Cropping in sawdust

In the 1950s and 1960s the Saanichton and Agassiz research stations developed a method of cropping greenhouse tomatoes in sawdust. This method received general commercial acceptance in British Columbia, and to some extent in Alberta, in the 1970s and 1980s, but it is now being replaced by rockwool. Some of the advantages of sawdust culture are its low cost, light weight, and the wide availability of sawdust itself. Although rockwool also claims some of these qualities, sawdust could again receive renewed attention because it is easier to dispose of than rockwool.

The sawdust used as a growing medium in the past was derived from Douglas-fir and western hemlock. Sawdust from western red cedar was found to be toxic, especially when fresh, and therefore should not be used. Other organic or inorganic media can be mixed with sawdust to improve the chemical and physical properties of the substrate. However, the various

Table 16 Fertigation schedule for tomato production in peat bags (in kilograms of fertilizer per 1000 L of stock solution)

Iron

Week from

Calcium

Potassium

Ammonium

10-52-10

chelate

Monoammonium

Magnesium

EC

planting

nitrate

nitrate

nitrate

Starter

(13% Fe) phosphate

sulfate

L/day

()j.S/cm)

1,2

0

0

0

40.0

0.0

0

0

0.4

5000

3,4

0

0

0

40.0

0.0

0

0

0.2

4000

5,6

0

90.0

0

0.0

0.0

20.0

9.0

0.4

3500

7,8

18.0

90.0

0

0.0

0.0

20.0

9.0

0.6

3000

9, 10

18.0

90.0

0

0.0

0.0

40.0

9.0

0.8

2500

11, 12

18.0

90.0

0

0.0

4.0

40.0

9.0

1.0

2300

13, 14

18.0

90.0

50.0

0.0

4.0

40.0

9.0

1.2

2200

15-18

36.0

90.0

50.0

0.0

4.0

40.0

18.0

1.4

2000

19-22

36.0

90.0

50.0

0.0

4.0

40.0

18.0

1.4

2000

23

36.0

90.0

50.0

0.0

4.0

40.0

0

1.4

1500

24, 25

0

90.0

50.0

0.0

4.0

40.0

0

1.4

1500

  • Trace elements (e.g. 0.5 kg of STEM) must, also be added to all the above fertilizer feeds; a typical trace element mix, e.g. Peters soluble trace element, mix (STEM) contains 1.45% baron, 3.2% copper, 7.5% iron, 8.15% manganese, 0.046% molybdenum, and 4.5% zinc.
  • Dissolve given amount of each fertilizer, including trace elements, in 1000 L of water and add to the irrigation water in equal doses, ideally with a multihead fertilizer injector. Start, injection at a very low rate and increase progressively until the desired EC is achieved. Adjust thepH of the fertilizer solution to 5.5 by injecting a dilute solution of phosphoric, nitric, or sulfuric acid.
  • For a spring crop use the schedule unchanged; for a fall crop follow the schedule but start from week 4.
  • The recommended strength of the stock solutions is within the working range of a fertilizer injector with a 1:100 mixing ratio. If a fertilizer injector with a 1:200 mixingratio is used, double the amount of each fertilizer. Similar adjustments can be made for fertilizer injectors with other mixing ratios.

substrate mixtures must be formulated and tested on a small scale under well-controlled conditions. The uncontrolled distribution of a wide variety of organic media mixtures with diverse chemical and physical characteristics is a major source of grower confusion and therefore an obstacle in the profitable use of this valuable Canadian resource.

Sawdust can be placed in troughs, beds, upright bags, bolsters, or even large pots. Regardless of the container, a minimum of 10 L of medium is recommended for each plant. The culture practices followed in sawdust culture are similar to those described for peat moss.

Fertilizer can be applied in two ways: all nutrients, with complete nutrient solution, can be supplied at each irrigation; or, some of the fertilizer can be incorporated into the growth medium before planting and the remainder can be delivered through the irrigation system.

The fertilizer rates described in Table 17 are recommended for tomato production in unfertilized sawdust.

The fertilizer rates described in Table 18 are recommended for tomato production in sawdust enriched with 2.4 kg of superphosphate (0-19-0) and 4 kg of domolitic limestone per cubic metre of sawdust. To ensure the long-term availability of calcium and magnesium, supply half the limestone as a coarse grind and half as a fine grind.

