What are the technical measures for growing fruit trees on saline-alkali land?

Growing fruit trees on saline-alkali land is relatively difficult; without improvement, the survival rate is relatively low. The measures we have explored for planting fruit trees on saline-alkali land are described below:

I. Adopt raised-bed and strip-field planting to leach salt and drain alkali

The width of the constructed raised beds and strip fields should preferably be 40 m, with a length of 300-400 m. Each raised bed or strip field serves as one plot, with a land area of about 1.33 ha per plot. Branch canals connect to main canals; the branch canal has a top width of 2.5 m and a depth of 1.8 m. Field ditches connect to branch canals; the field ditch has a top width of 2 m and a depth of 1.5 m. Regularly clean and dredge the main, branch and field ditches to ensure smooth drainage and salt leaching in the orchard. Generally, desilting is done once every 2-3 years to maintain the required depth of all types of channels.

II. Dig large planting holes, apply fertilizer to improve the soil, or replace the soil

Saline-alkali land generally has a shallow plow layer, and the subsoil is compact, sticky and hard, which is unfavorable for fruit tree root growth. Before planting, dig planting holes 1 m square and 80-100 cm deep. First fill the bottom of the hole with a layer of crop straw and weeds about 20 cm thick, then mix the topsoil with organic fertilizer and fill it into the hole. Apply 50 kg of organic fertilizer and 0.25-0.5 kg of phosphate fertilizer per hole, tamping while filling. Wherever there are alkaline clods, the surface soil with high salt content should be removed and replaced with nearby topsoil of low salt content, to prevent the weak salt tolerance of newly planted seedling roots from reducing the planting survival rate.

III. Lower the height of the tree basin

According to the salt movement pattern that water flows to low places and salt moves to high places, lower the height of the tree basin. Generally, the tree basin should be 5-15 cm lower than the ground surface, which helps avoid salt and accumulates rainwater to suppress alkali. Because the ground between fruit tree rows is high and water evaporates quickly, salt accumulates on the ground surface with water, playing a role in salt accumulation.

IV. Select rootstocks with strong salt tolerance

Using apple seedlings grafted on Huailai Baling Begonia (Malus micromalus) rootstock for planting can not only increase the survival rate, but also show strong tolerance to saline-alkali conditions and low-lying wet conditions. Only by using Baling Begonia seeds to raise seedlings and carry out domestication training on saline-alkali land can young apple trees grow normally. Other begonias perform poorly as rootstocks, especially apple trees on Shan Ding Zi (Malus baccata) rootstock, which often show small and thin leaves, chlorotic and yellow leaf color, and a low planting survival rate.

V. Plant in autumn to skillfully avoid the peak period of salt return

Spring is dry and windy, soil moisture evaporates quickly, and this is the peak period of soil salt return. Planting young seedlings in spring, when roots have weak salt tolerance, affects the survival rate. With autumn planting, the root recovery period is long, and before the soil freezes the young seedlings are pressed down and covered with soil for cold protection, resulting in a high survival rate and rapid resumption of growth in spring.

VI. Artificially create clods and use clods to suppress alkali

For seedlings planted in autumn, after the trunk is headed in spring and they survive, it is exactly the peak period of salt return. Because the surviving young trees have very weak root absorption capacity and salt tolerance, after light rain the salt in the soil is brought to the soil surface, and the rapid evaporation of water often causes the young trees to suffer salt damage and die. Therefore, in spring, deep hoeing around the tree basin multiple times or deep digging with a three-tooth hoe should be used to create clods, so as to cut off soil capillaries and prevent the trees from salt damage.

VII. Plant green manure crops such as Sesbania cannabina between rows

Planting green manure crops such as Amorpha fruticosa and Sesbania cannabina along the edges of ditches, and regularly cutting and turning them under, can increase the organic fertilizer content in the soil, improve the soil, and play a role in preventing alkali and improving the soil.

VIII. Cover the tree basin with grass to improve soil physical and chemical properties

Covering the area under the tree basin with grass or crop straw can effectively reduce soil moisture evaporation, prevent salt return, and also play a role in raising temperature, preserving moisture, increasing soil organic matter, promoting microbial activity, and improving soil physical and chemical properties. It is a cultivation system in saline-alkali soil management with low investment, quick results and easy promotion. Experiments have shown that on saline-alkali land, covering the soil under trees during the initial fruiting period can increase yield by more than 26%, with a grass-covering thickness of 20-30 cm.

IX. Appropriately reduce tree canopy height

Head low and form the canopy early, first promote and then control, expand the canopy as quickly as possible, and increase the rate of ground coverage by the canopy to reduce ground moisture evaporation and prevent soil salt return. Generally, the heading height is 60-70 cm. According to the characteristics of fruit trees on saline-alkali land, such as shallow root distribution, high groundwater level and easy premature senescence of branches, appropriately arrange more large and medium-sized branch groups on the lower primary and lateral branches to enhance the renewal ability of branch groups, prolong the life of fruiting branch groups, and pay attention to controlling new shoots of young trees to stop growing early, so as to promote lignification of branch tissues and reduce the occurrence of freezing damage. Through measures such as increasing organic fertilizer year by year to improve soil and suppress alkali, reducing the number of irrigations, frequent intertillage, foliar fertilizer spraying, and raising the level of nutrient accumulation in the tree, the tree vigor can be kept strong, laying the foundation for rapid growth and high yield of young trees.

Qu Weiwei, Yang Jing, Forestry Bureau of Jizhou District, Tianjin