# Three-Year Cereal: Field Bean Intercropping Greatly Reduced Weed Abundance with Small Changes in Functional Composition

## TL;DR

Growing field beans and cereals together significantly reduced weeds compared to growing them alone, with only minor changes in weed diversity.

## Contribution

The study shows that intercropping cereals and field beans is an effective, sustainable alternative to chemical weed control.

## Key findings

- Intercropping reduced weed biomass two- to sevenfold compared to high-density sole crops.
- Intercropping slightly reduced weed species richness and favored tall weeds.
- Fertilization reduced species richness and favored widespread weed species.

## Abstract

In sustainable crop production, weed management presents special challenges. On the one hand, uncontrolled weed growth can hinder the achievement of quantitative and qualitative standards that meet market and societal demands. On the other hand, the positive contribution of weeds to the conservation of species richness and diversity within agroecosystems is a growing public concern. To address this issue, the influence of cropping system and mineral fertilization on the biomass and functional composition of weed communities was investigated in a three-year experiment in which field bean and winter cereals, either triticale or barley, were grown as intercrops and sole crops, with and without nitrogen and phosphorus fertilization. The simultaneous growth of field beans and cereals in the same field proved to reduce weed growth more effectively than sole crops, irrespective of mineral fertilization. Intercropping did not markedly change the functional composition of weed communities but slightly reduced weed richness and favored tall weeds. Fertilization also tended to reduce species richness and favored widespread weeds at the expense of narrowly distributed species. Intercropping could therefore represent an effective alternative to chemical weed control, although its potential long-term adverse effects on weed biodiversity should be monitored.

Weeds reduce crop yield but may also support agroecosystem biodiversity. The biomass and functional composition of weed communities were evaluated in cereal–field bean intercrops and sole crops, with and without NP fertilization. Intercrops were repeatedly grown in the same plots using 1:1 and 2:1 cereal:field bean row ratios, while sole crops were sown at low or high density and rotated. Weeds were sampled at cereal flowering and maturity stages. Fertilization had little effect on weed biomass but tended to reduce species richness and favor cosmopolitan species. Intercropping reduced weed biomass two- to sevenfold compared with high-density cereal and legume sole crops. Plot richness was 39% lower in intercrops than in field bean and low-density cereal crops. Over three years, weed functional composition was influenced more by year than by crop system or fertilization. However, the contribution of tall weeds increased in intercrops: 51% compared to 42% in high-density sole crops and approximately 31% in low-density ones. The average frequency of types indicated early shifts in weed community structure. In conclusion, continuous cereal–field bean intercropping controlled weeds more effectively than rotated sole crops, with a slight decline in species richness and minor shifts in functional composition.