Some of the key factors in this chart are :
TIME
As time progresses , you will see the recommendations changing for the amount of various formulas added . For the chart above , the plant being considered in this example has a 12-week growth cycle before harvest . Most tomato plants will take this long , while some varieties mature more quickly . Some charts found online allow you to modify the number of weeks to maturity . In any case , find out how many weeks it will / should take your crop to mature and use a chart that reflects this . Seedlings and cuttings will usually be listed for the first week or two on a nutrient chart . Nutrient requirements are low for new plants with tender root systems and care must be given not to overfeed during this phase . On most charts , there will be nutrient varieties especially formulated for :
• seedlings and cuttings
• root building
• blooming or transition
• flowering or fruiting
• ripening
• cleansing or flushing
The nutrient formulas for these different phases of growth are designed to be best for the plant when it is in that phase of growth . Each of these plant phases will be listed along one line ( vertical or horizontal ) with the week number , while the various formula name brands are listed on the other line opposing line .
Most charts are laid out by the week , but the nutrient amount listed should be given as called for in the feeding tips section ( once a week , daily , etc .). As the growth phase of each plant varies throughout the cycle , the formula recommended is often varied . The richness of the nutrient solution will be measured by the EC or ppm readings you take . If these readings get too high or low , adjust the amount of nutrient applied in order to closely match these concentration measurements .
EC
The electric conductivity of the reservoir nutrient solution will indicate the essential concentration of the fertilizer being fed . There are many meters on the market to help you measure this , and this measurement is likely to be one of the most important you make .
PPM
The scientific parts per million ( ppm ) of nutrient in the solution is a measurement of the dried weight of the residue in the solution in relation to the initial liquid volume . This is obviously laborious , and it can be estimated by an EC measurement . There are conversion factors ( internal to the EC meter ) and these range from 0.5 to 0.72 . Influent water contains undesirable dissolved solids that show up as ppm , so this needs to be considered when using your EC reading . If not specified in the brands feeding tips , reduce your range by your influent ppm . Often recommended in a chart are one or more rinse cycles . Rinse cycles are sometimes recommended the week before a new or different formula is to be started in order to help the new formula provide the strongest impact on the crop . Often a thorough rinse or flush is recommended a week or two before harvest to reduce the concentration of various nutrients from the consumable leaf of the plant before harvest .
LIGHT HOURS
We can see that the hours of illumination are changing as the plant goes from leafy growth to bud and bloom . With many plants , the reduction of illumination hours can actually trigger them into blooming . By controlling the hours of illumination more accurately , you can help the plants mature and produce more quickly .
NUTRIENT FORMULA
There is a primary separation of instructions for any nutrient feeding chart . Why ? Because the different concentration levels for the many various nutrients in each product demand substantially different feeding amounts . If the nutrient you use does not have an identical formula , you can ’ t assume that chart would work for your nutrient .
INFLUENT TDS AND SOLUTION PH
Often discussed in the feeding tips section on a nutrient bottle are things like influent TDS and solution pH . At this point it is good to remember that the influent water may contain a TDS value of up to 800 ppm in Las Vegas and as low as 50 ppm in Seattle . Whatever the influent reading is , it needs to be taken in conjunction with the EC reading of the nutrient solution in making nutrient concentration levels .
“ THE BETTER informed the grower is of these aspects and how they affect nutrient requirements , the better choice they can make toward optimal feeding practice .”