Why can't crops be planted repeatedly? (You can tell which crops can't be planted repeatedly at a glance)

The reason why crops cannot be planted repeatedly

There are many reasons why some crops cannot be planted repeatedly. One of them is that planting the same crop all year round will cause a particular lack of certain trace elements in the soil, thereby inhibiting the growth and development of subsequent cultivated plants.

For example, continuous cropping of wheat will significantly reduce the phosphorus content in the soil, and continuous cropping of soybeans will reduce the bioavailability of zinc in the soil, thereby affecting the efficiency of photosynthesis and reducing yields .

The metal ions in the soil will combine with malic acid and salicylic acid in the root secretions of tobacco, potatoes, tomatoes, peppers, etc. to form complexes, and with citric acid to form complexes and chelates.

Relatively speaking, the root system can absorb and utilize chelates at a higher level, which is why some crops that are not tolerant to continuous cropping will suffer from severe nutrient deficiency after continuous cropping.

Another point is that some crops have an excessive demand for certain trace elements , which causes the lack of some trace elements in the soil and leads to nutrient deficiency.

The second is pests and diseases. When planting crops that cannot tolerate repeated cropping, there will be some fungi and bacteria in the soil that will parasitize the crops.

Years of continuous cropping will make these pathogens more adapted to the soil environment of the crop and will also develop resistance to drugs, affecting the normal growth of the crop's roots, causing poor root growth and restricted growth of the aboveground parts.

Even if it is planted every other year, these remaining pathogens and insect eggs can still have a certain impact on it, which is called "back-stubble". For example, the incidence of corn head smut in corn planted for three consecutive years can be as high as 29.5%.

The third is the self-toxic effect of the roots. The roots of these crops that are not tolerant to repeated cropping will secrete toxins to poison the roots of adjacent crops.

When these crops are planted repeatedly, the toxins secreted by the roots will accumulate in the soil and have a toxic effect on the roots of the crops, resulting in poor growth, reduced yield and decreased quality.

For example, phenolic acids secreted by rice can inhibit the growth of subsequent rice seedlings.

Generally speaking, many crops in rural areas will not be planted on one piece of land for many years. In fact, most of them are due to the above three reasons.

If you plant crops like this all year round, pests and diseases will become more serious and the yield will be reduced. Therefore, it is better not to plant crops repeatedly.