(1) temperature

Jujube is a warm-loving tree species, which needs high temperature during its growth and development. Jujube trees cultivated in the north germinate late and shed leaves early. When the temperature reaches 13 ~ 15℃ in spring (about mid-April in Cangzhou), jujube buds begin to germinate. When the temperature reached 17 ~ 18℃, the new shoots of jujube trees grew, the leaves spread, the flower buds differentiated, and the buds sprouted at 19℃, and the daily average temperature reached 20 ~. The suitable temperature for pollen germination is 22 ~ 26℃, and the pollen germination rate is significantly reduced below 20℃ or above 38℃. The suitable temperature for fruit growth and development is 24 ~ 27℃. When the temperature is low, the fruit grows slowly, with less dry matter and poor quality. The suitable temperature for fruit ripening is 18 ~ 22℃. Therefore, the temperature in flowering and fruiting period is an important limiting factor in jujube planting area. When the temperature drops to 15℃ in autumn, the leaves turn yellow and begin to fall, and all the leaves fall in the first frost period. It has a strong ability to resist extreme temperatures in winter, with a low temperature of -34℃ in hibernation and a short-term high temperature of 50℃ in summer.

The daily average fruit-setting temperature is an important factor in regional cultivation of jujube trees, which can be divided into wide-temperature type (the daily average fruit-setting temperature in flowering period is required to be above 265,438 0℃, such as Daguazhao, Banzao and Linyi Lizao, which are widely cultivated) and normal-temperature type (the daily average fruit-setting temperature in flowering period is not lower than 22℃, such as Jinsixiaozao, Junzao and Dali Zhao Yuan).

Different varieties have different tolerance to extreme high temperature and low temperature, different temperature required in each growth period, different requirements for soil environment, and different disease resistance and fruit cracking resistance. The characteristics of these varieties should be fully considered when introducing them, so as not to cause losses to production.

(2) Humidity

Jujube is a tree species with strong drought resistance and waterlogging tolerance, and has a wide adaptability to humidity. Annual precipitation 100 ~ 1200mm, and annual precipitation is 400 ~ 700mm. The lowest annual rainfall in Cangzhou is less than 100 mm, and the highest is 1 160 mm, all of which can grow and bear fruit normally, and the jujube orchard will not die after more than 30 days of water accumulation.

Different growth periods of jujube trees require different humidity. The flowering period needs high humidity, and the relative humidity of 70% ~ 85% is beneficial to pollination, fertilization and fruit setting. If this period is too dry and the relative humidity is lower than 40%, it will affect pollen germination and pollen tube elongation, resulting in poor pollination and fertilization, serious flower and fruit drop and decreased yield. The phenomenon of "burnt flowers" is caused by dry air and low relative humidity. If there is too much rainfall in the flowering period, especially if the flowering period is rainy and cold, it is not conducive to pollination, the pollen is easy to burst, it can not germinate normally, and the fruit setting rate will also decrease. In the later stage of fruit growth, it is required to have less rain and sunny days, high temperature in the daytime, low temperature at night and large temperature difference between day and night, which is beneficial to sugar accumulation and fruit coloring. If there is too much and too frequent rainfall, it will affect the growth and nutrient accumulation of fruit, aggravate fruit diseases such as fruit cracking and pulp rot, and reduce the quality of jujube fruit.

Soil moisture will affect the water balance in trees and the growth and development of various organs. The field water holding capacity of soil is about 70%, which is beneficial to the growth of jujube trees. When the water content of 30 cm soil layer is 5%, jujube seedlings will wither temporarily. When the soil moisture content is 3%, it will wither permanently. Too much water, poor soil ventilation, root system will affect growth due to suffocation, and long-term water accumulation will also cause jujube tree death.

(3) Lighting

Sunlight is the foundation of all living things, providing inexhaustible energy and realizing energy transformation through plants. Photosynthesis of plants, only under the action of light, converts carbon dioxide absorbed in the air, water absorbed in the soil (including water absorbed by leaves) and minerals into organic matter, releases oxygen, and converts light energy into chemical energy, thus completing energy conversion.

