Friday, March 29, 2024

A summer oasis

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Liz and Don Polson with ewes ready for shearing. Don and Liz Polson have struck green on their Mangamahu Valley farm near Wanganui after spending $5000/ha on irrigation. Russell Priest reports. Photos by Graeme Brown. A desire to improve lamb growth rates and drought-proof their finishing prompted the Polsons to install an irrigation system along with high-performance forages on their 130ha alluvial river flats. “I’ve had enough of droughts,” Don says. “We’ve gone from a desert to an oasis under irrigation. We’ve never had so much summer feed.” The Polsons’ main farm, Waipuna, is a 1600ha mainly medium to steep hill-country block lying between Mangamahu Valley and State Highway 4 (the Parapara Rd) north-east of Wanganui. The farm includes 350ha of river flats and terraces bounded by the Mangawhero River. The area is prone to dry summers.
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“In the past we’ve finished most of our lambs by various means. However, we’ve generally ended-up having to carry a lot of light lambs into the winter to finish,” Don says.

“My philosophy used to be that if we could get our lambs through the summer they would be very valuable.”

In recent years the Polsons have even fed grain or pellets to help carry their lambs through.

“We quite enjoyed feeding grain-pellets as it was nice to feel appreciated. The lambs would be waiting for you at the gate each day!”

Nowadays the focus is on getting lambs to slaughter weights as early as possible. To help them do this the Polsons have invested $5000/ha to irrigate some of the river flats.

The option of buying more finishing land was also investigated but irrigation got the nod.

Don concedes that not everyone close to a major water source is able to irrigate because of the difficulty in getting water consents and in lifting it out of the river. 

The irrigation project employs three guns, each covering an area of a little over 40ha and capable of delivering 30mm every 10 days. The required operating pressure is 120psi.

“Because of the high pressures required, guns are less efficient than centre pivots in delivering water. We couldn’t use centre-pivot technology because of the uneven contour.”

To achieve the required result two pumps are used in tandem. The first pump (30kW) lifts the water 30m out of the Mangawhero River and delivers it to the second pump (90kW) that provides the necessary volume and pressure to drive the guns. The Polsons have a consent to use 5300-cubic metres of water a day.

Getting all bases covered

Don Polson surveys the flood damage on his irrigated flats.

The Polson family name was established in the Wanganui area in 1873 when Don Polson’s great grandfather Donald Gunn Polson bought Manurewa, a 460ha farm at the southern end of what is now known as Waipuna.

Further land was subsequently bought by Donald until Don’s grandfather, Sir William John Polson, took over the farm. It underwent a period of consolidation under his ownership because of his divided interest in politics.

Sir William was an independent Member of Parliament for Stratford and leader of the Upper House before it was disbanded. He was also a foundation member of the NZ Farmers’ Union (now Federated Farmers) and its president for 18 years.

“The organisation had a lot of political clout in those days. It almost ran the country,” Don says.

Don’s father and uncle subsequently managed the property and when they returned from World War II the farm was divided three ways, the third-share going to their sister Dorothy.

When Don and his late brother Alistair – a past national president of Federated Farmers and a special agricultural trade envoy for NZ – were handed the reins of their father’s share of the farm they set about amalgamating, with the help of their cousin Sam, the farms previously owned by Sir William.

Sam’s father, John Polson, was also politically inclined, serving on the NZ Meat Board. In 2005 Don and Alistair decided to follow the family tradition and divide the business so the farm was once again split.

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