Crop rotation is one of the cultural practices used to control pest and diseases in agriculture. Crop pests and diseases are the major limiting factors in crop production. The effects of various crop pests and deleterious diseases discourage most aspiring and practicing farmers. This is one of the causes of food insecurity across the globe. However, with crop rotation, this can be corrected at zero or no cost.
Knowledge is power; a knowledgeable farmer is a successful farmer. Like what I do tell people if you want to start any business, you need to know lots about the business. If you are reading this, I salute your quest for knowledge. Crop rotation is a very easy and cheap way to control crop pests and diseases.
I will be sharing my personal experience on crop rotation with tomato, cucumber, and cowpea as you read through.
There are several methods of controlling pests and diseases you can adopt in your farm irrespective of your scale of production. The use of chemicals like herbicides, pesticides, etc. are common in a commercial farm; however, crop rotation is also very effective when compared to using chemicals.
Crop rotation advantages are copious; you do not need to spend a dime on it. It is environmental-friendly as it does not pose any threat to the ecosystem. Unlike other methods of pest control, that cause pollution of the environment and contamination of the underground water.
What is crop rotation and why is it important?
Crop rotation is a systematic cultivation practice where different crops are grown on the same piece of land in a specified order. The principles of crop rotation aim at providing a favorable environment for the crops that are yet to be grown and an unfavorable environment for crop pests and diseases. Crop rotation serves two functions, namely:
- Crop pests and disease control
- Soil nutrient management.
How crop rotation be used to control pests and diseases.
I posted an article on methods of plant disease management where I discussed extensively on the conditions needed for any pest or disease to emerge. Part of the conditions is the environment.
The environment is the medium of cultivation; it is the habitat both pests and disease-causing agents called pathogen. If you can devise a technique to keep the environment sterile or unfavorable to pathogen survival, then, you will have no issue of pest invasion and diseases. One of the ways to keep the plant environment unfavorable for crop pest and disease pathogen is through the rotation of crops.
Some pests or diseases are common to specific plants. A good example is blight disease in tomato and whitefly in cassava. These pests or diseases do not only affect these crops alone but other members of the family where these crops belong.
How do I mean:
For instance, tomato belongs to the family Solanaceae where pepper and eggplant belong. This implies that any disease that affects tomato will also affect pepper, eggplant and other members of the family. This is common in all crops. If you have a tomato farm and a particular disease always perturbs you, say late blight also called tomato cancer. You cannot plant any of the crops that belong to the family Solanaceae because the disease will still emerge. The only way you can completely eradicate the disease is to adopt crop rotation.
Let me quickly reveal a secret to you.
Do you know that chemicals (example fungicide) do not completely control the disease intended for? Yes, they do not. They only manage the disease below the economic threshold level.
Crop rotation pest control system breaks the life cycle of any disease or crop pest. For a disease to remain endemic in your farm, it means the environmental conditions are favorable and the ecosystem is friendly to such disease, hence, the pathogen keeps multiplying spontaneously, especially when the host is from the same family.
However, immediately you rotate your crop with a crop from another family, trust me, you have completely destabilized the existence of the pests and disease pathogen. With this, they will not have any option than to vacate your farm because the environment and ecosystem no longer favor them; they no longer have what they love to eat.
Let me share my personal experience on this:
I used to manage a greenhouse tomato farm where every necessary pre-planting operation such as soil treatment; was done before the commencement of planting. Down the line, the tomato was transplanted and they were doing awesomely well. I had issues of flood at the flowering stage; it was an unfortunate situation.
The whole greenhouse was flooded and as a result, different pathogens found their way into the greenhouse. The most prominent of them was the late blight fungus, Phytophthora infestans. Within a period of 7 days, the bright green-colored tomato plants gradually turned to yellow and brown. It is a devastating experience.
Many measures were deployed to manage the situation; I started spraying broad-spectrum fungicides such as Mancozeb fungicide and lots of pruning was done to prevent the spread of the spores formed by the fungus. As expected, the disease was managed but not totally eradicated. At some point, all the tomato stands were thinned-out and the greenhouse stayed fallow for some weeks. I had a little harvest but very far from the expected yield.
Again, I continued my cultivation with cucumber this time in the same greenhouse after 4 weeks of fallow. The Cucumber did awesomely well but at the later stage, spider mites emerged; they were controlled organically using neem oil and black soap. After harvesting the cucumber, I began to reason the next line of action. I decided to plant cowpea; I was very skeptical about this but I did it.
The result was awesome; it was as if I had never cultivated on that soil. Throughout the period of cultivation, we recorded no pest or disease attack; remember it was a greenhouse. I was able to break the cycle of the late blight disease and the spider mites with cowpea, a legume, to allow the cowpea to grow and yield awesomely. This is how crop rotation works practically.
How to use crop rotation to manage soil nutrient management
Aside from controlling pests and diseases, crop rotation can also be used to manage the fertility of the soil. As you cultivate on particular land, year-in-year-out, the fertility of the soil decreases. However, you can replenish the soil nutrients using crop rotation.
This can be done through deliberate selection of some crops from the diagram of crop rotation. Legumes are known for fixing nitrogen in the soil. When you have legumes like soybean, cowpea or groundnut in the rotation, these crops fix atmospheric nitrogen in the soil through a symbiotic relationship formed between their roots and a bacterium called Rhizobium.
In terms of the requirement, the root crops need an appreciable amount of potassium to aid tuberization but require relatively less nitrogen. Fruit vegetables and cereals like maize, millet, tomato, pepper, cucumber, and watermelon need phosphorus in high quantity compared to other nutrients to aid fruiting. While the leafy vegetable, like celery, lettuce, and cauliflower need more nitrogen than other nutrient elements for good vegetative growth.
How to plan crop rotation allotment
In an ideal soil, primary elements needed by the crops, Nitrogen Potassium and Phosphorus are present in the soil in varying concentration. Looking at the crop rotation chart above, you would see that legumes come first. It is deliberate, this is because legumes will fix atmospheric nitrogen in the soil, thus, adding to the default quantity of the nitrogen in the soil.
After harvesting, the quantity of nitrogen present in the soil is higher than other nutrients present in the soil. Therefore, planting leafy vegetables here would be very nice because you would have a flamboyant vegetative growth; the leaves would grow so big with prominent stems.
It is compulsory you plant leafy vegetables first; because they help to reduce the quantity of nitrogen in the soil through their voracious consumption of it. Cereals or Fruit vegetables like maize, millet, tomato, pepper, cucumber, and watermelon can replace leafy vegetable in the subsequent cultivation.
Because they need a high level of phosphorus than other plants; it allows quick fruiting and increases flowering. If you plant cereals or fruit vegetables after legumes, you would observe high vegetative growth but delay in flowering and ultimately poor fruiting; this is because of the high nitrogen content of the soil. I hope you get the scope.
You can now plant Root crops after the harvesting the cereal or fruit vegetable. Root crops need a high amount of potassium; it aids tuber formation. In addition, after harvesting the root crop, you can now replant legumes to replenish the soil nutrient through the fortification of nitrogen. This is how the cycle goes on the same soil.
You can as well design your diagram of crop rotation putting different classes of crops that favor the rotation.
This is how the crop rotation works. It can either serve as a means of controlling pests and diseases or replenishing the soil nutrient. It can as well serve the same purpose simultaneously.
Information is power, with this technique; a farmer can systematically reduce the cost of production by eliminating the cost of fertilizer.
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