Foliar Fertiliser: Feeding Plants Through the Leaves with Leading New Zealand Soil Scientist Dr Gordon Rajendram
Foliar fertiliser means spraying water-soluble nutrients directly onto plant leaves. In effect, it’s like a quick “vitamin boost” through the foliage. Research has long shown that leaves can absorb nutrients via stomata (tiny pores), cuticle and leaf hairs. So foliar feeding bypasses the soil and gives plants nutrients within hours. According to soil scientist Dr Gordon Rajendram, foliar sprays “deliver nutrients exactly when and where they’re needed” during cooler weather (1).
Why It Works in Winter
Foliar feeding is especially handy in cold seasons. When soil temperatures drop, root uptake of nitrogen slows dramatically, so grass barely grows. But a foliar spray can still feed actively growing leaves. Dr Rajendram explains: “Applying foliar fertiliser in winter means you’re not relying on soil temperatures to activate the nitrogen… You’re feeding the plant directly — it’s faster, more efficient, and leads to better results with less input.” In other words, you get a quicker response even when the ground is cold. Trials in New Zealand found that foliar N improved pasture growth at low temperatures, helping farmers extend growth into winter (1,2).
Real Results from New Zealand Trials
Figure: A replicated pasture trial found that using 9 kg N/ha as a foliar urea spray produced essentially the same grass yield (1,426 kg DM/ha) as 37 kg N/ha of granular urea. This means the foliar method gave about 61 kg of dry matter per kg N versus 14 kg per kg N for soil urea – roughly 4× more efficient (2). The response was quick and lasted for 24 days.
Better Efficiency, Less Waste
The efficiency gains are dramatic. By targeting nutrients to the leaves, plants use more of the fertiliser and less is lost. A recent review notes that foliar sprays “deliver nutrients directly… thereby helping to reduce negative impacts” on soil and water (3). In trials on wheat, even very low rates of foliar phosphorus in winter corrected mid-season deficiencies and boosted P use efficiency (4). Overall, foliar feeding can increase nutrient-use efficiency and yield, especially for micronutrients or in special situations.
When and How to Use It
Of course, foliar feeding supplements, not replaces, normal soil fertilisation. Think of it as an extra tool. Bulk N, P, K still come from soil and applied fertilisers, while foliar applications give fast fixes of nitrogen, major and trace elements. For best results, spray when leaves are moist (e.g. morning dew or light rain) and avoid very hot, dry weather to prevent leaf burn.
The bottom line: foliar fertilisers are a practical way to get nutrients into the plant quickly, especially when soil uptake is slow. As Dr Rajendram reminds us, with the right timing farmers can grow more winter grass with less input. By combining foliar sprays with a solid soil fertility plan, farmers can boost efficiency, reduce losses, and keep pasture growing through the cooler months (1,2).
About Dr Gordon Rajendram
Dr Gordon Rajendram is a New Zealand-based soil scientist with over 40 years of experience in nutrient management and soil fertility. Formerly with AgResearch, he is widely respected for his work on improving nitrogen efficiency and sustainable farming practices.
References
- Rajendram, G. S. (2025). Grow more grass in the colder months. Gordon Rajendram the soil scientist.
- Rajendram, G. S., et. al. (2009). Nitrogen fertiliser response trials over 80 years in New Zealand. New Zealand Journal of Agricultural Research, 52(4), 511–528.
- Chalker-Scott, L. (2015). Foliar fertilisation in plants: A review. Journal of Plant Nutrition, 38(3), 376–390.
- Mosali, J., et al. (2020). Foliar phosphorus application improves wheat P-use efficiency. Field Crops Research, 250, 107792.
Contact Dr Gordon Rajendram
021 466 077 | rajendram@xtra.co.nz
www.gordonrajendramsoilscientist.co.nz
Contact MediaPA
027 458 7724
phillip@mediapa.co.nz