So what is really the problem with mono-cropping (single species plantation)? This question is more easily answered by understanding how intercropping is beneficial. But a short and logical answer is that mono-cropping creates a weak system where one pest, one drought, one unfavourable climatic condition, can wipe out an entire crop resulting in complete loss for the farmer.
Once more the forest has a lot to teach us on this topic. The forest is one of the highest biomass producing eco-systems and more precisely tropical and evergreen forests have the highest production amongst types of forests. What we typically see in such forests is that it has the highest biodiversity. Very rarely will you find only one species growing in even a tiny area. Biodiversity is the strength of ecosystems. Won't we have better luck if we learn to imitate the forest system of production?
Let us look at some benefits of intercropping in organic farming and gardening.
If your garden bed has more than three types of plants growing on it, and no same plants are touching each other, it reduces the impact of pests dramatically. There is a very simple explanation for this. Pests usually move from one plant to the other and usually pests like one or two kinds of plants. When there is one straight line of the pests' favourite vegetable it will keep going from one to the other and keep multiplying. If the pest eats one plant and then next it encounters a plant that it doesn't like, then it will think there are no more of its favourite plants and so it may disappear or simply remain in small numbers.
Nutrient Control and Optimization
Every plant has different nutrient requirements. If you have a monocropping of only vegetables such as cauliflower or sweet corn which are high nutrient consuming plants, then your soil will become depleted very quickly and will require you to keep adding hight amounts of nutrients externally. This is both harmful to nature as well as inefficient. Intercropping high nutrient consuming vegetables with low nutrient extracting and nitrogen fixing plants will give you a diverse and higher yield. This chart below will give you some idea of what are high and low nutrient consuming vegetables.
1. Fruiting Vegetables (e.g Tomato, Brinjal, Cauliflower, Cabbage etc.) High
2. Leafy Vegetables (e.g. Spinach, Latmat, Methi, Corriander etc.) Medium
3. Roots (e.g Carrot, Raddish, Sweet Potato etc.) Low
4. Legumes (e.g Tur dal, Chawli, French Beans, Soya bean etc.) Nitrogen Fixing
Nutrient management automatically leads to less requirements of water, fertilizer, and mulching since plants can form their own mini-ecosystem with less needed from the outside.
So how can you do it?
As I always say don't be afraid to try something out. Trial and error is your best friend because only your context will tell you what can be best intercropped and how. There are several established examples of intercropping and companion planting.
Tomato and Marigold Companion Planting: This is a very common example. Companion planting is where the two plants are meant to be with each other because of how beneficial they are to each other and to us. Tomato pests are mostly nematodes which means they come from the soil. Marigold roots have a property that kills these soil nematodes. So they do very well together and at the end of the day you have beautiful tomatoes and marigold flowers to harvest.
More information on companion planting and intercropping can be found here.