It’s hard work, but somebody has to do it. This is Thompson’s Farm at Batchelor in Australia’s Northern Territory. The last time I was WWOOFing, I was picking buds off vines. This time, I’ve been picking watermelons off vines. They’re slightly heavier. 12kg heavier in fact.

The trick is to look for one that’s already caught the sun. There should be signs of a yellow patch on the skin. You then give it a tap. If it makes a noise like a ‘ping’ or a ‘bounce’, it’s good to go. If it’s dense, it’s overripe. If it’s hollow, you have to turn it around for a closer look because something else has obviously got there first. Watermelons are a delicious feast for white ants, cockatoos and wild pigs. I’ve had to chase off wallabies who love the shoots.

You can understand why these ‘sugar babies’, (as they’re affectionally known) are so popular. There’s nothing better than sitting on the back of a truck after a hard morning’s work and eating a slice of sweet, juicy melon warmed by the sun. We’ve called it ‘testing’ although that doesn’t really make sense, because the rest of it can’t be used. Do you see the cunning nature of our work?

We’ve also been picking bananas. They’re covered in plastic to keep the moisture in and the moths, rats and spiders out. The first step is to feel for a full fruit. Then, if you open it up and it looks like some of the bananas are turning yellow, it’s time to cut off the bunch.

You leave a few inches on the stem so that there’s enough room to hang them and get the bananas fully ripe.

Once the fruit is picked, it’s time to cut down the entire tree. This is because one tree can only produce one bunch. It’s surprisingly easy – the trunk is fibrous and mushy. You just have to get out of the way when it falls.

Laying down irrigation lines is dirty, dusty work on a hot and windy day – and it has been hot, with an average of 34c. I love the rich red colour of the soil but up until three years ago, some of this couldn’t be used. Years of chemicals had taken their toll. That’s why the Thompsons started using organic farming methods instead. They now use soil enhancers like gypsum, agralime and chicken manure. The main pesticide is neem oil. They also use potassium silicate, which feels like small shards of glass. The results are good. The watermelons can now grow up to 12 or 15 kilos. Five years ago, they only reached 8. The yield from courgettes has tripled.

They’re a favourite with the cows here. Any bad fruit or vegetables that we’ve picked has gone straight to them. They’re the happiest beasts you’ll ever meet.

The farm shop has been another satisfying part of the volunteering – proudly displaying the produce you’ve carefully planted, picked or packed. Customers talk about how much better they taste than the fruit and vegetables they buy in the supermarket.

The farm manager and his wife are expecting their first baby in November. He wants the soil to last long enough for his own children to grow vegetables here. That’s why the organic way works for them.