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A Norfolk farmer who irrigated maize to overcome last summer's drought says doing so was cost-effective – despite the expense. Dairy farmer reaps benefits after irrigating maize crop

• Eases pressure of summer drought

• Worst affected maize area irrigated

• Financial and environmental benefit

A Norfolk farmer who irrigated maize to overcome last summer’s drought says doing so was cost-effective – despite the expense.

Mark Larwood irrigated the worst drought-stressed areas of his 40ha maize crop at Oak House Farm, Larling. It helped ensure he produced sufficient forage for the farm’s 250 Holstein dairy cows throughout the winter.

“Irrigation has become much more expensive following substantial increases in water and electricity prices – but ultimately the additional cost was more than offset by the benefits in maize yield and silage quality.

“Without it, we would undoubtedly have seen production fall substantially or had to buy in expensive additional forages and concentrates, assuming that supplies were available.

“We have grown maize for 40 years as it suits our farm and what we want to do here. Maize is a high energy, high starch feed which reliably delivers high drymatter yields.

“It is very palatable and consistent in terms of feed value, so we have always fed a diet high in maize silage to optimise the performance of our high-input cows.”

Maize ration

Calving all year round, the farm’s Holstein herd averages 10,700 litres per cow per year at 4.3% butterfat and 3.3% protein. The goal under the farm’s contract with Arla is to maximise these constituents.

“We want to produce as much milk as possible from forage, so maize silage makes up 70% to 80% of the forage portion of the ration,” says Mr Larwood, who farms with  his father Brendan, uncle Peter and three full-time staff.

“Maize is much more resistant to drought than grass, which is important because most of our farm is on sandy loam soil which is prone to drought.

“The average rainfall here is 600mm, but in 2022 we had just 450mm and very little of that fell in the critical growing period from March until June.

“When selecting varieties, out and out yield is not the only consideration, rather the overall quality, with enough starch to provide sufficient energy and reasonably early harvesting to allow a following crop of winter wheat or grass to be established.

“In 2022, two-thirds of the crop went into the extra-early variety Cathy and one-third into the ultra-early ES Tommen.”

Variety choice

Cathy yields 104% of controls on the NIAB list and has delivered stable performance every year in trials, says Wilson Hendry, of forage specialists Grainseed.

“It’s a variety characterised by very even growth throughout the season and has excellent drought tolerance on light soils. MGA trials have also shown it delivers superb results under film.

“With a maturity rating of seven, it’s a variety providing early grain maturity with high levels of ME at 11.5Mj/kg DM and starch at 29.0% from mature grains with large plants giving the potential to produce huge drymatter yields at 30%DM.”

ES Tommen has excellent early vigour to speed establishment on heavier soils, but suited to a wide range of soil types, featuring large, erect cobs on big plants, plus excellent feed quality he adds.

“It’s a variety characterised by early starch lay down in the grain for early harvest and the plant remains green, extending the harvesting window for an ultra-early maize.”

“It makes excellent silage which is high in starch and has a high ME, typical DM starch and ME values being 33.5% and 11.6 MJ/kg.”

Maximising performance

Despite the challenging conditions, both varieties looked very good through until June, but after three months with very little rain the decision to irrigate was taken, says Mr Larwood.

“Had we not started to irrigate then the plants would have started to shed leaves and the opportunity to do so would have been lost as the crop would not have been able to take up the water.

“Starting in early July, the maize received four irrigation passes over six weeks, 30mm being applied through a rain gun on each occasion. We irrigated about one-third of the total maize area which was most affected by drought conditions.

“The infrastructure was already available from when we grew potatoes, so the actual cost was about £45 per acre inch.

“In total, we invested about £180 per acre, but the payback made that very worthwhile.”

“Relative to the unirrigated area, where water was applied the fresh weight yield of maize almost doubled, from 17-18t/ha at 39%-40% DM to 40t/ha at 33% DM, the latter figure being about average in a normal season.

“With maize from irrigated and non-irrigated fields mixed together in the clamp the overall quality was not far off what we would normally hope for, a remarkable result given the challenging conditions.”