Drought and Low Temperatures = Double Whammy

This blog continues my last discussion of what is now recognised as a drought ("A period (long) of dry weather that is harmful to crops").  In North Canterbury it is the worst since 1997-98.  Two months into autumn and a drought’s worst enemy is omnipresent – cold soil temperatures on top of large soil moisture deficit.  Soil moisture deficit is still significant (70mm over the depth 0-200cm in the example shown) despite rainfall of 35mm.  What little is now growing at this site has resulted in reducing the deficit by about 25mm from the wilting point soil moisture content in early March.  

Time plot of soil moisture (mm) near Christchurch

The rainfall events are from the southerly quarter and are associated with cold temperatures.  Soil temperatures fell to below 10°C at 9am for consecutive days – the first time since October 2014.  Low soil temperatures and continued soil moisture deficit (especially in North Canterbury) is bad news for unirrigated farmers.  The soil moisture deficit is bad enough, but coupled with low soil temperatures makes for a double whammy.

Blog post by Dr Anthony Davoren from HydroServices Ltd

Variable Rate Irrigation Visionaries - Brian and Jo Bosch

As promised we take a visit to South Wairarapa where the first Growsmart Precision VRI system was installed by dairy farmers Brian and Jo Bosch. The system helps them to use their water more efficiently, saving electricity, track maintenance and reducing the number of lame cows in their herd.

The couple, who have 1150 cows, producing 400,000kg MS annually off their 320ha milking platform, have three centre pivots irrigating 210ha, one of which has VRI installed.

Overlooking part of the Bosch's dairy farm in South Wairarapa
(Photo courtesy of Rebecca Harper)

The Growsmart Precision VRI system was installed in 2008 by Precision Irrigation, now known as Lindsay NZ.

“The reason I was keen on getting into it was we were having issues when the pivots crossed the tracks. We’d have a nice crowned track and water would run off into the water table, causing bad pivot ruts,” Brian says.

Not only did this hinder the performance of the pivots but it meant high track maintenance costs and increased numbers of lame cows.

With the VRI installed, Brian is able to turn the pivot off as it goes over the tracks. “Now the tracks are dry and we have no damage. There’s no damage to the cows’ feet.”

The Bosch's also have a large pond under the pivot and a number of open drains. They are able to turn the pivot off when it is over these as well, meaning the water is not pumped to waste.

“I worked out that the tracks, pond and drains probably add up to 10% of the land under that pivot, so we can go and irrigate 10% more productive land now. It actually costs us to irrigate the track because we get more lame cows and do more track maintenance.”

“They (Lindsay NZ) put the programme in and I haven’t fiddled with it too much. I recently started upgrading to the latest version and they provide training for that.

“There’s been no maintenance, this upgrade is the first money I’ve spent on it since installation – it’s just the software that needs upgrading, the hardware is fine. It’s just worked.”

Brian Bosch has plenty to smile about as the Growsmart Precision VRI system has been working a treat since being installed back in 2008. Resulting in significant savings in track maintenance costs, reduced cow lameness issues and the ability to spread his irrigation water further.
(Photo courtesy of Rebecca Harper)

Installing VRI has been a worthwhile exercise, Brian says, and he can see the future benefits too. “Going forward with the council, and for your own peace of mind, you can show you are using water efficiently on your farm and prove to council you’re not wasting water.”

Post bought to you by Sarah Elliot from Lindsay NZ

Variable Rate Irrigation and the Big Picture

Variable rate irrigation (VRI) has been mentioned in several posts to date, however we have not yet formally introduced the technology or the key to its potential benefits in farming. So we will start by looking at the big picture to hopefully provide you with some context to place this innovative irrigation technology. 

Irrigation demands about 80% of allocated freshwaters in New Zealand, which is similar to the global average; and the area of irrigated land in New Zealand has roughly doubled every decade since the 1960s. As the demand on freshwater increases so are the restrictions and charges placed on it. Farmers are realising the value of increasing their irrigation efficiency to ensure the long term sustainability of their freshwater, improve their nutrient management and decrease their water costs.

Efficient water management plays an important role in irrigated agricultural systems. Under conventional blanket irrigation (uniform rate irrigation or URI) many parts of irrigated fields are effectively over or under-irrigated due to spatial variability in soil available water-holding capacity, water infiltration rates and topography. Under-irrigated areas are subject to water stress, resulting in production loss, while over-irrigated areas suffer from poor plant health and nutrient leaching. 

