Water productivity in practice

Where should growers focus their attention to get the best returns on their irrigation water? By Anna Mouton.

Danie Viljoen is the production manager at Lushof in Prins Alfred Hamlet. The farm was the birthplace of the vertically integrated fruit-production company Graaff Fruit. Today Lushof includes 175 hectares of pome- and stone-fruit orchards. Fruit is grown primarily for export and for Woolworths.

“We started looking at using water more efficiently because of Woolworths and their Farming-for-the-Future audit,” recalls Viljoen, “and because of the water stewardship programme of WWF — the World Wide Fund for Nature.” He says that the 2015 drought brought home the need for these programmes. “It made it more real for us — so much so that we began innovating around water use.”

According to Viljoen, there are three main focus areas when using water productively — systems, records, and planning.

Pumps and pipes

Most of the water at Lushof comes from three water schemes in the Ceres area, and is collected on Lushof in a dam that holds about 1.3 million cubic metres. Groundwater at Lushof is brackish and not used for irrigation.

“The maintenance of our irrigation system — pumps, pipes, inlets, outlets, ensuring correct flows — is something we do continuously,” says Viljoen. He and his team are always on the lookout for ways to improve the consistency and efficiency of water delivery. For example, they upgraded all their filter stations to replace wasteful and ineffective sand filters. Viljoen also describes how servicing pumps improves water delivery and saves energy.

“We have a booster pump on our one system, and it usually comes on when more than a certain number of valves are open. After we serviced the feed pumps, our guys thought the booster pump was faulty, because it didn’t switch on. But it wasn’t faulty — it was just that the feed pumps were so much more efficient after their service.”

Upgrading the system is expensive, admits Viljoen, but it can be done gradually. He has converted two orchards to drip irrigation this season, and he believes this will result in substantial water savings compared to the previous system, which was old. “I believe that by doing all these things we will be far more sustainable going forward,” he says.

An eye on the numbers

Measurement is key to management, and Viljoen keeps a close eye on irrigation records. He downloads the numbers from his irrigation computers every Monday morning, to assess how much water each block received, and how this compares to the budget for that orchard. He also has someone in the field collecting data and uploading it to the cloud.

“I use Excel for all my analyses,” says Viljoen, “so I pull all this together using power queries to see how orchards compare to one another, and to their budget. And then, if I spot some anomalies, I get in my bakkie and I drive to those spots in the orchard. You have to watch your data, monitor constantly, and keep your finger on the pulse.”

Lushof has a 10-year water budget that is updated every year. The budget includes estimates of income per cubic metre of water. “We have a sum that we make — how many litres of water does it take to produce a fruit?” explains Viljoen. He points out that water productivity at the fruit level can change exponentially depending on cultivar selection.

“When we look at cultivars in the trial block, my first question is, how much fruit does this cultivar produce? If a cultivar sets poorly, or has a poor yield, I back off immediately, because I can’t utilise my most limiting resource — water — effectively with something which doesn’t give me fruit.”

Plan for success

It’s all too easy to get caught up in the excitement of new cultivars, and the fear of losing out, cautions Viljoen. He highlights the importance of selecting cultivars and rootstocks based on data, and ignoring uninformed popular opinion.

“If you talk to guys who are pulling out orchards, it’s almost never because the trees were too old,” says Viljoen. “It’s because it was the wrong cultivar, or the wrong rootstock, or incorrect irrigation.” The key to orchards with long productive lives is good planning — and that must include assessing economic and physical water productivity.

“We used to plant more than our capacity, without realising it. But when the 2015 drought struck, we weren’t able to get by on our available water, and we started making the sums,” recalls Viljoen.

These sums included looking at the relationship between water used and income generated — economic water productivity — for different orchards. Cultivars that were losing the most money were the first to go. Whereas in the past the dam at Lushof was empty at the end of the season, there is now a buffer of 10%–15% at the start of winter.

Viljoen also takes great care with orchard establishment. He employs a soil scientist to survey the orchard, as well as consulting some of the older people on the farm, before installing drainage and irrigation. Trees are planted in April from pots.

When asked about the secrets of optimal water use, Viljoen singles out the human factor. “I can’t do everything myself, it’s impossible. So I try to pass my insights onto my managers, so that they also spot any waste, and fix it.”

Lushof survived the 2015 drought, but not without stressing some trees. It took about three years for production to return to normal. However, lessons were learnt, and Viljoen is confident that Lushof has made changes for the better. “We will have droughts again — they haven’t disappeared. But when the next drought comes, we’ll know what to do.”

Water-use efficiency versus water productivity

Water-use efficiency in crop production is the ratio of water used in plant metabolism to water lost through transpiration. Photosynthetic water-use efficiency is a measure of carbon assimilation relative to water transpired. Productive water-use efficiency is a measure of biomass produced relative to unit water transpired.

Water productivity is output divided by water used to achieve that Economic water productivity is a measure of income per unit water. Physical water productivity is a measure of production — for example kilograms of fruit — per unit water.

For more about water use and water productivity in apple orchards, read Thirst Trap in the September 2018 issue of Fresh Quarterly.

Image: The farm Lushof in Prins Alfred Hamlet.

Supplied by Danie Viljoen | Graaff Fruit.