The correct methods and key technical points of root-pruning (seedling hardening)

Root-pruning is a traditional crop management technique, a technical measure used in crop cultivation to suppress excessive vegetative growth of seedling stems and leaves and promote root development. So, what are the methods of root-pruning?

1. What are the methods of root-pruning?

There are two commonly used methods of root-pruning. The first is to control fertilizer and water during the seedling stage, so that the internodes of the plant become thick, short and sturdy, with a well-developed root system. The second is to carry out repeated intertillage, so that the surface soil is loose and dry while the subsoil retains moisture well, which helps the roots extend deeper, controls excessive growth, increases carbohydrate accumulation in the plant, and makes it grow robustly.

Root-pruning measures also include scraping away soil to expose the roots to the sun, in order to raise ground temperature and so on. The timing and specific operation methods of root-pruning vary with the crop. Spring-sown crops such as sorghum and corn generally have soil scraped away to expose the roots from the thinning stage to before jointing; crops and vegetables grown from transplanted seedlings mostly have watering controlled in the seedbed for drought hardening, or are transplanted into a nursery bed, in order to suppress the growth of aboveground vegetative organs, strengthen resistance to adverse external conditions, and shorten the post-transplant recovery period.

2. Benefits of root-pruning for corn

1. Controlling plant growth vigor can slow the aboveground growth of corn seedlings, promote robust growth, shorten the internodes, and improve lodging resistance.

2. Promoting a well-developed root system can make the underground root system of corn well developed and deeply rooted; improve the plant's lodging resistance; enhance root vigor and the ability to absorb nutrients and water, suppress vegetative growth, and promote reproductive growth.

3. Increasing corn yield. Trials show that after root-pruning, corn yield can generally increase by 7%-12%.

3. Precautions for root-pruning of corn

1. Root-pruning of corn should follow the principle of “prune the dark, not the yellow; prune the fat, not the thin; prune the wet, not the dry.” That is, plots with dark green seedlings, fertile soil, and good soil moisture can be given root-pruning; otherwise, root-pruning should not be done, and instead extra fertilizer and water management should be adopted.

2. The time for root-pruning is generally best from after corn emergence to the jointing stage.

The timing and specific operation methods of root-pruning vary with the crop, so before root-pruning you can first learn about the growth of the crop.