The soil in a typical backyard vegie patch works pretty hard. Season after season, we depend on it to grow a continuous supply of produce. As soon as one crop finishes, in goes another. So should we give our soil a rest from time to time?
Conventional thinking would lead you to say yes. You know yourself that after a long period of working flat out, it’s wise to take a break to recharge your batteries. But it’s not quite the same for soil. The very health and fertility of soil depends on having plants growing in it at all times. It’s all about the soil micro-organisms and their interconnection with plant roots.
We know that certain soil bacteria and fungi boost plant growth by repelling pathogens and increasing the availability of nutrients. In return, plant roots release sugars and other exudates that support these beneficial microbes and allow them to proliferate. It’s one of those perfect examples of symbiosis in nature. The idea of removing all the plants, covering the soil with mulch, and ‘putting it to sleep’ is pointless, and could even set it back.
So, what about the constant removal of soil nutrients in the form of harvesting? Wouldn’t resting the soil stop it being further depleted? That’s where compost and crop rotation come in. If you add compost to the soil on a regular basis, at least once a year, or in small amounts every time you plant, you’re helping to replace the nutrients that were removed, while supporting your soil’s microbial community.
Replacing a harvest with an unrelated crop with different nutritional needs (crop rotation) helps to reduce the nutritional load on the soil. A typical crop rotation system includes a ‘rest’ bed, where a green manure crop, such as oats or fava beans, is grown, not for harvest but to be slashed (before flowering) and left in place to break down and provide more organic goodness for the soil. If you’re not planning on planting a crop for harvest, sowing a green manure crop is your best option.