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From NJ Commercial Vegetable Production Recommendations
Many pre-mixed growing media products suitable for conventional and organic production are available commercially. A good, lightweight, disease-free, plant-growing material can also be made from a mixture of peat and vermiculite. A formula for a very simple mix for conventional production is given in Table R-4, but a preferred formulation is shown in Table R-5. If plants are to be grown in a mix longer than 8 weeks, use the formula in Table R-5. Organic growing media differ from conventional media because all components used must be allowable under organic production standards. When mixing your own formulation it is important to verify with your certifier that the materials you are using will not compromise your certification. For more information on organic growing media including several formulations can be found in:
Table R-4: Simple Plant-Growing Mix
| Materials | Cubic Yard (22 Bushels) | 2 Bushels |
| Shredded sphagnum peat moss | 11bu | 1bu (10gal) |
| No. 2, 3, or 4 domestic or African vermiculite1 or horticultural grade (dust-screened) | 11bu | 1bu (10gal) |
| Pulverized limestone: dolomitic lime for mixes made with domestic vermiculite or calcitic lime mixes made with African vermiculite | – 10lb 6lb | – 1lb 9oz(3/4c) |
| Superphosphate (20% P2O5) or Triple superphosphate (46% P2O5) | 2½lb 1¼lb | 4oz (½c) 2oz (¼c) |
| Fertilizer (5-10-10) | 5lb | 8oz (1c) |
1 Vermiculite should be pea-sized and relatively free of fines and dust. Final mix should have a pH of 6.0-6.5
Notes. Good results for growing lettuce and cabbage transplants have been obtained by diluting this mix with an equal part of sand.
This mix will only get the seedlings up. Supplemental fertilizing will be needed to grow plants to transplant size. About 3 weeks after seeding, begin liquid fertilizing the plants with a soluble fertilizer, such as a 20-20-20, at the rate of 2-3 teaspoons per gallon of water. This rate should be applied at least weekly. More frequent applications may be desirable.
Table R-5: Preferred Plant-Growing Mix
| Materials | Cubic Yard (22 Bushels) | 2 Bushels |
| Shredded sphagnum peat moss | 11bu | 1bu (10gal) |
| No. 2, 3, or 4 domestic or African vermiculite1 or horticultural grade (dust-screened) | 11bu | 1bu (10gal) |
| Pulverized limestone: dolomitic lime for mixes made with domestic vermiculite or calcitic lime mixes made with African vermiculite | – 10lb 6lb | – 1lb 9oz(3/4c) |
| Superphosphate (20% P2O5) or Triple superphosphate (46% P2O5) | 2½lb 1¼lb | 4oz (½c) 2oz (¼c) |
| Sulfate or muriate of potash (50%-60% K2O) | ½lb | 1oz (2tbs) |
| Osmocote2 (18-6-12) Tomatoes Eggplants Peppers | – 4lb 8lb 8lb | – 6oz (3/4c) 12oz (1½c) 12oz (1½c) |
| Micronutrient mix | Use according to mfgr’s recommendations. | |
| Wetting agent (such as Aqua-Gro granular) | 1½pt | 1oz (4tbs) |
1 Vermiculite should be pea-sized and relatively free of fines and dust. Final mix should have a pH of 6.0-6.5
2 Osmocote is a slow-release fertilizer. Use a formula that will release nutrients over a period of 8 to 9 months. Therefore, mixes should be made just prior to seeding. Plants grown in mixes containing Osmocote must be carefully watered and the temperature carefully controlled prior to field planting. Reduced rates are suggested to control plant height when using small cells.
Regardless of which formula is chosen, unless good mixing procedures are used, the results will be less than optimal. For best mixing, use a horizontal-type paddle mixer that folds or blends the components, such as lime and fertilizer, evenly throughout the mix. With tilted or other types of mixers, the components tend to segregate or separate out, resulting in erratic performance of the mix.
Good procedures to follow when preparing a mix are:
- Use a respirator to prevent inhalation of dust when mixing peat, vermiculite and additives.
- For small quantities of mix preparation–1 cubic yard or less–place 4 to 5 inches of vermiculite in the bottom of a 5-gallon pail.
- Add all the additives (lime, fertilizer, micronutrient, etc.) to the vermiculite in the pail and mix thoroughly.
- Fluff the recommended amount of peat. Start mixer and begin blending the peat.
- While blending, add water according to the dampness of the peat. You will need approximately 1 gallon of water per bushel of peat in the mix.
- While blending, slowly pour the additives, which you have already mixed thoroughly with a small amount of vermiculite, into the mixer and blend for 3 to 5 minutes.
- Add the recommended amount of vermiculite after the other ingredients and blend for 1 minute or less, depending on the consistency of the vermiculite. It should be mixed thoroughly without breaking down. Soon after mixing, use the mix for growing your plants. It is not a good practice to stockpile the mix in large piles for long periods of time.
- Read all labels of the ingredients used, and heed all warnings that may be marked on the labels or bags.