Southland Soils and Warmth Map

This map brings together two things: the soil and the warmth available for plant growth. Both come from the Topoclimate South project, which surveyed the soils and climate of farmland in Southland between 1998 and 2001.

Soils.

The soil survey covered about 825,000 ha of intensively farmed land. Soil scientists made more than 10,300 auger observations and dug over 650 soil pits, describing soils to 1m depth and identifying 175 soil types.

Click an area to see its soil type, slope and depth. Each soil type links to its Information Sheet, a plain-language summary of the soil's properties, limitations and management. Less common soils without their own sheet link to a general minor soils sheet.

Warmth: growing degree days (GDD)

Growing Degree Days (GDD) measure accumulated warmth. Each day adds its average air temperature above 4°C, so a day averaging 10°C adds 6, and a day averaging 3°C adds nothing. Higher numbers mean more warmth, faster growth and crop development. 4°C is roughly the temperature at which pasture starts to grow.

How GDD is calculated

The heat information comes from about 2523 air-temperature loggers that were moved around the region between 1998 and 2001, placed on flats, terraces and hills with different slopes, aspects and shelter. Their records were linked to long-running climate stations to estimate long-term average conditions.

• Yearly GDD: the long-term average total for the year, mapped in bands of 50 GDD.
• Seasonal GDD: the seasonal range (Spring: Sep–Nov, Summer: Dec–Feb, Autumn: Mar–May, Winter: Jun–Aug) in the same yearly band.

Using this map

• Soil ratings describe the typical soil of each type under minimal management. Drained or improved land may perform better than shown. Where an area contains more than one soil, the details describe the main (dominant) soil.
• GDD measures warmth only. It does not show frost risk: even a warm area can get damaging frosts, especially in low-lying spots such as hollows, gullies and valley floors, where cold air tends to pool. It also does not show water, sunshine or wind, which affect growth too.
• Use both layers as a guide for planning, not for paddock-scale decisions, which need a check on the ground and local advice.

Soil maps © Topoclimate South Trust. Soil Information Sheets © Crops for Southland.