Swiss Field Data Show Comparable Wheat Yields With and Without Herbicide Use

How can plant-protection product use in winter wheat be reduced without compromising yields? An Agroscope study shows that a combination of herbicide-free weed-control measures can achieve yields comparable to those obtained with herbicide use.

Reducing the use of plant-protection products (PPPs) is an important objective of Swiss agricultural policy. A key question in arable farming is whether weeds can be effectively controlled without the use of herbicides. As part of the PestiRed project, Agroscope researchers worked together with advisory services and farmers to evaluate the performance of integrated weed management (IWM) strategies in winter wheat under real farming conditions. The focus was on determining whether herbicide-free approaches enable comparable yields and identifying which measures are most effective.

A combination of different measures is effective

From 2020 to 2023, 94 winter wheat fields across Switzerland were monitored. Integrated cropping systems with and without herbicide use were compared. Farmers implemented different measures, including adapted tillage practices, delayed sowing, false seedbeds and mechanical weed management. Weed biomass and grain yield were subsequently assessed, and the key factors influencing these outcomes were identified.

Low weed pressure with and without herbicides

The main finding was that wheat yields did not differ between systems with and without herbicide use. At the same time, weed pressure remained low in most fields. Only a few sites reached weed biomass levels associated with yield losses. Rather than a single measure, it was the combination of different preventive and targeted direct weed management measures that proved decisive. Under the practical conditions studied, herbicide-free systems achieved yields comparable to those of systems using targeted herbicide applications.

Key factors influencing weed biomass and yield

Of particular importance were a well-chosen sowing date, adapted seeding rates and false-seedbed preparation. More intensive tillage also reduced weed biomass. Wheat yield was additionally influenced by rainfall conditions, soil type and site-specific yield potential. In the fields studied, herbicides were only one component of successful weed management. The results highlight the importance of a long-term cropping strategy that combines different measures in a targeted and complementary way.

Mechanical control with potential trade-offs

However, the study also highlights the limitations of herbicide-free systems. While more- intensive tillage reduced weed biomass, increased mechanical weed control was associated with yield losses. Herbicide-free approaches were only able to maintain yield levels when weed management was effective. Under certain conditions, higher labour and operational costs can be offset by price premiums and direct payments.  Since the results are largely based on sites with moderate weed pressure, their transferability to more challenging conditions is limited.