Running a livestock farm in the hills of North East Fife and writing dark crime fiction set in Edinburgh’s haunted closes might seem like an unlikely mix, but somehow I’ve managed to combine the two for over a decade now.

This month sees the publication of For Our Sins, the 13th book in the Inspector McLean series, and by happy coincidence this year will be the 13th crop of calves born to my fold of pedigree Highland cattle.

You might think that the life of a livestock farmer – tied to the land and the turn of the seasons – would be very much different to that of a writer. In truth, they have a great deal in common. Both involve long, solitary hours, toiling away for a reward that may be months or years in coming. Both require a certain stubbornness of character to persist in the face of adversity. And both have almost magical moments when it all seems to be worth it.

Farmer and author James Oswald crafts his latest novel watched by his sheep PIC: David Cruickshanks

Like writing, farming attracts a number of misconceptions in the public mind, not the least of which is that we are rich. It’s true that farmers may be asset rich if they own their land and aren’t in hock to the bank, but livestock farm incomes are among the lowest in the country, with brutally long hours and not much in the way of holidays. Cows don’t care if it’s Christmas; they still want to be fed.

Writing, similarly, is seen as a wealthy profession, and it’s true there are some – myself included – who have earned large sums from their words. And yet, the median income for a professional author in the UK, according to the most recent Society of Authors survey, is less than £11,000. That figure has also been falling in absolute terms for years.

I’m very fortunate to have bucked that trend in writing, although I’m not in the same league as JK Rowling, Richard Osman or Stephen King. Over the past ten years, Tony McLean, Constance Fairchild and my little dragon Sir Benfro have earned me far more than the cows and sheep ever could, but I’m not sure it’s a farm diversification plan that would work for all.

When my father ran the farm, it was a traditional mixed arable and livestock unit, with a herd of about a hundred cattle, a flock of 300 ewes and growing around 150 acres of malting barley. If that was the farm that I had inherited, there would be no time for writing and no Inspector McLean, but dividing the estate between my sister, two brothers and me meant most of the arable land had to be sold. The grazing and rough hill land I was left with initially ran a flock of pure bred New Zealand Romney sheep and a small fold of pedigree Highland cattle. Hard work, but just about enough to make a living. And working in one of the most beautiful parts of the country makes up for a lot of the hardship.

Then, in 2012, everything changed. The first two Inspector McLean books, self-published at the start of that year, sold over 300,000 ebook copies in less than six months. I’d written both of them many years earlier, while working as an agricultural consultant on a research farm in Wales and remembering my time living in and around Edinburgh in the 1990s. The farm took up so much of my time that I’d not written anything since taking it on, but the creative itch was still there. Still, I never imagined that the books would succeed the way they did. Both had been shortlisted for the CWA Debut Dagger in the mid-oughts, but failed to find a publisher at the time.

All that changed very quickly. Publishers came calling, both UK and overseas in translation. Natural Causes, the first in the series, was a Richard and Judy Book Club Summer pick and I was shortlisted for the National Book Awards debut author prize too. I was even invited over to the US to appear on The Late Late Show with Craig Ferguson, which was a surreal experience for a Scottish farmer. The pressure was on to write more Inspector McLean stories, but there was the small matter of running a livestock farm to fit in around all the marketing and publicity.

It hasn’t been easy. Instead of building up the Highland fold to around 50 breeding cows, I now have 16. The target had been a flock of 300 ewes, but it peaked at fewer than a hundred. I sold them all to my neighbour a few years ago, as they needed just too much work for me to cope. With lambing starting in April, and calving not usually ending until mid-June, I was missing a lot of the annual calendar of literary festivals. One big difference between writing and farming is that you can write pretty much anywhere; farming ties you to the land.

Over a decade, I’ve somehow managed to muddle through all the same, and somehow produce 20 published novels.

The 21st, For Our Sins opens with the discovery of a dead body in a disused church in the north of Edinburgh, scheduled for demolition. Inspector McLean handed in his resignation at the end of the previous book, All That Lives, tired of the politics of policing and exhausted by the long hours (a little like the author), but this dead man was an ex-con McLean put away many years earlier, and a local crime boss is leaning on him to investigate the death as suspicious.

Will he go back to the job he loved, but which ground him down until he could take it no more? You’ll have to read the book to find out.

It was written, like all of my books now, mostly in the autumn months. Then, the cattle are out on the hill, the spring calves still with their mothers but old enough to be hardy. There is not much essential farm work to be done, so I can concentrate on the words.

I don’t have time to take the Highland cattle to shows, but I do like to handle them as much as possible.

Most of them are quite tame – I’ve raised them all from birth, after all. They like to be combed, and often a less than orderly queue forms if I’m out checking they’re all OK and get the comb out to tend to someone’s fringe. It can be very therapeutic, and a great way to clear my mind when whichever story I’m currently writing doesn’t want to work.

That is the unexpected benefit of combining two such seemingly different professions. When the words aren’t coming or a plot is being particularly hard to wrestle into submission, I can pull on my wellies and walk up to check on the cows, jump in the tractor and spend a couple of hours topping weeds, load up the trailer with posts to fix a few fences, or take a chainsaw to some of the gorse that threatens to overwhelm parts of the farm. Almost always when I sit down to write again afterwards, the problem has magically resolved itself.

For Our Sins by James Oswald is published by Headline, £20, out 15 February

James Oswald on his double life as a farmer and crime writer