Nice to meet you all from Indonesia (and an overview on my plant journey)

[Wiandry Adi]

I see that this thread gets hot and hotter! After the fiasco on the calculator site Steve had recommended here, I guess I had to revise the plan to weigh everything so that means a delay on the results. I'll get to the results by this week!

OK, so I'll give the rundown of the ferts' weight measurement plan:

• Weigh both PROVIT Hijau and FLEX-G by 10 times and measuring the mean value (the ultimate weight I'll put as the threshold)

• Weigh both potassium and ammonium sulfate by 1/2 tsp

• Include the pH bound result (the fert solution in jar one)

• Get the EC (and TDC) meter result

Another way to measure fertilizers is by EC. Example,- There is 100ppm N in the solution (and 0.4 grams) of Ammonium sulphate dissolved in 1 litre of water when the EC reads 0.96 dS/m. For potassium sulphate it's 100ppm K at an EC of 0.34 (0.22 grams/litre)
I have the figures for all the fertilizers if you want to be ultra precise and go down that route. You need a good EC meter for this.

Hmm... I'm kinda conflicted by this. I don't have expertise on chemistry and physics though that doesn't mean I'm forever not knowing about it. Given time, I'll learn everything about this slow and steady; but at the moment, I don't have much time to get things ultra-precise, so I'm trying to keep it safe by under-weighing the fert formula according to the final result (to prevent accidental over-fertilization). With that posted, I'll get the EC meter (which in my place, it's also available as TDS meter; so it's TDS & EC meter).

Steve, that calculator you linked to is an example we all need to be aware of, the great need to be careful with what we use from the Internet. I remember finding that site a few years ago and almost getting fooled by it. At least it gives the calculations of what it is doing. Too bad it is not spelled out in detail that it can't be used to convert powders from volume to weight. I suspect a lot of people get tripped up with that site. It looks impressive, but....

Agreed -- nothing beats having an accurate digital scale so we can measure dry weights for ourselves.

Another way to measure fertilizers is by EC. Example,- There is 100ppm N in the solution (and 0.4 grams) of Ammonium sulphate dissolved in 1 litre of water when the EC reads 0.96 dS/m. For potassium sulphate it's 100ppm K at an EC of 0.34 (0.22 grams/litre)
I have the figures for all the fertilizers if you want to be ultra precise and go down that route. You need a good EC meter for this.

We don't need to be that precise!

When I started my current collection in 2011, I was going to a cactus nursery that had been around since 1975. What I didn't realize at the time -- the owners were pumping their cacti up with N, producing a phenomenon I call "nitrogen bloat". This example comes from a Tephrocactus articulatus inermis I purchased there in April 2012:

Tephrocactus_articulatus_var_inermis04102012.JPG

Starting from the upper left -- 5/6, 5/26, 8/5, and 10/7/2012:

Tephrocactus_articulatus_var_inermis0506-0526-0805-10072012resized.jpg

Diluting 1/2 teaspoon Dyna-Gro 7-7-7 per gallon, the inermis was getting 46 ppm N per feeding (and yes, fertilizing every time I water). N being applied at the nursery must've been well above 90 ppm per feeding, so these photos show the difference between that and bringing the N down to a more acceptable level. By the way, I could show you what the inermis looks like these days, but you'll have to wait until I get my 2023 end-of-summer review going. (Shameless self-promotion! )

Now we have a pretty good idea of what nitrogen bloat looks like. If growers can see it in their cacti, there are a couple of important things that need to be done -- find out about how much N you've been feeding your plants, and reduce the amount of fertilizer going into your watering solution.

Okay, Adi -- I'm eager to get started on your dilutions for the Hijau, FLEX-G, and potassium sulfate. Once you give me their 1/2 level tsp. weights, I'll crunch some numbers and give you the results as soon as I can.

Coincidentally, my next month's garden update will feature a large Tephrocactus and they grow great! ...so far. I'll give the results by this week and I'll wait for the (hopefully) final verdict afterwards.

