Four-Year Field Trial: Cover Crops Increase Yields and Improve Farm Economics

A four-year study conducted at METK's Kuusiku experimental centre confirmed that growing cover crops helps increase yields in conventional farming, and proper crop rotation improves agricultural producers' financial results. The study revealed a surprising finding: on less fertile soil, organic farming proved more profitable in terms of gross margin than conventional farming in most years.

The Rural Knowledge Centre (METK) Kuusiku experimental centre conducted a four-year comprehensive study of organic and conventional farming that highlighted the important role of cover crops and proper crop rotation in agriculture. The results confirmed that alternating crops in rotation cycles produces stronger plants and better yields.

Cover crops bring benefits especially to conventional farming

Within the framework of the study, two crop rotation schemes meeting the minimum requirements for organic farming and environmentally friendly management were tested on experimental plots: cereal-clover and cereal-cover crop rotations. As a control, a field with only cereal rotation, a scheme not meeting the requirements, was used.

METK agroecology specialist Karli Sepp explained that the effect of cover crops on cereal yields was most evident in conventional farming, where nutrients left unused in the soil by autumn enabled cover crops to build up greater biomass. "We have a particular problem in conventional farming in that a great many nutrients remain unused in the soil by autumn," said Sepp.

According to the trial results, the cereal-clover rotation scheme generally provided the highest gross margin. The winter rye yield following red clover was on average 21 per cent higher in organic farming than in the cereal monoculture rotation and 11 per cent higher than in the cereal-cover crop rotation.

A surprising paradox on less fertile soil

One of the most notable findings of the study concerned the competitiveness of organic farming. Sepp acknowledged that at the outset of the trial, it was assumed that conventional farming would outperform organic farming in the test in any case. "As the trial continued longer, it turned out that actually organic farming produces a higher gross margin in most years," he said.

The Kuusiku sandy loam, which dries out quickly, yields somewhat lower harvests than the more fertile soils elsewhere in Estonia. It was this very condition that created the paradox: organic farming yields were smaller than those from conventional farming, but the gross margin proved higher, partly thanks to organic farming subsidies, which have been considerably higher than those for conventional farming.

Science combines practice and environmental stewardship

Iiri Raa, head of METK's agroecology field, stressed that science plays a very important role in agricultural activity, combining the practical needs of agricultural producers with environmental protection. "We really need to study environmental protection, biodiversity and soil management specifically in the fields, because agriculture does not affect nature simply in general, but through very concrete mechanisms that require measurement, observation, monitoring and testing," she explained.

Raa also drew attention to the fact that environmental impacts often manifest very slowly. "Changes in soil fertility or species diversity may not be visible in a single agricultural season, they develop over years or even decades. And that is why long-term trials and monitoring are necessary," she said.