Hmm… I still owe you that article about tea taste that I promised so long ago. Great way to remind me.
Back to the issue of fertilizer and green tea taste:
I just did a tasting yesterday on a few lesser grade Huangshan Maofeng, trying to find a few possible ones for export demands. Some of them smell so exceedingly pleasing, fragrantly warm and flavourful, with that umami promise. While I was tasting them, all the usual disappointment on tasting lower grade green teas came by. Lack of depth and length; a thinner than expected body and much shorter tastes. Not that they are bad tea, I was just setting my expectation too high because of the smell.
A good tea needs to be both balanced as well as possessing length and depth; and with distinctive character. Any singular aspect without the support of others is not enough to give the drinker enough satisfaction. So is the umami aspect.
“Savouriness”, or “umami”, or in some translated Chinese text “soupiness” 
in some green teas is a result of the higher concentration of amino acids. I have to note here that this is not necessarily a measurement for all green teas, and definitely not for most oolongs or black tea. It is one for Longjing, as you are doing.
in some green teas is a result of the higher concentration of amino acids. I have to note here that this is not necessarily a measurement for all green teas, and definitely not for most oolongs or black tea. It is one for Longjing, as you are doing.As you have pointed out, concentration of amino acids in the leaves before plucking for green tea production is done by many ways, including adding of fertilizers. Most farmers are well aware of the fact that over fertilizing the soil is not going to do them any good. However, that point of just right is a difficult one. Many overdo it, as does this producer of mass market Huangshan Maofeng I tasted. I figure they would have lots of weed and pest problem every summer.
In the horticulture for high grade Longjing, fertilizers, chemical or organic, are used very sparingly and particularly not before Spring harvests. They want these highest priced leaves to grow very slowly so they can accrue ample concentration of all other things in the leaves for the kind of body that a seasoned drinker would expect from a good Longjing. Not just umami. They don’t want undergrowth and pest problems in the field either.
I am very impressed by your understanding of what to look for in a good Longjing for your relatively young tea age. Bravo.
Let me know if I have not answered your question.
