For 20 years I’ve kept what I consider to be simple, but effective crop records for our business. The detail of each block, or in the case of potatoes each field, is on a home-designed spreadsheet filling just one A4 page.

Basic information on area, cropping history and soil fertility are at the top. Seed rates, fertiliser applications and spray details are recorded on the day of use in pounds per hectare, and the separate totals are highlighted.

When it comes to costing field operations I use Farmers Weekly’s updated contractors’ rates. The reasoning is that although we use contractors only for harvest, we should be able to do the rest of our work at the suggested rates and still cover our overheads.

Contractors’ rates, like variable input costs, change each year. But by using them in our recording system I can compare costs over several years with a constant baseline.

The same thinking applies to outputs. All combinable crops are valued at the ex-farm price at the end of September each year. Potato income is recorded on the sale value of each hectare in any given field, and haylage is valued at a price below which I will not sell.

The results have been consistent and the net margin league table from the top is: 1. Potatoes. 2. Land let for potatoes/veg. 3. First-year wheat (the only wheat we grow). 4. Haylage. 5. Spring barley. 6. Winter barley. 7. Forage maize.

The conclusion is that on our land with our climate, a sound manageable rotation continues to sustain our business so no big changes are contemplated.

Mistake of the month: Said yes to a visit in May 2009 from David Richardson and his party of FW readers. I like brushing the yard, but hate painting.