Friday, 29 May 2015

Evaluating Potential VRI Returns with an EM Survey

In the previous blog about the EM surveying service provided by Agri Optics I touched on an aspect of our software platform which helps you evaluate the variability in monetary terms. In this post I will go into it in more detail and explain how it can help you evaluate the likely financial benefits from the installation of VRI. This is another service that is unique to Agri Optics in New Zealand.

The VRI Design Evaluator allows you to enter the cost of your VRI system, (for example a  standard budgetary figure of $100/metre of pivot) then put your expected yield and value of crop – for example  wheat yielding 12 t/h at $400/t or grass at 25c per kgDM and 12,500kgDM/ha per year.
The software works on the theory that by not over watering the high EM areas or under watering the lighter low EM areas you are not inhibiting yield from water stress and therefore getting a yield penalty.  These areas will then yield more like the average EM area i.e. 12t/ha. By altering the water application to match the soil’s requirements you are reducing the effect of soil variability therefore gaining a greater yield, as there are no water based yield penalties.

This is a very useful tool for showing the amount of yield benefit that can be made by applying VRI to your lateral or pivot. However it doesn’t take into account the added benefits of savings in water, power, a quicker return time and in a dairy scenario reduced track maintenance, reduced lameness and the milk penalties tied to that. Nor does it take into account environmental benefits from reduced nutrient leaching or soil erosion.

In the screenshot above, using a yield of 12t/ha for wheat at a value of $400/t, a cost of VRI at $100/m (figures underlined in green) on a 476m pivot at a total cost of $47,696 (underlined in blue) there is an annual benefit in the region of $43,302 (underlined in red), so in this scenario the VRI system would pay for itself by the second year.

This can be very useful information for anyone who is trying to decide if VRI would work for them and is one of the options we can provide when conducting an EM survey.

Chris Smith - Agri Optics NZ Ltd.

Tuesday, 12 May 2015

Keeping it Green Where it Counts with VRI

Growsmart Precision VRI is one tool that may help farmers manage nutrient loss, as the ability to efficiently and effectively irrigate becomes increasingly important, Central Hawke’s Bay farmer Hugh Ritchie says.

In this weeks blog post we visit Hugh and Sharon Ritchie who operate Drumpeel Farms at Otane.  In 2014 they were winners of the Hawke’s Bay Farmer of the Year competition. Hugh was kind enough to offer his time and share with us the benefits of variable rate irrigation (VRI) at Drumpeel Farms, and the potential he sees for the technology in the future.

Hugh Ritchie says Growsmart Precision VRI is one tool that may help farmers manage nutrient loss.
(photo courtesy of Rebecca Greaves)
Drumpeel Farms comprises just over 2000 hectares of farmland between two blocks at Otane and Horonui. Cropping makes up a significant part of their operation and irrigation is key – with VRI used on both blocks. Growsmart Precision VRI has already enabled the Ritchies to eliminate overlap in their irrigation system, ensuring consistent application of water and a better return time to irrigate.

The cropping is focused at the Drumpeel block, which is 650ha. The Ritchies crop 850ha annually, with double crops. They currently have consent to irrigate 460ha and of that area, 160ha is under VRI. They have a towable pivot, a fixed pivot, a linear pivot, two hard hose with a gun and one hard hose with a boom.

Electro-magnetic mapping trials at their Wainui block, which had Growsmart Precision VRI installed by the previous owner in 2008, means there is potential to water according to soil type and depth in the future, as well as identifying leaching rates.

Soil type is an important consideration for Hugh. “Soil type is quite important and you have lower lying areas etc, so being able to manage areas is critical. We have different crops on different soil types with different water requirements,” he says.

“It’s been identified that with different soil types efficient and effective irrigation could be used to manage nutrient loss, and VRI is one of the tools that gives us the ability to do that."

“Going forward there’s a social contract that comes with the ability to utilise a public resource, like water. It’s an advantage to the farm but we have an obligation and commitment back to make sure we use that resource wisely."

“The biggest wastage of water is irrigating the driest point to wet enough, but the wetter areas get over-watered and that water goes down the drainage channels. That waste water can also flush nutrients and a badly run system can be very damaging. The concept of distribution uniformity is critical and VRI is a tool to help fine-tune that."

“It’s the invisible loss of water going to drainage because of overwatering that, in my mind, is a significant area that VRI can address. It’s going to be a very effective tool in the irrigation area to help manage nutrient loss.”

In an opinion piece published in Rural News, Waikato University agribusiness professor Jacqueline Rowarth commented on the issue of water quality, specifically the role VRI could play in maintaining water quality.

“The debate on water quality is important in the decisions about water storage and irrigation. Concerns hinge on the fear that increasing irrigation opportunities will lead to intensification in agriculture, resulting in more nutrient loss to waterways. What doesn't appear to have been considered is how irrigation water is applied on farm – yet research involving the Precision Agriculture Centre at Massey University, with researchers from Landcare, has shown that variable rate irrigation (VRI) has the potential to reduce nitrogen loss, reduce energy and water requirements, and increase production,” she said.

“VRI allows farmers to apply water only where necessary, avoiding leaching and surface runoff. Specifying type of irrigation involved in the proposed irrigation schemes could go a long way to alleviating community concerns about water quality.”

The Ritchies also installed VRI on their towable pivot three years ago, with an aim of increasing the return time. Working within their consent, VRI eliminated the overlap in their irrigation system, which has three positions, helping make the water go further.

“It (VRI) gives us ease of management. Better return times mean we can get better crops out of our soil types. VRI gives us an efficient and easy way to water." Says Ritchie
(photo courtesy of Rebecca Greaves)
“Before VRI we used to have an overlap. With VRI we were able to put bigger nozzles in the pivot and control the water flow…it meant we could get back to each place in six days, rather than losing time,” Hugh says.

“It means consistent application of water and the machines can speed up in places of overlap, which brings the return time down.”

Previously, some areas were receiving 48mls of water, areas that didn’t need it, while other areas didn’t get enough water and were too dry.

“VRI enabled a system to spread a little bit of water over a bigger area. Under our consent our water allocation is quite low, so it was about working out how to make 20 litres per second go as far as possible.”
For irrigation of large areas of land and ease of use VRI is great, Hugh says. He is also able to exclude areas from irrigation, like tracks and troughs.

“Once it’s up and running it’s a very good system and easy to follow on the menus. They have done a good job and they are still developing, which is great. They are responsive and the backup is good, but generally the product works very well.”

Growsmart Precision VRI technology was developed by Lindsay NZ (formally Precision Irrigation) and is available through Zimmatic Irrigation dealers. For more information about variable rate irrigation visit or contact your local Zimmatic dealer.