Available N
Available nitrogen on the sheet is this season’s supply, not a prescription.
Also called: alkaline-hydrolysable N, available N, hydrolysable nitrogen
- This cell is this season’s nitrogen, not total N.
- Read it next to total N.
- Old leaves yellow, new leaves greener — that is the N look.
- New leaves yellow with green veins is not nitrogen.
- Rates live in the nitrogen guide.
How it appears on the sheet
Alkaline-hydrolysable or available nitrogen. This season’s N, not total N. Often mg/kg.
A sketch. Do not fertilise from the picture alone.Common units
Often mg/kg. This season’s N, not the whole warehouse.
Soil:water ratio · Total N is the warehouse. This cell is this season’s meal. Read them together.
How to read the number
Too low: yellow old leaves. Too high: lush lodging. Use the provincial class. This table is a sketch.
Don’t chase urea at the first yellow. Split leaf position and the root. Rates live in the nitrogen guide.
Thresholds only, not a prescription. Rates live in the field guide. This page does not hand you a bag count.
| Cell | Low | Mid | High |
|---|---|---|---|
| Available N mg/kg (sketch) | This season’s meal is short | Enough for many grain fields | More N often lodges |
Regional classes differ. This table is a comparison, not a prescription.
What it looks like in the field
Old leaves evenly yellow, new leaves still greener, roots still white — that is the nitrogen look. New leaves yellow with green veins is not this cell.
Don’t do this
- Don’t mix total N with this cell.
- Don’t call iron-lock a nitrogen gap.
- Don’t pour urea on black smelly roots.