Khalid: Fantastic thread. I love your pic. of banana peels. I already tested pH of banana peels using red-cabbage juice, it's neutral pH. The potassium is very high, I once soaked chopped banana peels in water, and watered roses with that .. the high potassium suppressed nitrogen and they didn't grow any new leaves. High potassium and calcium suppress nitrogen.
Guava is VERY HIGH in vitamin C, at 228 mg. It has 47 mg of phosphorus, and 417 mg of potassium, and all the B vitamins for plant growth. Both vitamin C and certain B vitamins help with plant growth.
http://wiki-fitness.com/guava-health-benefits-and-nutrition-facts/
pH of egg shell is neutral, it's composed mainly of calcium carbonate. I have egg shell in my compost for over a year, still hasn't decomposed. I would mix the egg-shell with acidic lemons, so the acid in lemons would release the calcium from the shell. I used lemons to lower my high pH tap water (near 9) down-to rain water at pH 5.6. The root growth was good with vitamin C, but roses' leaves broke down in black spots, due to lower pH.
Here's from Science Daily on how plants need vitamin C for growth:
" Scientists have proved for the first time that vitamin C is essential for plant growth. This discovery could have implications for agriculture and for the production of vitamin C dietary supplements. "
Another link shows that plants benefit from vitamin C, B vitamins, and vitamin E. They used to put sunflower seeds in the old ingredients of Rose-tone ... sunflower seeds is high in vitamin E.
http://homeguides.sfgate.com/kinds-vitamins-plants-need-49591.html
Calcium (lime or egg shell) is a good buffer to neutralize acidic rain, and acidic lemons. Fresh tea leaves are slightly acidic, but once decomposed, become slightly alkaline. U. of Illinois Extension did a study where they measured the pH of fully-composted leaves, and it's slightly alkaline. I didn't believe them, so I measured the pH of fully-composted grass using red-cabbage-juice, and it's slightly alkaline .. so they are right.
An excerpt from below link: "
Tea is not acidic enough to cause any harm.
Acidity is usually measured by pH, with pure water being given a pH of 7, and acids being given lower pH's, ranging from 1 (stomach acid) to 3-4 (fruit juices), to just under 6 for very mild acids. A recent study found the acidity of black tea to be about 4.9.[1]
http://ratetea.com/topic/acidity-of-tea/79/
Years ago when I did the thread on pH of organic values, the web reported pH of tea as slightly alkaline, 7.2. So I tested the pH of my used green leaf teas, and it was neutral pH in red-cabbage juice. I think black tea is more acidic than green tea. Some people say coffee grounds is acidic, while others say it's neutral. So I tested that in red cabbage juice: it was pinkish (acidic) at first, but after 1 hour soaking, it became neutral.
Coffee ground and tea-leaves are buffers, which mean they break down fast, to neutralize any acid released, and become neutral pH at the end. Also alkaline or neutral-pH scraps in compost encourage beneficial bacteria, while acidic scraps (lemon) encourage fungal growth.
For best plant's growth, or to encourage nitrogen-fixing bacteria, I would avoid lemons in compost heap. Bacteria prefer it alkaline, same with earthworms. Fungi or mold prefer neutral to acidic pH. At pH below 4, BOTH bacteria and fungi are suppressed. At neutral pH, there's a balance mix of bacteria and fungi. At alkaline pH, more bacteria and earthworms than fungi.
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