The risk of repeated cultivation and what we can do to avoid the damage

It’s fun to grow various vegetables in the garden. However, we need to plan carefully, remembering what we planted last season because if you grow the same crop in the same place as the previous season it may not do well. 

What could happen if we grow the same crops in the same place?

It’s better not to plant the same crops in the same place. There are three reasons.

Nutrition Unbalance

One thing is the balance of nutrition in the soil. Each crop has a preference for nutrition. After growing a certain crop, the soil is unbalanced in terms of nutrients. If you plant the same crop to grow there in succession, you will start growing it with the soil lacking the nutrients it needs and it will perform poorly.

Disease and Pests

I think the nutrition imbalance is not a major issue. You can add new soil or fertiliser to avoid it. What is more serious is the risk of disease and pests. Different crops are more susceptible to different diseases and pests. If the same crop is grown in the same place for consecutive years the risk of damage from diseases and pests increases.

Avoiding growing the same crops in the same place is not enough. We need to consider the group of vegetables in large categories. For example, if you grow tomatoes in the part of your garden where you grew aubergines in the previous year, you will increase the risk of monocropping problems because they are all in the same Solanaceae family.

Furthermore, it is not enough to avoid growing the same crop for two years in a row. Some crops are more susceptible than others, some can be grown for just one year, while others should be avoided for three or four years.

So what can we do to avoid this problem? The following are what we can do easily;

  1. Rotating cultivation (grow different types of vegetables in the same place)
  2. Soil preparation
  3. Companion plants

1. Rotating cultivation

We can try to avoid growing the same group of vegetables in the same place. To make it easier to understand, we divide the vegetable garden into three or four zones and rotate the crops; leafy greens, fruit crops and root vegetables. If you divide it into four zones, you would create a ‘rest’ zone in addition to the three categories above.

Potatoes are an exception. You may think potatoes are root crops, but they are actually a member of the Solanaceae family. Having said that, potatoes are not very good to be grown with other vegetables in terms of ‘companion plants’. Therefore, some gardeners don’t include them in their rotation, but rather grow them in the same place repeatedly. To avoid your potatoes getting disease, it’s recommended to plant spring onions alternately.

There is also the opinion that radishes and carrots do better if they are continuously grown in the same place. Every gardener has a slightly different method and opinion. I think we should do experiments in our garden to find the best way.

2. Soil preparation

After you have grown your vegetables, the soil becomes less nutritious, so it is important to prepare the soil before you start growing the next year.

We make our own compost, but if we don’t have enough we buy it. When we buy compost, we mix it with the soil in our garden at the beginning of the season. Homemade compost is decomposed during the summer, so it is ideal to add it to the garden at the end of the season so that it will mature by the beginning of next season.

3. Companion plants

Some crops like to be grown with certain types of crops and others don’t. When you grow multiple plants in the same place or nearby, there are good combinations which help each other’s crops grow well and bad combinations which work vice versa. 

One of the best known is tomatoes and basil. Tomatoes are sun-loving vegetables, but they are not so greedy for water. Tomatoes taste better when grown in a sunny spot and slightly dry. The key is the steadiness of water supply. Basil, on the other hand, is a water-loving plant. So combining tomatoes and basil is a win-win relationship for both. More importantly, basil helps to keep tomato pests such as the aphid away.

Using companion planting techniques not only helps repel pests, but it can also reduce nutrient imbalance. We just need to be aware that some plants get along with each other and others don’t. If you choose the right crops, you can efficiently grow various vegetables and flowers. Even if you have a small garden your garden will be prolific. 

This is our companion planting plan in 2021

We want to have a good harvest, but we don’t want to use chemicals. Last year, we planted basil all over the vegetable garden, not just around the tomatoes, for repelling pests. Besides basil, marigolds are also a good company with most vegetable plants. They don’t only keep aphids away, but also attract pollinators.

The companion planting that we are planning this year is as follows;

  • Tomatoes + shiso (shiso and basil are in the same family and will have a similar effect)
  • Hot peppers + nasturtium + lettuce
  • Carrots + parsnips

Nasturtiums (capsicum) also help to keep aphids away and attract pollinators. It seems that lettuce and other Asteraceae plants can keep pests away as well. 

The combination of carrots and parsnips is a more effective use of farmland. We decided to give it a try because parsnips take a long time to harvest and in the meantime we can grow carrots.

Are there other solutions to reduce the risk of repeated cultivation damage?

The more I learn, the more interesting I find it. I saw a couple of videos which an experienced Japanese farmer provided. According to him, there are other ways to avoid the risk of disease which is related to continuous cultivation, although I thought some of them were not realistic for us. 

Anyway, the information that he provided and I found most interesting was that the risk of getting disease caused by monocropping lasts seven years at most. He said that your crop will grow well in the first year, but probably grow worse in the next year, if you consecutively plant the same crop in the same land. It may be bad or slightly better in the third, fourth year, but in the fifth or sixth year, you may find the crop growing nicely again. From his experience, most kinds of vegetables work alright after seven years of monocropping. So seven year monocropping is an extraordinary solution to avoid the repeated cultivation problem. 

Ultimately, it all depends on the condition of your land and climate too. I believe that we should give it a try when we have any idea how to get a better harvest, repeating trial and error. Our experience and knowledge are the most valuable, and then one day everything should pay off!

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