Also, by what you posted about skipping fertilizing once in a while, so that means flushing the pots as well?

I was thinking several scenarios regarding this:

• Fertilize by-weekly; fertilize, not fertilize, fertilize, and so on

• Skip fertilizing by the last week of the month; fertilize, fertilize, fertilize, not fertilize, and so on

• Fertilize by half strength bi-weekly; fertilize on full dosage, fertilize by half dilution the next week, and so on

I just found this week where it seems watering them without first preparing the ferts is the ideal thing to do as I got sudden business that ruined my entire schedule, and I had to water my plants at night. Also I now dealt with a nosy cactus seller who's more of coerced (and somehow gaslighted) me to make transaction than understand my predicaments. First time dealing with this kind of seller to be honest since all of other sellers I'm dealing with are fine with me bookmarking my potential collection - down-paying for them first - so I can buy them next month, with some of them will remind me if my picked collection has been sold to someone else.

What a roller-coaster of emotion last week was!

Also, how was the solar eclipse yesterday? I see in the news it's only visible in the Americas, so I didn't get any visual unfortunately

[Steve Johnson]

I see that this thread gets hot and hotter! After the fiasco on the calculator site Steve had recommended here, I guess I had to revise the plan to weigh everything so that means a delay on the results.[/list]

Sorry about the confusion, and I'm glad Jerry pointed out the problem with using the Aqua-Calc calculator. Besides that, you wouldn't have been able to use it for weighing your fertilizers. As I said in my previous post, nothing beats having an accurate digital scale so we can measure dry weights for ourselves. Once we convert weight into volume, you'll be able to dilute by volume with your half-teaspoon measures.

OK, so I'll give the rundown of the ferts' weight measurement plan:

• Weigh both PROVIT Hijau and FLEX-G by 10 times and measuring the mean value (the ultimate weight I'll put as the threshold)

• Weigh both potassium and ammonium sulfate by 1/2 tsp

• Include the pH bound result (the fert solution in jar one)

• Get the EC (and TDC) meter result

No ammonium sulfate -- for the Hijau and FLEX-G, the only supplement you'll need is potassium sulfate. Just to be clear, all I need are the mean-value weights of 1/2 level tsp. Hijau, 1/2 level tsp. FLEX-G, and 1/2 level tsp. potassium sulfate. The Pak Tani, PROVIT Orange, and Multiara GROWER are about to become things of the past for you. Regarding EC/TDC meters -- great for professionals, but as an amateur hobbyist, I never found a use for them.

Also, by what you posted about skipping fertilizing once in a while, so that means flushing the pots as well?

I was thinking several scenarios regarding this:

• Fertilize by-weekly; fertilize, not fertilize, fertilize, and so on

• Skip fertilizing by the last week of the month; fertilize, fertilize, fertilize, not fertilize, and so on

• Fertilize by half strength bi-weekly; fertilize on full dosage, fertilize by half dilution the next week, and so on

Flushing your pots every 6 months certainly qualifies. If you need to be on a regular no-fertilizer schedule beyond that, I think no fert at the end of each month should be fine. Before you make that a for-sure, let me do the dilution calcs and see the ppm numbers in your prospective watering solution.

Also, how was the solar eclipse yesterday? I see in the news it's only visible in the Americas, so I didn't get any visual unfortunately.

I went to bed yesterday at 4 a.m., so the eclipse came and went before I had the chance to see it. Nerts!

[Wiandry Adi]

Quick update:

While I'm preparing the results for the next fert formula, I'll share the conditions of my place at this week.

The temperature range has been above 34°C and even for the last two days, it's reached as far as 37°C. To make things more 'exciting', it's even been ridiculously windy, more sunlight up to 3 p.m., and no clouds whatsoever. Afternoon sun was actually painful, and I've heard some of people around me experiencing heatstroke. When I do some other research, I see it's similar to Arizona's. It's just that hot.

