fleshier than usual.

A Nitrate (NO3-) concentration of over 300ppm (of runoff solution or the soil water sampler solution) is too high and will require rinsing the growing medium with clean water.

The first of three numbers on the fertilizer package is Nitrogen (N), the second is Phosphoros (P) and the third is Potassium (K).

The number represents the weight percentage of the nutrient in the fertilizer package.

For example: if you buy a 25lbs pack of 32-3-8 fertilizer, it means that: 32% of that, is pure nitrogen (N) -8lbs. 3% is pure phosphorus (P)- 0.75lbs. 8% is pure potassium(K)- 2lbs.

This kind of fertilizer is good for lawn grasses, and golf course grasses that need plenty of nitrogen and almost no Phosphoros or potassium, since grass must continually renew itself.

Nitrogen (N) comes as a fertilizer in the form of:

Nitrate (NO3-), is available immediately to the plant.

Ammonium (NH4+) available immediately to the plant, changes to Nitrite (NO2-), which changes to Nitrate (NO3-) after a few days.

Urea (NH2) is not available immediately to the plant, but changes to Nitrate (NO3-) after a while.

For example: in the famous 20-20-20 Soluble Fertilizer, the total Nitrogen (N)-20.00% ……. nitrate nitrogen-5.98% ……. ammoniacal nitrogen-6.00% ……. urea nitrogen-8.02%, available Phosphate (P2O5)-20.00%, Soluble Potash (K2O)-20.00%.

Nitrite (NO2-) does not change to Nitrate (NO3-) without Oxygen.

Nitrite (NO2-) is also very toxic to the plant’s roots.

Over irrigation causes lack of Oxygen in the soil.

Appearance and accumulation of Nitrite (NO2-) points to over irrigation/watering, so it’s necessary to reduce the irrigation dose.

Nitrite (NO2-) shouldn’t be present at all.

Even the slight of presence in the stick test means that there is a situation of over irrigation, Flooding and lack of oxygen at the roots.

Test kit for Nitrite (NO2-) and Nitrate (NO3-)

In order to know if there is a lack or excess of nitrogen, you need to check the nitrate concentration in the irrigation water and in the solution that was obtained from the soil water sampler, or the runoff water.

The concentration of the nitrate in the solution should always be higher than the one from the irrigation.

For example:

If the irrigation water has a concentration of 100ppm, the obtained solution should have 120ppm, it indicates that there was still nitrate in the soil before the current irrigation.

Fertigation (irrigation + fertilizer)
N concentration
Solution (from soil water sampler/runoff)
N concentration
SituationMeasures to be taken
100ppm100ppm or lessThe plant is in nitrogen deficiencyRaise the quantity of nitrogen in the fertigation. Add more fertilizer.
100ppm120ppm-190ppmThe plant has enough nitrogen at the moment.Check again in a few days
100ppm200ppm and abovenitrogen excessLower the amount of nitrogen in the fertigation.
A waste of fertilizer. Add less fertilizer
Nitrite (NO2-)Over irrigationLower the water dose

If you use granular fertilizer, or compost before planting, or if you do not fertigate and use only irrigation pure water, you should only check the soil water sampler/runoff solution for nitrogen surplus.

As long as there is, you’re fine, if not add some granular fertilizer.

Lawn fertilizer
Fertilizer for Edible Gardens
High nitrogen liquid fertilizer
balanced NPK liquid fertilizer

For more info about minerals for your soil, click these links:

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