Tuesday 22 November 2016

Legumes + Efficient Water Use = Great Results at Omarama Station

Omarama Station recently played host to the "Legumes in the High Country" field day, organised by Lincoln University and Beef + Lamb NZ. There was a good turnout of farmers and industry professionals to the farm owned and run by Richard and Annabelle Subtil, 2015 winners of the South Island Farmer of the Year competition. The focus for the day was the use of legume species in the high country environment with a short session on the use of irrigation and soil moisture monitoring in the arid environment that is the Mackenzie Country.

Omarama Station (Courtesty of Richard Subtil)
Omarama Station covers 12,000ha with a mixture of dryland high country and irrigated flats. The property has had significant development work undertaken and a number of centre pivot irrigators installed that irrigate 560ha. A large water storage pond has been constructed to supply water to the irrigation system.

Dr MS Srinivasan from NIWA gave the first presentation for the day at the site of the lysimeter that has recently been installed on the station. The lysimeter is the first in the Waitaki catchment and aims to build knowledge around drainage and soil water under the developing soils at Omarama Station. The site contains three catchment sleeves one of which has soil moisture sensors installed. Any drainage water from the site is measured which gives an indication of the soil moisture status and how drainage from the soil profile is taking place.

From a soil moisture point of view the lysimeter is important as the soils at Omarama Station have exceptionally variable fertility, structure and water holding capacity. Irrigation is not new to the area however the shift from border-dyke irrigation to more efficient spray irrigation has seen a massive change in the water use efficiency on extensive properties such as Omarama Station. Soil development under irrigation is an interesting concept and soils mapped on Omarama Station have shown to have varying levels of water holding capacity based on how long they have been irrigated for in the past. Investigation has shown that the depth of soil and the water holding capacity has improved under 30 years of irrigation. 

Irrigation at Omarama Station (Courtesy of Richard Subtil)
Agri Optics has installed three sub-surface AquaCheck probes that will complement the work being undertaken at the lysimeter site. This information will flow into the decision making process that is used around timing and quantity of irrigation water applied by the team at Omarama Station. 

Derrick Moot spoke on how selection of species was important to maximising water use efficiency in moisture deficient environments such as the Mackenzie Basin. As we know lucerne is a great fit into dryland high country systems. It has the ability to maximise the water use efficiency and has a high water to dry matter conversion ratio (kg DM/mm/ha). The selection of species going forward and the development of novel species all points towards maximising the efficiency of water use in dry high country areas.

Write up by Nick Evans