Abu Dhabi Farmers' Service Centre – open-field vegetable production guide

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Growing cabbage for profit and sustainability 2014-2015 Season Guidelines

Introduction Cabbage (Brassica oleraceae) is a biennial plant belonging to the Cruciferae family. They are popular traditional vegetables in the UAE with several varieties grown for the local markets. The types favored by supermarkets are red, green or white fully round shaped cabbage. Flat varieties tend to go to wholesalers. Careful selection of varieties, adoption of appropriate technology and good management of cabbage crops throughout the production cycle allow growers to maximize profits. This guide outlines the key practices essential for producing high yields of good quality cabbages under UAE growing conditions over the growing season to meet market demands. Growing season Sowing: September to mid-January Transplanting: October to mid-February Harvest period: December to mid-May Table 1: Cabbage growing season

Month Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun

Sowing

Transplanting

Harvest

Growing period Nursery sowing to transplant: 4 weeks Transplant to harvest: 10 weeks Total crop cycle: 14 – 16 weeks Table 2: Cabbage growing period

Week 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Stage S T H H H

Key to colours and symbols: S Sowing T Transplanting H Harvesting

Varieties Varietal selection is important for the success of your crop. Varieties selected should suit local climatic conditions, have good pest and disease resistance and meet market needs. The green round and white round varieties attract the best market prices in the UAE. Communicate with your marketer and seed supplier to determine the most suitable variety for UAE growing conditions and that gives you best returns.

Irrigation layout, plant density and expected yield

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In Abu Dhabi cabbages have traditionally been planted with a between row plant spacing of 90 cm resulting in a per donum plant density of 4,400 with a typical yield of 5,000 kg (Table 3). Yield can be increased to 9,000 kg using new pressure compensated inline drip irrigation systems and higher plant density. Using the high density planting arrangement, cabbage seedlings should be planted in 40 cm rows and within row plant spacing of 40 cm. Table 3: Plant arrangement and density

Plant arrangement

Plant spacing Drip line spacing

Layout detail

Plant density

Be-tween rows (cm)

Within rows (cm)

Be-tween lines (cm)

Within lines (cm)

Number of plants/ donum

Poten-tial mar-ketable yield (kg/ donum)

Recommended High density planting

40 40 40 40

Beds of 2 rows x 40 cm spacing with

pathway of 60 cm between

beds

5,000 9,000

Not recommended Traditional planting

90 50 90 50 Cluster of 2 plants per

dripper 4,400 5,000

Figure1: Correct spacing for high density cabbage

Figure2: As the crop matures full ground cover is achieved

improving water use efficiency

Soil analysis and water quality requirements Cabbages are moderately sensitive to soil salinity. At the nursery stage and soon after transplanting, it is recommended that irrigation water should not exceed 1.2 dS/m (1,150 ppm). Prior to field preparation, soil and water samples should be taken and sent for analysis. Once plants are fully established, a water salinity of up to 1.9 dS/m (1,220 ppm) can be used to grow the crop provided leaching requirements are strictly followed. Irrigation water salinity levels higher than 4.6 dS/m (3,000 ppm) will severely restrict growth and a 50% yield loss can be expected. Under salt stress, cabbage heads are generally more compact, and leaves are fleshier than under nonsaline conditions. Your local ADFSC extension engineer can assist you with soil and water sampling techniques and help interpret results from the lab to grow the crop successfully. Land preparation and pre-planting fertilising Thoroughly cultivate the area to be planted four weeks prior to transplanting. Apply pre-planting fertiliser and well composted manure

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in a 30cm wide band along each drip line and mix thoroughly into the top 10cm to 15cm of the soil along this band. The fertilisers that should be incorporated into the soil at least two weeks prior to transplanting are shown in Table 4 below. Table 4: Pre-planting fertilisers

Pre-plant Composted manure (kg/donum) Triple super phosphate

(kg/donum)

Total application 2,500 50

Pre and post-plant fertiliser applications provided are only a guideline. Fertiliser recommendations should be based on soil and irrigation water analyses and experience of soil conditions in your local area. Contact your ADFSC extension engineer for assistance with testing water and soil on your farm and formulating a fertiliser program. Cabbage benefit from high levels of organic matter. The composted manure provides organic matter to the soil to help with retention of irrigation water and nutrients for a strong healthy root system. Organic material must be thoroughly composted to avoid introducing weed seeds, pests, diseases and causing seedling root burn from high temperatures produced during the composting process. Installation of new irrigation lines Existing irrigation systems can be adapted to the new layout by attaching new drip lines at the required spacing to the existing underground sub-mains or lateral water pipes. Existing outlets that do not align with the new spacing should be blocked off. In some situations farmers may choose to install new sub-mains or lateral pipes to facilitate the new drip line layout. Always test the irrigation system and dripper prior to transplanting to ensure all drippers are working properly. This is ideally done as part of the pre-planting weed control. Cabbage nursery Sowing cabbages in a well-managed field nursery has the following advantages over direct sowing in the field:

