Key Management Techniques for Fresh-Eating Jujube in Summer and Autumn

I. Promoting Jujube Fruit Enlargement

The size of the fruit depends on the genetic factors of the variety itself, but scientific management measures have a relatively large impact on fruit size. The main technical measures for increasing fruit size in production are:

1. Strengthen soil, fertilizer and water management by increasing the application of organic fertilizer, deep plowing to improve the soil, and improving soil permeability, so as to achieve sufficient nutrition for tree growth and ensure jujube fruit enlargement and increased yield. Before fruit enlargement, apply an appropriate amount of phosphorus and potassium fertilizer as a top dressing. Generally, for trees in full fruit period, apply 0.75-1 kg of potassium sulfate or potassium-magnesium fertilizer per tree, either by flushing application or hole application. The effect of increasing fruit size is obvious, and it can also increase the sugar content of the fruit, making the flavor better. Increase foliar fertilizer application. During the entire growth period, foliar fertilizer can be sprayed 7-8 times. In the early growth stage, nitrogen fertilizer is mainly used, and in the middle and late growth stages, phosphorus and potassium fertilizers are mainly used. This can effectively improve the photosynthetic efficiency of leaves. During the critical period of water demand for jujube tree growth and development, timely irrigation should be carried out to meet the tree's water needs. This is a necessary condition for increasing fruit size.

2. Strengthen summer pruning to regulate nutrient supply During the growing season, promptly remove buds, thin out overly dense branches, and pinch off growing tips to improve the tree's nutritional status, save nutrients, and concentrate nutrient supply to the jujube fruit.

3. Reasonable load and strict control of fruit set rate Promptly thin out excess flowers and fruits, set fruit according to bearing shoots, and make the distribution of fruit on the tree as even as possible. Generally, jujube fruits between the 3rd and 8th leaves on a bearing shoot are large and of high quality.

4. Timely delay of harvest The period near physiological maturity is the key period for rapid fruit weight gain and quality improvement, so the harvest period should be appropriately delayed.

5. Spray plant growth regulators According to experiments in Hebei, Shaanxi and other places, starting from the hard stone stage of jujube fruit, spray Zaofeng No. 2 once every 10 days or so, for 2-3 consecutive sprays. Jujube fruit enlargement is obvious, and the yield increase effect is significant.

II. Promoting Jujube Fruit Coloration

Color is an important indicator of fruit quality. The main factors affecting fruit coloration are: sugar content, light, temperature, nutrients, water, etc. In production, the main technical measures to promote jujube fruit coloration are:

1. Properly control water before harvest Timely water supply can ensure normal fruit growth and development, but irrigation should be properly controlled near maturity. Doing so is beneficial to jujube fruit coloration.

2. Scientific fertilization and reasonable pruning In fertilization, the early growth stage should mainly supplement nitrogen fertilizer, and the middle and late growth stages should mainly use phosphorus and potassium fertilizers. At the same time, summer pruning should be carried out in a timely manner to improve ventilation and light conditions in the orchard, so as to promote fruit coloration.

3. Leaf removal Mainly used for large-fruit fresh-eating varieties. Generally, about 30 days before jujube fruit harvest, remove the leaves close to the fruit and shading leaves around the jujube fruit in stages and batches, so that the jujube fruit can receive sufficient light for coloration. Note that too many leaves should not be removed at one time, so as to avoid sunscald.

4. Change branch orientation In order to make the fruit receive light evenly and achieve full coloration, branch turning can begin 10 days after leaf removal to change branch orientation and comprehensively increase light. Carry this out in 2-3 sessions.

5. Lay reflective film During the fruit coloration period, laying silver-white reflective film under the canopy or between tree rows can increase light within the canopy, so that fruit in the inner canopy and lower part can fully color.

III. Preventing Fruit Cracking and Physiological Fruit Drop

1. Preventing fruit cracking Many jujube varieties often suffer fruit cracking to varying degrees when rain occurs during the maturity period. Fruit cracking mostly occurs in the crisp-ripe stage (the period from when the peel begins to turn partially red to when it turns completely red). Cracked jujube fruits not only suffer damage to appearance and quality and are prone to rot and deterioration (some varieties have a bitter taste after cracking), but also cannot fully mature, causing dried varieties to fail to meet standard grade requirements after processing and fresh-eating varieties to be unfit for consumption, resulting in great losses to production. Under normal circumstances, cracking losses account for 10%-30% of total yield, and in severe years losses can be as high as 50%.

To prevent fruit cracking, on the basis of selecting cracking-resistant varieties, sunscald of the peel in the early stage should be prevented. Covering the ground under the trees with plastic film or timely irrigation, especially not allowing the orchard soil to become excessively dry from mid-to-late August to early September, are effective measures to prevent fruit cracking. The effect of mulching under the trees is very obvious. For mature bearing trees, mulching to the edge of the canopy can basically prevent fruit cracking. Mulching should be carried out before the rainy season ends in early August. In jujube orchards where conditions permit, straw or green manure can also be used as mulch. For irrigation to prevent drought, it is required that from mid-August to early September, the soil moisture content at 0-20 cm below the surface should be maintained above 14%, and irrigation should be carried out in a timely manner before drought occurs. Alternatively, starting before the white-ripe stage, spray organic or inorganic calcium fertilizer on the leaves every 15 days until harvest.

2. Preventing pre-harvest physiological fruit drop Pre-harvest physiological fruit drop mostly begins about 15 days before maturity. In mild cases it accounts for 10%-15% of total yield, and in severe cases 40%-60%, greatly affecting jujube tree yield. Apart from being related to varietal characteristics, the causes of pre-harvest physiological fruit drop are directly or indirectly related to wind damage, high temperature and drought, excessive rainfall, insufficient sunlight, excessive nitrogen fertilizer, pest and disease damage, and imbalance of nutrient components.

To prevent pre-harvest fruit drop, on the basis of selecting good varieties, soil, fertilizer and water management and pest and disease control should be strengthened to improve tree resistance. About 10 days before the white-ripe stage of the fruit and again in the late white-ripe stage, spray once each with 50-70 mg/kg naphthaleneacetic acid (sodium), 20 mg/kg fruit-drop prevention agent, or Zaofeng No. 2, etc., which can reduce pre-harvest physiological fruit drop by 20%-80%. Hormone spraying should be carried out in the evening to enhance absorption by leaves and fruits, and care should be taken to spray the fruit surface and fruit stalk evenly.