As a large-scale herbaceous fruit tree, the bananas are loose and loose, the plants are juicy, and the water content of each organ is high. In addition, the leaves have a large transpiration effect, shallow rooting, and the deep soil water utilization capacity is weak, so wet and avoid drought, therefore, the banana is growing. The amount of water required during development is very large, and the lack of water will restrict the high-quality and high-yield of bananas, or induce diseases, and increase the cost of protection.
It is generally believed that a banana plant with an annual rainfall of 1800 to 2500 mm and a uniform rainfall distribution (150 to 200 mm per month) is ideal, and the soil of the banana plantation can always maintain an appropriate amount of water. Although the annual rainfall of banana production areas in South China can generally meet the needs of bananas for water, the monthly precipitation in the spring and autumn of the banana area is often less than the minimum water requirement of the 100 mm banana plantation. The autumn drought and spring drought directly affect the banana. Growth results, especially those that are not drought tolerant (such as fragrant banana, dragon tooth banana), are severely affected by drought.
In the case of drought or low rainfall, in addition to timely watering to avoid water shortage, cross-linked polyacrylamide, which is a soil water retention agent, is applied around the roots of banana plants at the time of planting or planting. Another effective measure to ensure the normal growth of bananas and high yield and stable yield of banana plants. When the banana is planted, the water-retaining agent can resist the spring drought, improve the survival rate, promote the growth and growth of the banana seedling, and effectively avoid the adverse effects of autumn drought on banana flower bud differentiation and bolting.
Second, the type of water retention agent
Water-retaining agent is a kind of super absorbent resin, which has been widely used in drought-resistant planting because of its repeated "absorption-preservation-release" moisture characteristics. At present, polymers having water retention functions which are common in the market are classified into three major categories, namely, acrylamide-acrylate crosslinked copolymer, sodium polyacrylate and starch grafted acrylate. Each type of water retaining agent has a variety of products with different proportions and synthetic processes, mainly in terms of water absorption, water retention and weather resistance. The different thicknesses of the same product also have different performances in the soil. Therefore, it is necessary to analyze and select according to the characteristics of crops (length of growth). The table below lists the reference values ​​of the main components of the three types of water retaining agents (omitted), which are different in composition and use.
Third, the mechanism of action of water retention agent
The water retaining agent contains a large number of structurally specific strong water-absorptive groups, which can absorb hundreds of times to thousands of times of deionized water. The water absorption rate and stability of the water retaining agent are closely related to its molecular structure and the amount of crosslinking agent. Sodium polyacrylate and starch grafted sodium acrylate water retention agent are self-crosslinking types with high water absorption ratio but low stability; acrylamide-acrylate cross-linking copolymer has self-crosslinking and cross-linking at the same time. High stability. In addition, the amount of the crosslinking agent is small, the water absorption ratio is high, and the stability is low; on the contrary, the amount of the crosslinking agent is large, the water absorption ratio is low, and the stability is high. Sodium polyacrylate and starch grafted sodium acrylate water retaining agent have an effective service life of only about 1 year, while acrylamide-acrylate crosslinked copolymer has an effective service life of more than 3 years.
The water-retaining agent expands into a hydrogel after water absorption, and is applied to the soil to enhance the water retention performance of the soil. When the soil is dehydrated, the water is slowly released for absorption and utilization of the roots of the banana plant. If 2 ‰ (loam) ~ 3 ‰ (sand) water retention agent is added to the root layer soil, the soil water content can be long-term within the suitable soil water content above the wilting point, and the suitable soil moisture period is extended by 2~3. Times, delaying the emergence of wilting. At the same time, it reduces the deep leakage of soil moisture and the loss of soil nutrients, and improves the water use efficiency and utilization efficiency of the banana plantation. More importantly, the repeated shrinkage and swelling of the water retaining agent caused a lot of pores in the soil, improved the permeability and water permeability of the soil, improved the rhizosphere ecological environment, enhanced the activities of the rhizosphere microorganisms, and accelerated the rhizosphere. The decomposition of the surrounding organic minerals is conducive to root absorption, promotes the growth and development of roots and plants, improves the soil matrix, and prevents soil compaction. Professor Liao Zongwen from South China Agricultural University found that by applying water-retaining agent, the phosphorus in the soil can be activated, which is beneficial to the development of strong fibrous roots.
Fourth, the choice of planting banana water retention agent
RT-3005 series products are high-quality, high-purity acrylamide-acrylic acid potassium salt cross-linked copolymers produced by SNF of France for agriculture, horticulture and forestry. They are ideal materials for banana planting and have other brands of water retention agents. Unusually long weathering, superior water release characteristics and safety for plants and the environment. At different stages of banana planting activities, RT-3005 water retention agents with different particle sizes can be selected.
In the cultivation stage of banana seedlings, the medium-thickness with a particle size of 0.3-1.0 mm is selected and mixed into the culture bag or the medium of the cultured sputum in a weight ratio of 1:500, which can reduce the frequent watering at the seedling stage and maintain the root system suitable for stability. Temperature and humidity accelerate seedling growth. The most important thing is that after the seedlings are transplanted, the seedlings with water-retaining agent in the root soil can better adapt to the environment of the banana garden, avoiding the slow seedling process and avoiding the occurrence of dead seedlings.
When transplanting banana seedlings, it is necessary to use a coarse-grained water-retaining agent with a long water-holding period, a long-term stable water retention and fertilizer retention in the soil, and a particle size of 1.0-3.0 mm. The amount of water-retaining agent applied should be determined according to the water supply situation of the banana plantation and the management level of the banana plantation. For the banana plantation where the growth of the banana plant is abundant or the investment is difficult, in order to ensure the basic quantity of the banana plant, the seedling application amount of 4 to 5 g per plant can be used, and the water retention agent per acre of banana plant is about 0.5 kg. For the banana plantation with poor natural precipitation distribution, in order to obtain high-yield and high-quality results, 50-100g per acre of water-retaining agent for banana garden can be applied for 6~12kg. The application method can mix the water retaining agent back into the filling soil and apply it to the depth of the planting hole in the range of 10 to 30 cm. It can also be drilled with the soil layer around the banana plant and applied to the drilling depth of 10 to 30 cm. After the water-retaining agent absorbs water into a gel, it can maintain a suitable soil moisture content for about 25 to 30 days, and 95% of the water-absorbing fraction can be used by the plant. However, when there is no rain for more than 45 days, artificial irrigation should be used to replenish water.
5. Method of applying water retaining agent in banana garden
Divided into ditch (hole) casting, guest soil bag casting, rapid seedling method and drilling application method. The water retaining agent can be applied dry or wetted into a gel, and the desired method can be selected according to specific conditions.
Ditch (hole) casting
For the banana plantation with irrigation conditions, the water retaining agent can be applied dry, and the mountain water with limited irrigation conditions should be applied with the hydrogel retaining agent. It can also be applied to the soil before the rainy season, and then planted after the rain has been increased.
The specific practice of applying water-retaining agent to planting seedlings is: after digging the well-planting points, put 500 g of gel that has been fully swelled and swelled at each hole (about 3 to 4 g of dry-grain water-retaining agent), and then lightly remove the bagged banana seedlings. On the gel, backfill the soil, slightly compacted
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