Agronomic trait plasticity of 8 wheat cultivars when grown in 2-components cultivar mixtures in Switzerland from 2021 to 2023

This dataset contains data regarding the plasticity of agronomic traits of 8 Swiss winter wheat cultivars in response to growing in a mixture compared to a pure stand. The data includes results from field trials at 3 locations in Switzerland during 3 growing seasons (2021-2023). This dataset has been used to analyse the mechanisms underlying overyielding effects in wheat cultivar mixtures, which is published in https://doi.org/10.1007/s13593-025-01051-0. 

The dataset notably contains cultivar-specific ear density, biomass, yield, protein content, thousand kernel weight, in pure stands and in 2-cultivar mixtures. 

The field trials were performed under the Swiss Extenso (low input) conditions, conducted by Agroscope and DSP. 

Methods 

Field trials 

The experimental design consisted of all the varieties grown in pure stands, and all the possible 2-variety mixtures of one awned variety with an awnless variety, leading to a total of 15 mixtures. We focused on the 2-variety mixtures of one awned and one awnless variety in order to be able to visually distinguish and separate the varieties. Each pure stand and mixture were grown in plots of 7.05 m² (1.5m × 4.7m). We replicated the experiment three times per site with the exact same variety and mixture composition, a complete randomized block design. Sowing density was 350 viable seeds/m² for each pure stand and mixture plots. For the mixtures, seeds were mixed beforehand at a 50% mass ratio for 2-variety mixtures, e.g., 100 g of variety A was mixed with 100 g of variety B. This means that the sowing densities of each variety in mixture varied depending on the mixture, with the total sowing density remaining 350 seeds/m². Plots were sowed mechanically each autumn and fertilized with ammonium nitrate at a rate of 140 N/ha in 3 applications on all sites (40 N/ha at tillering stage/BBCH 22–29; 60 N/ha at the beginning of stem elongation/BBCH 30–31; 40 N/ha at the flag leaf stage/BBCH 45–47). The trials were grown according to the Swiss Extenso scheme — i.e., without any fungicide, insecticide, or growth regulator. Weeds were regulated twice per season with the application of herbicides commonly used in Switzerland. Disease incidence was monitored throughout the growing seasons, but there were no major outbreaks in any of our field sites, and therefore disease incidence will not be presented here.

Plant height

In Changins, we measured plant height of five random individuals from each variety in each plot (i.e., in mixture plots and pure stands) at the phenology stage BBCH 69 (end of flowering). Plant height was measured in centimeters, from the ground to the top of the ears, including awns.

Yield 

At maturity, we manually harvested a strip of 30 cm × 1.5 m = 0.45 m² along the width of each plot by cutting all individuals (i.e., stems with ears) within the strip right above the ground. The harvested strip was located at more than 1 meter from the plot borders to avoid edge effect, and non-homogeneous parts of the plots were avoided. We subsequently air-dried the samples for two weeks. For pure stand samples, we counted the stems, weighted the total biomass, then threshed and weighted the grains. For mixture samples, we manually sorted the awned stems and ears from the awnless stems and ears. We counted the number of awned and awnless stems and ears in each sample and weighed the total biomass of the two varieties. We then separately threshed the awned and awnless individuals and subsequently weighed the grains in order to obtain the yields from the awned variety and from the awnless variety. Yield is therefore defined in our study as grain weight (kg).

Post-harvest analyses

Protein content (% of dry matter) was measured for each previously described grain samples (e.g., grains of each variety in pure stand, but also of each associated variety in mixture plots) with a near-infrared instrument (ProxiMateTM, Büchi instruments), and thousand kernel weight (TKW, g) with a Marvin seed analyzer (GTA Sensorik, Neubrandenburg, Germany).

Light competition trial 

In Changins, in 2021/2022, we grew single plants of each variety in full light and in shaded conditions to assess the phenological response of each variety to competition for light. The experiment took place in an outdoor agricultural field, where we covered the soil with a thin, dark, microperforated agricultural foil to avoid weed infestation. The agricultural foil contained one hole every 0.25 m², where varieties were grown as individual plants. Over half the soil surface, we constructed dome-shaped, metallic tunnels, which we covered with a shading net intercepting 66% of photosynthetically active radiation (PAR). Each variety was replicated five times per light treatment, with randomized blocks within each light treatment. The phenological development of each plant following the BBCH scale was regularly assessed (i.e., every 2–3 days).