When Is the Right Time to Apply Growth Control to Sweet Potatoes? A Detailed Guide to Timing and Techniques

AbstractThe first growth control application is during the sweet potato's swelling stage; the second growth control application is around 65-70 days after planting; the third growth control application is around 85-90 days after planting. Generally, growth control can be achieved by lifting the vines, cutting the vines, or using chemicals. Among these, cutting the vines not only effectively controls excessive vine growth but also provides sweet potato vines for feeding pigs, which helps save on feed costs.

I. Timing of Sweet Potato Growth Control

1. First growth control: During the first swelling stage of the sweet potato, when the vines are about 35-45 cm long and have begun to hang down from the ridges, commonly known as “lowering the beams,” or elegantly described as “two ridges seeming to hold hands yet not quite,” this is the branching and tuber-setting stage of the sweet potato, when branches form above ground and tubers form below ground, making it a critical period.

2. Second growth control: Generally around 65-70 days after planting, when the “rainy season” begins with high temperatures and high humidity. This is also the season when sweet potato stems and leaves grow rapidly, in a stage of simultaneous vine and tuber growth, but the tubers swell slowly, so growth control is needed at this time.

3. Third growth control: Generally around 85-90 days after planting, when the growth of sweet potato stems and leaves reaches its peak. To prepare for the arrival of the sweet potato's second swelling stage, timely growth control is also needed at this time. During the second swelling stage of the sweet potato, when the vines are about 60-80 cm long and the rows have basically closed, this is the golden period for sweet potato development, so growth control is particularly important.

II. Methods of Sweet Potato Growth Control

1. Vine lifting for growth control

(1) Generally, when sweet potato vines are 40-50 cm long, vine lifting for growth control produces better results. Its main purpose is to prevent the growth of fibrous roots on the sweet potato vines, which helps control nutrient loss and also effectively prevents excessive vine growth.

(2) Simply lift the sweet potato vines gently, but avoid damaging the stems and leaves. This helps prevent fibrous root growth. If using the vine-turning method for growth control, the vines can be turned over, but this easily damages the sweet potato stems and leaves. If the stems and leaves face the ground, it may also affect the sweet potato's photosynthesis, leading to reduced yield.

2. Vine cutting for growth control

(1) Vine cutting for growth control is a commonly used method in small-scale rural planting. In the past, rural sweet potato vines were mainly used to feed pigs. During the hot and rainy summer, sweet potato stems and leaves grow quickly, and the vines would be cut to feed the pigs.

(2) This not only effectively controls excessive vine growth but also provides sweet potato vines for feeding pigs, which helps save on feed costs.

3. Chemical growth control

For large-scale planting, chemicals are used for growth control to achieve increased yield and income. Commonly used growth control agents include paclobutrazol and chlormequat chloride. If the sweet potato has excessive nitrogen fertilizer, chemical growth control is less effective during hot and rainy seasons. Therefore, to achieve high sweet potato yields, apply less nitrogen fertilizer and more potassium fertilizer.