Low Substrate Phosphorus Corrective Procedures
Brian E. Whipker, James L. Gibson, Paul V. Nelson, Todd
J. Cavins, and John M. Dole
Disclaimer: Growers should read and follow all label
directions. Test the corrective procedure on a small number of plants
prior to applying it to the entire crop.
|The amount of fertilizer supplied is lower
than the crop's nutrient demand (crops are categorized as light, medium
or heavy feeders), or at a particular stage of development (actively
growing plants have greater nutrient demands than young or flowering
||1. Increase fertilization frequency (use
more frequent fertilization irrigations instead of clear water irrigations).
2. Increase fertilizer rate.
3. Avoid leaching the substrate with clear water irrigations.
4. Recheck the EC values to make sure they are within the acceptable
|P lacking in fertilizer program (eg. no P starter charge
used or dark weather feed [calcium nitrate + potassium nitrate] used
which does not contain P).
||1. Use a fertilizer that contains P.
2. If injecting acid to neutralize alkalinity, consider supplying
P from phosphoric acid (upper limit of 10 to 15 ppm P).
|Leaching too great.
|1. Avoid leaching the substrate with clear water irrigations.
2. Recheck the EC values to make sure they are within the acceptable
||1. Check the EC of the clear water and the fertilizer
solution. Fertilizer solution EC minus clear water EC = EC contribution
of the fertilizer. Compare this value with the tables on the fertilizer
bag to determine the fertilization rate being applied.
|Fertilizer mixing rate error and too little fertilizer
||1. Check if the amount of fertilizer used, the size
of the concentrate bucket, and the proportioner setting are correct.
|Don't forget to check out the Plant Root Zone Management
(PRZM) Manual for more information! Want to know more? Click
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