I read somewhere that at certain time, it's recommended to water cacti twice a week when it's so scorching hot. Shall I do this? And shall the fert number be increased or decreased?

[Steve Johnson]

Quick update:

While I'm preparing the results for the next fert formula, I'll share the conditions of my place at this week.

The temperature range has been above 34°C and even for the last two days, it's reached as far as 37°C. To make things more 'exciting', it's even been ridiculously windy, more sunlight up to 3 p.m., and no clouds whatsoever. Afternoon sun was actually painful, and I've heard some of people around me experiencing heatstroke. When I do some other research, I see it's similar to Arizona's. It's just that hot.

I read somewhere that at certain time, it's recommended to water cacti twice a week when it's so scorching hot. Shall I do this? And shall the fert number be increased or decreased?

Hi Adi,

The summertime highs on my plant bench range anywhere from 31 to 40 C, and I don't water any more often at the upper end of that range than I do at the lower end. (Bear in mind that I water most of my cacti every 2 weeks in spring and summer.) To give you some perspective, check out your local forecast here:

https://www.timeanddate.com/weather/ind ... akarta/ext

A couple of things to consider -- first, there's a big difference between the low humidity in Arizona, and your fairly high humidity. In fact, your humidity levels are similar to mine, hence the reason why I don't think you need to water twice a week. But there is one thing you'll need to watch out for -- the possibility of summer dormancy. Inexperienced growers get fixated on daytime highs without thinking about overnight lows. When overnight lows are consistently above 25 C, cacti are fat, happy -- and asleep. Normally, cacti open their stomata (skin pores) for transpiration at night, but the stomata stay closed in summer dormancy conditions -- those are the conditions for not watering unless your cacti show new top growth. If you have ever lost cacti to rot for no apparent reason, chances are that they were going through summer dormancy and you didn't even know it. I highly recommend that you buy a digital outdoor thermometer that records highs and lows -- this will be the best way to know if you're dealing with summer dormancy conditions.

By the way, compared to timeanddate.com, Weather Underground may give you more accurate 10-day forecasts:

https://www.wunderground.com/forecast/id/east-jakarta

Nice thing is that you can select different nearby weather stations. Regarding fertilizer, dilution doesn't change just because of the heat.

[Wiandry Adi]

A couple of things to consider -- first, there's a big difference between the low humidity in Arizona, and your fairly high humidity. In fact, your humidity levels are similar to mine, hence the reason why I don't think you need to water twice a week. But there is one thing you'll need to watch out for -- the possibility of summer dormancy. Inexperienced growers get fixated on daytime highs without thinking about overnight lows. When overnight lows are consistently above 25 C, cacti are fat, happy -- and asleep. Normally, cacti open their stomata (skin pores) for transpiration at night, but the stomata stay closed in summer dormancy conditions -- those are the conditions for not watering unless your cacti show new top growth. If you have ever lost cacti to rot for no apparent reason, chances are that they were going through summer dormancy and you didn't even know it. I highly recommend that you buy a digital outdoor thermometer that records highs and lows -- this will be the best way to know if you're dealing with summer dormancy conditions.

So, at what temperature I shall pay attention to inspect for any sign of dormancy in my collection? I saw this old thread here - https://cactiguide.com/forum/viewtopic.php?t=6728 - and I see some hints:

Now i'm sure this is the last thing on all you northerner's minds right now, but when it gets really hot (like right now, 39 degrees, 36 tomorrow and scheduled 41 for the next), when plants go dormant due to the heat and it is recommended that you withold watering, how long do they remain in this state after a heatwave, and when is it safe to recommence watering? .What if the plants are putting on new growth and flowering?

Some cacti are not set up to go dormant so readily when the hot weather hits at the start of summer. They may continue to grow and require quite a lot of water until temperatures are nearer to 50C than 40C. Doubly true if your nights are still fairly cool, while a string of hot nights will shut down a great many plants. Other species are pre-programmed to shut down in May for a couple of months and tend to do it whether it is excessively hot or not.

