Before planting out each year in the veg plot, the first decision is what to grow, and what is going to be planted in which bit of the plot, and how to rotate Crops year on year.
Crop rotation is important; it quickly becomes obvious, when growing vegetables, disease and pests are the enemy. Crop rotation seeks to prevent build up in the soil of diseases and pests particular to that type of vegetable, by not growing the same vegetable in the same soil each year. In addition, some vegetables, the pea and bean family, fix nitrogen in the soil and so the next crop should be one that thrives with the extra nitrogen. There are good reasons to organise crop rotation which does it's bit to help keep disease at bay.