Cal/Mag deficiency?

Bumwhush

Bumwhush

Member
Howdy all. This is my first time growing indoors and I'm having an issue with my leaf tips turning yellow, curling up and brown/rust-like spots on the tips. From my research, it appears to be possibly be a cal/mag deficiency and I'm wanting to get advice as to the correct diagnosis. Here is my setup and info:

Strain: Kilimanjaro (pure landrace sativa), growing from feminized seeds
Day : 24 (Vegetative stage
System: hydroponic ebb & flow setup, growing in hydroton
Lights: 400w MH at 18" from the tops of the plants, running 24hrs.
Temps: range from 77 to 81
Humidity: ranges from 40-55%
Nutrients: General Organics BioThrive, CalMag, BioRoot, Bioweed (This is day 10 of using nutes, they are still at 50% of recommended amounts)
Water: using spring water, feeding every 12 hours.
Ph: between 5.8 to 5.95

I added 25 ml of CalMag to my reservoir yesterday, which was at a little over 6 gallons left of water. I do not have a ppm/ec meter at this time, but will purchase one soon. Am I correct on the diagnosis and should I make anymore adjustments or wait to see what adding the extra CalMag?





First pic is of my setup.
Second pic is from plant 1 (with minor yellowing/brown spots).
Third pic is plant 2 (with lots of yellowing/brown spots on bottom leaves and starting to appear on top of leaves).
Fourth pic is a close up on the under leaves on plant 2).

013 Grow Room (week 2) 0915.jpg 016 DAY 24 092915.jpg 017 DAY 24 092915.jpg 018 DAY 24 092915.jpg
 
Bumwhush

Bumwhush

Member
AGrower said:
MAGNESIUM (MG)

Magnesium (Mg) deficiency is common in all mediums and hydro. It is not common outdoors.

Symptoms
Mg deficiency starts in the lower leaves. The veiwns remain green while the rest of the leaf turns yellow, exhibiting chlorosis. The leaves eventually curl up, and then die. The edges of affected leaves feel dry and crispy. As the deficiency continues it moves from the lower leaves to the middle to upper half. Eventually the growing shoots change from a pale green white color. The deficiency is quite apparent in the upper leaves. At the same time, the stems and petioles turn purple. Mg is mobile.

Role in plant nutrition
Mg helps support healthy veins and maintains leaf production and structure. It's required for chlorophyll production and enzyme breakdowns.

Problem Solving
Water-soluble nutrients containing Mg fix the deficiency. Such nutrients containing Mg sulfate (MgSO4, Epsom salts) and Ca-Mg for fast absorption; and dolomite lime/garden lime and worm castings for moderate absorption.
In hydro and planting mixes Mg deficiencies are easily fixed using 1 teaspoon (4.9cc) of Epsom salts per gallon (1.3cc per liter) of water in reservoirs. In planting mixes user 1 teaspoon per quart (5cc per liter) of water in planting mixes. After the first treatment, use one-quarter dose with each watering or change of reservoir. Ca-Mg can also be used.

For fast action Epsom salts can be used foliarly at the rate of 1 teaspoon per gallon (1.3cc per liter). Ca-Mg can used foliarly as directed.
Dolomitic limestone contains large amounts of Mg. It can be used to raise the pH of soils and planting mixes and supply Mg at the same time.

General Discussion
Mg deficiency is one of the easiest nutrient deficiencies to diagnose and sure. It occurs more frequently if using distilled, reverse osmosis water and tap water that has low ppm count.
Click to expand...

That was my initial diagnosis but after looking at various pictures with potassium deficiencies, they appear to be very similar in appearance. I added more BioThrive Grow to the soup as well, as I'm sure it could use it since I haven't added any nutes in the past few days.

I am using spring water that has no more than 50 ppm, so it would appear that it is a Mg deficiency since it tends to happen to water that has low ppm to start with.

I just ordered a TDS meter to help keep track of the nutrient use and should be able to have better schedule of when to add more nutes to the soup.
 
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