Its tough to do but when your plants stop growing in hot weather you really do need to lay off the water. Dormant plants don't take up water so they will sit in wet soil and rot. Or maybe you will get lucky and the water will evaporate first. Do you feel lucky, ducky?

No, you're not. Watch the plants. Warm weather is just a warning sign of possible dormancy.

If it is intensely hot but the plant insists on growing then you will need to provide water and probably a lot of it. Many Brazilian and Caribbean plants, for example, will continue to grow in hot weather and they will grow very fast but they will suffer without water.

If the plant is dormant, whatever the temperature, then do not water other than perhaps a spray. Some plants, mostly non-cactus succulents, you can guarantee will be dormant all summer. Most cacti will continue to grow unless it is extremely hot, but some cacti will become dormant on a timetable. Don't join those people who say they are impossible to grow simply because they insist on treating them like a Notocactus. Not always easy to spot when a cactus has gone dormant in summer, but always easy not to water if you are unsure

I conclude if it ever reaches 39 to 40°C on daytime and 27°C in nighttime, then I shall brace for the Great Dormancy and get my water spray and give them spritz, though I'd like some suggestions on taking care of dormant cacti.

[Steve Johnson]

That thread is probably the best explanation of what to look for. However, there's a caveat -- all the posts you saw there assume that most growers live in the northern hemisphere. For people like me who do, the year is divided by a spring-summer growing season, and a fall-winter dormant season when the nights are cold and day lengths are short in the winter. The hot nights of summer dormancy are a problem only in places like Arizona, Nevada, and New Mexico. You, on the other hand, live in a tropical climate where the growing season is pretty much year-round, and what we call "summer dormancy" may happen to you and your cacti at any time of the year.

Another assumption commonly made on the forum is that everyone knows what new growth looks like. Bad assumption, and it would be helpful if you know what to look for there:

• Single-stem cacti -- the growth point is at the very top of the plant. Look for the presence of new spines forming. Many species also produce apical wool on the growth point, and new wool has a certain "vibrant" appearance that'll be different from wool that looks "dingy".

• Clustering cacti -- aside from the growth point on the parent stem's top, the plant will start growing offsets on the stem. These offsets are new stems in their own right, and they also have growth points on their tops.

It takes time to know what the growth points of your cacti look like when they're active and when they're inactive. If your powers of observation are good, you'll be able to spot the difference. When their growth points are active, water them on your normal schedule. When their growth points appear to be inactive due to summer dormancy conditions, give them an occasional spritz at night to keep their stems hydrated. Could it be every few days? Once a week? Can't tell you, so you'll just have to use your best judgment.

By the way...

No disrespect to iann, but he could never explain anything well.

[Wiandry Adi]

That thread is probably the best explanation of what to look for. However, there's a caveat -- all the posts you saw there assume that most growers live in the northern hemisphere. For people like me who do, the year is divided by a spring-summer growing season, and a fall-winter dormant season when the nights are cold and day lengths are short in the winter. The hot nights of summer dormancy are a problem only in places like Arizona, Nevada, and New Mexico. You, on the other hand, live in a tropical climate where the growing season is pretty much year-round, and what we call "summer dormancy" may happen to you and your cacti at any time of the year.

Another assumption commonly made on the forum is that everyone knows what new growth looks like. Bad assumption, and it would be helpful if you know what to look for there:

• Single-stem cacti -- the growth point is at the very top of the plant. Look for the presence of new spines forming. Many species also produce apical wool on the growth point, and new wool has a certain "vibrant" appearance that'll be different from wool that looks "dingy".

• Clustering cacti -- aside from the growth point on the parent stem's top, the plant will start growing offsets on the stem. These offsets are new stems in their own right, and they also have growth points on their tops.

It takes time to know what the growth points of your cacti look like when they're active and when they're inactive. If your powers of observation are good, you'll be able to spot the difference. When their growth points are active, water them on your normal schedule. When their growth points appear to be inactive due to summer dormancy conditions, give them an occasional spritz at night to keep their stems hydrated. Could it be every few days? Once a week? Can't tell you, so you'll just have to use your best judgment.

