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.
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| 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.
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| 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:
- 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.
- 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.
- 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