Appropriate light can promote the growth and differentiation of plant somatic cells, control cell division and elongation, maintain normal photosynthesis, and be beneficial to the accumulation of dry matter of trees and the healthy growth of various organs. For example, the differentiation and formation of flower buds, quality, fruit setting rate, fruit growth, coloring, sugar and vitamin C production are all directly related to light. Moreover, insufficient light will also affect root growth, because the nutrients needed for root growth mainly depend on aboveground photosynthetic products, and root growth will affect the growth and development of aboveground parts. Photosynthesis is also inseparable from water and minerals absorbed by roots.

At present, some winter jujube orchards in production are densely planted in order to achieve the goal of early fruiting. However, due to improper management, the jujube orchard is closed and the canopy is poorly ventilated and light-permeable, which leads to the increase of invalid leaf area, the decline of leaf productivity, the weakness of trees, the poor growth of jujube heads, secondary branches and jujube hanging, the low fruit setting rate, low yield, poor fruit quality, dead branches in the inner cavity, the outward migration of fruit parts, serious pests and diseases and so on. Therefore, it is necessary to carry out reasonable transformation of winter jujube orchard through winter cutting and summer cutting.

(4) Soil

Generally speaking, jujube trees have low requirements for soil and strong adaptability. They are barren and saline-alkali-tolerant, and can grow in soil with salt content not higher than 0.3% (coastal areas) within the range of soil pH value of 5.5 ~ 8.2. (pH is a numerical value indicating the acidity and alkalinity of soil solution. Any soil solution with pH less than 7 is acidic, and the smaller the pH, the stronger the acidity. The soil solution with pH equal to 7 is neutral, and the soil solution with pH greater than 7 is alkaline, and the greater the pH, the stronger the alkalinity). Plain wasteland and hilly wasteland can be planted, especially the Regulations on the Protection of Basic Farmland issued by the State Council 1998, which prohibits the occupation of basic farmland to develop forestry and fruit industry. The excellent characteristics of barren and saline-alkali tolerance of jujube trees are of special significance to the adjustment of agricultural industry and the increase of farmers' income in the future. Winter jujube and golden jujube planted in coastal saline-alkali land in Cangzhou area not only grow well, but also produce famous brand golden jujube and winter jujube with good quality and are famous at home and abroad. Mountain counties such as Zanhuang and Fuping in Hebei Province and Lvliang in Shanxi Province also produce famous dates, such as Zanhuang Jujube, Fupingpo Jujube and Lvliang Muzao. Nevertheless, planting jujube trees on plots with fertile soil and good environmental conditions can make jujube trees grow well, flourish, bear fruit early, have high yield, have good fruit quality and have high economic benefits even if the production input cost is low. Therefore, high-quality soil must be prepared before jujube tree planting to create good soil and environmental conditions for jujube tree growth.

(5) Wind

Breeze and breeze are beneficial to the growth of jujube trees, can promote gas exchange to maintain the normal concentration of carbon dioxide and oxygen in jujube trees, regulate the temperature and humidity of air, promote transpiration, and are beneficial to the growth, flowering, pollination and fruiting of jujube trees. Strong wind and dry hot wind are extremely unfavorable to the growth and development of jujube trees. Although jujube trees are very resistant to wind during dormancy, strong wind in germination will change the growth state of branches, inhibit normal growth and even break branches. Strong winds, especially dry and hot winds, will scorch flowers and buds or fail to pollinate them, reducing the fruit setting rate. When the fruit is blown by the wind in the late growth stage and before maturity, it will drop or reduce the quality of the fruit. In order to reduce the adverse effects of wind on the growth of jujube trees, we should avoid the tuyere when choosing a garden, plan to plant shelterbelts before building the garden, and take technical measures such as spraying water during flowering to improve the microclimate in the field and create a more suitable ecological environment for the growth and development of jujube trees.