Mapping hill country soil temperature and moisture

Mapping hill country soil temperature and moisture

Farm scale mapping of key soil properties provides robust information to inform decision making tools

Tools are needed to estimate pasture yields and determine the suitability of forage legumes in diverse landscapes. To make these tools more robust, data needs to be collected at the farm scale, particularly when considering New Zealand’s diverse hill-country landscapes.

Data on soil temperature and moisture dynamics are particularly important as these micro-indicators are key drivers of many soil and plant processes.

Wireless sensor networks (WSN) accommodating hill country topography challenges were installed at six sites across New Zealand

Previously the best available source of climate information in New Zealand was NIWA’s Virtual Climate Station Network (VCSN). The VCSN provides daily estimates of a range of climate variables, including soil temperature and soil moisture, on a 5,000 m square grid.

New Zealand’s hill country landscapes are diverse and soil conditions can vary markedly with topography over distances much shorter than 5,000 m. Existing climate variable estimates do not account for the influence of topography especially effects related to the direction a slope faces. This makes them unsatisfactory for hill-country pasture management. Farm-scale mapping of soil properties is better suited to a grid resolution of 100 m square or smaller.

Each WSN had twenty sensor nodes that were designed to make hourly measurements of soil temperature and moisture at 30 cm depth and transmit the data to a cloud database. At each site, the sensors were distributed in order to account for the variation in important topographic variables including elevation and aspect.

The sensor nodes were famously constructed by Jagath Ekanayake in his living room during New Zealand’s first COVID-19 lockdown in April 2020, a feat which was noticed by the Smithsonian Institution.

Farm-scale maps for soil temperature and moisture are now available to drive yield models and help inform decision-making on pasture management

Daily maps of soil properties were produced at a grid resolution of 30 m, showing that soil temperature and moisture can be mapped at the farm scale in New Zealand hill country.

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A big thank you to Nathan Odgers (Manaaki Whenua - Landcare Research) for taking the lead on this project for New Zealand's sheep and beef farming community. Special thanks to the farmers who actively supported this work.


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