The summer evenings are so light and warm that the chickens stay out long past their bedtime. It’s nearly nine o’clock before they finally mosey into their palais des poulets, an abandoned fruit cage where sheds covered in old car number plates and graffiti by William Blake provide shelter from farmyard terrorists: hedgehogs, foxes and stoats.

The ritual of shutting up chickens makes me feel like a genuine countrywoman. That isn’t entirely true. I hate to shoot birds, I am vague on the gestation periods of sheep and cows (eggs hatch out in 28 days, but 28 days from when they are laid or from when the broody broods?), I don’t understand why during a long drought the water sucked up by evaporation doesn’t return in a cascade of rain, and I owe my knowledge of birdsong to Radio 4. Still, I love the peace of these evenings, the Bach like chatter of the guineafowl in their sleeping porches in the apple trees. And every evening this week, following the path of the full moon, I walk over to a field called Cages. I scramble up the small ledge and gaze out onto a field that is being transformed in front of my eyes: dramatic, vast, an earthly miracle.

Ten days ago, Cages was a 10-acre field of oilseed rape which, if we were lucky, would fetch £2,000 when harvested (before seed and labour costs). At the beginning of the week, with the rape crop sacrificed, the topsoil removed and the earth scraped and flattened, the field looked like a magnificent dance floor. It also looked spookily like Prescottville: just pour concrete, build 72 houses and install yellow sodium street lights. With planning permission, this field might be worth more than £20 million. As farmland, it’s in a category our bank manager describes as expecting ‘a level of income insufficient to break even’. In eight weeks’ time, it will be a reservoir covering some six acres and holding 20 million gallons of water.

It will also be a debt that will take us 10 years to pay off. Instead of farming concrete the most profitable crop in the country-side, we have just borrowed £8,000 from the bank, the amount we need to match a generous Defra grant (thank you, blessed among taxpayers). The reservoir will enable us to irrigate 150 acres of vegetables. We hope the income from these vegetables will be worth the investment (plus borrowing costs and the nerve-wracking handover of deeds to the bank for ‘safekeeping’ until the loan is paid).

Under the full moon, I stand in the centre of the amphitheatre and sing at the top of my lungs a song from Carole King’s Tapestry: ‘I feel the earth move under my feet, I feel the sky tumbling down…’ The year 1971 must have been a slow one for me because I know this whole album by heart. The vast cavern of Cages provides its own amplifier and I move about as nimbly as any ageing rock star, happy to release the nervous energy that accompanies borrowing money and investing in farming.

‘If water is the new oil, you’ve made the right decision,’ the farm accountant tells us. This sounds flaky and dubious to me. Reservoirs, like oil fields, can dry up. If we continue turning this corner of East Anglia into a concrete landscape, Cages field will look like a cameo of the Grand Canyon. A reservoir stores water: it doesn’t create water. We could find ourselves paying back the loan on a deep hole. But this is no time for gloom. Under the lunar spotlight, I sing to my audience of great crested newts: I feel the earth move under my feet

I feel my heart start to trembling…

This article first appeared in Country Life magazine on July 20, 2006.