By the way...

No disrespect to iann, but he could never explain anything well.

Well, in that case, I may need to buy a thermometer for a more exact calculation, since I do notice a lot of new growth on my collection, cacti and non-cacti, though (at the moment, I think) it happened at random (like the Pilosocereus one, it's still constantly growing though sluggish to follow) and again, keep in mind most of my collection gets shaded after 12.00 p.m. with few of them unfortunately (now) still gets sunlight 'til 3.00 p.m. I think being in shade may affect temperature and humidity as well, but I say I'll need more reinforcement for the better.

Also, can you recommend any references in regards of cactus dormancy, like which one has winter dormancy and which one has summer dormancy? (hold up... could CactiGuide actually have this kind of list? )

[Wiandry Adi]

The results are in!

Here are the results for the requested criteria from previous threads:

• pH bound result (for Pak Tani - GROWER solution): 7.74 (7 > 6.50 > 7.74)

• Mean weight of each ferts (1/2 tsp):
  • 1.98 gr Hijau
  • 3.17 gr FLEX-G
  • 3.05 gr potassium sulfate

I'll kindly wait for the next calculation and anything additional if necessary

[jerrytheplater]

Another way to measure fertilizers is by EC. Example,- There is 100ppm N in the solution (and 0.4 grams) of Ammonium sulphate dissolved in 1 litre of water when the EC reads 0.96 dS/m. For potassium sulphate it's 100ppm K at an EC of 0.34 (0.22 grams/litre)
I have the figures for all the fertilizers if you want to be ultra precise and go down that route. You need a good EC meter for this.

Here's what I have: https://www.myronl.com/products/handhel ... ameter-ii/ I have one similar to the Ultrameter II 6PFCe. Mine does not do the free chlorine. It is an earlier model which is no longer sold. It reads in milli or micro siemens per cm, depending on the range needed for the solution.

[Steve Johnson]

Hi Adi,

All desert cacti go through fall/winter dormancy in the northern hemisphere. This is something you won't see because you live in the tropic zone. As I said in my previous post, summer dormancy in the US is a problem only for places like Arizona, Nevada, and New Mexico -- we're talking about overnight lows well above 27 C throughout the summer. There aren't any references regarding dormancy, and this is something growers need to learn based on how their cacti behave under various temperature conditions. When your cacti are growing, water them according to your normal schedule. If you see cacti that have decided to stop growing while the overnight lows are above 25 C for more than a few days, stop watering them until they start growing again. When in doubt, don't water.

By the way, there are two genera that are perfect for tropic zone growers:

http://www.llifle.com/Encyclopedia/CACT ... scocactus/

http://www.llifle.com/Encyclopedia/CACT ... elocactus/

If you haven't tried growing Discocactus or Melocactus before, you should do well with them -- unlike us northern hemisphere folks who struggle to keep them alive through our cold winters. That's one advantage you have, and the other -- Discos and Melos don't go through summer dormancy.

• Mean weight of each ferts (1/2 tsp):
  • 1.98 gr Hijau
  • 3.17 gr FLEX-G
  • 3.05 gr potassium sulfate

Got it -- I'll work on the calculations for you over the weekend.

• pH bound result (for Pak Tani - GROWER solution): 7.74 (7 > 6.50 > 7.74)

Just wanted to make sure I'm reading this correctly -- your untreated tap water has a pH of 7.0, the Pak Tani and Multiara GROWER bring the pH in your watering solution down to 6.50, and the pH rebounds up to 7.74 after 7 days in your test jar. This can happen only if the ferts are releasing bicarbonate into the water, and I don't see how it's possible. No point in worrying about it at the moment since you'll need to run the test again with the Hijau, FLEX-G, and potassium sulfate diluted in your watering solution. When you do, please be sure to recalibrate your pH meter first in case it went out of calibration. This has been known to happen with digital pen-style meters, and I always recalibrate mine right before I use it.

