g'day,
no absolute expert on citrus but as we manage to get good sweet fruits off of all of ours, i'm also going with growing conditions, could need some ph adjustment as well as a boost of nutrient around the drip line use any sort of manure, and heavily mulch with green type hay mulches even sugar cane mulch.
and like a lot of citrus they do like a cold spell over the fruit as it matures, those that get frost over them are the sweetest, but you can still get good fruit with more attention to nutrition.
they will also like a good deep watering at least once a month.
i would suggest a layer of manure from say 8"s out from the trunk to just beyond the drip line, then cover that with mushroom compost app'
4"s depth each, then at least 10"s of hay to extend beyond that line a little and keep renewing the hay as it breaks down.
ours also do well with watering from our grey water when needed, but i also save my wee water for ours as well and they get 1/2 bucket each twice a week of this wee fresh water mix (by that i mean i top up the bucket to full so at least 1/2 the bucket will be wee).
using the above method we grew great juicy citrus that got only available rainfall in a medium rainfall area when we were in rural.
if you have heavy clay add a good dose of gypsum under the above and i suppsoe without a ph test a handfull of dolomite won't do a lot of damage.
also find they do better on western aspects usually they have the extremes of micro climate.
snipped With peace and brightest of blessings,
len
-- "Be Content With What You Have And May You Find Serenity and Tranquillity In A World That You May Not Understand."
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