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Nutrient absorbtion
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Phase Feeding

In order to better serve their customers needs many nutrient manufacturers have developed “feedcharts”. The data they contain is intended to suggest optimal usage of a combination of their products, typically on a week by week basis. Ideally, the grower consults their chart for the particular time period of their crop, determines which of the manufactures products to use, measures the appropriate quantities and applies as directed.

Reputable manufacturers and retailers have based their feeding program on years of experimentation with a variety of crops and growing conditions and through continued feedback from objective and competent growers. In fact some of this experimentation has not only led to modifications in their recommended feeding regimen, but sometimes the products themselves. Growers should be wary of feed schedules which are more concerned with getting you to buy as much of the products listed as possible, instead of suggesting products your crop actually can use in a given stage of growth. For example, how much benefit do you think you may realize by applying two sources of B-1 at the same time?

There are strong and often valid arguments that revolve around the concept that you should stick with one particular manufacturer’s products for the entirety of the crop for compatibility reasons. A proven feeding program can be essential for the success of the novice grower. However, some of the most successful growers are able to “think outside of the chart”, and draw from a broader arsenal of growing products from a variety of manufacturers.

A lot of factors come into play when determining how best to feed your favourite plants. The stage of plant development and the crops chronological age in that phase weighs largely in your considerations of what to feed and in what quantities. However, blindly following the feed program you picked up at the hydro shop isn’t going to necessarily give you the best results. It would be naïve to assume that all grow rooms are the same, therefore growing conditions will vary. As such, so will the extent of your plants’ development within a given time frame. For example, you have completed the rooting/seedling stage, and your chart calls for an increased amount of nutrients in what it deems “week 1” of vegetative growth. Experienced growers have learned from past mistakes that over applications of fertilizer (high in nitrogen), particularly in the early stages of a plant’s development can be disastrous. Also, some strains prefer different levels of nutrition.

So, if you had cooler rooting conditions and the donor plants were older and woodier, there is a greater likelihood that they would not have developed as robustly as younger donor material in warmer conditions (although the same chronological age). As a result, the new plants may not be prepared for the increased levels of nutrition as suggested by the chart you are following.

Now the problem becomes exponential. Growth is retarded due to an over abundance of fertilizer, and the plants fall further behind the lines drawn on the chart. This progresses into “week 2” on your chart, where the formula calls for a yet another increase in nutrient strength while your plants are screaming for mercy. This problem will continue to get worse until normal growth becomes abnormal. If this is not recognized, and the pattern continues into flowering, reduced yields and crop quality are near certain.

These are a couple of examples of potential pitfalls in treating printed feed charts as absolutes rather than guidelines.

Experienced growers learn to recognize their plants changing needs by careful observation and inference rather than force feeding their plants a prescribed diet. This is not to say that you can’t take control over your crop and steer it in the direction you desire. However figuratively speaking, driving it into a wall isn’t the answer just because the map says that it’s the right direction.

OK, so if you’re ready to do some tinkering, let’s get down to business.

The basis of this style of feeding will revolve around the notion that you can use a greater range of individual products on their own, over a greater number of applications rather than using fewer products in fewer applications but for longer durations. For those running automated systems it is suggested that you maintain intervals as a three day supply of nutrients, rather than a seven day cycle. Most growers using re-circulating media based systems usually need to replenish their reservoir within three days, as do their automated drain to waste counterparts (although the drain to waste growers are only limited to the size of their reservoir and changes in growth).

The following will be provided as an example of a specialized feed program, and is not necessarily the best and certainly not the only method; it is offered as an example.


1) Presoak rockwool cubes for a minimum of 24 hours in a well aerated, mild strength (1/4 X), low nitrogen to phosphorous and potassium solution . For rockwool only, the pH should be maintained at 5.5. Squeeze excess moisture from the cubes before proceeding. Most other medias will simply need to be watered with pH adjusted (6.3) solution as described above.
2) Apply a biological inoculant to cuttings and emerging seedlings to colonize the growing medium and plants’ surface with beneficial life. Inoculants may be either endo (inside) or ecto (outside) colonizers or both. Some innovative rooting plugs contain beneficial inoculants such as Trichoderma to improve biological activity. Biologicals can serve to protect the plant by colonizing it with an army of beneficial microbes, standing guard to any potential pathogens. Furthermore, they can trigger an increase in the biological activity of the plant itself.
3) After seedlings show their first set of true leaves (after the cotyledon leaves) or cuttings have begun to indicate rooting, water with a pH adjusted mild kelp or B-1 solution. Additions of high quality fulvic acid will improve vigour and reduce the feed strength requirements. Continue until a minimum of three new sets of leaves have developed. Take care not to over water tender young plants, as damping-off may occur (because you have created anaerobic conditions)

1) Soak seeds for a few minutes in a microbial inhibitor or a very mild bleach solution for a minute or two to disinfect the seed surface from any pathogens that may have been left as residues from the donor crop. Rinse well with distilled water.
2) Soak the seeds for up to 24 hrs in a very mild kelp or B-1 solution to increase germination rates and improve seedling vigour.
3) After soaking, transplant seeds to medium pre-treated as described in Cuttings.


1) If required, pre-treat the growing media to be transplanted into with pH adjusted, balanced nutrient solution as recommended by the manufacturer for transitional growth. With popular three part nutrients, this is typically a 1 part to 1 part to 1 part ratio with 1/4X to 1/2X kelp solution or B-1 solution. Additions of fulvic acid will increase the nutrient capabilities of the growing media and reduce the amount of fertilizer you will need to add (as it will increase the effectiveness).
2) Immediately after transplanting the crop, or a portion of larger crops, apply a biological innoculant (see Cuttings) as a drench or as per the manufacturer’s directions.
3) In soil or soilless gardens, allow the first inch of the medium to dry out before the next fertigation or watering.

