Detailed Explanation of Key Points of Fertilization Techniques for High-Quality Banana Cultivation
1. Suitable planting density. Planting 120-130 plants per mu is relatively suitable, yielding higher production and better commercial appearance quality of bananas. 2. Suitable seedling age and planting time. The suitable planting seedling age is 9-10 leaves, and the planting period is mid-to-late March. In this way, the buds can emerge uniformly in mid-to-late October and be harvested in January-February of the following year....
(1) Fertilizer application rates for bananasAccording to foreign research, each Cavendish banana plant requires 150.5 g of nitrogen, 40.7 g of phosphorus, and 561 g of potassium per year. However, the plant can only absorb part of the fertilizer, of which nitrogen accounts for 50% of the applied amount (some say only 1/4), potassium accounts for 50% of the applied amount, and phosphorus accounts for only 20%-30% of the applied amount. That is to say, 50%-80% of the applied nitrogen, phosphorus, and potassium fertilizers are lost or fixed by the soil. Therefore, the fertilizer application rate should include the total of both the amount absorbed by the plant and the amount lost or fixed. To determine the reasonable fertilizer application rate for a given plantation, local climatic conditions must also be considered. The soil structure and fertility of the plantation, as well as the water supply situation, production goals (i.e., yield per unit area, single-crop or multi-crop banana cultivation, newly planted or ratoon), planting density, variety type, management level, and other factors. For example, Hainan Province should apply less fertilizer than Guangxi, potassium-deficient soils should receive more potassium fertilizer, the fertilization level for high yield and high quality must be higher than that for ordinary production, deep-hole application requires less than broadcast application, and so on. In banana plantations of the Pearl River Delta in Guangdong. When the yield is to reach 30,000-45,000 kg per hectare (2,000-3,000 kg per mu), the annual fertilizer application rate per plant is required to be 518-823 g of nitrogen, 186-297 g of phosphorus, and 750-1,185 g of potassium.
In order to make fertilization scientific and reasonable, that is, to meet the needs of banana growth and development and the requirements of production goals without applying excessive fertilizer and wasting it, it is best to conduct banana leaf nutrient analysis and soil nutrient analysis, guide fertilization according to the analysis results, and reasonably supplement the deficient parts according to the degree of deficiency.
(2) Ratio of the three major fertilizer elements for bananas
Different ratios of the three major elements nitrogen, phosphorus, and potassium in fertilizers will affect the absorption of nitrogen, phosphorus, and potassium by bananas and their growth and development. Based on the experience of formula fertilization for bananas in Guangdong, Guangxi, Fujian, Taiwan, China, and other provinces and regions in recent years, the author believes that to obtain good fertilization results, the ratio range of the three major elements nitrogen, phosphorus, and potassium should be 1:0.2-0.5:1.1-2.0. To determine a reasonable ratio of the three major elements nitrogen, phosphorus, and potassium for bananas, the following two points should also be achieved:
① It must vary according to the nitrogen, phosphorus, and potassium content in the soil of the plantation, especially the potassium content, and the ratio of nitrogen, phosphorus, and potassium; for soil very rich in potassium (exchangeable potassium reaching above 0.06%), it should be 1:0.3:0.5; for relatively potassium-rich soil (exchangeable potassium 0.025%-0.059%), it should be 1:0.3:1; for medium-potassium soil (exchangeable potassium 0.015%-0.0249%), it should be 1:0.3:1.1-1.3; for relatively low-potassium soil (exchangeable potassium 0.0075%-0.0149%), it should be 1:0.3:1.4-1.7; for low-potassium soil (exchangeable potassium only below 0.0075%), it should be 1:0.3:1.8-2.0.
② It must be determined according to the different growth and development stages of bananas. According to analysis results from Guinea in Africa, the required nitrogen-to-potassium ratio at the early stage of flower bud differentiation is 1:1.35-1.6, and at the late stage of flower bud differentiation it is 1:1.5-1.7. Exceeding or falling below the above ratios is unfavorable to the growth and development of bananas.
(3) Important fertilization periods for bananas
The nutrient demand of bananas generally increases as the leaf stage increases. The growth and development of bananas from the 18-40 leaf stage plays a decisive role in banana yield and quality, so this period is an important fertilization period for bananas. This period can be further divided into two heavy application periods: the mid-to-late stage of vegetative growth and the flower bud differentiation stage. Most of the fertilizer should be applied intensively during these two periods.
