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Successfully using precision agriculture technnology already on two of their cropping centre pivots, it was an easy decision for the Mitchell and Webster Group to invest again; this time on their dairy farm. The Group is owned and operated by two families, the Mitchells and the Websters, with 1400 hectares of cropping land around North Otago. In the last two years they have converted 200 hectares of cropping land to dairy and have invested in Electro-magnetic (EM) soil surveys by Agri Optics NZ Ltd and Growsmart Precision VRI technology for the two centre pivots which cover 100 hectares of the dairy farm.
The use of precision agriculture technology on the dairy farm has allowed the Mitchell and Webster Group to irrigate more efficiently through their pivots. They have been able to reduce the amount of water they apply through their pivots while still maintaining soil moisture levels for pasture growth. They now use the water they have saved to irrigate an additional 15 hectares with K-lines. By irrigating this additional area they are able to increase pasture production by 6 tonnes of DM (Dry Matter) per hectare giving them an additional 90 tonnes DM per season and resulting in a subsequent increase in MS (Milk Solids) production. Given a long term payout average of $6/kg MS their expected increase in revenue is $40,0001, a 40% ROI. In addition the Growsmart Precision VRI has meant that the Group is able to apply effluent in accordance with consent conditions and avoid application over the drains and environmentally sensitve areas.
1Assuming 15% DM wastage and 11.4 kg DM eaten to produce 1 kg MS
With an annual rainfall of 400-500 mm and a range in summer rainfall from 10 mm – 240 mm (October – April)2 irrigation is central to achieving production targets. The Group aims to increase cow numbers to 750 cows in order to attain a total output goal of 300,000 kg MS. However water is also expenisve and financial returns are dependent on efficient irrigation and minimising the number of irrigation shares required by the operation.
2Rainfall data from Grow Otago and NIWA regional rainfall recordings
1 – Assuming 15% DM wastage and 11.4 kg DM eaten to produce 1 kg MS 2 – Rainfall data from Grow Otago and NIWA regional rainfall recordings
Figure 1 – EM soil survey of the Webster and Mitchell dairy farm showing the two Growsmart Precision VRI pivots, Dog Town and Hillbrook with a soil moisture sensor under the Dog Town pivot.
The EM soil survey of the property (Figure 1) defines soil texture zones which can be used to further increase irrigation efficiency on the property.
An interesting feature of the farm is the presence of springs that make themselves known through the lime rich, calcareous parent material and mean that the already heavy clay soils become water logged as they shrink and swell. Precision agriculture technology means that ongoing farm maintenance costs can be reduced as irrigation is avoided over areas that are identified as more prone to waterlogging, helping to maintain soil structure and reduce pugging damage.
Figure 2 – Soil moisture sensor under the Dog Town VRI pivot showing that soil moisture levels for the first 3 weeks in February are within the desired range.
To assist with the problem of waterlogging and try to remedy the presence of springs on the property the Group have installed Novaflow drains which they can create avoid zones for on their Growsmart Precision VRI programme. By creating avoid zones for a total of 12.6 hectares, of drains and other sensitive areas across both the pivots, the Group is able to apply effluent through their system in accordance with their effluent consent conditions from the Otago Regional Council (ORC).
From a nutrient leaching perspective the ORC has defined nitrate leaching limits as 20 kgN per hectare per year, for areas surrounding sensitive aquifers, and 30 kgN per hectare per year for the rest of Otago. Co-owner Peter Mitchell describes the benefits of precision agriculture as “savings both environmentally and financially”. He believes that the system will help the Group to meet these environmetal restrictions on their dairy property. Given the high costs of water in the region Peter notes that “the main driver for precision technology is financial however we also want to do what is best by our land”.