[Wiandry Adi]

Hi Adi,

All desert cacti go through fall/winter dormancy in the northern hemisphere. This is something you won't see because you live in the tropic zone. As I said in my previous post, summer dormancy in the US is a problem only for places like Arizona, Nevada, and New Mexico -- we're talking about overnight lows well above 27 C throughout the summer. There aren't any references regarding dormancy, and this is something growers need to learn based on how their cacti behave under various temperature conditions. When your cacti are growing, water them according to your normal schedule. If you see cacti that have decided to stop growing while the overnight lows are above 25 C for more than a few days, stop watering them until they start growing again. When in doubt, don't water.

By the way, there are two genera that are perfect for tropic zone growers:

http://www.llifle.com/Encyclopedia/CACT ... scocactus/

http://www.llifle.com/Encyclopedia/CACT ... elocactus/

If you haven't tried growing Discocactus or Melocactus before, you should do well with them -- unlike us northern hemisphere folks who struggle to keep them alive through our cold winters. That's one advantage you have, and the other -- Discos and Melos don't go through summer dormancy.

• Mean weight of each ferts (1/2 tsp):
  • 1.98 gr Hijau
  • 3.17 gr FLEX-G
  • 3.05 gr potassium sulfate

Got it -- I'll work on the calculations for you over the weekend.

• pH bound result (for Pak Tani - GROWER solution): 7.74 (7 > 6.50 > 7.74)

Just wanted to make sure I'm reading this correctly -- your untreated tap water has a pH of 7.0, the Pak Tani and Multiara GROWER bring the pH in your watering solution down to 6.50, and the pH rebounds up to 7.74 after 7 days in your test jar. This can happen only if the ferts are releasing bicarbonate into the water, and I don't see how it's possible. No point in worrying about it at the moment since you'll need to run the test again with the Hijau, FLEX-G, and potassium sulfate diluted in your watering solution. When you do, please be sure to recalibrate your pH meter first in case it went out of calibration. This has been known to happen with digital pen-style meters, and I always recalibrate mine right before I use it.

I see there are tables listing which succulents went either winter or summer dormancy but none of them specify cacti or any plants within the cactus family. Also there may be information about cactus dormancy in detail on literature or the internet, but searching and gathering said info would be too challenging compared to my ever-busy schedules.

So far, nighttime average last week was about 25 - 27°C. I'll get a thermometer (plus hygrometer to measure humidity) by next month or next week, ideally.

Didn't I attach one of my Melocactus collection, the azureus one on my 'monthly update' thread? Well, I do have 10 (and counting) Melocactus, with curvispinus and bahiensis being the most number of specimens. Also, about Discocactus, I founf it after doing thorough research several months ago after I identify several cacti seedlings that were given to me from a seller as a bonus from purchasing their cacti. I thought it was another Melocactus due to its form, and even I speculated it was another Echinocactus.

Also, regarding pH bound test, I wonder what are the main goal/objective for said test? I mean, if the pH could go higher than the initial pH, there's something we can understand from it and formulate our ferts accordingly, yes? Though I may be guilty for not calibrating my meter that time, but I have a roaring question: how often shall I calibrate it? Pardon me if I'm missing something here.

Another way to measure fertilizers is by EC. Example,- There is 100ppm N in the solution (and 0.4 grams) of Ammonium sulphate dissolved in 1 litre of water when the EC reads 0.96 dS/m. For potassium sulphate it's 100ppm K at an EC of 0.34 (0.22 grams/litre)
I have the figures for all the fertilizers if you want to be ultra precise and go down that route. You need a good EC meter for this.

Here's what I have: https://www.myronl.com/products/handhel ... ameter-ii/ I have one similar to the Ultrameter II 6PFCe. Mine does not do the free chlorine. It is an earlier model which is no longer sold. It reads in milli or micro siemens per cm, depending on the range needed for the solution.

