Slee Hi-Tech Dairy Irrigation

Mark and Devon Slee run a large dairying business with a particular focus on efficient use of water and effluent.

Mark spent 12 years as a director on the Mayfield Hinds Scheme, and has been a board member of Irrigation NZ for the past six years. Part of his work on the Mayfield Hinds Scheme was as a delegate to the Rangitata Diversion Race, which supplies water to three irrigation schemes as well as stock water for Mid Canterbury, and supplies water to hydro generator TrustPower which has two power stations in the area. At the moment his only position is on the Irrigation NZ board.

Mark and Devon have been farming here and dairying since 1990. Originally the whole farm was border dyke irrigation, which was typical of the district.

“I was a director on the Mayfield Hinds local irrigation scheme, I could see the huge benefits of the change from border dyke to spray irrigation:

* a production benefit,

* better use of water,

* giving better use of nutrients,

* potentially growing more grass.

We changed to pivots in 2000. We bought a neighbouring, predominantly dryland property and we put centre pivots on there. When we realised how well it worked, we started developing the home farm.

We were one of the earlier farms to go from border dyke to pivots; a few people thought we were mad at the start. We were also on restrictions, and if the river dropped below 32 cumecs we would have no water. That was a good incentive to drive efficiencies.

Border dyke suits heavy soil types which can take the flow. Our soils are very light Lismore stony silt loams. Our rainfall is 600mm/year, and it is evenly spread throughout the year. We can probably lose 5mm a day in evapotranspiration in midsummer, so that adds up to 100mm ET over each summer month, which builds up to quite a deficit. Even putting on 5mm on a hot day you could be going backwards.”

As a result, they put on 300 to 500mm by irrigation a year, but have low application rates.

“The beauty of a centre pivot is that it only puts on 5mm/day, which is a really light application. You can cover the farm in a 24 hour period. This keeps the soil profile topped up without losing anything through drainage.”

Instead of applying water every day, they apply 15mm every three days.

“The soil water holding capacity is 60-65mm, and there is probably about 30mm available water. So we are putting on half of what the soil can hold.”

The 890ha farm is virtually fully irrigated, with only 10-15ha of small dry corners not irrigated. Three dairy sheds milk 2500 cows, and there are seven pivot irrigators.

“We have four storage ponds for on-farm water storage, and they give us about on average 10 days of water for irrigation. It is small scale but it does give us a buffer.

We have five Aquaflex sites measuring soil moisture. These give consistent soil moisture readings. They also give soil temperature readings. Our springs can be quite cold, and if it is too cold and dry, irrigation doesn’t necessarily help.

We have stony soils with only about 300mm of topsoil. About 20 years ago we only had around 200mm of topsoil; slowly the organic matter level has been building up under dairying.

We use a weather forecasting service on a reasonably regular basis through the internet. The local Ashburton Trading Society (ATS) has its own weather and prediction service which is pretty good actually. It has two climate sites at Timaru and Rakaia, and they tell you for example that next Wednesday you can expect 10-20mm of rain. We look out 10 days, and that will give us an indication of what is happening in terms of how much rainfall we are likely to get. They indicate there might be a 90% chance of rain.

The effluent goes through three centre pivots and is spread very thinly over the farm from the three dairy sheds.”

Traditionally dairy farmers have spread all their dairy shed effluent on a small area of land, but now more farms are using irrigators to cover a bigger area. This also reduces the likelihood of leaching occurring.

“We benchmark our water use. The irrigation scheme gives us the amount of water used each year so we can see where we are in comparison to other water users. From those figures we are pretty confident that what we are doing is close to best practice. At the end of the day we are trying to run a proper business and there is no real advantage in wasting water.

We are at the low end of the scheme water use because we have centre pivots. We still have a surface water take and are only pumping water with a surface pump, so our electricity costs are quite low compared to those who pump out of deep wells.

At the moment we have one pivot on a variable rate pump, but our others are on a standard rate.”

We are using Tracmap GPS system which maps, for example where we have been with the fertiliser truck. Now we have a unit on the quad bike and we are using it for shifting K-line sprinklers so we can move them to exactly the right spot.”

With the pivots we have taken out a lot of trees, because centre pivots don’t like trees. We had a lot of really old trees on this property, and we have put in 10,000 natives to create low shelter beneath the pivots. These are now in their third year.

Nurseries are starting to realise that some varieties grow better under the pivots than others. We’ve had some frost damage and hare damage. They have been quite destructive, so now we use protection against them.

We are looking at using variable rate irrigation on some of our pivots, which is another way of saving water. The sprinklers would turn off when the pivot reached crossings over tracks and laneways.

The cost benefit return on it would be quite slow, but one of the pivots crosses four lanes which would be a potential water saving.

The next step is putting more efficient irrigation into each corner, possibly using some small pivots to in-fill existing dryland .

The beauty of the pivots is that they have improved our reliability and probably increased our productivity by 30%. Our average growth on our ryegrass pastures is 12-13tDM/ha/year, and it might have been pushed out by 30% to 15 or 16tDM/ha/year.

While providing more feed on the same area probably does create a more intensive operation, and might possibly seen as a negative, the flip side of that is less nutrients are being leached out under centre pivots rather than border dykes.”

Tom Lambie, Environment Canterbury Commissioner says that Mark’s operation is exemplary. “He is in the top 5% of operators and is one of the really early adopters of new technology. He is identifying that border dyke irrigation on light ground is crazy. Border dyke irrigation on really heavy ground can be quite efficient, but on Mark’s land it doesn’t make any sense – because it wastes too much water with leakage.

We don’t want leaky dairy farms because leaky dairy farms don’t make money. We want to keep irrigation water on the ground, in the soil and not leaking out the bottom of the profile. We have to become smarter farmers, and because of our relatively low rainfall of 500-600mm in Canterbury we can control more of our environment by controlling the irrigation.

At Environment Canterbury we are trying to empower local communities to look after their own water, to have discussions about water and to make changes and adopt new technologies. In the last 15 months we now have 10 different local zones, including the Ashburton zone, where communities are now working together on water issues instead of being at loggerheads. “