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Growing spinach in nft syatem PDF Print E-mail
Written by Administrator   
Tuesday, 18 October 2016 11:39

Growing spinach in nft syatem

 

 

The preferred system is NFT. [Nutrient film technique]. But there are also varieties of

media bed and part media systems that produce excellent results and the raft system.

The NFT system.

(Either fixed bench system, or sliding gully system.)

The NFT system uses either fixed Growing benches 18 meters long by 8 gullies wide or

sliding gullies inside a structure.

Gullies are made using the 100 x 50 rectangular Hydroponic gully with a flat base, do

not use round pipes, as the true film of nutrient cannot be achieved.

Fixed benches are set up in rows, at a convenient height to work on, and grow plants to

maturity. They may be inside structures or outside with a suitable covering in winter,

e.g. cloche covers or roof only structures with wind break sides, and roll down plastic

sides for winter. This depends on the crop grown and the area climate.

Spinach in warm areas for example would be outside in summer, or inside a structure

with shade cloth cover.

Sliding gully systems are usually inside a structure, and have gullies custom

manufactured to fit the structure size. More plants per square meter can be fitted into

this area compared to the fixed benches.

For both systems seeds are germinated in a sterile media such as 25 x 25 x 40 Rockwool

blocks, or in grow pots, again in a sterile media, such as Perlite, Vermiculite, Sterile

Pumice or mixtures of these. Flood & drain trays are usually used for propagation, with

horticultural lighting for consistent production year round.

In the fixed bench system seedlings are transferred to a Nursery bench

[18 meters long and 12 gullies wide] as soon as the roots are large enough to sit on the

gully base. Young plants are grown on in these Nursery benches until the roots or the

tops of the plants are touching, at this stage they are transferred to the final Growing

benches.

A ratio of 1 Nursery bench to 9 Growing benches is ideal.

Holes in the Nursery bench are drilled in a zigzag pattern to house as many plants as

possible, while in the Growing benches they are spaced; 250mm to 280mm apart for

Spinach . A hole sized to suit the chosen pot or media, e.g. Grow pots require 48 to

50mm holes, the same size also suits Rockwool cubes.

Growing benches hold from 450 to 525 plants depending on the hole spacing. The

Nursery bench holds several thousand, the more the better.

Benches should have a fall of 1 in 40 down the gullies, e.g. the top is 450mm higher

than the bottom of an 18 meter long gully.

The flow of nutrient is set at 1 liter per minute per gully.

For sliding gully systems, the seedlings from propagation are placed into the gullies at

one end of the system, and progress down the system, moved manually each time

plants are harvested, until they reach full size.

Feed and return pipes are sized according to the number of benches and flow rate

required.

Tank and pump size are also determined by the number of benches or sliding gullies and

head required to reach to the highest point.

NFT systems require nutrient to circulate 24 hours per day.

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Propagation to end product.

1/. Seed germination in the propagation stage takes 12 to 20 days depending on climatic

conditions. In winter the seed is planted, watered and placed on a hot pad to encourage

germination and root growth. Once germinated they must not dry out at any stage of

growth [if they dry out at any stage, dispose of the plants and start a fresh batch, as

they will never be top quality plants and will produce flower well before they are ready to

harvest] Timed flood & drain systems are best for this stage.

The seeds only require water to grow to the two leaf stage, and then require a nutrient

solution at 3 to 5 CF.

2/.  When seedlings are transferred to the Nursery bench or sliding gullies they should be

sprayed if necessary for insects [aphids in particular] and any possible fungal problems.

The Nursery bench is fed with the same nutrients as the Growing bench.

CF 10 to 18 according to local air temperatures and the time of year. [The hotter the air

temperature the lower the CF.]

A pH of 6.0 to 6.5 should be maintained at all times, ideally 6.3.

The Nursery stage takes 7 to 21 days according to time of year.

3/.  Plants are transferred to the Growing benches and may receive an additional insect

and fungal spray if necessary.

Time to maturity varies with temperature, and time of year, but ranges between 21 to

60 days.

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Nutrients and pH correctors.

Use a Spinach formula mix. Spinach has its own special mix.

