According to SoilScapes the soil around the Burnley area is:
Slowly permeable seasonally wet acid loamy and clayey soils, Loamy and clayey and low fertility
To improve the soil fertility:
Add organic matter.
This helps improve drainage and lighten heavy soil. It also provides nutrients for beneficial soil microorganisms which will, in turn, also help improve the soil. Before planting in spring, add compost and aged manure. A 2- to 3-inch layer worked into the soil to shovel depth is a good amount. Throughout the growing season, mulch with organic materials like grass clippings, shredded leaves, or additional compost. Since soil microorganisms literally “eat” organic matter, make a habit of continually adding it to your soil.
Build raised beds.
Because clay soils hold water, creating raised beds can help improve drainage by encouraging water to run off. Raised beds can be a simple mound of soil, or can be constructed out of wood, brick, or stone. To lessen compaction, size the beds so you can reach the middle without stepping in the bed.
Mulch beds over the winter. Driving rain can really pack down bare soil, so keep beds mulched with organic matter both during the growing season and over the winter. A layer of straw over the beds will protect the soil from compaction and reduce erosion; it can also help minimize weed growth. In the spring, transfer the mulch to the garden paths.
Improving soil takes time, so don’t expect overnight results. On the other hand, if you follow the above steps you should notice some improvement each year. Within a few years, you’ll have rich, plant-friendly soil.
Add compost any time. However, if you are tilling in fresh or uncomposted organic matter, such as a cover crop, leaves, or straw, wait at least a few weeks before planting to allow the material to break down.
Vegetables that grow best in Burnley’s soilscape:
Lettuce, chard, snap beans and other crops with shallow roots benefit from clay soil’s ability to retain moisture, and broccoli, Brussels sprouts and cabbage often grow better in clay soil than looser loams because their roots enjoy firm anchorage.