Vegetative Growth:

Note: As discussed previously, the fertigation period is based on three day cycles, which is convenient in terms of automated nutrient delivery systems.

1) If the plants show no signs of nutrient stress, which symptoms include: abnormally dark leaves, scorched leaf tips, twisted or curling leaves; proceed to Step 2. Otherwise feed with a mild solution (400-500 ppm) as per Step 1 in Transplant. Re-evaluate after three days. In re-circulating systems, top up the reservoir with fresh water and monitor and adjust the pH accordingly.
2) Prepare the nutrient solution as per the manufacturer’s directions for this stage of growth. To play it safe you can use 50-75% of the recommended amounts and increase the feed strength after 3 days, when a new batch is mixed. In drain to waste systems where fertilizer solution is applied with each watering, many growers find that feed strengths of 500 to 750 ppm allow for vigorous growth with less risk of over applications while continuing to follow the manufacturers suggested feeding ratios.
3) If growth appears healthy and vigorous, proceed along with the manufacturer’s guidelines and time line. If plants show signs of stress, discontinue usage of additives and feed with the recommended general application formula not exceeding 650 ppm, adjusting the pH accordingly. Once normal growth resumes, you may choose to pick up where you left off on your feed chart and continue to the flowering/reproductive phase.

TIP: after two 3 day nutrient cycles (the 7th day) it is wise to mix a single day’s worth of ¼ strength nutrient solution to help remove any fertilizer residues which may accumulate before initiating another 3 day cycle. Alternatively, to reduce nutrient build up and improve root zone hygiene, consider applying a product to control the microbial load or enzymes to assist in breaking down decaying organic matter in the rhizosphere (root zone).

Early Flowering/Fruiting:

1) For the first and second nutrient cycle (6days) after initiating the photoperiod required for flowering, it is recommended that you apply only a transitional formula, as previously described not exceeding 500 ppm, unless plants indicate greater nutrient strengths are required (for example lower leaves become pale to yellow)
2) If you anticipate the variety you are cultivating has a relatively longer flowering period (8+weeks), you may consider continuing with the transitional formulation during the second nutrient cycling but increase the feed strength with additions of a supplement to elevate calcium/magnesium/iron/zinc levels while not significantly increasing nitrogen levels. If plants show signs of nutrient stress, dilute the solution in the reservoir and adjust the pH accordingly.
3) As previously, after 2 nutrient cycles (6 days) run a one day supply of fresh water with either an anti-microbial or enzymatic solution. Continue to proceed with the manufacturer’s recommendations as per the feed chart.

Flower Set/Early Fruiting

1) Indications of flowers should be visible within the first seven to ten days after initiating the critical photoperiod. If not, it is possible, that an abundance of nitrogen has delayed flowering, or that you are growing a variety with a very long period required to maturation. If there are no signs of nutrient stress, consider following the Early Flowering guidelines until flowers appear.
2) Follow the manufacturer’s recommendations for product and mixing instructions for this stage of flowering on the feed chart.
3) After the first cycle (3 days) consider re-inoculating the crop with a biological stimulant, as sometimes the effectiveness of previous applications can begin to diminish after several weeks following the initial inoculation. Continue to follow the manufacturers feeding recommendations, and reduce feed strength if plants show any signs of nutrient stress.


-Continue to run an anti-microbial or enzymatic solution with pH adjusted water for one day every 2 nutrient cycles (6 days).
-In drain to waste systems where fertilizer solution is applied with each watering, many growers find that feed strengths of 500 to 750 ppm allow for vigorous flowering while reducing the risk of delayed or diminished harvests.

Mid Flowering/Fruiting to Ripening:

1) Continue using the manufacturer’s feed ratios and product suggestions. If not already indicated on your chart, consider an addition of a low nitrogen, high phosphorous guano tea in conjunction with your regular feed mix. This should be applied with the regular nutrient cycles in weeks 4 to 6 of an eight week flowering cycle. It will help to add a third dimension of sorts to a hydroponic feed program. If the anticipated flowering cycle is longer or shorter, adjust the duration of the guano application accordingly.
2) If not already apparent in your feed chart, weeks 4 to 6 in an eight week flowering cycle is the window of opportunity to promote large blooms. If you have fertilized sparingly up until this point, it is now time to make the push. At this point, nitrogen levels should be greatly reduced in hydroponic systems, and near eliminated in soilless systems. Phosphorous levels should be at their highest levels. Potassium levels can also be increased to promote even ripening and is required in abundance for healthy seed production. Bloom supplements often contain elevated levels of both phosphorous and potassium, and may offer other benefits for floral or fruit production.
3) In soilless set-ups, the final 10 days prior to your anticipated harvest date, you should consider applying only fresh, pH adjusted water. If you are applying water only, do not cycle as frequently as previous stages. Water sparingly, as not to strip the plant of valuable nutrients, but enough to let the crop consume the nutrients it has stored in reserve within the plan and growing media. This will allow for superior flavours and palatability without sacrificing yields.
In re-circulating hydroponic crops, for the final 5 days before anticipated harvest feed strengths should be greatly reduced, but not necessarily eliminated. The only stored nutrients will be in the plant material itself, unless you are in an organic based hydroponic media, rather than inert or bare-rooted. Consider applying low nitrogen, high phosphorous guano tea or bloom supplement at 1/4X, while maintaining the appropriate pH levels. For the final 24 hours prior to harvest run only pH adjusted water through the system to flush away any residual nutrients remaining.

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