Nutrient formula mixes can be blended to suit your water supply. A copy of your water

analysis or a sample of water for analysis is necessary for these customised mixes to be

designed for you.

pH correction is made to maintain a pH of 6.3

(6.0 to 6.5 is the optimum range)

To raise the pH; Use Potassium Hydroxide.

This product is purchased as a strong solution or in powder form and requires diluting

with water, do not use at full strength as the nutrients can be destroyed by precipitation,

and the crop could be damaged.

Potassium Silicate can also be used to raise pH if extra Silicon is needed for natural

fungal protection.

To lower the pH;

Use Phosphoric and/or Nitric acids. The ratio required depends on the pH of the base

water, and will be advised. In many cases a 50 / 50 mix is used.

Again do not use at full strength. Dilute acids 500 to 1 with water.

?

Medias and equipment.

Suitable Medias for pots and plug production include;

Sterile pumice. 1 to 5mm in size.

60% Perlite [super course] mixed with 40% vermiculite [medium].

Sterile potting mix (used with care).

Course washed river sand.

Suitable pre-made blocks include;

Rockwool blocks. 25mm x 25mm x 40mm cubes are ideal for Spinach.

Grow pots;

Available in reusable (white) or disposable (green) types.

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Test and control equipment.

It is advisable to have a fully automatic nutrient dosing system to control the pH and CF

for Spinach if there are more than 10 benches in the system.

Nutrient heating is advised in the winter months if temperatures of the nutrient fall

below 14 degrees C. Spinach grows well at 14 to 24 degrees C but does not like

temperatures over 32 degrees C, going to seed/flower very quickly.

Where Spinach is grown under protective structures, good air flow is essential for

healthy plants, and temperatures over 30 degrees C must be avoided where possible.

Evaporative mist cooling systems can be employed if high temperatures are a problem.

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Seed varieties.

The seed suppliers should be able to supply samples of different varieties, test these to

see if they are suitable for your growing conditions, and market requirements

ppm Mineral levels for specific CF ranges for Spinach

MINERAL

CF 10

CF 12

CF18

NITROGEN

33-100

40-120

60-180

PHOSPHOROUS

8-25

10-30

15-45

POTASSIUM

50-150

60-180

90-270

SULPHUR

13-40

16-48

24-72

CALCIUM

33-118

40-142

60-210

MAGNESIUM

8-25

10-30

15-45

SODIUM

3-35

3-35

3-35

CHLORIDE

3-35

3-35

3-35

IRON

0.7-3.6

0.8-3.6

1.2-5.0

MANGANESE

0.13-1.6

0.16-1.9

0.24-3.0

BORON

0.07-0.5

0.08-0.6

0.12-0.9

ZINC

0.03-1.0

0.04-1.0

0.06-1.0

COPPER

0.03-0.33

0.04-0.36

0.06-0.5

pH RANGE

6.0-6.5

6.0-6.5

6.0-6.5

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Nutritional problems

Regular nutrient analysis and leaf analysis may be required to assist in producing top

yield, especially in the first crop, or crops.

The following are the leaf nutrient results required for a healthy crop.

Nitrogen

4.2 to 5.2 %

Phosphorous

0.48 to 0.58%

Potassium

3.5 to 5.3%

Calcium

0.6 to 1.2%

Magnesium

1.6 to 1.8%

Sulphur

0.3 to 0.8%

Iron

220 to 245 ppm

Manganese

50 to 85 ppm

Boron

42 to 63 ppm

Copper

45 to 65 ppm

Zinc

50 to 75 ppm

With NFT systems it is often advantageous to flush out the nutrient tank regularly to

avoid a build up in toxic materials or to remove a nutritional mineral imbalance. Also if

the nutrient gets dirty and you don't fancy drinking it, then flush it out. Plants respond

to clean nutrient and there will be far less problems from disease if nutrient is regularly

changed. Only nutrient analysis will show how long a specific system can run for until it’s

out of balance; however 4 weeks is usually the maximum time between flushing.

Remember, don't put cold water into the tank and circulate immediately,.

Last Updated on Friday, 30 December 2016 13:29
 

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