① Mid-to-late stage of vegetative growth (18-29 leaf stage), that is, 3-5 months after planting for spring-planted bananas, and 5-9 months after planting for summer-autumn planted bananas and after ratoon bananas sprout and set suckers. In terms of leaf shape, this period extends from the newly emerging middle leaves (at this time the newly emerged leaves are mostly curved like a tiger's tail) to the appearance of 1-2 large leaves. This period is in the peak stage of vegetative growth, with a very strong demand for nutrients and the most sensitive response. Whether the banana plant grows and develops well is determined by the adequacy of fertilizer supply. If heavy fertilizer is applied at this time, the banana plant can obtain sufficient nutrients and grow into a banana plant with broad late leaves and a thick pseudostem, carry out efficient assimilation, accumulate a large amount of organic matter, and lay a good material foundation for the next stage of flower bud differentiation.
② Flower bud differentiation stage (30-40 leaf stage), that is, 5-7 months after planting for spring-planted bananas, and 9-11 months after planting for summer-autumn planted bananas and after ratoon bananas sprout and set suckers. In terms of leaf shape, this period extends from the emergence of 1-2 large leaves to short, round fan-shaped leaves, and the leaf spacing begins to change from the widest to denser, with the rate of leaf emergence slowing down; in terms of the stem, the pseudostem develops to its thickest, and the corm (banana head) begins to emerge above the ground, taking on a jar shape; in terms of suckers, it has entered the period of vigorous sucker production. This period is in the process of flower bud differentiation for reproductive growth, requiring a large amount of nutrients for the growth and development of young panicles in order to form a fruit bunch with a large bunch and long fruit. According to foreign research, when vegetative growth later enters flower bud differentiation, the nitrogen content of the leaves drops sharply, because at this time a large amount of nitrogen is urgently needed for flower bud differentiation. When the nitrogen absorbed by the root system from the soil cannot meet the demand, nitrogen has to be transferred from tissues and organs such as leaves and stems. Applying heavy fertilizer at this time can promote maximum assimilation by the leaves, producing more organic matter for the formation and growth and development of young panicles.
(4) Number of fertilizer applications for bananas
Bananas have the characteristics of year-round growth, rapid growth, and large growth increments, while the climatic characteristics of our country are that high-temperature and rainy weather occurs during the optimal season for banana growth. After fertilizer is applied, it is prone to leaching, volatilization, and loss. Therefore, banana fertilization must implement the principles of frequent light application and heavy application during key periods.
In recent years, the number of fertilizer applications for bananas in our country has generally increased compared with the past, ranging from 5-9 times a year at the least to 10-20 times at the most. What number of fertilizer applications per year is appropriate? Someone once conducted an experiment on the number of fertilizer applications for bananas. The first group was applied 13 times, and the second group was applied 8 times, with the same total fertilizer application rate. Results: The pseudostem of plants in the first group was 15 cm taller and 2.7 cm thicker than that in the second group; all plants in the first group had emerged buds by mid-August, while the second group did not finish emerging buds until early September; the yield of the first group increased by 10% compared with the second group.
Applying fertilizer in multiple applications can minimize losses, improve utilization rate, and fully exert fertilizer efficiency. For banana plantations with sandy soil, the effect of applying fertilizer in multiple applications is even more obvious.
Based on the above circumstances, we believe that the more suitable number of fertilizer applications for bananas is 12-15 times throughout the year, including 5 heavy applications and 7-10 light applications.
(5) Types of banana fertilizers and fertilization methods
① Types of fertilizers. The fertilizers applied to bananas are divided into two major categories: organic fertilizers and inorganic fertilizers.
Organic fertilizers. Organic fertilizers, namely organic matter fertilizers, include human and livestock manure and urine, poultry manure, animal waste, crop stems and leaves and residues, plant ash, green manure, and other organic substances from animals and plants, as well as alluvial materials such as river mud, pond mud, and sludge, and contain relatively comprehensive nutrient elements. After application, organic fertilizers can improve the physical properties of the soil, improve the drainage and aeration performance of the soil, and after decomposition by soil microorganisms can increase soil humus and nutrient elements. Organic fertilizers are generally used as base fertilizer for newly planted bananas or as early spring fertilizer and overwintering fertilizer, while easily decomposable bran cake fertilizer can be used as flower bud differentiation fertilizer or seedling strengthening fertilizer.