Table 17 Fertilizer application rates for tomato production in unfertilized sawdust

Nitrogen level in final solution Fertilizer N at 126 ppm N at 168 ppm N at 210 ppm

Amount of fertilizer in final solution (g/1000L)

Potassium sulfate

360

44

_

Potassium nitrate

160

500

550

Magnesium sulfate

500

500

500

Ammonium nitrate

-

_

100

Calcium nitrate

680

680

680

Stock solution (mL)

Trace element, stock*

220

220

220

Phosphoric acid (75%) f

100

100

100

  • The trace element stock solution is prepared by dissolvingthe following elements in 1 L of warm water: 70 g iron chelate (10% iron), 15 g manganese sulfate, 12 g boric acid, 2.2 g zinc sulfate, 0.6 copper sulfate, and 0.2 g molybdic acid. When this trace element stock solution is added to the final nutrient solution at a rate of 220 mL/L, the concentration of trace elements in the final nutrient solution, in parts per million, is as follows: iron 1.54, manganese 1.07, boron 0.46, zinc 0.11, copper 0.034, and molybdenum 0.023. f Concentrated phosphoric acid (75%) can be carefully added directly to the final nutrient solution without, prior dilution.
  • The trace element stock solution is prepared by dissolvingthe following elements in 1 L of warm water: 70 g iron chelate (10% iron), 15 g manganese sulfate, 12 g boric acid, 2.2 g zinc sulfate, 0.6 copper sulfate, and 0.2 g molybdic acid. When this trace element stock solution is added to the final nutrient solution at a rate of 220 mL/L, the concentration of trace elements in the final nutrient solution, in parts per million, is as follows: iron 1.54, manganese 1.07, boron 0.46, zinc 0.11, copper 0.034, and molybdenum 0.023. f Concentrated phosphoric acid (75%) can be carefully added directly to the final nutrient solution without, prior dilution.

Table 18 Fertilizer application rates for tomato production in fertilizer-amended sawdust

Nitrogen level

Table 18 Fertilizer application rates for tomato production in fertilizer-amended sawdust

Nitrogen level

Fertilizer

N at 126 ppm N at 168 ppm N at 210 ppm

Amount of fertilizer in final solution (g/1000L)

Potassium nitrate

550

550 550

Ammonium nitrate

160

280 410

Stock solution (mL)

Trace element stock*

220

220 220

Phosphoric acid (75%) t

100

100 100

  • The trace element stock solution is prepared by dissolving the following elements in 1 L of warm water: 70 g iron chelate (10% iron), 15 g manganese sulfate, 12 g boric acid, 2.2 g zinc sulfate, 0.6 copper sulfate, and 0.2 g molybdic acid. When this trace element stock solution is added to the final nutrient solution at a rate of 220 mL/L, the concentration of trace elements in the final nutrient solution, in parts per million, is as follows: iron 1.54, manganese 1.07, boron 0.46, zinc 0.11, copper 0.034, and molybdenum 0.023. t Concentrated phosphoric acid (75%) can be carefully added directly to the final nutrient solution without prior dilution.
  • The trace element stock solution is prepared by dissolving the following elements in 1 L of warm water: 70 g iron chelate (10% iron), 15 g manganese sulfate, 12 g boric acid, 2.2 g zinc sulfate, 0.6 copper sulfate, and 0.2 g molybdic acid. When this trace element stock solution is added to the final nutrient solution at a rate of 220 mL/L, the concentration of trace elements in the final nutrient solution, in parts per million, is as follows: iron 1.54, manganese 1.07, boron 0.46, zinc 0.11, copper 0.034, and molybdenum 0.023. t Concentrated phosphoric acid (75%) can be carefully added directly to the final nutrient solution without prior dilution.

In Tables 17 and 18 the recommendations for applying fertilizer can be implemented either by dissolving the fertilizers at the prescribed rates in water and directly applying the resulting nutrient solution to the crop or by preparing concentrated stock solutions (e.g., 100 times the prescribed rates) and incorporating the stock solutions into the irrigation water (i.e., by using a fertilizer injector with a 1:100 mixing ratio). Always remember that calcium and sulfates cannot be mixed together at high concentrations without some precipitation of calcium sulfate, and therefore at least two stock solutions must be prepared.

How To Can Tangy Tomatoes

How To Can Tangy Tomatoes

Interested In Canning Juicy Tomatoes? Here's How You Can Prepare Canned Tomatoes At Home. A Comprehensive Guide On Tomato Canning. The process of canning tomatoes at home has been a family tradition with many generations. Making home canned or home tinned tomatoes is something that is remembered by families for years! You must have surely seen your granny canning tomatoes at home in order to prepare for the approaching winters. In winters, one is usually unsure of getting fresh tomatoes.

Get My Free Ebook


Post a comment