A more favourable and even germination

A protected location on the farm under Agrile row cover provides a good seedling environment and minimises the risk of virus infections through whitefly infestations

Improved irrigation control and crop monitoring during the sensitive germination and seedling stage

Minimised irrigation water use and salt accumulation in the field for the nursery period between 3 and 4 weeks. This effectively reduces irrigation water consumption, potential salt build-up and the leaching of nutrients from the root zone

Selection of strong evenly sized seedlings for transplanting and good production Cabbage nursery requirements are given in Table 5 as follows:

Abu Dhabi Farmers' Service Centre – open-field vegetable production guide

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Table 5: Cabbage nursery planting and seed requirements

Crop Recom-

mended sow-ing method

Sowing depth (mm)

Number of plants/donum

Seed requirements

Number of seeds/g

Number of g/ donum (with 20% additional allowance for germi-nation and replace-

ments)

In recom-mended spacing

In tradi-tional spac-

ing

Recom-mended

plant spacing

Tradi-tional plant

spacing

Cabbage Nursery 5 to 10 5,000 4,400 280 to 380 16 to 22 14 to 19

Cabbage seedlings can be produced in the ground in nursery beds, in flat-cell trays or in Jiffy pots. Potting mix should be preferably mixed with water before packing the mix into the trays or Jiffy pots. When seeds are started in cell trays, a good commercial potting mix should be used to improve water and nutrient availability, provide correct aeration and minimise pests and diseases. In the field, cabbage nurseries can be established using a good potting mix that provides appropriate soil conditioning. An Agrile row cover should be used to protect seeds from excessive surface temperatures and disease carrying insects. Good aeration, temperatures not exceeding 30⁰C and adequate moisture are necessary to encourage rapid even germination of seeds and growth of seedlings. Over watering will result in seed death from lack of oxygen leading to poor germination and should be avoided. Production of cabbage seedlings in ground nurseries is generally not recommended as bare root transplants are slow to establish in the field, lead to higher seedling mortality and reduce yield. Moreover, it is difficult to maintain a root ball during the digging out process as the soil is light and friable resulting in bare root seedlings for transplanting. The nursery should be observed twice daily to make sure that optimum conditions are maintained during the germination and seedling development. Soon after emergence, the seedling should be exposed to adequate sunlight to support good strong growth. Early detection of problems allows a rapid response when extra water, nutrient or pesticide applications may be required. Seedlings are ready for transplanting in approximately 4 weeks after sowing. Seedlings can be hardened to better prepare them for transplanting, as follows:

Stop fertiliser applications seven days before transplanting.

Reduce irrigation to stress the seedlings two days before transplanting.

Resume normal irrigation the day before transplanting.

Transplant the seedlings in the cooler part of the morning or evening.

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Figure3: White cabbage seedlings under Agrile cover

Figure4: Red cabbage seedlings

It is important to minimise stress on the seedlings by keeping them out of direct sunlight and not letting them dry out. ADFSC extension engineers can provide advice about the best approach for nurseries on your farm.

Growing stage Transplanting Cabbage seedlings are transplanted into prepared rows at 40cm spacing between plants within the rows. Whether seedlings to be transplanted are lifted from the nursery bed, from seedling trays or Jiffy pots it is important that the roots are not disturbed and the soil surrounding the roots maintained. Bare root transplants are discouraged as they will take longer to establish in the field. Management of the young plants is easier than with bare-rooted seedlings. Crop nutrition and application of soluble fertilisers through irrigation (fertigation) Weekly or more frequent fertigation is recommended according to the following schedule: Table 6: Recommended weekly rates for fertigation fertiliser (kg/donum) and trace element application for UAE sands

Growth stages in weeks after trans-

planting

Ammonium sulphate

Potassium nitrate

Magnesium sulphate

Trace element mix Chelated Fe

(EDDHA)

Week 1 3.0 - 0.2 0.2

Week 2 3.0 3.0 0.5 0.2 0.2

Week 3 3.0 3.0 1.0 0.2 0.2

Week 4 4.0 3.0 1.0 0.2 0.2

Week 5 7.0 5.0 1.0 0.2 0.2

Week 6 7.0 5.0 1.0 0.2 0.2

Week 7 7.0 5.0 1.0 0.2 0.2

Week 8 7.0 5.0 0.5 0.2 0.2

Week 9 7.0 5.0 - 0.2 0.2

Week 10 2.0 1.0 -

Total 50.0 35.0 6.0 2.0 2.0

Notes on fertigation

1. Fertigation should begin on the first week after transplanting

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2. Depending on the soil and water analyses it may be necessary to supply other chelated trace elements. 3. Continue irrigation for 5 minutes after fertigation to flush the system. 4. More frequent fertigation can be adopted and the fertiliser dosage should be adjusted accordingly

