Potted Deciduous Fruit Tree Fertiliser Trials

From 2019 to 2021 PlantNet® conducted fertiliser trials on blueberries and deciduous fruit trees. The aim of these trials were to help the home gardener get the best out of their PlantNet® products using products readily available to the home gardener. This page contains a summary of the deciduous fruit tree trials, with recommendations on the best fertiliser plan.

Scroll to the bottom of the page for our summary!

Our fertiliser plans from these trials can be used for Apples, Pears and Stonefruit varieties.

Artificial and organic product trials have shown the following results and we have found there are fertilising plans which showed better results than others.

Fertiliser plan 1 produced the largest fruit and the best plant growth when applied to stonefruit.

Fertiliser plan 1 or 2 produced the largest fruit and the best plant growth when applied to apples.

Fruit trees in pots should be fertilised every 2 weeks for best results except months marked with – .

PLEASE NOTE: PlantNet cannot recommend specific brands of fertiliser as there can be privacy and confidentiality issues if we do this. Please follow the directions below.

When purchasing fertilisers look for the nutrient analysis on the container to match as closely as possible to the product NPK used in our fertilising plans. below. There are products available on the market with the same or similar analysis to what we have used.

Examples of products on the market and how they list nutrient analysis below.

The soluble liquid fertiliser we tested in Trial 2.

The controlled release fertiliser we tested in Trial 1 and 2.

Three different fertiliser programs were used. Apply once a fortnight for best results but every 3 weeks is fine.

Fertiliser plan 1– This has shown the best plant growth and cropping results in stonefruit and good results in apples. Use all products in the plan and apply separately and water in. Do not apply fertiliser for three weeks after planting.

Products used:

Product 1 – Controlled release fertiliser with analysis of (N)Nitrogen 15.3%, (P) Phosphorous 2%, (K) Potassium 12.6% Has some trace elements

Product 2 – Urea (N) Nitrogen 46%

Product 3 – Sulphate of Potash (K) Potassium 41%

Product 4 – Liquid trace element mix.

Fertiliser plan 2– In stonefruit this produced 25% less fruit than Plan 1. In apples this produced the same amount of fruit as Plan 1. Use all products in the plan and apply separately and water in. Do not apply fertiliser for three weeks after planting.

Products used:

Product 1 – Soluble fertiliser blend- (N)Nitrogen 14%, (P) Phosphorous 2.6%, (P) Potassium 21%

Product 2 – Gradual release fertiliser blend- (N)Nitrogen 13%, (P) Phosphorous 1.0%, (P) Potassium 11%- Has some trace elements

Product 3 – Liquid Potassium- (K) Potassium 14%

Product 4 – Liquid trace element mix

Fertiliser plan 3 (Organic) produced 70% less fruit in stonefruit and apples than plan 1 and 55% less than plan 2. Use all products in the plan and apply separately and water in. Do not apply fertiliser for three weeks after planting.

Products used:

Product 1 – Organic Controlled release fertiliser with analysis of (N)Nitrogen 15.3%, (P) Phosphorous 2%, (K) Potassium 12.6%- Has some trace elements

Product 2 – Natural Potash- (K) Potassium 41%

Product 3 – Seaweed, fish, kelp, humic acid, and manure have been digested by the beneficial bacteria.

Fertiliser Plan 1

The aim of this plan was to test a holistic fertilising regime on deciduous fruit trees. This plan proved to be the best plan for stonefruit.

Please note: Premium potting mix contains controlled release fertiliser – do not add more controlled release fertiliser if using this mix until the second application OR until the fertiliser in the potting mix expires, as listed on the bag.

A Dwarf Fresno Peach in Fertiliser Plan 1 – 2021

Fertiliser Plan 2

This plan produced 25% less fruit in stone fruit than Plan 1, however apples produced the same amount of fruit in both Plan 1 and Plan 2. The aim of this plan is to replace the use of urea with soluble liquid fertiliser.

Please note: Premium potting mix contains controlled release fertiliser – so do not add more controlled release fertiliser at planting if using this mix until the second application OR until the fertiliser in the potting mix expires, as listed on the bag.

A Leprechaun Apple in Fertiliser Plan 2 – 2021

Fertiliser Plan 3

This plan produced 70% less fruit in stone fruit and 55% less fruit in apples than Fertiliser Plan 1. The aim of this plan was to test the effectiveness of organic products on deciduous fruit trees.

Please note: Premium potting mix contains synthetic controlled release fertiliser – if you use this mix with Fertiliser Plan 3 you will see different results than us.

A Leprechaun apple in Fertiliser Plan 3 – 2021

Summary

For the best results in your stone fruit we recommend following Fertiliser Trial 1. For apples the best plans are 1 and 2. The benefits of this trial aren’t only fruit production – the fruit trees in trial 1 (stone fruit and apples) and trial 2 (apples only) were healthier and more resistant to pest and disease attacks.

To follow this trial you need to stock up on:

A good controlled release fertiliser, like the one in the orange tub at the top of the page. The fertiliser you use doesn’t have to be exactly this fertiliser – what’s most important is the NPK ratio is similar.
A bag of urea (Nitrogen 46) (OR soluble liquid fertiliser with the specifications at the top of the page – apples only)
A bag of sulfate of potash (Potassium 41)
Trace element mix (you can purchase concentrate, ready to use, or as a soluble powder)

After year 3 – increase fertiliser rates by 50% if trees are presenting good growth