Broccoli - Planting and Fertilizer application


This mostly applies to those who do irrigation production. Compacted soils restrict root growth, reduce the amount of oxygen available to roots, and limit water penetration, all of which can reduce yield potential. Work beds to 150-175 mm deep to promote good rooting. Raised beds are an alternative to conventional field planting as they improve soil drainage and allow access to the crop without causing soil compaction. Raised beds are typically 1.2-1.5 m wide and 27 m long. The width is determined by the type of equipment used and by the crop. Leave a 30 cm pathway on either side of each bed to accommodate foot traffic.

Broccoli sprouts should generally be started in greenhouses before the frost-free date depending on the province you are located. This allows sufficient time for growth and hardening before transplanting to the field. Shortly before planting treat seeds in a hot water bath. This is done to prevent black rot, black leg, and damping off diseases. This will kill fungi that can decimate young plants. Sterilise empty transplant trays in a 10% bleach solution. Ten days before transplanting to the field, move plants into a cold frame to harden them. Once Cole crop plants have been sufficiently hardened, they will be able to withstand temperatures as high as 28 oC. You can also purchase transplants commercially which is recommended for those growing the crop for the first time.

For early markets, transplants must be raised in greenhouses. About five to six weeks are required to produce transplants. Plants may be grown in plastic plug trays/plant cells. Broccoli may have two plants per cell in some production systems where large terminal heads are not desired. Normally 300 grams of seed will produce enough plants for one hectare.

Old or large plants of broccoli and those grown at low temperatures (10 to 15 oC) are likely to button (premature head formation) and bolt if exposed to a period of cool weather after field setting. Plant seedlings outside when they are about 15 cm high with 5-6 true leaves. Slight hardening is beneficial, but severe hardening may stunt growth. Hardening is the process whereby transplants are gradually acclimatized to the outdoor environment two weeks before planting.

For late markets, transplants may be raised in plastic plug trays/plant cells, a greenhouse seedbed, or direct-seeded. For greenhouse production, follow the instructions given above. If growing on seedbeds, space rows 25 to 30 cm apart and plant 20 seeds per 25 cm of row with a scatter shoe seeder.

Irrigation

The availability of water is critical for successful broccoli production. Irrigation may also be used to cool plants during periods of high temperature. Fertiliser could be applied through an irrigation system. Irrigation at the wrong time can cause problems such as head rot. Broccoli crops require a regular water supply of about 25 mm every 5 to 7 days during the growing season. Shortage of water is detrimental for head development.

Fertiliser application

Lime should be applied to maintain the soil pH in the range of 6.5 to 7.0, unless club root control is required (pH of 7.2). If soil pH is below is 6.2, apply lime six weeks before planting.

Nitrogen

About 130 to 150 kg/ha of actual nitrogen is required for broccoli. If manure is applied or a legume is ploughed down, the nitrogen application may be reduced. Broadcast 80 kg/ha before planting and work it in. Apply the remainder as two side-dressings at 7 -10 days after planting, and the second 4- 6 weeks later. If the season is very moist, a third side dressing application may be applied three weeks after the second application. Adequate nitrogen produces a dark green colour in broccoli leaves. Leaves of nitrogen-deficient plants are light green eventually turning yellow and may be shed. Excess nitrogen during hot, humid weather will increase the incidence of head rot of broccoli.

Phosphorus

A soil test will determine the level of phosphorus requirements. Broadcast or band any needed
phosphate before planting and disc it in. Phosphorous is important for root growth. A shortage of phosphorous causes stunted growth.

Potassium

A soil test will determine potassium requirements. Excessive potash may lead to increased tip burn (internal and/or external). Potash competes with calcium for uptake from the soil and this is probably what causes the increased tip burn.

Magnesium

Older leaves are the first to show deficiency signs, which include blotches of interveinal chlorosis. As the chlorosis intensifies, purple blotches may be seen near the leaf margins. Deficiency is fairly common especially on light acid soils where dolomite limestone has not been applied. To avoid these problems, apply dolomitic limestone or add limestone or add magnesium to the fertiliser. If the problem occurs during the season spray the foliage with magnesium sulphate.

Sulphur

Early deficiency symptoms appear as blotches of interveinal chlorosis on the youngest leaves, and the leaves may become reflexed. On sandy soils low in organic matter that has been intensively cropped, soil sulphate levels may be low. Application of gypsum should be considered on these soils. Broccoli crops have a high need for sulphur.

The recommended balanced fertiliser for basal application is Compound C (5:15:12) or Compound S (7:21:7). For top dressing, apply ammonium nitrate (34.5% N).
 

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