Soil Fertility

The Basics

In this episode of GROW COOK EAT Michael and Karen discuss the importance of soil fertility for the health of the food we grow, and, ultimately, our own health. 

There are loads of factors affecting soil fertility like the amount of organic matter, the minerals in the soil, micro-organisms, soil structure, drainage, soil PH…and about 15 more.
The main ways to maintain or improve soil fertility are

  • keep your soil covered
  • replace nutrients lost through growing
  • protect the micro-organisms in the soil (don’t kill off the helpful bugs)
  • rotate what you grow

Soil Cover

Covering soil can help suppress weeds, keep the rain from leeching out nutrients and reduces erosion. In winter at both GROW HQ and in GIY’s other site in Carriganore, Waterford, we use a crop called a ‘green manure’ to cover the soil. It acts as both soil cover and fertiliser, sown in late autumn or early winter and dug back into the soil in early spring. Green manure like clover or buckwheat, helps improve soil drainage as the roots break up claggy soil, lets air in and yet holds the soil together to prevent erosion.

Soil Feeding

Replacing lost nutrients in the soil is essential. You might have no problem growing in your soil for the first few years but then ‘inexplicably’ struggle thereafter. Plants take nutrients from the soil to grow and we need to replace those. As Michael explained in the show, there are several ways to replace those nutrients and the good news is they’re mostly cost free.

  1. Well-rotted manure. You know it’s well-rotted when it’s at least 6 months to a year old, is a uniform dark brown, has no smell and no distinguishable particles, like grass, in it. Manure is a great natural fertiliser that adds nitrogen, phosphorus, potassium and more. It warms the soil and creates a beneficial environment for micro-organisms, and for decomposition.
  1. Fresh Seaweed. Unlike manure, seaweed doesn’t need to compost before being used as a fertiliser. It’s full or trace nutrients and minerals and these exist in a state that is readily available to soil and plants even before it decomposes.
  1. Compost. Decomposed organic matter is a complete feed for plants and soil. If you watched last week’s episode on compost you’ll have heard Karen refer to it as ‘Brown Gold’ and it really is. It completes the life cycle of all organic material, it benefits the environment in so many different ways and it’s really simple and easy to make. Learn how to make your own compost.

There are, of course, many other fertilisers that you can buy: liquid feeds, chicken manure pellets, powdered seaweed but it’s a good idea to view these as supplementary feeds rather than being used to increase the overall fertility of your soil.

Protect the Micro-Organisms

Our GROW HQ Head Grower, Richard Mee, is all about allowing the mini-ecosystem of the soil or garden to find it’s balance. The more diversity in the soil the better it maintains its health. Only a small amount of the bacteria and fungi etc in soil are harmful to plants and allowing all microbial life to thrive means the natural enemies of the harmful organisms keep them under control. Using fungicides, pesticides and weed killers can not only affect your own health, but they disrupt the natural balance of soil species, allowing some species to thrive and killing off others. Often, you end up trying to counteract the unwanted effects of the last chemical with another and never quite getting the balance right.