Composting at Mottisfont

A gardener 'turning' the compost at Mottisfont, Hampshire

Making and using compost is integral to keeping Mottisfont’s gardens in top condition. Here, head gardener Jonny Norton explains the why’s and how’s behind good compost, and the important role of the industrial cake thermometer.

The main reason for making compost is the need to feed the soil and its micro-organisms, worms and insects – they love organic matter. Our soil is itself a living organism, and needs feeding. The method we use to feed our soil is by adding a regular applications of composted mulch - just as nature intended.

Nature’s best example of this can be seen on the forest floor, where fallen green (live) and brown (dead) matter collect on the surface of the ground and gradually decompose into the soil below.

The key benefits from applying compost are:

  • A well fed, healthy soil
  • A thriving habitat of micro-organisms, worms and insects
  • Healthy plants with a greater natural resistance to combat pests and fungal diseases
  • No need to spray or add chemicals/artificial fertilisers 
  • Effective organic weed control
  • Effective method of water retention, reducing the need to water plants by hand
  • It’s free to make and means you can recycle waste.  

What is compost made of?

Compost can be made from any decomposed organic material, such as straw, leaves, food, straw, and waste grass cuttings. The makeup of compost can vary considerably depending on its ingredients: usually the makeup of our compost is based on seasonal garden waste.

Garden waste, ready for composting
A pile of garden waster ready for composting at Mottisfont, Hampshire

In the spring and summer months you will usually end up with a high nitrogen content, as more green material tends to be available. In autumn and winter months, our compost has more brown material, which provides a more woody-based compost, great for adding structure to the soil.

How do we make compost at Mottisfont?

As we require very large volumes, we have adopted a rapid system known as ‘hot composting’, which means we can produce usable compost within 4 - 8 weeks. This way we never let our garden waste build up, and we spread out the workload throughout the year.

We are able to do this thanks to a clever machine which grinds and minces our mixed green and brown waste (we generally aim to mix 60% of brown and 40% of green material). A full load in our mixer can make approximately two tonnes of compost - we aim to produce 80 tonnes in a year.

Our compost piles
Piles of compost at Mottisfont, Hampshire

This is then piled to at least 1.2-1.5 meters or shoulder height, which ensures the heat can build up to the desired central temperature of 50 – 70 degrees Celsius. This temperature is ideal for decomposing the mixed waste and killing off any weeds, roots and seed.

We use an industrial cake thermometer to measure the heat in the centre of our pile. As the temperature starts to drop below 50 Celsius, it’s time to turn the compost pile and mix it all again – with our rapid method, this is a weekly task. We turn a small batch by hand, but use a small tractor for large quantities. 

Our busiest time for making compost is during the autumn, when we harvest almost all of the fallen leaves from our many hundreds of trees on the estate. We use this leaf harvest to make amazing fine leaf compost, which makes our soil and plants really thrive. We even use it as peat free potting compost.

A pile of seasonal produce dug up from a vegetable patch

Our guide to making your own compost 

Our gardeners have written some top tips for making your own compost at home. Follow this cost effective, step-by-step guide to help your garden - it will help reduce waste, too.