Nut trees cut soybean farms’ modeled footprint, but yields fell

In the western Slovakia models, sweet chestnut delivered the largest climate reduction, while hazelnut systems kept more soybean production.

Editorial illustration — not from the study.

A life cycle assessment of farms in western Slovakia found that adding European hazelnut or sweet chestnut trees to soybean systems reduced their modeled net greenhouse gas emissions compared with soybean monoculture. The largest reductions came from chestnut systems, where carbon uptake in modeled woody biomass outweighed other emissions.

The modeled soybean yields were lower in the tree-based systems, falling by 61–83% compared with conventional soybean monoculture. Hazelnut systems retained more soybean production than chestnut systems, while chestnut systems produced the larger modeled reduction in climate impact. Nut harvests provided an additional farm output.

Soybean yields and tree carbon

The researchers compared conventional soybean monoculture with soybean systems that also included European hazelnut or sweet chestnut trees. All of the soybean–nut systems had lower modeled net greenhouse gas emissions than conventional soybean monoculture.

Total modeled climate impact ranged from −8.8 to −17,122 kilograms of carbon dioxide equivalent per hectare. Compared with conventional soybean monoculture, the modeled climate impact fell by 68–101% in hazelnut systems and by 1,020–1,265% in chestnut systems. The values below zero resulted from counting carbon uptake in tree biomass as a negative flow.

Modeled soybean yields ranged from 416 to 979 kilograms per hectare, with declines of 61–83% compared with conventional soybean monoculture. Sweet chestnut systems produced the largest modeled reductions because of woody-biomass accumulation. Soybean–hazelnut systems had higher modeled soybean yields but smaller climate-impact reductions. The nut trees also provided an additional agricultural product.

The production trade-off

The results indicate that integrating nut trees with soybeans could combine food production with modeled climate mitigation, but the trade-off was substantial: soybean production fell sharply in the assessed configurations. The comparison also shows that the choice of tree matters. Sweet chestnut offered the largest modeled reduction in climate impact, while hazelnut preserved more soybean yield.

Evidence and caveats

The study used a cradle-to-farm-gate life cycle assessment to model climate impacts in soybean monoculture, nut-tree systems and three soybean–nut agroforestry configurations in western Slovakia. It assessed only climate change impact, not other environmental measures. The results depend on the study’s assumptions, including modeled carbon uptake in tree biomass, and do not establish how these systems would perform in other regions or under different management conditions.

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