Satellite Radar Maps Crop Changes in South Africa's Maize Triangle

Radar data from the National Aeronautics and Space Administration-Indian Space Research Organisation Synthetic Aperture Radar (NISAR) satellite reveal detailed crop types and their changes in South Africa's Maize Triangle. This agricultural region is located in the Free State province, near the Vetrivier (Vet River). The data were collected over ten passes between November 2025 and March 2026.

The visualization uses a false-color composite. Green indicates vegetated areas. Red represents unvegetated surfaces. Blue shows how rapidly vegetated areas changed over the season.

Stable vegetation, such as forests, appears with a light blue component. Plants that change structure throughout the season, like wheat and maize (corn), have a darker blue component. Pixels often contain a mix of these colors, creating a varied palette.

For example, fields with plants that grow rapidly and are harvested early appear orange. Sunflowers are known to exhibit this pattern in the region. Ground validation would be needed to confirm specific crop types in individual fields.

NISAR's L-band radar observations measure vegetation structure. Scientists analyzed these observations to produce statistical measures for each pixel. Combining radar scattering behaviors from multiple dates created a summary of seasonal agricultural activity and change.

This technique offers a repeatable method for monitoring crop development, irrigation impacts, and land-use changes across large areas. Future NISAR data will allow researchers to compare seasons and track growth patterns. This will help understand how agricultural systems respond to water availability and climate variability.