Soft fruit agronomy: preparing irrigation and coir systems for the new season

As planting plans take shape, winter is the right time to prepare irrigation systems, fertigation lines and growing media. A clean, efficient system helps ensure uniform establishment and reduces risk later in the season.

At this time of year attention turns to planting preparations. Winter jobs often include checking irrigation and fertigation systems so everything is ready when crops go in.

After last season’s warm weather, the old phrase “start clean, stay clean” feels particularly relevant. Irrigation systems were under far greater pressure than usual, with higher volumes of water and nutrients passing through them.

That makes winter system cleaning an important first step before the new season begins.

Cleaning irrigation systems before planting

Irrigation lines should be flushed over winter using hydrogen peroxide, or a hydrogen peroxide and silver combination, to sterilise the system and remove any biofilm build-up.

Biofilm inside irrigation lines can restrict flow and affect nutrient delivery. Removing it helps restore system performance and ensures water moves freely through the network.

If a full flush is not carried out during winter, running a continuous low-dose hydrogen peroxide treatment through the system during the season can help reduce and prevent biofilm build-up.

A clean irrigation system also helps maintain uniform crop establishment. Every plant should receive the same volume of water and nutrients. If drippers become blocked or restricted, some plants receive too much water while others receive very little.

Water management is becoming increasingly important

The 2025 season was another reminder that water is becoming a more valuable resource for fruit growers. Changing weather patterns and longer dry periods are making reliable water supply increasingly important.

Many growers are already reviewing long-term plans around water storage and irrigation capacity. Investment in reservoirs and storage systems is likely to become more common as pressure on water resources increases.

Preparing for changes in phytophthora control

Another reason to begin the season with a clean irrigation system is the reduced availability of Paraat (dimethomorph).

Some growers experienced shortages of the product during 2025, and 2026 will be the final year it remains available. That means attention will increasingly turn to alternative strategies for managing phytophthora risk.

Good irrigation hygiene and system maintenance will play an important role as growers adapt to these changes.

Managing coir substrates and salt levels

Clean irrigation systems are also important for growers using washed coir substrates in bags or slabs. Proper flushing is required to remove excess salts from the growing medium.

During this process drippers must deliver consistent volumes of water to ensure salts are removed evenly across the crop.

When flushing coir with calcium nitrate, growers should check that the substrate has hydrated fully and that there are no dry spots remaining in the bags or slabs.

Where possible, testing the pH and EC of coir provides useful insight into salt levels and nutrient balance. If testing equipment is not available on farm, samples can be sent to a laboratory for analysis of pH, EC and nutrient content.

Confirming coir specification with suppliers

It is also worth confirming with your supplier exactly which type of coir has been delivered. During the 2025 season some suppliers were unable to provide fully buffered coir for all orders, and some growers received a mixture of washed and buffered products.

Knowing which substrate is being used is important because it affects management decisions during crop establishment and early fertigation.

Understanding sodium risks in coir systems

One issue that occasionally appears in coir systems is elevated sodium levels. Sodium is not taken up by plants and can accumulate within irrigation water and growing media.

As salinity rises it can affect plant health and root performance.

An additional source of sodium can come from potassium nitrate fertilisers, where sodium levels may vary between manufacturers. In some cases concentrations can range from 1,500 ppm to 6,000 ppm.

A newer potassium nitrate fertiliser, Multi-K Reci, contains almost no sodium. Using products with lower sodium levels reduces the need for repeated flushing and helps maintain a more stable growing environment.

Fewer flushing events also mean improved water efficiency and reduced labour requirements.

Final planting checks before the season begins

Alongside irrigation preparation, growers should also carry out the usual planting checks.

• Confirm plant availability and delivery schedules with suppliers.
• Inspect plants on arrival to assess root health and overall condition.
• Check irrigation systems are delivering even flow across the crop.
• Monitor young plants closely during early establishment.

Attention to these fundamentals early in the season helps reduce problems later and supports uniform crop development across the planting.

About the author

Jason Steels is a horticultural agronomist with Agrii, advising soft fruit growers across the Midlands from Norfolk to Herefordshire.