A lawn needs about a dozen nutrients to function properly. Some it uses in large amounts, others in tiny amounts. A good fertiliser programme covers all of them.
The primary nutrients (N-P-K)
These are the three you see on every fertiliser bag. The numbers represent the percentage of each by weight.
Nitrogen (N)
The growth driver. Nitrogen is a key building block of chlorophyll, the green pigment that powers photosynthesis, and it pushes leaf and tiller production. Most of the difference between a tired pale lawn and a thick green one comes down to nitrogen.
Too little and the lawn yellows, thins, and weeds move in. Too much and you get soft fast growth that’s a magnet for disease and falls over in heat or drought. The trick is steady controlled nitrogen, not big spikes followed by crashes. That’s why slow-release granular technology matters, it spreads the feed across weeks rather than dumping it in one hit.
Nitrogen is usually the highest number on the bag because it’s the nutrient the lawn uses most.
Phosphorus (P)
The root nutrient. Phosphorus drives root development and energy transfer inside the plant. It’s particularly relevant at lawn establishment, which is why NZLA Starter runs higher in phosphorus than the maintenance fertilisers.
Most established NZ lawns sit on soil with adequate phosphorus already. The Olsen P test on a soil sample tells you where you’re at. Maintenance feeds like NZLA All Seasons carry small amounts to top up what the lawn uses, no more.
Phosphorus doesn’t move much in soil, so it’s worked into the root zone at establishment rather than top-dressed later. Deficiency shows as stunted growth and sometimes a purple tinge on the leaves.
Potassium (K)
The stress nutrient. Potassium regulates water movement inside the plant and strengthens cell walls. A lawn with adequate potassium handles drought, heat, cold, traffic, and disease pressure much better than one that’s run down.
Potassium also lets the plant use nitrogen more efficiently. Skimp on K and the nitrogen response is weaker even if the lawn looks fed.
NZLA All Seasons and Lawns SR are both 16% potassium, which keeps the lawn’s stress tolerance up year-round.
The secondary nutrients (Ca, Mg, S)
Used in smaller amounts than N-P-K but still in macronutrient territory. Often supplied through other applications (lime, gypsum, soil amendments) rather than dedicated fertiliser.
Calcium (Ca)
Calcium goes into cell wall structure and root tip development. It also influences soil structure on heavy clay. Most NZ soils have adequate calcium, but it shifts down over time on acidic soils.
Lime applications (calcium carbonate) supply calcium and raise soil pH. Gypsum (calcium sulphate) supplies calcium without affecting pH.
Magnesium (Mg)
Magnesium sits at the centre of every chlorophyll molecule. Without it, no chlorophyll, no green colour. Some sandy NZ soils run low on magnesium.
Sulphur (S)
Sulphur is part of several proteins and enzymes the plant builds. NZ pasture-derived soils sometimes run low. The slow-release nitrogen technology in NZLA’s granular range (PCSCU, polymer and sulphur-coated urea) supplies sulphur as part of the nitrogen delivery, so the maintenance programme covers it.
The micronutrients (trace elements)
Used in tiny amounts but the lawn still needs them. Most NZ soils supply most of them naturally. The exceptions are worth knowing.
Iron (Fe)
The most relevant micronutrient for lawn appearance. Iron drives chlorophyll production alongside nitrogen, and a lawn with adequate nitrogen but low iron still looks pale.
NZLA Iron+ is chelated iron in foliar form. Chelated means it stays plant-available even on alkaline soils where free iron locks up. Colour response shows in 1 to 3 days. NZLA All Seasons has 5% iron in the granular, Lawns SR has 6%. Standard programmes usually cover iron requirements without needing extra, though Iron+ is the go-to for colour push between granular applications.
Manganese (Mn)
Manganese helps with chlorophyll production and several enzyme systems. Less commonly deficient than iron, but a real issue on high-pH soils where availability drops, particularly some areas of Canterbury, Bay of Plenty and Hawke’s Bay where the soil sits naturally on the alkaline side.
The symptoms look similar to iron deficiency, pale interveinal chlorosis on the leaves, but the pattern shows up more uniformly across young and old leaves rather than just the new growth. A lawn that responds only partially to iron applications is worth investigating for manganese.
NZLA Iron+ doesn’t supply manganese specifically. For confirmed manganese deficiency, manganese sulphate as a foliar spray is the treatment. The long-term fix is bringing soil pH down toward 6.0 to 6.5 with sulphur applications.
For most NZ home lawns on slightly acidic soil, manganese isn’t an issue. This one matters for the small percentage of lawns where the soil is genuinely alkaline.
Zinc (Zn)
Zinc regulates several enzyme systems and contributes to chlorophyll. Rare on lawn soils. Most NZ soils have adequate zinc.
Copper, boron, molybdenum, chlorine, nickel
Used in even smaller amounts. Deficiency on home lawns is uncommon. Quality granular fertilisers carry trace amounts as part of the formulation. Soil testing through a commercial lab Hill Laboratories can confirm trace levels if you’re chasing an unexplained problem.
What this means for fertiliser choice
A quality fertiliser supplies the primary nutrients in the right ratio for lawn growth, has adequate potassium for stress tolerance, includes iron and trace elements, and releases over a useful window rather than dumping everything in a week.
Different slow-release technologies are used across the fertiliser products on the NZ market. NZLA sources premium polymer and sulphur-coated urea (PCSCU) for the controlled-release backbone of All Seasons, Lawns SR, and the rest of the granular range.
Some brands use lower-cost PCSCU or alternative slow-release coatings to bring price points down. The release curves on the cheaper options are less predictable and the coating quality varies. That’s the call NZLA’s made on the input side, premium coating tech over input cost. It’s what separates a fertiliser that performs to expectation across a season from one that releases too fast or too slow.
For a typical home lawn programme, NZLA Lawns SR or All Seasons three times a year covers the primary and secondary nutrients plus iron. Foliar NZLA Iron+ adds an extra colour push between granular applications when the lawn wants it.
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