That's a splendid tool you have there. I'll try to get any similar instruments that is sufficient for my current expertise

[MikeInOz]

Here's what I have: https://www.myronl.com/products/handhel ... ameter-ii/ I have one similar to the Ultrameter II 6PFCe. Mine does not do the free chlorine. It is an earlier model which is no longer sold. It reads in milli or micro siemens per cm, depending on the range needed for the solution.

Looks ok Jerry but wouldn't one you can dip be easier? Anyway I've gone through 3 of them but I don't use them anymore.

[Steve Johnson]

...regarding pH bound test, I wonder what are the main goal/objective for said test?

Sorry about being Mr. Picky-Fussy, but we're testing for pH rebound -- pH going down and rebounding back up. When bicarbonate alkalinity in tap water is detected with a pH meter (pH above 7.0 = bicarbonate is present), the point of the rebound test is to see if acidity in the fertilizer neutralizes the watering solution's bicarbonate either fully or partially. If neutralization is only partial after 5-7 days, an acidifier should be added to the watering solution when the potting medium is pH-neutral or alkaline. The goal -- pH starting at about 6.0 and ending at 7.0 when the mix goes from wet to dry. Whether or not the grower needs to add an acidifier can be determined in advance by testing rebound after 7 days with a sample jar of watering solution.

Assuming that your tap water really doesn't have bicarbonate alkalinity, the only thing you'll need to do is test the pH of the watering solution right after you add fertilizer. Using the example you gave me from yesterday -- Pak Tani and Multiara GROWER lowers the pH of your tap water from 7.0 to 6.5. In your 9/22 post, you found that your acidic mix has a pH of 6.56, so it'll start out with a pH of 6.06 right after you water. If there's any rebound at all, it'll be small and when it dries out we should expect that the mix will end with a pH of -- 6.56. You found that your alkaline mix has a pH of 7.1, so it'll start out with a pH of 6.6 right after you water. The mix will probably end with with a pH of 7.1 when it dries out. Long story short -- for your acidic mix, you don't need to add an acidifier on top of the acidification done by the ferts. For your alkaline mix, I would recommend that you bring the pH down closer to 6.0-6.2 with the correct amount of citric acid in your watering solution. Of course the numbers may change when you start using the Hijau, FLEX-G, and potassium sulfate, so be prepared for a retest after I come up with the right dilution amounts for you.

Going back to the results of your pH rebound test, rebounding up to 7.74 after 7 days doesn't make any sense, so I think we can chalk it up to a measuring error. Which brings me to this...

Though I may be guilty for not calibrating my meter that time, but I have a roaring question: how often shall I calibrate it? Pardon me if I'm missing something here.

Yeah, I skipped a step. Buy a bottle of pH 7.0 reference solution online or at your local hydroponics shop. Every time you use the meter, test it with the reference solution first. If it reads 7.0, the calibration is still good. If it gives you a different reading, you'll need to recalibrate. Meters with 1-point calibration can be recalibrated with the reference solution. Meters with 2-point calibration need to be recalibrated using the reference solutions provided or recommended by the manufacturer. In my case, Poniie provided me with 4.0 and 6.86 reference solutions. I realize that having to recalibrate one's pH meter can be a labor-intensive pain in the you-know-what, but there's a point when it'll be less of a pain.

One last thing about digital pen-style pH meters:

• The meter's probe cannot be allowed to stay dry for extended periods of time.

Manufacturers include a cap for the probe -- put a little bit of reference solution or KCl storage solution in the cap to keep the probe wet. Hopefully you've already been doing this.

I should have the dilutions ready for you tomorrow night or over the weekend.

[Wiandry Adi]

Hi Steve,

Sorry that I forgot to put additional info regarding the wacky pH rebound test result: I put the solution in a small glass jar which I don't remember cleaning it before I put the solution into it. If I remember it correctly, said jar has also been used to contain various kinds of ferts and whatnot so I assume this may result in the pH getting too high. This is because I've tried the meter again - no calibrating - and found the initial water pH is still normal, at pH 7, sometimes 7.10.

