Monitoring the key to reducing water use

<b>Monitoring the key to reducing water use</b>

Name: Brian Caddy
Current job title, winery & region: Riverland Grapegrower

By Sonya Logan

Tools that track soil moisture are far from new but with water for irrigation becoming increasingly scarce their usefulness is evermore apparent.

For proof, one need look no further than grapegrower Brian Caddy who was one of just a few Riverland grapegrowers who came through the 2007-08 season without needing to purchase temporary water to produce a commercial crop. By utilising his soil moisture monitors, Caddy ensured that his 32% allocation and 14ML of carryover water - giving him a total of 93.16ML - was more than sufficient to irrigate his 7ha vineyard and yield an average of 18t/ha, with up to 27t/ha from some vines.

'My whole aim with irrigation for the last 2-3 years has been to keep the water in the first 30cm of soil and the soil moisture devices have shown that I have been managing to do that,' Caddy explains, referring to his Sentek Enviroscan and Odyssey GreenLight-Red Light soil moisture system.

'I've also been aiming to keep fertilisers in the top 30cm as well. To measure this, I've been using soil water extractors. I have nine SoluSampler probes scattered throughout the property which I primarily put in to measure salinity in the rootzone. But, they can also track nutrient levels,' Caddy said. 'At one time I used to buy a truckload of 'feel-good' fertiliser and use it whether I needed it or not and then flush it all past the rootzone. I now make sure that whatever I apply stays there.'

With the benefit of being able to track the salinity in the rootzone, Caddy now only needs to carry out leaching irrigations if it is deemed necessary whereas previously they were performed at the end of the season, usually before the end of January, whether they were needed or not.

Since 2002-03, Caddy has reduced the amount of irrigation water he applies to his vineyard from just shy of 10ML/ha using overhead sprinklers to just 3ML/ha in 2006-07 under drip - a far cry from the days when the vineyard was flood irrigated.

Caddy bought his Barmera block back in 1965 which bore Sultanas, Currants and Gordos that had been grown mainly for dried fruit production. Set up for flood irrigation through the use of open channels, the vineyard had a water licence for 46ML per season and received six 'general irrigations' once a month, with 'special irrigations' performed in between times to 'top up' in accordance with standard practice at the time.

'General irrigations were carried out by growers whether vines needed it or not,' Caddy recalls. 'Fertilisers would be applied and then watered during a 'general irrigation'. Any fertilisers put on the ground would be watered past the rootzone and washed out into the drains! These drains would be running all the time!'

In 1973, Caddy began redeveloping his vineyard, replanting to Chardonnay and Cabernet Sauvignon and converting his irrigation system to overhead sprinklers.

'Back then, overhead sprinklers weren't that common and were considered the 'ants pants'. But although overhead sprinklers gave growers the ability to put on the right amount of water at the right time, they didn't; they tended to stick to their existing ways which included utilising open channels,' Caddy remembers.

Through his involvement with the now defunct SA River Murray Resources Committee during the 1980s and '90s, Caddy became increasingly familiar with best practices in water use efficiency. In 1990, a soil survey was carried out across his entire property to give a better understanding of the readily available water (RAW) value of his soil - a sandy loam clay over very heavy limestone. Two years later, he purchased an adjoining 4ac patch degraded land with the intention of extending his rows of Cabernet and spent in excess of $40,000 over two years rehabilitating it. Prior to planting out the block, Caddy applied 50 tonnes of gypsum and planted sorghum to build up the humus in the soil. Having purchased a second water licence to cater for the additional plantings - bringing his total allocation to 79.16ML - the vines are now strong and healthy and achieving good returns.

In 2003, an evaluation of Caddy's sprinkler system was completed which proved that the system had poor distribution uniformity, meaning he had to over-irrigate to ensure that all parts of the vineyard received the desired amount of water. Hence, he made the decision to install a drip system comprising 2.3L/hour drippers with an application rate of 1.05L per hour. Caddy says the system had an immediate impact on the vineyard with both the crops and their management improving.

Having at one time run his own petroleum business, Caddy was one of the first in the oil industry to use computers to help run his business. He now uses spread sheets extensively to run his vineyard, which today is split almost 50-50 between Chardonnay and Cabernet. 'Fruit growing is no longer a way of life - it's a business,' he says. 'It's becoming more of a science too.'

Caddy says that prior to the drought and during the time of significant growth in vine plantings in Australia, water-efficient growers were encouraged to grow enough grapes to completely utilise their water allocations.

'As growers became more efficient with their water use, they used less water and therefore had some leftover. They used this leftover water to establish additional plantings. That's why a number of them are now in trouble, given their allocations in recent years have been dramatically reduced.'

This season, Caddy decided to shy away from using synthetic fertilisers in his vineyard, preferring to use organic alternatives.

'The cost of fertilisers is going through the roof and it's only going to get worse,' Caddy remarks. 'In addition to that, if you put fertilisers on your soil you increase salinity - it's a known fact which shows up in salinity readings. I'm trying to avoid all that, particularly with improved irrigation practices.

'When salinity in Renmark rises, and it will, we will be dealing with 1000EC instead of 300EC. We are going to be in big trouble. Because land in the area has been cleared over the years to grow crops, rainfall is going straight through the soil. The pressure on the ground water is increasing forcing the ground water to come up which is going to flow straight into the River. My greatest fear is that salinity is going to be our next hurdle once we get out of the drought.'

Assuming allocations for the season remain on a par with the most recent 32% - water allocations for South Australia's River Murray irrigators stood at 15% on 15 October compared with 16% at the same time last year - Caddy believes he will again avoid the need to purchase temporary water, given a carryover of 4ML, and insists others could too.

'Growers have to get out of the 'that's how my father did it so that's how I do it' mentality. Be prepared to change your growing practices and take on new ideas,' he says. 'Be aware of your surroundings, monitor your vines all the time and monitor weather forecasts. I am constantly surveying the vines and assessing their general health. I'm also constantly watching the weather to see if any heatwaves are coming through and make sure I'm prepared for them. I saw the heatwave that we experienced earlier in the year coming and was due to water the night it hit. Instead, I watered the previous morning then topped them up again that night. Growers that didn't had severe stress.'

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