Variable rate irrigation (VRI) addresses the need to achieve irrigation efficiency, aiming for best conversion of each millimetre of irrigation water to pasture growth. Irrigation efficiency is commonly referred to as application efficiency and depends on three main factors:

·         Applying the correct depth of water

·         Uniformity of application

·         The rate at which water is applied to the soil

Furthermore application efficiency is known as the percentage of applied water that is retained in the root zone or in the target area, after an irrigation event. Variable rate irrigation allows for irrigation efficiency of centre-pivot or linear-move irrigators to be optimised. This can be achieved through using a VRI system alongside soil mapping technology and site specific moisture monitoring. 

The Growsmart Precision VRI system was developed in Manawatu (New Zealand) by a team of talented engineers from farming backgrounds. The technology they developed is world-leading and the first system of its kind offering individual sprinkler control of the entire irrigator. This  allows farmers to apply exactly the right amount of water to specific management zones, giving full control to maximise yields and profitability.

Brian Bosch installed the first Growsmart Precision VRI system on his dairy farm in Wairarapa (NZ)

While there are many advantages of the Growsmart Precision VRI system that will be explored in greater detail in later blog posts one significant advantage is the understanding and support of the team that develop and manufacture the technology and the Zimmatic dealerships that sell and support he product. The team are passionate about precision agriculture and how it can be used to aid in the sustainable use of resources. And I will share with you some insider knowledge – a major focus of the current product development is based around this very premise.

In upcoming posts you will be introduced to some of the early adopters of the Growsmart Precision VRI technology to hear their story of how they have used the system to their advantage. To make sure you are notified when these stories come out subscribe to this blog by entering your email address in the box at the top right or "Like" the Growsmart Precision VRI Facebook Page. If you are wanting more information about the technology beforehand then visit www.growsmartprecisionvri.co.nz. 

This post was written by Nicole Mesman and Sarah Elliot from Lindsay NZ :)

The best time to get your farm EM Surveyed

Okay. So, you’ve decided to EM survey an area of your farm, but aren’t sure when is the best time to do it. Not only at what time of year but also in relation to the planning of your irrigation development.

The first decision, what time of year, is relatively easy to determine. Here at Agri Optics NZ we recommend conducting a survey outside the irrigation season - before you start or after you finish irrigating, ideally when the paddocks are naturally nearer their peak water holding capacity. This ensures that any man-made influence from your irrigation system is not showing through in the survey results. By waiting until the ground has had a couple of good rain events this will bring the soil back to its natural state.

 The image below shows on the left an EM survey conducted at the right time of year (top map being the 0-50cm profile and the bottom one the 0-125cm soil profile) conducted in 2013, while the image on the right show the same paddock with EM survey conducted in February 2015, undertaken as an experiment. This highlights why Agri Optics do not recommend conducting EM surveys in the summer when land is being irrigated.

Comparison between EM Surveying conducted in winter (left) and summer (right) and different survey depths.

As you can see the influence of the pivot irrigation on the two maps on the right-hand side (especially the top map showing the shallow profile) is masking the true characteristics of the soil, not only on the dry red areas around the edge but also in the blue areas where there was run off and ponding.

The second timing decision lies around at what stage in your project development planning to do the survey. Should it be in the early planning stages or before or after building the pivot?

If you EM survey while still in the planning stages but before work starts then the elevation data recorded as part of the survey can be used to help with pivot design and help budgeting for any potential earth works, especially on hilly ground. This can help your pivot designers enormously, and also at this early stage give a good indication on how much savings can be made by varying your water to the soil’s requirements under the pivot footprint. A note of caution though, if you plan on doing major earth works then be aware that you will be removing the soil the EM survey has based upon and this can alter how relevant the EM map will be to your final soil profile.

If the EM survey is conducted after the pivot is up and running, but before the Variable Rate Irrigation (VRI) system is purchased, the Information from the survey can be used to see what the gains are from varying water application across your different soil zones.  By using Agri Optics VA Gateway software we can show you the payback time of implementing VRI based on the initial variability and what a return on investment is likely to be for your specific situation.

An EM survey can also be undertaken after VRI is already fitted, where it’s existing use is for the management of avoidance zones such as lanes and waterways. With the data from an EM survey you can then tweak your applications to match the soil types within your current setup. By going down this route you will already be familiar with the VRI software before introducing the application maps from your EM data and making the step up to site specific management.

Here at Agri Optics we’re happy to give you our independent advice, helping you make the right decision for your farm and business, providing you with a truly sustainable solution – sustainable for your land and for your business. You can find our contact details here