High-efficiency cultivation technology of strawberry in open field in northern China

Open-air cultivation of strawberries is a basic and simple method that does not rely on protective facilities such as greenhouses, plastic greenhouses or small arch sheds. Instead, it protects the strawberry plants by covering them with mulch and straw before the soil freezes. Let’s learn together about the efficient open-field cultivation technology of northern strawberries.

1. Garden Selection

Strawberry gardens should be located in slightly acidic areas with high terrain, flat ground, convenient drainage and irrigation, and loose, fertile soil. Heavy clay, saline soil, swamps, saline-alkali land, windy areas or places susceptible to cold currents and frost damage should be avoided.

For previous crop fields that have been cropped for many years or have common diseases, the soil must be disinfected before planting strawberries. Commonly used disinfection methods include chloropicrin and dazomethane fumigation, but these agents are highly toxic. The solar soil disinfection method is now more commonly used, which is more effective in preventing and controlling strawberry wilt, bud blight and nematodes.

Specific operation: In the hot season before strawberry planting, apply about 1000kg of crop straw and other organic matter per mu, apply 50-60kg of lime nitrogen or appropriate amount of sulfur ammonia, then deep plow and ridge, cover with transparent plastic film, irrigate between ridges, keep sealed for 14-20 days, and maintain the soil temperature at 40-45℃.

2. Variety selection

There are many strawberry varieties suitable for open-air cultivation. When choosing, factors such as climatic conditions, terrain, fruit use and pollination varieties should be considered. The following are recommended varieties suitable for planting in different regions:

Northern region: Gorera, All Stars, Daselecte, Morioka No. 16, Mingjing, Mingxu, etc.

The middle and lower reaches of the Yangtze River: Shuofeng, Shuomi, Shuolu, etc.

North China: Xingdu No. 1, Xingdu No. 2, Shimei No. 1, Hani, Chunxing, etc.

Southwest region: Fengxiang, Chunxiang, Shizhuo No. 1, etc.

3. Planting

1. Preparation before planting

Before planting strawberries, sufficient base fertilizer should be applied, with 2000 to 5000 kg of decomposed high-quality organic fertilizer applied per mu. Fine land preparation is required, with the general tillage depth being 30 to 40 cm.

In the southern region, due to the high acidity of the soil, in addition to applying organic fertilizers, an appropriate amount of lime should be applied to increase the soil pH and improve the physical and chemical properties of the soil. Due to the heavy rainfall, high-bed cultivation can be adopted to facilitate drainage. The bed length is 10 to 20 meters, the width is 0.8 to 1 meter, and the height is 20 to 30 cm.

In some areas of the north, due to severe winter cold and spring drought, it is customary to use flat-bed cultivation on the ground to facilitate cold protection, heat preservation, and irrigation to prevent drought. However, this cultivation method can easily lead to waterlogging in the beds, affecting the quality of the fruit. In order to improve the quality and yield of strawberry fruit, open-field high ridge cultivation is now more commonly used, and supporting measures such as mulching and drip irrigation are used. The general ridge spacing is 75 to 80 cm, the ridge height is about 20 cm, and the ridge top width is 30 to 40 cm.

2. Planting period

The planting period is generally divided into autumn planting and spring planting, and autumn planting is more commonly used in production.

Autumn planting in northern regions is generally from early August to early September. At this time, most seedlings can meet the planting standards, the planting time is long, and it is the rainy season in the north, the soil moisture and air humidity are high, the seedlings grow quickly, and the survival rate is high.

Autumn planting in southern regions is generally from early October to early November. Seedlings for open-field cultivation are generally selected directly from the seedling propagation nursery, and sometimes transplanting is also used. Selecting strong seedlings is the basis for obtaining a high yield. Generally, they are required to have a well-developed root system, short and thick petioles, 4 to 5 mature leaves, and a new stem that is more than 0.8 cm thick. Watering thoroughly before transplanting the seedlings helps keep the plant's root system intact and increase the water content of the seedlings.

3. Planting density

The planting density generally depends on factors such as soil fertility, variety characteristics, seedling size, management level, and planting time. Generally, 8,000 to 12,000 plants are planted per mu.

In the northern region, high ridge planting is generally carried out with a planting density of 2 rows per ridge, a plant spacing of 15 to 18 cm, and 9,000 to 11,000 plants per mu. In traditional flat-bed planting, the spacing between rows and plants is generally 20cm×(20～25)cm, with 3～4 rows per bed and about 10,000 plants planted per mu.

In the south, the row spacing generally used is 25 to 30 cm, while the plant spacing depends on the variety; generally 16 to 20 cm.

4. Planting depth and precautions

When planting, dig holes at a predetermined distance, spread the plant roots into the holes, allow the roots to combine with the soil, and fill and compact the soil. The planting depth is the key to survival. The reasonable depth should make the rhizome flush with the ground, so that "the heart is not buried deep and the roots are not exposed shallowly". Water immediately after planting.

Pay attention to the direction when planting. When planting on high ridges or high furrows, the arch should face outward so that the fruits hang on one side of the furrow, which makes harvesting and management easier and reduces damage from pests and diseases. When planting in flat beds, the direction of the inflorescence should be toward the inside of the bed to prevent the inflorescence from extending onto the bed stalks and being stepped on during operation.