Inorganic fertilizers. Inorganic fertilizers mostly belong to chemical fertilizers, have high element content, can dissolve in water or weak acid, are easily absorbed and utilized by bananas, have high and quick fertilizer efficiency, and are also very convenient to use. However, improper use of some inorganic fertilizers can cause soil compaction, excessive acidity, or alkalinity. Applying inorganic fertilizers together with organic fertilizers can overcome these problems. Common inorganic fertilizers used for bananas include nitrogen fertilizers such as urea, ammonium sulfate, ammonium bicarbonate, and ammonia water; phosphate fertilizers such as superphosphate, calcium magnesium phosphate, defluorinated phosphate, and phosphate rock powder; and potassium fertilizers such as potassium sulfate and potassium chloride. Compound fertilizers generally contain nitrogen, phosphorus, and potassium elements, with a ratio generally of 15:15:15. The banana BB fertilizer produced by a Canadian foreign-funded factory in Huangpu, Guangzhou, has a nitrogen, phosphorus, and potassium ratio of 1:0.2:1.33.
② Fertilization methods. There are two types of banana fertilization, namely rhizosphere fertilization and foliar topdressing. Rhizosphere fertilization is the main method, and foliar topdressing is supplementary.
Rhizosphere fertilization can be divided into liquid application and dry application, and dry application can be further divided into broadcast application, hole application, and trench application.
Liquid application. In liquid application, fertilizer is dissolved and diluted in water before application. For those that dissolve easily, use them immediately after dissolving; for organic fertilizers such as bran cakes and human and livestock manure, they must be composted and decomposed with water or human and livestock urine before use. After applying the slurry-like mixture, cover it immediately with a thin layer of soil. The advantage of liquid application is that the fertilizer easily contacts the root system, is easily absorbed, and does not injure the roots. During drought, it also serves an irrigation function.
Broadcast application. Broadcast application means scattering fertilizer on the surface of the bed, generally after the rainy season when the soil is still relatively moist. In sunny and dry weather when the soil is dry, broadcast application is not suitable. If broadcasting in sunny and dry weather, the bed surface must first be watered (irrigated) wet. Broadcast application should be done evenly, and it is best to water once after application. The advantage of broadcast application is that it saves labor, can expand the absorption area, and shows fertilizer effects quickly, but improper application can easily injure roots and cause loss and waste, especially from May to July when banana roots easily emerge from the soil, the fertilizer concentration must be well controlled.
Hole application. Hole application is to dig holes 30-100 cm away from the banana plant, with a depth of 15-23 cm (the size depends on the amount of fertilizer), place the fertilizer into the holes, and cover with soil. In dry weather, it must be thoroughly watered to facilitate the decomposition and dissolution of the fertilizer. The advantage of hole application is that it prevents fertilizer loss and causes less fertilizer injury, but the absorption area is narrow, the fertilizer effect is relatively slow, and it requires more labor. It is generally used for spring fertilizer and overwintering fertilizer.
Trench application. Trench application is to dig 1-2 small arc-shaped trenches 30-100 cm away from the banana plant, 15-25 cm wide, 35-50 cm long, and 8-15 cm deep, apply the fertilizer evenly in the trenches, and then cover with soil. The advantage of trench application, besides preventing fertilizer loss and causing less fertilizer injury, is that the absorption area is wider than hole application and the fertilizer effect is faster than hole application, but it also requires more labor. It is generally used for spring fertilizer, autumn fertilizer, and overwintering fertilizer, and is not suitable for use from May to July, because at that time the fine roots of banana plants are distributed throughout the plantation and exposed above the ground, and digging trenches easily injures the fine roots.
Banana foliar topdressing is the spraying of low-concentration liquid fertilizer onto the leaf surface or fruit surface. The advantage of foliar topdressing is that fertilizer is easily absorbed directly and quickly by leaves or fruits, can timely supplement nutrients, and meet the nutrient demands of banana growth and development, especially during the period from flower bud differentiation to young fruit development when a large amount of nutrients is needed. Through foliar topdressing, the required nutrients can be supplemented in time, playing an important role in improving banana yield and quality. On the other hand, when spraying fertilizer on leaf and fruit surfaces, the fertilizer absorption rate can be as high as 90%, significantly higher than rhizosphere fertilization. However, foliar topdressing also has shortcomings, mainly that each application amount is small, requiring multiple applications and more labor.
