tea notes

These notes are maintained by Ben Discoe (who also has a tea farm)

< How to grow tea in Hawai‘i?

Tea: Soil and Fertilizer

• Most of the following is my understanding from Chapters 5 ("Tea soils") and 10 ("Mineral nutrition") of the Hajra book, along with information from UH CTAHR and Hawaiian USDA people.
• Acidity
  • In general, tea likes an acidic soil, which is generally what Hawai'i has - especially in Hamakua.
  • It is often reported that pH of 5.0 to 5.5 is good, although "vigorous growth of tea has been reported even at a pH of 3.2"!
  • If it's too far below 5.0, it's recommended to add some lime to bring pH up a bit.
• N / P / K
  • At Mealani, they've had lots of rapid growth by applying very large amounts of nitrogen fertilizer via fertigation.
  • It's been mentioned that you don't want to give tea too much Phosphorus, because it encourages the plant to flower, rather than grow leaves.
  • Generally, horse/cow/goat manure should be better than chicken manure, because chicken manure has a lower ratio of N/P.
• Compost
  • Hawaiian soils are generally lacking in many ways, including nutrients, humus and soil structure.  So, adding compost would seem to be a natural step.  However, reportedly with tea, "the USDA has experienced some problems with compost." 
  • What problems may occur, or at what phase of the plant's life compost could pose an issue?
  • CTAHR reports: "There may be an issue of newly planted tea plants not growing. It seems that once the plants are acclimated and vigor established, it's ok to add compost. The verdict is not completely out as of yet but we are offering caution at this time."
  • Dr. Zee of USDA reports: "During out initial dealing with rooted tea cuttings, we had difficulties when we added well composted macadamia husks into the soil as an amendment. We had much better results when the cuttings were planted directly into cane wash soil alone. Once the plants were established, compost can be good as a side dress, not touching the trunk. You probably have to do some testing at your site to see how suitable compost can be used as a soil amendment."
• Minerals
  • Besides pH and N/P/K, what minerals does tea need to grow well and be high quality?
  • The Hajra book says the limiting nutrients for high production are, in order: "N, P, K, Zn, Mg, Si, MO, B+liming"
  • Zinc (Zn): It's well known that a zinc deficiency commonly causes problems for tea.  The CTAHR publication PD-34 Oct. 2006: Zinc Deficiency in Tea (pdf) shows a picture of zinc deficiency and says you can add zinc either directly as a mineral amendment, and "Poultry and swine manure are good organic sources of zinc".  A lot of countries apply zinc as a foliar spray.
  • Magnesium (Mg): It's complex. Tea in some parts of the world got no benefit from adding Mg, some places did, and there's some interaction between Mg and K in the soil.  In places with very acidic soil, where dolomitic lime is added, that provides some Mg.
  • Sulfur (S): Tea needs it, but it shouldn't be a problem.  A small amount of manure, compost or other natural fertilizers seem to contain all the sulfur tea may need.
  • Calcium (Ca): Most phosphate fertilizers contain large amount of calcium, so conventional tea growers usually don't worry about calcium.  However, this may not be true for organic farming?  Many Hawaiian soils in wet areas are low in calcium due to millennia of leaching out from rainfall.
• Azomite seems to be a good source of many of the trace elements needed, including calcium.
  •  But, as of 2007-2008, it is usually out of stock on the Big Island ag supply stores.
• Kelp Meal is one likely alternative to Azomite, although it apparently usually costs 50% more.
• How about local (Big Island) sources of fertilizer?  See page on Hawai'i Agriculture Notes