It’s well established that biodiversity plays an important role in the health and resilience of living systems. The combination of organisms (or organisers as I like to think of them) and the different roles they play makes for a productive, dynamic program. Having a diversity of plants supports a diversity of microbe and animal life above and below ground that in turn carry out services of benefit to the plants.
Crop rotation and companion planting are the gardeners’ interpretation of the fancy ecological terms – temporal diversity and spatial diversity. In nature, spatial diversity, i.e. a good mix of plant species all growing together, is the most predominant mode. That said there are also natural successions of plant communities over time, such as in the occurrence of pioneer species that colonise degraded or marginal landscapes and make the way for higher plants to follow. Both of these strategies can be utilised in a growing program.
Companion planting is all about combining crops that grow well together or inter-planting crops with complimentary species. It is important to consider the different growth habits of companions in the sequencing and/or spacing of plantings.
Based on your objectives you may use species that:
- are understood to grow well next to each other
- support specific microbe populations that acquire nutrients from the environment, improve soil structure and manufacture beneficial plant compounds
- attract animals, birds and insects to help with pollination, pest control and fertility
- ward off or confuse pests
- handle various environmental conditions well and support or protect their neighbours in tough times
It’s worth noting when choosing to grow a bunch of plants together that they have the potential to benefit or compete with each other.
Most annual species deliver significant amounts of carbon rich exudes to the biology around their roots, contributing to soil fertility, for much of the growing cycle. This is the case from the vegetative growth stages right through to flowering and early fruit set.
When the process of fruiting begins, fruit fill becomes the number one priority and plants then direct most of their supply that way instead of towards the roots. This is an expensive time and you often see old leaves start to lose colour and disease set in.
At this stage plants will take what they need from the soil reserves so it’s a good time to terminate non-crop plantings if you don’t want to hinder nearby and subsequent crops.
When planning your rotations you want to ensure the timing of the growing seasons between crops match up and that the successions work well culturally for each type of crop.
Objectives behind rotating crops include:
- repelling crop specific pests and diseases or breaking their breeding cycles with crop sequences they find unfavourable.
- interrupting weed reproduction cycles with a range of crops that have different growing seasons
- improving the growing conditions for subsequent crops by preceding them with a mix of plants that contribute to the structure and fertility of the soil
- loosening up the soil and recovering leached nutrients with deep/tap rooted species