Digital Maps for Spatially Differentiated Assessment of Grassland Productivity

Grass grows on around 70% of Switzerland’s utilised agricultural area. Yields on these grasslands vary significantly. For the first time, an Agroscope study has calculated these yields in a spatially differentiated manner, making digital maps available for planning and farm extension services.

Permanent grasslands and meadows cover nearly two-thirds of the utilised agricultural area of Switzerland. In addition to this, just under 30% of arable land is used as ley. The productivity of these grasslands varies widely. For the first time, researchers from Agroscope have shown, in a spatially differentiated manner, just how strongly yields can vary from one site to another.

New model for site-specific assessment of grass yields

The aim of the study was to highlight regional yield patterns and to identify regions with differing production potential. For this, the researchers developed a model for the spatially differentiated assessment of grassland productivity in the plain, hill and mountain zones. The summer-pasturing area was not considered in this study.

The calculations were based on the utilised agricultural area of 2023. Yields were calculated using key figures from the ‘Principles of Agricultural Crop Fertilisation in Switzerland’ (PRIF, Chapter 9, ‘Fertilisation of Grassland’), which differentiate between altitudinal zones and usage intensities. These data were supplemented by expert knowledge and geodata on topography and climatic conditions. In a multistage process, the researchers first estimated the average grass yields and then adjusted these according to the site factors of solar radiation and drought.

Up to 60 million tonnes of grass per year

The study estimates annual grass production on an area of around 726,000 hectares at up to 60 million decitonnes of dry matter (dt DM). If the regional effects of solar radiation and drought are taken into account, this figure falls to approx. 57 million dt DM.

The differences between the individual areas are considerable: Depending on usage type and intensity, the modelled average yields range between 23 and 122 dt DM per hectare and year. After adjusting for both site factors, they range between 22 and 116 dt DM per hectare and year. The study therefore shows the necessity of taking site factors into account when assessing grass production.

Des cartes numériques pour la planification et la vulgarisation

Les cartes ainsi établies fournissent pour la première fois une image spatialement différenciée de la productivité des surfaces herbagères en Suisse. Les données numériques peuvent être intégrées dans des systèmes de gestion agricole et d’information, et aider les agricultrices et agriculteurs à planifier leur exploitation. Elles offrent en outre aux responsables politiques, aux autorités chargées de l’application de la législation et aux vulgarisateurs une base solide pour l’élaboration de stratégies et de mesures d’exploitation adaptées à chaque région.