Again, I'm not sure why. That test result was quite looney, if not whimsical.

[Steve Johnson]

Hi Adi,

Since your tap water fluctuates between 7.0 and 7.1, you do have a small amount of bicarbonate in the water, but not enough to be concerned about. The bigger concern is knowing the levels of carbonate hardness (KH) and non-carbonate (general) hardness (GH) in the water. Both types of hardness are measured in parts-per-million and milligrams per liter. I'm quite sure that the people you've been talking to don't know what the numbers even are, so it's best for you to test your tap water with aquarium test strips you can buy online or at your local aquarium shop. Here's an example of what to look for:

Anniple_pH_test_strips.jpg (63.95 KiB) Viewed 203287 times

These test strips are available on Amazon US (in fact I should buy them myself! ), but I don't know if 9 in 1 test strips are available from another manufacturer in Indonesia. If not, look for test strips specific to KH and test strips specific to GH -- test strips that show only total hardness won't be useful. When you dip the test strip(s) in tap water, look at the colors and compare them to the product's color chart. Those colors will give you a reading of KH and GH levels. Converting mg/L to ppm is easy -- 1 mg/L = 1 ppm. A couple of things to bear in mind here:

• The GH test doesn't make a distinction between the amounts of Ca and Mg cations in the water, so we don't have a way of knowing the Ca-Mg ratio. In practice this really doesn't matter -- if the GH levels are high enough, your cacti and succulents will be able to get what they need from the water. Just a guess on my part, but GH higher than 50 ppm should be great, in which case Ca from the gypsum you add to your pots is a nice little bonus.

• KH is neutralized through acidification. And now we have a good reason for testing rebound in your watering solution after you add fertilizers to the water. I'll explain further as we get to...

...the main event -- and I think you'll like it!

Meroke_FLEX-G-PROVIT_Hijau.jpg (79.39 KiB) Viewed 203287 times

The dilutions per 50 liters of water are:

• Meroke FLEX-G -- 1/2 tsp. x 2

• PROVIT Hijau -- 1/2 tsp. x 4

• Potassium sulfate -- 1/2 tsp.

Nutrient dosages in the watering solution are:

• 53 ppm N

• 17 ppm P

• 80 ppm K

17/53 = 0.32 on the P side of the NPK ratio, and 80/53 = 1.51 on the K side of the ratio -- this balance is ideal. And with 53 ppm N per feeding, accidental over-fertilization simply won't happen. If you decide on no-fert watering at the end of each month just to be on the safe side, your plants won't starve to death.

There are 2 other nutrients we'll review. First, the FLEX-G and potassium sulfate contribute 16 ppm S to your watering solution -- good enough. The FLEX-G and Hijau contribute 3 ppm Mg -- probably inconsequential, although I'll mention it anyway. Micronutrients in the FLEX-G and Hijau -- nice!

Before you test a batch of watering solution diluted with the FLEX-G, Hijau, and potassium sulfate, please be sure to clean the test jar thoroughly so you don't have any residues which could skew the results. You know the drill -- test the pH of your tap water and write down the number (step 1), add the ferts and potassium sulfate to your 50-liter bucket of water, then fill your test jar with some of the watering solution, test the pH and write down the number (step 2). This time you'll be testing rebound after 7 days, but not with the pH meter. What you'll do instead is test KH with a test strip (step 3). If it reads 0, KH neutralization from the dilute ferts is complete. If the number is higher than 0, you may need to add citric acid to your watering solution. If you do and how much can be determined only through the results of the rebound test with a KH test strip. When you give me the numbers from steps 1, 2, and 3, we can find out if adding citric acid to your watering solution is required at least for your alkaline mix.

By the way -- I don't think heat will affect the results of the rebound test, but direct sunlight very well could, so I recommend that you keep the test jar indoors.