The above schedule of weekly applications (Table 6) is only a guideline for the sandy soils typically found on Abu Dhabi farms. The exact fertiliser recommendations should be based on soil fertility levels and irrigation water conditions in your area. Contact your ADFSC extension engineer for assistance with testing water and soil on your farm. Weekly or more frequent fertigation ensures that nutrient levels are maintained in the root zone of the crop throughout the important growing and production periods. These recommendations are based on good irrigation practices. Excessive irrigation will leach nutrients away from the root zone. Crop water requirements Young cabbage transplants or seedlings have a lower water requirement. However, water requirement increases rapidly as complete canopy cover and head development occurs. Irrigation must be closely monitored to ensure soil moisture remains even in the beds during the cropping period. It is particularly important in the days following transplanting when seedlings are establishing new root systems. Excessive irrigation promotes root rot and results in leaching of nutrients away from the root zone. Supplying water in equal amounts throughout the season prevents cracking of the heads. Application of soluble fertiliser as fertigation can be carried out during a normal irrigation. Continue irrigation for 5 minutes after fertigation to flush the system. Plant protection Many pest and disease problems can be avoided through Integrated Pest Management (IPM) procedures. The following will help to ensure any pests and diseases in your cabbage crop remain below the economic threshold and swift action is taken should they become a problem. Use of pest resistant varieties This ensures your crop has natural resistance to pests and diseases, minimising the need for expensive chemical control. Row covering These should be put up immediately after transplanting and left up for 10 – 15 days. They protect your crop from numerous insect pests, such as caterpillars, aphids, leafhoppers, leaf miners, beetles and white-flies. Crop rotation Do not plant cabbage more than once every 3 – 4 years in the same field. This will minimise the risk of fungal and bacterial diseases

Figure5: Achieving full ground cover with high density

red cabbage

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such as bacterial black rot and fungal diseases such as downy mildew, powdery mildew, white rot and damping off. Soil solarisation This should be carried out each summer prior to planting to help control soil borne pathogens, soil insects, weeds and root-knot nematodes. Companion crops Planting corn and squash as a trap crop around the borders of your cabbage crop keeps aphids away, reducing the incidence of turnip mosaic virus. Traps Placing yellow and blue sticky traps and pheromone traps around your cabbage crop will help control whitefly, leaf miners and caterpillars. Removing and correctly destroying all crop residues immediately after harvest This helps prevent last season’s pests re-infecting your new crop and will help to control fungal and bacterial diseases, caterpillars, aphids and beetles. Good weed management Irrigate the beds prior to transplanting to stimulate germination of weed seeds. Remove all weeds prior to transplanting. Following planting, the field should be monitored regularly and kept free of weeds. Remove weeds by hand at early growth stages of cabbage and before canopy covers over. Crop monitoring Cabbage crops should be monitored for pests and diseases every week. This is especially important during the early stages of growth when cabbages are susceptible to pests and diseases. Consistent monitoring enables a swift and effective response should an outbreak occur, which will minimise crop damage and expense. Thorough composting of all organic matter All manure put on the crop should be thoroughly composted to prevent pest and disease outbreaks. In the event of a pest or disease outbreak please contact your nearest ADFSC extension engineer to correctly identify the pest or disease and provide recommended control measures.

Harvest stage Pre-harvest interval (PHI) Pre-harvest interval is the time between the last pesticide application and harvests of the treated crop. The PHI must be adhered to for all crops. Failure to adhere to the PHI will result in pesticide residues in the harvested produce, which will render the crop unfit for human consumption and for sale. It is illegal to sell crops where the PHI has not been adhered to. For further advice on harvest intervals please contact your local ADFSC extension engineer. Field Hygiene during harvest Good field hygiene is required to ensure your crop is free of contaminants. This is essential for it to be sold in the market. Good field hygiene practices must always be adhered to when harvesting fresh vegetables. Crop maturity, handling and storage Cabbages should be harvested during the cooler parts of the day to avoid heat and sun damage. To ensure best prices, the base should be neatly trimmed with a clean, sharp instrument to prevent from tearing and rotting. Cutting blades should be regularly cleaned to prevent the spread of disease. For field packed cabbages, the leaves should be stripped away to present a neat and clean product with the shape typical of the variety. For best prices, consult the most recent marketing specifications available from the ADFSC for size requirements. Smaller size cabbages can be more profitable than larger sized ones.

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Cabbages are prone to damage which reduces shelf-life and saleability of the product. They must be handled with care and never be thrown or dropped. Harvested cabbage should be moved from the field to a cool shaded location for short term storage. They must never be left exposed to direct sun. This is especially important during late season harvesting when air temperatures and intensity of the midday sun will dramatically reduce quality. Cabbages should be free from mechanical damage and be of uniform shape and size in each tray. Cabbages should be packed carefully to reduce risk of damage in transit. Crates must be stacked safely and securely so they are not resting on the produce beneath. Grading To ensure cabbages receive the best price, they must be graded according to the current ADFSC specifications. These can be obtained from your local procurement officer.

For further information and advice: Contact your local ADFSC office for professional advice from our experienced team of extension engineers.

Figure6: White cabbage ready for harvest

Figure7: Red cabbage ready for harvest