It is very easy to grow leek plants. A detailed account of growing practices for leek is given below:
Climate: Climatic and soil requirements for growing leek are same as those of onions. The requirements of day length of different varieties may differ and therefore, it is advisable to grow only those varieties which are acclimatized to your locality. Temperature is more important than the length of day during seed-stalk development.
Soil: Soil for growing leek should be rich in humus and organic matter. Leeks can be grown on a wide range of soil provided that soil is well-drained with deep, fertile top soil. However, coarse sandy soils should be avoided. Leek is sensitive to high acidity in the soils. Optimum pH range is 6.5-7.0.
Propagation: Propagation is by seeds. Seeds are sown in the well-prepared nursery beds before the winter season in the tropics. Nursery-beds should always be kept weed-free. A plant density of 70 plants/sq. meter area may be followed while sowing seeds. Seeds germinate within one or two weeks. Hardened seedlings of one to two months old are transplanted in the main field (or when they attain 15-20cm height).
Site/Field Preparation: Main site is prepared by ploughing, levelling and by incorporating organic manures and fertilizers into the top soil. Generally, 10 to 20 metric tons of farm yard manure is incorporated into the top soil to enhance soil fertility. After that trenches are prepared in the field. Each trench is of 30-45 cm deep. Seedlings are planted in these trenches.
Planting: The transplanting is done in trenches prepared in the field. A spacing of 10-15 cm may be followed within a row. Spacing between rows depends on varietal type and other parameters such as ease of intercultural operations; normally it would be about 60-90 cm. Soon after planting, a light watering is done. Plants grow vigorously and soon get established in the fields. Once plants are established, soil around the plant base is earthed up regularly exposing the base of the plants as they grow. Lower portion/base of the plants is sufficiently blanched by this process.
Fertilizer Requirements: Since leek plants have more vigorous growth, nutrient requirement is more than that of the onion plants. It is estimated that leeks require about 200-250 kg Nitrogen, 50 to 100 kg Phosphorus and 150 to 200 kg Potash per hectare.
Nitrogen is applied in three equal doses: at the time of field preparation, as a side dressing during active vegetative growth and as a top dressing when leaves are dried. One-third of nitrogen and full doses of phosphorus and potash are incorporated into the top soil at the time of site/field preparation.
Irrigation: Irrigation frequency depends on climatic conditions, plant requirements and soil moisture level. It is important that soil moisture needs to be kept at optimum level throughout all growth stages of the leek plants. Irrigation needs to be stopped when plant tops start maturing and showing symptoms of wilting.
Weed Control: Regular manual weeding is recommended to keep the plants weed-free during initial stages of plant growth. In addition to this, cultural practices such as crop rotation and choosing weed-free areas for planting may be adopted for weed control.
Disease-Pest Management: Disease-pest management is similar to those of the onion plants. Major diseases are rust, downy mildew, white rot, white tip disease, and purple blotch. Major insect-pests are thrips and onion maggots.
A detailed account of disease-pest management practices for leek plants is given below:
Rust: Rust is a fungal disease caused by Puccinia porri. It affects mature plants during summers. Major symptom is the appearance of the rust-coloured spores on the upper and lower leaf surfaces.Regular spraying of any of the following fungicides such as Cuprous oxide plus rosin soap emulsion, rosin soap with lime-sulphur emulsion, or Bordeaux mixture with cotton seed oil will effectively control this disease.
Downy Mildew: Downy mildew is a fungal disease caused by Peronospora destructor. It is prevalent in areas having high humidity. Main symptom is violet-coloured furry growth on leaf surfaces and seed stems. Regular spraying of any of the following fungicides such as Cuprous oxide plus rosin soap emulsion, rosin soap with lime-sulphur emulsion, or Bordeaux mixture with cotton seed oil will effectively control this disease.
White Rot: White Rot is a soil-borne fungal disease caused by Sclerotium cepivorum which is prevalent in wet, damp soils. Young plants are affected severely and the affected plants wilt and collapse. Normally, a dense white mass of fungal mycelium is present at the roots of the collapsed plants. Major symptoms of this disease are yellowing and dying back of the leaves. This disease may be controlled effectively by planting leeks in fresh soils where no member of onion family has been grown previously and by adopting proper field sanitation measures.
White Tip Disease: White Tip disease is a fungal disease caused by Phytophthora porri. This fungus develops and spread in low lying areas where soil drainage is poor. This fungal infestation is normally seen soon after heavy rain falls. Affected plants develop a water-soaked appearance at the leaf margins near the leaf tip. This disease may effectively be controlled by providing proper soil drainage in the growing fields and through adopting proper field sanitation measures such as burning the contaminated crop residues.
Purple Blotch: Purple blotch is another fungal disease that affects leek plants. This is caused by Alternaria porri and the disease affects leaves, seed stems, and lower portions of the plants. The disease begins as small, whitish sunken lesions with purple centres that rapidly enlarge affecting the whole leaves and stems. Eventually, the affected leaves and seed stems fall down from the point of attack and die. Spraying of Bordeaux mixture and proper field sanitation will provide maximum control of this disease.
Onion Thrips: Onion thrips (Thrip tabaci) are found to infest leek plants in the fields. These are very small, yellow-coloured sucking insects that affect leek plants and other members of the onion family. Silvery-white mottled lesions or blotches appear on the leaves of the affected plants. Eventually, leaf tips turn brown and die. Repeated dusting or spraying with any of the biopesticides such as pyrethrums or chemical sprays with a recommended insecticide can control the insects effectively.
Onion Maggots: Onion Maggots (Hylemya antiqua) are the larvae of a grey flies which lay eggs in the soil near the plant base. Eggs hatch in one week and maggots crawl upwards towards the leaves and stems of the plants eating the tender parts of the plants along the way. Spraying the soil around the plant base with a 4:4:50 Bordeaux mixture containing 2% lubricating oil emulsion will control the maggots effectively. Spraying should be repeated every week or every ten days.
Harvesting and Yield: Leek plants will be ready for harvest 120-180 days after sowing seeds. Leaf stalks will be about an inch in diameter at this stage. Individual leek plants are pulled from the soil carefully without causing any injuries to the lower portion of the plants. Soil is cleaned off and outer leaves are removed in the packing sheds. After that roots and leaves are trimmed and entire produce is rinsed with spraying water. A harvest of 15-30 tons/ha can be harvested under good crop management conditions.
Packing and Storage: Fresh green tops and well-blanched stems are considered as top quality. Wilted tops, yellowing of tops, bruised tops, crooked stems and bulbous bases are considered as poor quality. Clean, fresh, trimmed leaf stalks of top quality are packed in carton boxes for marketing purposes. Market prefers leaf stalks that are uniform within the bunch and uniform bunches throughout the box. Hence standard packaging practice is packing of 3 uniform sized stalks per bunch and 12 bunches per box. Market prefers big, fresh leaf stalks than small leaf stalks and therefore bigger leaf stalks are in great demand across the markets. Leeks may be stored for 2-4 months at 1-3°C at a high humidity of 95%.
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