Controlled Release Fertilizers Enhance Soil Health

Controlled release fertilizers are primarily used to improve the efficiency of nutrient delivery, releasing nutrients over a defined period rather than making them immediately available after application.

Long-term research from Shandong Agricultural University in China has now looked beyond nutrient use efficiency to examine how different controlled release fertilizer technologies can influence the soil itself.

Published in the European Journal of Agronomy, the 12-year study compared several coated urea fertilizers and found changes in soil organic matter and microbial communities, particularly where sulfur-coated and polymer/sulfur-coated urea were used.

What did the research examine?

The study compared three controlled release fertilizer technologies:

• polymer-coated urea (PCU)
• sulfur-coated urea (SCU)
• polymer/sulfur dual-layer-coated urea (PSCU)

These treatments were assessed against conventional urea over 12 years, allowing the researchers to examine how repeated fertilizer use affected the soil over the longer term.

Particular attention was given to soil organic matter and the abundance of microorganisms associated with plant growth and soil function.

Changes in soil organic matter and microbial communities

The strongest effects were seen with sulfur-coated urea and polymer/sulfur-coated urea.

These treatments increased soil organic matter and changed the relative abundance of several plant growth-promoting microorganisms compared with conventional urea and polymer-coated urea.

The study also linked these changes with improved plant growth and lower disease levels within the agricultural system.

The findings are important because they show that the effects of controlled release fertilizers are not limited to the timing of nutrient supply. Fertilizer formulation can also influence the soil environment over time.

What does this mean for turf?

The research was carried out in an agricultural cropping system rather than managed turf, so the results cannot be transferred directly to turfgrass management.

However, the processes examined are also relevant to turf soils. Soil organic matter, microbial activity and nutrient availability all contribute to the functioning of the rootzone and the way turf responds to nutrition.

For turf managers, the study adds to the evidence that fertilizer choice can influence more than short-term turf response. The way nutrients are released, and the materials used to control that release, can affect what happens within the soil over a much longer period.

Controlled release fertilizers and nutrient use efficiency

Controlled release fertilizers are already widely used in turf management because they can improve the timing and efficiency of nutrient supply.

By releasing nutrients gradually, they can help match nutrient availability more closely with plant demand and reduce the risk of excessive growth or nutrient loss.

For ICL, that forms part of a broader approach to nutrient use efficiency rather than a standalone solution.

“Efficient fertilization is an important part of integrated turf management,” says Dr Andy Owen, International Technical Manager for Turf and Landscape at ICL.

Part of an integrated turf management program

Controlled release fertilizers are one part of a wider turf management strategy.

Depending on the site, conditions and management objectives, a nutritional program may combine controlled release fertilizers with liquid nutrition, biostimulants, wetting agents and other inputs.

The value of controlled release technology lies in using it where it provides the right nutrient-release pattern for the turf and growing conditions, rather than treating it as a solution for every situation.

Building the evidence around long-term soil effects

The Shandong Agricultural University study provides useful long-term evidence that some controlled release fertilizer technologies can influence soil organic matter and microbial communities as well as nutrient availability.

Further turf-specific research would be needed before drawing the same conclusions for managed turfgrass systems, but the study broadens the discussion around controlled release fertilizers beyond nutrient delivery alone.

For turf managers, it reinforces the value of looking at fertilizer performance over the longer term: not only at the immediate turf response, but at how nutrient-release technology interacts with the wider soil environment.