4. Management after planting

1. Weeding

After strawberries are planted, inter-cultivation and weeding are required frequently. Inter-cultivation can also be combined with topdressing and soil cultivation. Mulching can prevent weeds, increase ground temperature, retain soil moisture, improve soil structure, promote root growth, advance flowering and fruiting, and prevent berries from touching the ground. It is an effective measure to increase strawberry yield and quality and is suitable for various strawberry cultivation methods. If mulching needs to be combined with wintering to prevent cold, it is usually done after watering the soil before it freezes. In northern areas, it is usually done in mid-to-late November. It is advisable to choose a ground film with a thickness of 0.008 to 0.02 mm.

2. Remove the runners

Runners consume nutrients from the mother plant and reduce yield. Removing runners from the beginning of flowering to the end of fruit harvesting is an important management measure. At the same time, old and diseased leaves should be removed in time. When the mother plant sprouts more tillers, especially strawberry plants that are planted for many years often sprout lateral buds and weak buds close to the ground, usually only 1 to 3 fully developed lateral buds are retained, and excess tillers and weak buds should be removed at any time. For multi-year strawberry gardens, it is also necessary to cut off the old leaves above the ground after the fruits are harvested to reduce the occurrence of runners, increase the number of flower buds, and improve the yield in the following year.

3. Thinning flowers and fruits

Strawberry has many flowers, and the higher-order flowers are often infertile and become ineffective. Even if some can form fruits, they are too small to be harvested and become useless. Flower thinning is the process of removing an appropriate amount of high-grade flower buds during the bud separation period before flowering, so that nutrients are concentrated on the remaining flowers, promoting fruit size growth, improving quality, and concentrating the ripening period.

Fruit thinning is the process of removing deformed, diseased and insect-infested fruits in a timely manner when the young fruits are green. Poor pollination, low temperatures during flowering, or high temperatures above 35°C can easily lead to deformed fruits. Releasing bees during the flowering period is the most effective measure to prevent deformed fruits. At the same time, spraying pesticides should be strictly limited during the flowering period.

4. Fertilizer and water management

The root system of strawberries is shallow, so watering and fertilizing should focus on the flowering period and fruit expansion period, with nitrogen, phosphorus and potassium reasonably combined and applied in small amounts and multiple times. For open-field strawberries, it is recommended to combine irrigation and apply 9-10 kg of urea and 4-8 kg of potassium sulfate per mu during the flowering period. You can also apply 15-20 kg of high-nitrogen and potassium compound fertilizers with a total nitrogen, phosphorus and potassium nutrient content of not less than 45%; during the fruit expansion period, apply 11-13 kg of urea and 7-10 kg of potassium sulfate per mu, or 20-25 kg of high-nitrogen and potassium compound fertilizers with a total nutrient content of not less than 45%.

Foliar fertilization can be carried out during the budding stage, flowering stage, and flower bud differentiation stage. In addition to preventing nutrient deficiency, it can also increase the photosynthetic intensity of strawberry leaves, promote root development, increase fruit yield, improve fruit quality, make the fruit more delicious, and the commercial price higher. In the middle and late stages, you can spray foliar fertilizers such as 0.3%-0.5% urea solution, 0.3%-0.5% Mengbaolong high-purity potassium dihydrogen phosphate solution, 0.1%-0.3% boric acid solution, 0.2% calcium sulfate plus 0.05% manganese sulfate (volume 1:1) alone or in combination with spraying pesticides .

For micro-irrigation fertilization, according to the nutritional characteristics and needs of different growth periods, the pH value of the fertilizer solution can be adjusted, and appropriate amounts of heavy superphosphate, superphosphate, calcium-magnesium phosphate fertilizer, borax, amino acid chelated zinc, manganese, copper, molybdenum and other fertilizers containing medium and trace elements can be added to supplement or adjust the nutritional components and proportions of the micro-irrigation fertilizer solution, which can achieve a fertilization effect equivalent to or even better than foliar fertilizer.

5. Harvesting, grading and packaging

1. Harvesting

The maturity of strawberries at harvest depends on climate, usage and sales method. Fresh fruits are usually harvested when they are 90% ripe, that is, before the red part of the fruit surface reaches about 90%, for easy transportation. Fruits used for processing wine, juice and jam must be fully mature. The fruits used for making canned syrup should be harvested when they are 80% ripe, that is, when the red part of the fruit surface reaches about 80%.

2. Grading and packaging

In the past, bamboo baskets, baskets, basins and other containers were mostly used for harvesting. In recent years, paper boxes, cardboard boxes, plastic boxes, plastic crates, etc. are mostly used. Soft paper or soft cloth is placed on the fruits before picking. The fruits are picked, sorted and packed at the same time, which has high work efficiency and less damage.

After harvesting, the fruits should be graded according to their size. In order to increase the value of the product, the grading standards currently used in various places are as follows: first-grade fruits weigh more than 15g, second-grade fruits weigh more than 10g, third-grade fruits weigh more than 6g, and other fruits weigh less than 6g. Foreign fruits include deformed fruits, dry and pointed fruits, rotten fruits, dead fruits and over-ripe fruits, and they cannot be put on the market. During the grading and packaging process, care must be taken to prevent the strawberries from being exposed to direct sunlight. Packaging is the last important link in the strawberry production process to ensure the quality of berries and improve the commercial rate. After packaging, strawberries need to be placed in a ventilated and cool place or shipped in a timely manner.

The above is an introduction to the key points of open-field cultivation technology of northern strawberries. You can plant them in the appropriate season, and high yields can be achieved with proper management.