Which fertilizer to use for foliar topdressing needs to be determined according to soil nutrient element content, plant nutrient deficiency conditions, and different growth stages of bananas. Generally, urea (without biuret), ternary compound fertilizer (nitrogen:phosphorus:potassium at 15:15:15), potassium dihydrogen phosphate, foliar fertilizer (such as Yemianbao, etc.), and various trace fertilizers (zinc sulfate, manganese sulfate, ferrous sulfate, borax, neutral copper sulfate, etc.) are used. The concentration used should also be determined according to different fertilizer types and banana growth stages. For example, at the young stage (7-12 leaf stage), urea and ternary compound fertilizer should be 150-250 times dilution; from mature plant to young fruit stage (22 leaf stage to fruit at 40% flesh fullness), urea and ternary compound fertilizer should be 50-100 times dilution, potassium dihydrogen phosphate should be 250-350 times dilution, L�wang should be 800-1,000 times dilution, magnesium sulfate should be 2,000 times dilution, and other various trace fertilizers (zinc sulfate, etc.) should be 3,000-5,000 times dilution. Foliar fertilizers containing auxins such as Yemianbao should be 8,000-10,000 times dilution.
For foliar topdressing, the following should also be noted: use a sprayer with good spraying performance, with fine and uniform droplets; it is best to add 0.5% spreader (such as neutral laundry detergent); the best time for spraying is after 4 p.m.
Years of production practice have proven that combining banana rhizosphere fertilization with foliar topdressing has a better effect than single rhizosphere fertilization, can increase yield, and can also improve fruit quality, especially greatly improving peel color, fruit internal quality, and storage tolerance, while also saving fertilizer amount and reducing banana production costs.
(6) Fertilization for different banana cultivation types
Because banana cultivation times differ and target requirements differ, their fertilization times and frequencies also differ.
① Fertilization for newly planted bananas. Fertilization for newly planted bananas differs depending on spring planting and summer-autumn planting, and there are also differences in fertilization depending on whether the banana seedlings are sucker seedlings or tissue-cultured seedlings. The initial fertilization for tissue-cultured seedlings has already been discussed above, and the post-planting fertilization discussed here mainly refers to sucker seedlings. Initial fertilization uses liquid fertilizer for drenching.
Spring planting. For spring-planted bananas, about 20 days after planting. When the seedlings produce 1-2 new leaves, begin topdressing with dilute manure water or bran water or urea solution, once every 10-20 days, for a total of 3-5 applications. In May, apply 1 heavy late-spring fertilizer to promote banana seedling growth and cultivate strong seedlings. In July-August, when the total number of new leaves of the banana plant reaches 22-24, it has entered the flower bud differentiation stage. Therefore, from July to September, apply heavy fertilizer in two applications to promote flower bud differentiation and young panicle formation; between the two heavy applications, apply 3 light fertilizers (fertilization during this period both promotes flower spike growth and stimulates the emergence of suckers for the next crop), and by September 85% of the year's fertilizer has already been applied. In October, apply 1-2 more fruit-strengthening fertilizers, and in November apply 1 overwintering heavy fertilizer to lay a good foundation for fruit strengthening and the banana plant's overwintering. Within the 10 months of the year, the total number of fertilizer applications is 12-15, including 5 heavy applications and 7-10 light applications.
Summer-autumn planting. In the first year after planting and before the onset of winter, apply light fertilizer 3-4 times to cultivate strong seedlings. In late October, apply 1 overwintering heavy fertilizer to provide nutrients for the late stage of vegetative growth and enhance the plant's overwintering ability. In early March of the second year, apply 1 early spring heavy fertilizer to accelerate late vegetative growth and provide sufficient nutrients for the transition to the flower bud differentiation stage. In April-May it has already entered flower bud differentiation, so in April-June or May-July apply flower bud differentiation fertilizer heavily in 2 applications, with 3 light fertilizer applications in between, to promote early bud emergence and strong bud emergence of the banana plant, and to provide sufficient nutrients for cultivating strong seedlings for the next crop. From August to October, apply 3 more light fertilizers to strengthen fruit and at the same time promote the early-to-mid vegetative growth of the next crop of bananas. At the end of October, apply heavy overwintering fertilizer, and in December apply light fertilizer before overwintering, laying the foundation for the late vegetative growth of the next crop of banana plants. In the 17 months of the two years, the total number of fertilizer applications is 14-15, including 5 heavy applications and 9-10 light applications.
