Nitrogen

What is nitrogen?

N is the chemical symbol for nitrogen. It identifies the element, not a particular compound. Atmospheric nitrogen gas, soil nitrate and organically bound nitrogen are therefore not interchangeable.

Humans and animals obtain nitrogen mainly through nitrogen-containing food components such as proteins. In plants, uptake and transformation of available compounds through roots and leaves are central. A shared chemical basis does not create a shared dose.

From stored nitrogen to available forms

Mineralisation releases organically bound nitrogen. Temperature, moisture and microbial activity influence the timing. A large organic nitrogen reserve therefore does not guarantee adequate availability when the crop needs it. [2]

What does the number measure?

kg N/ha expresses nitrogen mass per area. Percentage N in leaf dry matter is a concentration in sampled plant material. mg N/L in must refers to a litre of liquid. These values cannot be converted into one another without further information.

Product quantities also need interpretation: 10 kg of fertiliser is not 10 kg of nitrogen. Transparent planning starts with the declared N concentration and its basis, then considers availability, timing and actual crop uptake.

How much nitrogen does a plant need?

There is no defensible universal quantity for vines, vegetables, houseplants and every soil. In viticulture, GRUD guidance distinguishes observations, nutrient demand, soil conditions and fertilisation measures. Leaf values are interpreted for specific crops and sampling times. [7]

A fertilisation plan first records crop, area, growth stage, previous crop or previous season, and production objectives. Existing supply is then assessed: mineral soil nitrogen, expected release and organic or mineral sources already applied. Calculated demand is not automatically an additional application requirement.

Which measurement answers which question?

Our practical interpretation: different measurements should help explain one another. If they appear inconsistent, check sampling, timing and units before changing fertilisation. One sensor reading does not replace understanding the site.

What does the research show?

A transparent practical sequence

Nutrient losses belong in this decision: nitrate can move with water, and certain soil conditions permit gaseous losses. Planning therefore also considers water movement and uptake timing. [1]

Marketing and use of fertilisers have their own requirements. EFSA human dietary values are not fertilisation recommendations. The Swiss Federal Office for Agriculture provides the relevant Swiss regulatory framework. [8]

• Record the starting point: crop, area, soil, irrigation, growth and previous applications.
• Define the question: general growth supply, a confirmed deficiency or, in viticulture, must nitrogen?
• Match measurements to suitable professional reference values. Vine leaf and must findings are not interchangeable.
• Plan amount, form and timing together. Increasing the amount does not automatically compensate for a poorly chosen date.
• Record the response and potential adverse effects, then compare equivalent data in the next season.