Wednesday, September 26, 2018

Effective irrigation vital for high-value crops

September 3, 2018 by  
Filed under Crops

Securing adequate supplies of water has become increasingly important for David Hoyles, who manages three fenland farms.

Fenland farmer David Hoyles is renowned as a grower of high yielding crops – especially wheat for which he is a past record holder.

But to maximise margins across the range of crops grown on the 700ha family enterprise, he has become increasingly concerned with quality, timely production and efficiency. And that means securing enough water for the business.

Apart from wheat, his seven-year rotation on three farms between Wisbech and the Wash includes sugarbeet, vining peas, and mustard. Since 2015, however, his attention has focused on 110ha of potatoes and 35 ha of beetroot – both grown for the quality end of the market.

The Grade 1, Wisbech series silt is a fine, powdery soil. Relatively free of stones, it holds moisture well. Even so, to avoid scab on potatoes the ridge must be moist as the tubers form. Ideally, this means they need to be well watered two to three weeks after emergence.

Premium quality

Irrigation is required if there is insufficient rainfall. Until recently, none of the farms under Mr Hoyles’ management had irrigation which meant they were at the mercy of the weather. In poor years, this could result in failure to achieve a quality premium for the contracted volume.

That all changed in autumn 2015 when Mr Hoyles built the first reservoir and installed an irrigation system on one farm under the LEADER grant scheme – awarded through South Lincolnshire’s ‘Wash Fens’ programme.

The grant was paid via the Rural Payments Agency. It covered 40% of the equipment – although not the 18 million gallon reservoir. In the first season, this was more than enough for the farm’s irrigation requirements.

“In 2016, we used very little water – primarily for beetroot emergence and to aid the potato harvest,” explains Mr Hoyles. “In 2017, we used much more, partly because even though the rainfall figure for May was average, it came in 24 hours with long dry periods in between.”

The success of the first system – which is based on two Briggs Irrigation hosereels and 64m booms irrigating to 72m – has led to a second installation on land fronting the River Nene in Cambridgeshire.

In this case, the Cambridgshire Local Action Group (LAG) scheme has included grant aid for the (lagoon) underground mains. The systems were designed by Adrian Colwill of Briggs Irrigation for maximum efficiency and ease of use.

On the second site, a small 5 million-gallon, lined reservoir has been created next to the river. While this is insufficient for a whole season, it can be topped up when water is available and the quality is suitable. As the farm is two metres below sea level, however, salinity is an issue.

The abstraction pump is fitted with a conductivity meter to monitor salt content and stop water flow if necessary. On both systems a 200mm main has been installed by Philip Millington Water Services to ensure there is adequate water pressure throughout farm.

The fields are served by 160mm spurs and hydrants have been installed every 72m – the wetted width of the Briggs R64/2 boom – to avoid long feed pipes to the VR7 hosereel, fitted with 600m of 110mm diameter hose.

Cnstant pressure

With very little pressure loss throughout the system a 55kW (75 hp) rated electric pump can easily maintain the 7-8 bar pressure requirement throughout the network. A 5.5kW submersible pump in the lagoon maintains positive pressure to the main pump house.

Total power requirement is therefore kept to a minimum at around 18-19kW with one machine working and 36kW with two machines – an efficiency objective that fits well with the requirements of the grant scheme.

The pump house, specified and constructed off-site by Powerflow Systems of Usk, includes a control system inside a secure, shipping style container. The variable speed control system ensures there are no ‘spikes’ in power consumption on start up.

It also reduces the effect of water hammer at the beginning and end of the irrigation cycle.  A digital water meter allows easy detection of leaks and automatic shut down in the event of low or high flow scenarios – simplifying management.

Attention to detail is equally evident in the application of water. The booms provide far greater accuracy than a raingun – especially helpful under the windy condition that are common in this part of the fens.

Mr Hoyles also wants to ensure the ridge is wetted rather than allowing water to run down the sides into the trough. This can be achieved by reducing the instantaneous application rate by using nozzles with a large diameter and an even spread throughout the radius.

Smaller nozzles

Brown deflector plates work at a 14-15m diameter and deflect the water evenly due to multi trajectory streams. Reduced nozzle sizes during the early part of the year until ‘canopy cover’ are being used to lower the instantaneous application rate.

Each 15mm application can therefore be applied uniformly and gently with an increased wetted area. Under ‘normal’, dry conditions water will be applied 10 days after 50% leaf emergence and then throughout the growing season as required.

This season, the exceptionally dry spell meant continuous irrigation was needed for nine weeks, until the reservoir ran out in mid July. By this time, the drain that supplies it was too low for further extraction.

Mr Hoyles says the investment has helped him achieved his objectives of security of water supply under normal conditions – plus the ability to manage water for maximum quality. It is a strategy that is already starting to pay off, he adds.

“We have already seen the financial benefits for the beetroot in particular where irrigation helped us bring a good quality crop to the market ahead of the competition.

“On potatoes, I anticipate this year our yields will still be down by 20% where we have irrigated because the temperature was too high for growth. However, our unirrigated yields are likely to be down by 30-40% at the very least; irrigation certainly helped to set the crop up.

“Looking ahead, if we are to maintain our relationship with the high quality retailers I believe we need to be able to ensure we meet our obligations for quality and volume and that will require effective irrigation.”

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