When to plant sweet potatoes?

Sweet potatoes , as a food that is loved by people of all ages, are widely grown in China. Due to the differences in climatic conditions between the north and south of China, the planting time of sweet potatoes also varies accordingly. In Hainan and Taiwan, where the climate is warm, sweet potatoes can be grown all year round. Let’s take a look at when to plant sweet potatoes.

When to plant sweet potatoes?

As a sun-loving plant, sufficient sunlight is essential for sweet potato's photosynthesis and helps increase tuber yield. The most suitable temperature range for the growth of sweet potato tubers is 22 to 23 degrees Celsius, and the minimum temperature should not be lower than 16 degrees Celsius. Therefore, the best time to plant sweet potatoes in spring is in mid-to-late April, when the temperature is stable above 15 degrees Celsius. Summer sweet potatoes, also known as stubble sweet potatoes, are usually planted after the spring wheat is harvested in June. Sweet potatoes are mainly grown in spring and summer in areas north of the Huanghuai River. The planting time for autumn sweet potatoes is from mid-July to early August, and they are mainly distributed in southern provinces with warmer climates, such as Fujian and Jiangxi. Hainan Province, due to its unique climatic conditions, can grow sweet potatoes all year round, and the planting time for winter sweet potatoes is around November. It is crucial to choose the appropriate planting time according to local climatic conditions and plant the sweet potato seedlings in time, because late planting will shorten the growth period of sweet potatoes, resulting in reduced root swelling time, lower yield and reduced quality. It is estimated that for every day of delay in planting, the yield per acre may decrease by about 1%.

Sweet potato planting technology and management

1. Adequate base fertilizer and appropriate land preparation

Fertilization: Given that sweet potatoes are usually grown in sandy soils, sufficient base fertilizer is needed to enhance soil fertility and thus achieve high yields. It is recommended to apply about 5 cubic meters of farmyard manure per mu, combined with 25 kg of diammonium phosphate and 25 kg of potassium sulfate.

Land preparation: As a root crop, sweet potatoes grow best in an environment with deep soil, loose soil and good ventilation. Deep plowing helps increase soil thickness, improve soil aeration, and facilitate the enlargement of tubers. The general recommended deep plowing depth is 30 cm. Land with fertile soil is suitable for ridge cultivation, while land with poor soil and more sand is suitable for flat planting or low ridge cultivation.

2. Select the best varieties, plant early and plant at the right time, and plant at a reasonable density

Seed selection: Choose high-yield and high-quality sweet potato varieties, such as the virus-free Beijing 553, virus-free Xushu 18, Xinnong 1, Xinnong 431, Yanshu 27, Sushu 8, Yushu 7 and other short-vine high-yield varieties.

Transplanting time: Since late frost may occur around May 1st every year, it is recommended to transplant rice seedlings after May 1st to avoid frost damage.

Density: Sparse planting is suitable for long-vine varieties and fertile land, while dense planting is suitable for short-vine varieties and poor land. In fertile plots, 3,000 to 3,500 plants of long-vine varieties are planted per acre, and in barren plots, 4,000 plants of short-vine varieties are planted per acre. The row spacing is maintained at 60 to 70 cm and the plant spacing is 30 cm.

3. Field Management

Planting: Select healthy seedlings and use shallow horizontal planting method, with the seedling heads facing southeast and downwind to prevent wind damage. The burial depth is about 1.5 to 2 inches, with 3 to 4 leaves exposed above the ground. When planting seedlings, ensure adequate watering and timely replanting to ensure full seedlings.

Early tillage, frequent weeding and early management. Intertillage helps loosen the soil, increase aeration, raise ground temperature, and control weeds. Sweet potatoes are drought-resistant and should not be watered too much in the early stages, but appropriate irrigation can be used when the soil is too dry. For long-vine varieties, the stems should be pinched when they are about 30 cm long to promote branching and help increase yield.

Mid-term vine control: From July to August, the temperature is high and there is a lot of rain. The stems and leaves grow rapidly while the tubers expand slowly. Control should be the main focus to prevent the stems and leaves from growing too long. Long-vine varieties can be sprayed with paclobutrazol 2 to 3 times, and short-vine varieties can also be sprayed in appropriate amounts when their stems and vines are vigorous. Avoid turning over the vines and instead lift the vines to reduce damage to the stems and leaves, control excessive growth of the stems and leaves, and promote increased yields.

Later management: After August, rainfall decreases and drought is prone to occur, affecting the expansion of tubers. Timely watering can prevent premature aging of stems and leaves and promote the enlargement of tubers. For plots with yellow leaves and premature aging of stems and leaves, 10 kg of urea can be applied as potato-growing fertilizer in combination with watering. This period is the critical period for tuber enlargement. Spraying sweet potato growth hormone can increase the root system's absorption of fertilizer , shorten the internode length, increase leaf thickness and chlorophyll content, induce the transfer of nutrients to the tubers, and accelerate tuber enlargement. Spraying twice per acre with an interval of 15 days can significantly increase the yield.

The above is an introduction to the planting techniques and management points of sweet potatoes. In addition to the planting time, some other aspects of sweet potato planting also require more attention to achieve high yields.