② Fertilization for ratoon single-crop bananas. Fertilization for ratoon single-crop bananas differs depending on whether spring-summer bananas or main-crop bananas are being cultivated.
Spring-summer bananas. In early March, apply 1 early spring heavy fertilizer to accelerate the development of the previous crop's fruit and the early vegetative growth of the current crop of banana plants. From March to May, apply light fertilizer 3 times, and in late May apply heavy fertilizer once to accelerate the early-to-mid vegetative growth of the current crop of banana plants. From June to July, apply light fertilizer 3 more times to promote late vegetative growth of the current crop of banana plants. From July to September, when the total number of growing leaves reaches 28-30, this marks that flower bud differentiation has begun. At that time, heavy fertilizer should be applied promptly 2 times to promote young panicle formation of the current crop of banana plants and the emergence of the next crop of bananas. From September to October, apply 1-2 fruit-strengthening and seedling-strengthening light fertilizers. At the end of October, apply heavy overwintering fertilizer, and in December apply 1 more light fertilizer to promote the development of the current crop's fruit and the early vegetative growth of the next crop of banana plants. In the 12 months of the year, the total number of fertilizer applications is 13-14, including 5 heavy applications and 8-9 light applications.
Main-crop bananas. In early March, apply 1 early spring heavy fertilizer to promote late vegetative growth of the current crop of banana plants. From April to July, it has already entered the flower bud differentiation stage, so flower bud differentiation fertilizer should be applied in two applications to promote flower bud differentiation of the current crop and the emergence of the next crop of bananas, with 3 light fertilizer applications between the heavy applications during the same period. From August to October, apply 3 more light fertilizers to promote the development of the current crop's fruit and the early-to-mid vegetative growth of the next crop of bananas. At the end of October, apply overwintering fertilizer, and in December apply 1 light fertilizer to enhance the overwintering ability of the banana plants and promote late vegetative growth of the next crop of bananas. In the 12 months of the year, the total number of fertilizer applications is 12, including 5 heavy applications and 7 light applications.
③ Fertilization for ratoon multi-crop bananas. Fertilization for ratoon multi-crop bananas should be based on the principles of early application and sufficiency. In the first year of newly planted bananas, in addition to applying sufficient base fertilizer, topdressing must also be done early and frequently. The annual fertilizer application rate should be 1/4-1/3 more than that for single-crop bananas, and the number of applications should be 2-4 more. In the first year, begin light topdressing 10-20 days after planting, and apply 4 times during March-April to promote early growth and rapid development of banana plants. In early May, apply 1 late-spring heavy fertilizer to accelerate the early-to-mid vegetative growth of banana plants. From May to June, apply light fertilizer 2 times to accelerate late vegetative growth of banana plants and promote the emergence of strong suckers for the next crop. From July to September, apply heavy fertilizer in two applications to promote flower bud differentiation and young panicle formation of the first crop of banana plants, and accelerate the early-to-mid vegetative growth of the second crop of banana plants. From August to October, apply light fertilizer 3 times to promote early bud emergence and strong bud emergence, while also accelerating the growth of the second crop of banana plants. At the end of October, apply 1 overwintering fertilizer, followed by 1 light topdressing, to strengthen the fruit of the first crop and lay the foundation for late vegetative growth of the second crop of banana plants, ensuring the smooth overwintering of fruit and banana plants. In February-March of the second year, apply 1 early spring heavy fertilizer to accelerate late vegetative growth of the second crop of banana plants and promote the emergence of strong suckers for the third crop. From April to June, apply spring-summer fertilizer heavily in two applications, with 3 light fertilizer applications between the heavy applications, to promote flower bud differentiation of the second crop and accelerate the early vegetative growth of the third crop. In July, apply light fertilizer once to promote the development of the second crop's fruit and late vegetative growth of the third crop of banana plants. From August to October, apply summer-autumn fertilizer heavily in two applications, with 3 additional light fertilizer applications during the same period, to promote flower bud differentiation of the third crop of bananas. In November-December, apply the final 2 light fertilizers to promote the development of the third crop's fruit. In the 10 months of the first year, a total of 15 applications are made, including 5 heavy applications and 10 light applications; in the 12 months of the second year, a total of 14 applications are made, including 5 heavy applications and 9 light applications.