Key Technical Points for Fertilization and Soil Management in Pineapple Orchards

Pineapple (scientific name: Ananas comosus), commonly known as fengli, is one of the famous tropical fruits. In Fujian and the Taiwan region of China it is called wangli or wanglai (ông-lâi), in Singapore and Malaysia it is called huangli, and in the mainland and Hong Kong, China it is called boluo. There are more than 70 varieties, and it is one of the four famous fruits of Lingnan.

Pineapple originated in the Amazon River basin region of Brazil and Paraguay in South America, and was introduced to China from Brazil in the 16th century. It has now spread throughout the entire tropical region. Its edible portion mainly consists of the enlarged fleshy inflorescence axis and the flowers arranged in a spiral on the periphery; the flowers usually do not set fruit, and the persistent perianth lobes enclose a cavity that contains shrunken stamens and styles. The fibers of the leaves are very tough and can be used for fabrics, making rope, knotting nets and papermaking.

Fengli and boluo are biologically the same fruit. In the market, fengli and boluo are different varieties of fruit: after peeling, boluo has “inner spines” that need to be removed; while fengli, after the outer skin is removed, has no “inner spines” and does not need to be scored with grooves. 

The requirements of pineapple for nitrogen, phosphorus and potassium fertilizers differ at each stage of growth and development. Overall, from planting to flower bud differentiation, the ratio of nitrogen, phosphorus and potassium fertilizers is 17:10:23, mainly nitrogen and potassium fertilizers; after flower stalk emergence, potassium fertilizer is dominant, and the ratio of the “three elements” is 7:10:23.

For pineapple fertilization, in addition to applying sufficient basal fertilizer before planting, reasonable supplementary fertilization must be carried out throughout the entire growth process according to the needs of each stage.

(1) Fertilizer for strong plants

This refers to fertilization during the vegetative growth stage from planting to flower bud differentiation. Taking pineapples planted in July to August as an example, about 40 days after planting, after the plants have produced new roots and resumed growth, applying ammonium sulfate once or spraying nitrogen fertilizer as a foliar feed 1 to 2 times is sufficient. In March and April of the following year, after the weather warms up in spring, the plants gradually resume growth and should be fertilized once. From April to September is the period of vigorous plant growth, with growth accounting for 70% to 80% of the whole year. Especially in June and July, when temperatures are high and rainfall is abundant, the plants grow vigorously and absorb large amounts of nutrients, so fertilizer should be applied heavily 2 to 3 times. Fertilization at this stage mainly consists of supplementary nitrogen and potassium fertilizers. In principle, nitrogen fertilizer should be applied heavily first and then lightly, to promote the growth of vegetative organs, while potassium fertilizer should be applied lightly first and then heavily, so that carbohydrates are fully accumulated in the plant, facilitating flower bud formation. In addition to root-zone fertilization, foliar feeding can also be carried out 2 to 3 times.

(2) Fertilizer for promoting flowers and strengthening flower buds

In November, one month before flower bud differentiation of the main crop fruit, flower-inducing fertilizer can be applied to promote flower bud differentiation and lay a good foundation for increasing yield. This fertilization is mainly potassium fertilizer, supplemented with an appropriate amount of nitrogen fertilizer. Then from late February to early March of the following year, before and after the flower buds emerge, apply organic fertilizer in furrows at 0.5 kg per plant and about 30 kg per mu of nitrogen and potassium fertilizers or compound fertilizer, to promote rapid recovery of plant growth after overwintering and robust growth after the flower buds emerge.

(3) Fertilizer for fruit development and promoting suckers

In early to mid-May, after pineapple flowering ends, the fruit enters a period of rapid growth and enlargement, and various types of suckers and slips also emerge successively. More potassium fertilizer and an appropriate amount of nitrogen fertilizer should be supplemented in a timely manner, so that the fruit grows and develops normally, fruit quality is improved, and vigorous growth of all types of suckers and slips is promoted. In addition to root-zone fertilization, foliar feeding with 0.2% monopotassium phosphate or 0.1% urea plus 1% potassium sulfate can also be used, which has a clear effect on improving fruit quality.

(4) Fertilizer for strengthening suckers

After harvesting fruit from June to September, heavy application of fertilizer for strengthening suckers is of decisive significance for the yield of the mother plants bearing fruit the following year. Usually, 40% to 50% of the following year's fertilizer amount is used for this fertilization, often by mixing high-quality organic fertilizer with quick-acting nitrogen and potassium fertilizers and applying it in furrows. To accelerate sucker growth, foliar feeding can also be carried out once a month. In densely planted orchards where root-zone fertilization is difficult, foliar feeding can be used.

Soil management 

1) Intertillage and weeding

Intertillage loosens the soil, allows rainwater to be stored, reduces rainwater erosion, reduces soil moisture evaporation during drought, and enhances water retention capacity. Combining intertillage with weeding can further reduce competition between weeds and pineapple for fertilizer and water, which is beneficial to the growth and development of the root system. Intertillage and weeding are generally carried out 3 to 4 times per year. When weeds flower, the first intertillage and weeding should be carried out. In May to June and July to August, when temperatures are high and humidity is high, weeds grow very quickly, so intertillage and weeding should each be carried out once. In autumn and winter, when rain is scarce, carry out intertillage and weeding once more, and turn the weeds into the soil.

2) Earthing up and mulching

Pineapple often uses suckers as successor mother plants, and because the suckers are positioned away from the soil surface, earthing up should be carried out in a timely manner after fruit harvest to promote new roots at their base and prevent lodging. In addition, pineapples planted on sloping land often have exposed roots due to rainwater erosion, so earthing up should also be carried out in conjunction with each intertillage and weeding, loosening the soil around the plants and mounding it at the base.

Mulching the soil surface in pineapple orchards can prevent weed proliferation, reduce moisture evaporation, keep the soil moist, loose and well structured, and can lower soil temperature in summer and raise soil temperature in winter. This allows the pineapple root system to grow well, thereby significantly increasing fruit yield and quality. Mulching materials can be rice straw or green manure stalks, and can also be asphalt paper and plastic film, etc.