Tuesday 24 March 2015

Information Aplenty for Farmers at the Sustainable Irrigation Field Day

The Sustainable Irrigation field day last Wednesday saw an excess of 50 attendees interested in learning more about variable rate irrigation (VRI), electro-magnetic (EM) mapping and soil moisture measurement technologies. Hosts Peter Mitchell and Nick Webster of North Otago’s Mitchell and Webster Ltd noted that there was a strong contingency of farmers in the turnout which was very encouraging. Farmers are hearing about the benefits and thinking more seriously about precision ag technology as a means of helping them increase resource efficiency and revenue.

Jemma Mulvihill (Agri Optics New Zealand Ltd) discusses EM mapping and how the data can be used to make informed irrigation scheduling decisions.
The afternoon was held at the Mitchell and Webster Ltd’s Dairy farm in Enfield, inland of Oamaru, which was converted from cropping two years ago, with Growsmart Precision VRI systems installed on their two centre pivots covering 100 hectares of the property and EM mapping by Agri Optics Ltd for the majority of the farm. Peter and Nick started off the series of talks with a run through of the farming system and the use of precision ag technology on the farm. The farm covers 200 hectares and soils generally have a high clay content with drains installed across the property to both decrease waterlogging and negate the presence of seasonal springs.

Nicole Mesman (Lindsay NZ) presented the key findings from the joint Lindsay NZ (formally Precision Irrigation) and Agri Optics summer case studies carried out on the Mitchell and Webster Ltd Dairy and McCarthy cropping block. The studies showed that use of Growsmart Precision VRI on the dairy farm allowed for more efficient irrigation and resulted in enough water being saved to irrigate an additional 15 hectares using K-lines. Assuming an increase in production with irrigation of 6 tonnes DM per hectare, long term average payout of $6/kg MS and 15% DM wastage and 11.4 kg DM eaten to produce 1 kg MS additional revenue as a result of VRI was calculated to be $40,000. The cost for VRI and EM mapping on the property totalled $100,000 therefore this represents a 40% ROI. EM mapping has also allowed for identify soil zones to further increase irrigation efficiency and has allowed for identifying areas to put soil moisture sensors in.

Nicole and Peter installing soil moisture
sensors at the McCarthy cropping block.
On the McCarthy block the centre pivot with Precision VRI installed covers 82.5 hectares of rolling hillside and alongside EM mapping has resulted in a reduction in water usage from 34 l/s to 26 l/s. This is from avoiding irrigating 7.5 hectares of springs and ditches and varying irrigation application based on soil texture as well as topography and topsoil depth (influenced by aspect). Annual savings on the property total $39,500 due to both decreased water charges and increase in production.

Paul Reese, Projects Manager with Irrigation NZ discussed the findings of the Sustainable Farming Fund – Hill Country Irrigation project that concluded near the end of 2014. The research trial investigated irrigating hill country (slopes between 16° and 25°) and as a result produced a resource book ‘Irrigation on Hills’ from the findings (available from IrrigationNZ). Key findings include the need to recognise that runoff on hills takes place throughout the soil profile, not just on the surface. Therefore application intensity must equal or be less than the slowest permeable layer in the profile.
Environmental considerations for the region were presented by James White (Otago Regional Council, ORC) and Dylan Robertson (North Otago Irrigation Company, NOIC). The ORC Water Plan rules related to irrigation fall into three main areas:
  1. Discharges of effluent, silage or composting materials are prohibited directly to a waterway, to a bore or soak hole, to land 50 m of a river, to saturated soils, at a rate causing ponding.
  2. Surface water discharges – must ensure discharges to rivers comply with Schedule 16 thresholds and that nutrient levels in rivers also comply with Schedule 16 thresholds for 2020.
  3. Discharges to groundwater – landowner must identify what zone property is in, for instance 15, 20 or 30 kgN/ha/yr and monitor system nitrate leaching using Overseer in order to achieve compliance when these limits become compulsory in 2020.

Efficient and accurate irrigation is essential to achieving regional targets for water quality. More information on Schedule 16, Regional Water Plan can be found here. Landowners can also request a Fact pack with information regarding regional rules.

NOIC are proactive in encouraging shareholders to comply with regional environmental standards by providing assistance for those wishing to undertake water testing. They offer support to shareholders looking at completing Farm Environment Plans, a template is available to help ensure they meet requirements. 

Posted today by Nicole Mesman and Sarah Elliot from Lindsay NZ